| blob | a628c038099a0d9bbdbdbcaf22f29c9ab386f6c6 |
13 </pre>
17 <pre>
20 ABSTRACT
24 (Cover sheet to be provided by ISO Secretariat.)
26 This International Standard specifies the form and establishes the interpretation of
27 programs expressed in the programming language C. Its purpose is to promote
28 portability, reliability, maintainability, and efficient execution of C language programs on
29 a variety of computing systems.
31 Clauses are included that detail the C language itself and the contents of the C language
32 execution library. Annexes summarize aspects of both of them, and enumerate factors
33 that influence the portability of C programs.
35 Although this International Standard is intended to guide knowledgeable C language
36 programmers as well as implementors of C language translation systems, the document
37 itself is not designed to serve as a tutorial.
39 Recipients of this draft are invited to submit, with their comments, notification of any
40 relevant patent rights of which they are aware and to provide supporting documentation.
42 Changes from the previous draft (N1539) are indicated by ''diff marks'' in the right
43 margin: deleted text is marked with ''*'', new or changed text with '' ''.
44 <!--page 2 -->
45 <!--page 3 -->
46 </pre>
50 <ul>
58 <ul>
60 <ul>
63 </ul>
65 <ul>
70 </ul>
71 </ul>
73 <ul>
76 <ul>
85 </ul>
87 <ul>
90 </ul>
92 <ul>
102 <!--page 4 -->
103 </ul>
105 <ul>
123 </ul>
126 <ul>
137 </ul>
139 <ul>
146 </ul>
148 <ul>
151 </ul>
153 <ul>
157 <!--page 5 -->
164 </ul>
166 <ul>
176 </ul>
177 </ul>
179 <ul>
181 <ul>
186 </ul>
188 <ul>
190 </ul>
192 <ul>
202 </ul>
204 <ul>
207 </ul>
210 <ul>
215 </ul>
217 <!--page 6 -->
219 <ul>
222 </ul>
226 <ul>
229 </ul>
231 <ul>
246 </ul>
248 <ul>
251 </ul>
253 <ul>
256 </ul>
259 <ul>
261 </ul>
263 <ul>
272 </ul>
276 <!--page 7 -->
277 <ul>
282 </ul>
284 <ul>
295 </ul>
297 <ul>
306 </ul>
309 <ul>
316 </ul>
319 <ul>
326 </ul>
328 <ul>
332 <!--page 8 -->
333 </ul>
335 <ul>
337 </ul>
339 <ul>
344 <ul>
351 </ul>
354 <ul>
359 </ul>
360 </ul>
361 <li><a href="#7.30"> 7.30 Wide character classification and mapping utilities <wctype.h></a>
362 <ul>
365 <ul>
368 </ul>
370 <ul>
373 </ul>
374 </ul>
376 <ul>
389 <!--page 9 -->
393 <li><a href="#7.31.16"> 7.31.16 Extended multibyte and wide character utilities <wchar.h></a>
394 <li><a href="#7.31.17"> 7.31.17 Wide character classification and mapping utilities <wctype.h></a>
395 </ul>
396 </ul>
398 <ul>
402 </ul>
404 <ul>
433 <li><a href="#B.29"> B.29 Wide character classification and mapping utilities <wctype.h></a>
434 </ul>
436 <!--page 10 -->
438 <ul>
441 </ul>
444 <ul>
455 <ul>
467 </ul>
468 </ul>
470 <ul>
475 <ul>
479 </ul>
481 <ul>
484 </ul>
486 <ul>
491 </ul>
493 <!--page 11 -->
494 </ul>
496 <ul>
500 </ul>
503 <ul>
509 </ul>
511 <ul>
515 <ul>
517 <ul>
522 </ul>
527 <ul>
532 </ul>
534 <ul>
540 </ul>
542 <ul>
547 </ul>
549 <ul>
552 <!--page 12 -->
553 </ul>
555 <ul>
559 </ul>
560 </ul>
561 </ul>
563 <ul>
567 </ul>
570 <!--page 13 -->
571 </ul>
576 ISO (the International Organization for Standardization) and IEC (the International
577 Electrotechnical Commission) form the specialized system for worldwide
578 standardization. National bodies that are member of ISO or IEC participate in the
579 development of International Standards through technical committees established by the
580 respective organization to deal with particular fields of technical activity. ISO and IEC
581 technical committees collaborate in fields of mutual interest. Other international
582 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
583 take part in the work.
585 International Standards are drafted in accordance with the rules given in the ISO/IEC
586 Directives, Part 2. This International Standard was drafted in accordance with the fifth
587 edition (2004).
589 In the field of information technology, ISO and IEC have established a joint technical
590 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
591 committee are circulated to national bodies for voting. Publication as an International
592 Standard requires approval by at least 75% of the national bodies casting a vote.
594 Attention is drawn to the possibility that some of the elements of this document may be
595 the subject of patent rights. ISO and IEC shall not be held responsible for identifying any
596 or all such patent rights.
598 This International Standard was prepared by Joint Technical Committee ISO/IEC JTC 1,
599 Information technology, Subcommittee SC 22, Programming languages, their
600 environments and system software interfaces. The Working Group responsible for this
601 standard (WG 14) maintains a site on the World Wide Web at http://www.open-
602 std.org/JTC1/SC22/WG14/ containing additional information relevant to this
603 standard such as a Rationale for many of the decisions made during its preparation and a
604 log of Defect Reports and Responses.
609 <ul>
610 <li> conditional (optional) features (including some that were previously mandatory)
611 <li> support for multiple threads of execution including an improved memory sequencing
615 <li> querying and specifying alignment of objects (<a href="#7.15"><stdalign.h></a>, <a href="#7.22"><stdlib.h></a>)
616 <li> Unicode characters and strings (<a href="#7.28"><uchar.h></a>) (originally specified in
618 <li> type-generic expressions
619 <!--page 14 -->
620 <li> static assertions
621 <li> anonymous structures and unions
622 <li> no-return functions
624 <li> support for opening files for exclusive access
626 <li> added the aligned_alloc, at_quick_exit, and quick_exit functions
628 <li> (conditional) support for bounds-checking interfaces (originally specified in
630 <li> (conditional) support for analyzability
631 </ul>
633 Major changes in the second edition included:
634 <ul>
635 <li> restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
636 in AMD1)
637 <li> wide character library support in <a href="#7.29"><wchar.h></a> and <a href="#7.30"><wctype.h></a> (originally
638 specified in AMD1)
639 <li> more precise aliasing rules via effective type
640 <li> restricted pointers
641 <li> variable length arrays
642 <li> flexible array members
643 <li> static and type qualifiers in parameter array declarators
646 <li> the long long int type and library functions
647 <li> increased minimum translation limits
649 <li> remove implicit int
650 <li> reliable integer division
651 <li> universal character names (\u and \U)
652 <li> extended identifiers
653 <li> hexadecimal floating-point constants and %a and %A printf/scanf conversion
654 specifiers
655 <!--page 15 -->
656 <li> compound literals
657 <li> designated initializers
658 <li> // comments
659 <li> extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.20"><stdint.h></a>
660 <li> remove implicit function declaration
661 <li> preprocessor arithmetic done in intmax_t/uintmax_t
662 <li> mixed declarations and code
663 <li> new block scopes for selection and iteration statements
664 <li> integer constant type rules
665 <li> integer promotion rules
666 <li> macros with a variable number of arguments
667 <li> the vscanf family of functions in <a href="#7.21"><stdio.h></a> and <a href="#7.29"><wchar.h></a>
669 <li> treatment of error conditions by math library functions (math_errhandling)
672 <li> trailing comma allowed in enum declaration
673 <li> %lf conversion specifier allowed in printf
674 <li> inline functions
677 <li> idempotent type qualifiers
678 <li> empty macro arguments
679 <li> new structure type compatibility rules (tag compatibility)
680 <li> additional predefined macro names
681 <li> _Pragma preprocessing operator
682 <li> standard pragmas
683 <li> __func__ predefined identifier
684 <li> va_copy macro
685 <li> additional strftime conversion specifiers
686 <li> LIA compatibility annex
687 <!--page 16 -->
688 <li> deprecate ungetc at the beginning of a binary file
689 <li> remove deprecation of aliased array parameters
690 <li> conversion of array to pointer not limited to lvalues
691 <li> relaxed constraints on aggregate and union initialization
692 <li> relaxed restrictions on portable header names
693 <li> return without expression not permitted in function that returns a value (and vice
694 versa)
695 </ul>
697 Annexes D, F, G, K, and L form a normative part of this standard; annexes A, B, C, E, H,
698 I, J, the bibliography, and the index are for information only. In accordance with Part 2 of
699 the ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples
700 are also for information only.
701 <!--page 17 -->
706 With the introduction of new devices and extended character sets, new features may be
707 added to this International Standard. Subclauses in the language and library clauses warn
708 implementors and programmers of usages which, though valid in themselves, may
709 conflict with future additions.
711 Certain features are obsolescent, which means that they may be considered for
712 withdrawal in future revisions of this International Standard. They are retained because
713 of their widespread use, but their use in new implementations (for implementation
714 features) or new programs (for language [<a href="#6.11">6.11</a>] or library features [<a href="#7.31">7.31</a>]) is discouraged.
716 This International Standard is divided into four major subdivisions:
717 <ul>
722 </ul>
724 Examples are provided to illustrate possible forms of the constructions described.
725 Footnotes are provided to emphasize consequences of the rules described in that
726 subclause or elsewhere in this International Standard. References are used to refer to
727 other related subclauses. Recommendations are provided to give advice or guidance to
728 implementors. Annexes provide additional information and summarize the information
729 contained in this International Standard. A bibliography lists documents that were
730 referred to during the preparation of the standard.
732 The language clause (clause 6) is derived from ''The C Reference Manual''.
735 <!--page 18 -->
736 <!--page 19 -->
747 This International Standard specifies the form and establishes the interpretation of
748 programs written in the C programming language.<sup><a href="#note1"><b>1)</b></a></sup> It specifies
749 <ul>
750 <li> the representation of C programs;
751 <li> the syntax and constraints of the C language;
752 <li> the semantic rules for interpreting C programs;
753 <li> the representation of input data to be processed by C programs;
754 <li> the representation of output data produced by C programs;
755 <li> the restrictions and limits imposed by a conforming implementation of C.
756 </ul>
758 This International Standard does not specify
759 <ul>
760 <li> the mechanism by which C programs are transformed for use by a data-processing
761 system;
762 <li> the mechanism by which C programs are invoked for use by a data-processing
763 system;
764 <li> the mechanism by which input data are transformed for use by a C program;
765 <li> the mechanism by which output data are transformed after being produced by a C
766 program;
767 <li> the size or complexity of a program and its data that will exceed the capacity of any
768 specific data-processing system or the capacity of a particular processor;
769 <li> all minimal requirements of a data-processing system that is capable of supporting a
770 conforming implementation.
773 <!--page 20 -->
774 </ul>
777 <p><small><a name="note1" href="#note1">1)</a> This International Standard is designed to promote the portability of C programs among a variety of
778 data-processing systems. It is intended for use by implementors and programmers.
779 </small>
784 The following referenced documents are indispensable for the application of this
785 document. For dated references, only the edition cited applies. For undated references,
786 the latest edition of the referenced document (including any amendments) applies.
789 use in the physical sciences and technology.
792 interchange.
795 terms.
797 ISO 4217, Codes for the representation of currencies and funds.
799 ISO 8601, Data elements and interchange formats -- Information interchange --
800 Representation of dates and times.
802 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
803 Character Set (UCS).
807 <!--page 21 -->
812 For the purposes of this International Standard, the following definitions apply. Other
813 terms are defined where they appear in italic type or on the left side of a syntax rule.
814 Terms explicitly defined in this International Standard are not to be presumed to refer
815 implicitly to similar terms defined elsewhere. Terms not defined in this International
825 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
828 NOTE 2 ''Modify'' includes the case where the new value being stored is the same as the previous value.
831 NOTE 3 Expressions that are not evaluated do not access objects.
838 requirement that objects of a particular type be located on storage boundaries with
839 addresses that are particular multiples of a byte address
845 actual argument
846 actual parameter (deprecated)
847 expression in the comma-separated list bounded by the parentheses in a function call
848 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
849 by the parentheses in a function-like macro invocation
855 external appearance or action
861 unspecified behavior where each implementation documents how the choice is made
863 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
864 when a signed integer is shifted right.
871 behavior that depends on local conventions of nationality, culture, and language that each
872 implementation documents
873 <!--page 22 -->
875 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
876 characters other than the 26 lowercase Latin letters.
883 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
884 for which this International Standard imposes no requirements
886 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
887 results, to behaving during translation or program execution in a documented manner characteristic of the
888 environment (with or without the issuance of a diagnostic message), to terminating a translation or
889 execution (with the issuance of a diagnostic message).
892 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
899 use of an unspecified value, or other behavior where this International Standard provides
900 two or more possibilities and imposes no further requirements on which is chosen in any
901 instance
903 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
904 evaluated.
911 unit of data storage in the execution environment large enough to hold an object that may
912 have one of two values
914 NOTE It need not be possible to express the address of each individual bit of an object.
921 addressable unit of data storage large enough to hold any member of the basic character
922 set of the execution environment
924 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
927 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
928 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
929 bit.
937 representation of data
943 single-byte character
945 <!--page 23 -->
951 sequence of one or more bytes representing a member of the extended character set of
952 either the source or the execution environment
954 NOTE The extended character set is a superset of the basic character set.
961 value representable by an object of type wchar_t, capable of representing any character
962 in the current locale
968 restriction, either syntactic or semantic, by which the exposition of language elements is
969 to be interpreted
975 representation in the result format that is nearest in value, subject to the current rounding
976 mode, to what the result would be given unlimited range and precision
982 message belonging to an implementation-defined subset of the implementation's message
983 output
989 reference to a later subclause of this International Standard that contains additional
990 information relevant to this subclause
996 particular set of software, running in a particular translation environment under particular
997 control options, that performs translation of programs for, and supports execution of
998 functions in, a particular execution environment
1004 restriction imposed upon programs by the implementation
1010 either an object of scalar type, or a maximal sequence of adjacent bit-fields all having
1011 nonzero width
1012 <!--page 24 -->
1014 NOTE 1 Two threads of execution can update and access separate memory locations without interfering
1015 with each other.
1018 NOTE 2 A bit-field and an adjacent non-bit-field member are in separate memory locations. The same
1019 applies to two bit-fields, if one is declared inside a nested structure declaration and the other is not, or if the
1020 two are separated by a zero-length bit-field declaration, or if they are separated by a non-bit-field member
1021 declaration. It is not safe to concurrently update two non-atomic bit-fields in the same structure if all
1022 members declared between them are also (non-zero-length) bit-fields, no matter what the sizes of those
1023 intervening bit-fields happen to be.
1026 EXAMPLE A structure declared as
1027 <pre>
1028 struct {
1029 char a;
1031 struct { int ee:8; } e;
1032 }
1033 </pre>
1034 contains four separate memory locations: The member a, and bit-fields d and e.ee are each separate
1035 memory locations, and can be modified concurrently without interfering with each other. The bit-fields b
1036 and c together constitute the fourth memory location. The bit-fields b and c cannot be concurrently
1037 modified, but b and a, for example, can be.
1044 region of data storage in the execution environment, the contents of which can represent
1045 values
1047 NOTE When referenced, an object may be interpreted as having a particular type; see <a href="#6.3.2.1">6.3.2.1</a>.
1054 formal parameter
1055 formal argument (deprecated)
1056 object declared as part of a function declaration or definition that acquires a value on
1057 entry to the function, or an identifier from the comma-separated list bounded by the
1058 parentheses immediately following the macro name in a function-like macro definition
1064 specification that is strongly recommended as being in keeping with the intent of the
1065 standard, but that may be impractical for some implementations
1071 requirement on a program when calling a library function
1073 NOTE 1 Despite the similar terms, a runtime-constraint is not a kind of constraint as defined by <a href="#3.8">3.8</a>, and
1074 need not be diagnosed at translation time.
1077 NOTE 2 Implementations that support the extensions in <a href="#K">annex K</a> are required to verify that the runtime-
1078 constraints for a library function are not violated by the program; see <a href="#K.3.1.4">K.3.1.4</a>.
1079 <!--page 25 -->
1085 precise meaning of the contents of an object when interpreted as having a specific type
1091 unspecified value where each implementation documents how the choice is made
1097 either an unspecified value or a trap representation
1103 valid value of the relevant type where this International Standard imposes no
1104 requirements on which value is chosen in any instance
1106 NOTE An unspecified value cannot be a trap representation.
1113 an object representation that need not represent a value of the object type
1119 interrupt execution of the program such that no further operations are performed
1121 NOTE In this International Standard, when the word ''trap'' is not immediately followed by
1126 <p><small><a name="note2" href="#note2">2)</a> For example, ''Trapping or stopping (if supported) is disabled...'' (<a href="#F.8.2">F.8.2</a>). Note that fetching a trap
1127 representation might perform a trap but is not required to (see <a href="#6.2.6.1">6.2.6.1</a>).
1128 </small>
1134 ceiling of x: the least integer greater than or equal to x
1143 floor of x: the greatest integer less than or equal to x
1150 <!--page 26 -->
1155 In this International Standard, ''shall'' is to be interpreted as a requirement on an
1156 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
1157 prohibition.
1159 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint or runtime-
1160 constraint is violated, the behavior is undefined. Undefined behavior is otherwise
1161 indicated in this International Standard by the words ''undefined behavior'' or by the
1162 omission of any explicit definition of behavior. There is no difference in emphasis among
1163 these three; they all describe ''behavior that is undefined''.
1165 A program that is correct in all other aspects, operating on correct data, containing
1166 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
1168 The implementation shall not successfully translate a preprocessing translation unit
1169 containing a #error preprocessing directive unless it is part of a group skipped by
1170 conditional inclusion.
1172 A strictly conforming program shall use only those features of the language and library
1173 specified in this International Standard.<sup><a href="#note3"><b>3)</b></a></sup> It shall not produce output dependent on any
1174 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
1175 minimum implementation limit.
1177 The two forms of conforming implementation are hosted and freestanding. A conforming
1178 hosted implementation shall accept any strictly conforming program. A conforming
1179 freestanding implementation shall accept any strictly conforming program in which the *
1180 use of the features specified in the library clause (clause 7) is confined to the contents of
1181 the standard headers <a href="#7.7"><float.h></a>, <a href="#7.9"><iso646.h></a>, <a href="#7.10"><limits.h></a>, <a href="#7.15"><stdalign.h></a>,
1182 <a href="#7.16"><stdarg.h></a>, <a href="#7.18"><stdbool.h></a>, <a href="#7.19"><stddef.h></a>, <a href="#7.20"><stdint.h></a>, and
1183 <a href="#7.23"><stdnoreturn.h></a>. A conforming implementation may have extensions (including
1184 additional library functions), provided they do not alter the behavior of any strictly
1189 <!--page 27 -->
1191 A conforming program is one that is acceptable to a conforming implementation.<sup><a href="#note5"><b>5)</b></a></sup>
1193 An implementation shall be accompanied by a document that defines all implementation-
1194 defined and locale-specific characteristics and all extensions.
1195 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), error directive (<a href="#6.10.5">6.10.5</a>),
1196 characteristics of floating types <a href="#7.7"><float.h></a> (<a href="#7.7">7.7</a>), alternative spellings <a href="#7.9"><iso646.h></a>
1197 (<a href="#7.9">7.9</a>), sizes of integer types <a href="#7.10"><limits.h></a> (<a href="#7.10">7.10</a>), alignment <a href="#7.15"><stdalign.h></a> (<a href="#7.15">7.15</a>),
1198 variable arguments <a href="#7.16"><stdarg.h></a> (<a href="#7.16">7.16</a>), boolean type and values <a href="#7.18"><stdbool.h></a>
1199 (<a href="#7.18">7.18</a>), common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>),
1205 <!--page 28 -->
1208 <p><small><a name="note3" href="#note3">3)</a> A strictly conforming program can use conditional features (see <a href="#6.10.8.3">6.10.8.3</a>) provided the use is guarded
1209 by an appropriate conditional inclusion preprocessing directive using the related macro. For example:
1211 <pre>
1212 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
1213 /* ... */
1214 fesetround(FE_UPWARD);
1215 /* ... */
1216 #endif
1217 </pre>
1219 </small>
1220 <p><small><a name="note4" href="#note4">4)</a> This implies that a conforming implementation reserves no identifiers other than those explicitly
1221 reserved in this International Standard.
1222 </small>
1223 <p><small><a name="note5" href="#note5">5)</a> Strictly conforming programs are intended to be maximally portable among conforming
1224 implementations. Conforming programs may depend upon nonportable features of a conforming
1225 implementation.
1226 </small>
1231 An implementation translates C source files and executes C programs in two data-
1232 processing-system environments, which will be called the translation environment and
1233 the execution environment in this International Standard. Their characteristics define and
1234 constrain the results of executing conforming C programs constructed according to the
1235 syntactic and semantic rules for conforming implementations.
1237 have been noted.
1248 A C program need not all be translated at the same time. The text of the program is kept
1249 in units called source files, (or preprocessing files) in this International Standard. A
1250 source file together with all the headers and source files included via the preprocessing
1251 directive #include is known as a preprocessing translation unit. After preprocessing, a
1252 preprocessing translation unit is called a translation unit. Previously translated translation
1253 units may be preserved individually or in libraries. The separate translation units of a
1254 program communicate by (for example) calls to functions whose identifiers have external
1255 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
1256 of data files. Translation units may be separately translated and then later linked to
1257 produce an executable program.
1258 <p><b> Forward references</b>: linkages of identifiers (<a href="#6.2.2">6.2.2</a>), external definitions (<a href="#6.9">6.9</a>),
1264 The precedence among the syntax rules of translation is specified by the following
1266 <ol>
1267 <li> Physical source file multibyte characters are mapped, in an implementation-
1268 defined manner, to the source character set (introducing new-line characters for
1269 end-of-line indicators) if necessary. Trigraph sequences are replaced by
1270 corresponding single-character internal representations.
1274 <!--page 29 -->
1275 <li> Each instance of a backslash character (\) immediately followed by a new-line
1276 character is deleted, splicing physical source lines to form logical source lines.
1277 Only the last backslash on any physical source line shall be eligible for being part
1278 of such a splice. A source file that is not empty shall end in a new-line character,
1279 which shall not be immediately preceded by a backslash character before any such
1280 splicing takes place.
1281 <li> The source file is decomposed into preprocessing tokens<sup><a href="#note7"><b>7)</b></a></sup> and sequences of
1282 white-space characters (including comments). A source file shall not end in a
1283 partial preprocessing token or in a partial comment. Each comment is replaced by
1284 one space character. New-line characters are retained. Whether each nonempty
1285 sequence of white-space characters other than new-line is retained or replaced by
1286 one space character is implementation-defined.
1287 <li> Preprocessing directives are executed, macro invocations are expanded, and
1288 _Pragma unary operator expressions are executed. If a character sequence that
1289 matches the syntax of a universal character name is produced by token
1290 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
1291 directive causes the named header or source file to be processed from phase 1
1292 through phase 4, recursively. All preprocessing directives are then deleted.
1293 <li> Each source character set member and escape sequence in character constants and
1294 string literals is converted to the corresponding member of the execution character
1295 set; if there is no corresponding member, it is converted to an implementation-
1297 <li> Adjacent string literal tokens are concatenated.
1298 <li> White-space characters separating tokens are no longer significant. Each
1299 preprocessing token is converted into a token. The resulting tokens are
1300 syntactically and semantically analyzed and translated as a translation unit.
1301 <li> All external object and function references are resolved. Library components are
1302 linked to satisfy external references to functions and objects not defined in the
1303 current translation. All such translator output is collected into a program image
1304 which contains information needed for execution in its execution environment.
1305 </ol>
1306 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), lexical elements (<a href="#6.4">6.4</a>),
1307 preprocessing directives (<a href="#6.10">6.10</a>), trigraph sequences (<a href="#5.2.1.1">5.2.1.1</a>), external definitions (<a href="#6.9">6.9</a>).
1311 <!--page 30 -->
1314 <p><small><a name="note6" href="#note6">6)</a> Implementations shall behave as if these separate phases occur, even though many are typically folded
1315 together in practice. Source files, translation units, and translated translation units need not
1316 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
1317 and any external representation. The description is conceptual only, and does not specify any
1318 particular implementation.
1319 </small>
1320 <p><small><a name="note7" href="#note7">7)</a> As described in <a href="#6.4">6.4</a>, the process of dividing a source file's characters into preprocessing tokens is
1321 context-dependent. For example, see the handling of < within a #include preprocessing directive.
1322 </small>
1323 <p><small><a name="note8" href="#note8">8)</a> An implementation need not convert all non-corresponding source characters to the same execution
1324 character.
1325 </small>
1330 A conforming implementation shall produce at least one diagnostic message (identified in
1331 an implementation-defined manner) if a preprocessing translation unit or translation unit
1332 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1333 specified as undefined or implementation-defined. Diagnostic messages need not be
1336 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1337 <pre>
1338 char i;
1339 int i;
1340 </pre>
1341 because in those cases where wording in this International Standard describes the behavior for a construct
1342 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1346 <p><small><a name="note9" href="#note9">9)</a> The intent is that an implementation should identify the nature of, and where possible localize, each
1347 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1348 valid program is still correctly translated. It may also successfully translate an invalid program.
1349 </small>
1354 Two execution environments are defined: freestanding and hosted. In both cases,
1355 program startup occurs when a designated C function is called by the execution
1356 environment. All objects with static storage duration shall be initialized (set to their
1357 initial values) before program startup. The manner and timing of such initialization are
1358 otherwise unspecified. Program termination returns control to the execution
1359 environment.
1360 <p><b> Forward references</b>: storage durations of objects (<a href="#6.2.4">6.2.4</a>), initialization (<a href="#6.7.9">6.7.9</a>).
1365 In a freestanding environment (in which C program execution may take place without any
1366 benefit of an operating system), the name and type of the function called at program
1367 startup are implementation-defined. Any library facilities available to a freestanding
1368 program, other than the minimal set required by clause 4, are implementation-defined.
1370 The effect of program termination in a freestanding environment is implementation-
1371 defined.
1376 A hosted environment need not be provided, but shall conform to the following
1377 specifications if present.
1382 <!--page 31 -->
1387 The function called at program startup is named main. The implementation declares no
1388 prototype for this function. It shall be defined with a return type of int and with no
1389 parameters:
1390 <pre>
1391 int main(void) { /* ... */ }
1392 </pre>
1393 or with two parameters (referred to here as argc and argv, though any names may be
1394 used, as they are local to the function in which they are declared):
1395 <pre>
1396 int main(int argc, char *argv[]) { /* ... */ }
1397 </pre>
1398 or equivalent;<sup><a href="#note10"><b>10)</b></a></sup> or in some other implementation-defined manner.
1400 If they are declared, the parameters to the main function shall obey the following
1401 constraints:
1402 <ul>
1403 <li> The value of argc shall be nonnegative.
1404 <li> argv[argc] shall be a null pointer.
1406 argv[argc-1] inclusive shall contain pointers to strings, which are given
1407 implementation-defined values by the host environment prior to program startup. The
1408 intent is to supply to the program information determined prior to program startup
1409 from elsewhere in the hosted environment. If the host environment is not capable of
1410 supplying strings with letters in both uppercase and lowercase, the implementation
1411 shall ensure that the strings are received in lowercase.
1414 program name is not available from the host environment. If the value of argc is
1416 represent the program parameters.
1417 <li> The parameters argc and argv and the strings pointed to by the argv array shall
1418 be modifiable by the program, and retain their last-stored values between program
1419 startup and program termination.
1420 </ul>
1423 <p><small><a name="note10" href="#note10">10)</a> Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as
1424 char ** argv, and so on.
1425 </small>
1430 In a hosted environment, a program may use all the functions, macros, type definitions,
1431 and objects described in the library clause (clause 7).
1436 <!--page 32 -->
1441 If the return type of the main function is a type compatible with int, a return from the
1442 initial call to the main function is equivalent to calling the exit function with the value
1443 returned by the main function as its argument;<sup><a href="#note11"><b>11)</b></a></sup> reaching the } that terminates the
1444 main function returns a value of 0. If the return type is not compatible with int, the
1445 termination status returned to the host environment is unspecified.
1446 <p><b> Forward references</b>: definition of terms (<a href="#7.1.1">7.1.1</a>), the exit function (<a href="#7.22.4.4">7.22.4.4</a>).
1449 <p><small><a name="note11" href="#note11">11)</a> In accordance with <a href="#6.2.4">6.2.4</a>, the lifetimes of objects with automatic storage duration declared in main
1450 will have ended in the former case, even where they would not have in the latter.
1451 </small>
1456 The semantic descriptions in this International Standard describe the behavior of an
1457 abstract machine in which issues of optimization are irrelevant.
1459 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1460 that does any of those operations are all side effects,<sup><a href="#note12"><b>12)</b></a></sup> which are changes in the state of
1461 the execution environment. Evaluation of an expression in general includes both value
1462 computations and initiation of side effects. Value computation for an lvalue expression
1463 includes determining the identity of the designated object.
1465 Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations
1466 executed by a single thread, which induces a partial order among those evaluations.
1467 Given any two evaluations A and B, if A is sequenced before B, then the execution of A
1468 shall precede the execution of B. (Conversely, if A is sequenced before B, then B is
1469 sequenced after A.) If A is not sequenced before or after B, then A and B are
1470 unsequenced. Evaluations A and B are indeterminately sequenced when A is sequenced
1471 either before or after B, but it is unspecified which.<sup><a href="#note13"><b>13)</b></a></sup> The presence of a sequence point
1472 between the evaluation of expressions A and B implies that every value computation and
1473 side effect associated with A is sequenced before every value computation and side effect
1476 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1477 actual implementation need not evaluate part of an expression if it can deduce that its
1478 value is not used and that no needed side effects are produced (including any caused by
1480 <!--page 33 -->
1481 calling a function or accessing a volatile object).
1483 When the processing of the abstract machine is interrupted by receipt of a signal, the
1484 values of objects that are neither lock-free atomic objects nor of type volatile
1485 sig_atomic_t are unspecified, as is the state of the floating-point environment. The
1486 value of any object modified by the handler that is neither a lock-free atomic object nor of
1487 type volatile sig_atomic_t becomes indeterminate when the handler exits, as
1488 does the state of the floating-point environment if it is modified by the handler and not
1489 restored to its original state.
1491 The least requirements on a conforming implementation are:
1492 <ul>
1493 <li> Accesses to volatile objects are evaluated strictly according to the rules of the abstract
1494 machine.
1495 <li> At program termination, all data written into files shall be identical to the result that
1496 execution of the program according to the abstract semantics would have produced.
1497 <li> The input and output dynamics of interactive devices shall take place as specified in
1498 <a href="#7.21.3">7.21.3</a>. The intent of these requirements is that unbuffered or line-buffered output
1499 appear as soon as possible, to ensure that prompting messages actually appear prior to
1500 a program waiting for input.
1501 </ul>
1502 This is the observable behavior of the program.
1504 What constitutes an interactive device is implementation-defined.
1506 More stringent correspondences between abstract and actual semantics may be defined by
1507 each implementation.
1509 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1510 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1511 abstract semantics. The keyword volatile would then be redundant.
1513 Alternatively, an implementation might perform various optimizations within each translation unit, such
1514 that the actual semantics would agree with the abstract semantics only when making function calls across
1515 translation unit boundaries. In such an implementation, at the time of each function entry and function
1516 return where the calling function and the called function are in different translation units, the values of all
1517 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1518 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1519 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1520 type of implementation, objects referred to by interrupt service routines activated by the signal function
1521 would require explicit specification of volatile storage, as well as other implementation-defined
1522 restrictions.
1525 EXAMPLE 2 In executing the fragment
1526 <pre>
1527 char c1, c2;
1528 /* ... */
1529 c1 = c1 + c2;
1530 </pre>
1531 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1532 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1533 <!--page 34 -->
1534 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1535 produce the same result, possibly omitting the promotions.
1538 EXAMPLE 3 Similarly, in the fragment
1539 <pre>
1540 float f1, f2;
1541 double d;
1542 /* ... */
1543 f1 = f2 * d;
1544 </pre>
1545 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1546 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1547 were replaced by the constant 2.0, which has type double).
1550 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1551 semantics. Values are independent of whether they are represented in a register or in memory. For
1552 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1553 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1554 perform their specified conversion. For the fragment
1555 <pre>
1556 double d1, d2;
1557 float f;
1558 d1 = f = expression;
1559 d2 = (float) expression;
1560 </pre>
1561 the values assigned to d1 and d2 are required to have been converted to float.
1564 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1565 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1566 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1567 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1568 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1570 <pre>
1571 double x, y, z;
1572 /* ... */
1573 x = (x * y) * z; // not equivalent to x *= y * z;
1574 z = (x - y) + y ; // not equivalent to z = x;
1575 z = x + x * y; // not equivalent to z = x * (1.0 + y);
1577 </pre>
1580 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1581 <pre>
1582 int a, b;
1583 /* ... */
1585 </pre>
1586 the expression statement behaves exactly the same as
1587 <pre>
1589 </pre>
1590 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1591 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1592 which overflows produce an explicit trap and in which the range of values representable by an int is
1594 <pre>
1595 a = ((a + b) + 32765);
1596 </pre>
1597 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1598 <!--page 35 -->
1599 while the original expression would not; nor can the expression be rewritten either as
1600 <pre>
1601 a = ((a + 32765) + b);
1602 </pre>
1603 or
1604 <pre>
1605 a = (a + (b + 32765));
1606 </pre>
1607 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1608 in which overflow silently generates some value and where positive and negative overflows cancel, the
1609 above expression statement can be rewritten by the implementation in any of the above ways because the
1610 same result will occur.
1613 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1614 following fragment
1615 <pre>
1617 int sum;
1618 char *p;
1619 /* ... */
1621 </pre>
1622 the expression statement is grouped as if it were written as
1623 <pre>
1625 </pre>
1626 but the actual increment of p can occur at any time between the previous sequence point and the next
1627 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1628 value.
1630 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), type qualifiers (<a href="#6.7.3">6.7.3</a>), statements (<a href="#6.8">6.8</a>), floating-
1631 point environment <a href="#7.6"><fenv.h></a> (<a href="#7.6">7.6</a>), the signal function (<a href="#7.14">7.14</a>), files (<a href="#7.21.3">7.21.3</a>).
1634 <p><small><a name="note12" href="#note12">12)</a> The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
1635 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1636 values of floating-point operations. Implementations that support such floating-point state are
1637 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1638 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1639 effects matter, freeing the implementations in other cases.
1640 </small>
1641 <p><small><a name="note13" href="#note13">13)</a> The executions of unsequenced evaluations can interleave. Indeterminately sequenced evaluations
1642 cannot interleave, but can be executed in any order.
1643 </small>
1646 <h5><a name="5.1.2.4" href="#5.1.2.4">5.1.2.4 Multi-threaded executions and data races</a></h5>
1648 Under a hosted implementation, a program can have more than one thread of execution
1649 (or thread) running concurrently. The execution of each thread proceeds as defined by
1650 the remainder of this standard. The execution of the entire program consists of an
1651 execution of all of its threads.<sup><a href="#note14"><b>14)</b></a></sup> Under a freestanding implementation, it is
1652 implementation-defined whether a program can have more than one thread of execution.
1654 The value of an object visible to a thread T at a particular point is the initial value of the
1655 object, a value stored in the object by T , or a value stored in the object by another thread,
1656 according to the rules below.
1658 NOTE 1 In some cases, there may instead be undefined behavior. Much of this section is motivated by
1659 the desire to support atomic operations with explicit and detailed visibility constraints. However, it also
1660 implicitly supports a simpler view for more restricted programs.
1663 Two expression evaluations conflict if one of them modifies a memory location and the
1664 other one reads or modifies the same memory location.
1667 <!--page 36 -->
1669 The library defines a number of atomic operations (<a href="#7.17">7.17</a>) and operations on mutexes
1670 (<a href="#7.26.4">7.26.4</a>) that are specially identified as synchronization operations. These operations play
1671 a special role in making assignments in one thread visible to another. A synchronization
1672 operation on one or more memory locations is either an acquire operation, a release
1673 operation, both an acquire and release operation, or a consume operation. A
1674 synchronization operation without an associated memory location is a fence and can be
1675 either an acquire fence, a release fence, or both an acquire and release fence. In addition,
1676 there are relaxed atomic operations, which are not synchronization operations, and
1677 atomic read-modify-write operations, which have special characteristics.
1679 NOTE 2 For example, a call that acquires a mutex will perform an acquire operation on the locations
1680 composing the mutex. Correspondingly, a call that releases the same mutex will perform a release
1681 operation on those same locations. Informally, performing a release operation on A forces prior side effects
1682 on other memory locations to become visible to other threads that later perform an acquire or consume
1683 operation on A. We do not include relaxed atomic operations as synchronization operations although, like
1684 synchronization operations, they cannot contribute to data races.
1687 All modifications to a particular atomic object M occur in some particular total order,
1688 called the modification order of M. If A and B are modifications of an atomic object M,
1689 and A happens before B, then A shall precede B in the modification order of M, which is
1690 defined below.
1692 NOTE 3 This states that the modification orders must respect the ''happens before'' relation.
1695 NOTE 4 There is a separate order for each atomic object. There is no requirement that these can be
1696 combined into a single total order for all objects. In general this will be impossible since different threads
1697 may observe modifications to different variables in inconsistent orders.
1700 A release sequence headed by a release operation A on an atomic object M is a maximal
1701 contiguous sub-sequence of side effects in the modification order of M, where the first
1702 operation is A and every subsequent operation either is performed by the same thread that
1703 performed the release or is an atomic read-modify-write operation.
1705 Certain library calls synchronize with other library calls performed by another thread. In
1706 particular, an atomic operation A that performs a release operation on an object M
1707 synchronizes with an atomic operation B that performs an acquire operation on M and
1708 reads a value written by any side effect in the release sequence headed by A.
1710 NOTE 5 Except in the specified cases, reading a later value does not necessarily ensure visibility as
1711 described below. Such a requirement would sometimes interfere with efficient implementation.
1714 NOTE 6 The specifications of the synchronization operations define when one reads the value written by
1715 another. For atomic variables, the definition is clear. All operations on a given mutex occur in a single total
1716 order. Each mutex acquisition ''reads the value written'' by the last mutex release.
1719 An evaluation A carries a dependency <sup><a href="#note15"><b>15)</b></a></sup> to an evaluation B if:
1722 <!--page 37 -->
1723 <ul>
1724 <li> the value of A is used as an operand of B, unless:
1725 <ul>
1726 <li> B is an invocation of the kill_dependency macro,
1730 <li> A is the left operand of a ? : operator, or
1732 <li> A is the left operand of a , operator;
1733 </ul>
1734 or
1735 <li> A writes a scalar object or bit-field M, B reads from M the value written by A, and A
1736 is sequenced before B, or
1737 <li> for some evaluation X, A carries a dependency to X and X carries a dependency to B.
1738 </ul>
1740 An evaluation A is dependency-ordered before<sup><a href="#note16"><b>16)</b></a></sup> an evaluation B if:
1741 <ul>
1742 <li> A performs a release operation on an atomic object M, and, in another thread, B
1743 performs a consume operation on M and reads a value written by any side effect in
1744 the release sequence headed by A, or
1745 <li> for some evaluation X, A is dependency-ordered before X and X carries a
1746 dependency to B.
1747 </ul>
1749 An evaluation A inter-thread happens before an evaluation B if A synchronizes with B, A
1750 is dependency-ordered before B, or, for some evaluation X:
1751 <ul>
1752 <li> A synchronizes with X and X is sequenced before B,
1753 <li> A is sequenced before X and X inter-thread happens before B, or
1754 <li> A inter-thread happens before X and X inter-thread happens before B.
1755 </ul>
1757 NOTE 7 The ''inter-thread happens before'' relation describes arbitrary concatenations of ''sequenced
1758 before'', ''synchronizes with'', and ''dependency-ordered before'' relationships, with two exceptions. The
1759 first exception is that a concatenation is not permitted to end with ''dependency-ordered before'' followed
1760 by ''sequenced before''. The reason for this limitation is that a consume operation participating in a
1761 ''dependency-ordered before'' relationship provides ordering only with respect to operations to which this
1762 consume operation actually carries a dependency. The reason that this limitation applies only to the end of
1763 such a concatenation is that any subsequent release operation will provide the required ordering for a prior
1764 consume operation. The second exception is that a concatenation is not permitted to consist entirely of
1765 ''sequenced before''. The reasons for this limitation are (1) to permit ''inter-thread happens before'' to be
1766 transitively closed and (2) the ''happens before'' relation, defined below, provides for relationships
1767 consisting entirely of ''sequenced before''.
1770 An evaluation A happens before an evaluation B if A is sequenced before B or A inter-
1771 thread happens before B.
1775 <!--page 38 -->
1777 A visible side effect A on an object M with respect to a value computation B of M
1778 satisfies the conditions:
1779 <ul>
1780 <li> A happens before B, and
1781 <li> there is no other side effect X to M such that A happens before X and X happens
1782 before B.
1783 </ul>
1784 The value of a non-atomic scalar object M, as determined by evaluation B, shall be the
1785 value stored by the visible side effect A.
1787 NOTE 8 If there is ambiguity about which side effect to a non-atomic object is visible, then there is a data
1788 race and the behavior is undefined.
1791 NOTE 9 This states that operations on ordinary variables are not visibly reordered. This is not actually
1792 detectable without data races, but it is necessary to ensure that data races, as defined here, and with suitable
1793 restrictions on the use of atomics, correspond to data races in a simple interleaved (sequentially consistent)
1794 execution.
1797 The visible sequence of side effects on an atomic object M, with respect to a value
1798 computation B of M, is a maximal contiguous sub-sequence of side effects in the
1799 modification order of M, where the first side effect is visible with respect to B, and for
1800 every subsequent side effect, it is not the case that B happens before it. The value of an
1801 atomic object M, as determined by evaluation B, shall be the value stored by some
1802 operation in the visible sequence of M with respect to B. Furthermore, if a value
1803 computation A of an atomic object M happens before a value computation B of M, and
1804 the value computed by A corresponds to the value stored by side effect X, then the value
1805 computed by B shall either equal the value computed by A, or be the value stored by side
1806 effect Y , where Y follows X in the modification order of M.
1808 NOTE 10 This effectively disallows compiler reordering of atomic operations to a single object, even if
1809 both operations are ''relaxed'' loads. By doing so, we effectively make the ''cache coherence'' guarantee
1810 provided by most hardware available to C atomic operations.
1813 NOTE 11 The visible sequence depends on the ''happens before'' relation, which in turn depends on the
1814 values observed by loads of atomics, which we are restricting here. The intended reading is that there must
1815 exist an association of atomic loads with modifications they observe that, together with suitably chosen
1816 modification orders and the ''happens before'' relation derived as described above, satisfy the resulting
1817 constraints as imposed here.
1820 The execution of a program contains a data race if it contains two conflicting actions in
1821 different threads, at least one of which is not atomic, and neither happens before the
1822 other. Any such data race results in undefined behavior.
1824 NOTE 12 It can be shown that programs that correctly use simple mutexes and
1825 memory_order_seq_cst operations to prevent all data races, and use no other synchronization
1826 operations, behave as though the operations executed by their constituent threads were simply interleaved,
1827 with each value computation of an object being the last value stored in that interleaving. This is normally
1828 referred to as ''sequential consistency''. However, this applies only to data-race-free programs, and data-
1829 race-free programs cannot observe most program transformations that do not change single-threaded
1830 program semantics. In fact, most single-threaded program transformations continue to be allowed, since
1831 any program that behaves differently as a result must contain undefined behavior.
1832 <!--page 39 -->
1834 NOTE 13 Compiler transformations that introduce assignments to a potentially shared memory location
1835 that would not be modified by the abstract machine are generally precluded by this standard, since such an
1836 assignment might overwrite another assignment by a different thread in cases in which an abstract machine
1837 execution would not have encountered a data race. This includes implementations of data member
1838 assignment that overwrite adjacent members in separate memory locations. We also generally preclude
1839 reordering of atomic loads in cases in which the atomics in question may alias, since this may violate the
1840 "visible sequence" rules.
1843 NOTE 14 Transformations that introduce a speculative read of a potentially shared memory location may
1844 not preserve the semantics of the program as defined in this standard, since they potentially introduce a data
1845 race. However, they are typically valid in the context of an optimizing compiler that targets a specific
1846 machine with well-defined semantics for data races. They would be invalid for a hypothetical machine that
1847 is not tolerant of races or provides hardware race detection.
1848 <!--page 40 -->
1851 <p><small><a name="note14" href="#note14">14)</a> The execution can usually be viewed as an interleaving of all of the threads. However, some kinds of
1852 atomic operations, for example, allow executions inconsistent with a simple interleaving as described
1853 below.
1854 </small>
1855 <p><small><a name="note15" href="#note15">15)</a> The ''carries a dependency'' relation is a subset of the ''sequenced before'' relation, and is similarly
1856 strictly intra-thread.
1857 </small>
1858 <p><small><a name="note16" href="#note16">16)</a> The ''dependency-ordered before'' relation is analogous to the ''synchronizes with'' relation, but uses
1859 release/consume in place of release/acquire.
1860 </small>
1868 Two sets of characters and their associated collating sequences shall be defined: the set in
1869 which source files are written (the source character set), and the set interpreted in the
1870 execution environment (the execution character set). Each set is further divided into a
1871 basic character set, whose contents are given by this subclause, and a set of zero or more
1872 locale-specific members (which are not members of the basic character set) called
1873 extended characters. The combined set is also called the extended character set. The
1874 values of the members of the execution character set are implementation-defined.
1876 In a character constant or string literal, members of the execution character set shall be
1877 represented by corresponding members of the source character set or by escape
1878 sequences consisting of the backslash \ followed by one or more characters. A byte with
1879 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1880 is used to terminate a character string.
1882 Both the basic source and basic execution character sets shall have the following
1883 members: the 26 uppercase letters of the Latin alphabet
1884 <pre>
1885 A B C D E F G H I J K L M
1886 N O P Q R S T U V W X Y Z
1887 </pre>
1888 the 26 lowercase letters of the Latin alphabet
1889 <pre>
1890 a b c d e f g h i j k l m
1891 n o p q r s t u v w x y z
1892 </pre>
1893 the 10 decimal digits
1894 <pre>
1895 0 1 2 3 4 5 6 7 8 9
1896 </pre>
1897 the following 29 graphic characters
1898 <pre>
1899 ! " # % & ' ( ) * + , - . / :
1900 ; < = > ? [ \ ] ^ _ { | } ~
1901 </pre>
1902 the space character, and control characters representing horizontal tab, vertical tab, and
1903 form feed. The representation of each member of the source and execution basic
1904 character sets shall fit in a byte. In both the source and execution basic character sets, the
1905 value of each character after 0 in the above list of decimal digits shall be one greater than
1906 the value of the previous. In source files, there shall be some way of indicating the end of
1907 each line of text; this International Standard treats such an end-of-line indicator as if it
1908 were a single new-line character. In the basic execution character set, there shall be
1909 control characters representing alert, backspace, carriage return, and new line. If any
1910 other characters are encountered in a source file (except in an identifier, a character
1911 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1912 <!--page 41 -->
1913 converted to a token), the behavior is undefined.
1914 <p><!--para 4 -->
1915 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1916 Standard the term does not include other characters that are letters in other alphabets.
1917 <p><!--para 5 -->
1918 The universal character name construct provides a way to name other characters.
1919 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), character constants (<a href="#6.4.4.4">6.4.4.4</a>),
1920 preprocessing directives (<a href="#6.10">6.10</a>), string literals (<a href="#6.4.5">6.4.5</a>), comments (<a href="#6.4.9">6.4.9</a>), string (<a href="#7.1.1">7.1.1</a>).
1924 <p><!--para 1 -->
1925 Before any other processing takes place, each occurrence of one of the following
1926 sequences of three characters (called trigraph sequences<sup><a href="#note17"><b>17)</b></a></sup>) is replaced with the
1927 corresponding single character.
1928 <pre>
1929 ??= # ??) ] ??! |
1930 ??( [ ??' ^ ??> }
1931 ??/ \ ??< { ??- ~
1932 </pre>
1933 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1934 above is not changed.
1935 <p><!--para 2 -->
1936 EXAMPLE 1
1937 <pre>
1938 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
1939 </pre>
1940 becomes
1941 <pre>
1942 #define arraycheck(a, b) a[b] || b[a]
1943 </pre>
1945 <p><!--para 3 -->
1946 EXAMPLE 2 The following source line
1947 <pre>
1949 </pre>
1950 becomes (after replacement of the trigraph sequence ??/)
1951 <pre>
1953 </pre>
1956 <p><b>Footnotes</b>
1957 <p><small><a name="note17" href="#note17">17)</a> The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
1958 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1959 </small>
1963 <p><!--para 1 -->
1964 The source character set may contain multibyte characters, used to represent members of
1965 the extended character set. The execution character set may also contain multibyte
1966 characters, which need not have the same encoding as for the source character set. For
1967 both character sets, the following shall hold:
1968 <ul>
1969 <li> The basic character set shall be present and each character shall be encoded as a
1970 single byte.
1971 <li> The presence, meaning, and representation of any additional members is locale-
1972 specific.
1974 <!--page 42 -->
1975 <li> A multibyte character set may have a state-dependent encoding, wherein each
1976 sequence of multibyte characters begins in an initial shift state and enters other
1977 locale-specific shift states when specific multibyte characters are encountered in the
1978 sequence. While in the initial shift state, all single-byte characters retain their usual
1979 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1980 in the sequence is a function of the current shift state.
1981 <li> A byte with all bits zero shall be interpreted as a null character independent of shift
1982 state. Such a byte shall not occur as part of any other multibyte character.
1983 </ul>
1984 <p><!--para 2 -->
1985 For source files, the following shall hold:
1986 <ul>
1987 <li> An identifier, comment, string literal, character constant, or header name shall begin
1988 and end in the initial shift state.
1989 <li> An identifier, comment, string literal, character constant, or header name shall consist
1990 of a sequence of valid multibyte characters.
1991 </ul>
1995 <p><!--para 1 -->
1996 The active position is that location on a display device where the next character output by
1997 the fputc function would appear. The intent of writing a printing character (as defined
1998 by the isprint function) to a display device is to display a graphic representation of
1999 that character at the active position and then advance the active position to the next
2000 position on the current line. The direction of writing is locale-specific. If the active
2001 position is at the final position of a line (if there is one), the behavior of the display device
2002 is unspecified.
2003 <p><!--para 2 -->
2004 Alphabetic escape sequences representing nongraphic characters in the execution
2005 character set are intended to produce actions on display devices as follows:
2006 \a (alert) Produces an audible or visible alert without changing the active position.
2007 \b (backspace) Moves the active position to the previous position on the current line. If
2008 <pre>
2009 the active position is at the initial position of a line, the behavior of the display
2010 device is unspecified.
2011 </pre>
2012 \f ( form feed) Moves the active position to the initial position at the start of the next
2013 <pre>
2014 logical page.
2015 </pre>
2016 \n (new line) Moves the active position to the initial position of the next line.
2017 \r (carriage return) Moves the active position to the initial position of the current line.
2018 \t (horizontal tab) Moves the active position to the next horizontal tabulation position
2019 <pre>
2020 on the current line. If the active position is at or past the last defined horizontal
2021 tabulation position, the behavior of the display device is unspecified.
2022 </pre>
2023 \v (vertical tab) Moves the active position to the initial position of the next vertical
2024 <!--page 43 -->
2025 <pre>
2026 tabulation position. If the active position is at or past the last defined vertical
2027 tabulation position, the behavior of the display device is unspecified.
2028 </pre>
2029 <p><!--para 3 -->
2030 Each of these escape sequences shall produce a unique implementation-defined value
2031 which can be stored in a single char object. The external representations in a text file
2032 need not be identical to the internal representations, and are outside the scope of this
2033 International Standard.
2034 <p><b> Forward references</b>: the isprint function (<a href="#7.4.1.8">7.4.1.8</a>), the fputc function (<a href="#7.21.7.3">7.21.7.3</a>).
2038 <p><!--para 1 -->
2039 Functions shall be implemented such that they may be interrupted at any time by a signal,
2040 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
2041 invocations' control flow (after the interruption), function return values, or objects with
2042 automatic storage duration. All such objects shall be maintained outside the function
2043 image (the instructions that compose the executable representation of a function) on a
2044 per-invocation basis.
2048 <p><!--para 1 -->
2049 Both the translation and execution environments constrain the implementation of
2050 language translators and libraries. The following summarizes the language-related
2051 environmental limits on a conforming implementation; the library-related limits are
2052 discussed in clause 7.
2056 <p><!--para 1 -->
2057 The implementation shall be able to translate and execute at least one program that
2058 contains at least one instance of every one of the following limits:<sup><a href="#note18"><b>18)</b></a></sup>
2059 <ul>
2060 <li> 127 nesting levels of blocks
2061 <li> 63 nesting levels of conditional inclusion
2062 <li> 12 pointer, array, and function declarators (in any combinations) modifying an
2063 arithmetic, structure, union, or void type in a declaration
2064 <li> 63 nesting levels of parenthesized declarators within a full declarator
2065 <li> 63 nesting levels of parenthesized expressions within a full expression
2066 <li> 63 significant initial characters in an internal identifier or a macro name (each
2067 universal character name or extended source character is considered a single
2068 character)
2069 <li> 31 significant initial characters in an external identifier (each universal character name
2070 specifying a short identifier of 0000FFFF or less is considered 6 characters, each
2073 <!--page 44 -->
2074 <pre>
2075 universal character name specifying a short identifier of 00010000 or more is
2076 considered 10 characters, and each extended source character is considered the same
2077 number of characters as the corresponding universal character name, if any)<sup><a href="#note19"><b>19)</b></a></sup>
2078 </pre>
2079 <li> 4095 external identifiers in one translation unit
2080 <li> 511 identifiers with block scope declared in one block
2081 <li> 4095 macro identifiers simultaneously defined in one preprocessing translation unit
2082 <li> 127 parameters in one function definition
2083 <li> 127 arguments in one function call
2084 <li> 127 parameters in one macro definition
2085 <li> 127 arguments in one macro invocation
2086 <li> 4095 characters in a logical source line
2087 <li> 4095 characters in a string literal (after concatenation)
2088 <li> 65535 bytes in an object (in a hosted environment only)
2089 <li> 15 nesting levels for #included files
2090 <li> 1023 case labels for a switch statement (excluding those for any nested switch
2091 statements)
2092 <li> 1023 members in a single structure or union
2093 <li> 1023 enumeration constants in a single enumeration
2094 <li> 63 levels of nested structure or union definitions in a single struct-declaration-list
2095 </ul>
2097 <p><b>Footnotes</b>
2098 <p><small><a name="note18" href="#note18">18)</a> Implementations should avoid imposing fixed translation limits whenever possible.
2099 </small>
2100 <p><small><a name="note19" href="#note19">19)</a> See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
2101 </small>
2105 <p><!--para 1 -->
2106 An implementation is required to document all the limits specified in this subclause,
2107 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
2109 <p><b> Forward references</b>: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>).
2112 <h5><a name="5.2.4.2.1" href="#5.2.4.2.1">5.2.4.2.1 Sizes of integer types <limits.h></a></h5>
2113 <p><!--para 1 -->
2114 The values given below shall be replaced by constant expressions suitable for use in #if
2115 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
2116 following shall be replaced by expressions that have the same type as would an
2117 expression that is an object of the corresponding type converted according to the integer
2118 promotions. Their implementation-defined values shall be equal or greater in magnitude
2121 <!--page 45 -->
2122 (absolute value) to those shown, with the same sign.
2123 <ul>
2124 <li> number of bits for smallest object that is not a bit-field (byte)
2125 CHAR_BIT 8
2126 <li> minimum value for an object of type signed char
2127 SCHAR_MIN -127 // -(27 - 1)
2128 <li> maximum value for an object of type signed char
2129 SCHAR_MAX +127 // 27 - 1
2130 <li> maximum value for an object of type unsigned char
2131 UCHAR_MAX 255 // 28 - 1
2132 <li> minimum value for an object of type char
2133 CHAR_MIN see below
2134 <li> maximum value for an object of type char
2135 CHAR_MAX see below
2136 <li> maximum number of bytes in a multibyte character, for any supported locale
2137 MB_LEN_MAX 1
2138 <li> minimum value for an object of type short int
2139 SHRT_MIN -32767 // -(215 - 1)
2140 <li> maximum value for an object of type short int
2141 SHRT_MAX +32767 // 215 - 1
2142 <li> maximum value for an object of type unsigned short int
2143 USHRT_MAX 65535 // 216 - 1
2144 <li> minimum value for an object of type int
2145 INT_MIN -32767 // -(215 - 1)
2146 <li> maximum value for an object of type int
2147 INT_MAX +32767 // 215 - 1
2148 <li> maximum value for an object of type unsigned int
2149 UINT_MAX 65535 // 216 - 1
2150 <li> minimum value for an object of type long int
2151 LONG_MIN -2147483647 // -(231 - 1)
2152 <li> maximum value for an object of type long int
2153 LONG_MAX +2147483647 // 231 - 1
2154 <li> maximum value for an object of type unsigned long int
2155 ULONG_MAX 4294967295 // 232 - 1
2156 <!--page 46 -->
2157 <li> minimum value for an object of type long long int
2158 LLONG_MIN -9223372036854775807 // -(263 - 1)
2159 <li> maximum value for an object of type long long int
2160 LLONG_MAX +9223372036854775807 // 263 - 1
2161 <li> maximum value for an object of type unsigned long long int
2162 ULLONG_MAX 18446744073709551615 // 264 - 1
2163 </ul>
2164 <p><!--para 2 -->
2165 If the value of an object of type char is treated as a signed integer when used in an
2166 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
2167 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
2168 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
2169 UCHAR_MAX.<sup><a href="#note20"><b>20)</b></a></sup> The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
2170 <p><b> Forward references</b>: representations of types (<a href="#6.2.6">6.2.6</a>), conditional inclusion (<a href="#6.10.1">6.10.1</a>).
2172 <p><b>Footnotes</b>
2174 </small>
2177 <h5><a name="5.2.4.2.2" href="#5.2.4.2.2">5.2.4.2.2 Characteristics of floating types <float.h></a></h5>
2178 <p><!--para 1 -->
2179 The characteristics of floating types are defined in terms of a model that describes a
2180 representation of floating-point numbers and values that provide information about an
2181 implementation's floating-point arithmetic.<sup><a href="#note21"><b>21)</b></a></sup> The following parameters are used to
2182 define the model for each floating-point type:
2183 <pre>
2184 s sign ((+-)1)
2185 b base or radix of exponent representation (an integer > 1)
2186 e exponent (an integer between a minimum emin and a maximum emax )
2187 p precision (the number of base-b digits in the significand)
2188 fk nonnegative integers less than b (the significand digits)
2189 </pre>
2190 <p><!--para 2 -->
2191 A floating-point number (x) is defined by the following model:
2192 <pre>
2193 p
2194 x = sb e (Sum) f k b-k ,
2195 k=1
2196 emin <= e <= emax
2197 </pre>
2199 <p><!--para 3 -->
2200 In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be
2201 able to contain other kinds of floating-point numbers, such as subnormal floating-point
2202 numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0,
2203 e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and
2204 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
2205 through almost every arithmetic operation without raising a floating-point exception; a
2206 signaling NaN generally raises a floating-point exception when occurring as an
2209 <!--page 47 -->
2211 <p><!--para 4 -->
2212 An implementation may give zero and values that are not floating-point numbers (such as
2213 infinities and NaNs) a sign or may leave them unsigned. Wherever such values are
2214 unsigned, any requirement in this International Standard to retrieve the sign shall produce
2215 an unspecified sign, and any requirement to set the sign shall be ignored.
2216 <p><!--para 5 -->
2217 The minimum range of representable values for a floating type is the most negative finite
2218 floating-point number representable in that type through the most positive finite floating-
2219 point number representable in that type. In addition, if negative infinity is representable
2220 in a type, the range of that type is extended to all negative real numbers; likewise, if
2221 positive infinity is representable in a type, the range of that type is extended to all positive
2222 real numbers.
2223 <p><!--para 6 -->
2224 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
2225 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
2226 defined, as is the accuracy of the conversion between floating-point internal
2227 representations and string representations performed by the library functions in
2228 <a href="#7.21"><stdio.h></a>, <a href="#7.22"><stdlib.h></a>, and <a href="#7.29"><wchar.h></a>. The implementation may state that the
2229 accuracy is unknown.
2230 <p><!--para 7 -->
2231 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
2232 expressions suitable for use in #if preprocessing directives; all floating values shall be
2233 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
2234 and FLT_ROUNDS have separate names for all three floating-point types. The floating-
2235 point model representation is provided for all values except FLT_EVAL_METHOD and
2236 FLT_ROUNDS.
2237 <p><!--para 8 -->
2238 The rounding mode for floating-point addition is characterized by the implementation-
2240 <pre>
2241 -1 indeterminable
2242 0 toward zero
2243 1 to nearest
2244 2 toward positive infinity
2245 3 toward negative infinity
2246 </pre>
2247 All other values for FLT_ROUNDS characterize implementation-defined rounding
2248 behavior.
2251 <!--page 48 -->
2252 <p><!--para 9 -->
2253 Except for assignment and cast (which remove all extra range and precision), the values
2254 yielded by operators with floating operands and values subject to the usual arithmetic
2255 conversions and of floating constants are evaluated to a format whose range and precision
2256 may be greater than required by the type. The use of evaluation formats is characterized
2257 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note24"><b>24)</b></a></sup>
2258 <pre>
2259 -1 indeterminable;
2260 0 evaluate all operations and constants just to the range and precision of the
2261 type;
2262 1 evaluate operations and constants of type float and double to the
2263 range and precision of the double type, evaluate long double
2264 operations and constants to the range and precision of the long double
2265 type;
2266 2 evaluate all operations and constants to the range and precision of the
2267 long double type.
2268 </pre>
2269 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
2270 behavior.
2271 <p><!--para 10 -->
2272 The presence or absence of subnormal numbers is characterized by the implementation-
2273 defined values of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and
2274 LDBL_HAS_SUBNORM:
2275 <pre>
2278 1 present (type does support subnormal numbers)
2279 </pre>
2280 <p><!--para 11 -->
2281 The values given in the following list shall be replaced by constant expressions with
2282 implementation-defined values that are greater or equal in magnitude (absolute value) to
2283 those shown, with the same sign:
2284 <ul>
2285 <li> radix of exponent representation, b
2286 FLT_RADIX 2
2291 <!--page 49 -->
2292 <li> number of base-FLT_RADIX digits in the floating-point significand, p
2293 FLT_MANT_DIG
2294 DBL_MANT_DIG
2295 LDBL_MANT_DIG
2296 <li> number of decimal digits, n, such that any floating-point number with p radix b digits
2297 can be rounded to a floating-point number with n decimal digits and back again
2298 without change to the value,
2299 <pre>
2300 { p log10 b if b is a power of 10
2301 {
2302 { [^1 + p log10 b^] otherwise
2303 </pre>
2304 FLT_DECIMAL_DIG 6
2305 DBL_DECIMAL_DIG 10
2306 LDBL_DECIMAL_DIG 10
2307 <li> number of decimal digits, n, such that any floating-point number in the widest
2308 supported floating type with pmax radix b digits can be rounded to a floating-point
2309 number with n decimal digits and back again without change to the value,
2310 <pre>
2311 { pmax log10 b if b is a power of 10
2312 {
2313 { [^1 + pmax log10 b^] otherwise
2314 </pre>
2315 DECIMAL_DIG 10
2316 <li> number of decimal digits, q, such that any floating-point number with q decimal digits
2317 can be rounded into a floating-point number with p radix b digits and back again
2318 without change to the q decimal digits,
2319 <pre>
2320 { p log10 b if b is a power of 10
2321 {
2322 { [_( p - 1) log10 b_] otherwise
2323 </pre>
2324 FLT_DIG 6
2325 DBL_DIG 10
2326 LDBL_DIG 10
2327 <li> minimum negative integer such that FLT_RADIX raised to one less than that power is
2328 a normalized floating-point number, emin
2329 FLT_MIN_EXP
2330 DBL_MIN_EXP
2331 LDBL_MIN_EXP
2332 <!--page 50 -->
2333 <li> minimum negative integer such that 10 raised to that power is in the range of
2334 normalized floating-point numbers, [^log10 b emin -1 ^]
2335 <pre>
2336 [ ]
2337 </pre>
2338 FLT_MIN_10_EXP -37
2339 DBL_MIN_10_EXP -37
2340 LDBL_MIN_10_EXP -37
2341 <li> maximum integer such that FLT_RADIX raised to one less than that power is a
2342 representable finite floating-point number, emax
2343 <pre>
2344 FLT_MAX_EXP
2345 DBL_MAX_EXP
2346 LDBL_MAX_EXP
2347 </pre>
2348 <li> maximum integer such that 10 raised to that power is in the range of representable
2349 finite floating-point numbers, [_log10 ((1 - b- p )b emax )_]
2350 <pre>
2351 FLT_MAX_10_EXP +37
2352 DBL_MAX_10_EXP +37
2353 LDBL_MAX_10_EXP +37
2354 </pre>
2355 </ul>
2356 <p><!--para 12 -->
2357 The values given in the following list shall be replaced by constant expressions with
2358 implementation-defined values that are greater than or equal to those shown:
2359 <ul>
2360 <li> maximum representable finite floating-point number, (1 - b- p )b emax
2361 <pre>
2362 FLT_MAX 1E+37
2363 DBL_MAX 1E+37
2364 LDBL_MAX 1E+37
2365 </pre>
2366 </ul>
2367 <p><!--para 13 -->
2368 The values given in the following list shall be replaced by constant expressions with
2369 implementation-defined (positive) values that are less than or equal to those shown:
2370 <ul>
2371 <li> the difference between 1 and the least value greater than 1 that is representable in the
2372 given floating point type, b1- p
2373 <pre>
2374 FLT_EPSILON 1E-5
2375 DBL_EPSILON 1E-9
2376 LDBL_EPSILON 1E-9
2377 </pre>
2378 <li> minimum normalized positive floating-point number, b emin -1
2379 <!--page 51 -->
2380 <pre>
2381 FLT_MIN 1E-37
2382 DBL_MIN 1E-37
2383 LDBL_MIN 1E-37
2384 </pre>
2386 FLT_TRUE_MIN 1E-37
2387 DBL_TRUE_MIN 1E-37
2388 LDBL_TRUE_MIN 1E-37
2389 </ul>
2390 <p><b>Recommended practice</b>
2391 <p><!--para 14 -->
2392 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
2393 should be the identity function.
2394 <p><!--para 15 -->
2395 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
2396 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
2397 float:
2398 <pre>
2399 6
2400 x = s16e (Sum) f k 16-k ,
2401 k=1
2402 -31 <= e <= +32
2403 </pre>
2405 <pre>
2406 FLT_RADIX 16
2407 FLT_MANT_DIG 6
2408 FLT_EPSILON 9.53674316E-07F
2409 FLT_DECIMAL_DIG 9
2410 FLT_DIG 6
2411 FLT_MIN_EXP -31
2412 FLT_MIN 2.93873588E-39F
2413 FLT_MIN_10_EXP -38
2414 FLT_MAX_EXP +32
2415 FLT_MAX 3.40282347E+38F
2416 FLT_MAX_10_EXP +38
2417 </pre>
2419 <p><!--para 16 -->
2420 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
2421 single-precision and double-precision numbers in IEC 60559,<sup><a href="#note28"><b>28)</b></a></sup> and the appropriate values in a
2423 <pre>
2424 24
2425 x f = s2e (Sum) f k 2-k ,
2426 k=1
2427 -125 <= e <= +128
2428 </pre>
2430 <pre>
2431 53
2432 x d = s2e (Sum) f k 2-k ,
2433 k=1
2434 -1021 <= e <= +1024
2435 </pre>
2437 <pre>
2438 FLT_RADIX 2
2439 DECIMAL_DIG 17
2440 FLT_MANT_DIG 24
2441 FLT_EPSILON 1.19209290E-07F // decimal constant
2442 FLT_EPSILON 0X1P-23F // hex constant
2443 FLT_DECIMAL_DIG 9
2444 </pre>
2447 <!--page 52 -->
2448 <pre>
2449 FLT_DIG 6
2450 FLT_MIN_EXP -125
2451 FLT_MIN 1.17549435E-38F // decimal constant
2452 FLT_MIN 0X1P-126F // hex constant
2453 FLT_TRUE_MIN 1.40129846E-45F // decimal constant
2454 FLT_TRUE_MIN 0X1P-149F // hex constant
2455 FLT_HAS_SUBNORM 1
2456 FLT_MIN_10_EXP -37
2457 FLT_MAX_EXP +128
2458 FLT_MAX 3.40282347E+38F // decimal constant
2459 FLT_MAX 0X1.fffffeP127F // hex constant
2460 FLT_MAX_10_EXP +38
2461 DBL_MANT_DIG 53
2462 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
2463 DBL_EPSILON 0X1P-52 // hex constant
2464 DBL_DECIMAL_DIG 17
2465 DBL_DIG 15
2466 DBL_MIN_EXP -1021
2467 DBL_MIN 2.2250738585072014E-308 // decimal constant
2468 DBL_MIN 0X1P-1022 // hex constant
2469 DBL_TRUE_MIN 4.9406564584124654E-324 // decimal constant
2470 DBL_TRUE_MIN 0X1P-1074 // hex constant
2471 DBL_HAS_SUBNORM 1
2472 DBL_MIN_10_EXP -307
2473 DBL_MAX_EXP +1024
2474 DBL_MAX 1.7976931348623157E+308 // decimal constant
2475 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
2476 DBL_MAX_10_EXP +308
2477 </pre>
2478 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
2479 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
2480 precision), then DECIMAL_DIG would be 21.
2482 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
2483 <a href="#7.3"><complex.h></a> (<a href="#7.3">7.3</a>), extended multibyte and wide character utilities <a href="#7.29"><wchar.h></a>
2484 (<a href="#7.29">7.29</a>), floating-point environment <a href="#7.6"><fenv.h></a> (<a href="#7.6">7.6</a>), general utilities <a href="#7.22"><stdlib.h></a>
2485 (<a href="#7.22">7.22</a>), input/output <a href="#7.21"><stdio.h></a> (<a href="#7.21">7.21</a>), mathematics <a href="#7.12"><math.h></a> (<a href="#7.12">7.12</a>).
2486 <!--page 53 -->
2488 <p><b>Footnotes</b>
2489 <p><small><a name="note21" href="#note21">21)</a> The floating-point model is intended to clarify the description of each floating-point characteristic and
2490 does not require the floating-point arithmetic of the implementation to be identical.
2491 </small>
2492 <p><small><a name="note22" href="#note22">22)</a> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
2493 IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
2494 similar behavior.
2495 </small>
2496 <p><small><a name="note23" href="#note23">23)</a> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
2498 </small>
2499 <p><small><a name="note24" href="#note24">24)</a> The evaluation method determines evaluation formats of expressions involving all floating types, not
2500 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
2501 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
2502 double.
2503 </small>
2504 <p><small><a name="note25" href="#note25">25)</a> Characterization as indeterminable is intended if floating-point operations do not consistently interpret
2505 subnormal representations as zero, nor as nonzero.
2506 </small>
2507 <p><small><a name="note26" href="#note26">26)</a> Characterization as absent is intended if no floating-point operations produce subnormal results from
2508 non-subnormal inputs, even if the type format includes representations of subnormal numbers.
2509 </small>
2510 <p><small><a name="note27" href="#note27">27)</a> If the presence or absence of subnormal numbers is indeterminable, then the value is intended to be a
2511 positive number no greater than the minimum normalized positive number for the type.
2512 </small>
2513 <p><small><a name="note28" href="#note28">28)</a> The floating-point model in that standard sums powers of b from zero, so the values of the exponent
2514 limits are one less than shown here.
2515 </small>
2522 <p><!--para 1 -->
2523 In the syntax notation used in this clause, syntactic categories (nonterminals) are
2524 indicated by italic type, and literal words and character set members (terminals) by bold
2525 type. A colon (:) following a nonterminal introduces its definition. Alternative
2526 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
2527 optional symbol is indicated by the subscript ''opt'', so that
2528 <pre>
2529 { expression<sub>opt</sub> }
2530 </pre>
2531 indicates an optional expression enclosed in braces.
2532 <p><!--para 2 -->
2533 When syntactic categories are referred to in the main text, they are not italicized and
2534 words are separated by spaces instead of hyphens.
2535 <p><!--para 3 -->
2543 <p><!--para 1 -->
2544 An identifier can denote an object; a function; a tag or a member of a structure, union, or
2545 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
2546 same identifier can denote different entities at different points in the program. A member
2547 of an enumeration is called an enumeration constant. Macro names and macro
2548 parameters are not considered further here, because prior to the semantic phase of
2549 program translation any occurrences of macro names in the source file are replaced by the
2550 preprocessing token sequences that constitute their macro definitions.
2551 <p><!--para 2 -->
2552 For each different entity that an identifier designates, the identifier is visible (i.e., can be
2553 used) only within a region of program text called its scope. Different entities designated
2554 by the same identifier either have different scopes, or are in different name spaces. There
2555 are four kinds of scopes: function, file, block, and function prototype. (A function
2556 prototype is a declaration of a function that declares the types of its parameters.)
2557 <p><!--para 3 -->
2558 A label name is the only kind of identifier that has function scope. It can be used (in a
2559 goto statement) anywhere in the function in which it appears, and is declared implicitly
2560 by its syntactic appearance (followed by a : and a statement).
2561 <p><!--para 4 -->
2562 Every other identifier has scope determined by the placement of its declaration (in a
2563 declarator or type specifier). If the declarator or type specifier that declares the identifier
2564 appears outside of any block or list of parameters, the identifier has file scope, which
2565 terminates at the end of the translation unit. If the declarator or type specifier that
2566 declares the identifier appears inside a block or within the list of parameter declarations in
2567 a function definition, the identifier has block scope, which terminates at the end of the
2568 associated block. If the declarator or type specifier that declares the identifier appears
2569 <!--page 54 -->
2570 within the list of parameter declarations in a function prototype (not part of a function
2571 definition), the identifier has function prototype scope, which terminates at the end of the
2572 function declarator. If an identifier designates two different entities in the same name
2573 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will end
2574 strictly before the scope of the other entity (the outer scope). Within the inner scope, the
2575 identifier designates the entity declared in the inner scope; the entity declared in the outer
2576 scope is hidden (and not visible) within the inner scope.
2577 <p><!--para 5 -->
2578 Unless explicitly stated otherwise, where this International Standard uses the term
2579 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
2580 entity in the relevant name space whose declaration is visible at the point the identifier
2581 occurs.
2582 <p><!--para 6 -->
2583 Two identifiers have the same scope if and only if their scopes terminate at the same
2584 point.
2585 <p><!--para 7 -->
2586 Structure, union, and enumeration tags have scope that begins just after the appearance of
2587 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
2588 begins just after the appearance of its defining enumerator in an enumerator list. Any
2589 other identifier has scope that begins just after the completion of its declarator.
2590 <p><!--para 8 -->
2591 As a special case, a type name (which is not a declaration of an identifier) is considered to
2592 have a scope that begins just after the place within the type name where the omitted
2593 identifier would appear were it not omitted.
2594 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), function definitions
2595 (<a href="#6.9.1">6.9.1</a>), identifiers (<a href="#6.4.2">6.4.2</a>), macro replacement (<a href="#6.10.3">6.10.3</a>), name spaces of identifiers (<a href="#6.2.3">6.2.3</a>),
2600 <p><!--para 1 -->
2601 An identifier declared in different scopes or in the same scope more than once can be
2602 made to refer to the same object or function by a process called linkage.<sup><a href="#note29"><b>29)</b></a></sup> There are
2603 three kinds of linkage: external, internal, and none.
2604 <p><!--para 2 -->
2605 In the set of translation units and libraries that constitutes an entire program, each
2606 declaration of a particular identifier with external linkage denotes the same object or
2607 function. Within one translation unit, each declaration of an identifier with internal
2608 linkage denotes the same object or function. Each declaration of an identifier with no
2609 linkage denotes a unique entity.
2610 <p><!--para 3 -->
2611 If the declaration of a file scope identifier for an object or a function contains the storage-
2612 class specifier static, the identifier has internal linkage.<sup><a href="#note30"><b>30)</b></a></sup>
2616 <!--page 55 -->
2617 <p><!--para 4 -->
2618 For an identifier declared with the storage-class specifier extern in a scope in which a
2619 prior declaration of that identifier is visible,<sup><a href="#note31"><b>31)</b></a></sup> if the prior declaration specifies internal or
2620 external linkage, the linkage of the identifier at the later declaration is the same as the
2621 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
2622 declaration specifies no linkage, then the identifier has external linkage.
2623 <p><!--para 5 -->
2624 If the declaration of an identifier for a function has no storage-class specifier, its linkage
2625 is determined exactly as if it were declared with the storage-class specifier extern. If
2626 the declaration of an identifier for an object has file scope and no storage-class specifier,
2627 its linkage is external.
2628 <p><!--para 6 -->
2629 The following identifiers have no linkage: an identifier declared to be anything other than
2630 an object or a function; an identifier declared to be a function parameter; a block scope
2631 identifier for an object declared without the storage-class specifier extern.
2632 <p><!--para 7 -->
2633 If, within a translation unit, the same identifier appears with both internal and external
2634 linkage, the behavior is undefined.
2635 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), external definitions (<a href="#6.9">6.9</a>),
2638 <p><b>Footnotes</b>
2639 <p><small><a name="note29" href="#note29">29)</a> There is no linkage between different identifiers.
2640 </small>
2641 <p><small><a name="note30" href="#note30">30)</a> A function declaration can contain the storage-class specifier static only if it is at file scope; see
2643 </small>
2644 <p><small><a name="note31" href="#note31">31)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2645 </small>
2649 <p><!--para 1 -->
2650 If more than one declaration of a particular identifier is visible at any point in a
2651 translation unit, the syntactic context disambiguates uses that refer to different entities.
2652 Thus, there are separate name spaces for various categories of identifiers, as follows:
2653 <ul>
2654 <li> label names (disambiguated by the syntax of the label declaration and use);
2655 <li> the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note32"><b>32)</b></a></sup>
2656 of the keywords struct, union, or enum);
2657 <li> the members of structures or unions; each structure or union has a separate name
2658 space for its members (disambiguated by the type of the expression used to access the
2659 member via the . or -> operator);
2660 <li> all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
2661 enumeration constants).
2662 </ul>
2663 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), labeled statements (<a href="#6.8.1">6.8.1</a>),
2664 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), structure and union members (<a href="#6.5.2.3">6.5.2.3</a>), tags
2667 <!--page 56 -->
2669 <p><b>Footnotes</b>
2670 <p><small><a name="note32" href="#note32">32)</a> There is only one name space for tags even though three are possible.
2671 </small>
2675 <p><!--para 1 -->
2676 An object has a storage duration that determines its lifetime. There are four storage
2677 durations: static, thread, automatic, and allocated. Allocated storage is described in
2679 <p><!--para 2 -->
2680 The lifetime of an object is the portion of program execution during which storage is
2681 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note33"><b>33)</b></a></sup> and retains
2682 its last-stored value throughout its lifetime.<sup><a href="#note34"><b>34)</b></a></sup> If an object is referred to outside of its
2683 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
2684 the object it points to (or just past) reaches the end of its lifetime.
2685 <p><!--para 3 -->
2686 An object whose identifier is declared without the storage-class specifier
2687 _Thread_local, and either with external or internal linkage or with the storage-class
2688 specifier static, has static storage duration. Its lifetime is the entire execution of the
2689 program and its stored value is initialized only once, prior to program startup.
2690 <p><!--para 4 -->
2691 An object whose identifier is declared with the storage-class specifier _Thread_local
2692 has thread storage duration. Its lifetime is the entire execution of the thread for which it
2693 is created, and its stored value is initialized when the thread is started. There is a distinct
2694 object per thread, and use of the declared name in an expression refers to the object
2695 associated with the thread evaluating the expression. The result of attempting to
2696 indirectly access an object with thread storage duration from a thread other than the one
2697 with which the object is associated is implementation-defined.
2698 <p><!--para 5 -->
2699 An object whose identifier is declared with no linkage and without the storage-class
2700 specifier static has automatic storage duration, as do some compound literals. The
2701 result of attempting to indirectly access an object with automatic storage duration from a
2702 thread other than the one with which the object is associated is implementation-defined.
2703 <p><!--para 6 -->
2704 For such an object that does not have a variable length array type, its lifetime extends
2705 from entry into the block with which it is associated until execution of that block ends in
2706 any way. (Entering an enclosed block or calling a function suspends, but does not end,
2707 execution of the current block.) If the block is entered recursively, a new instance of the
2708 object is created each time. The initial value of the object is indeterminate. If an
2709 initialization is specified for the object, it is performed each time the declaration or
2710 compound literal is reached in the execution of the block; otherwise, the value becomes
2711 indeterminate each time the declaration is reached.
2715 <!--page 57 -->
2716 <p><!--para 7 -->
2717 For such an object that does have a variable length array type, its lifetime extends from
2718 the declaration of the object until execution of the program leaves the scope of the
2719 declaration.<sup><a href="#note35"><b>35)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2720 each time. The initial value of the object is indeterminate.
2721 <p><!--para 8 -->
2722 A non-lvalue expression with structure or union type, where the structure or union
2723 contains a member with array type (including, recursively, members of all contained
2724 structures and unions) refers to an object with automatic storage duration and temporary
2725 lifetime.<sup><a href="#note36"><b>36)</b></a></sup> Its lifetime begins when the expression is evaluated and its initial value is the
2726 value of the expression. Its lifetime ends when the evaluation of the containing full
2727 expression or full declarator ends. Any attempt to modify an object with temporary
2728 lifetime results in undefined behavior.
2729 <p><b> Forward references</b>: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), compound literals (<a href="#6.5.2.5">6.5.2.5</a>), declarators
2730 (<a href="#6.7.6">6.7.6</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), initialization (<a href="#6.7.9">6.7.9</a>), statements (<a href="#6.8">6.8</a>).
2732 <p><b>Footnotes</b>
2733 <p><small><a name="note33" href="#note33">33)</a> The term ''constant address'' means that two pointers to the object constructed at possibly different
2734 times will compare equal. The address may be different during two different executions of the same
2735 program.
2736 </small>
2737 <p><small><a name="note34" href="#note34">34)</a> In the case of a volatile object, the last store need not be explicit in the program.
2738 </small>
2739 <p><small><a name="note35" href="#note35">35)</a> Leaving the innermost block containing the declaration, or jumping to a point in that block or an
2740 embedded block prior to the declaration, leaves the scope of the declaration.
2741 </small>
2742 <p><small><a name="note36" href="#note36">36)</a> The address of such an object is taken implicitly when an array member is accessed.
2743 </small>
2747 <p><!--para 1 -->
2748 The meaning of a value stored in an object or returned by a function is determined by the
2749 type of the expression used to access it. (An identifier declared to be an object is the
2750 simplest such expression; the type is specified in the declaration of the identifier.) Types
2751 are partitioned into object types (types that describe objects) and function types (types
2752 that describe functions). At various points within a translation unit an object type may be
2753 incomplete (lacking sufficient information to determine the size of objects of that type) or
2755 <p><!--para 2 -->
2756 An object declared as type _Bool is large enough to store the values 0 and 1.
2757 <p><!--para 3 -->
2758 An object declared as type char is large enough to store any member of the basic
2759 execution character set. If a member of the basic execution character set is stored in a
2760 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2761 a char object, the resulting value is implementation-defined but shall be within the range
2762 of values that can be represented in that type.
2763 <p><!--para 4 -->
2764 There are five standard signed integer types, designated as signed char, short
2765 int, int, long int, and long long int. (These and other types may be
2766 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2767 implementation-defined extended signed integer types.<sup><a href="#note38"><b>38)</b></a></sup> The standard and extended
2768 signed integer types are collectively called signed integer types.<sup><a href="#note39"><b>39)</b></a></sup>
2770 <!--page 58 -->
2771 <p><!--para 5 -->
2772 An object declared as type signed char occupies the same amount of storage as a
2773 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2774 architecture of the execution environment (large enough to contain any value in the range
2776 <p><!--para 6 -->
2777 For each of the signed integer types, there is a corresponding (but different) unsigned
2778 integer type (designated with the keyword unsigned) that uses the same amount of
2779 storage (including sign information) and has the same alignment requirements. The type
2780 _Bool and the unsigned integer types that correspond to the standard signed integer
2781 types are the standard unsigned integer types. The unsigned integer types that
2782 correspond to the extended signed integer types are the extended unsigned integer types.
2783 The standard and extended unsigned integer types are collectively called unsigned integer
2785 <p><!--para 7 -->
2786 The standard signed integer types and standard unsigned integer types are collectively
2787 called the standard integer types, the extended signed integer types and extended
2788 unsigned integer types are collectively called the extended integer types.
2789 <p><!--para 8 -->
2790 For any two integer types with the same signedness and different integer conversion rank
2791 (see <a href="#6.3.1.1">6.3.1.1</a>), the range of values of the type with smaller integer conversion rank is a
2792 subrange of the values of the other type.
2793 <p><!--para 9 -->
2794 The range of nonnegative values of a signed integer type is a subrange of the
2795 corresponding unsigned integer type, and the representation of the same value in each
2796 type is the same.<sup><a href="#note41"><b>41)</b></a></sup> A computation involving unsigned operands can never overflow,
2797 because a result that cannot be represented by the resulting unsigned integer type is
2798 reduced modulo the number that is one greater than the largest value that can be
2799 represented by the resulting type.
2800 <p><!--para 10 -->
2801 There are three real floating types, designated as float, double, and long
2802 double.<sup><a href="#note42"><b>42)</b></a></sup> The set of values of the type float is a subset of the set of values of the
2803 type double; the set of values of the type double is a subset of the set of values of the
2804 type long double.
2807 <!--page 59 -->
2808 <p><!--para 11 -->
2809 There are three complex types, designated as float _Complex, double
2810 _Complex, and long double _Complex.<sup><a href="#note43"><b>43)</b></a></sup> (Complex types are a conditional
2811 feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.) The real floating and
2812 complex types are collectively called the floating types.
2813 <p><!--para 12 -->
2814 For each floating type there is a corresponding real type, which is always a real floating
2815 type. For real floating types, it is the same type. For complex types, it is the type given
2816 by deleting the keyword _Complex from the type name.
2817 <p><!--para 13 -->
2818 Each complex type has the same representation and alignment requirements as an array
2819 type containing exactly two elements of the corresponding real type; the first element is
2820 equal to the real part, and the second element to the imaginary part, of the complex
2821 number.
2822 <p><!--para 14 -->
2823 The type char, the signed and unsigned integer types, and the floating types are
2824 collectively called the basic types. The basic types are complete object types. Even if the
2825 implementation defines two or more basic types to have the same representation, they are
2827 <p><!--para 15 -->
2828 The three types char, signed char, and unsigned char are collectively called
2829 the character types. The implementation shall define char to have the same range,
2830 representation, and behavior as either signed char or unsigned char.<sup><a href="#note45"><b>45)</b></a></sup>
2831 <p><!--para 16 -->
2832 An enumeration comprises a set of named integer constant values. Each distinct
2833 enumeration constitutes a different enumerated type.
2834 <p><!--para 17 -->
2835 The type char, the signed and unsigned integer types, and the enumerated types are
2836 collectively called integer types. The integer and real floating types are collectively called
2837 real types.
2838 <p><!--para 18 -->
2839 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2840 belongs to one type domain: the real type domain comprises the real types, the complex
2841 type domain comprises the complex types.
2842 <p><!--para 19 -->
2843 The void type comprises an empty set of values; it is an incomplete object type that
2844 cannot be completed.
2848 <!--page 60 -->
2849 <p><!--para 20 -->
2850 Any number of derived types can be constructed from the object and function types, as
2851 follows:
2852 <ul>
2853 <li> An array type describes a contiguously allocated nonempty set of objects with a
2854 particular member object type, called the element type. The element type shall be
2855 complete whenever the array type is specified. Array types are characterized by their
2856 element type and by the number of elements in the array. An array type is said to be
2857 derived from its element type, and if its element type is T , the array type is sometimes
2858 called ''array of T ''. The construction of an array type from an element type is called
2859 ''array type derivation''.
2860 <li> A structure type describes a sequentially allocated nonempty set of member objects
2861 (and, in certain circumstances, an incomplete array), each of which has an optionally
2862 specified name and possibly distinct type.
2863 <li> A union type describes an overlapping nonempty set of member objects, each of
2864 which has an optionally specified name and possibly distinct type.
2865 <li> A function type describes a function with specified return type. A function type is
2866 characterized by its return type and the number and types of its parameters. A
2867 function type is said to be derived from its return type, and if its return type is T , the
2868 function type is sometimes called ''function returning T ''. The construction of a
2869 function type from a return type is called ''function type derivation''.
2870 <li> A pointer type may be derived from a function type or an object type, called the
2871 referenced type. A pointer type describes an object whose value provides a reference
2872 to an entity of the referenced type. A pointer type derived from the referenced type T
2873 is sometimes called ''pointer to T ''. The construction of a pointer type from a
2874 referenced type is called ''pointer type derivation''. A pointer type is a complete
2875 object type.
2876 <li> An atomic type describes the type designated by the construct _Atomic ( type-
2877 name ). (Atomic types are a conditional feature that implementations need not
2879 </ul>
2880 These methods of constructing derived types can be applied recursively.
2881 <p><!--para 21 -->
2882 Arithmetic types and pointer types are collectively called scalar types. Array and
2883 structure types are collectively called aggregate types.<sup><a href="#note46"><b>46)</b></a></sup>
2884 <p><!--para 22 -->
2885 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2886 that type, by specifying the size in a later declaration (with internal or external linkage).
2887 A structure or union type of unknown content (as described in <a href="#6.7.2.3">6.7.2.3</a>) is an incomplete
2890 <!--page 61 -->
2891 type. It is completed, for all declarations of that type, by declaring the same structure or
2892 union tag with its defining content later in the same scope.
2893 <p><!--para 23 -->
2894 A type has known constant size if the type is not incomplete and is not a variable length
2895 array type.
2896 <p><!--para 24 -->
2897 Array, function, and pointer types are collectively called derived declarator types. A
2898 declarator type derivation from a type T is the construction of a derived declarator type
2899 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2900 T.
2901 <p><!--para 25 -->
2902 A type is characterized by its type category, which is either the outermost derivation of a
2903 derived type (as noted above in the construction of derived types), or the type itself if the
2904 type consists of no derived types.
2905 <p><!--para 26 -->
2906 Any type so far mentioned is an unqualified type. Each unqualified type has several
2907 qualified versions of its type,<sup><a href="#note47"><b>47)</b></a></sup> corresponding to the combinations of one, two, or all
2908 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2909 versions of a type are distinct types that belong to the same type category and have the
2910 same representation and alignment requirements.<sup><a href="#note48"><b>48)</b></a></sup> A derived type is not qualified by the
2911 qualifiers (if any) of the type from which it is derived.
2912 <p><!--para 27 -->
2913 Further, there is the _Atomic qualifier. The presence of the _Atomic qualifier
2914 designates an atomic type. The size, representation, and alignment of an atomic type
2915 need not be the same as those of the corresponding unqualified type. Therefore, this
2916 Standard explicitly uses the phrase ''atomic, qualified or unqualified type'' whenever the
2917 atomic version of a type is permitted along with the other qualified versions of a type.
2918 The phrase ''qualified or unqualified type'', without specific mention of atomic, does not
2919 include the atomic types.
2920 <p><!--para 28 -->
2921 A pointer to void shall have the same representation and alignment requirements as a
2922 pointer to a character type.<sup><a href="#note48"><b>48)</b></a></sup> Similarly, pointers to qualified or unqualified versions of
2923 compatible types shall have the same representation and alignment requirements. All
2924 pointers to structure types shall have the same representation and alignment requirements
2925 as each other. All pointers to union types shall have the same representation and
2926 alignment requirements as each other. Pointers to other types need not have the same
2927 representation or alignment requirements.
2928 <p><!--para 29 -->
2929 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2930 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2931 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2934 <!--page 62 -->
2935 qualified float'' and is a pointer to a qualified type.
2937 <p><!--para 30 -->
2938 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
2939 function returning struct tag''. The array has length five and the function has a single parameter of type
2940 float. Its type category is array.
2942 <p><b> Forward references</b>: compatible type and composite type (<a href="#6.2.7">6.2.7</a>), declarations (<a href="#6.7">6.7</a>).
2944 <p><b>Footnotes</b>
2945 <p><small><a name="note37" href="#note37">37)</a> A type may be incomplete or complete throughout an entire translation unit, or it may change states at
2946 different points within a translation unit.
2947 </small>
2948 <p><small><a name="note38" href="#note38">38)</a> Implementation-defined keywords shall have the form of an identifier reserved for any use as
2950 </small>
2951 <p><small><a name="note39" href="#note39">39)</a> Therefore, any statement in this Standard about signed integer types also applies to the extended
2952 signed integer types.
2953 </small>
2954 <p><small><a name="note40" href="#note40">40)</a> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2955 unsigned integer types.
2956 </small>
2957 <p><small><a name="note41" href="#note41">41)</a> The same representation and alignment requirements are meant to imply interchangeability as
2958 arguments to functions, return values from functions, and members of unions.
2959 </small>
2960 <p><small><a name="note42" href="#note42">42)</a> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2961 </small>
2962 <p><small><a name="note43" href="#note43">43)</a> A specification for imaginary types is in <a href="#G">annex G</a>.
2963 </small>
2964 <p><small><a name="note44" href="#note44">44)</a> An implementation may define new keywords that provide alternative ways to designate a basic (or
2965 any other) type; this does not violate the requirement that all basic types be different.
2966 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2968 </small>
2969 <p><small><a name="note45" href="#note45">45)</a> CHAR_MIN, defined in <a href="#7.10"><limits.h></a>, will have one of the values 0 or SCHAR_MIN, and this can be
2970 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2971 other two and is not compatible with either.
2972 </small>
2973 <p><small><a name="note46" href="#note46">46)</a> Note that aggregate type does not include union type because an object with union type can only
2974 contain one member at a time.
2975 </small>
2976 <p><small><a name="note47" href="#note47">47)</a> See <a href="#6.7.3">6.7.3</a> regarding qualified array and function types.
2977 </small>
2978 <p><small><a name="note48" href="#note48">48)</a> The same representation and alignment requirements are meant to imply interchangeability as
2979 arguments to functions, return values from functions, and members of unions.
2980 </small>
2987 <p><!--para 1 -->
2988 The representations of all types are unspecified except as stated in this subclause.
2989 <p><!--para 2 -->
2990 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2991 the number, order, and encoding of which are either explicitly specified or
2992 implementation-defined.
2993 <p><!--para 3 -->
2994 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2996 <p><!--para 4 -->
2997 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2998 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2999 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
3000 called the object representation of the value. Values stored in bit-fields consist of m bits,
3001 where m is the size specified for the bit-field. The object representation is the set of m
3002 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
3003 than NaNs) with the same object representation compare equal, but values that compare
3004 equal may have different object representations.
3005 <p><!--para 5 -->
3006 Certain object representations need not represent a value of the object type. If the stored
3007 value of an object has such a representation and is read by an lvalue expression that does
3008 not have character type, the behavior is undefined. If such a representation is produced
3009 by a side effect that modifies all or any part of the object by an lvalue expression that
3010 does not have character type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup> Such a representation is called
3011 a trap representation.
3012 <p><!--para 6 -->
3013 When a value is stored in an object of structure or union type, including in a member
3014 object, the bytes of the object representation that correspond to any padding bytes take
3015 unspecified values.<sup><a href="#note51"><b>51)</b></a></sup> The value of a structure or union object is never a trap
3018 <!--page 63 -->
3019 representation, even though the value of a member of the structure or union object may be
3020 a trap representation.
3021 <p><!--para 7 -->
3022 When a value is stored in a member of an object of union type, the bytes of the object
3023 representation that do not correspond to that member but do correspond to other members
3024 take unspecified values.
3025 <p><!--para 8 -->
3026 Where an operator is applied to a value that has more than one object representation,
3027 which object representation is used shall not affect the value of the result.<sup><a href="#note52"><b>52)</b></a></sup> Where a
3028 value is stored in an object using a type that has more than one object representation for
3029 that value, it is unspecified which representation is used, but a trap representation shall
3030 not be generated.
3031 <p><!--para 9 -->
3032 Loads and stores of objects with atomic types are done with
3033 memory_order_seq_cst semantics.
3034 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), lvalues, arrays, and function
3035 designators (<a href="#6.3.2.1">6.3.2.1</a>), order and consistency (<a href="#7.17.3">7.17.3</a>).
3037 <p><b>Footnotes</b>
3038 <p><small><a name="note49" href="#note49">49)</a> A positional representation for integers that uses the binary digits 0 and 1, in which the values
3039 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
3040 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
3041 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
3042 type unsigned char range from 0 to 2
3044 <pre>
3045 CHAR_BIT
3046 - 1.
3047 </pre>
3048 </small>
3049 <p><small><a name="note50" href="#note50">50)</a> Thus, an automatic variable can be initialized to a trap representation without causing undefined
3050 behavior, but the value of the variable cannot be used until a proper value is stored in it.
3051 </small>
3052 <p><small><a name="note51" href="#note51">51)</a> Thus, for example, structure assignment need not copy any padding bits.
3053 </small>
3054 <p><small><a name="note52" href="#note52">52)</a> It is possible for objects x and y with the same effective type T to have the same value when they are
3055 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
3056 defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
3057 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
3058 on values of type T may distinguish between them.
3059 </small>
3063 <p><!--para 1 -->
3064 For unsigned integer types other than unsigned char, the bits of the object
3065 representation shall be divided into two groups: value bits and padding bits (there need
3066 not be any of the latter). If there are N value bits, each bit shall represent a different
3067 power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of
3068 representing values from 0 to 2 N - 1 using a pure binary representation; this shall be
3069 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note53"><b>53)</b></a></sup>
3070 <p><!--para 2 -->
3071 For signed integer types, the bits of the object representation shall be divided into three
3072 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
3073 signed char shall not have any padding bits. There shall be exactly one sign bit.
3074 Each bit that is a value bit shall have the same value as the same bit in the object
3075 representation of the corresponding unsigned type (if there are M value bits in the signed
3076 type and N in the unsigned type, then M <= N ). If the sign bit is zero, it shall not affect
3078 <!--page 64 -->
3079 the resulting value. If the sign bit is one, the value shall be modified in one of the
3080 following ways:
3081 <ul>
3082 <li> the corresponding value with sign bit 0 is negated (sign and magnitude);
3083 <li> the sign bit has the value -(2 M ) (two's complement);
3084 <li> the sign bit has the value -(2 M - 1) (ones' complement).
3085 </ul>
3086 Which of these applies is implementation-defined, as is whether the value with sign bit 1
3087 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
3088 complement), is a trap representation or a normal value. In the case of sign and
3089 magnitude and ones' complement, if this representation is a normal value it is called a
3090 negative zero.
3091 <p><!--para 3 -->
3092 If the implementation supports negative zeros, they shall be generated only by:
3093 <ul>
3094 <li> the &, |, ^, ~, <<, and >> operators with operands that produce such a value;
3095 <li> the +, -, *, /, and % operators where one operand is a negative zero and the result is
3096 zero;
3097 <li> compound assignment operators based on the above cases.
3098 </ul>
3099 It is unspecified whether these cases actually generate a negative zero or a normal zero,
3100 and whether a negative zero becomes a normal zero when stored in an object.
3101 <p><!--para 4 -->
3102 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
3103 and >> operators with operands that would produce such a value is undefined.
3104 <p><!--para 5 -->
3105 The values of any padding bits are unspecified.<sup><a href="#note54"><b>54)</b></a></sup> A valid (non-trap) object representation
3106 of a signed integer type where the sign bit is zero is a valid object representation of the
3107 corresponding unsigned type, and shall represent the same value. For any integer type,
3108 the object representation where all the bits are zero shall be a representation of the value
3109 zero in that type.
3110 <p><!--para 6 -->
3111 The precision of an integer type is the number of bits it uses to represent values,
3112 excluding any sign and padding bits. The width of an integer type is the same but
3113 including any sign bit; thus for unsigned integer types the two values are the same, while
3114 for signed integer types the width is one greater than the precision.
3119 <!--page 65 -->
3121 <p><b>Footnotes</b>
3122 <p><small><a name="note53" href="#note53">53)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
3123 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
3124 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
3125 with unsigned types. All other combinations of padding bits are alternative object representations of
3126 the value specified by the value bits.
3127 </small>
3128 <p><small><a name="note54" href="#note54">54)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
3129 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
3130 representation other than as part of an exceptional condition such as an overflow. All other
3131 combinations of padding bits are alternative object representations of the value specified by the value
3132 bits.
3133 </small>
3137 <p><!--para 1 -->
3138 Two types have compatible type if their types are the same. Additional rules for
3139 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
3140 in <a href="#6.7.3">6.7.3</a> for type qualifiers, and in <a href="#6.7.6">6.7.6</a> for declarators.<sup><a href="#note55"><b>55)</b></a></sup> Moreover, two structure,
3141 union, or enumerated types declared in separate translation units are compatible if their
3142 tags and members satisfy the following requirements: If one is declared with a tag, the
3143 other shall be declared with the same tag. If both are completed anywhere within their
3144 respective translation units, then the following additional requirements apply: there shall
3145 be a one-to-one correspondence between their members such that each pair of
3146 corresponding members are declared with compatible types; if one member of the pair is
3147 declared with an alignment specifier, the other is declared with an equivalent alignment
3148 specifier; and if one member of the pair is declared with a name, the other is declared
3149 with the same name. For two structures, corresponding members shall be declared in the
3150 same order. For two structures or unions, corresponding bit-fields shall have the same
3151 widths. For two enumerations, corresponding members shall have the same values.
3152 <p><!--para 2 -->
3153 All declarations that refer to the same object or function shall have compatible type;
3154 otherwise, the behavior is undefined.
3155 <p><!--para 3 -->
3156 A composite type can be constructed from two types that are compatible; it is a type that
3157 is compatible with both of the two types and satisfies the following conditions:
3158 <ul>
3159 <li> If both types are array types, the following rules are applied:
3160 <ul>
3161 <li> If one type is an array of known constant size, the composite type is an array of
3162 that size.
3163 <li> Otherwise, if one type is a variable length array whose size is specified by an
3164 expression that is not evaluated, the behavior is undefined.
3165 <li> Otherwise, if one type is a variable length array whose size is specified, the
3166 composite type is a variable length array of that size.
3167 <li> Otherwise, if one type is a variable length array of unspecified size, the composite
3168 type is a variable length array of unspecified size.
3169 <li> Otherwise, both types are arrays of unknown size and the composite type is an
3170 array of unknown size.
3171 </ul>
3172 The element type of the composite type is the composite type of the two element
3173 types.
3174 <li> If only one type is a function type with a parameter type list (a function prototype),
3175 the composite type is a function prototype with the parameter type list.
3178 <!--page 66 -->
3179 <li> If both types are function types with parameter type lists, the type of each parameter
3180 in the composite parameter type list is the composite type of the corresponding
3181 parameters.
3182 </ul>
3183 These rules apply recursively to the types from which the two types are derived.
3184 <p><!--para 4 -->
3185 For an identifier with internal or external linkage declared in a scope in which a prior
3186 declaration of that identifier is visible,<sup><a href="#note56"><b>56)</b></a></sup> if the prior declaration specifies internal or
3187 external linkage, the type of the identifier at the later declaration becomes the composite
3188 type.
3190 <p><!--para 5 -->
3191 EXAMPLE Given the following two file scope declarations:
3192 <pre>
3193 int f(int (*)(), double (*)[3]);
3194 int f(int (*)(char *), double (*)[]);
3195 </pre>
3196 The resulting composite type for the function is:
3197 <pre>
3198 int f(int (*)(char *), double (*)[3]);
3199 </pre>
3202 <p><b>Footnotes</b>
3203 <p><small><a name="note55" href="#note55">55)</a> Two types need not be identical to be compatible.
3204 </small>
3205 <p><small><a name="note56" href="#note56">56)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
3206 </small>
3210 <p><!--para 1 -->
3211 Complete object types have alignment requirements which place restrictions on the
3212 addresses at which objects of that type may be allocated. An alignment is an
3213 implementation-defined integer value representing the number of bytes between
3214 successive addresses at which a given object can be allocated. An object type imposes an
3215 alignment requirement on every object of that type: stricter alignment can be requested
3216 using the _Alignas keyword.
3217 <p><!--para 2 -->
3218 A fundamental alignment is represented by an alignment less than or equal to the greatest
3219 alignment supported by the implementation in all contexts, which is equal to
3220 _Alignof (max_align_t).
3221 <p><!--para 3 -->
3222 An extended alignment is represented by an alignment greater than
3223 _Alignof (max_align_t). It is implementation-defined whether any extended
3224 alignments are supported and the contexts in which they are supported. A type having an
3225 extended alignment requirement is an over-aligned type.<sup><a href="#note57"><b>57)</b></a></sup>
3226 <p><!--para 4 -->
3227 Alignments are represented as values of the type size_t. Valid alignments include only
3228 those values returned by an _Alignof expression for fundamental types, plus an
3229 additional implementation-defined set of values, which may be empty. Every valid
3230 alignment value shall be a nonnegative integral power of two.
3233 <!--page 67 -->
3234 <p><!--para 5 -->
3235 Alignments have an order from weaker to stronger or stricter alignments. Stricter
3236 alignments have larger alignment values. An address that satisfies an alignment
3237 requirement also satisfies any weaker valid alignment requirement.
3238 <p><!--para 6 -->
3239 The alignment requirement of a complete type can be queried using an _Alignof
3240 expression. The types char, signed char, and unsigned char shall have the
3241 weakest alignment requirement.
3242 <p><!--para 7 -->
3243 Comparing alignments is meaningful and provides the obvious results:
3244 <ul>
3245 <li> Two alignments are equal when their numeric values are equal.
3246 <li> Two alignments are different when their numeric values are not equal.
3247 <li> When an alignment is larger than another it represents a stricter alignment.
3248 <!--page 68 -->
3249 </ul>
3251 <p><b>Footnotes</b>
3252 <p><small><a name="note57" href="#note57">57)</a> Every over-aligned type is, or contains, a structure or union type with a member to which an extended
3253 alignment has been applied.
3254 </small>
3258 <p><!--para 1 -->
3259 Several operators convert operand values from one type to another automatically. This
3260 subclause specifies the result required from such an implicit conversion, as well as those
3261 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
3262 the conversions performed by most ordinary operators; it is supplemented as required by
3264 <p><!--para 2 -->
3265 Conversion of an operand value to a compatible type causes no change to the value or the
3266 representation.
3274 <p><!--para 1 -->
3275 Every integer type has an integer conversion rank defined as follows:
3276 <ul>
3277 <li> No two signed integer types shall have the same rank, even if they have the same
3278 representation.
3279 <li> The rank of a signed integer type shall be greater than the rank of any signed integer
3280 type with less precision.
3281 <li> The rank of long long int shall be greater than the rank of long int, which
3282 shall be greater than the rank of int, which shall be greater than the rank of short
3283 int, which shall be greater than the rank of signed char.
3284 <li> The rank of any unsigned integer type shall equal the rank of the corresponding
3285 signed integer type, if any.
3286 <li> The rank of any standard integer type shall be greater than the rank of any extended
3287 integer type with the same width.
3288 <li> The rank of char shall equal the rank of signed char and unsigned char.
3289 <li> The rank of _Bool shall be less than the rank of all other standard integer types.
3290 <li> The rank of any enumerated type shall equal the rank of the compatible integer type
3292 <li> The rank of any extended signed integer type relative to another extended signed
3293 integer type with the same precision is implementation-defined, but still subject to the
3294 other rules for determining the integer conversion rank.
3295 <li> For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
3296 greater rank than T3, then T1 has greater rank than T3.
3297 </ul>
3298 <p><!--para 2 -->
3299 The following may be used in an expression wherever an int or unsigned int may
3300 be used:
3301 <!--page 69 -->
3302 <ul>
3303 <li> An object or expression with an integer type (other than int or unsigned int)
3304 whose integer conversion rank is less than or equal to the rank of int and
3305 unsigned int.
3306 <li> A bit-field of type _Bool, int, signed int, or unsigned int.
3307 </ul>
3308 If an int can represent all values of the original type (as restricted by the width, for a
3309 bit-field), the value is converted to an int; otherwise, it is converted to an unsigned
3310 int. These are called the integer promotions.<sup><a href="#note58"><b>58)</b></a></sup> All other types are unchanged by the
3311 integer promotions.
3312 <p><!--para 3 -->
3313 The integer promotions preserve value including sign. As discussed earlier, whether a
3314 ''plain'' char is treated as signed is implementation-defined.
3315 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
3318 <p><b>Footnotes</b>
3319 <p><small><a name="note58" href="#note58">58)</a> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
3320 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
3321 shift operators, as specified by their respective subclauses.
3322 </small>
3326 <p><!--para 1 -->
3327 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
3330 <p><b>Footnotes</b>
3331 <p><small><a name="note59" href="#note59">59)</a> NaNs do not compare equal to 0 and thus convert to 1.
3332 </small>
3336 <p><!--para 1 -->
3337 When a value with integer type is converted to another integer type other than _Bool, if
3338 the value can be represented by the new type, it is unchanged.
3339 <p><!--para 2 -->
3340 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
3341 subtracting one more than the maximum value that can be represented in the new type
3343 <p><!--para 3 -->
3344 Otherwise, the new type is signed and the value cannot be represented in it; either the
3345 result is implementation-defined or an implementation-defined signal is raised.
3347 <p><b>Footnotes</b>
3348 <p><small><a name="note60" href="#note60">60)</a> The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
3349 </small>
3353 <p><!--para 1 -->
3354 When a finite value of real floating type is converted to an integer type other than _Bool,
3355 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
3356 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note61"><b>61)</b></a></sup>
3359 <!--page 70 -->
3360 <p><!--para 2 -->
3361 When a value of integer type is converted to a real floating type, if the value being
3362 converted can be represented exactly in the new type, it is unchanged. If the value being
3363 converted is in the range of values that can be represented but cannot be represented
3364 exactly, the result is either the nearest higher or nearest lower representable value, chosen
3365 in an implementation-defined manner. If the value being converted is outside the range of
3366 values that can be represented, the behavior is undefined. Results of some implicit
3367 conversions may be represented in greater range and precision than that required by the
3370 <p><b>Footnotes</b>
3371 <p><small><a name="note61" href="#note61">61)</a> The remaindering operation performed when a value of integer type is converted to unsigned type
3372 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
3373 range of portable real floating values is (-1, Utype_MAX+1).
3374 </small>
3378 <p><!--para 1 -->
3379 When a value of real floating type is converted to a real floating type, if the value being
3380 converted can be represented exactly in the new type, it is unchanged. If the value being
3381 converted is in the range of values that can be represented but cannot be represented
3382 exactly, the result is either the nearest higher or nearest lower representable value, chosen
3383 in an implementation-defined manner. If the value being converted is outside the range of
3384 values that can be represented, the behavior is undefined. Results of some implicit
3385 conversions may be represented in greater range and precision than that required by the
3390 <p><!--para 1 -->
3391 When a value of complex type is converted to another complex type, both the real and
3392 imaginary parts follow the conversion rules for the corresponding real types.
3396 <p><!--para 1 -->
3397 When a value of real type is converted to a complex type, the real part of the complex
3398 result value is determined by the rules of conversion to the corresponding real type and
3399 the imaginary part of the complex result value is a positive zero or an unsigned zero.
3400 <p><!--para 2 -->
3401 When a value of complex type is converted to a real type, the imaginary part of the
3402 complex value is discarded and the value of the real part is converted according to the
3403 conversion rules for the corresponding real type.
3407 <p><!--para 1 -->
3408 Many operators that expect operands of arithmetic type cause conversions and yield result
3409 types in a similar way. The purpose is to determine a common real type for the operands
3410 and result. For the specified operands, each operand is converted, without change of type
3411 domain, to a type whose corresponding real type is the common real type. Unless
3412 explicitly stated otherwise, the common real type is also the corresponding real type of
3413 the result, whose type domain is the type domain of the operands if they are the same,
3414 and complex otherwise. This pattern is called the usual arithmetic conversions:
3415 <!--page 71 -->
3416 <pre>
3417 First, if the corresponding real type of either operand is long double, the other
3418 operand is converted, without change of type domain, to a type whose
3419 corresponding real type is long double.
3420 Otherwise, if the corresponding real type of either operand is double, the other
3421 operand is converted, without change of type domain, to a type whose
3422 corresponding real type is double.
3423 Otherwise, if the corresponding real type of either operand is float, the other
3424 operand is converted, without change of type domain, to a type whose
3426 Otherwise, the integer promotions are performed on both operands. Then the
3427 following rules are applied to the promoted operands:
3428 If both operands have the same type, then no further conversion is needed.
3429 Otherwise, if both operands have signed integer types or both have unsigned
3430 integer types, the operand with the type of lesser integer conversion rank is
3431 converted to the type of the operand with greater rank.
3432 Otherwise, if the operand that has unsigned integer type has rank greater or
3433 equal to the rank of the type of the other operand, then the operand with
3434 signed integer type is converted to the type of the operand with unsigned
3435 integer type.
3436 Otherwise, if the type of the operand with signed integer type can represent
3437 all of the values of the type of the operand with unsigned integer type, then
3438 the operand with unsigned integer type is converted to the type of the
3439 operand with signed integer type.
3440 Otherwise, both operands are converted to the unsigned integer type
3441 corresponding to the type of the operand with signed integer type.
3442 </pre>
3443 <p><!--para 2 -->
3444 The values of floating operands and of the results of floating expressions may be
3445 represented in greater range and precision than that required by the type; the types are not
3451 <!--page 72 -->
3453 <p><b>Footnotes</b>
3454 <p><small><a name="note62" href="#note62">62)</a> For example, addition of a double _Complex and a float entails just the conversion of the
3455 float operand to double (and yields a double _Complex result).
3456 </small>
3457 <p><small><a name="note63" href="#note63">63)</a> The cast and assignment operators are still required to remove extra range and precision.
3458 </small>
3464 <h5><a name="6.3.2.1" href="#6.3.2.1">6.3.2.1 Lvalues, arrays, and function designators</a></h5>
3465 <p><!--para 1 -->
3466 An lvalue is an expression (with an object type other than void) that potentially
3467 designates an object;<sup><a href="#note64"><b>64)</b></a></sup> if an lvalue does not designate an object when it is evaluated, the
3468 behavior is undefined. When an object is said to have a particular type, the type is
3469 specified by the lvalue used to designate the object. A modifiable lvalue is an lvalue that
3470 does not have array type, does not have an incomplete type, does not have a const-
3471 qualified type, and if it is a structure or union, does not have any member (including,
3472 recursively, any member or element of all contained aggregates or unions) with a const-
3473 qualified type.
3474 <p><!--para 2 -->
3475 Except when it is the operand of the sizeof operator, the _Alignof operator, the
3476 unary & operator, the ++ operator, the -- operator, or the left operand of the . operator
3477 or an assignment operator, an lvalue that does not have array type is converted to the
3478 value stored in the designated object (and is no longer an lvalue); this is called lvalue
3479 conversion. If the lvalue has qualified type, the value has the unqualified version of the
3480 type of the lvalue; additionally, if the lvalue has atomic type, the value has the non-atomic
3481 version of the type of the lvalue; otherwise, the value has the type of the lvalue. If the
3482 lvalue has an incomplete type and does not have array type, the behavior is undefined. If
3483 the lvalue designates an object of automatic storage duration that could have been
3484 declared with the register storage class (never had its address taken), and that object
3485 is uninitialized (not declared with an initializer and no assignment to it has been
3486 performed prior to use), the behavior is undefined.
3487 <p><!--para 3 -->
3488 Except when it is the operand of the sizeof operator, the _Alignof operator, or the
3489 unary & operator, or is a string literal used to initialize an array, an expression that has
3490 type ''array of type'' is converted to an expression with type ''pointer to type'' that points
3491 to the initial element of the array object and is not an lvalue. If the array object has
3492 register storage class, the behavior is undefined.
3493 <p><!--para 4 -->
3494 A function designator is an expression that has function type. Except when it is the
3495 operand of the sizeof operator, the _Alignof operator,<sup><a href="#note65"><b>65)</b></a></sup> or the unary & operator, a
3496 function designator with type ''function returning type'' is converted to an expression that
3499 <!--page 73 -->
3500 has type ''pointer to function returning type''.
3501 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
3502 (<a href="#6.5.16">6.5.16</a>), common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), initialization (<a href="#6.7.9">6.7.9</a>), postfix
3503 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
3504 (<a href="#6.5.3.1">6.5.3.1</a>), the sizeof and _Alignof operators (<a href="#6.5.3.4">6.5.3.4</a>), structure and union members
3507 <p><b>Footnotes</b>
3508 <p><small><a name="note64" href="#note64">64)</a> The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
3509 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
3510 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
3511 as the ''value of an expression''.
3512 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
3513 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
3514 </small>
3515 <p><small><a name="note65" href="#note65">65)</a> Because this conversion does not occur, the operand of the sizeof or _Alignof operator remains
3517 </small>
3521 <p><!--para 1 -->
3522 The (nonexistent) value of a void expression (an expression that has type void) shall not
3523 be used in any way, and implicit or explicit conversions (except to void) shall not be
3524 applied to such an expression. If an expression of any other type is evaluated as a void
3525 expression, its value or designator is discarded. (A void expression is evaluated for its
3526 side effects.)
3530 <p><!--para 1 -->
3531 A pointer to void may be converted to or from a pointer to any object type. A pointer to
3532 any object type may be converted to a pointer to void and back again; the result shall
3533 compare equal to the original pointer.
3534 <p><!--para 2 -->
3535 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
3536 the q-qualified version of the type; the values stored in the original and converted pointers
3537 shall compare equal.
3538 <p><!--para 3 -->
3539 An integer constant expression with the value 0, or such an expression cast to type
3540 void *, is called a null pointer constant.<sup><a href="#note66"><b>66)</b></a></sup> If a null pointer constant is converted to a
3541 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
3542 to a pointer to any object or function.
3543 <p><!--para 4 -->
3544 Conversion of a null pointer to another pointer type yields a null pointer of that type.
3545 Any two null pointers shall compare equal.
3546 <p><!--para 5 -->
3547 An integer may be converted to any pointer type. Except as previously specified, the
3548 result is implementation-defined, might not be correctly aligned, might not point to an
3549 entity of the referenced type, and might be a trap representation.<sup><a href="#note67"><b>67)</b></a></sup>
3550 <p><!--para 6 -->
3551 Any pointer type may be converted to an integer type. Except as previously specified, the
3552 result is implementation-defined. If the result cannot be represented in the integer type,
3553 the behavior is undefined. The result need not be in the range of values of any integer
3554 type.
3557 <!--page 74 -->
3558 <p><!--para 7 -->
3559 A pointer to an object type may be converted to a pointer to a different object type. If the
3560 resulting pointer is not correctly aligned<sup><a href="#note68"><b>68)</b></a></sup> for the referenced type, the behavior is
3561 undefined. Otherwise, when converted back again, the result shall compare equal to the
3562 original pointer. When a pointer to an object is converted to a pointer to a character type,
3563 the result points to the lowest addressed byte of the object. Successive increments of the
3564 result, up to the size of the object, yield pointers to the remaining bytes of the object.
3565 <p><!--para 8 -->
3566 A pointer to a function of one type may be converted to a pointer to a function of another
3567 type and back again; the result shall compare equal to the original pointer. If a converted
3568 pointer is used to call a function whose type is not compatible with the referenced type,
3569 the behavior is undefined.
3570 <p><b> Forward references</b>: cast operators (<a href="#6.5.4">6.5.4</a>), equality operators (<a href="#6.5.9">6.5.9</a>), integer types
3571 capable of holding object pointers (<a href="#7.20.1.4">7.20.1.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
3576 <!--page 75 -->
3578 <p><b>Footnotes</b>
3579 <p><small><a name="note66" href="#note66">66)</a> The macro NULL is defined in <a href="#7.19"><stddef.h></a> (and other headers) as a null pointer constant; see <a href="#7.19">7.19</a>.
3580 </small>
3581 <p><small><a name="note67" href="#note67">67)</a> The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to
3582 be consistent with the addressing structure of the execution environment.
3583 </small>
3584 <p><small><a name="note68" href="#note68">68)</a> In general, the concept ''correctly aligned'' is transitive: if a pointer to type A is correctly aligned for a
3585 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
3586 correctly aligned for a pointer to type C.
3587 </small>
3591 <p><b>Syntax</b>
3592 <p><!--para 1 -->
3593 <pre>
3594 token:
3595 keyword
3596 identifier
3597 constant
3598 string-literal
3599 punctuator
3600 preprocessing-token:
3601 header-name
3602 identifier
3603 pp-number
3604 character-constant
3605 string-literal
3606 punctuator
3607 each non-white-space character that cannot be one of the above
3608 </pre>
3609 <p><b>Constraints</b>
3610 <p><!--para 2 -->
3611 Each preprocessing token that is converted to a token shall have the lexical form of a
3612 keyword, an identifier, a constant, a string literal, or a punctuator.
3613 <p><b>Semantics</b>
3614 <p><!--para 3 -->
3615 A token is the minimal lexical element of the language in translation phases 7 and 8. The
3616 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
3617 A preprocessing token is the minimal lexical element of the language in translation
3618 phases 3 through 6. The categories of preprocessing tokens are: header names,
3619 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
3620 single non-white-space characters that do not lexically match the other preprocessing
3621 token categories.<sup><a href="#note69"><b>69)</b></a></sup> If a ' or a " character matches the last category, the behavior is
3622 undefined. Preprocessing tokens can be separated by white space; this consists of
3623 comments (described later), or white-space characters (space, horizontal tab, new-line,
3624 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
3625 during translation phase 4, white space (or the absence thereof) serves as more than
3626 preprocessing token separation. White space may appear within a preprocessing token
3627 only as part of a header name or between the quotation characters in a character constant
3628 or string literal.
3632 <!--page 76 -->
3634 If the input stream has been parsed into preprocessing tokens up to a given character, the
3635 next preprocessing token is the longest sequence of characters that could constitute a
3636 preprocessing token. There is one exception to this rule: header name preprocessing
3637 tokens are recognized only within #include preprocessing directives and in
3638 implementation-defined locations within #pragma directives. In such contexts, a
3639 sequence of characters that could be either a header name or a string literal is recognized
3640 as the former.
3642 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
3643 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
3644 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
3645 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
3646 not E is a macro name.
3649 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
3650 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
3652 <p><b> Forward references</b>: character constants (<a href="#6.4.4.4">6.4.4.4</a>), comments (<a href="#6.4.9">6.4.9</a>), expressions (<a href="#6.5">6.5</a>),
3653 floating constants (<a href="#6.4.4.2">6.4.4.2</a>), header names (<a href="#6.4.7">6.4.7</a>), macro replacement (<a href="#6.10.3">6.10.3</a>), postfix
3654 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
3655 (<a href="#6.5.3.1">6.5.3.1</a>), preprocessing directives (<a href="#6.10">6.10</a>), preprocessing numbers (<a href="#6.4.8">6.4.8</a>), string literals
3659 <p><small><a name="note69" href="#note69">69)</a> An additional category, placemarkers, is used internally in translation phase 4 (see <a href="#6.10.3.3">6.10.3.3</a>); it cannot
3660 occur in source files.
3661 </small>
3667 <pre>
3668 keyword: one of
3669 auto * if unsigned
3670 break inline void
3671 case int volatile
3672 char long while
3673 const register _Alignas
3674 continue restrict _Alignof
3675 default return _Atomic
3676 do short _Bool
3677 double signed _Complex
3678 else sizeof _Generic
3679 enum static _Imaginary
3680 extern struct _Noreturn
3681 float switch _Static_assert
3682 for typedef _Thread_local
3683 goto union
3684 </pre>
3688 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
3689 <!--page 77 -->
3693 <p><small><a name="note70" href="#note70">70)</a> One possible specification for imaginary types appears in <a href="#G">annex G</a>.
3694 </small>
3703 <pre>
3704 identifier:
3705 identifier-nondigit
3706 identifier identifier-nondigit
3707 identifier digit
3708 identifier-nondigit:
3709 nondigit
3710 universal-character-name
3711 other implementation-defined characters
3712 nondigit: one of
3713 _ a b c d e f g h i j k l m
3714 n o p q r s t u v w x y z
3715 A B C D E F G H I J K L M
3716 N O P Q R S T U V W X Y Z
3717 digit: one of
3718 0 1 2 3 4 5 6 7 8 9
3719 </pre>
3722 An identifier is a sequence of nondigit characters (including the underscore _, the
3723 lowercase and uppercase Latin letters, and other characters) and digits, which designates
3724 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
3725 There is no specific limit on the maximum length of an identifier.
3727 Each universal character name in an identifier shall designate a character whose encoding
3728 in ISO/IEC 10646 falls into one of the ranges specified in D.1.<sup><a href="#note71"><b>71)</b></a></sup> The initial character
3729 shall not be a universal character name designating a character whose encoding falls into
3730 one of the ranges specified in <a href="#D.2">D.2</a>. An implementation may allow multibyte characters
3731 that are not part of the basic source character set to appear in identifiers; which characters
3732 and their correspondence to universal character names is implementation-defined.
3736 <!--page 78 -->
3738 When preprocessing tokens are converted to tokens during translation phase 7, if a
3739 preprocessing token could be converted to either a keyword or an identifier, it is converted
3740 to a keyword.
3743 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
3744 characters in an identifier; the limit for an external name (an identifier that has external
3745 linkage) may be more restrictive than that for an internal name (a macro name or an
3746 identifier that does not have external linkage). The number of significant characters in an
3747 identifier is implementation-defined.
3749 Any identifiers that differ in a significant character are different identifiers. If two
3750 identifiers differ only in nonsignificant characters, the behavior is undefined.
3751 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), macro replacement (<a href="#6.10.3">6.10.3</a>).
3754 <p><small><a name="note71" href="#note71">71)</a> On systems in which linkers cannot accept extended characters, an encoding of the universal character
3755 name may be used in forming valid external identifiers. For example, some otherwise unused
3756 character or sequence of characters may be used to encode the \u in a universal character name.
3757 Extended characters may produce a long external identifier.
3758 </small>
3764 The identifier __func__ shall be implicitly declared by the translator as if,
3765 immediately following the opening brace of each function definition, the declaration
3766 <pre>
3767 static const char __func__[] = "function-name";
3768 </pre>
3769 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note72"><b>72)</b></a></sup>
3771 This name is encoded as if the implicit declaration had been written in the source
3772 character set and then translated into the execution character set as indicated in translation
3773 phase 5.
3775 EXAMPLE Consider the code fragment:
3776 <pre>
3778 void myfunc(void)
3779 {
3780 printf("%s\n", __func__);
3781 /* ... */
3782 }
3783 </pre>
3784 Each time the function is called, it will print to the standard output stream:
3785 <pre>
3786 myfunc
3787 </pre>
3794 <!--page 79 -->
3797 <p><small><a name="note72" href="#note72">72)</a> Since the name __func__ is reserved for any use by the implementation (<a href="#7.1.3">7.1.3</a>), if any other
3798 identifier is explicitly declared using the name __func__, the behavior is undefined.
3799 </small>
3805 <pre>
3806 universal-character-name:
3807 \u hex-quad
3808 \U hex-quad hex-quad
3809 hex-quad:
3810 hexadecimal-digit hexadecimal-digit
3811 hexadecimal-digit hexadecimal-digit
3812 </pre>
3815 A universal character name shall not specify a character whose short identifier is less than
3820 Universal character names may be used in identifiers, character constants, and string
3821 literals to designate characters that are not in the basic character set.
3824 The universal character name \Unnnnnnnn designates the character whose eight-digit
3825 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note74"><b>74)</b></a></sup> Similarly, the universal
3826 character name \unnnn designates the character whose four-digit short identifier is nnnn
3827 (and whose eight-digit short identifier is 0000nnnn).
3832 <!--page 80 -->
3835 <p><small><a name="note73" href="#note73">73)</a> The disallowed characters are the characters in the basic character set and the code positions reserved
3836 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
3837 UTF-16).
3839 </small>
3840 <p><small><a name="note74" href="#note74">74)</a> Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
3841 </small>
3847 <pre>
3848 constant:
3849 integer-constant
3850 floating-constant
3851 enumeration-constant
3852 character-constant
3853 </pre>
3856 Each constant shall have a type and the value of a constant shall be in the range of
3857 representable values for its type.
3860 Each constant has a type, determined by its form and value, as detailed later.
3866 <!--page 81 -->
3867 <pre>
3868 integer-constant:
3872 decimal-constant:
3873 nonzero-digit
3874 decimal-constant digit
3875 octal-constant:
3876 0
3877 octal-constant octal-digit
3878 hexadecimal-constant:
3879 hexadecimal-prefix hexadecimal-digit
3880 hexadecimal-constant hexadecimal-digit
3881 hexadecimal-prefix: one of
3883 nonzero-digit: one of
3884 1 2 3 4 5 6 7 8 9
3885 octal-digit: one of
3886 0 1 2 3 4 5 6 7
3887 hexadecimal-digit: one of
3888 0 1 2 3 4 5 6 7 8 9
3889 a b c d e f
3890 A B C D E F
3891 integer-suffix:
3893 unsigned-suffix long-long-suffix
3896 unsigned-suffix: one of
3897 u U
3898 long-suffix: one of
3899 l L
3900 long-long-suffix: one of
3901 ll LL
3902 </pre>
3905 An integer constant begins with a digit, but has no period or exponent part. It may have a
3906 prefix that specifies its base and a suffix that specifies its type.
3908 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3909 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3911 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3916 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3918 The type of an integer constant is the first of the corresponding list in which its value can
3919 be represented.
3920 <!--page 82 -->
3921 <pre>
3922 Octal or Hexadecimal
3923 </pre>
3924 Suffix Decimal Constant Constant
3926 none int int
3927 <pre>
3928 long int unsigned int
3929 long long int long int
3930 unsigned long int
3931 long long int
3932 unsigned long long int
3933 </pre>
3935 u or U unsigned int unsigned int
3936 <pre>
3937 unsigned long int unsigned long int
3938 unsigned long long int unsigned long long int
3939 </pre>
3941 l or L long int long int
3942 <pre>
3943 long long int unsigned long int
3944 long long int
3945 unsigned long long int
3946 </pre>
3948 Both u or U unsigned long int unsigned long int
3949 and l or L unsigned long long int unsigned long long int
3951 ll or LL long long int long long int
3952 <pre>
3953 unsigned long long int
3954 </pre>
3956 Both u or U unsigned long long int unsigned long long int
3957 and ll or LL
3959 If an integer constant cannot be represented by any type in its list, it may have an
3960 extended integer type, if the extended integer type can represent its value. If all of the
3961 types in the list for the constant are signed, the extended integer type shall be signed. If
3962 all of the types in the list for the constant are unsigned, the extended integer type shall be
3963 unsigned. If the list contains both signed and unsigned types, the extended integer type
3964 may be signed or unsigned. If an integer constant cannot be represented by any type in
3965 its list and has no extended integer type, then the integer constant has no type.
3966 <!--page 83 -->
3972 <!--page 84 -->
3973 <pre>
3974 floating-constant:
3975 decimal-floating-constant
3976 hexadecimal-floating-constant
3977 decimal-floating-constant:
3980 hexadecimal-floating-constant:
3981 hexadecimal-prefix hexadecimal-fractional-constant
3983 hexadecimal-prefix hexadecimal-digit-sequence
3985 fractional-constant:
3987 digit-sequence .
3988 exponent-part:
3991 sign: one of
3992 + -
3993 digit-sequence:
3994 digit
3995 digit-sequence digit
3996 hexadecimal-fractional-constant:
3998 hexadecimal-digit-sequence
3999 hexadecimal-digit-sequence .
4000 binary-exponent-part:
4003 hexadecimal-digit-sequence:
4004 hexadecimal-digit
4005 hexadecimal-digit-sequence hexadecimal-digit
4006 floating-suffix: one of
4007 f l F L
4008 </pre>
4011 A floating constant has a significand part that may be followed by an exponent part and a
4012 suffix that specifies its type. The components of the significand part may include a digit
4013 sequence representing the whole-number part, followed by a period (.), followed by a
4014 digit sequence representing the fraction part. The components of the exponent part are an
4015 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
4016 Either the whole-number part or the fraction part has to be present; for decimal floating
4017 constants, either the period or the exponent part has to be present.
4020 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
4021 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
4022 floating constants, the exponent indicates the power of 10 by which the significand part is
4023 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
4024 by which the significand part is to be scaled. For decimal floating constants, and also for
4025 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
4026 the nearest representable value, or the larger or smaller representable value immediately
4027 adjacent to the nearest representable value, chosen in an implementation-defined manner.
4028 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
4029 correctly rounded.
4031 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
4032 type float. If suffixed by the letter l or L, it has type long double.
4034 Floating constants are converted to internal format as if at translation-time. The
4035 conversion of a floating constant shall not raise an exceptional condition or a floating-
4036 point exception at execution time. All floating constants of the same source form<sup><a href="#note75"><b>75)</b></a></sup> shall
4037 convert to the same internal format with the same value.
4040 The implementation should produce a diagnostic message if a hexadecimal constant
4041 cannot be represented exactly in its evaluation format; the implementation should then
4042 proceed with the translation of the program.
4044 The translation-time conversion of floating constants should match the execution-time
4045 conversion of character strings by library functions, such as strtod, given matching
4046 inputs suitable for both conversions, the same result format, and default execution-time
4049 <!--page 85 -->
4052 <p><small><a name="note75" href="#note75">75)</a> <a href="#1.23">1.23</a>, 1.230, 123e-2, 123e-02, and 1.23L are all different source forms and thus need not
4053 convert to the same internal format and value.
4054 </small>
4055 <p><small><a name="note76" href="#note76">76)</a> The specification for the library functions recommends more accurate conversion than required for
4057 </small>
4063 <pre>
4064 enumeration-constant:
4065 identifier
4066 </pre>
4069 An identifier declared as an enumeration constant has type int.
4076 <!--page 86 -->
4077 <pre>
4078 character-constant:
4079 ' c-char-sequence '
4080 L' c-char-sequence '
4081 u' c-char-sequence '
4082 U' c-char-sequence '
4083 c-char-sequence:
4084 c-char
4085 c-char-sequence c-char
4086 c-char:
4087 any member of the source character set except
4088 the single-quote ', backslash \, or new-line character
4089 escape-sequence
4090 escape-sequence:
4091 simple-escape-sequence
4092 octal-escape-sequence
4093 hexadecimal-escape-sequence
4094 universal-character-name
4095 simple-escape-sequence: one of
4096 \' \" \? \\
4097 \a \b \f \n \r \t \v
4098 octal-escape-sequence:
4099 \ octal-digit
4100 \ octal-digit octal-digit
4101 \ octal-digit octal-digit octal-digit
4102 hexadecimal-escape-sequence:
4103 \x hexadecimal-digit
4104 hexadecimal-escape-sequence hexadecimal-digit
4105 </pre>
4106 <p><b>Description</b>
4107 <p><!--para 2 -->
4108 An integer character constant is a sequence of one or more multibyte characters enclosed
4109 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
4110 letter L, u, or U. With a few exceptions detailed later, the elements of the sequence are
4111 any members of the source character set; they are mapped in an implementation-defined
4112 manner to members of the execution character set.
4113 <p><!--para 3 -->
4114 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
4115 arbitrary integer values are representable according to the following table of escape
4116 sequences:
4117 <pre>
4118 single quote ' \'
4119 double quote " \"
4120 question mark ? \?
4121 backslash \ \\
4122 octal character \octal digits
4123 hexadecimal character \x hexadecimal digits
4124 </pre>
4126 The double-quote " and question-mark ? are representable either by themselves or by the
4127 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
4128 shall be represented, respectively, by the escape sequences \' and \\.
4130 The octal digits that follow the backslash in an octal escape sequence are taken to be part
4131 of the construction of a single character for an integer character constant or of a single
4132 wide character for a wide character constant. The numerical value of the octal integer so
4133 formed specifies the value of the desired character or wide character.
4135 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
4136 sequence are taken to be part of the construction of a single character for an integer
4137 character constant or of a single wide character for a wide character constant. The
4138 numerical value of the hexadecimal integer so formed specifies the value of the desired
4139 character or wide character.
4141 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
4142 constitute the escape sequence.
4144 In addition, characters not in the basic character set are representable by universal
4145 character names and certain nongraphic characters are representable by escape sequences
4146 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
4148 <!--page 87 -->
4151 The value of an octal or hexadecimal escape sequence shall be in the range of
4152 representable values for the corresponding type:
4153 <pre>
4154 Prefix Corresponding Type
4155 none unsigned char
4156 L the unsigned type corresponding to wchar_t
4157 u char16_t
4158 U char32_t
4159 </pre>
4162 An integer character constant has type int. The value of an integer character constant
4163 containing a single character that maps to a single-byte execution character is the
4164 numerical value of the representation of the mapped character interpreted as an integer.
4165 The value of an integer character constant containing more than one character (e.g.,
4166 'ab'), or containing a character or escape sequence that does not map to a single-byte
4167 execution character, is implementation-defined. If an integer character constant contains
4168 a single character or escape sequence, its value is the one that results when an object with
4169 type char whose value is that of the single character or escape sequence is converted to
4170 type int.
4172 A wide character constant prefixed by the letter L has type wchar_t, an integer type
4173 defined in the <a href="#7.19"><stddef.h></a> header; a wide character constant prefixed by the letter u or
4174 U has type char16_t or char32_t, respectively, unsigned integer types defined in the
4175 <a href="#7.28"><uchar.h></a> header. The value of a wide character constant containing a single
4176 multibyte character that maps to a single member of the extended execution character set
4177 is the wide character corresponding to that multibyte character, as defined by the
4178 mbtowc, mbrtoc16, or mbrtoc32 function as appropriate for its type, with an
4179 implementation-defined current locale. The value of a wide character constant containing
4180 more than one multibyte character or a single multibyte character that maps to multiple
4181 members of the extended execution character set, or containing a multibyte character or
4182 escape sequence not represented in the extended execution character set, is
4183 implementation-defined.
4188 EXAMPLE 2 Consider implementations that use two's complement representation for integers and eight
4189 bits for objects that have type char. In an implementation in which type char has the same range of
4190 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
4191 same range of values as unsigned char, the character constant '\xFF' has the value +255.
4196 <!--page 88 -->
4198 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
4199 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
4200 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
4201 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
4202 escape sequence is terminated after three octal digits. (The value of this two-character integer character
4203 constant is implementation-defined.)
4206 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
4207 L'\1234' specifies the implementation-defined value that results from the combination of the values
4210 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbtowc function
4211 (<a href="#7.22.7.2">7.22.7.2</a>), Unicode utilities <a href="#7.28"><uchar.h></a> (<a href="#7.28">7.28</a>).
4214 <p><small><a name="note77" href="#note77">77)</a> The semantics of these characters were discussed in <a href="#5.2.2">5.2.2</a>. If any other character follows a backslash,
4215 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
4216 </small>
4222 <pre>
4223 string-literal:
4225 encoding-prefix:
4226 u8
4227 u
4228 U
4229 L
4230 s-char-sequence:
4231 s-char
4232 s-char-sequence s-char
4233 s-char:
4234 any member of the source character set except
4235 the double-quote ", backslash \, or new-line character
4236 escape-sequence
4237 </pre>
4238 <p><b>Constraints</b>
4239 <p><!--para 2 -->
4240 A sequence of adjacent string literal tokens shall not include both a wide string literal and
4241 a UTF-8 string literal.
4242 <p><b>Description</b>
4243 <p><!--para 3 -->
4244 A character string literal is a sequence of zero or more multibyte characters enclosed in
4246 A wide string literal is the same, except prefixed by the letter L, u, or U.
4247 <p><!--para 4 -->
4248 The same considerations apply to each element of the sequence in a string literal as if it
4249 were in an integer character constant (for a character or UTF-8 string literal) or a wide
4250 character constant (for a wide string literal), except that the single-quote ' is
4251 representable either by itself or by the escape sequence \', but the double-quote " shall
4252 <!--page 89 -->
4253 be represented by the escape sequence \".
4254 <p><b>Semantics</b>
4255 <p><!--para 5 -->
4256 In translation phase 6, the multibyte character sequences specified by any sequence of
4257 adjacent character and identically-prefixed string literal tokens are concatenated into a
4258 single multibyte character sequence. If any of the tokens has an encoding prefix, the
4259 resulting multibyte character sequence is treated as having the same prefix; otherwise, it
4260 is treated as a character string literal. Whether differently-prefixed wide string literal
4261 tokens can be concatenated and, if so, the treatment of the resulting multibyte character
4262 sequence are implementation-defined.
4263 <p><!--para 6 -->
4264 In translation phase 7, a byte or code of value zero is appended to each multibyte
4265 character sequence that results from a string literal or literals.<sup><a href="#note78"><b>78)</b></a></sup> The multibyte character
4266 sequence is then used to initialize an array of static storage duration and length just
4267 sufficient to contain the sequence. For character string literals, the array elements have
4268 type char, and are initialized with the individual bytes of the multibyte character
4269 sequence. For UTF-8 string literals, the array elements have type char, and are
4270 initialized with the characters of the multibyte character sequence, as encoded in UTF-8.
4271 For wide string literals prefixed by the letter L, the array elements have type wchar_t
4272 and are initialized with the sequence of wide characters corresponding to the multibyte
4273 character sequence, as defined by the mbstowcs function with an implementation-
4274 defined current locale. For wide string literals prefixed by the letter u or U, the array
4275 elements have type char16_t or char32_t, respectively, and are initialized with the
4276 sequence of wide characters corresponding to the multibyte character sequence, as
4277 defined by successive calls to the mbrtoc16, or mbrtoc32 function as appropriate for
4278 its type, with an implementation-defined current locale. The value of a string literal
4279 containing a multibyte character or escape sequence not represented in the execution
4280 character set is implementation-defined.
4281 <p><!--para 7 -->
4282 It is unspecified whether these arrays are distinct provided their elements have the
4283 appropriate values. If the program attempts to modify such an array, the behavior is
4284 undefined.
4285 <p><!--para 8 -->
4286 EXAMPLE 1 This pair of adjacent character string literals
4287 <pre>
4289 </pre>
4290 produces a single character string literal containing the two characters whose values are '\x12' and '3',
4291 because escape sequences are converted into single members of the execution character set just prior to
4292 adjacent string literal concatenation.
4294 <p><!--para 9 -->
4295 EXAMPLE 2 Each of the sequences of adjacent string literal tokens
4299 <!--page 90 -->
4300 <pre>
4305 </pre>
4306 is equivalent to the string literal
4307 <pre>
4309 </pre>
4310 Likewise, each of the sequences
4311 <pre>
4316 </pre>
4317 is equivalent to
4318 <pre>
4320 </pre>
4322 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbstowcs
4323 function (<a href="#7.22.8.1">7.22.8.1</a>), Unicode utilities <a href="#7.28"><uchar.h></a> (<a href="#7.28">7.28</a>).
4325 <p><b>Footnotes</b>
4326 <p><small><a name="note78" href="#note78">78)</a> A string literal need not be a string (see <a href="#7.1.1">7.1.1</a>), because a null character may be embedded in it by a
4327 \0 escape sequence.
4328 </small>
4332 <p><b>Syntax</b>
4333 <p><!--para 1 -->
4334 <pre>
4335 punctuator: one of
4336 [ ] ( ) { } . ->
4337 ++ -- & * + - ~ !
4338 / % << >> < > <= >= == != ^ | && ||
4339 ? : ; ...
4340 = *= /= %= += -= <<= >>= &= ^= |=
4341 , # ##
4342 <: :> <% %> %: %:%:
4343 </pre>
4344 <p><b>Semantics</b>
4345 <p><!--para 2 -->
4346 A punctuator is a symbol that has independent syntactic and semantic significance.
4347 Depending on context, it may specify an operation to be performed (which in turn may
4348 yield a value or a function designator, produce a side effect, or some combination thereof)
4349 in which case it is known as an operator (other forms of operator also exist in some
4350 contexts). An operand is an entity on which an operator acts.
4351 <!--page 91 -->
4352 <p><!--para 3 -->
4354 <pre>
4355 <: :> <% %> %: %:%:
4356 </pre>
4357 behave, respectively, the same as the six tokens
4358 <pre>
4359 [ ] { } # ##
4360 </pre>
4362 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
4365 <p><b>Footnotes</b>
4366 <p><small><a name="note79" href="#note79">79)</a> These tokens are sometimes called ''digraphs''.
4367 </small>
4368 <p><small><a name="note80" href="#note80">80)</a> Thus [ and <: behave differently when ''stringized'' (see <a href="#6.10.3.2">6.10.3.2</a>), but can otherwise be freely
4369 interchanged.
4370 </small>
4374 <p><b>Syntax</b>
4375 <p><!--para 1 -->
4376 <pre>
4377 header-name:
4378 < h-char-sequence >
4380 h-char-sequence:
4381 h-char
4382 h-char-sequence h-char
4383 h-char:
4384 any member of the source character set except
4385 the new-line character and >
4386 q-char-sequence:
4387 q-char
4388 q-char-sequence q-char
4389 q-char:
4390 any member of the source character set except
4391 the new-line character and "
4392 </pre>
4395 The sequences in both forms of header names are mapped in an implementation-defined
4398 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
4399 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
4404 <!--page 92 -->
4405 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note81"><b>81)</b></a></sup> Header name
4406 preprocessing tokens are recognized only within #include preprocessing directives and
4407 in implementation-defined locations within #pragma directives.<sup><a href="#note82"><b>82)</b></a></sup>
4409 EXAMPLE The following sequence of characters:
4410 <pre>
4413 #define const.member@$
4414 </pre>
4415 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
4416 by a { on the left and a } on the right).
4417 <pre>
4420 {#}{define} {const}{.}{member}{@}{$}
4421 </pre>
4426 <p><small><a name="note81" href="#note81">81)</a> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
4427 </small>
4428 <p><small><a name="note82" href="#note82">82)</a> For an example of a header name preprocessing token used in a #pragma directive, see <a href="#6.10.9">6.10.9</a>.
4429 </small>
4435 <pre>
4436 pp-number:
4437 digit
4438 . digit
4439 pp-number digit
4440 pp-number identifier-nondigit
4441 pp-number e sign
4442 pp-number E sign
4443 pp-number p sign
4444 pp-number P sign
4445 pp-number .
4446 </pre>
4449 A preprocessing number begins with a digit optionally preceded by a period (.) and may
4450 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
4451 p+, p-, P+, or P-.
4453 Preprocessing number tokens lexically include all floating and integer constant tokens.
4456 A preprocessing number does not have type or a value; it acquires both after a successful
4457 conversion (as part of translation phase 7) to a floating constant token or an integer
4458 constant token.
4461 <!--page 93 -->
4466 Except within a character constant, a string literal, or a comment, the characters /*
4467 introduce a comment. The contents of such a comment are examined only to identify
4468 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note83"><b>83)</b></a></sup>
4470 Except within a character constant, a string literal, or a comment, the characters //
4471 introduce a comment that includes all multibyte characters up to, but not including, the
4472 next new-line character. The contents of such a comment are examined only to identify
4473 multibyte characters and to find the terminating new-line character.
4475 EXAMPLE
4476 <pre>
4477 "a//b" // four-character string literal
4478 #include "//e" // undefined behavior
4479 // */ // comment, not syntax error
4480 f = g/**//h; // equivalent to f = g / h;
4481 //\
4482 i(); // part of a two-line comment
4483 /\
4484 / j(); // part of a two-line comment
4485 #define glue(x,y) x##y
4486 glue(/,/) k(); // syntax error, not comment
4487 /*//*/ l(); // equivalent to l();
4488 m = n//**/o
4489 + p; // equivalent to m = n + p;
4490 </pre>
4495 <!--page 94 -->
4499 </small>
4504 An expression is a sequence of operators and operands that specifies computation of a
4505 value, or that designates an object or a function, or that generates side effects, or that
4506 performs a combination thereof. The value computations of the operands of an operator
4507 are sequenced before the value computation of the result of the operator.
4509 If a side effect on a scalar object is unsequenced relative to either a different side effect
4510 on the same scalar object or a value computation using the value of the same scalar
4511 object, the behavior is undefined. If there are multiple allowable orderings of the
4512 subexpressions of an expression, the behavior is undefined if such an unsequenced side
4515 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note85"><b>85)</b></a></sup> Except as specified
4516 later, side effects and value computations of subexpressions are unsequenced.<sup><a href="#note86"><b>86)</b></a></sup>
4518 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
4519 collectively described as bitwise operators) are required to have operands that have
4520 integer type. These operators yield values that depend on the internal representations of
4521 integers, and have implementation-defined and undefined aspects for signed types.
4523 If an exceptional condition occurs during the evaluation of an expression (that is, if the
4524 result is not mathematically defined or not in the range of representable values for its
4525 type), the behavior is undefined.
4529 <!--page 95 -->
4531 The effective type of an object for an access to its stored value is the declared type of the
4532 object, if any.<sup><a href="#note87"><b>87)</b></a></sup> If a value is stored into an object having no declared type through an
4533 lvalue having a type that is not a character type, then the type of the lvalue becomes the
4534 effective type of the object for that access and for subsequent accesses that do not modify
4535 the stored value. If a value is copied into an object having no declared type using
4536 memcpy or memmove, or is copied as an array of character type, then the effective type
4537 of the modified object for that access and for subsequent accesses that do not modify the
4538 value is the effective type of the object from which the value is copied, if it has one. For
4539 all other accesses to an object having no declared type, the effective type of the object is
4540 simply the type of the lvalue used for the access.
4542 An object shall have its stored value accessed only by an lvalue expression that has one of
4544 <ul>
4545 <li> a type compatible with the effective type of the object,
4546 <li> a qualified version of a type compatible with the effective type of the object,
4547 <li> a type that is the signed or unsigned type corresponding to the effective type of the
4548 object,
4549 <li> a type that is the signed or unsigned type corresponding to a qualified version of the
4550 effective type of the object,
4551 <li> an aggregate or union type that includes one of the aforementioned types among its
4552 members (including, recursively, a member of a subaggregate or contained union), or
4553 <li> a character type.
4554 </ul>
4556 A floating expression may be contracted, that is, evaluated as though it were a single
4557 operation, thereby omitting rounding errors implied by the source code and the
4558 expression evaluation method.<sup><a href="#note89"><b>89)</b></a></sup> The FP_CONTRACT pragma in <a href="#7.12"><math.h></a> provides a
4559 way to disallow contracted expressions. Otherwise, whether and how expressions are
4561 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), copying functions (<a href="#7.24.2">7.24.2</a>).
4564 <!--page 96 -->
4567 <p><small><a name="note84" href="#note84">84)</a> This paragraph renders undefined statement expressions such as
4569 <pre>
4570 i = ++i + 1;
4571 a[i++] = i;
4572 </pre>
4573 while allowing
4575 <pre>
4576 i = i + 1;
4577 a[i] = i;
4578 </pre>
4580 </small>
4581 <p><small><a name="note85" href="#note85">85)</a> The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
4582 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
4583 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
4584 <a href="#6.5.1">6.5.1</a> through <a href="#6.5.6">6.5.6</a>. The exceptions are cast expressions (<a href="#6.5.4">6.5.4</a>) as operands of unary operators
4585 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
4586 parentheses () (<a href="#6.5.1">6.5.1</a>), subscripting brackets [] (<a href="#6.5.2.1">6.5.2.1</a>), function-call parentheses () (<a href="#6.5.2.2">6.5.2.2</a>), and
4588 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
4589 indicated in each subclause by the syntax for the expressions discussed therein.
4590 </small>
4591 <p><small><a name="note86" href="#note86">86)</a> In an expression that is evaluated more than once during the execution of a program, unsequenced and
4592 indeterminately sequenced evaluations of its subexpressions need not be performed consistently in
4593 different evaluations.
4594 </small>
4596 </small>
4597 <p><small><a name="note88" href="#note88">88)</a> The intent of this list is to specify those circumstances in which an object may or may not be aliased.
4598 </small>
4599 <p><small><a name="note89" href="#note89">89)</a> The intermediate operations in the contracted expression are evaluated as if to infinite range and
4600 precision, while the final operation is rounded to the format determined by the expression evaluation
4601 method. A contracted expression might also omit the raising of floating-point exceptions.
4602 </small>
4603 <p><small><a name="note90" href="#note90">90)</a> This license is specifically intended to allow implementations to exploit fast machine instructions that
4604 combine multiple C operators. As contractions potentially undermine predictability, and can even
4605 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
4606 documented.
4607 </small>
4613 <pre>
4614 primary-expression:
4615 identifier
4616 constant
4617 string-literal
4618 ( expression )
4619 generic-selection
4620 </pre>
4623 An identifier is a primary expression, provided it has been declared as designating an
4624 object (in which case it is an lvalue) or a function (in which case it is a function
4627 A constant is a primary expression. Its type depends on its form and value, as detailed in
4630 A string literal is a primary expression. It is an lvalue with type as detailed in <a href="#6.4.5">6.4.5</a>.
4632 A parenthesized expression is a primary expression. Its type and value are identical to
4633 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
4634 expression if the unparenthesized expression is, respectively, an lvalue, a function
4635 designator, or a void expression.
4637 A generic selection is a primary expression. Its type and value depend on the selected
4638 generic association, as detailed in the following subclause.
4642 <p><small><a name="note91" href="#note91">91)</a> Thus, an undeclared identifier is a violation of the syntax.
4643 </small>
4649 <pre>
4650 generic-selection:
4651 _Generic ( assignment-expression , generic-assoc-list )
4652 generic-assoc-list:
4653 generic-association
4654 generic-assoc-list , generic-association
4655 generic-association:
4656 type-name : assignment-expression
4657 default : assignment-expression
4658 </pre>
4662 <!--page 97 -->
4665 A generic selection shall have no more than one default generic association. The type
4666 name in a generic association shall specify a complete object type other than a variably
4667 modified type. No two generic associations in the same generic selection shall specify
4668 compatible types. The controlling expression of a generic selection shall have type
4669 compatible with at most one of the types named in its generic association list. If a
4670 generic selection has no default generic association, its controlling expression shall
4671 have type compatible with exactly one of the types named in its generic association list.
4674 The controlling expression of a generic selection is not evaluated. If a generic selection
4675 has a generic association with a type name that is compatible with the type of the
4676 controlling expression, then the result expression of the generic selection is the
4677 expression in that generic association. Otherwise, the result expression of the generic
4678 selection is the expression in the default generic association. None of the expressions
4679 from any other generic association of the generic selection is evaluated.
4681 The type and value of a generic selection are identical to those of its result expression. It
4682 is an lvalue, a function designator, or a void expression if its result expression is,
4683 respectively, an lvalue, a function designator, or a void expression.
4685 EXAMPLE The cbrt type-generic macro could be implemented as follows:
4686 <pre>
4687 #define cbrt(X) _Generic((X), \
4688 long double: cbrtl, \
4689 default: cbrt, \
4690 float: cbrtf \
4691 )(X)
4692 </pre>
4699 <!--page 98 -->
4700 <pre>
4701 postfix-expression:
4702 primary-expression
4703 postfix-expression [ expression ]
4705 postfix-expression . identifier
4706 postfix-expression -> identifier
4707 postfix-expression ++
4708 postfix-expression --
4709 ( type-name ) { initializer-list }
4710 ( type-name ) { initializer-list , }
4711 argument-expression-list:
4712 assignment-expression
4713 argument-expression-list , assignment-expression
4714 </pre>
4720 One of the expressions shall have type ''pointer to complete object type'', the other
4721 expression shall have integer type, and the result has type ''type''.
4724 A postfix expression followed by an expression in square brackets [] is a subscripted
4725 designation of an element of an array object. The definition of the subscript operator []
4726 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
4727 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
4728 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
4729 element of E1 (counting from zero).
4731 Successive subscript operators designate an element of a multidimensional array object.
4733 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
4734 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
4735 implicitly as a result of subscripting, the result is the referenced (n - 1)-dimensional
4736 array, which itself is converted into a pointer if used as other than an lvalue. It follows
4737 from this that arrays are stored in row-major order (last subscript varies fastest).
4739 EXAMPLE Consider the array object defined by the declaration
4740 <pre>
4742 </pre>
4743 Here x is a 3 x 5 array of ints; more precisely, x is an array of three element objects, each of which is an
4744 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
4745 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
4746 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
4747 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
4748 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
4749 yields an int.
4751 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
4753 <!--page 99 -->
4759 The expression that denotes the called function<sup><a href="#note92"><b>92)</b></a></sup> shall have type pointer to function
4760 returning void or returning a complete object type other than an array type.
4762 If the expression that denotes the called function has a type that includes a prototype, the
4763 number of arguments shall agree with the number of parameters. Each argument shall
4764 have a type such that its value may be assigned to an object with the unqualified version
4765 of the type of its corresponding parameter.
4768 A postfix expression followed by parentheses () containing a possibly empty, comma-
4769 separated list of expressions is a function call. The postfix expression denotes the called
4770 function. The list of expressions specifies the arguments to the function.
4772 An argument may be an expression of any complete object type. In preparing for the call
4773 to a function, the arguments are evaluated, and each parameter is assigned the value of the
4776 If the expression that denotes the called function has type pointer to function returning an
4777 object type, the function call expression has the same type as that object type, and has the
4778 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void.
4780 If the expression that denotes the called function has a type that does not include a
4781 prototype, the integer promotions are performed on each argument, and arguments that
4782 have type float are promoted to double. These are called the default argument
4783 promotions. If the number of arguments does not equal the number of parameters, the
4784 behavior is undefined. If the function is defined with a type that includes a prototype, and
4785 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
4786 promotion are not compatible with the types of the parameters, the behavior is undefined.
4787 If the function is defined with a type that does not include a prototype, and the types of
4788 the arguments after promotion are not compatible with those of the parameters after
4789 promotion, the behavior is undefined, except for the following cases:
4790 <ul>
4791 <li> one promoted type is a signed integer type, the other promoted type is the
4792 corresponding unsigned integer type, and the value is representable in both types;
4796 <!--page 100 -->
4797 <li> both types are pointers to qualified or unqualified versions of a character type or
4798 void.
4799 </ul>
4801 If the expression that denotes the called function has a type that does include a prototype,
4802 the arguments are implicitly converted, as if by assignment, to the types of the
4803 corresponding parameters, taking the type of each parameter to be the unqualified version
4804 of its declared type. The ellipsis notation in a function prototype declarator causes
4805 argument type conversion to stop after the last declared parameter. The default argument
4806 promotions are performed on trailing arguments.
4808 No other conversions are performed implicitly; in particular, the number and types of
4809 arguments are not compared with those of the parameters in a function definition that
4810 does not include a function prototype declarator.
4812 If the function is defined with a type that is not compatible with the type (of the
4813 expression) pointed to by the expression that denotes the called function, the behavior is
4814 undefined.
4816 There is a sequence point after the evaluations of the function designator and the actual
4817 arguments but before the actual call. Every evaluation in the calling function (including
4818 other function calls) that is not otherwise specifically sequenced before or after the
4819 execution of the body of the called function is indeterminately sequenced with respect to
4822 Recursive function calls shall be permitted, both directly and indirectly through any chain
4823 of other functions.
4825 EXAMPLE In the function call
4826 <pre>
4827 (*pf[f1()]) (f2(), f3() + f4())
4828 </pre>
4829 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
4830 the function pointed to by pf[f1()] is called.
4832 <p><b> Forward references</b>: function declarators (including prototypes) (<a href="#6.7.6.3">6.7.6.3</a>), function
4833 definitions (<a href="#6.9.1">6.9.1</a>), the return statement (<a href="#6.8.6.4">6.8.6.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
4836 <p><small><a name="note92" href="#note92">92)</a> Most often, this is the result of converting an identifier that is a function designator.
4837 </small>
4838 <p><small><a name="note93" href="#note93">93)</a> A function may change the values of its parameters, but these changes cannot affect the values of the
4839 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
4840 change the value of the object pointed to. A parameter declared to have array or function type is
4842 </small>
4843 <p><small><a name="note94" href="#note94">94)</a> In other words, function executions do not ''interleave'' with each other.
4844 </small>
4850 The first operand of the . operator shall have an atomic, qualified, or unqualified
4851 structure or union type, and the second operand shall name a member of that type.
4853 The first operand of the -> operator shall have type ''pointer to atomic, qualified, or
4854 unqualified structure'' or ''pointer to atomic, qualified, or unqualified union'', and the
4855 second operand shall name a member of the type pointed to.
4858 <!--page 101 -->
4861 A postfix expression followed by the . operator and an identifier designates a member of
4862 a structure or union object. The value is that of the named member,<sup><a href="#note95"><b>95)</b></a></sup> and is an lvalue if
4863 the first expression is an lvalue. If the first expression has qualified type, the result has
4864 the so-qualified version of the type of the designated member.
4866 A postfix expression followed by the -> operator and an identifier designates a member
4867 of a structure or union object. The value is that of the named member of the object to
4868 which the first expression points, and is an lvalue.<sup><a href="#note96"><b>96)</b></a></sup> If the first expression is a pointer to
4869 a qualified type, the result has the so-qualified version of the type of the designated
4870 member.
4872 Accessing a member of an atomic structure or union object results in undefined
4875 One special guarantee is made in order to simplify the use of unions: if a union contains
4876 several structures that share a common initial sequence (see below), and if the union
4877 object currently contains one of these structures, it is permitted to inspect the common
4878 initial part of any of them anywhere that a declaration of the completed type of the union
4879 is visible. Two structures share a common initial sequence if corresponding members
4880 have compatible types (and, for bit-fields, the same widths) for a sequence of one or more
4881 initial members.
4883 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
4884 union, f().x is a valid postfix expression but is not an lvalue.
4887 EXAMPLE 2 In:
4888 <pre>
4889 struct s { int i; const int ci; };
4890 struct s s;
4891 const struct s cs;
4892 volatile struct s vs;
4893 </pre>
4894 the various members have the types:
4899 <!--page 102 -->
4900 <pre>
4901 s.i int
4902 s.ci const int
4903 cs.i const int
4904 cs.ci const int
4905 vs.i volatile int
4906 vs.ci volatile const int
4907 </pre>
4910 EXAMPLE 3 The following is a valid fragment:
4911 <pre>
4912 union {
4913 struct {
4914 int alltypes;
4915 } n;
4916 struct {
4917 int type;
4918 int intnode;
4919 } ni;
4920 struct {
4921 int type;
4922 double doublenode;
4923 } nf;
4924 } u;
4925 u.nf.type = 1;
4927 /* ... */
4928 if (u.n.alltypes == 1)
4929 if (sin(u.nf.doublenode) == 0.0)
4930 /* ... */
4931 </pre>
4932 The following is not a valid fragment (because the union type is not visible within function f):
4933 <pre>
4934 struct t1 { int m; };
4935 struct t2 { int m; };
4936 int f(struct t1 *p1, struct t2 *p2)
4937 {
4940 return p1->m;
4941 }
4942 int g()
4943 {
4944 union {
4945 struct t1 s1;
4946 struct t2 s2;
4947 } u;
4948 /* ... */
4950 }
4951 </pre>
4953 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
4955 <!--page 103 -->
4958 <p><small><a name="note95" href="#note95">95)</a> If the member used to read the contents of a union object is not the same as the member last used to
4959 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
4960 as an object representation in the new type as described in <a href="#6.2.6">6.2.6</a> (a process sometimes called ''type
4961 punning''). This might be a trap representation.
4962 </small>
4963 <p><small><a name="note96" href="#note96">96)</a> If &E is a valid pointer expression (where & is the ''address-of '' operator, which generates a pointer to
4965 </small>
4966 <p><small><a name="note97" href="#note97">97)</a> For example, a data race would occur if access to the entire structure or union in one thread conflicts
4967 with access to a member from another thread, where at least one access is a modification. Members
4968 can be safely accessed using a non-atomic object which is assigned to or from the atomic object.
4969 </small>
4972 <h5><a name="6.5.2.4" href="#6.5.2.4">6.5.2.4 Postfix increment and decrement operators</a></h5>
4975 The operand of the postfix increment or decrement operator shall have atomic, qualified,
4976 or unqualified real or pointer type, and shall be a modifiable lvalue.
4979 The result of the postfix ++ operator is the value of the operand. As a side effect, the
4980 value of the operand object is incremented (that is, the value 1 of the appropriate type is
4981 added to it). See the discussions of additive operators and compound assignment for
4982 information on constraints, types, and conversions and the effects of operations on
4983 pointers. The value computation of the result is sequenced before the side effect of
4984 updating the stored value of the operand. With respect to an indeterminately-sequenced
4985 function call, the operation of postfix ++ is a single evaluation. Postfix ++ on an object
4986 with atomic type is a read-modify-write operation with memory_order_seq_cst
4989 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
4990 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
4991 it).
4992 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
4995 <p><small><a name="note98" href="#note98">98)</a> Where a pointer to an atomic object can be formed and E has integer type, E++ is equivalent to the
4996 following code sequence where T is the type of E:
4998 <pre>
4999 T *addr = &E;
5000 T old = *addr;
5001 T new;
5002 do {
5003 new = old + 1;
5004 } while (!atomic_compare_exchange_strong(addr, &old, new));
5005 </pre>
5006 with old being the result of the operation.
5008 </small>
5014 The type name shall specify a complete object type or an array of unknown size, but not a
5015 variable length array type.
5017 All the constraints for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.
5020 A postfix expression that consists of a parenthesized type name followed by a brace-
5021 enclosed list of initializers is a compound literal. It provides an unnamed object whose
5023 <!--page 104 -->
5026 If the type name specifies an array of unknown size, the size is determined by the
5027 initializer list as specified in <a href="#6.7.9">6.7.9</a>, and the type of the compound literal is that of the
5028 completed array type. Otherwise (when the type name specifies an object type), the type
5029 of the compound literal is that specified by the type name. In either case, the result is an
5030 lvalue.
5032 The value of the compound literal is that of an unnamed object initialized by the
5033 initializer list. If the compound literal occurs outside the body of a function, the object
5034 has static storage duration; otherwise, it has automatic storage duration associated with
5035 the enclosing block.
5037 All the semantic rules for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.<sup><a href="#note100"><b>100)</b></a></sup>
5039 String literals, and compound literals with const-qualified types, need not designate
5042 EXAMPLE 1 The file scope definition
5043 <pre>
5045 </pre>
5046 initializes p to point to the first element of an array of two ints, the first having the value two and the
5047 second, four. The expressions in this compound literal are required to be constant. The unnamed object
5048 has static storage duration.
5051 EXAMPLE 2 In contrast, in
5052 <pre>
5053 void f(void)
5054 {
5055 int *p;
5056 /*...*/
5057 p = (int [2]){*p};
5058 /*...*/
5059 }
5060 </pre>
5061 p is assigned the address of the first element of an array of two ints, the first having the value previously
5062 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
5063 unnamed object has automatic storage duration.
5066 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
5067 created using compound literals can be passed to functions without depending on member order:
5068 <pre>
5071 </pre>
5075 <!--page 105 -->
5076 Or, if drawline instead expected pointers to struct point:
5077 <pre>
5080 </pre>
5083 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
5084 <pre>
5086 </pre>
5089 EXAMPLE 5 The following three expressions have different meanings:
5090 <pre>
5091 "/tmp/fileXXXXXX"
5092 (char []){"/tmp/fileXXXXXX"}
5093 (const char []){"/tmp/fileXXXXXX"}
5094 </pre>
5095 The first always has static storage duration and has type array of char, but need not be modifiable; the last
5096 two have automatic storage duration when they occur within the body of a function, and the first of these
5097 two is modifiable.
5100 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
5101 and can even be shared. For example,
5102 <pre>
5104 </pre>
5105 might yield 1 if the literals' storage is shared.
5108 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
5109 linked object. For example, there is no way to write a self-referential compound literal that could be used
5110 as the function argument in place of the named object endless_zeros below:
5111 <pre>
5112 struct int_list { int car; struct int_list *cdr; };
5114 eval(endless_zeros);
5115 </pre>
5118 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
5119 <pre>
5120 struct s { int i; };
5121 int f (void)
5122 {
5123 struct s *p = 0, *q;
5124 int j = 0;
5125 again:
5126 q = p, p = &((struct s){ j++ });
5129 }
5130 </pre>
5131 The function f() always returns the value 1.
5133 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
5134 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
5135 have an indeterminate value, which would result in undefined behavior.
5137 <p><b> Forward references</b>: type names (<a href="#6.7.7">6.7.7</a>), initialization (<a href="#6.7.9">6.7.9</a>).
5138 <!--page 106 -->
5141 <p><small><a name="note99" href="#note99">99)</a> Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
5142 or void only, and the result of a cast expression is not an lvalue.
5143 </small>
5144 <p><small><a name="note100" href="#note100">100)</a> For example, subobjects without explicit initializers are initialized to zero.
5145 </small>
5146 <p><small><a name="note101" href="#note101">101)</a> This allows implementations to share storage for string literals and constant compound literals with
5147 the same or overlapping representations.
5148 </small>
5154 <pre>
5155 unary-expression:
5156 postfix-expression
5157 ++ unary-expression
5158 -- unary-expression
5159 unary-operator cast-expression
5160 sizeof unary-expression
5161 sizeof ( type-name )
5162 _Alignof ( type-name )
5163 unary-operator: one of
5164 & * + - ~ !
5165 </pre>
5168 <h5><a name="6.5.3.1" href="#6.5.3.1">6.5.3.1 Prefix increment and decrement operators</a></h5>
5171 The operand of the prefix increment or decrement operator shall have atomic, qualified,
5172 or unqualified real or pointer type, and shall be a modifiable lvalue.
5175 The value of the operand of the prefix ++ operator is incremented. The result is the new
5176 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
5177 See the discussions of additive operators and compound assignment for information on
5178 constraints, types, side effects, and conversions and the effects of operations on pointers.
5180 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
5181 operand is decremented.
5182 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
5188 The operand of the unary & operator shall be either a function designator, the result of a
5189 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
5190 not declared with the register storage-class specifier.
5192 The operand of the unary * operator shall have pointer type.
5195 The unary & operator yields the address of its operand. If the operand has type ''type'',
5196 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
5197 neither that operator nor the & operator is evaluated and the result is as if both were
5198 omitted, except that the constraints on the operators still apply and the result is not an
5199 <!--page 107 -->
5200 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
5201 the unary * that is implied by the [] is evaluated and the result is as if the & operator
5202 were removed and the [] operator were changed to a + operator. Otherwise, the result is
5203 a pointer to the object or function designated by its operand.
5205 The unary * operator denotes indirection. If the operand points to a function, the result is
5206 a function designator; if it points to an object, the result is an lvalue designating the
5207 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
5208 invalid value has been assigned to the pointer, the behavior of the unary * operator is
5210 <p><b> Forward references</b>: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
5214 <p><small><a name="note102" href="#note102">102)</a> Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is
5215 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
5216 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
5217 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
5218 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
5219 address inappropriately aligned for the type of object pointed to, and the address of an object after the
5220 end of its lifetime.
5221 </small>
5227 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
5228 integer type; of the ! operator, scalar type.
5231 The result of the unary + operator is the value of its (promoted) operand. The integer
5232 promotions are performed on the operand, and the result has the promoted type.
5234 The result of the unary - operator is the negative of its (promoted) operand. The integer
5235 promotions are performed on the operand, and the result has the promoted type.
5237 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
5238 each bit in the result is set if and only if the corresponding bit in the converted operand is
5239 not set). The integer promotions are performed on the operand, and the result has the
5240 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
5241 to the maximum value representable in that type minus E.
5243 The result of the logical negation operator ! is 0 if the value of its operand compares
5245 The expression !E is equivalent to (0==E).
5249 <!--page 108 -->
5255 The sizeof operator shall not be applied to an expression that has function type or an
5256 incomplete type, to the parenthesized name of such a type, or to an expression that
5257 designates a bit-field member. The _Alignof operator shall not be applied to a
5258 function type or an incomplete type.
5261 The sizeof operator yields the size (in bytes) of its operand, which may be an
5262 expression or the parenthesized name of a type. The size is determined from the type of
5263 the operand. The result is an integer. If the type of the operand is a variable length array
5264 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
5265 integer constant.
5267 The _Alignof operator yields the alignment requirement of its operand type. The
5268 operand is not evaluated and the result is an integer constant. When applied to an array
5269 type, the result is the alignment requirement of the element type.
5271 When sizeof is applied to an operand that has type char, unsigned char, or
5272 signed char, (or a qualified version thereof) the result is 1. When applied to an
5273 operand that has array type, the result is the total number of bytes in the array.<sup><a href="#note103"><b>103)</b></a></sup> When
5274 applied to an operand that has structure or union type, the result is the total number of
5275 bytes in such an object, including internal and trailing padding.
5277 The value of the result of both operators is implementation-defined, and its type (an
5278 unsigned integer type) is size_t, defined in <a href="#7.19"><stddef.h></a> (and other headers).
5280 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
5281 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
5282 allocate and return a pointer to void. For example:
5283 <pre>
5284 extern void *alloc(size_t);
5285 double *dp = alloc(sizeof *dp);
5286 </pre>
5287 The implementation of the alloc function should ensure that its return value is aligned suitably for
5288 conversion to a pointer to double.
5291 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
5292 <pre>
5293 sizeof array / sizeof array[0]
5294 </pre>
5297 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
5298 function:
5299 <pre>
5301 </pre>
5305 <!--page 109 -->
5306 <pre>
5307 size_t fsize3(int n)
5308 {
5309 char b[n+3]; // variable length array
5310 return sizeof b; // execution time sizeof
5311 }
5312 int main()
5313 {
5314 size_t size;
5316 return 0;
5317 }
5318 </pre>
5320 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), declarations (<a href="#6.7">6.7</a>),
5321 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), type names (<a href="#6.7.7">6.7.7</a>), array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
5324 <p><small><a name="note103" href="#note103">103)</a> When applied to a parameter declared to have array or function type, the sizeof operator yields the
5326 </small>
5332 <pre>
5333 cast-expression:
5334 unary-expression
5335 ( type-name ) cast-expression
5336 </pre>
5339 Unless the type name specifies a void type, the type name shall specify atomic, qualified,
5340 or unqualified scalar type, and the operand shall have scalar type.
5342 Conversions that involve pointers, other than where permitted by the constraints of
5345 A pointer type shall not be converted to any floating type. A floating type shall not be
5346 converted to any pointer type.
5349 Preceding an expression by a parenthesized type name converts the value of the
5350 expression to the named type. This construction is called a cast.<sup><a href="#note104"><b>104)</b></a></sup> A cast that specifies
5351 no conversion has no effect on the type or value of an expression.
5353 If the value of the expression is represented with greater range or precision than required
5354 by the type named by the cast (<a href="#6.3.1.8">6.3.1.8</a>), then the cast specifies a conversion even if the
5355 type of the expression is the same as the named type and removes any extra range and
5356 precision.
5357 <p><b> Forward references</b>: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
5358 prototypes) (<a href="#6.7.6.3">6.7.6.3</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>), type names (<a href="#6.7.7">6.7.7</a>).
5360 <!--page 110 -->
5363 <p><small><a name="note104" href="#note104">104)</a> A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
5364 unqualified version of the type.
5365 </small>
5371 <pre>
5372 multiplicative-expression:
5373 cast-expression
5374 multiplicative-expression * cast-expression
5375 multiplicative-expression / cast-expression
5376 multiplicative-expression % cast-expression
5377 </pre>
5380 Each of the operands shall have arithmetic type. The operands of the % operator shall
5381 have integer type.
5384 The usual arithmetic conversions are performed on the operands.
5386 The result of the binary * operator is the product of the operands.
5388 The result of the / operator is the quotient from the division of the first operand by the
5389 second; the result of the % operator is the remainder. In both operations, if the value of
5390 the second operand is zero, the behavior is undefined.
5392 When integers are divided, the result of the / operator is the algebraic quotient with any
5393 fractional part discarded.<sup><a href="#note105"><b>105)</b></a></sup> If the quotient a/b is representable, the expression
5394 (a/b)*b + a%b shall equal a; otherwise, the behavior of both a/b and a%b is
5395 undefined.
5398 <p><small><a name="note105" href="#note105">105)</a> This is often called ''truncation toward zero''.
5399 </small>
5405 <pre>
5406 additive-expression:
5407 multiplicative-expression
5408 additive-expression + multiplicative-expression
5409 additive-expression - multiplicative-expression
5410 </pre>
5413 For addition, either both operands shall have arithmetic type, or one operand shall be a
5414 pointer to a complete object type and the other shall have integer type. (Incrementing is
5415 equivalent to adding 1.)
5417 For subtraction, one of the following shall hold:
5422 <!--page 111 -->
5423 <ul>
5424 <li> both operands have arithmetic type;
5425 <li> both operands are pointers to qualified or unqualified versions of compatible complete
5426 object types; or
5427 <li> the left operand is a pointer to a complete object type and the right operand has
5428 integer type.
5429 </ul>
5430 (Decrementing is equivalent to subtracting 1.)
5433 If both operands have arithmetic type, the usual arithmetic conversions are performed on
5434 them.
5436 The result of the binary + operator is the sum of the operands.
5438 The result of the binary - operator is the difference resulting from the subtraction of the
5439 second operand from the first.
5441 For the purposes of these operators, a pointer to an object that is not an element of an
5442 array behaves the same as a pointer to the first element of an array of length one with the
5443 type of the object as its element type.
5445 When an expression that has integer type is added to or subtracted from a pointer, the
5446 result has the type of the pointer operand. If the pointer operand points to an element of
5447 an array object, and the array is large enough, the result points to an element offset from
5448 the original element such that the difference of the subscripts of the resulting and original
5449 array elements equals the integer expression. In other words, if the expression P points to
5450 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
5451 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
5452 the array object, provided they exist. Moreover, if the expression P points to the last
5453 element of an array object, the expression (P)+1 points one past the last element of the
5454 array object, and if the expression Q points one past the last element of an array object,
5455 the expression (Q)-1 points to the last element of the array object. If both the pointer
5456 operand and the result point to elements of the same array object, or one past the last
5457 element of the array object, the evaluation shall not produce an overflow; otherwise, the
5458 behavior is undefined. If the result points one past the last element of the array object, it
5459 shall not be used as the operand of a unary * operator that is evaluated.
5461 When two pointers are subtracted, both shall point to elements of the same array object,
5462 or one past the last element of the array object; the result is the difference of the
5463 subscripts of the two array elements. The size of the result is implementation-defined,
5464 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.19"><stddef.h></a> header.
5465 If the result is not representable in an object of that type, the behavior is undefined. In
5466 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
5467 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
5468 <!--page 112 -->
5469 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
5470 an array object or one past the last element of an array object, and the expression Q points
5471 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
5473 expression P points one past the last element of the array object, even though the
5474 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note106"><b>106)</b></a></sup>
5476 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
5477 <pre>
5478 {
5480 int a[n][m];
5484 n = p - a; // n == 1
5485 }
5486 </pre>
5488 If array a in the above example were declared to be an array of known constant size, and pointer p were
5489 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
5490 the same.
5492 <p><b> Forward references</b>: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), common definitions <a href="#7.19"><stddef.h></a>
5496 <p><small><a name="note106" href="#note106">106)</a> Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In
5497 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
5498 by the size of the object originally pointed to, and the resulting pointer is converted back to the
5499 original type. For pointer subtraction, the result of the difference between the character pointers is
5500 similarly divided by the size of the object originally pointed to.
5501 When viewed in this way, an implementation need only provide one extra byte (which may overlap
5502 another object in the program) just after the end of the object in order to satisfy the ''one past the last
5503 element'' requirements.
5504 </small>
5510 <pre>
5511 shift-expression:
5512 additive-expression
5513 shift-expression << additive-expression
5514 shift-expression >> additive-expression
5515 </pre>
5518 Each of the operands shall have integer type.
5521 The integer promotions are performed on each of the operands. The type of the result is
5522 that of the promoted left operand. If the value of the right operand is negative or is
5524 <!--page 113 -->
5525 greater than or equal to the width of the promoted left operand, the behavior is undefined.
5527 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
5528 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
5529 one more than the maximum value representable in the result type. If E1 has a signed
5530 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
5531 the resulting value; otherwise, the behavior is undefined.
5533 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
5534 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
5535 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
5536 resulting value is implementation-defined.
5542 <pre>
5543 relational-expression:
5544 shift-expression
5545 relational-expression < shift-expression
5546 relational-expression > shift-expression
5547 relational-expression <= shift-expression
5548 relational-expression >= shift-expression
5549 </pre>
5552 One of the following shall hold:
5553 <ul>
5554 <li> both operands have real type; or
5555 <li> both operands are pointers to qualified or unqualified versions of compatible object
5556 types.
5557 </ul>
5560 If both of the operands have arithmetic type, the usual arithmetic conversions are
5561 performed.
5563 For the purposes of these operators, a pointer to an object that is not an element of an
5564 array behaves the same as a pointer to the first element of an array of length one with the
5565 type of the object as its element type.
5567 When two pointers are compared, the result depends on the relative locations in the
5568 address space of the objects pointed to. If two pointers to object types both point to the
5569 same object, or both point one past the last element of the same array object, they
5570 compare equal. If the objects pointed to are members of the same aggregate object,
5571 pointers to structure members declared later compare greater than pointers to members
5572 declared earlier in the structure, and pointers to array elements with larger subscript
5573 values compare greater than pointers to elements of the same array with lower subscript
5574 <!--page 114 -->
5575 values. All pointers to members of the same union object compare equal. If the
5576 expression P points to an element of an array object and the expression Q points to the
5577 last element of the same array object, the pointer expression Q+1 compares greater than
5578 P. In all other cases, the behavior is undefined.
5580 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
5585 <p><small><a name="note107" href="#note107">107)</a> The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it
5586 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
5587 </small>
5593 <pre>
5594 equality-expression:
5595 relational-expression
5596 equality-expression == relational-expression
5597 equality-expression != relational-expression
5598 </pre>
5601 One of the following shall hold:
5602 <ul>
5603 <li> both operands have arithmetic type;
5604 <li> both operands are pointers to qualified or unqualified versions of compatible types;
5605 <li> one operand is a pointer to an object type and the other is a pointer to a qualified or
5606 unqualified version of void; or
5607 <li> one operand is a pointer and the other is a null pointer constant.
5608 </ul>
5611 The == (equal to) and != (not equal to) operators are analogous to the relational
5612 operators except for their lower precedence.<sup><a href="#note108"><b>108)</b></a></sup> Each of the operators yields 1 if the
5613 specified relation is true and 0 if it is false. The result has type int. For any pair of
5614 operands, exactly one of the relations is true.
5616 If both of the operands have arithmetic type, the usual arithmetic conversions are
5617 performed. Values of complex types are equal if and only if both their real parts are equal
5618 and also their imaginary parts are equal. Any two values of arithmetic types from
5619 different type domains are equal if and only if the results of their conversions to the
5620 (complex) result type determined by the usual arithmetic conversions are equal.
5624 <!--page 115 -->
5626 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
5627 null pointer constant, the null pointer constant is converted to the type of the pointer. If
5628 one operand is a pointer to an object type and the other is a pointer to a qualified or
5629 unqualified version of void, the former is converted to the type of the latter.
5631 Two pointers compare equal if and only if both are null pointers, both are pointers to the
5632 same object (including a pointer to an object and a subobject at its beginning) or function,
5633 both are pointers to one past the last element of the same array object, or one is a pointer
5634 to one past the end of one array object and the other is a pointer to the start of a different
5635 array object that happens to immediately follow the first array object in the address
5638 For the purposes of these operators, a pointer to an object that is not an element of an
5639 array behaves the same as a pointer to the first element of an array of length one with the
5640 type of the object as its element type.
5643 <p><small><a name="note108" href="#note108">108)</a> Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
5644 </small>
5645 <p><small><a name="note109" href="#note109">109)</a> Two objects may be adjacent in memory because they are adjacent elements of a larger array or
5646 adjacent members of a structure with no padding between them, or because the implementation chose
5647 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
5648 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
5649 behavior.
5650 </small>
5656 <pre>
5657 AND-expression:
5658 equality-expression
5659 AND-expression & equality-expression
5660 </pre>
5663 Each of the operands shall have integer type.
5666 The usual arithmetic conversions are performed on the operands.
5668 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
5669 the result is set if and only if each of the corresponding bits in the converted operands is
5670 set).
5675 <!--page 116 -->
5681 <pre>
5682 exclusive-OR-expression:
5683 AND-expression
5684 exclusive-OR-expression ^ AND-expression
5685 </pre>
5688 Each of the operands shall have integer type.
5691 The usual arithmetic conversions are performed on the operands.
5693 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
5694 in the result is set if and only if exactly one of the corresponding bits in the converted
5695 operands is set).
5701 <pre>
5702 inclusive-OR-expression:
5703 exclusive-OR-expression
5704 inclusive-OR-expression | exclusive-OR-expression
5705 </pre>
5708 Each of the operands shall have integer type.
5711 The usual arithmetic conversions are performed on the operands.
5713 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
5714 the result is set if and only if at least one of the corresponding bits in the converted
5715 operands is set).
5716 <!--page 117 -->
5722 <pre>
5723 logical-AND-expression:
5724 inclusive-OR-expression
5725 logical-AND-expression && inclusive-OR-expression
5726 </pre>
5729 Each of the operands shall have scalar type.
5732 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
5733 yields 0. The result has type int.
5735 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
5736 if the second operand is evaluated, there is a sequence point between the evaluations of
5737 the first and second operands. If the first operand compares equal to 0, the second
5738 operand is not evaluated.
5744 <pre>
5745 logical-OR-expression:
5746 logical-AND-expression
5747 logical-OR-expression || logical-AND-expression
5748 </pre>
5751 Each of the operands shall have scalar type.
5755 yields 0. The result has type int.
5757 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; if the
5758 second operand is evaluated, there is a sequence point between the evaluations of the first
5759 and second operands. If the first operand compares unequal to 0, the second operand is
5760 not evaluated.
5761 <!--page 118 -->
5767 <pre>
5768 conditional-expression:
5769 logical-OR-expression
5770 logical-OR-expression ? expression : conditional-expression
5771 </pre>
5774 The first operand shall have scalar type.
5776 One of the following shall hold for the second and third operands:
5777 <ul>
5778 <li> both operands have arithmetic type;
5779 <li> both operands have the same structure or union type;
5780 <li> both operands have void type;
5781 <li> both operands are pointers to qualified or unqualified versions of compatible types;
5782 <li> one operand is a pointer and the other is a null pointer constant; or
5783 <li> one operand is a pointer to an object type and the other is a pointer to a qualified or
5784 unqualified version of void.
5785 </ul>
5788 The first operand is evaluated; there is a sequence point between its evaluation and the
5789 evaluation of the second or third operand (whichever is evaluated). The second operand
5790 is evaluated only if the first compares unequal to 0; the third operand is evaluated only if
5791 the first compares equal to 0; the result is the value of the second or third operand
5792 (whichever is evaluated), converted to the type described below.<sup><a href="#note110"><b>110)</b></a></sup>
5794 If both the second and third operands have arithmetic type, the result type that would be
5795 determined by the usual arithmetic conversions, were they applied to those two operands,
5796 is the type of the result. If both the operands have structure or union type, the result has
5797 that type. If both operands have void type, the result has void type.
5799 If both the second and third operands are pointers or one is a null pointer constant and the
5800 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
5801 of the types referenced by both operands. Furthermore, if both operands are pointers to
5802 compatible types or to differently qualified versions of compatible types, the result type is
5803 a pointer to an appropriately qualified version of the composite type; if one operand is a
5804 null pointer constant, the result has the type of the other operand; otherwise, one operand
5805 is a pointer to void or a qualified version of void, in which case the result type is a
5806 pointer to an appropriately qualified version of void.
5808 <!--page 119 -->
5810 EXAMPLE The common type that results when the second and third operands are pointers is determined
5811 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
5812 pointers have compatible types.
5814 Given the declarations
5815 <pre>
5816 const void *c_vp;
5817 void *vp;
5818 const int *c_ip;
5819 volatile int *v_ip;
5820 int *ip;
5821 const char *c_cp;
5822 </pre>
5823 the third column in the following table is the common type that is the result of a conditional expression in
5824 which the first two columns are the second and third operands (in either order):
5825 <pre>
5826 c_vp c_ip const void *
5827 v_ip 0 volatile int *
5828 c_ip v_ip const volatile int *
5829 vp c_cp const void *
5830 ip c_ip const int *
5831 vp ip void *
5832 </pre>
5836 <p><small><a name="note110" href="#note110">110)</a> A conditional expression does not yield an lvalue.
5837 </small>
5843 <pre>
5844 assignment-expression:
5845 conditional-expression
5846 unary-expression assignment-operator assignment-expression
5847 assignment-operator: one of
5849 </pre>
5852 An assignment operator shall have a modifiable lvalue as its left operand.
5855 An assignment operator stores a value in the object designated by the left operand. An
5856 assignment expression has the value of the left operand after the assignment,<sup><a href="#note111"><b>111)</b></a></sup> but is not
5857 an lvalue. The type of an assignment expression is the type the left operand would have
5858 after lvalue conversion. The side effect of updating the stored value of the left operand is
5859 sequenced after the value computations of the left and right operands. The evaluations of
5860 the operands are unsequenced.
5865 <!--page 120 -->
5868 <p><small><a name="note111" href="#note111">111)</a> The implementation is permitted to read the object to determine the value but is not required to, even
5869 when the object has volatile-qualified type.
5870 </small>
5877 <ul>
5878 <li> the left operand has atomic, qualified, or unqualified arithmetic type, and the right has
5879 arithmetic type;
5880 <li> the left operand has an atomic, qualified, or unqualified version of a structure or union
5881 type compatible with the type of the right;
5882 <li> the left operand has atomic, qualified, or unqualified pointer type, and (considering
5883 the type the left operand would have after lvalue conversion) both operands are
5884 pointers to qualified or unqualified versions of compatible types, and the type pointed
5885 to by the left has all the qualifiers of the type pointed to by the right;
5886 <li> the left operand has atomic, qualified, or unqualified pointer type, and (considering
5887 the type the left operand would have after lvalue conversion) one operand is a pointer
5888 to an object type, and the other is a pointer to a qualified or unqualified version of
5889 void, and the type pointed to by the left has all the qualifiers of the type pointed to
5890 by the right;
5891 <li> the left operand is an atomic, qualified, or unqualified pointer, and the right is a null
5892 pointer constant; or
5893 <li> the left operand has type atomic, qualified, or unqualified _Bool, and the right is a
5894 pointer.
5895 </ul>
5898 In simple assignment (=), the value of the right operand is converted to the type of the
5899 assignment expression and replaces the value stored in the object designated by the left
5900 operand.
5902 If the value being stored in an object is read from another object that overlaps in any way
5903 the storage of the first object, then the overlap shall be exact and the two objects shall
5904 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
5905 undefined.
5907 EXAMPLE 1 In the program fragment
5912 <!--page 121 -->
5913 <pre>
5914 int f(void);
5915 char c;
5916 /* ... */
5917 if ((c = f()) == -1)
5918 /* ... */
5919 </pre>
5920 the int value returned by the function may be truncated when stored in the char, and then converted back
5921 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
5922 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
5923 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
5924 variable c should be declared as int.
5927 EXAMPLE 2 In the fragment:
5928 <pre>
5929 char c;
5930 int i;
5931 long l;
5932 l = (c = i);
5933 </pre>
5934 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
5935 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
5936 that is, long int type.
5939 EXAMPLE 3 Consider the fragment:
5940 <pre>
5941 const char **cpp;
5942 char *p;
5943 const char c = 'A';
5944 cpp = &p; // constraint violation
5945 *cpp = &c; // valid
5946 *p = 0; // valid
5947 </pre>
5948 The first assignment is unsafe because it would allow the following valid code to attempt to change the
5949 value of the const object c.
5953 <p><small><a name="note112" href="#note112">112)</a> The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
5954 (specified in <a href="#6.3.2.1">6.3.2.1</a>) that changes lvalues to ''the value of the expression'' and thus removes any type
5955 qualifiers that were applied to the type category of the expression (for example, it removes const but
5956 not volatile from the type int volatile * const).
5957 </small>
5963 For the operators += and -= only, either the left operand shall be an atomic, qualified, or
5964 unqualified pointer to a complete object type, and the right shall have integer type; or the
5965 left operand shall have atomic, qualified, or unqualified arithmetic type, and the right
5966 shall have arithmetic type.
5968 For the other operators, the left operand shall have atomic, qualified, or unqualified
5969 arithmetic type, and (considering the type the left operand would have after lvalue
5970 conversion) each operand shall have arithmetic type consistent with those allowed by the
5971 corresponding binary operator.
5974 A compound assignment of the form E1 op = E2 is equivalent to the simple assignment
5975 expression E1 = E1 op (E2), except that the lvalue E1 is evaluated only once, and with
5976 respect to an indeterminately-sequenced function call, the operation of a compound
5977 <!--page 122 -->
5978 assignment is a single evaluation. If E1 has an atomic type, compound assignment is a
5979 read-modify-write operation with memory_order_seq_cst memory order
5985 <!--page 123 -->
5988 <p><small><a name="note113" href="#note113">113)</a> Where a pointer to an atomic object can be formed and E1 and E2 have integer type, this is equivalent
5989 to the following code sequence where T1 is the type of E1 and T2 is the type of E2:
5991 <pre>
5992 T1 *addr = &E1;
5993 T2 val = (E2);
5994 T1 old = *addr;
5995 T1 new;
5996 do {
5997 new = old op val;
5998 } while (!atomic_compare_exchange_strong(addr, &old, new));
5999 </pre>
6000 with new being the result of the operation.
6001 If E1 or E2 has floating type, then exceptional conditions or floating-point exceptions encountered
6002 during discarded evaluations of new should also be discarded in order to satisfy the equivalence of E1
6003 op = E2 and E1 = E1 op (E2). For example, if <a href="#F">annex F</a> is in effect, the floating types involved have
6006 <pre>
6008 #pragma STDC FENV_ACCESS ON
6009 /* ... */
6010 fenv_t fenv;
6011 T1 *addr = &E1;
6012 T2 val = E2;
6013 T1 old = *addr;
6014 T1 new;
6015 feholdexcept(&fenv);
6016 for (;;) {
6017 new = old op val;
6018 if (atomic_compare_exchange_strong(addr, &old, new))
6019 break;
6020 feclearexcept(FE_ALL_EXCEPT);
6021 }
6022 feupdateenv(&fenv);
6023 </pre>
6024 If FLT_EVAL_METHOD is not 0, then T2 must be a type with the range and precision to which E2 is
6025 evaluated in order to satisfy the equivalence.
6026 </small>
6032 <pre>
6033 expression:
6034 assignment-expression
6035 expression , assignment-expression
6036 </pre>
6039 The left operand of a comma operator is evaluated as a void expression; there is a
6040 sequence point between its evaluation and that of the right operand. Then the right
6041 operand is evaluated; the result has its type and value.<sup><a href="#note114"><b>114)</b></a></sup>
6043 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
6044 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
6045 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
6046 expression of a conditional operator in such contexts. In the function call
6047 <pre>
6049 </pre>
6050 the function has three arguments, the second of which has the value 5.
6057 <!--page 124 -->
6060 <p><small><a name="note114" href="#note114">114)</a> A comma operator does not yield an lvalue.
6061 </small>
6067 <pre>
6068 constant-expression:
6069 conditional-expression
6070 </pre>
6073 A constant expression can be evaluated during translation rather than runtime, and
6074 accordingly may be used in any place that a constant may be.
6077 Constant expressions shall not contain assignment, increment, decrement, function-call,
6078 or comma operators, except when they are contained within a subexpression that is not
6081 Each constant expression shall evaluate to a constant that is in the range of representable
6082 values for its type.
6085 An expression that evaluates to a constant is required in several contexts. If a floating
6086 expression is evaluated in the translation environment, the arithmetic range and precision
6087 shall be at least as great as if the expression were being evaluated in the execution
6090 An integer constant expression<sup><a href="#note117"><b>117)</b></a></sup> shall have integer type and shall only have operands
6091 that are integer constants, enumeration constants, character constants, sizeof
6092 expressions whose results are integer constants, _Alignof expressions, and floating
6093 constants that are the immediate operands of casts. Cast operators in an integer constant
6094 expression shall only convert arithmetic types to integer types, except as part of an
6095 operand to the sizeof or _Alignof operator.
6097 More latitude is permitted for constant expressions in initializers. Such a constant
6098 expression shall be, or evaluate to, one of the following:
6099 <ul>
6100 <li> an arithmetic constant expression,
6104 <!--page 125 -->
6105 <li> a null pointer constant,
6106 <li> an address constant, or
6107 <li> an address constant for a complete object type plus or minus an integer constant
6108 expression.
6109 </ul>
6111 An arithmetic constant expression shall have arithmetic type and shall only have
6112 operands that are integer constants, floating constants, enumeration constants, character
6113 constants, sizeof expressions whose results are integer constants, and _Alignof
6114 expressions. Cast operators in an arithmetic constant expression shall only convert
6115 arithmetic types to arithmetic types, except as part of an operand to a sizeof or
6116 _Alignof operator.
6118 An address constant is a null pointer, a pointer to an lvalue designating an object of static
6119 storage duration, or a pointer to a function designator; it shall be created explicitly using
6120 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
6121 an expression of array or function type. The array-subscript [] and member-access .
6122 and -> operators, the address & and indirection * unary operators, and pointer casts may
6123 be used in the creation of an address constant, but the value of an object shall not be
6124 accessed by use of these operators.
6126 An implementation may accept other forms of constant expressions.
6128 The semantic rules for the evaluation of a constant expression are the same as for
6130 <p><b> Forward references</b>: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), initialization (<a href="#6.7.9">6.7.9</a>).
6135 <!--page 126 -->
6138 <p><small><a name="note115" href="#note115">115)</a> The operand of a sizeof or _Alignof operator is usually not evaluated (<a href="#6.5.3.4">6.5.3.4</a>).
6139 </small>
6140 <p><small><a name="note116" href="#note116">116)</a> The use of evaluation formats as characterized by FLT_EVAL_METHOD also applies to evaluation in
6141 the translation environment.
6142 </small>
6143 <p><small><a name="note117" href="#note117">117)</a> An integer constant expression is required in a number of contexts such as the size of a bit-field
6144 member of a structure, the value of an enumeration constant, and the size of a non-variable length
6145 array. Further constraints that apply to the integer constant expressions used in conditional-inclusion
6147 </small>
6150 <pre>
6152 </pre>
6153 the expression is a valid integer constant expression with value one.
6154 </small>
6160 <pre>
6161 declaration:
6163 static_assert-declaration
6164 declaration-specifiers:
6170 init-declarator-list:
6171 init-declarator
6172 init-declarator-list , init-declarator
6173 init-declarator:
6174 declarator
6175 declarator = initializer
6176 </pre>
6179 A declaration other than a static_assert declaration shall declare at least a declarator
6180 (other than the parameters of a function or the members of a structure or union), a tag, or
6181 the members of an enumeration.
6183 If an identifier has no linkage, there shall be no more than one declaration of the identifier
6184 (in a declarator or type specifier) with the same scope and in the same name space, except
6185 that:
6186 <ul>
6187 <li> a typedef name may be redefined to denote the same type as it currently does,
6188 provided that type is not a variably modified type;
6190 </ul>
6192 All declarations in the same scope that refer to the same object or function shall specify
6193 compatible types.
6196 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
6197 of an identifier is a declaration for that identifier that:
6198 <ul>
6199 <li> for an object, causes storage to be reserved for that object;
6201 <!--page 127 -->
6202 <li> for an enumeration constant, is the (only) declaration of the identifier;
6203 <li> for a typedef name, is the first (or only) declaration of the identifier.
6204 </ul>
6206 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
6207 storage duration, and part of the type of the entities that the declarators denote. The init-
6208 declarator-list is a comma-separated sequence of declarators, each of which may have
6209 additional type information, or an initializer, or both. The declarators contain the
6210 identifiers (if any) being declared.
6212 If an identifier for an object is declared with no linkage, the type for the object shall be
6213 complete by the end of its declarator, or by the end of its init-declarator if it has an
6214 initializer; in the case of function parameters (including in prototypes), it is the adjusted
6216 <p><b> Forward references</b>: declarators (<a href="#6.7.6">6.7.6</a>), enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), initialization
6217 (<a href="#6.7.9">6.7.9</a>), type names (<a href="#6.7.7">6.7.7</a>), type qualifiers (<a href="#6.7.3">6.7.3</a>).
6220 <p><small><a name="note119" href="#note119">119)</a> Function definitions have a different syntax, described in <a href="#6.9.1">6.9.1</a>.
6221 </small>
6227 <pre>
6228 storage-class-specifier:
6229 typedef
6230 extern
6231 static
6232 _Thread_local
6233 auto
6234 register
6235 </pre>
6238 At most, one storage-class specifier may be given in the declaration specifiers in a
6239 declaration, except that _Thread_local may appear with static or extern.<sup><a href="#note120"><b>120)</b></a></sup>
6241 In the declaration of an object with block scope, if the declaration specifiers include
6242 _Thread_local, they shall also include either static or extern. If
6243 _Thread_local appears in any declaration of an object, it shall be present in every
6244 declaration of that object.
6246 _Thread_local shall not appear in the declaration specifiers of a function declaration.
6251 <!--page 128 -->
6254 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
6255 only; it is discussed in <a href="#6.7.8">6.7.8</a>. The meanings of the various linkages and storage durations
6258 A declaration of an identifier for an object with storage-class specifier register
6259 suggests that access to the object be as fast as possible. The extent to which such
6260 suggestions are effective is implementation-defined.<sup><a href="#note121"><b>121)</b></a></sup>
6262 The declaration of an identifier for a function that has block scope shall have no explicit
6263 storage-class specifier other than extern.
6265 If an aggregate or union object is declared with a storage-class specifier other than
6266 typedef, the properties resulting from the storage-class specifier, except with respect to
6267 linkage, also apply to the members of the object, and so on recursively for any aggregate
6268 or union member objects.
6274 <!--page 129 -->
6277 <p><small><a name="note120" href="#note120">120)</a> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
6278 </small>
6279 <p><small><a name="note121" href="#note121">121)</a> The implementation may treat any register declaration simply as an auto declaration. However,
6280 whether or not addressable storage is actually used, the address of any part of an object declared with
6281 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
6282 operator as discussed in <a href="#6.5.3.2">6.5.3.2</a>) or implicitly (by converting an array name to a pointer as discussed in
6283 <a href="#6.3.2.1">6.3.2.1</a>). Thus, the only operators that can be applied to an array declared with storage-class specifier
6284 register are sizeof and _Alignof.
6285 </small>
6291 <pre>
6292 type-specifier:
6293 void
6294 char
6295 short
6296 int
6297 long
6298 float
6299 double
6300 signed
6301 unsigned
6302 _Bool
6303 _Complex
6304 atomic-type-specifier
6305 struct-or-union-specifier
6306 enum-specifier
6307 typedef-name
6308 </pre>
6311 At least one type specifier shall be given in the declaration specifiers in each declaration,
6312 and in the specifier-qualifier list in each struct declaration and type name. Each list of
6313 type specifiers shall be one of the following multisets (delimited by commas, when there
6314 is more than one multiset per item); the type specifiers may occur in any order, possibly
6315 intermixed with the other declaration specifiers.
6316 <ul>
6317 <li> void
6318 <li> char
6319 <li> signed char
6320 <li> unsigned char
6321 <li> short, signed short, short int, or signed short int
6322 <li> unsigned short, or unsigned short int
6323 <li> int, signed, or signed int
6324 <li> unsigned, or unsigned int
6325 <li> long, signed long, long int, or signed long int
6326 <li> unsigned long, or unsigned long int
6327 <!--page 130 -->
6328 <li> long long, signed long long, long long int, or
6329 signed long long int
6330 <li> unsigned long long, or unsigned long long int
6331 <li> float
6332 <li> double
6333 <li> long double
6334 <li> _Bool
6335 <li> float _Complex
6336 <li> double _Complex
6337 <li> long double _Complex
6338 <li> atomic type specifier
6339 <li> struct or union specifier
6340 <li> enum specifier
6341 <li> typedef name
6342 </ul>
6344 The type specifier _Complex shall not be used if the implementation does not support
6348 Specifiers for structures, unions, enumerations, and atomic types are discussed in <a href="#6.7.2.1">6.7.2.1</a>
6349 through <a href="#6.7.2.4">6.7.2.4</a>. Declarations of typedef names are discussed in <a href="#6.7.8">6.7.8</a>. The
6352 Each of the comma-separated multisets designates the same type, except that for bit-
6353 fields, it is implementation-defined whether the specifier int designates the same type as
6354 signed int or the same type as unsigned int.
6355 <p><b> Forward references</b>: atomic type specifiers (<a href="#6.7.2.4">6.7.2.4</a>), enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>),
6356 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
6362 <!--page 131 -->
6363 <pre>
6364 struct-or-union-specifier:
6366 struct-or-union identifier
6367 struct-or-union:
6368 struct
6369 union
6370 struct-declaration-list:
6371 struct-declaration
6372 struct-declaration-list struct-declaration
6373 struct-declaration:
6375 static_assert-declaration
6376 specifier-qualifier-list:
6379 struct-declarator-list:
6380 struct-declarator
6381 struct-declarator-list , struct-declarator
6382 struct-declarator:
6383 declarator
6385 </pre>
6388 A struct-declaration that does not declare an anonymous structure or anonymous union
6389 shall contain a struct-declarator-list.
6391 A structure or union shall not contain a member with incomplete or function type (hence,
6392 a structure shall not contain an instance of itself, but may contain a pointer to an instance
6393 of itself), except that the last member of a structure with more than one named member
6394 may have incomplete array type; such a structure (and any union containing, possibly
6395 recursively, a member that is such a structure) shall not be a member of a structure or an
6396 element of an array.
6398 The expression that specifies the width of a bit-field shall be an integer constant
6399 expression with a nonnegative value that does not exceed the width of an object of the
6400 type that would be specified were the colon and expression omitted.<sup><a href="#note122"><b>122)</b></a></sup> If the value is
6401 zero, the declaration shall have no declarator.
6403 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
6404 int, unsigned int, or some other implementation-defined type. It is
6405 implementation-defined whether atomic types are permitted.
6407 <!--page 132 -->
6410 As discussed in <a href="#6.2.5">6.2.5</a>, a structure is a type consisting of a sequence of members, whose
6411 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
6412 of members whose storage overlap.
6414 Structure and union specifiers have the same form. The keywords struct and union
6415 indicate that the type being specified is, respectively, a structure type or a union type.
6417 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
6418 within a translation unit. The struct-declaration-list is a sequence of declarations for the
6419 members of the structure or union. If the struct-declaration-list does not contain any
6420 named members, either directly or via an anonymous structure or anonymous union, the
6421 behavior is undefined. The type is incomplete until immediately after the } that
6422 terminates the list, and complete thereafter.
6424 A member of a structure or union may have any complete object type other than a
6425 variably modified type.<sup><a href="#note123"><b>123)</b></a></sup> In addition, a member may be declared to consist of a
6426 specified number of bits (including a sign bit, if any). Such a member is called a
6429 A bit-field is interpreted as having a signed or unsigned integer type consisting of the
6430 specified number of bits.<sup><a href="#note125"><b>125)</b></a></sup> If the value 0 or 1 is stored into a nonzero-width bit-field of
6431 type _Bool, the value of the bit-field shall compare equal to the value stored; a _Bool
6432 bit-field has the semantics of a _Bool.
6434 An implementation may allocate any addressable storage unit large enough to hold a bit-
6435 field. If enough space remains, a bit-field that immediately follows another bit-field in a
6436 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
6437 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
6438 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
6439 low-order or low-order to high-order) is implementation-defined. The alignment of the
6440 addressable storage unit is unspecified.
6442 A bit-field declaration with no declarator, but only a colon and a width, indicates an
6443 unnamed bit-field.<sup><a href="#note126"><b>126)</b></a></sup> As a special case, a bit-field structure member with a width of 0
6446 <!--page 133 -->
6447 indicates that no further bit-field is to be packed into the unit in which the previous bit-
6448 field, if any, was placed.
6450 An unnamed member whose type specifier is a structure specifier with no tag is called an
6451 anonymous structure; an unnamed member whose type specifier is a union specifier with
6452 no tag is called an anonymous union. The members of an anonymous structure or union
6453 are considered to be members of the containing structure or union. This applies
6454 recursively if the containing structure or union is also anonymous.
6456 Each non-bit-field member of a structure or union object is aligned in an implementation-
6457 defined manner appropriate to its type.
6459 Within a structure object, the non-bit-field members and the units in which bit-fields
6460 reside have addresses that increase in the order in which they are declared. A pointer to a
6461 structure object, suitably converted, points to its initial member (or if that member is a
6462 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
6463 padding within a structure object, but not at its beginning.
6465 The size of a union is sufficient to contain the largest of its members. The value of at
6466 most one of the members can be stored in a union object at any time. A pointer to a
6467 union object, suitably converted, points to each of its members (or if a member is a bit-
6468 field, then to the unit in which it resides), and vice versa.
6470 There may be unnamed padding at the end of a structure or union.
6472 As a special case, the last element of a structure with more than one named member may
6473 have an incomplete array type; this is called a flexible array member. In most situations,
6474 the flexible array member is ignored. In particular, the size of the structure is as if the
6475 flexible array member were omitted except that it may have more trailing padding than
6476 the omission would imply. However, when a . (or ->) operator has a left operand that is
6477 (a pointer to) a structure with a flexible array member and the right operand names that
6478 member, it behaves as if that member were replaced with the longest array (with the same
6479 element type) that would not make the structure larger than the object being accessed; the
6480 offset of the array shall remain that of the flexible array member, even if this would differ
6481 from that of the replacement array. If this array would have no elements, it behaves as if
6482 it had one element but the behavior is undefined if any attempt is made to access that
6483 element or to generate a pointer one past it.
6485 EXAMPLE 1 The following illustrates anonymous structures and unions:
6486 <!--page 134 -->
6487 <pre>
6488 struct v {
6489 union { // anonymous union
6490 struct { int i, j; }; // anonymous structure
6491 struct { long k, l; } w;
6492 };
6493 int m;
6494 } v1;
6495 v1.i = 2; // valid
6496 v1.k = 3; // invalid: inner structure is not anonymous
6497 v1.w.k = 5; // valid
6498 </pre>
6501 EXAMPLE 2 After the declaration:
6502 <pre>
6503 struct s { int n; double d[]; };
6504 </pre>
6505 the structure struct s has a flexible array member d. A typical way to use this is:
6506 <pre>
6507 int m = /* some value */;
6508 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
6509 </pre>
6510 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
6511 p had been declared as:
6512 <pre>
6513 struct { int n; double d[m]; } *p;
6514 </pre>
6515 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
6516 not be the same).
6518 Following the above declaration:
6519 <pre>
6520 struct s t1 = { 0 }; // valid
6522 t1.n = 4; // valid
6524 </pre>
6525 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
6526 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
6527 <pre>
6528 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)
6529 </pre>
6530 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
6531 code.
6533 After the further declaration:
6534 <pre>
6535 struct ss { int n; };
6536 </pre>
6537 the expressions:
6538 <pre>
6539 sizeof (struct s) >= sizeof (struct ss)
6540 sizeof (struct s) >= offsetof(struct s, d)
6541 </pre>
6542 are always equal to 1.
6544 If sizeof (double) is 8, then after the following code is executed:
6545 <pre>
6546 struct s *s1;
6547 struct s *s2;
6548 s1 = malloc(sizeof (struct s) + 64);
6549 s2 = malloc(sizeof (struct s) + 46);
6550 </pre>
6551 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
6552 purposes, as if the identifiers had been declared as:
6553 <pre>
6554 struct { int n; double d[8]; } *s1;
6555 struct { int n; double d[5]; } *s2;
6556 </pre>
6558 Following the further successful assignments:
6559 <!--page 135 -->
6560 <pre>
6561 s1 = malloc(sizeof (struct s) + 10);
6562 s2 = malloc(sizeof (struct s) + 6);
6563 </pre>
6564 they then behave as if the declarations were:
6565 <pre>
6566 struct { int n; double d[1]; } *s1, *s2;
6567 </pre>
6568 and:
6569 <pre>
6570 double *dp;
6572 *dp = 42; // valid
6574 *dp = 42; // undefined behavior
6575 </pre>
6577 The assignment:
6578 <pre>
6579 *s1 = *s2;
6580 </pre>
6581 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
6582 of the structure, they might be copied or simply overwritten with indeterminate values.
6585 EXAMPLE 3 Because members of anonymous structures and unions are considered to be members of the
6586 containing structure or union, struct s in the following example has more than one named member and
6587 thus the use of a flexible array member is valid:
6588 <pre>
6589 struct s {
6590 struct { int i; };
6591 int a[];
6592 };
6593 </pre>
6595 <p><b> Forward references</b>: declarators (<a href="#6.7.6">6.7.6</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>).
6598 <p><small><a name="note122" href="#note122">122)</a> While the number of bits in a _Bool object is at least CHAR_BIT, the width (number of sign and
6599 value bits) of a _Bool may be just 1 bit.
6600 </small>
6601 <p><small><a name="note123" href="#note123">123)</a> A structure or union cannot contain a member with a variably modified type because member names
6603 </small>
6604 <p><small><a name="note124" href="#note124">124)</a> The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
6605 or arrays of bit-field objects.
6606 </small>
6607 <p><small><a name="note125" href="#note125">125)</a> As specified in <a href="#6.7.2">6.7.2</a> above, if the actual type specifier used is int or a typedef-name defined as int,
6608 then it is implementation-defined whether the bit-field is signed or unsigned.
6609 </small>
6610 <p><small><a name="note126" href="#note126">126)</a> An unnamed bit-field structure member is useful for padding to conform to externally imposed
6611 layouts.
6612 </small>
6618 <pre>
6619 enum-specifier:
6622 enum identifier
6623 enumerator-list:
6624 enumerator
6625 enumerator-list , enumerator
6626 enumerator:
6627 enumeration-constant
6628 enumeration-constant = constant-expression
6629 </pre>
6632 The expression that defines the value of an enumeration constant shall be an integer
6633 constant expression that has a value representable as an int.
6634 <!--page 136 -->
6637 The identifiers in an enumerator list are declared as constants that have type int and
6638 may appear wherever such are permitted.<sup><a href="#note127"><b>127)</b></a></sup> An enumerator with = defines its
6639 enumeration constant as the value of the constant expression. If the first enumerator has
6640 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
6641 defines its enumeration constant as the value of the constant expression obtained by
6642 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
6643 = may produce enumeration constants with values that duplicate other values in the same
6644 enumeration.) The enumerators of an enumeration are also known as its members.
6646 Each enumerated type shall be compatible with char, a signed integer type, or an
6647 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note128"><b>128)</b></a></sup> but shall be
6648 capable of representing the values of all the members of the enumeration. The
6649 enumerated type is incomplete until immediately after the } that terminates the list of
6650 enumerator declarations, and complete thereafter.
6652 EXAMPLE The following fragment:
6653 <pre>
6654 enum hue { chartreuse, burgundy, claret=20, winedark };
6655 enum hue col, *cp;
6656 col = claret;
6657 cp = &col;
6658 if (*cp != burgundy)
6659 /* ... */
6660 </pre>
6661 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
6662 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
6667 <p><small><a name="note127" href="#note127">127)</a> Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
6668 each other and from other identifiers declared in ordinary declarators.
6669 </small>
6670 <p><small><a name="note128" href="#note128">128)</a> An implementation may delay the choice of which integer type until all enumeration constants have
6671 been seen.
6672 </small>
6678 A specific type shall have its content defined at most once.
6680 Where two declarations that use the same tag declare the same type, they shall both use
6681 the same choice of struct, union, or enum.
6683 A type specifier of the form
6684 <pre>
6685 enum identifier
6686 </pre>
6687 without an enumerator list shall only appear after the type it specifies is complete.
6690 <!--page 137 -->
6693 All declarations of structure, union, or enumerated types that have the same scope and
6694 use the same tag declare the same type. Irrespective of whether there is a tag or what
6695 other declarations of the type are in the same translation unit, the type is incomplete<sup><a href="#note129"><b>129)</b></a></sup>
6696 until immediately after the closing brace of the list defining the content, and complete
6697 thereafter.
6699 Two declarations of structure, union, or enumerated types which are in different scopes or
6700 use different tags declare distinct types. Each declaration of a structure, union, or
6701 enumerated type which does not include a tag declares a distinct type.
6703 A type specifier of the form
6704 <pre>
6706 </pre>
6707 or
6708 <pre>
6710 </pre>
6711 or
6712 <pre>
6714 </pre>
6715 declares a structure, union, or enumerated type. The list defines the structure content,
6716 union content, or enumeration content. If an identifier is provided,<sup><a href="#note130"><b>130)</b></a></sup> the type specifier
6717 also declares the identifier to be the tag of that type.
6719 A declaration of the form
6720 <pre>
6721 struct-or-union identifier ;
6722 </pre>
6723 specifies a structure or union type and declares the identifier as a tag of that type.<sup><a href="#note131"><b>131)</b></a></sup>
6725 If a type specifier of the form
6726 <pre>
6727 struct-or-union identifier
6728 </pre>
6729 occurs other than as part of one of the above forms, and no other declaration of the
6730 identifier as a tag is visible, then it declares an incomplete structure or union type, and
6735 <!--page 138 -->
6737 If a type specifier of the form
6738 <pre>
6739 struct-or-union identifier
6740 </pre>
6741 or
6742 <pre>
6743 enum identifier
6744 </pre>
6745 occurs other than as part of one of the above forms, and a declaration of the identifier as a
6746 tag is visible, then it specifies the same type as that other declaration, and does not
6747 redeclare the tag.
6749 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
6750 <pre>
6751 struct tnode {
6752 int count;
6753 struct tnode *left, *right;
6754 };
6755 </pre>
6756 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
6757 declaration has been given, the declaration
6758 <pre>
6759 struct tnode s, *sp;
6760 </pre>
6761 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
6762 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
6763 which sp points; the expression s.right->count designates the count member of the right struct
6764 tnode pointed to from s.
6766 The following alternative formulation uses the typedef mechanism:
6767 <pre>
6768 typedef struct tnode TNODE;
6769 struct tnode {
6770 int count;
6771 TNODE *left, *right;
6772 };
6773 TNODE s, *sp;
6774 </pre>
6777 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
6778 structures, the declarations
6779 <pre>
6780 struct s1 { struct s2 *s2p; /* ... */ }; // D1
6781 struct s2 { struct s1 *s1p; /* ... */ }; // D2
6782 </pre>
6783 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
6784 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
6785 D2. To eliminate this context sensitivity, the declaration
6786 <pre>
6787 struct s2;
6788 </pre>
6789 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
6790 completes the specification of the new type.
6792 <p><b> Forward references</b>: declarators (<a href="#6.7.6">6.7.6</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
6793 <!--page 139 -->
6796 <p><small><a name="note129" href="#note129">129)</a> An incomplete type may only by used when the size of an object of that type is not needed. It is not
6797 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
6798 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
6799 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
6800 </small>
6801 <p><small><a name="note130" href="#note130">130)</a> If there is no identifier, the type can, within the translation unit, only be referred to by the declaration
6802 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
6803 can make use of that typedef name to declare objects having the specified structure, union, or
6804 enumerated type.
6805 </small>
6806 <p><small><a name="note131" href="#note131">131)</a> A similar construction with enum does not exist.
6807 </small>
6813 <pre>
6814 atomic-type-specifier:
6815 _Atomic ( type-name )
6816 </pre>
6819 Atomic type specifiers shall not be used if the implementation does not support atomic
6822 The type name in an atomic type specifier shall not refer to an array type, a function type,
6823 an atomic type, or a qualified type.
6826 The properties associated with atomic types are meaningful only for expressions that are
6827 lvalues. If the _Atomic keyword is immediately followed by a left parenthesis, it is
6828 interpreted as a type specifier (with a type name), not as a type qualifier.
6834 <pre>
6835 type-qualifier:
6836 const
6837 restrict
6838 volatile
6839 _Atomic
6840 </pre>
6843 Types other than pointer types whose referenced type is an object type shall not be
6844 restrict-qualified.
6846 The type modified by the _Atomic qualifier shall not be an array type or a function
6847 type.
6850 The properties associated with qualified types are meaningful only for expressions that
6853 If the same qualifier appears more than once in the same specifier-qualifier-list, either
6854 directly or via one or more typedefs, the behavior is the same as if it appeared only
6855 once. If other qualifiers appear along with the _Atomic qualifier in a specifier-qualifier-
6857 <!--page 140 -->
6858 list, the resulting type is the so-qualified atomic type.
6860 If an attempt is made to modify an object defined with a const-qualified type through use
6861 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
6862 made to refer to an object defined with a volatile-qualified type through use of an lvalue
6863 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note133"><b>133)</b></a></sup>
6865 An object that has volatile-qualified type may be modified in ways unknown to the
6866 implementation or have other unknown side effects. Therefore any expression referring
6867 to such an object shall be evaluated strictly according to the rules of the abstract machine,
6868 as described in <a href="#5.1.2.3">5.1.2.3</a>. Furthermore, at every sequence point the value last stored in the
6869 object shall agree with that prescribed by the abstract machine, except as modified by the
6870 unknown factors mentioned previously.<sup><a href="#note134"><b>134)</b></a></sup> What constitutes an access to an object that
6871 has volatile-qualified type is implementation-defined.
6873 An object that is accessed through a restrict-qualified pointer has a special association
6874 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
6875 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note135"><b>135)</b></a></sup> The intended
6876 use of the restrict qualifier (like the register storage class) is to promote
6877 optimization, and deleting all instances of the qualifier from all preprocessing translation
6878 units composing a conforming program does not change its meaning (i.e., observable
6879 behavior).
6881 If the specification of an array type includes any type qualifiers, the element type is so-
6882 qualified, not the array type. If the specification of a function type includes any type
6885 For two qualified types to be compatible, both shall have the identically qualified version
6886 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
6887 does not affect the specified type.
6889 EXAMPLE 1 An object declared
6890 <pre>
6891 extern const volatile int real_time_clock;
6892 </pre>
6896 <!--page 141 -->
6897 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
6900 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
6901 modify an aggregate type:
6902 <pre>
6903 const struct s { int mem; } cs = { 1 };
6904 struct s ncs; // the object ncs is modifiable
6907 int *pi;
6908 const int *pci;
6909 ncs = cs; // valid
6910 cs = ncs; // violates modifiable lvalue constraint for =
6911 pi = &ncs.mem; // valid
6912 pi = &cs.mem; // violates type constraints for =
6913 pci = &cs.mem; // valid
6915 </pre>
6918 EXAMPLE 3 The declaration
6919 <pre>
6920 _Atomic volatile int *p;
6921 </pre>
6922 specifies that p has the type ''pointer to volatile atomic int'', a pointer to a volatile-qualified atomic type.
6926 <p><small><a name="note132" href="#note132">132)</a> The implementation may place a const object that is not volatile in a read-only region of
6927 storage. Moreover, the implementation need not allocate storage for such an object if its address is
6928 never used.
6929 </small>
6930 <p><small><a name="note133" href="#note133">133)</a> This applies to those objects that behave as if they were defined with qualified types, even if they are
6931 never actually defined as objects in the program (such as an object at a memory-mapped input/output
6932 address).
6933 </small>
6934 <p><small><a name="note134" href="#note134">134)</a> A volatile declaration may be used to describe an object corresponding to a memory-mapped
6935 input/output port or an object accessed by an asynchronously interrupting function. Actions on
6936 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
6937 permitted by the rules for evaluating expressions.
6938 </small>
6939 <p><small><a name="note135" href="#note135">135)</a> For example, a statement that assigns a value returned by malloc to a single pointer establishes this
6940 association between the allocated object and the pointer.
6941 </small>
6942 <p><small><a name="note136" href="#note136">136)</a> Both of these can occur through the use of typedefs.
6943 </small>
6948 Let D be a declaration of an ordinary identifier that provides a means of designating an
6949 object P as a restrict-qualified pointer to type T.
6951 If D appears inside a block and does not have storage class extern, let B denote the
6952 block. If D appears in the list of parameter declarations of a function definition, let B
6953 denote the associated block. Otherwise, let B denote the block of main (or the block of
6954 whatever function is called at program startup in a freestanding environment).
6956 In what follows, a pointer expression E is said to be based on object P if (at some
6957 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
6958 a copy of the array object into which it formerly pointed would change the value of E.<sup><a href="#note137"><b>137)</b></a></sup>
6959 Note that ''based'' is defined only for expressions with pointer types.
6961 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
6962 access the value of the object X that it designates, and X is also modified (by any means),
6963 then the following requirements apply: T shall not be const-qualified. Every other lvalue
6964 used to access the value of X shall also have its address based on P. Every access that
6965 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
6966 is assigned the value of a pointer expression E that is based on another restricted pointer
6969 <!--page 142 -->
6970 object P2, associated with block B2, then either the execution of B2 shall begin before
6971 the execution of B, or the execution of B2 shall end prior to the assignment. If these
6972 requirements are not met, then the behavior is undefined.
6974 Here an execution of B means that portion of the execution of the program that would
6975 correspond to the lifetime of an object with scalar type and automatic storage duration
6976 associated with B.
6978 A translator is free to ignore any or all aliasing implications of uses of restrict.
6980 EXAMPLE 1 The file scope declarations
6981 <pre>
6982 int * restrict a;
6983 int * restrict b;
6984 extern int c[];
6985 </pre>
6986 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
6987 program, then it is never accessed using either of the other two.
6990 EXAMPLE 2 The function parameter declarations in the following example
6991 <pre>
6992 void f(int n, int * restrict p, int * restrict q)
6993 {
6995 *p++ = *q++;
6996 }
6997 </pre>
6998 assert that, during each execution of the function, if an object is accessed through one of the pointer
6999 parameters, then it is not also accessed through the other.
7001 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
7002 analysis of function f without examining any of the calls of f in the program. The cost is that the
7003 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
7004 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
7005 both p and q.
7006 <pre>
7007 void g(void)
7008 {
7009 extern int d[100];
7012 }
7013 </pre>
7016 EXAMPLE 3 The function parameter declarations
7017 <pre>
7018 void h(int n, int * restrict p, int * restrict q, int * restrict r)
7019 {
7020 int i;
7022 p[i] = q[i] + r[i];
7023 }
7024 </pre>
7025 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
7026 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
7027 modified within function h.
7028 <!--page 143 -->
7030 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
7031 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
7032 between restricted pointers declared in nested blocks have defined behavior.
7033 <pre>
7034 {
7035 int * restrict p1;
7036 int * restrict q1;
7037 p1 = q1; // undefined behavior
7038 {
7039 int * restrict p2 = p1; // valid
7040 int * restrict q2 = q1; // valid
7041 p1 = q2; // undefined behavior
7042 p2 = q2; // undefined behavior
7043 }
7044 }
7045 </pre>
7047 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
7048 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
7049 example, this permits new_vector to return a vector.
7050 <pre>
7051 typedef struct { int n; float * restrict v; } vector;
7052 vector new_vector(int n)
7053 {
7054 vector t;
7055 t.n = n;
7056 t.v = malloc(n * sizeof (float));
7057 return t;
7058 }
7059 </pre>
7063 <p><small><a name="note137" href="#note137">137)</a> In other words, E depends on the value of P itself rather than on the value of an object referenced
7064 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
7065 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
7066 expressions *p and p[1] are not.
7067 </small>
7073 <pre>
7074 function-specifier:
7075 inline
7076 _Noreturn
7077 </pre>
7080 Function specifiers shall be used only in the declaration of an identifier for a function.
7082 An inline definition of a function with external linkage shall not contain a definition of a
7083 modifiable object with static or thread storage duration, and shall not contain a reference
7084 to an identifier with internal linkage.
7086 In a hosted environment, no function specifier(s) shall appear in a declaration of main.
7089 A function specifier may appear more than once; the behavior is the same as if it
7090 appeared only once.
7092 A function declared with an inline function specifier is an inline function. Making a
7093 function an inline function suggests that calls to the function be as fast as possible.<sup><a href="#note138"><b>138)</b></a></sup>
7094 <!--page 144 -->
7095 The extent to which such suggestions are effective is implementation-defined.<sup><a href="#note139"><b>139)</b></a></sup>
7097 Any function with internal linkage can be an inline function. For a function with external
7098 linkage, the following restrictions apply: If a function is declared with an inline
7099 function specifier, then it shall also be defined in the same translation unit. If all of the
7100 file scope declarations for a function in a translation unit include the inline function
7101 specifier without extern, then the definition in that translation unit is an inline
7102 definition. An inline definition does not provide an external definition for the function,
7103 and does not forbid an external definition in another translation unit. An inline definition
7104 provides an alternative to an external definition, which a translator may use to implement
7105 any call to the function in the same translation unit. It is unspecified whether a call to the
7106 function uses the inline definition or the external definition.<sup><a href="#note140"><b>140)</b></a></sup>
7108 A function declared with a _Noreturn function specifier shall not return to its caller.
7111 The implementation should produce a diagnostic message for a function declared with a
7112 _Noreturn function specifier that appears to be capable of returning to its caller.
7114 EXAMPLE 1 The declaration of an inline function with external linkage can result in either an external
7115 definition, or a definition available for use only within the translation unit. A file scope declaration with
7116 extern creates an external definition. The following example shows an entire translation unit.
7117 <pre>
7118 inline double fahr(double t)
7119 {
7121 }
7122 inline double cels(double t)
7123 {
7125 }
7126 extern double fahr(double); // creates an external definition
7127 </pre>
7132 <!--page 145 -->
7133 <pre>
7134 double convert(int is_fahr, double temp)
7135 {
7136 /* A translator may perform inline substitutions */
7137 return is_fahr ? cels(temp) : fahr(temp);
7138 }
7139 </pre>
7141 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
7142 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
7143 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
7144 definition are distinct and either may be used for the call.
7147 EXAMPLE 2
7148 <pre>
7149 _Noreturn void f () {
7150 abort(); // ok
7151 }
7154 }
7155 </pre>
7160 <p><small><a name="note138" href="#note138">138)</a> By using, for example, an alternative to the usual function call mechanism, such as ''inline
7161 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
7162 Therefore, for example, the expansion of a macro used within the body of the function uses the
7163 definition it had at the point the function body appears, and not where the function is called; and
7164 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
7165 single address, regardless of the number of inline definitions that occur in addition to the external
7166 definition.
7167 </small>
7168 <p><small><a name="note139" href="#note139">139)</a> For example, an implementation might never perform inline substitution, or might only perform inline
7169 substitutions to calls in the scope of an inline declaration.
7170 </small>
7171 <p><small><a name="note140" href="#note140">140)</a> Since an inline definition is distinct from the corresponding external definition and from any other
7172 corresponding inline definitions in other translation units, all corresponding objects with static storage
7173 duration are also distinct in each of the definitions.
7174 </small>
7180 <pre>
7181 alignment-specifier:
7182 _Alignas ( type-name )
7183 _Alignas ( constant-expression )
7184 </pre>
7187 An alignment attribute shall not be specified in a declaration of a typedef, or a bit-field, or
7188 a function, or a parameter, or an object declared with the register storage-class
7189 specifier.
7191 The constant expression shall be an integer constant expression. It shall evaluate to a
7192 valid fundamental alignment, or to a valid extended alignment supported by the
7193 implementation in the context in which it appears, or to zero.
7195 The combined effect of all alignment attributes in a declaration shall not specify an
7196 alignment that is less strict than the alignment that would otherwise be required for the
7197 type of the object or member being declared.
7200 The first form is equivalent to _Alignas (_Alignof (type-name)).
7202 The alignment requirement of the declared object or member is taken to be the specified
7203 alignment. An alignment specification of zero has no effect.<sup><a href="#note141"><b>141)</b></a></sup> When multiple
7204 alignment specifiers occur in a declaration, the effective alignment requirement is the
7205 strictest specified alignment.
7206 <!--page 146 -->
7208 If the definition of an object has an alignment specifier, any other declaration of that
7209 object shall either specify equivalent alignment or have no alignment specifier. If the
7210 definition of an object does not have an alignment specifier, any other declaration of that
7211 object shall also have no alignment specifier. If declarations of an object in different
7212 translation units have different alignment specifiers, the behavior is undefined.
7215 <p><small><a name="note141" href="#note141">141)</a> An alignment specification of zero also does not affect other alignment specifications in the same
7216 declaration.
7217 </small>
7223 <pre>
7224 declarator:
7226 direct-declarator:
7227 identifier
7228 ( declarator )
7231 direct-declarator [ type-qualifier-list static assignment-expression ]
7233 direct-declarator ( parameter-type-list )
7235 pointer:
7238 type-qualifier-list:
7239 type-qualifier
7240 type-qualifier-list type-qualifier
7241 parameter-type-list:
7242 parameter-list
7243 parameter-list , ...
7244 parameter-list:
7245 parameter-declaration
7246 parameter-list , parameter-declaration
7247 parameter-declaration:
7248 declaration-specifiers declarator
7250 </pre>
7254 <!--page 147 -->
7255 <pre>
7256 identifier-list:
7257 identifier
7258 identifier-list , identifier
7259 </pre>
7262 Each declarator declares one identifier, and asserts that when an operand of the same
7263 form as the declarator appears in an expression, it designates a function or object with the
7264 scope, storage duration, and type indicated by the declaration specifiers.
7266 A full declarator is a declarator that is not part of another declarator. The end of a full
7267 declarator is a sequence point. If, in the nested sequence of declarators in a full
7268 declarator, there is a declarator specifying a variable length array type, the type specified
7269 by the full declarator is said to be variably modified. Furthermore, any type derived by
7270 declarator type derivation from a variably modified type is itself variably modified.
7272 In the following subclauses, consider a declaration
7273 <pre>
7274 T D1
7275 </pre>
7276 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
7277 a declarator that contains an identifier ident. The type specified for the identifier ident in
7278 the various forms of declarator is described inductively using this notation.
7280 If, in the declaration ''T D1'', D1 has the form
7281 <pre>
7282 identifier
7283 </pre>
7284 then the type specified for ident is T .
7286 If, in the declaration ''T D1'', D1 has the form
7287 <pre>
7288 ( D )
7289 </pre>
7290 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
7291 parentheses is identical to the unparenthesized declarator, but the binding of complicated
7292 declarators may be altered by parentheses.
7295 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of pointer, array, and
7296 function declarators that modify an arithmetic, structure, union, or void type, either
7297 directly or via one or more typedefs.
7298 <p><b> Forward references</b>: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
7299 <!--page 148 -->
7305 If, in the declaration ''T D1'', D1 has the form
7306 <pre>
7308 </pre>
7309 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7310 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
7311 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
7313 For two pointer types to be compatible, both shall be identically qualified and both shall
7314 be pointers to compatible types.
7316 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
7317 to a constant value'' and a ''constant pointer to a variable value''.
7318 <pre>
7319 const int *ptr_to_constant;
7320 int *const constant_ptr;
7321 </pre>
7322 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
7323 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
7324 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
7325 same location.
7327 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
7328 type ''pointer to int''.
7329 <pre>
7330 typedef int *int_ptr;
7331 const int_ptr constant_ptr;
7332 </pre>
7333 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
7340 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
7341 an expression or *. If they delimit an expression (which specifies the size of an array), the
7342 expression shall have an integer type. If the expression is a constant expression, it shall
7343 have a value greater than zero. The element type shall not be an incomplete or function
7344 type. The optional type qualifiers and the keyword static shall appear only in a
7345 declaration of a function parameter with an array type, and then only in the outermost
7346 array type derivation.
7348 If an identifier is declared as having a variably modified type, it shall be an ordinary
7349 identifier (as defined in <a href="#6.2.3">6.2.3</a>), have no linkage, and have either block scope or function
7350 prototype scope. If an identifier is declared to be an object with static or thread storage
7351 duration, it shall not have a variable length array type.
7352 <!--page 149 -->
7355 If, in the declaration ''T D1'', D1 has one of the forms:
7356 <pre>
7359 D[ type-qualifier-list static assignment-expression ]
7361 </pre>
7362 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7363 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note142"><b>142)</b></a></sup>
7364 (See <a href="#6.7.6.3">6.7.6.3</a> for the meaning of the optional type qualifiers and the keyword static.)
7366 If the size is not present, the array type is an incomplete type. If the size is * instead of
7367 being an expression, the array type is a variable length array type of unspecified size,
7368 which can only be used in declarations or type names with function prototype scope;<sup><a href="#note143"><b>143)</b></a></sup>
7369 such arrays are nonetheless complete types. If the size is an integer constant expression
7370 and the element type has a known constant size, the array type is not a variable length
7371 array type; otherwise, the array type is a variable length array type. (Variable length
7372 arrays are a conditional feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.)
7374 If the size is an expression that is not an integer constant expression: if it occurs in a
7375 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
7376 each time it is evaluated it shall have a value greater than zero. The size of each instance
7377 of a variable length array type does not change during its lifetime. Where a size
7378 expression is part of the operand of a sizeof operator and changing the value of the
7379 size expression would not affect the result of the operator, it is unspecified whether or not
7380 the size expression is evaluated.
7382 For two array types to be compatible, both shall have compatible element types, and if
7383 both size specifiers are present, and are integer constant expressions, then both size
7384 specifiers shall have the same constant value. If the two array types are used in a context
7385 which requires them to be compatible, it is undefined behavior if the two size specifiers
7386 evaluate to unequal values.
7388 EXAMPLE 1
7389 <pre>
7391 </pre>
7392 declares an array of float numbers and an array of pointers to float numbers.
7395 EXAMPLE 2 Note the distinction between the declarations
7400 <!--page 150 -->
7401 <pre>
7402 extern int *x;
7403 extern int y[];
7404 </pre>
7405 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
7406 (an incomplete type), the storage for which is defined elsewhere.
7409 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
7410 <pre>
7411 extern int n;
7412 extern int m;
7413 void fcompat(void)
7414 {
7415 int a[n][6][m];
7417 int c[n][n][6][m];
7418 int (*r)[n][n][n+1];
7420 r = c; // compatible, but defined behavior only if
7422 }
7423 </pre>
7426 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
7427 function prototype scope. Array objects declared with the _Thread_local, static, or extern
7428 storage-class specifier cannot have a variable length array (VLA) type. However, an object declared with
7429 the static storage-class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all
7430 identifiers declared with a VM type have to be ordinary identifiers and cannot, therefore, be members of
7431 structures or unions.
7432 <pre>
7433 extern int n;
7434 int A[n]; // invalid: file scope VLA
7435 extern int (*p2)[n]; // invalid: file scope VM
7436 int B[100]; // valid: file scope but not VM
7437 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
7438 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
7439 {
7440 typedef int VLA[m][m]; // valid: block scope typedef VLA
7441 struct tag {
7442 int (*y)[n]; // invalid: y not ordinary identifier
7443 int z[n]; // invalid: z not ordinary identifier
7444 };
7445 int D[m]; // valid: auto VLA
7446 static int E[m]; // invalid: static block scope VLA
7447 extern int F[m]; // invalid: F has linkage and is VLA
7448 int (*s)[m]; // valid: auto pointer to VLA
7449 extern int (*r)[m]; // invalid: r has linkage and points to VLA
7450 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
7451 }
7452 </pre>
7454 <p><b> Forward references</b>: function declarators (<a href="#6.7.6.3">6.7.6.3</a>), function definitions (<a href="#6.9.1">6.9.1</a>),
7456 <!--page 151 -->
7459 <p><small><a name="note142" href="#note142">142)</a> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
7460 </small>
7461 <p><small><a name="note143" href="#note143">143)</a> Thus, * can be used only in function declarations that are not definitions (see <a href="#6.7.6.3">6.7.6.3</a>).
7462 </small>
7465 <h5><a name="6.7.6.3" href="#6.7.6.3">6.7.6.3 Function declarators (including prototypes)</a></h5>
7468 A function declarator shall not specify a return type that is a function type or an array
7469 type.
7471 The only storage-class specifier that shall occur in a parameter declaration is register.
7473 An identifier list in a function declarator that is not part of a definition of that function
7474 shall be empty.
7476 After adjustment, the parameters in a parameter type list in a function declarator that is
7477 part of a definition of that function shall not have incomplete type.
7480 If, in the declaration ''T D1'', D1 has the form
7481 <pre>
7482 D( parameter-type-list )
7483 </pre>
7484 or
7485 <pre>
7487 </pre>
7488 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7489 T '', then the type specified for ident is ''derived-declarator-type-list function returning
7490 T ''.
7492 A parameter type list specifies the types of, and may declare identifiers for, the
7493 parameters of the function.
7495 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
7496 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
7497 array type derivation. If the keyword static also appears within the [ and ] of the
7498 array type derivation, then for each call to the function, the value of the corresponding
7499 actual argument shall provide access to the first element of an array with at least as many
7500 elements as specified by the size expression.
7502 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
7505 If the list terminates with an ellipsis (, ...), no information about the number or types
7508 The special case of an unnamed parameter of type void as the only item in the list
7509 specifies that the function has no parameters.
7513 <!--page 152 -->
7515 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
7516 parameter name, it shall be taken as a typedef name.
7518 If the function declarator is not part of a definition of that function, parameters may have
7519 incomplete type and may use the [*] notation in their sequences of declarator specifiers
7520 to specify variable length array types.
7522 The storage-class specifier in the declaration specifiers for a parameter declaration, if
7523 present, is ignored unless the declared parameter is one of the members of the parameter
7524 type list for a function definition.
7526 An identifier list declares only the identifiers of the parameters of the function. An empty
7527 list in a function declarator that is part of a definition of that function specifies that the
7528 function has no parameters. The empty list in a function declarator that is not part of a
7529 definition of that function specifies that no information about the number or types of the
7532 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note146"><b>146)</b></a></sup>
7533 Moreover, the parameter type lists, if both are present, shall agree in the number of
7534 parameters and in use of the ellipsis terminator; corresponding parameters shall have
7535 compatible types. If one type has a parameter type list and the other type is specified by a
7536 function declarator that is not part of a function definition and that contains an empty
7537 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
7538 parameter shall be compatible with the type that results from the application of the
7539 default argument promotions. If one type has a parameter type list and the other type is
7540 specified by a function definition that contains a (possibly empty) identifier list, both shall
7541 agree in the number of parameters, and the type of each prototype parameter shall be
7542 compatible with the type that results from the application of the default argument
7543 promotions to the type of the corresponding identifier. (In the determination of type
7544 compatibility and of a composite type, each parameter declared with function or array
7545 type is taken as having the adjusted type and each parameter declared with qualified type
7546 is taken as having the unqualified version of its declared type.)
7548 EXAMPLE 1 The declaration
7549 <pre>
7550 int f(void), *fip(), (*pfi)();
7551 </pre>
7552 declares a function f with no parameters returning an int, a function fip with no parameter specification
7553 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
7554 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
7555 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
7556 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
7557 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
7560 <!--page 153 -->
7561 designator, which is then used to call the function; it returns an int.
7563 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
7564 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
7565 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
7566 the identifier of the pointer pfi has block scope and no linkage.
7569 EXAMPLE 2 The declaration
7570 <pre>
7571 int (*apfi[3])(int *x, int *y);
7572 </pre>
7573 declares an array apfi of three pointers to functions returning int. Each of these functions has two
7574 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
7575 go out of scope at the end of the declaration of apfi.
7578 EXAMPLE 3 The declaration
7579 <pre>
7580 int (*fpfi(int (*)(long), int))(int, ...);
7581 </pre>
7582 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
7583 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
7584 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
7585 additional arguments of any type.
7588 EXAMPLE 4 The following prototype has a variably modified parameter.
7589 <pre>
7590 void addscalar(int n, int m,
7591 double a[n][n*m+300], double x);
7592 int main()
7593 {
7596 return 0;
7597 }
7598 void addscalar(int n, int m,
7599 double a[n][n*m+300], double x)
7600 {
7603 // a is a pointer to a VLA with n*m+300 elements
7604 a[i][j] += x;
7605 }
7606 </pre>
7609 EXAMPLE 5 The following are all compatible function prototype declarators.
7610 <pre>
7611 double maximum(int n, int m, double a[n][m]);
7612 double maximum(int n, int m, double a[*][*]);
7613 double maximum(int n, int m, double a[ ][*]);
7614 double maximum(int n, int m, double a[ ][m]);
7615 </pre>
7616 as are:
7617 <!--page 154 -->
7618 <pre>
7619 void f(double (* restrict a)[5]);
7620 void f(double a[restrict][5]);
7623 </pre>
7624 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
7625 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
7627 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>), type names (<a href="#6.7.7">6.7.7</a>).
7630 <p><small><a name="note144" href="#note144">144)</a> The macros defined in the <a href="#7.16"><stdarg.h></a> header (<a href="#7.16">7.16</a>) may be used to access arguments that
7631 correspond to the ellipsis.
7632 </small>
7633 <p><small><a name="note145" href="#note145">145)</a> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
7634 </small>
7635 <p><small><a name="note146" href="#note146">146)</a> If both function types are ''old style'', parameter types are not compared.
7636 </small>
7642 <pre>
7643 type-name:
7645 abstract-declarator:
7646 pointer
7648 direct-abstract-declarator:
7649 ( abstract-declarator )
7653 assignment-expression ]
7655 assignment-expression ]
7658 </pre>
7661 In several contexts, it is necessary to specify a type. This is accomplished using a type
7662 name, which is syntactically a declaration for a function or an object of that type that
7665 EXAMPLE The constructions
7666 <pre>
7667 (a) int
7668 (b) int *
7669 (c) int *[3]
7670 (d) int (*)[3]
7671 (e) int (*)[*]
7672 (f) int *()
7673 (g) int (*)(void)
7674 (h) int (*const [])(unsigned int, ...)
7675 </pre>
7676 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
7677 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
7678 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
7681 <!--page 155 -->
7682 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
7683 parameter that has type unsigned int and an unspecified number of other parameters, returning an
7684 int.
7688 <p><small><a name="note147" href="#note147">147)</a> As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
7689 parameter specification'', rather than redundant parentheses around the omitted identifier.
7690 </small>
7696 <pre>
7697 typedef-name:
7698 identifier
7699 </pre>
7702 If a typedef name specifies a variably modified type then it shall have block scope.
7705 In a declaration whose storage-class specifier is typedef, each declarator defines an
7706 identifier to be a typedef name that denotes the type specified for the identifier in the way
7707 described in <a href="#6.7.6">6.7.6</a>. Any array size expressions associated with variable length array
7708 declarators are evaluated each time the declaration of the typedef name is reached in the
7709 order of execution. A typedef declaration does not introduce a new type, only a
7710 synonym for the type so specified. That is, in the following declarations:
7711 <pre>
7712 typedef T type_ident;
7713 type_ident D;
7714 </pre>
7715 type_ident is defined as a typedef name with the type specified by the declaration
7716 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
7717 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
7718 typedef name shares the same name space as other identifiers declared in ordinary
7719 declarators.
7721 EXAMPLE 1 After
7722 <pre>
7723 typedef int MILES, KLICKSP();
7724 typedef struct { double hi, lo; } range;
7725 </pre>
7726 the constructions
7727 <pre>
7728 MILES distance;
7729 extern KLICKSP *metricp;
7730 range x;
7731 range z, *zp;
7732 </pre>
7733 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
7734 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
7735 such a structure. The object distance has a type compatible with any other int object.
7738 EXAMPLE 2 After the declarations
7739 <pre>
7740 typedef struct s1 { int x; } t1, *tp1;
7741 typedef struct s2 { int x; } t2, *tp2;
7742 </pre>
7743 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
7744 <!--page 156 -->
7745 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
7748 EXAMPLE 3 The following obscure constructions
7749 <pre>
7750 typedef signed int t;
7751 typedef int plain;
7752 struct tag {
7753 unsigned t:4;
7754 const t:5;
7755 plain r:5;
7756 };
7757 </pre>
7758 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
7759 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
7760 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
7761 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
7762 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
7763 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
7764 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
7765 in an inner scope by
7766 <pre>
7767 t f(t (t));
7768 long t;
7769 </pre>
7770 then a function f is declared with type ''function returning signed int with one unnamed parameter
7771 with type pointer to function returning signed int with one unnamed parameter with type signed
7772 int'', and an identifier t with type long int.
7775 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
7776 following declarations of the signal function specify exactly the same type, the first without making use
7777 of any typedef names.
7778 <pre>
7779 typedef void fv(int), (*pfv)(int);
7780 void (*signal(int, void (*)(int)))(int);
7781 fv *signal(int, fv *);
7782 pfv signal(int, pfv);
7783 </pre>
7786 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
7787 time the typedef name is defined, not each time it is used:
7788 <!--page 157 -->
7789 <pre>
7790 void copyt(int n)
7791 {
7792 typedef int B[n]; // B is n ints, n evaluated now
7793 n += 1;
7794 B a; // a is n ints, n without += 1
7795 int b[n]; // a and b are different sizes
7797 a[i-1] = b[i];
7798 }
7799 </pre>
7805 <pre>
7806 initializer:
7807 assignment-expression
7808 { initializer-list }
7809 { initializer-list , }
7810 initializer-list:
7813 designation:
7814 designator-list =
7815 designator-list:
7816 designator
7817 designator-list designator
7818 designator:
7819 [ constant-expression ]
7820 . identifier
7821 </pre>
7824 No initializer shall attempt to provide a value for an object not contained within the entity
7825 being initialized.
7827 The type of the entity to be initialized shall be an array of unknown size or a complete
7828 object type that is not a variable length array type.
7830 All the expressions in an initializer for an object that has static or thread storage duration
7831 shall be constant expressions or string literals.
7833 If the declaration of an identifier has block scope, and the identifier has external or
7834 internal linkage, the declaration shall have no initializer for the identifier.
7836 If a designator has the form
7837 <pre>
7838 [ constant-expression ]
7839 </pre>
7840 then the current object (defined below) shall have array type and the expression shall be
7841 an integer constant expression. If the array is of unknown size, any nonnegative value is
7842 valid.
7844 If a designator has the form
7845 <pre>
7846 . identifier
7847 </pre>
7848 then the current object (defined below) shall have structure or union type and the
7849 identifier shall be the name of a member of that type.
7850 <!--page 158 -->
7853 An initializer specifies the initial value stored in an object.
7855 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
7856 members of objects of structure and union type do not participate in initialization.
7857 Unnamed members of structure objects have indeterminate value even after initialization.
7859 If an object that has automatic storage duration is not initialized explicitly, its value is
7860 indeterminate. If an object that has static or thread storage duration is not initialized
7861 explicitly, then:
7862 <ul>
7863 <li> if it has pointer type, it is initialized to a null pointer;
7864 <li> if it has arithmetic type, it is initialized to (positive or unsigned) zero;
7865 <li> if it is an aggregate, every member is initialized (recursively) according to these rules,
7866 and any padding is initialized to zero bits;
7867 <li> if it is a union, the first named member is initialized (recursively) according to these
7868 rules, and any padding is initialized to zero bits;
7869 </ul>
7871 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
7872 initial value of the object is that of the expression (after conversion); the same type
7873 constraints and conversions as for simple assignment apply, taking the type of the scalar
7874 to be the unqualified version of its declared type.
7876 The rest of this subclause deals with initializers for objects that have aggregate or union
7877 type.
7879 The initializer for a structure or union object that has automatic storage duration shall be
7880 either an initializer list as described below, or a single expression that has compatible
7881 structure or union type. In the latter case, the initial value of the object, including
7882 unnamed members, is that of the expression.
7884 An array of character type may be initialized by a character string literal or UTF-8 string
7885 literal, optionally enclosed in braces. Successive bytes of the string literal (including the
7886 terminating null character if there is room or if the array is of unknown size) initialize the
7887 elements of the array.
7889 An array with element type compatible with a qualified or unqualified version of
7890 wchar_t, char16_t, or char32_t may be initialized by a wide string literal with
7891 the corresponding encoding prefix (L, u, or U, respectively), optionally enclosed in
7892 braces. Successive wide characters of the wide string literal (including the terminating
7893 null wide character if there is room or if the array is of unknown size) initialize the
7894 elements of the array.
7896 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
7897 enclosed list of initializers for the elements or named members.
7898 <!--page 159 -->
7900 Each brace-enclosed initializer list has an associated current object. When no
7901 designations are present, subobjects of the current object are initialized in order according
7902 to the type of the current object: array elements in increasing subscript order, structure
7903 members in declaration order, and the first named member of a union.<sup><a href="#note148"><b>148)</b></a></sup> In contrast, a
7904 designation causes the following initializer to begin initialization of the subobject
7905 described by the designator. Initialization then continues forward in order, beginning
7906 with the next subobject after that described by the designator.<sup><a href="#note149"><b>149)</b></a></sup>
7908 Each designator list begins its description with the current object associated with the
7909 closest surrounding brace pair. Each item in the designator list (in order) specifies a
7910 particular member of its current object and changes the current object for the next
7911 designator (if any) to be that member.<sup><a href="#note150"><b>150)</b></a></sup> The current object that results at the end of the
7912 designator list is the subobject to be initialized by the following initializer.
7914 The initialization shall occur in initializer list order, each initializer provided for a
7915 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note151"><b>151)</b></a></sup>
7916 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
7917 objects that have static storage duration.
7919 If the aggregate or union contains elements or members that are aggregates or unions,
7920 these rules apply recursively to the subaggregates or contained unions. If the initializer of
7921 a subaggregate or contained union begins with a left brace, the initializers enclosed by
7922 that brace and its matching right brace initialize the elements or members of the
7923 subaggregate or the contained union. Otherwise, only enough initializers from the list are
7924 taken to account for the elements or members of the subaggregate or the first member of
7925 the contained union; any remaining initializers are left to initialize the next element or
7926 member of the aggregate of which the current subaggregate or contained union is a part.
7928 If there are fewer initializers in a brace-enclosed list than there are elements or members
7929 of an aggregate, or fewer characters in a string literal used to initialize an array of known
7930 size than there are elements in the array, the remainder of the aggregate shall be
7931 initialized implicitly the same as objects that have static storage duration.
7935 <!--page 160 -->
7937 If an array of unknown size is initialized, its size is determined by the largest indexed
7938 element with an explicit initializer. The array type is completed at the end of its
7939 initializer list.
7941 The evaluations of the initialization list expressions are indeterminately sequenced with
7942 respect to one another and thus the order in which any side effects occur is
7945 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
7946 <pre>
7949 </pre>
7953 EXAMPLE 2 The declaration
7954 <pre>
7956 </pre>
7957 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
7958 and there are three initializers.
7961 EXAMPLE 3 The declaration
7962 <pre>
7967 };
7968 </pre>
7969 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
7971 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
7972 been achieved by
7973 <pre>
7976 };
7977 </pre>
7978 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
7982 EXAMPLE 4 The declaration
7983 <pre>
7986 };
7987 </pre>
7988 initializes the first column of z as specified and initializes the rest with zeros.
7991 EXAMPLE 5 The declaration
7992 <pre>
7994 </pre>
7995 is a definition with an inconsistently bracketed initialization. It defines an array with two element
7999 <!--page 161 -->
8003 EXAMPLE 6 The declaration
8004 <pre>
8006 { 1 },
8009 };
8010 </pre>
8011 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
8013 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
8014 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
8015 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
8016 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
8017 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
8018 diagnostic message would have been issued. The same initialization result could have been achieved by:
8019 <pre>
8024 };
8025 </pre>
8026 or by:
8027 <pre>
8029 {
8030 { 1 },
8031 },
8032 {
8034 },
8035 {
8037 { 6 },
8038 }
8039 };
8040 </pre>
8041 in a fully bracketed form.
8043 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
8044 cause confusion.
8047 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
8048 declaration
8049 <pre>
8050 typedef int A[]; // OK - declared with block scope
8051 </pre>
8052 the declaration
8053 <pre>
8055 </pre>
8056 is identical to
8057 <pre>
8059 </pre>
8060 due to the rules for incomplete types.
8061 <!--page 162 -->
8063 EXAMPLE 8 The declaration
8064 <pre>
8066 </pre>
8067 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
8068 This declaration is identical to
8069 <pre>
8070 char s[] = { 'a', 'b', 'c', '\0' },
8071 t[] = { 'a', 'b', 'c' };
8072 </pre>
8073 The contents of the arrays are modifiable. On the other hand, the declaration
8074 <pre>
8075 char *p = "abc";
8076 </pre>
8077 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
8078 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
8079 modify the contents of the array, the behavior is undefined.
8082 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
8083 designators:
8084 <pre>
8085 enum { member_one, member_two };
8086 const char *nm[] = {
8087 [member_two] = "member two",
8088 [member_one] = "member one",
8089 };
8090 </pre>
8093 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
8094 <pre>
8096 </pre>
8099 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
8100 might be misunderstood:
8101 <pre>
8102 struct { int a[3], b; } w[] =
8104 </pre>
8107 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
8108 <pre>
8109 int a[MAX] = {
8111 };
8112 </pre>
8114 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
8115 than ten, some of the values provided by the first five initializers will be overridden by the second five.
8118 EXAMPLE 13 Any member of a union can be initialized:
8119 <pre>
8120 union { /* ... */ } u = { .any_member = 42 };
8121 </pre>
8123 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>).
8124 <!--page 163 -->
8127 <p><small><a name="note148" href="#note148">148)</a> If the initializer list for a subaggregate or contained union does not begin with a left brace, its
8128 subobjects are initialized as usual, but the subaggregate or contained union does not become the
8129 current object: current objects are associated only with brace-enclosed initializer lists.
8130 </small>
8131 <p><small><a name="note149" href="#note149">149)</a> After a union member is initialized, the next object is not the next member of the union; instead, it is
8132 the next subobject of an object containing the union.
8133 </small>
8134 <p><small><a name="note150" href="#note150">150)</a> Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with
8135 the surrounding brace pair. Note, too, that each separate designator list is independent.
8136 </small>
8137 <p><small><a name="note151" href="#note151">151)</a> Any initializer for the subobject which is overridden and so not used to initialize that subobject might
8138 not be evaluated at all.
8139 </small>
8140 <p><small><a name="note152" href="#note152">152)</a> In particular, the evaluation order need not be the same as the order of subobject initialization.
8141 </small>
8147 <pre>
8148 static_assert-declaration:
8149 _Static_assert ( constant-expression , string-literal ) ;
8150 </pre>
8153 The constant expression shall compare unequal to 0.
8156 The constant expression shall be an integer constant expression. If the value of the
8157 constant expression compares unequal to 0, the declaration has no effect. Otherwise, the
8158 constraint is violated and the implementation shall produce a diagnostic message that
8159 includes the text of the string literal, except that characters not in the basic source
8160 character set are not required to appear in the message.
8162 <!--page 164 -->
8168 <pre>
8169 statement:
8170 labeled-statement
8171 compound-statement
8172 expression-statement
8173 selection-statement
8174 iteration-statement
8175 jump-statement
8176 </pre>
8179 A statement specifies an action to be performed. Except as indicated, statements are
8180 executed in sequence.
8182 A block allows a set of declarations and statements to be grouped into one syntactic unit.
8183 The initializers of objects that have automatic storage duration, and the variable length
8184 array declarators of ordinary identifiers with block scope, are evaluated and the values are
8185 stored in the objects (including storing an indeterminate value in objects without an
8186 initializer) each time the declaration is reached in the order of execution, as if it were a
8187 statement, and within each declaration in the order that declarators appear.
8189 A full expression is an expression that is not part of another expression or of a declarator.
8190 Each of the following is a full expression: an initializer that is not part of a compound
8191 literal; the expression in an expression statement; the controlling expression of a selection
8192 statement (if or switch); the controlling expression of a while or do statement; each
8193 of the (optional) expressions of a for statement; the (optional) expression in a return
8194 statement. There is a sequence point between the evaluation of a full expression and the
8195 evaluation of the next full expression to be evaluated.
8196 <p><b> Forward references</b>: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
8197 (<a href="#6.8.4">6.8.4</a>), iteration statements (<a href="#6.8.5">6.8.5</a>), the return statement (<a href="#6.8.6.4">6.8.6.4</a>).
8203 <pre>
8204 labeled-statement:
8205 identifier : statement
8206 case constant-expression : statement
8207 default : statement
8208 </pre>
8211 A case or default label shall appear only in a switch statement. Further
8212 constraints on such labels are discussed under the switch statement.
8213 <!--page 165 -->
8215 Label names shall be unique within a function.
8218 Any statement may be preceded by a prefix that declares an identifier as a label name.
8219 Labels in themselves do not alter the flow of control, which continues unimpeded across
8220 them.
8221 <p><b> Forward references</b>: the goto statement (<a href="#6.8.6.1">6.8.6.1</a>), the switch statement (<a href="#6.8.4.2">6.8.4.2</a>).
8227 <pre>
8228 compound-statement:
8230 block-item-list:
8231 block-item
8232 block-item-list block-item
8233 block-item:
8234 declaration
8235 statement
8236 </pre>
8239 A compound statement is a block.
8245 <pre>
8246 expression-statement:
8248 </pre>
8251 The expression in an expression statement is evaluated as a void expression for its side
8254 A null statement (consisting of just a semicolon) performs no operations.
8256 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
8257 discarding of its value may be made explicit by converting the expression to a void expression by means of
8258 a cast:
8259 <pre>
8260 int p(int);
8261 /* ... */
8262 (void)p(0);
8263 </pre>
8267 <!--page 166 -->
8269 EXAMPLE 2 In the program fragment
8270 <pre>
8271 char *s;
8272 /* ... */
8273 while (*s++ != '\0')
8274 ;
8275 </pre>
8276 a null statement is used to supply an empty loop body to the iteration statement.
8279 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
8280 statement.
8281 <pre>
8282 while (loop1) {
8283 /* ... */
8284 while (loop2) {
8285 /* ... */
8286 if (want_out)
8287 goto end_loop1;
8288 /* ... */
8289 }
8290 /* ... */
8291 end_loop1: ;
8292 }
8293 </pre>
8298 <p><small><a name="note153" href="#note153">153)</a> Such as assignments, and function calls which have side effects.
8299 </small>
8305 <pre>
8306 selection-statement:
8307 if ( expression ) statement
8308 if ( expression ) statement else statement
8309 switch ( expression ) statement
8310 </pre>
8313 A selection statement selects among a set of statements depending on the value of a
8314 controlling expression.
8316 A selection statement is a block whose scope is a strict subset of the scope of its
8317 enclosing block. Each associated substatement is also a block whose scope is a strict
8318 subset of the scope of the selection statement.
8324 The controlling expression of an if statement shall have scalar type.
8327 In both forms, the first substatement is executed if the expression compares unequal to 0.
8328 In the else form, the second substatement is executed if the expression compares equal
8329 <!--page 167 -->
8330 to 0. If the first substatement is reached via a label, the second substatement is not
8331 executed.
8333 An else is associated with the lexically nearest preceding if that is allowed by the
8334 syntax.
8340 The controlling expression of a switch statement shall have integer type.
8342 If a switch statement has an associated case or default label within the scope of an
8343 identifier with a variably modified type, the entire switch statement shall be within the
8346 The expression of each case label shall be an integer constant expression and no two of
8347 the case constant expressions in the same switch statement shall have the same value
8348 after conversion. There may be at most one default label in a switch statement.
8349 (Any enclosed switch statement may have a default label or case constant
8350 expressions with values that duplicate case constant expressions in the enclosing
8351 switch statement.)
8354 A switch statement causes control to jump to, into, or past the statement that is the
8355 switch body, depending on the value of a controlling expression, and on the presence of a
8356 default label and the values of any case labels on or in the switch body. A case or
8357 default label is accessible only within the closest enclosing switch statement.
8359 The integer promotions are performed on the controlling expression. The constant
8360 expression in each case label is converted to the promoted type of the controlling
8361 expression. If a converted value matches that of the promoted controlling expression,
8362 control jumps to the statement following the matched case label. Otherwise, if there is
8363 a default label, control jumps to the labeled statement. If no converted case constant
8364 expression matches and there is no default label, no part of the switch body is
8365 executed.
8368 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, the implementation may limit the number of case values in a
8369 switch statement.
8374 <!--page 168 -->
8376 EXAMPLE In the artificial program fragment
8377 <pre>
8378 switch (expr)
8379 {
8380 int i = 4;
8381 f(i);
8382 case 0:
8383 i = 17;
8384 /* falls through into default code */
8385 default:
8386 printf("%d\n", i);
8387 }
8388 </pre>
8389 the object whose identifier is i exists with automatic storage duration (within the block) but is never
8390 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
8391 access an indeterminate value. Similarly, the call to the function f cannot be reached.
8395 <p><small><a name="note154" href="#note154">154)</a> That is, the declaration either precedes the switch statement, or it follows the last case or
8396 default label associated with the switch that is in the block containing the declaration.
8397 </small>
8403 <pre>
8404 iteration-statement:
8405 while ( expression ) statement
8406 do statement while ( expression ) ;
8407 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
8409 </pre>
8412 The controlling expression of an iteration statement shall have scalar type.
8414 The declaration part of a for statement shall only declare identifiers for objects having
8415 storage class auto or register.
8418 An iteration statement causes a statement called the loop body to be executed repeatedly
8419 until the controlling expression compares equal to 0. The repetition occurs regardless of
8420 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note155"><b>155)</b></a></sup>
8422 An iteration statement is a block whose scope is a strict subset of the scope of its
8423 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
8424 of the iteration statement.
8426 An iteration statement whose controlling expression is not a constant expression,<sup><a href="#note156"><b>156)</b></a></sup> that
8427 performs no input/output operations, does not access volatile objects, and performs no
8428 synchronization or atomic operations in its body, controlling expression, or (in the case of
8430 <!--page 169 -->
8431 a for statement) its expression-3, may be assumed by the implementation to
8435 <p><small><a name="note155" href="#note155">155)</a> Code jumped over is not executed. In particular, the controlling expression of a for or while
8436 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
8437 </small>
8438 <p><small><a name="note156" href="#note156">156)</a> An omitted controlling expression is replaced by a nonzero constant, which is a constant expression.
8439 </small>
8440 <p><small><a name="note157" href="#note157">157)</a> This is intended to allow compiler transformations such as removal of empty loops even when
8441 termination cannot be proven.
8442 </small>
8447 The evaluation of the controlling expression takes place before each execution of the loop
8448 body.
8453 The evaluation of the controlling expression takes place after each execution of the loop
8454 body.
8459 The statement
8460 <pre>
8462 </pre>
8463 behaves as follows: The expression expression-2 is the controlling expression that is
8464 evaluated before each execution of the loop body. The expression expression-3 is
8465 evaluated as a void expression after each execution of the loop body. If clause-1 is a
8466 declaration, the scope of any identifiers it declares is the remainder of the declaration and
8467 the entire loop, including the other two expressions; it is reached in the order of execution
8468 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
8469 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note158"><b>158)</b></a></sup>
8472 nonzero constant.
8475 <p><small><a name="note158" href="#note158">158)</a> Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in
8476 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
8477 such that execution of the loop continues until the expression compares equal to 0; and expression-3
8478 specifies an operation (such as incrementing) that is performed after each iteration.
8479 </small>
8485 <pre>
8486 jump-statement:
8487 goto identifier ;
8488 continue ;
8489 break ;
8491 </pre>
8496 <!--page 170 -->
8499 A jump statement causes an unconditional jump to another place.
8505 The identifier in a goto statement shall name a label located somewhere in the enclosing
8506 function. A goto statement shall not jump from outside the scope of an identifier having
8507 a variably modified type to inside the scope of that identifier.
8510 A goto statement causes an unconditional jump to the statement prefixed by the named
8511 label in the enclosing function.
8513 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
8514 following outline presents one possible approach to a problem based on these three assumptions:
8515 <ol>
8516 <li> The general initialization code accesses objects only visible to the current function.
8517 <li> The general initialization code is too large to warrant duplication.
8518 <li> The code to determine the next operation is at the head of the loop. (To allow it to be reached by
8519 continue statements, for example.)
8520 <!--page 171 -->
8521 <pre>
8522 /* ... */
8523 goto first_time;
8524 for (;;) {
8525 // determine next operation
8526 /* ... */
8527 if (need to reinitialize) {
8528 // reinitialize-only code
8529 /* ... */
8530 first_time:
8531 // general initialization code
8532 /* ... */
8533 continue;
8534 }
8535 // handle other operations
8536 /* ... */
8537 }
8538 </pre>
8539 </ol>
8541 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
8542 modified types. A jump within the scope, however, is permitted.
8543 <pre>
8544 goto lab3; // invalid: going INTO scope of VLA.
8545 {
8546 double a[n];
8548 lab3:
8550 goto lab4; // valid: going WITHIN scope of VLA.
8552 lab4:
8554 }
8555 goto lab4; // invalid: going INTO scope of VLA.
8556 </pre>
8563 A continue statement shall appear only in or as a loop body.
8566 A continue statement causes a jump to the loop-continuation portion of the smallest
8567 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
8568 of the statements
8569 while (/* ... */) { do { for (/* ... */) {
8570 <pre>
8571 /* ... */ /* ... */ /* ... */
8572 continue; continue; continue;
8573 /* ... */ /* ... */ /* ... */
8574 </pre>
8575 contin: ; contin: ; contin: ;
8576 } } while (/* ... */); }
8577 unless the continue statement shown is in an enclosed iteration statement (in which
8578 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note159"><b>159)</b></a></sup>
8581 <p><small><a name="note159" href="#note159">159)</a> Following the contin: label is a null statement.
8582 </small>
8588 A break statement shall appear only in or as a switch body or loop body.
8591 A break statement terminates execution of the smallest enclosing switch or iteration
8592 statement.
8596 <!--page 172 -->
8602 A return statement with an expression shall not appear in a function whose return type
8603 is void. A return statement without an expression shall only appear in a function
8604 whose return type is void.
8607 A return statement terminates execution of the current function and returns control to
8608 its caller. A function may have any number of return statements.
8610 If a return statement with an expression is executed, the value of the expression is
8611 returned to the caller as the value of the function call expression. If the expression has a
8612 type different from the return type of the function in which it appears, the value is
8613 converted as if by assignment to an object having the return type of the function.<sup><a href="#note160"><b>160)</b></a></sup>
8615 EXAMPLE In:
8616 <pre>
8617 struct s { double i; } f(void);
8618 union {
8619 struct {
8620 int f1;
8621 struct s f2;
8622 } u1;
8623 struct {
8624 struct s f3;
8625 int f4;
8626 } u2;
8627 } g;
8628 struct s f(void)
8629 {
8630 return g.u1.f2;
8631 }
8632 /* ... */
8633 g.u2.f3 = f();
8634 </pre>
8635 there is no undefined behavior, although there would be if the assignment were done directly (without using
8636 a function call to fetch the value).
8641 <!--page 173 -->
8644 <p><small><a name="note160" href="#note160">160)</a> The return statement is not an assignment. The overlap restriction of subclause <a href="#6.5.16.1">6.5.16.1</a> does not
8645 apply to the case of function return. The representation of floating-point values may have wider range
8646 or precision than implied by the type; a cast may be used to remove this extra range and precision.
8647 </small>
8653 <pre>
8654 translation-unit:
8655 external-declaration
8656 translation-unit external-declaration
8657 external-declaration:
8658 function-definition
8659 declaration
8660 </pre>
8663 The storage-class specifiers auto and register shall not appear in the declaration
8664 specifiers in an external declaration.
8666 There shall be no more than one external definition for each identifier declared with
8667 internal linkage in a translation unit. Moreover, if an identifier declared with internal
8668 linkage is used in an expression (other than as a part of the operand of a sizeof or
8669 _Alignof operator whose result is an integer constant), there shall be exactly one
8670 external definition for the identifier in the translation unit.
8673 As discussed in <a href="#5.1.1.1">5.1.1.1</a>, the unit of program text after preprocessing is a translation unit,
8674 which consists of a sequence of external declarations. These are described as ''external''
8675 because they appear outside any function (and hence have file scope). As discussed in
8676 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
8677 by the identifier is a definition.
8679 An external definition is an external declaration that is also a definition of a function
8680 (other than an inline definition) or an object. If an identifier declared with external
8681 linkage is used in an expression (other than as part of the operand of a sizeof or
8682 _Alignof operator whose result is an integer constant), somewhere in the entire
8683 program there shall be exactly one external definition for the identifier; otherwise, there
8689 <!--page 174 -->
8692 <p><small><a name="note161" href="#note161">161)</a> Thus, if an identifier declared with external linkage is not used in an expression, there need be no
8693 external definition for it.
8694 </small>
8700 <pre>
8701 function-definition:
8703 declaration-list:
8704 declaration
8705 declaration-list declaration
8706 </pre>
8709 The identifier declared in a function definition (which is the name of the function) shall
8710 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note162"><b>162)</b></a></sup>
8712 The return type of a function shall be void or a complete object type other than array
8713 type.
8715 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
8716 static.
8718 If the declarator includes a parameter type list, the declaration of each parameter shall
8719 include an identifier, except for the special case of a parameter list consisting of a single
8720 parameter of type void, in which case there shall not be an identifier. No declaration list
8721 shall follow.
8723 If the declarator includes an identifier list, each declaration in the declaration list shall
8724 have at least one declarator, those declarators shall declare only identifiers from the
8725 identifier list, and every identifier in the identifier list shall be declared. An identifier
8726 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
8727 declaration list shall contain no storage-class specifier other than register and no
8728 initializations.
8732 <!--page 175 -->
8735 The declarator in a function definition specifies the name of the function being defined
8736 and the identifiers of its parameters. If the declarator includes a parameter type list, the
8737 list also specifies the types of all the parameters; such a declarator also serves as a
8738 function prototype for later calls to the same function in the same translation unit. If the
8739 declarator includes an identifier list,<sup><a href="#note163"><b>163)</b></a></sup> the types of the parameters shall be declared in a
8740 following declaration list. In either case, the type of each parameter is adjusted as
8741 described in <a href="#6.7.6.3">6.7.6.3</a> for a parameter type list; the resulting type shall be a complete object
8742 type.
8744 If a function that accepts a variable number of arguments is defined without a parameter
8745 type list that ends with the ellipsis notation, the behavior is undefined.
8747 Each parameter has automatic storage duration; its identifier is an lvalue.<sup><a href="#note164"><b>164)</b></a></sup> The layout
8748 of the storage for parameters is unspecified.
8750 On entry to the function, the size expressions of each variably modified parameter are
8751 evaluated and the value of each argument expression is converted to the type of the
8752 corresponding parameter as if by assignment. (Array expressions and function
8753 designators as arguments were converted to pointers before the call.)
8755 After all parameters have been assigned, the compound statement that constitutes the
8756 body of the function definition is executed.
8758 If the } that terminates a function is reached, and the value of the function call is used by
8759 the caller, the behavior is undefined.
8761 EXAMPLE 1 In the following:
8762 <pre>
8763 extern int max(int a, int b)
8764 {
8765 return a > b ? a : b;
8766 }
8767 </pre>
8768 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
8769 function declarator; and
8770 <pre>
8771 { return a > b ? a : b; }
8772 </pre>
8773 is the function body. The following similar definition uses the identifier-list form for the parameter
8774 declarations:
8779 <!--page 176 -->
8780 <pre>
8781 extern int max(a, b)
8782 int a, b;
8783 {
8784 return a > b ? a : b;
8785 }
8786 </pre>
8787 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
8788 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
8789 to the function, whereas the second form does not.
8792 EXAMPLE 2 To pass one function to another, one might say
8793 <pre>
8794 int f(void);
8795 /* ... */
8796 g(f);
8797 </pre>
8798 Then the definition of g might read
8799 <pre>
8800 void g(int (*funcp)(void))
8801 {
8802 /* ... */
8803 (*funcp)(); /* or funcp(); ... */
8804 }
8805 </pre>
8806 or, equivalently,
8807 <pre>
8808 void g(int func(void))
8809 {
8810 /* ... */
8811 func(); /* or (*func)(); ... */
8812 }
8813 </pre>
8817 <p><small><a name="note162" href="#note162">162)</a> The intent is that the type category in a function definition cannot be inherited from a typedef:
8819 <pre>
8820 typedef int F(void); // type F is ''function with no parameters
8821 // returning int''
8822 F f, g; // f and g both have type compatible with F
8823 F f { /* ... */ } // WRONG: syntax/constraint error
8824 F g() { /* ... */ } // WRONG: declares that g returns a function
8825 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
8826 int g() { /* ... */ } // RIGHT: g has type compatible with F
8827 F *e(void) { /* ... */ } // e returns a pointer to a function
8828 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
8829 int (*fp)(void); // fp points to a function that has type F
8830 F *Fp; // Fp points to a function that has type F
8831 </pre>
8832 </small>
8833 <p><small><a name="note163" href="#note163">163)</a> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
8834 </small>
8835 <p><small><a name="note164" href="#note164">164)</a> A parameter identifier cannot be redeclared in the function body except in an enclosed block.
8836 </small>
8842 If the declaration of an identifier for an object has file scope and an initializer, the
8843 declaration is an external definition for the identifier.
8845 A declaration of an identifier for an object that has file scope without an initializer, and
8846 without a storage-class specifier or with the storage-class specifier static, constitutes a
8847 tentative definition. If a translation unit contains one or more tentative definitions for an
8848 identifier, and the translation unit contains no external definition for that identifier, then
8849 the behavior is exactly as if the translation unit contains a file scope declaration of that
8850 identifier, with the composite type as of the end of the translation unit, with an initializer
8851 equal to 0.
8853 If the declaration of an identifier for an object is a tentative definition and has internal
8854 linkage, the declared type shall not be an incomplete type.
8855 <!--page 177 -->
8857 EXAMPLE 1
8858 <pre>
8859 int i1 = 1; // definition, external linkage
8860 static int i2 = 2; // definition, internal linkage
8861 extern int i3 = 3; // definition, external linkage
8862 int i4; // tentative definition, external linkage
8863 static int i5; // tentative definition, internal linkage
8864 int i1; // valid tentative definition, refers to previous
8866 int i3; // valid tentative definition, refers to previous
8867 int i4; // valid tentative definition, refers to previous
8869 extern int i1; // refers to previous, whose linkage is external
8870 extern int i2; // refers to previous, whose linkage is internal
8871 extern int i3; // refers to previous, whose linkage is external
8872 extern int i4; // refers to previous, whose linkage is external
8873 extern int i5; // refers to previous, whose linkage is internal
8874 </pre>
8877 EXAMPLE 2 If at the end of the translation unit containing
8878 <pre>
8879 int i[];
8880 </pre>
8881 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
8882 zero on program startup.
8883 <!--page 178 -->
8889 <!--page 179 -->
8890 <pre>
8891 preprocessing-file:
8893 group:
8894 group-part
8895 group group-part
8896 group-part:
8897 if-section
8898 control-line
8899 text-line
8900 # non-directive
8901 if-section:
8903 if-group:
8907 elif-groups:
8908 elif-group
8909 elif-groups elif-group
8910 elif-group:
8912 else-group:
8914 endif-line:
8915 # endif new-line
8916 control-line:
8917 # include pp-tokens new-line
8918 # define identifier replacement-list new-line
8920 replacement-list new-line
8921 # define identifier lparen ... ) replacement-list new-line
8922 # define identifier lparen identifier-list , ... )
8923 replacement-list new-line
8924 # undef identifier new-line
8925 # line pp-tokens new-line
8928 # new-line
8929 text-line:
8931 non-directive:
8932 pp-tokens new-line
8933 lparen:
8934 a ( character not immediately preceded by white-space
8935 replacement-list:
8937 pp-tokens:
8938 preprocessing-token
8939 pp-tokens preprocessing-token
8940 new-line:
8941 the new-line character
8942 </pre>
8945 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
8946 following constraints: The first token in the sequence is a # preprocessing token that (at
8947 the start of translation phase 4) is either the first character in the source file (optionally
8948 after white space containing no new-line characters) or that follows white space
8949 containing at least one new-line character. The last token in the sequence is the first new-
8950 line character that follows the first token in the sequence.<sup><a href="#note165"><b>165)</b></a></sup> A new-line character ends
8951 the preprocessing directive even if it occurs within what would otherwise be an
8953 <!--page 180 -->
8954 invocation of a function-like macro.
8956 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
8957 with any of the directive names appearing in the syntax.
8959 When in a group that is skipped (<a href="#6.10.1">6.10.1</a>), the directive syntax is relaxed to allow any
8960 sequence of preprocessing tokens to occur between the directive name and the following
8961 new-line character.
8964 The only white-space characters that shall appear between preprocessing tokens within a
8965 preprocessing directive (from just after the introducing # preprocessing token through
8966 just before the terminating new-line character) are space and horizontal-tab (including
8967 spaces that have replaced comments or possibly other white-space characters in
8968 translation phase 3).
8971 The implementation can process and skip sections of source files conditionally, include
8972 other source files, and replace macros. These capabilities are called preprocessing,
8973 because conceptually they occur before translation of the resulting translation unit.
8975 The preprocessing tokens within a preprocessing directive are not subject to macro
8976 expansion unless otherwise stated.
8978 EXAMPLE In:
8979 <pre>
8980 #define EMPTY
8982 </pre>
8983 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
8984 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
8985 replaced.
8989 <p><small><a name="note165" href="#note165">165)</a> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
8990 significance, as all white space is equivalent except in certain situations during preprocessing (see the
8991 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
8992 </small>
8998 The expression that controls conditional inclusion shall be an integer constant expression
8999 except that: identifiers (including those lexically identical to keywords) are interpreted as
9000 described below;<sup><a href="#note166"><b>166)</b></a></sup> and it may contain unary operator expressions of the form
9001 <pre>
9002 defined identifier
9003 </pre>
9004 or
9005 <pre>
9006 defined ( identifier )
9007 </pre>
9008 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
9011 <!--page 181 -->
9012 predefined or if it has been the subject of a #define preprocessing directive without an
9013 intervening #undef directive with the same subject identifier), 0 if it is not.
9015 Each preprocessing token that remains (in the list of preprocessing tokens that will
9016 become the controlling expression) after all macro replacements have occurred shall be in
9020 Preprocessing directives of the forms
9021 <pre>
9024 </pre>
9025 check whether the controlling constant expression evaluates to nonzero.
9027 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
9028 the controlling constant expression are replaced (except for those macro names modified
9029 by the defined unary operator), just as in normal text. If the token defined is
9030 generated as a result of this replacement process or use of the defined unary operator
9031 does not match one of the two specified forms prior to macro replacement, the behavior is
9032 undefined. After all replacements due to macro expansion and the defined unary
9033 operator have been performed, all remaining identifiers (including those lexically
9034 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
9035 token is converted into a token. The resulting tokens compose the controlling constant
9036 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
9037 token conversion and evaluation, all signed integer types and all unsigned integer types
9038 act as if they have the same representation as, respectively, the types intmax_t and
9039 uintmax_t defined in the header <a href="#7.20"><stdint.h></a>.<sup><a href="#note167"><b>167)</b></a></sup> This includes interpreting
9040 character constants, which may involve converting escape sequences into execution
9041 character set members. Whether the numeric value for these character constants matches
9042 the value obtained when an identical character constant occurs in an expression (other
9043 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note168"><b>168)</b></a></sup> Also, whether a
9044 single-character character constant may have a negative value is implementation-defined.
9049 <!--page 182 -->
9051 Preprocessing directives of the forms
9052 <pre>
9055 </pre>
9056 check whether the identifier is or is not currently defined as a macro name. Their
9057 conditions are equivalent to #if defined identifier and #if !defined identifier
9058 respectively.
9060 Each directive's condition is checked in order. If it evaluates to false (zero), the group
9061 that it controls is skipped: directives are processed only through the name that determines
9062 the directive in order to keep track of the level of nested conditionals; the rest of the
9063 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
9064 group. Only the first group whose control condition evaluates to true (nonzero) is
9065 processed. If none of the conditions evaluates to true, and there is a #else directive, the
9066 group controlled by the #else is processed; lacking a #else directive, all the groups
9068 <p><b> Forward references</b>: macro replacement (<a href="#6.10.3">6.10.3</a>), source file inclusion (<a href="#6.10.2">6.10.2</a>), largest
9072 <p><small><a name="note166" href="#note166">166)</a> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
9073 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
9074 </small>
9075 <p><small><a name="note167" href="#note167">167)</a> Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant
9076 0x8000 is signed and positive within a #if expression even though it would be unsigned in
9077 translation phase 7.
9078 </small>
9079 <p><small><a name="note168" href="#note168">168)</a> Thus, the constant expression in the following #if directive and if statement is not guaranteed to
9080 evaluate to the same value in these two contexts.
9082 <pre>
9083 #if 'z' - 'a' == 25
9084 if ('z' - 'a' == 25)
9085 </pre>
9086 </small>
9087 <p><small><a name="note169" href="#note169">169)</a> As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
9088 before the terminating new-line character. However, comments may appear anywhere in a source file,
9089 including within a preprocessing directive.
9090 </small>
9096 A #include directive shall identify a header or source file that can be processed by the
9097 implementation.
9100 A preprocessing directive of the form
9101 <pre>
9103 </pre>
9104 searches a sequence of implementation-defined places for a header identified uniquely by
9105 the specified sequence between the < and > delimiters, and causes the replacement of that
9106 directive by the entire contents of the header. How the places are specified or the header
9107 identified is implementation-defined.
9109 A preprocessing directive of the form
9110 <pre>
9111 # include "q-char-sequence" new-line
9112 </pre>
9113 causes the replacement of that directive by the entire contents of the source file identified
9114 by the specified sequence between the " delimiters. The named source file is searched
9117 <!--page 183 -->
9118 for in an implementation-defined manner. If this search is not supported, or if the search
9119 fails, the directive is reprocessed as if it read
9120 <pre>
9121 # include <h-char-sequence> new-line
9122 </pre>
9123 with the identical contained sequence (including > characters, if any) from the original
9124 directive.
9125 <p><!--para 4 -->
9126 A preprocessing directive of the form
9127 <pre>
9128 # include pp-tokens new-line
9129 </pre>
9130 (that does not match one of the two previous forms) is permitted. The preprocessing
9131 tokens after include in the directive are processed just as in normal text. (Each
9132 identifier currently defined as a macro name is replaced by its replacement list of
9133 preprocessing tokens.) The directive resulting after all replacements shall match one of
9134 the two previous forms.<sup><a href="#note170"><b>170)</b></a></sup> The method by which a sequence of preprocessing tokens
9135 between a < and a > preprocessing token pair or a pair of " characters is combined into a
9136 single header name preprocessing token is implementation-defined.
9138 The implementation shall provide unique mappings for sequences consisting of one or
9139 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
9140 first character shall not be a digit. The implementation may ignore distinctions of
9141 alphabetical case and restrict the mapping to eight significant characters before the
9142 period.
9144 A #include preprocessing directive may appear in a source file that has been read
9145 because of a #include directive in another file, up to an implementation-defined
9148 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
9149 <pre>
9151 #include "myprog.h"
9152 </pre>
9157 <!--page 184 -->
9159 EXAMPLE 2 This illustrates macro-replaced #include directives:
9160 <pre>
9161 #if VERSION == 1
9162 #define INCFILE "vers1.h"
9163 #elif VERSION == 2
9164 #define INCFILE "vers2.h" // and so on
9165 #else
9166 #define INCFILE "versN.h"
9167 #endif
9168 #include INCFILE
9169 </pre>
9174 <p><small><a name="note170" href="#note170">170)</a> Note that adjacent string literals are not concatenated into a single string literal (see the translation
9175 phases in <a href="#5.1.1.2">5.1.1.2</a>); thus, an expansion that results in two string literals is an invalid directive.
9176 </small>
9182 Two replacement lists are identical if and only if the preprocessing tokens in both have
9183 the same number, ordering, spelling, and white-space separation, where all white-space
9184 separations are considered identical.
9186 An identifier currently defined as an object-like macro shall not be redefined by another
9187 #define preprocessing directive unless the second definition is an object-like macro
9188 definition and the two replacement lists are identical. Likewise, an identifier currently
9189 defined as a function-like macro shall not be redefined by another #define
9190 preprocessing directive unless the second definition is a function-like macro definition
9191 that has the same number and spelling of parameters, and the two replacement lists are
9192 identical.
9194 There shall be white-space between the identifier and the replacement list in the definition
9195 of an object-like macro.
9197 If the identifier-list in the macro definition does not end with an ellipsis, the number of
9198 arguments (including those arguments consisting of no preprocessing tokens) in an
9199 invocation of a function-like macro shall equal the number of parameters in the macro
9200 definition. Otherwise, there shall be more arguments in the invocation than there are
9201 parameters in the macro definition (excluding the ...). There shall exist a )
9202 preprocessing token that terminates the invocation.
9204 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
9205 macro that uses the ellipsis notation in the parameters.
9207 A parameter identifier in a function-like macro shall be uniquely declared within its
9208 scope.
9211 The identifier immediately following the define is called the macro name. There is one
9212 name space for macro names. Any white-space characters preceding or following the
9213 replacement list of preprocessing tokens are not considered part of the replacement list
9214 <!--page 185 -->
9215 for either form of macro.
9217 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
9218 a preprocessing directive could begin, the identifier is not subject to macro replacement.
9220 A preprocessing directive of the form
9221 <pre>
9222 # define identifier replacement-list new-line
9223 </pre>
9224 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note171"><b>171)</b></a></sup>
9225 to be replaced by the replacement list of preprocessing tokens that constitute the
9226 remainder of the directive. The replacement list is then rescanned for more macro names
9227 as specified below.
9229 A preprocessing directive of the form
9230 <pre>
9232 # define identifier lparen ... ) replacement-list new-line
9233 # define identifier lparen identifier-list , ... ) replacement-list new-line
9234 </pre>
9235 defines a function-like macro with parameters, whose use is similar syntactically to a
9236 function call. The parameters are specified by the optional list of identifiers, whose scope
9237 extends from their declaration in the identifier list until the new-line character that
9238 terminates the #define preprocessing directive. Each subsequent instance of the
9239 function-like macro name followed by a ( as the next preprocessing token introduces the
9240 sequence of preprocessing tokens that is replaced by the replacement list in the definition
9241 (an invocation of the macro). The replaced sequence of preprocessing tokens is
9242 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
9243 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
9244 tokens making up an invocation of a function-like macro, new-line is considered a normal
9245 white-space character.
9247 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
9248 forms the list of arguments for the function-like macro. The individual arguments within
9249 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
9250 between matching inner parentheses do not separate arguments. If there are sequences of
9251 preprocessing tokens within the list of arguments that would otherwise act as
9252 preprocessing directives,<sup><a href="#note172"><b>172)</b></a></sup> the behavior is undefined.
9254 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
9255 including any separating comma preprocessing tokens, are merged to form a single item:
9258 <!--page 186 -->
9259 the variable arguments. The number of arguments so combined is such that, following
9260 merger, the number of arguments is one more than the number of parameters in the macro
9261 definition (excluding the ...).
9264 <p><small><a name="note171" href="#note171">171)</a> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
9265 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
9266 are never scanned for macro names or parameters.
9267 </small>
9268 <p><small><a name="note172" href="#note172">172)</a> Despite the name, a non-directive is a preprocessing directive.
9269 </small>
9274 After the arguments for the invocation of a function-like macro have been identified,
9275 argument substitution takes place. A parameter in the replacement list, unless preceded
9276 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
9277 replaced by the corresponding argument after all macros contained therein have been
9278 expanded. Before being substituted, each argument's preprocessing tokens are
9279 completely macro replaced as if they formed the rest of the preprocessing file; no other
9280 preprocessing tokens are available.
9282 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
9283 were a parameter, and the variable arguments shall form the preprocessing tokens used to
9284 replace it.
9290 Each # preprocessing token in the replacement list for a function-like macro shall be
9291 followed by a parameter as the next preprocessing token in the replacement list.
9294 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
9295 token, both are replaced by a single character string literal preprocessing token that
9296 contains the spelling of the preprocessing token sequence for the corresponding
9297 argument. Each occurrence of white space between the argument's preprocessing tokens
9298 becomes a single space character in the character string literal. White space before the
9299 first preprocessing token and after the last preprocessing token composing the argument
9300 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
9301 is retained in the character string literal, except for special handling for producing the
9302 spelling of string literals and character constants: a \ character is inserted before each "
9303 and \ character of a character constant or string literal (including the delimiting "
9304 characters), except that it is implementation-defined whether a \ character is inserted
9305 before the \ character beginning a universal character name. If the replacement that
9306 results is not a valid character string literal, the behavior is undefined. The character
9307 string literal corresponding to an empty argument is "". The order of evaluation of # and
9308 ## operators is unspecified.
9309 <!--page 187 -->
9315 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
9316 list for either form of macro definition.
9319 If, in the replacement list of a function-like macro, a parameter is immediately preceded
9320 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
9321 argument's preprocessing token sequence; however, if an argument consists of no
9322 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
9325 For both object-like and function-like macro invocations, before the replacement list is
9326 reexamined for more macro names to replace, each instance of a ## preprocessing token
9327 in the replacement list (not from an argument) is deleted and the preceding preprocessing
9328 token is concatenated with the following preprocessing token. Placemarker
9329 preprocessing tokens are handled specially: concatenation of two placemarkers results in
9330 a single placemarker preprocessing token, and concatenation of a placemarker with a
9331 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
9332 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
9333 token is available for further macro replacement. The order of evaluation of ## operators
9334 is unspecified.
9336 EXAMPLE In the following fragment:
9337 <pre>
9338 #define hash_hash # ## #
9339 #define mkstr(a) # a
9340 #define in_between(a) mkstr(a)
9341 #define join(c, d) in_between(c hash_hash d)
9342 char p[] = join(x, y); // equivalent to
9343 // char p[] = "x ## y";
9344 </pre>
9345 The expansion produces, at various stages:
9346 <pre>
9347 join(x, y)
9348 in_between(x hash_hash y)
9349 in_between(x ## y)
9350 mkstr(x ## y)
9351 "x ## y"
9352 </pre>
9353 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
9354 this new token is not the ## operator.
9357 <!--page 188 -->
9360 <p><small><a name="note173" href="#note173">173)</a> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
9361 exist only within translation phase 4.
9362 </small>
9367 After all parameters in the replacement list have been substituted and # and ##
9368 processing has taken place, all placemarker preprocessing tokens are removed. The
9369 resulting preprocessing token sequence is then rescanned, along with all subsequent
9370 preprocessing tokens of the source file, for more macro names to replace.
9372 If the name of the macro being replaced is found during this scan of the replacement list
9373 (not including the rest of the source file's preprocessing tokens), it is not replaced.
9374 Furthermore, if any nested replacements encounter the name of the macro being replaced,
9375 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
9376 available for further replacement even if they are later (re)examined in contexts in which
9377 that macro name preprocessing token would otherwise have been replaced.
9379 The resulting completely macro-replaced preprocessing token sequence is not processed
9380 as a preprocessing directive even if it resembles one, but all pragma unary operator
9383 EXAMPLE There are cases where it is not clear whether a replacement is nested or not. For example,
9384 given the following macro definitions:
9385 <pre>
9386 #define f(a) a*g
9387 #define g(a) f(a)
9388 </pre>
9389 the invocation
9390 <pre>
9392 </pre>
9393 may expand to either
9394 <pre>
9396 </pre>
9397 or
9398 <pre>
9400 </pre>
9401 Strictly conforming programs are not permitted to depend on such unspecified behavior.
9407 A macro definition lasts (independent of block structure) until a corresponding #undef
9408 directive is encountered or (if none is encountered) until the end of the preprocessing
9409 translation unit. Macro definitions have no significance after translation phase 4.
9411 A preprocessing directive of the form
9412 <pre>
9413 # undef identifier new-line
9414 </pre>
9415 causes the specified identifier no longer to be defined as a macro name. It is ignored if
9416 the specified identifier is not currently defined as a macro name.
9418 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
9419 <!--page 189 -->
9420 <pre>
9421 #define TABSIZE 100
9422 int table[TABSIZE];
9423 </pre>
9426 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
9427 It has the advantages of working for any compatible types of the arguments and of generating in-line code
9428 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
9429 arguments a second time (including side effects) and generating more code than a function if invoked
9430 several times. It also cannot have its address taken, as it has none.
9431 <pre>
9432 #define max(a, b) ((a) > (b) ? (a) : (b))
9433 </pre>
9434 The parentheses ensure that the arguments and the resulting expression are bound properly.
9437 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
9438 <pre>
9439 #define x 3
9440 #define f(a) f(x * (a))
9441 #undef x
9442 #define x 2
9443 #define g f
9444 #define z z[0]
9445 #define h g(~
9446 #define m(a) a(w)
9448 #define t(a) a
9449 #define p() int
9450 #define q(x) x
9451 #define r(x,y) x ## y
9452 #define str(x) # x
9455 (f)^m(m);
9458 </pre>
9459 results in
9460 <pre>
9465 </pre>
9468 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
9469 sequence
9470 <!--page 190 -->
9471 <pre>
9472 #define str(s) # s
9473 #define xstr(s) str(s)
9475 x ## s, x ## t)
9476 #define INCFILE(n) vers ## n
9477 #define glue(a, b) a ## b
9478 #define xglue(a, b) glue(a, b)
9479 #define HIGHLOW "hello"
9480 #define LOW LOW ", world"
9483 == 0) str(: @\n), s);
9484 #include xstr(INCFILE(2).h)
9485 glue(HIGH, LOW);
9486 xglue(HIGH, LOW)
9487 </pre>
9488 results in
9489 <pre>
9491 fputs(
9493 s);
9494 #include "vers2.h" (after macro replacement, before file access)
9495 "hello";
9497 </pre>
9498 or, after concatenation of the character string literals,
9499 <pre>
9500 printf("x1= %d, x2= %s", x1, x2);
9501 fputs(
9503 s);
9504 #include "vers2.h" (after macro replacement, before file access)
9505 "hello";
9506 "hello, world"
9507 </pre>
9508 Space around the # and ## tokens in the macro definition is optional.
9511 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
9512 <pre>
9513 #define t(x,y,z) x ## y ## z
9516 </pre>
9517 results in
9518 <pre>
9521 </pre>
9524 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
9525 <pre>
9528 #define FUNC_LIKE(a) ( a )
9529 #define FUNC_LIKE( a )( /* note the white space */ \
9530 a /* other stuff on this line
9531 */ )
9532 </pre>
9533 But the following redefinitions are invalid:
9534 <pre>
9535 #define OBJ_LIKE (0) // different token sequence
9537 #define FUNC_LIKE(b) ( a ) // different parameter usage
9538 #define FUNC_LIKE(b) ( b ) // different parameter spelling
9539 </pre>
9542 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
9543 <!--page 191 -->
9544 <pre>
9545 #define debug(...) fprintf(stderr, __VA_ARGS__)
9546 #define showlist(...) puts(#__VA_ARGS__)
9547 #define report(test, ...) ((test)?puts(#test):\
9548 printf(__VA_ARGS__))
9549 debug("Flag");
9550 debug("X = %d\n", x);
9551 showlist(The first, second, and third items.);
9553 </pre>
9554 results in
9555 <pre>
9556 fprintf(stderr, "Flag" );
9557 fprintf(stderr, "X = %d\n", x );
9558 puts( "The first, second, and third items." );
9560 printf("x is %d but y is %d", x, y));
9561 </pre>
9568 The string literal of a #line directive, if present, shall be a character string literal.
9571 The line number of the current source line is one greater than the number of new-line
9572 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
9573 file to the current token.
9575 A preprocessing directive of the form
9576 <pre>
9577 # line digit-sequence new-line
9578 </pre>
9579 causes the implementation to behave as if the following sequence of source lines begins
9580 with a source line that has a line number as specified by the digit sequence (interpreted as
9581 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
9582 2147483647.
9584 A preprocessing directive of the form
9585 <pre>
9586 # line digit-sequence "s-char-sequence<sub>opt</sub>" new-line
9587 </pre>
9588 sets the presumed line number similarly and changes the presumed name of the source
9589 file to be the contents of the character string literal.
9591 A preprocessing directive of the form
9592 <pre>
9593 # line pp-tokens new-line
9594 </pre>
9595 (that does not match one of the two previous forms) is permitted. The preprocessing
9596 tokens after line on the directive are processed just as in normal text (each identifier
9597 currently defined as a macro name is replaced by its replacement list of preprocessing
9598 tokens). The directive resulting after all replacements shall match one of the two
9599 previous forms and is then processed as appropriate.
9600 <!--page 192 -->
9606 A preprocessing directive of the form
9607 <pre>
9609 </pre>
9610 causes the implementation to produce a diagnostic message that includes the specified
9611 sequence of preprocessing tokens.
9617 A preprocessing directive of the form
9618 <pre>
9620 </pre>
9621 where the preprocessing token STDC does not immediately follow pragma in the
9622 directive (prior to any macro replacement)<sup><a href="#note174"><b>174)</b></a></sup> causes the implementation to behave in an
9623 implementation-defined manner. The behavior might cause translation to fail or cause the
9624 translator or the resulting program to behave in a non-conforming manner. Any such
9625 pragma that is not recognized by the implementation is ignored.
9627 If the preprocessing token STDC does immediately follow pragma in the directive (prior
9628 to any macro replacement), then no macro replacement is performed on the directive, and
9629 the directive shall have one of the following forms<sup><a href="#note175"><b>175)</b></a></sup> whose meanings are described
9630 elsewhere:
9631 <pre>
9632 #pragma STDC FP_CONTRACT on-off-switch
9633 #pragma STDC FENV_ACCESS on-off-switch
9634 #pragma STDC CX_LIMITED_RANGE on-off-switch
9635 on-off-switch: one of
9636 ON OFF DEFAULT
9637 </pre>
9638 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
9644 <!--page 193 -->
9647 <p><small><a name="note174" href="#note174">174)</a> An implementation is not required to perform macro replacement in pragmas, but it is permitted
9648 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
9649 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
9650 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
9651 but is not required to.
9652 </small>
9653 <p><small><a name="note175" href="#note175">175)</a> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
9654 </small>
9660 A preprocessing directive of the form
9661 <pre>
9662 # new-line
9663 </pre>
9664 has no effect.
9669 The values of the predefined macros listed in the following subclauses<sup><a href="#note176"><b>176)</b></a></sup> (except for
9670 __FILE__ and __LINE__) remain constant throughout the translation unit.
9672 None of these macro names, nor the identifier defined, shall be the subject of a
9673 #define or a #undef preprocessing directive. Any other predefined macro names
9674 shall begin with a leading underscore followed by an uppercase letter or a second
9675 underscore.
9677 The implementation shall not predefine the macro __cplusplus, nor shall it define it
9678 in any standard header.
9682 <p><small><a name="note176" href="#note176">176)</a> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
9683 </small>
9688 The following macro names shall be defined by the implementation:
9689 __DATE__ The date of translation of the preprocessing translation unit: a character
9690 <pre>
9691 string literal of the form "Mmm dd yyyy", where the names of the
9692 months are the same as those generated by the asctime function, and the
9693 first character of dd is a space character if the value is less than 10. If the
9694 date of translation is not available, an implementation-defined valid date
9695 shall be supplied.
9696 </pre>
9697 __FILE__ The presumed name of the current source file (a character string literal).<sup><a href="#note177"><b>177)</b></a></sup>
9698 __LINE__ The presumed line number (within the current source file) of the current
9699 <pre>
9701 </pre>
9702 __STDC__ The integer constant 1, intended to indicate a conforming implementation.
9703 __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
9704 <pre>
9705 implementation or the integer constant 0 if it is not.
9706 </pre>
9711 <!--page 194 -->
9713 __TIME__ The time of translation of the preprocessing translation unit: a character
9714 <pre>
9715 string literal of the form "hh:mm:ss" as in the time generated by the
9716 asctime function. If the time of translation is not available, an
9717 implementation-defined valid time shall be supplied.
9718 </pre>
9722 <p><small><a name="note177" href="#note177">177)</a> The presumed source file name and line number can be changed by the #line directive.
9723 </small>
9724 <p><small><a name="note178" href="#note178">178)</a> This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
9726 remain an integer constant of type long int that is increased with each revision of this International
9727 Standard.
9728 </small>
9733 The following macro names are conditionally defined by the implementation:
9734 __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
9735 <pre>
9736 199712L). If this symbol is defined, then every character in the Unicode
9737 required set, when stored in an object of type wchar_t, has the same
9738 value as the short identifier of that character. The Unicode required set
9739 consists of all the characters that are defined by ISO/IEC 10646, along with
9740 all amendments and technical corrigenda, as of the specified year and
9741 month. If some other encoding is used, the macro shall not be defined and
9742 the actual encoding used is implementation-defined.
9743 </pre>
9744 __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
9745 <pre>
9746 the encoding for wchar_t, a member of the basic character set need not
9747 have a code value equal to its value when used as the lone character in an
9748 integer character constant.
9749 </pre>
9750 __STDC_UTF_16__ The integer constant 1, intended to indicate that values of type
9751 <pre>
9752 char16_t are UTF-16 encoded. If some other encoding is used, the
9753 macro shall not be defined and the actual encoding used is implementation-
9754 defined.
9755 </pre>
9756 __STDC_UTF_32__ The integer constant 1, intended to indicate that values of type
9757 <pre>
9758 char32_t are UTF-32 encoded. If some other encoding is used, the
9759 macro shall not be defined and the actual encoding used is implementation-
9760 defined.
9761 </pre>
9762 <p><b> Forward references</b>: common definitions (<a href="#7.19">7.19</a>), unicode utilities (<a href="#7.28">7.28</a>).
9767 <!--page 195 -->
9772 The following macro names are conditionally defined by the implementation:
9773 __STDC_ANALYZABLE__ The integer constant 1, intended to indicate conformance to
9774 <pre>
9776 </pre>
9777 __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
9778 <pre>
9780 </pre>
9781 __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
9782 <pre>
9784 arithmetic).
9785 </pre>
9786 __STDC_LIB_EXT1__ The integer constant 201ymmL, intended to indicate support
9787 <pre>
9788 for the extensions defined in <a href="#K">annex K</a> (Bounds-checking interfaces).<sup><a href="#note179"><b>179)</b></a></sup>
9789 </pre>
9790 __STDC_NO_ATOMICS__ The integer constant 1, intended to indicate that the
9791 <pre>
9792 implementation does not support atomic types (including the _Atomic
9794 </pre>
9795 __STDC_NO_COMPLEX__ The integer constant 1, intended to indicate that the
9796 <pre>
9798 header.
9799 </pre>
9800 __STDC_NO_THREADS__ The integer constant 1, intended to indicate that the
9801 <pre>
9803 </pre>
9804 __STDC_NO_VLA__ The integer constant 1, intended to indicate that the
9805 <pre>
9806 implementation does not support variable length arrays or variably
9807 modified types.
9808 </pre>
9810 An implementation that defines __STDC_NO_COMPLEX__ shall not define
9811 __STDC_IEC_559_COMPLEX__.
9816 <!--page 196 -->
9819 <p><small><a name="note179" href="#note179">179)</a> The intention is that this will remain an integer constant of type long int that is increased with
9820 each revision of this International Standard.
9821 </small>
9827 A unary operator expression of the form:
9828 <pre>
9829 _Pragma ( string-literal )
9830 </pre>
9831 is processed as follows: The string literal is destringized by deleting any encoding prefix,
9832 deleting the leading and trailing double-quotes, replacing each escape sequence \" by a
9833 double-quote, and replacing each escape sequence \\ by a single backslash. The
9834 resulting sequence of characters is processed through translation phase 3 to produce
9835 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
9836 directive. The original four preprocessing tokens in the unary operator expression are
9837 removed.
9838 <p><!--para 2 -->
9839 EXAMPLE A directive of the form:
9840 <pre>
9842 </pre>
9843 can also be expressed as:
9844 <pre>
9846 </pre>
9847 The latter form is processed in the same way whether it appears literally as shown, or results from macro
9848 replacement, as in:
9849 <!--page 197 -->
9850 <pre>
9851 #define LISTING(x) PRAGMA(listing on #x)
9852 #define PRAGMA(x) _Pragma(#x)
9853 LISTING ( ..\listing.dir )
9854 </pre>
9861 <p><!--para 1 -->
9862 Future standardization may include additional floating-point types, including those with
9863 greater range, precision, or both than long double.
9867 <p><!--para 1 -->
9868 Declaring an identifier with internal linkage at file scope without the static storage-
9869 class specifier is an obsolescent feature.
9873 <p><!--para 1 -->
9874 Restriction of the significance of an external name to fewer than 255 characters
9875 (considering each universal character name or extended source character as a single
9876 character) is an obsolescent feature that is a concession to existing implementations.
9880 <p><!--para 1 -->
9881 Lowercase letters as escape sequences are reserved for future standardization. Other
9882 characters may be used in extensions.
9886 <p><!--para 1 -->
9887 The placement of a storage-class specifier other than at the beginning of the declaration
9888 specifiers in a declaration is an obsolescent feature.
9892 <p><!--para 1 -->
9893 The use of function declarators with empty parentheses (not prototype-format parameter
9894 type declarators) is an obsolescent feature.
9898 <p><!--para 1 -->
9899 The use of function definitions with separate parameter identifier and declaration lists
9900 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
9904 <p><!--para 1 -->
9905 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
9909 <p><!--para 1 -->
9910 Macro names beginning with __STDC_ are reserved for future standardization.
9911 <!--page 198 -->
9921 <p><!--para 1 -->
9922 A string is a contiguous sequence of characters terminated by and including the first null
9923 character. The term multibyte string is sometimes used instead to emphasize special
9924 processing given to multibyte characters contained in the string or to avoid confusion
9925 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
9926 character. The length of a string is the number of bytes preceding the null character and
9927 the value of a string is the sequence of the values of the contained characters, in order.
9928 <p><!--para 2 -->
9929 The decimal-point character is the character used by functions that convert floating-point
9930 numbers to or from character sequences to denote the beginning of the fractional part of
9931 such character sequences.<sup><a href="#note180"><b>180)</b></a></sup> It is represented in the text and examples by a period, but
9932 may be changed by the setlocale function.
9933 <p><!--para 3 -->
9934 A null wide character is a wide character with code value zero.
9935 <p><!--para 4 -->
9936 A wide string is a contiguous sequence of wide characters terminated by and including
9937 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
9938 addressed) wide character. The length of a wide string is the number of wide characters
9939 preceding the null wide character and the value of a wide string is the sequence of code
9940 values of the contained wide characters, in order.
9941 <p><!--para 5 -->
9942 A shift sequence is a contiguous sequence of bytes within a multibyte string that
9943 (potentially) causes a change in shift state (see <a href="#5.2.1.2">5.2.1.2</a>). A shift sequence shall not have a
9944 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
9946 <p><b> Forward references</b>: character handling (<a href="#7.4">7.4</a>), the setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
9951 <!--page 199 -->
9953 <p><b>Footnotes</b>
9954 <p><small><a name="note180" href="#note180">180)</a> The functions that make use of the decimal-point character are the numeric conversion functions
9955 (<a href="#7.22.1">7.22.1</a>, <a href="#7.29.4.1">7.29.4.1</a>) and the formatted input/output functions (<a href="#7.21.6">7.21.6</a>, <a href="#7.29.2">7.29.2</a>).
9956 </small>
9957 <p><small><a name="note181" href="#note181">181)</a> For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus be large
9958 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
9959 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
9960 implementation's choice.
9961 </small>
9965 <p><!--para 1 -->
9966 Each library function is declared, with a type that includes a prototype, in a header,<sup><a href="#note182"><b>182)</b></a></sup>
9967 whose contents are made available by the #include preprocessing directive. The
9968 header declares a set of related functions, plus any necessary types and additional macros
9969 needed to facilitate their use. Declarations of types described in this clause shall not
9970 include type qualifiers, unless explicitly stated otherwise.
9971 <p><!--para 2 -->
9973 <pre>
9974 <a href="#7.2"><assert.h></a> <a href="#7.12"><math.h></a> <a href="#7.22"><stdlib.h></a>
9975 <a href="#7.3"><complex.h></a> <a href="#7.13"><setjmp.h></a> <a href="#7.23"><stdnoreturn.h></a>
9976 <a href="#7.4"><ctype.h></a> <a href="#7.14"><signal.h></a> <a href="#7.24"><string.h></a>
9977 <a href="#7.5"><errno.h></a> <a href="#7.15"><stdalign.h></a> <a href="#7.25"><tgmath.h></a>
9978 <a href="#7.6"><fenv.h></a> <a href="#7.16"><stdarg.h></a> <a href="#7.26"><threads.h></a>
9979 <a href="#7.7"><float.h></a> <a href="#7.17"><stdatomic.h></a> <a href="#7.27"><time.h></a>
9980 <a href="#7.8"><inttypes.h></a> <a href="#7.18"><stdbool.h></a> <a href="#7.28"><uchar.h></a>
9981 <a href="#7.9"><iso646.h></a> <a href="#7.19"><stddef.h></a> <a href="#7.29"><wchar.h></a>
9982 <a href="#7.10"><limits.h></a> <a href="#7.20"><stdint.h></a> <a href="#7.30"><wctype.h></a>
9984 </pre>
9985 <p><!--para 3 -->
9986 If a file with the same name as one of the above < and > delimited sequences, not
9987 provided as part of the implementation, is placed in any of the standard places that are
9988 searched for included source files, the behavior is undefined.
9989 <p><!--para 4 -->
9990 Standard headers may be included in any order; each may be included more than once in
9991 a given scope, with no effect different from being included only once, except that the
9992 effect of including <a href="#7.2"><assert.h></a> depends on the definition of NDEBUG (see <a href="#7.2">7.2</a>). If
9993 used, a header shall be included outside of any external declaration or definition, and it
9994 shall first be included before the first reference to any of the functions or objects it
9995 declares, or to any of the types or macros it defines. However, if an identifier is declared
9996 or defined in more than one header, the second and subsequent associated headers may be
9997 included after the initial reference to the identifier. The program shall not have any
9998 macros with names lexically identical to keywords currently defined prior to the inclusion
9999 of the header or when any macro defined in the header is expanded.
10000 <p><!--para 5 -->
10001 Any definition of an object-like macro described in this clause shall expand to code that is
10002 fully protected by parentheses where necessary, so that it groups in an arbitrary
10003 expression as if it were a single identifier.
10006 <!--page 200 -->
10007 <p><!--para 6 -->
10008 Any declaration of a library function shall have external linkage.
10009 <p><!--para 7 -->
10013 <p><b>Footnotes</b>
10014 <p><small><a name="note182" href="#note182">182)</a> A header is not necessarily a source file, nor are the < and > delimited sequences in header names
10015 necessarily valid source file names.
10016 </small>
10017 <p><small><a name="note183" href="#note183">183)</a> The headers <a href="#7.3"><complex.h></a>, <a href="#7.17"><stdatomic.h></a>, and <a href="#7.26"><threads.h></a> are conditional features that
10019 </small>
10023 <p><!--para 1 -->
10024 Each header declares or defines all identifiers listed in its associated subclause, and
10025 optionally declares or defines identifiers listed in its associated future library directions
10026 subclause and identifiers which are always reserved either for any use or for use as file
10027 scope identifiers.
10028 <ul>
10029 <li> All identifiers that begin with an underscore and either an uppercase letter or another
10030 underscore are always reserved for any use.
10031 <li> All identifiers that begin with an underscore are always reserved for use as identifiers
10032 with file scope in both the ordinary and tag name spaces.
10033 <li> Each macro name in any of the following subclauses (including the future library
10034 directions) is reserved for use as specified if any of its associated headers is included;
10036 <li> All identifiers with external linkage in any of the following subclauses (including the
10037 future library directions) and errno are always reserved for use as identifiers with
10039 <li> Each identifier with file scope listed in any of the following subclauses (including the
10040 future library directions) is reserved for use as a macro name and as an identifier with
10041 file scope in the same name space if any of its associated headers is included.
10042 </ul>
10043 <p><!--para 2 -->
10044 No other identifiers are reserved. If the program declares or defines an identifier in a
10045 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
10046 identifier as a macro name, the behavior is undefined.
10047 <p><!--para 3 -->
10048 If the program removes (with #undef) any macro definition of an identifier in the first
10049 group listed above, the behavior is undefined.
10054 <!--page 201 -->
10056 <p><b>Footnotes</b>
10057 <p><small><a name="note184" href="#note184">184)</a> The list of reserved identifiers with external linkage includes math_errhandling, setjmp,
10058 va_copy, and va_end.
10059 </small>
10063 <p><!--para 1 -->
10064 Each of the following statements applies unless explicitly stated otherwise in the detailed
10065 descriptions that follow: If an argument to a function has an invalid value (such as a value
10066 outside the domain of the function, or a pointer outside the address space of the program,
10067 or a null pointer, or a pointer to non-modifiable storage when the corresponding
10068 parameter is not const-qualified) or a type (after promotion) not expected by a function
10069 with variable number of arguments, the behavior is undefined. If a function argument is
10070 described as being an array, the pointer actually passed to the function shall have a value
10071 such that all address computations and accesses to objects (that would be valid if the
10072 pointer did point to the first element of such an array) are in fact valid. Any function
10073 declared in a header may be additionally implemented as a function-like macro defined in
10074 the header, so if a library function is declared explicitly when its header is included, one
10075 of the techniques shown below can be used to ensure the declaration is not affected by
10076 such a macro. Any macro definition of a function can be suppressed locally by enclosing
10077 the name of the function in parentheses, because the name is then not followed by the left
10078 parenthesis that indicates expansion of a macro function name. For the same syntactic
10079 reason, it is permitted to take the address of a library function even if it is also defined as
10080 a macro.<sup><a href="#note185"><b>185)</b></a></sup> The use of #undef to remove any macro definition will also ensure that an
10081 actual function is referred to. Any invocation of a library function that is implemented as
10082 a macro shall expand to code that evaluates each of its arguments exactly once, fully
10083 protected by parentheses where necessary, so it is generally safe to use arbitrary
10084 expressions as arguments.<sup><a href="#note186"><b>186)</b></a></sup> Likewise, those function-like macros described in the
10085 following subclauses may be invoked in an expression anywhere a function with a
10086 compatible return type could be called.<sup><a href="#note187"><b>187)</b></a></sup> All object-like macros listed as expanding to
10089 <!--page 202 -->
10090 integer constant expressions shall additionally be suitable for use in #if preprocessing
10091 directives.
10092 <p><!--para 2 -->
10093 Provided that a library function can be declared without reference to any type defined in a
10094 header, it is also permissible to declare the function and use it without including its
10095 associated header.
10096 <p><!--para 3 -->
10097 There is a sequence point immediately before a library function returns.
10098 <p><!--para 4 -->
10099 The functions in the standard library are not guaranteed to be reentrant and may modify
10101 <p><!--para 5 -->
10102 Unless explicitly stated otherwise in the detailed descriptions that follow, library
10103 functions shall prevent data races as follows: A library function shall not directly or
10104 indirectly access objects accessible by threads other than the current thread unless the
10105 objects are accessed directly or indirectly via the function's arguments. A library
10106 function shall not directly or indirectly modify objects accessible by threads other than
10107 the current thread unless the objects are accessed directly or indirectly via the function's
10108 non-const arguments.<sup><a href="#note189"><b>189)</b></a></sup> Implementations may share their own internal objects between
10109 threads if the objects are not visible to users and are protected against data races.
10110 <p><!--para 6 -->
10111 Unless otherwise specified, library functions shall perform all operations solely within the
10112 current thread if those operations have effects that are visible to users.<sup><a href="#note190"><b>190)</b></a></sup>
10113 <p><!--para 7 -->
10114 EXAMPLE The function atoi may be used in any of several ways:
10115 <ul>
10116 <li> by use of its associated header (possibly generating a macro expansion)
10117 <pre>
10119 const char *str;
10120 /* ... */
10121 i = atoi(str);
10122 </pre>
10123 <li> by use of its associated header (assuredly generating a true function reference)
10128 <!--page 203 -->
10129 <pre>
10131 #undef atoi
10132 const char *str;
10133 /* ... */
10134 i = atoi(str);
10135 </pre>
10136 or
10137 <pre>
10139 const char *str;
10140 /* ... */
10141 i = (atoi)(str);
10142 </pre>
10143 <li> by explicit declaration
10144 <!--page 204 -->
10145 <pre>
10146 extern int atoi(const char *);
10147 const char *str;
10148 /* ... */
10149 i = atoi(str);
10150 </pre>
10151 </ul>
10153 <p><b>Footnotes</b>
10154 <p><small><a name="note185" href="#note185">185)</a> This means that an implementation shall provide an actual function for each library function, even if it
10155 also provides a macro for that function.
10156 </small>
10157 <p><small><a name="note186" href="#note186">186)</a> Such macros might not contain the sequence points that the corresponding function calls do.
10158 </small>
10159 <p><small><a name="note187" href="#note187">187)</a> Because external identifiers and some macro names beginning with an underscore are reserved,
10160 implementations may provide special semantics for such names. For example, the identifier
10161 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
10162 appropriate header could specify
10164 <pre>
10165 #define abs(x) _BUILTIN_abs(x)
10166 </pre>
10167 for a compiler whose code generator will accept it.
10168 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
10169 function may write
10171 <pre>
10172 #undef abs
10173 </pre>
10174 whether the implementation's header provides a macro implementation of abs or a built-in
10175 implementation. The prototype for the function, which precedes and is hidden by any macro
10176 definition, is thereby revealed also.
10177 </small>
10178 <p><small><a name="note188" href="#note188">188)</a> Thus, a signal handler cannot, in general, call standard library functions.
10179 </small>
10180 <p><small><a name="note189" href="#note189">189)</a> This means, for example, that an implementation is not permitted to use a static object for internal
10181 purposes without synchronization because it could cause a data race even in programs that do not
10182 explicitly share objects between threads. Similarly, an implementation of memcpy is not permitted to
10183 copy bytes beyond the specified length of the destination object and then restore the original values
10184 because it could cause a data race if the program shared those bytes between threads.
10185 </small>
10186 <p><small><a name="note190" href="#note190">190)</a> This allows implementations to parallelize operations if there are no visible side effects.
10187 </small>
10191 <p><!--para 1 -->
10192 The header <a href="#7.2"><assert.h></a> defines the assert and static_assert macros and
10193 refers to another macro,
10194 <pre>
10195 NDEBUG
10196 </pre>
10197 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
10198 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
10199 simply as
10200 <pre>
10201 #define assert(ignore) ((void)0)
10202 </pre>
10203 The assert macro is redefined according to the current state of NDEBUG each time that
10205 <p><!--para 2 -->
10206 The assert macro shall be implemented as a macro, not as an actual function. If the
10207 macro definition is suppressed in order to access an actual function, the behavior is
10208 undefined.
10209 <p><!--para 3 -->
10210 The macro
10211 <pre>
10212 static_assert
10213 </pre>
10214 expands to _Static_assert.
10221 <p><b>Synopsis</b>
10222 <p><!--para 1 -->
10223 <pre>
10225 void assert(scalar expression);
10226 </pre>
10227 <p><b>Description</b>
10228 <p><!--para 2 -->
10229 The assert macro puts diagnostic tests into programs; it expands to a void expression.
10230 When it is executed, if expression (which shall have a scalar type) is false (that is,
10231 compares equal to 0), the assert macro writes information about the particular call that
10232 failed (including the text of the argument, the name of the source file, the source line
10233 number, and the name of the enclosing function -- the latter are respectively the values of
10234 the preprocessing macros __FILE__ and __LINE__ and of the identifier
10235 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note191"><b>191)</b></a></sup> It
10236 then calls the abort function.
10240 <!--page 205 -->
10241 <p><b>Returns</b>
10242 <p><!--para 3 -->
10243 The assert macro returns no value.
10245 <!--page 206 -->
10247 <p><b>Footnotes</b>
10248 <p><small><a name="note191" href="#note191">191)</a> The message written might be of the form:
10249 Assertion failed: expression, function abc, file xyz, line nnn.
10250 </small>
10257 <p><!--para 1 -->
10258 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
10260 <p><!--para 2 -->
10261 Implementations that define the macro __STDC_NO_COMPLEX__ need not provide
10262 this header nor support any of its facilities.
10263 <p><!--para 3 -->
10264 Each synopsis specifies a family of functions consisting of a principal function with one
10265 or more double complex parameters and a double complex or double return
10266 value; and other functions with the same name but with f and l suffixes which are
10267 corresponding functions with float and long double parameters and return values.
10268 <p><!--para 4 -->
10269 The macro
10270 <pre>
10271 complex
10272 </pre>
10273 expands to _Complex; the macro
10274 <pre>
10275 _Complex_I
10276 </pre>
10277 expands to a constant expression of type const float _Complex, with the value of
10279 <p><!--para 5 -->
10280 The macros
10281 <pre>
10282 imaginary
10283 </pre>
10284 and
10285 <pre>
10286 _Imaginary_I
10287 </pre>
10288 are defined if and only if the implementation supports imaginary types;<sup><a href="#note194"><b>194)</b></a></sup> if defined,
10289 they expand to _Imaginary and a constant expression of type const float
10290 _Imaginary with the value of the imaginary unit.
10291 <p><!--para 6 -->
10292 The macro
10293 <pre>
10294 I
10295 </pre>
10296 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
10297 defined, I shall expand to _Complex_I.
10298 <p><!--para 7 -->
10299 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
10300 redefine the macros complex, imaginary, and I.
10302 <!--page 207 -->
10303 <p><b> Forward references</b>: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
10305 <p><b>Footnotes</b>
10306 <p><small><a name="note192" href="#note192">192)</a> See ''future library directions'' (<a href="#7.31.1">7.31.1</a>).
10307 </small>
10308 <p><small><a name="note193" href="#note193">193)</a> The imaginary unit is a number i such that i 2 = -1.
10309 </small>
10310 <p><small><a name="note194" href="#note194">194)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
10311 </small>
10315 <p><!--para 1 -->
10316 Values are interpreted as radians, not degrees. An implementation may set errno but is
10317 not required to.
10321 <p><!--para 1 -->
10322 Some of the functions below have branch cuts, across which the function is
10323 discontinuous. For implementations with a signed zero (including all IEC 60559
10324 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
10325 one side of a cut from another so the function is continuous (except for format
10326 limitations) as the cut is approached from either side. For example, for the square root
10327 function, which has a branch cut along the negative real axis, the top of the cut, with
10328 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
10329 imaginary part -0, maps to the negative imaginary axis.
10330 <p><!--para 2 -->
10331 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
10332 sides of branch cuts. These implementations shall map a cut so the function is continuous
10333 as the cut is approached coming around the finite endpoint of the cut in a counter
10334 clockwise direction. (Branch cuts for the functions specified here have just one finite
10335 endpoint.) For example, for the square root function, coming counter clockwise around
10336 the finite endpoint of the cut along the negative real axis approaches the cut from above,
10337 so the cut maps to the positive imaginary axis.
10341 <p><b>Synopsis</b>
10342 <p><!--para 1 -->
10343 <pre>
10345 #pragma STDC CX_LIMITED_RANGE on-off-switch
10346 </pre>
10347 <p><b>Description</b>
10348 <p><!--para 2 -->
10349 The usual mathematical formulas for complex multiply, divide, and absolute value are
10350 problematic because of their treatment of infinities and because of undue overflow and
10351 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
10352 implementation that (where the state is ''on'') the usual mathematical formulas are
10353 acceptable.<sup><a href="#note195"><b>195)</b></a></sup> The pragma can occur either outside external declarations or preceding all
10354 explicit declarations and statements inside a compound statement. When outside external
10355 declarations, the pragma takes effect from its occurrence until another
10356 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
10357 When inside a compound statement, the pragma takes effect from its occurrence until
10358 another CX_LIMITED_RANGE pragma is encountered (including within a nested
10359 compound statement), or until the end of the compound statement; at the end of a
10360 compound statement the state for the pragma is restored to its condition just before the
10361 <!--page 208 -->
10362 compound statement. If this pragma is used in any other context, the behavior is
10363 undefined. The default state for the pragma is ''off''.
10365 <p><b>Footnotes</b>
10366 <p><small><a name="note195" href="#note195">195)</a> The purpose of the pragma is to allow the implementation to use the formulas:
10368 <pre>
10369 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
10370 (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
10371 | x + iy | = (sqrt) x 2 + y 2
10372 -----
10373 </pre>
10374 where the programmer can determine they are safe.
10375 </small>
10382 <p><b>Synopsis</b>
10383 <p><!--para 1 -->
10384 <pre>
10386 double complex cacos(double complex z);
10387 float complex cacosf(float complex z);
10388 long double complex cacosl(long double complex z);
10389 </pre>
10390 <p><b>Description</b>
10391 <p><!--para 2 -->
10392 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
10393 interval [-1, +1] along the real axis.
10394 <p><b>Returns</b>
10395 <p><!--para 3 -->
10396 The cacos functions return the complex arc cosine value, in the range of a strip
10397 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
10398 real axis.
10402 <p><b>Synopsis</b>
10403 <p><!--para 1 -->
10404 <pre>
10406 double complex casin(double complex z);
10407 float complex casinf(float complex z);
10408 long double complex casinl(long double complex z);
10409 </pre>
10410 <p><b>Description</b>
10411 <p><!--para 2 -->
10412 The casin functions compute the complex arc sine of z, with branch cuts outside the
10413 interval [-1, +1] along the real axis.
10414 <p><b>Returns</b>
10415 <p><!--para 3 -->
10416 The casin functions return the complex arc sine value, in the range of a strip
10417 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
10419 <!--page 209 -->
10420 along the real axis.
10424 <p><b>Synopsis</b>
10425 <p><!--para 1 -->
10426 <pre>
10428 double complex catan(double complex z);
10429 float complex catanf(float complex z);
10430 long double complex catanl(long double complex z);
10431 </pre>
10432 <p><b>Description</b>
10433 <p><!--para 2 -->
10434 The catan functions compute the complex arc tangent of z, with branch cuts outside the
10435 interval [-i, +i] along the imaginary axis.
10436 <p><b>Returns</b>
10437 <p><!--para 3 -->
10438 The catan functions return the complex arc tangent value, in the range of a strip
10439 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
10440 along the real axis.
10444 <p><b>Synopsis</b>
10445 <p><!--para 1 -->
10446 <pre>
10448 double complex ccos(double complex z);
10449 float complex ccosf(float complex z);
10450 long double complex ccosl(long double complex z);
10451 </pre>
10452 <p><b>Description</b>
10453 <p><!--para 2 -->
10454 The ccos functions compute the complex cosine of z.
10455 <p><b>Returns</b>
10456 <p><!--para 3 -->
10457 The ccos functions return the complex cosine value.
10461 <p><b>Synopsis</b>
10462 <p><!--para 1 -->
10463 <pre>
10465 double complex csin(double complex z);
10466 float complex csinf(float complex z);
10467 long double complex csinl(long double complex z);
10468 </pre>
10469 <p><b>Description</b>
10470 <p><!--para 2 -->
10471 The csin functions compute the complex sine of z.
10472 <!--page 210 -->
10473 <p><b>Returns</b>
10474 <p><!--para 3 -->
10475 The csin functions return the complex sine value.
10479 <p><b>Synopsis</b>
10480 <p><!--para 1 -->
10481 <pre>
10483 double complex ctan(double complex z);
10484 float complex ctanf(float complex z);
10485 long double complex ctanl(long double complex z);
10486 </pre>
10487 <p><b>Description</b>
10488 <p><!--para 2 -->
10489 The ctan functions compute the complex tangent of z.
10490 <p><b>Returns</b>
10491 <p><!--para 3 -->
10492 The ctan functions return the complex tangent value.
10499 <p><b>Synopsis</b>
10500 <p><!--para 1 -->
10501 <pre>
10503 double complex cacosh(double complex z);
10504 float complex cacoshf(float complex z);
10505 long double complex cacoshl(long double complex z);
10506 </pre>
10507 <p><b>Description</b>
10508 <p><!--para 2 -->
10509 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
10510 cut at values less than 1 along the real axis.
10511 <p><b>Returns</b>
10512 <p><!--para 3 -->
10513 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
10514 half-strip of nonnegative values along the real axis and in the interval [-ipi , +ipi ] along the
10515 imaginary axis.
10519 <p><b>Synopsis</b>
10520 <p><!--para 1 -->
10521 <!--page 211 -->
10522 <pre>
10524 double complex casinh(double complex z);
10525 float complex casinhf(float complex z);
10526 long double complex casinhl(long double complex z);
10527 </pre>
10528 <p><b>Description</b>
10529 <p><!--para 2 -->
10530 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
10531 outside the interval [-i, +i] along the imaginary axis.
10532 <p><b>Returns</b>
10533 <p><!--para 3 -->
10534 The casinh functions return the complex arc hyperbolic sine value, in the range of a
10535 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
10536 along the imaginary axis.
10540 <p><b>Synopsis</b>
10541 <p><!--para 1 -->
10542 <pre>
10544 double complex catanh(double complex z);
10545 float complex catanhf(float complex z);
10546 long double complex catanhl(long double complex z);
10547 </pre>
10548 <p><b>Description</b>
10549 <p><!--para 2 -->
10550 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
10551 cuts outside the interval [-1, +1] along the real axis.
10552 <p><b>Returns</b>
10553 <p><!--para 3 -->
10554 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
10555 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
10556 along the imaginary axis.
10560 <p><b>Synopsis</b>
10561 <p><!--para 1 -->
10562 <pre>
10564 double complex ccosh(double complex z);
10565 float complex ccoshf(float complex z);
10566 long double complex ccoshl(long double complex z);
10567 </pre>
10568 <p><b>Description</b>
10569 <p><!--para 2 -->
10570 The ccosh functions compute the complex hyperbolic cosine of z.
10571 <p><b>Returns</b>
10572 <p><!--para 3 -->
10573 The ccosh functions return the complex hyperbolic cosine value.
10574 <!--page 212 -->
10578 <p><b>Synopsis</b>
10579 <p><!--para 1 -->
10580 <pre>
10582 double complex csinh(double complex z);
10583 float complex csinhf(float complex z);
10584 long double complex csinhl(long double complex z);
10585 </pre>
10586 <p><b>Description</b>
10587 <p><!--para 2 -->
10588 The csinh functions compute the complex hyperbolic sine of z.
10589 <p><b>Returns</b>
10590 <p><!--para 3 -->
10591 The csinh functions return the complex hyperbolic sine value.
10595 <p><b>Synopsis</b>
10596 <p><!--para 1 -->
10597 <pre>
10599 double complex ctanh(double complex z);
10600 float complex ctanhf(float complex z);
10601 long double complex ctanhl(long double complex z);
10602 </pre>
10603 <p><b>Description</b>
10604 <p><!--para 2 -->
10605 The ctanh functions compute the complex hyperbolic tangent of z.
10606 <p><b>Returns</b>
10607 <p><!--para 3 -->
10608 The ctanh functions return the complex hyperbolic tangent value.
10615 <p><b>Synopsis</b>
10616 <p><!--para 1 -->
10617 <pre>
10619 double complex cexp(double complex z);
10620 float complex cexpf(float complex z);
10621 long double complex cexpl(long double complex z);
10622 </pre>
10623 <p><b>Description</b>
10624 <p><!--para 2 -->
10625 The cexp functions compute the complex base-e exponential of z.
10626 <p><b>Returns</b>
10627 <p><!--para 3 -->
10628 The cexp functions return the complex base-e exponential value.
10629 <!--page 213 -->
10633 <p><b>Synopsis</b>
10634 <p><!--para 1 -->
10635 <pre>
10637 double complex clog(double complex z);
10638 float complex clogf(float complex z);
10639 long double complex clogl(long double complex z);
10640 </pre>
10641 <p><b>Description</b>
10642 <p><!--para 2 -->
10643 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
10644 cut along the negative real axis.
10645 <p><b>Returns</b>
10646 <p><!--para 3 -->
10647 The clog functions return the complex natural logarithm value, in the range of a strip
10648 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
10649 imaginary axis.
10656 <p><b>Synopsis</b>
10657 <p><!--para 1 -->
10658 <pre>
10660 double cabs(double complex z);
10661 float cabsf(float complex z);
10662 long double cabsl(long double complex z);
10663 </pre>
10664 <p><b>Description</b>
10665 <p><!--para 2 -->
10666 The cabs functions compute the complex absolute value (also called norm, modulus, or
10667 magnitude) of z.
10668 <p><b>Returns</b>
10669 <p><!--para 3 -->
10670 The cabs functions return the complex absolute value.
10674 <p><b>Synopsis</b>
10675 <p><!--para 1 -->
10676 <!--page 214 -->
10677 <pre>
10679 double complex cpow(double complex x, double complex y);
10680 float complex cpowf(float complex x, float complex y);
10681 long double complex cpowl(long double complex x,
10682 long double complex y);
10683 </pre>
10684 <p><b>Description</b>
10685 <p><!--para 2 -->
10686 The cpow functions compute the complex power function xy , with a branch cut for the
10687 first parameter along the negative real axis.
10688 <p><b>Returns</b>
10689 <p><!--para 3 -->
10690 The cpow functions return the complex power function value.
10694 <p><b>Synopsis</b>
10695 <p><!--para 1 -->
10696 <pre>
10698 double complex csqrt(double complex z);
10699 float complex csqrtf(float complex z);
10700 long double complex csqrtl(long double complex z);
10701 </pre>
10702 <p><b>Description</b>
10703 <p><!--para 2 -->
10704 The csqrt functions compute the complex square root of z, with a branch cut along the
10705 negative real axis.
10706 <p><b>Returns</b>
10707 <p><!--para 3 -->
10708 The csqrt functions return the complex square root value, in the range of the right half-
10709 plane (including the imaginary axis).
10716 <p><b>Synopsis</b>
10717 <p><!--para 1 -->
10718 <pre>
10720 double carg(double complex z);
10721 float cargf(float complex z);
10722 long double cargl(long double complex z);
10723 </pre>
10724 <p><b>Description</b>
10725 <p><!--para 2 -->
10726 The carg functions compute the argument (also called phase angle) of z, with a branch
10727 cut along the negative real axis.
10728 <p><b>Returns</b>
10729 <p><!--para 3 -->
10730 The carg functions return the value of the argument in the interval [-pi , +pi ].
10731 <!--page 215 -->
10735 <p><b>Synopsis</b>
10736 <p><!--para 1 -->
10737 <pre>
10739 double cimag(double complex z);
10740 float cimagf(float complex z);
10741 long double cimagl(long double complex z);
10742 </pre>
10743 <p><b>Description</b>
10744 <p><!--para 2 -->
10745 The cimag functions compute the imaginary part of z.<sup><a href="#note196"><b>196)</b></a></sup>
10746 <p><b>Returns</b>
10747 <p><!--para 3 -->
10748 The cimag functions return the imaginary part value (as a real).
10750 <p><b>Footnotes</b>
10751 <p><small><a name="note196" href="#note196">196)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
10752 </small>
10756 <p><b>Synopsis</b>
10757 <p><!--para 1 -->
10758 <pre>
10760 double complex CMPLX(double x, double y);
10761 float complex CMPLXF(float x, float y);
10762 long double complex CMPLXL(long double x, long double y);
10763 </pre>
10764 <p><b>Description</b>
10765 <p><!--para 2 -->
10766 The CMPLX macros expand to an expression of the specified complex type, with the real
10767 part having the (converted) value of x and the imaginary part having the (converted)
10768 value of y. The resulting expression shall be suitable for use as an initializer for an object
10769 with static or thread storage duration, provided both arguments are likewise suitable.
10770 <p><b>Returns</b>
10771 <p><!--para 3 -->
10772 The CMPLX macros return the complex value x + i y.
10773 <p><!--para 4 -->
10774 NOTE These macros act as if the implementation supported imaginary types and the definitions were:
10775 <pre>
10776 #define CMPLX(x, y) ((double complex)((double)(x) + \
10777 _Imaginary_I * (double)(y)))
10778 #define CMPLXF(x, y) ((float complex)((float)(x) + \
10779 _Imaginary_I * (float)(y)))
10780 #define CMPLXL(x, y) ((long double complex)((long double)(x) + \
10781 _Imaginary_I * (long double)(y)))
10782 </pre>
10787 <!--page 216 -->
10791 <p><b>Synopsis</b>
10792 <p><!--para 1 -->
10793 <pre>
10795 double complex conj(double complex z);
10796 float complex conjf(float complex z);
10797 long double complex conjl(long double complex z);
10798 </pre>
10799 <p><b>Description</b>
10800 <p><!--para 2 -->
10801 The conj functions compute the complex conjugate of z, by reversing the sign of its
10802 imaginary part.
10803 <p><b>Returns</b>
10804 <p><!--para 3 -->
10805 The conj functions return the complex conjugate value.
10809 <p><b>Synopsis</b>
10810 <p><!--para 1 -->
10811 <pre>
10813 double complex cproj(double complex z);
10814 float complex cprojf(float complex z);
10815 long double complex cprojl(long double complex z);
10816 </pre>
10817 <p><b>Description</b>
10818 <p><!--para 2 -->
10819 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
10820 z except that all complex infinities (even those with one infinite part and one NaN part)
10821 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
10822 equivalent to
10823 <pre>
10824 INFINITY + I * copysign(0.0, cimag(z))
10825 </pre>
10826 <p><b>Returns</b>
10827 <p><!--para 3 -->
10828 The cproj functions return the value of the projection onto the Riemann sphere.
10832 <p><b>Synopsis</b>
10833 <p><!--para 1 -->
10834 <pre>
10836 double creal(double complex z);
10837 float crealf(float complex z);
10838 long double creall(long double complex z);
10839 </pre>
10840 <p><b>Description</b>
10841 <p><!--para 2 -->
10843 <!--page 217 -->
10844 <p><b>Returns</b>
10845 <p><!--para 3 -->
10846 The creal functions return the real part value.
10851 <!--page 218 -->
10853 <p><b>Footnotes</b>
10854 <p><small><a name="note197" href="#note197">197)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
10855 </small>
10859 <p><!--para 1 -->
10860 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
10861 characters.<sup><a href="#note198"><b>198)</b></a></sup> In all cases the argument is an int, the value of which shall be
10862 representable as an unsigned char or shall equal the value of the macro EOF. If the
10863 argument has any other value, the behavior is undefined.
10864 <p><!--para 2 -->
10865 The behavior of these functions is affected by the current locale. Those functions that
10867 <p><!--para 3 -->
10868 The term printing character refers to a member of a locale-specific set of characters, each
10869 of which occupies one printing position on a display device; the term control character
10870 refers to a member of a locale-specific set of characters that are not printing
10871 characters.<sup><a href="#note199"><b>199)</b></a></sup> All letters and digits are printing characters.
10872 <p><b> Forward references</b>: EOF (<a href="#7.21.1">7.21.1</a>), localization (<a href="#7.11">7.11</a>).
10874 <p><b>Footnotes</b>
10875 <p><small><a name="note198" href="#note198">198)</a> See ''future library directions'' (<a href="#7.31.2">7.31.2</a>).
10876 </small>
10877 <p><small><a name="note199" href="#note199">199)</a> In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
10878 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
10879 values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
10880 </small>
10884 <p><!--para 1 -->
10885 The functions in this subclause return nonzero (true) if and only if the value of the
10886 argument c conforms to that in the description of the function.
10890 <p><b>Synopsis</b>
10891 <p><!--para 1 -->
10892 <pre>
10894 int isalnum(int c);
10895 </pre>
10896 <p><b>Description</b>
10897 <p><!--para 2 -->
10898 The isalnum function tests for any character for which isalpha or isdigit is true.
10902 <p><b>Synopsis</b>
10903 <p><!--para 1 -->
10904 <pre>
10906 int isalpha(int c);
10907 </pre>
10908 <p><b>Description</b>
10909 <p><!--para 2 -->
10910 The isalpha function tests for any character for which isupper or islower is true,
10911 or any character that is one of a locale-specific set of alphabetic characters for which
10915 <!--page 219 -->
10916 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note200"><b>200)</b></a></sup> In the "C" locale,
10917 isalpha returns true only for the characters for which isupper or islower is true.
10919 <p><b>Footnotes</b>
10920 <p><small><a name="note200" href="#note200">200)</a> The functions islower and isupper test true or false separately for each of these additional
10921 characters; all four combinations are possible.
10922 </small>
10926 <p><b>Synopsis</b>
10927 <p><!--para 1 -->
10928 <pre>
10930 int isblank(int c);
10931 </pre>
10932 <p><b>Description</b>
10933 <p><!--para 2 -->
10934 The isblank function tests for any character that is a standard blank character or is one
10935 of a locale-specific set of characters for which isspace is true and that is used to
10936 separate words within a line of text. The standard blank characters are the following:
10938 for the standard blank characters.
10942 <p><b>Synopsis</b>
10943 <p><!--para 1 -->
10944 <pre>
10946 int iscntrl(int c);
10947 </pre>
10948 <p><b>Description</b>
10949 <p><!--para 2 -->
10950 The iscntrl function tests for any control character.
10954 <p><b>Synopsis</b>
10955 <p><!--para 1 -->
10956 <pre>
10958 int isdigit(int c);
10959 </pre>
10960 <p><b>Description</b>
10961 <p><!--para 2 -->
10962 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
10966 <p><b>Synopsis</b>
10967 <p><!--para 1 -->
10968 <pre>
10970 int isgraph(int c);
10971 </pre>
10976 <!--page 220 -->
10977 <p><b>Description</b>
10978 <p><!--para 2 -->
10979 The isgraph function tests for any printing character except space (' ').
10983 <p><b>Synopsis</b>
10984 <p><!--para 1 -->
10985 <pre>
10987 int islower(int c);
10988 </pre>
10989 <p><b>Description</b>
10990 <p><!--para 2 -->
10991 The islower function tests for any character that is a lowercase letter or is one of a
10992 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
10998 <p><b>Synopsis</b>
10999 <p><!--para 1 -->
11000 <pre>
11002 int isprint(int c);
11003 </pre>
11004 <p><b>Description</b>
11005 <p><!--para 2 -->
11006 The isprint function tests for any printing character including space (' ').
11010 <p><b>Synopsis</b>
11011 <p><!--para 1 -->
11012 <pre>
11014 int ispunct(int c);
11015 </pre>
11016 <p><b>Description</b>
11017 <p><!--para 2 -->
11018 The ispunct function tests for any printing character that is one of a locale-specific set
11020 locale, ispunct returns true for every printing character for which neither isspace
11021 nor isalnum is true.
11025 <p><b>Synopsis</b>
11026 <p><!--para 1 -->
11027 <pre>
11029 int isspace(int c);
11030 </pre>
11031 <p><b>Description</b>
11032 <p><!--para 2 -->
11033 The isspace function tests for any character that is a standard white-space character or
11034 is one of a locale-specific set of characters for which isalnum is false. The standard
11035 <!--page 221 -->
11036 white-space characters are the following: space (' '), form feed ('\f'), new-line
11037 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
11042 <p><b>Synopsis</b>
11043 <p><!--para 1 -->
11044 <pre>
11046 int isupper(int c);
11047 </pre>
11048 <p><b>Description</b>
11049 <p><!--para 2 -->
11050 The isupper function tests for any character that is an uppercase letter or is one of a
11051 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
11057 <p><b>Synopsis</b>
11058 <p><!--para 1 -->
11059 <pre>
11061 int isxdigit(int c);
11062 </pre>
11063 <p><b>Description</b>
11064 <p><!--para 2 -->
11065 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
11072 <p><b>Synopsis</b>
11073 <p><!--para 1 -->
11074 <pre>
11076 int tolower(int c);
11077 </pre>
11078 <p><b>Description</b>
11079 <p><!--para 2 -->
11080 The tolower function converts an uppercase letter to a corresponding lowercase letter.
11081 <p><b>Returns</b>
11082 <p><!--para 3 -->
11083 If the argument is a character for which isupper is true and there are one or more
11084 corresponding characters, as specified by the current locale, for which islower is true,
11085 the tolower function returns one of the corresponding characters (always the same one
11086 for any given locale); otherwise, the argument is returned unchanged.
11087 <!--page 222 -->
11091 <p><b>Synopsis</b>
11092 <p><!--para 1 -->
11093 <pre>
11095 int toupper(int c);
11096 </pre>
11097 <p><b>Description</b>
11098 <p><!--para 2 -->
11099 The toupper function converts a lowercase letter to a corresponding uppercase letter.
11100 <p><b>Returns</b>
11101 <p><!--para 3 -->
11102 If the argument is a character for which islower is true and there are one or more
11103 corresponding characters, as specified by the current locale, for which isupper is true,
11104 the toupper function returns one of the corresponding characters (always the same one
11105 for any given locale); otherwise, the argument is returned unchanged.
11106 <!--page 223 -->
11110 <p><!--para 1 -->
11111 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
11112 conditions.
11113 <p><!--para 2 -->
11114 The macros are
11115 <pre>
11116 EDOM
11117 EILSEQ
11118 ERANGE
11119 </pre>
11120 which expand to integer constant expressions with type int, distinct positive values, and
11121 which are suitable for use in #if preprocessing directives; and
11122 <pre>
11123 errno
11124 </pre>
11125 which expands to a modifiable lvalue<sup><a href="#note201"><b>201)</b></a></sup> that has type int and thread local storage
11126 duration, the value of which is set to a positive error number by several library functions.
11127 If a macro definition is suppressed in order to access an actual object, or a program
11128 defines an identifier with the name errno, the behavior is undefined.
11129 <p><!--para 3 -->
11130 The value of errno in the initial thread is zero at program startup (the initial value of
11131 errno in other threads is an indeterminate value), but is never set to zero by any library
11132 function.<sup><a href="#note202"><b>202)</b></a></sup> The value of errno may be set to nonzero by a library function call
11133 whether or not there is an error, provided the use of errno is not documented in the
11134 description of the function in this International Standard.
11135 <p><!--para 4 -->
11136 Additional macro definitions, beginning with E and a digit or E and an uppercase
11137 letter,<sup><a href="#note203"><b>203)</b></a></sup> may also be specified by the implementation.
11142 <!--page 224 -->
11144 <p><b>Footnotes</b>
11145 <p><small><a name="note201" href="#note201">201)</a> The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue
11146 resulting from a function call (for example, *errno()).
11147 </small>
11148 <p><small><a name="note202" href="#note202">202)</a> Thus, a program that uses errno for error checking should set it to zero before a library function call,
11149 then inspect it before a subsequent library function call. Of course, a library function can save the
11150 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
11151 value is still zero just before the return.
11152 </small>
11153 <p><small><a name="note203" href="#note203">203)</a> See ''future library directions'' (<a href="#7.31.3">7.31.3</a>).
11154 </small>
11158 <p><!--para 1 -->
11159 The header <a href="#7.6"><fenv.h></a> defines several macros, and declares types and functions that
11160 provide access to the floating-point environment. The floating-point environment refers
11161 collectively to any floating-point status flags and control modes supported by the
11162 implementation.<sup><a href="#note204"><b>204)</b></a></sup> A floating-point status flag is a system variable whose value is set
11163 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
11164 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note205"><b>205)</b></a></sup> A floating-
11165 point control mode is a system variable whose value may be set by the user to affect the
11166 subsequent behavior of floating-point arithmetic.
11167 <p><!--para 2 -->
11168 The floating-point environment has thread storage duration. The initial state for a
11169 thread's floating-point environment is the current state of the floating-point environment
11170 of the thread that creates it at the time of creation.
11171 <p><!--para 3 -->
11172 Certain programming conventions support the intended model of use for the floating-
11174 <ul>
11175 <li> a function call does not alter its caller's floating-point control modes, clear its caller's
11176 floating-point status flags, nor depend on the state of its caller's floating-point status
11177 flags unless the function is so documented;
11178 <li> a function call is assumed to require default floating-point control modes, unless its
11179 documentation promises otherwise;
11180 <li> a function call is assumed to have the potential for raising floating-point exceptions,
11181 unless its documentation promises otherwise.
11182 </ul>
11183 <p><!--para 4 -->
11184 The type
11185 <pre>
11186 fenv_t
11187 </pre>
11188 represents the entire floating-point environment.
11189 <p><!--para 5 -->
11190 The type
11191 <pre>
11192 fexcept_t
11193 </pre>
11194 represents the floating-point status flags collectively, including any status the
11195 implementation associates with the flags.
11198 <!--page 225 -->
11199 <p><!--para 6 -->
11200 Each of the macros
11201 <pre>
11202 FE_DIVBYZERO
11203 FE_INEXACT
11204 FE_INVALID
11205 FE_OVERFLOW
11206 FE_UNDERFLOW
11207 </pre>
11208 is defined if and only if the implementation supports the floating-point exception by
11209 means of the functions in 7.6.2.<sup><a href="#note207"><b>207)</b></a></sup> Additional implementation-defined floating-point
11210 exceptions, with macro definitions beginning with FE_ and an uppercase letter,<sup><a href="#note208"><b>208)</b></a></sup> may
11211 also be specified by the implementation. The defined macros expand to integer constant
11212 expressions with values such that bitwise ORs of all combinations of the macros result in
11213 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
11215 <p><!--para 7 -->
11216 The macro
11217 <pre>
11218 FE_ALL_EXCEPT
11219 </pre>
11220 is simply the bitwise OR of all floating-point exception macros defined by the
11221 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
11222 <p><!--para 8 -->
11223 Each of the macros
11224 <pre>
11225 FE_DOWNWARD
11226 FE_TONEAREST
11227 FE_TOWARDZERO
11228 FE_UPWARD
11229 </pre>
11230 is defined if and only if the implementation supports getting and setting the represented
11231 rounding direction by means of the fegetround and fesetround functions.
11232 Additional implementation-defined rounding directions, with macro definitions beginning
11233 with FE_ and an uppercase letter,<sup><a href="#note210"><b>210)</b></a></sup> may also be specified by the implementation. The
11234 defined macros expand to integer constant expressions whose values are distinct
11238 <!--page 226 -->
11239 <p><!--para 9 -->
11240 The macro
11241 <pre>
11242 FE_DFL_ENV
11243 </pre>
11244 represents the default floating-point environment -- the one installed at program startup
11245 <ul>
11246 <li> and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
11247 </ul>
11249 <p><!--para 10 -->
11250 Additional implementation-defined environments, with macro definitions beginning with
11251 FE_ and an uppercase letter,<sup><a href="#note212"><b>212)</b></a></sup> and having type ''pointer to const-qualified fenv_t'',
11252 may also be specified by the implementation.
11254 <p><b>Footnotes</b>
11255 <p><small><a name="note204" href="#note204">204)</a> This header is designed to support the floating-point exception status flags and directed-rounding
11256 control modes required by IEC 60559, and other similar floating-point state information. It is also
11257 designed to facilitate code portability among all systems.
11258 </small>
11259 <p><small><a name="note205" href="#note205">205)</a> A floating-point status flag is not an object and can be set more than once within an expression.
11260 </small>
11261 <p><small><a name="note206" href="#note206">206)</a> With these conventions, a programmer can safely assume default floating-point control modes (or be
11262 unaware of them). The responsibilities associated with accessing the floating-point environment fall
11263 on the programmer or program that does so explicitly.
11264 </small>
11265 <p><small><a name="note207" href="#note207">207)</a> The implementation supports a floating-point exception if there are circumstances where a call to at
11266 least one of the functions in <a href="#7.6.2">7.6.2</a>, using the macro as the appropriate argument, will succeed. It is not
11267 necessary for all the functions to succeed all the time.
11268 </small>
11269 <p><small><a name="note208" href="#note208">208)</a> See ''future library directions'' (<a href="#7.31.4">7.31.4</a>).
11270 </small>
11271 <p><small><a name="note209" href="#note209">209)</a> The macros should be distinct powers of two.
11272 </small>
11273 <p><small><a name="note210" href="#note210">210)</a> See ''future library directions'' (<a href="#7.31.4">7.31.4</a>).
11274 </small>
11275 <p><small><a name="note211" href="#note211">211)</a> Even though the rounding direction macros may expand to constants corresponding to the values of
11276 FLT_ROUNDS, they are not required to do so.
11277 </small>
11278 <p><small><a name="note212" href="#note212">212)</a> See ''future library directions'' (<a href="#7.31.4">7.31.4</a>).
11279 </small>
11283 <p><b>Synopsis</b>
11284 <p><!--para 1 -->
11285 <pre>
11287 #pragma STDC FENV_ACCESS on-off-switch
11288 </pre>
11289 <p><b>Description</b>
11290 <p><!--para 2 -->
11291 The FENV_ACCESS pragma provides a means to inform the implementation when a
11292 program might access the floating-point environment to test floating-point status flags or
11293 run under non-default floating-point control modes.<sup><a href="#note213"><b>213)</b></a></sup> The pragma shall occur either
11294 outside external declarations or preceding all explicit declarations and statements inside a
11295 compound statement. When outside external declarations, the pragma takes effect from
11296 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
11297 the translation unit. When inside a compound statement, the pragma takes effect from its
11298 occurrence until another FENV_ACCESS pragma is encountered (including within a
11299 nested compound statement), or until the end of the compound statement; at the end of a
11300 compound statement the state for the pragma is restored to its condition just before the
11301 compound statement. If this pragma is used in any other context, the behavior is
11302 undefined. If part of a program tests floating-point status flags, sets floating-point control
11303 modes, or runs under non-default mode settings, but was translated with the state for the
11304 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
11305 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
11306 the program translated with FENV_ACCESS ''off'' to a part translated with
11307 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
11308 floating-point control modes have their default settings.)
11312 <!--page 227 -->
11313 <p><!--para 3 -->
11314 EXAMPLE
11315 <pre>
11317 void f(double x)
11318 {
11319 #pragma STDC FENV_ACCESS ON
11320 void g(double);
11321 void h(double);
11322 /* ... */
11323 g(x + 1);
11324 h(x + 1);
11325 /* ... */
11326 }
11327 </pre>
11328 <p><!--para 4 -->
11329 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
11330 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
11331 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note214"><b>214)</b></a></sup>
11334 <p><b>Footnotes</b>
11335 <p><small><a name="note213" href="#note213">213)</a> The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
11336 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
11337 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
11338 modes are in effect and the flags are not tested.
11339 </small>
11340 <p><small><a name="note214" href="#note214">214)</a> The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
11341 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
11342 ''off'', just one evaluation of x + 1 would suffice.
11343 </small>
11347 <p><!--para 1 -->
11348 The following functions provide access to the floating-point status flags.<sup><a href="#note215"><b>215)</b></a></sup> The int
11349 input argument for the functions represents a subset of floating-point exceptions, and can
11350 be zero or the bitwise OR of one or more floating-point exception macros, for example
11351 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
11352 functions is undefined.
11354 <p><b>Footnotes</b>
11355 <p><small><a name="note215" href="#note215">215)</a> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
11356 abstraction of flags that are either set or clear. An implementation may endow floating-point status
11357 flags with more information -- for example, the address of the code which first raised the floating-
11358 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
11359 content of flags.
11360 </small>
11364 <p><b>Synopsis</b>
11365 <p><!--para 1 -->
11366 <pre>
11368 int feclearexcept(int excepts);
11369 </pre>
11370 <p><b>Description</b>
11371 <p><!--para 2 -->
11372 The feclearexcept function attempts to clear the supported floating-point exceptions
11373 represented by its argument.
11374 <p><b>Returns</b>
11375 <p><!--para 3 -->
11376 The feclearexcept function returns zero if the excepts argument is zero or if all
11377 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
11380 <!--page 228 -->
11384 <p><b>Synopsis</b>
11385 <p><!--para 1 -->
11386 <pre>
11388 int fegetexceptflag(fexcept_t *flagp,
11389 int excepts);
11390 </pre>
11391 <p><b>Description</b>
11392 <p><!--para 2 -->
11393 The fegetexceptflag function attempts to store an implementation-defined
11394 representation of the states of the floating-point status flags indicated by the argument
11395 excepts in the object pointed to by the argument flagp.
11396 <p><b>Returns</b>
11397 <p><!--para 3 -->
11398 The fegetexceptflag function returns zero if the representation was successfully
11399 stored. Otherwise, it returns a nonzero value.
11403 <p><b>Synopsis</b>
11404 <p><!--para 1 -->
11405 <pre>
11407 int feraiseexcept(int excepts);
11408 </pre>
11409 <p><b>Description</b>
11410 <p><!--para 2 -->
11411 The feraiseexcept function attempts to raise the supported floating-point exceptions
11412 represented by its argument.<sup><a href="#note216"><b>216)</b></a></sup> The order in which these floating-point exceptions are
11413 raised is unspecified, except as stated in <a href="#F.8.6">F.8.6</a>. Whether the feraiseexcept function
11414 additionally raises the ''inexact'' floating-point exception whenever it raises the
11415 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
11416 <p><b>Returns</b>
11417 <p><!--para 3 -->
11418 The feraiseexcept function returns zero if the excepts argument is zero or if all
11419 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
11424 <!--page 229 -->
11426 <p><b>Footnotes</b>
11427 <p><small><a name="note216" href="#note216">216)</a> The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
11428 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
11430 </small>
11434 <p><b>Synopsis</b>
11435 <p><!--para 1 -->
11436 <pre>
11438 int fesetexceptflag(const fexcept_t *flagp,
11439 int excepts);
11440 </pre>
11441 <p><b>Description</b>
11442 <p><!--para 2 -->
11443 The fesetexceptflag function attempts to set the floating-point status flags
11444 indicated by the argument excepts to the states stored in the object pointed to by
11445 flagp. The value of *flagp shall have been set by a previous call to
11446 fegetexceptflag whose second argument represented at least those floating-point
11447 exceptions represented by the argument excepts. This function does not raise floating-
11448 point exceptions, but only sets the state of the flags.
11449 <p><b>Returns</b>
11450 <p><!--para 3 -->
11451 The fesetexceptflag function returns zero if the excepts argument is zero or if
11452 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
11453 a nonzero value.
11457 <p><b>Synopsis</b>
11458 <p><!--para 1 -->
11459 <pre>
11461 int fetestexcept(int excepts);
11462 </pre>
11463 <p><b>Description</b>
11464 <p><!--para 2 -->
11465 The fetestexcept function determines which of a specified subset of the floating-
11466 point exception flags are currently set. The excepts argument specifies the floating-
11468 <p><b>Returns</b>
11469 <p><!--para 3 -->
11470 The fetestexcept function returns the value of the bitwise OR of the floating-point
11471 exception macros corresponding to the currently set floating-point exceptions included in
11472 excepts.
11473 <p><!--para 4 -->
11474 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
11479 <!--page 230 -->
11480 <pre>
11482 /* ... */
11483 {
11484 #pragma STDC FENV_ACCESS ON
11485 int set_excepts;
11486 feclearexcept(FE_INVALID | FE_OVERFLOW);
11487 // maybe raise exceptions
11488 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
11489 if (set_excepts & FE_INVALID) f();
11490 if (set_excepts & FE_OVERFLOW) g();
11491 /* ... */
11492 }
11493 </pre>
11496 <p><b>Footnotes</b>
11497 <p><small><a name="note217" href="#note217">217)</a> This mechanism allows testing several floating-point exceptions with just one function call.
11498 </small>
11502 <p><!--para 1 -->
11503 The fegetround and fesetround functions provide control of rounding direction
11504 modes.
11508 <p><b>Synopsis</b>
11509 <p><!--para 1 -->
11510 <pre>
11512 int fegetround(void);
11513 </pre>
11514 <p><b>Description</b>
11515 <p><!--para 2 -->
11516 The fegetround function gets the current rounding direction.
11517 <p><b>Returns</b>
11518 <p><!--para 3 -->
11519 The fegetround function returns the value of the rounding direction macro
11520 representing the current rounding direction or a negative value if there is no such
11521 rounding direction macro or the current rounding direction is not determinable.
11525 <p><b>Synopsis</b>
11526 <p><!--para 1 -->
11527 <pre>
11529 int fesetround(int round);
11530 </pre>
11531 <p><b>Description</b>
11532 <p><!--para 2 -->
11533 The fesetround function establishes the rounding direction represented by its
11534 argument round. If the argument is not equal to the value of a rounding direction macro,
11535 the rounding direction is not changed.
11536 <p><b>Returns</b>
11537 <p><!--para 3 -->
11538 The fesetround function returns zero if and only if the requested rounding direction
11539 was established.
11540 <!--page 231 -->
11541 <p><!--para 4 -->
11542 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
11543 rounding direction fails.
11544 <pre>
11547 void f(int round_dir)
11548 {
11549 #pragma STDC FENV_ACCESS ON
11550 int save_round;
11551 int setround_ok;
11552 save_round = fegetround();
11553 setround_ok = fesetround(round_dir);
11554 assert(setround_ok == 0);
11555 /* ... */
11556 fesetround(save_round);
11557 /* ... */
11558 }
11559 </pre>
11564 <p><!--para 1 -->
11565 The functions in this section manage the floating-point environment -- status flags and
11566 control modes -- as one entity.
11570 <p><b>Synopsis</b>
11571 <p><!--para 1 -->
11572 <pre>
11574 int fegetenv(fenv_t *envp);
11575 </pre>
11576 <p><b>Description</b>
11577 <p><!--para 2 -->
11578 The fegetenv function attempts to store the current floating-point environment in the
11579 object pointed to by envp.
11580 <p><b>Returns</b>
11581 <p><!--para 3 -->
11582 The fegetenv function returns zero if the environment was successfully stored.
11583 Otherwise, it returns a nonzero value.
11587 <p><b>Synopsis</b>
11588 <p><!--para 1 -->
11589 <pre>
11591 int feholdexcept(fenv_t *envp);
11592 </pre>
11593 <p><b>Description</b>
11594 <p><!--para 2 -->
11595 The feholdexcept function saves the current floating-point environment in the object
11596 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
11597 (continue on floating-point exceptions) mode, if available, for all floating-point
11599 <!--page 232 -->
11600 <p><b>Returns</b>
11601 <p><!--para 3 -->
11602 The feholdexcept function returns zero if and only if non-stop floating-point
11603 exception handling was successfully installed.
11605 <p><b>Footnotes</b>
11606 <p><small><a name="note218" href="#note218">218)</a> IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
11607 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
11608 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
11609 function to write routines that hide spurious floating-point exceptions from their callers.
11610 </small>
11614 <p><b>Synopsis</b>
11615 <p><!--para 1 -->
11616 <pre>
11618 int fesetenv(const fenv_t *envp);
11619 </pre>
11620 <p><b>Description</b>
11621 <p><!--para 2 -->
11622 The fesetenv function attempts to establish the floating-point environment represented
11623 by the object pointed to by envp. The argument envp shall point to an object set by a
11624 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
11625 Note that fesetenv merely installs the state of the floating-point status flags
11626 represented through its argument, and does not raise these floating-point exceptions.
11627 <p><b>Returns</b>
11628 <p><!--para 3 -->
11629 The fesetenv function returns zero if the environment was successfully established.
11630 Otherwise, it returns a nonzero value.
11634 <p><b>Synopsis</b>
11635 <p><!--para 1 -->
11636 <pre>
11638 int feupdateenv(const fenv_t *envp);
11639 </pre>
11640 <p><b>Description</b>
11641 <p><!--para 2 -->
11642 The feupdateenv function attempts to save the currently raised floating-point
11643 exceptions in its automatic storage, install the floating-point environment represented by
11644 the object pointed to by envp, and then raise the saved floating-point exceptions. The
11645 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
11646 or equal a floating-point environment macro.
11647 <p><b>Returns</b>
11648 <p><!--para 3 -->
11649 The feupdateenv function returns zero if all the actions were successfully carried out.
11650 Otherwise, it returns a nonzero value.
11655 <!--page 233 -->
11656 <p><!--para 4 -->
11657 EXAMPLE Hide spurious underflow floating-point exceptions:
11658 <!--page 234 -->
11659 <pre>
11661 double f(double x)
11662 {
11663 #pragma STDC FENV_ACCESS ON
11664 double result;
11665 fenv_t save_env;
11666 if (feholdexcept(&save_env))
11667 return /* indication of an environmental problem */;
11668 // compute result
11669 if (/* test spurious underflow */)
11670 if (feclearexcept(FE_UNDERFLOW))
11671 return /* indication of an environmental problem */;
11672 if (feupdateenv(&save_env))
11673 return /* indication of an environmental problem */;
11674 return result;
11675 }
11676 </pre>
11680 <p><!--para 1 -->
11681 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
11682 parameters of the standard floating-point types.
11683 <p><!--para 2 -->
11684 The macros, their meanings, and the constraints (or restrictions) on their values are listed
11686 <!--page 235 -->
11689 <h3><a name="7.8" href="#7.8">7.8 Format conversion of integer types <inttypes.h></a></h3>
11690 <p><!--para 1 -->
11691 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.20"><stdint.h></a> and extends it with
11692 additional facilities provided by hosted implementations.
11693 <p><!--para 2 -->
11694 It declares functions for manipulating greatest-width integers and converting numeric
11695 character strings to greatest-width integers, and it declares the type
11696 <pre>
11697 imaxdiv_t
11698 </pre>
11699 which is a structure type that is the type of the value returned by the imaxdiv function.
11700 For each type declared in <a href="#7.20"><stdint.h></a>, it defines corresponding macros for conversion
11701 specifiers for use with the formatted input/output functions.<sup><a href="#note219"><b>219)</b></a></sup>
11702 <p><b> Forward references</b>: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>), formatted input/output
11703 functions (<a href="#7.21.6">7.21.6</a>), formatted wide character input/output functions (<a href="#7.29.2">7.29.2</a>).
11705 <p><b>Footnotes</b>
11706 <p><small><a name="note219" href="#note219">219)</a> See ''future library directions'' (<a href="#7.31.5">7.31.5</a>).
11707 </small>
11711 <p><!--para 1 -->
11712 Each of the following object-like macros expands to a character string literal containing a
11713 conversion specifier, possibly modified by a length modifier, suitable for use within the
11714 format argument of a formatted input/output function when converting the corresponding
11715 integer type. These macro names have the general form of PRI (character string literals
11716 for the fprintf and fwprintf family) or SCN (character string literals for the
11717 fscanf and fwscanf family),<sup><a href="#note220"><b>220)</b></a></sup> followed by the conversion specifier, followed by a
11718 name corresponding to a similar type name in <a href="#7.20.1">7.20.1</a>. In these names, N represents the
11719 width of the type as described in <a href="#7.20.1">7.20.1</a>. For example, PRIdFAST32 can be used in a
11720 format string to print the value of an integer of type int_fast32_t.
11721 <p><!--para 2 -->
11722 The fprintf macros for signed integers are:
11723 <pre>
11724 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
11725 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
11726 </pre>
11727 <p><!--para 3 -->
11728 The fprintf macros for unsigned integers are:
11729 <pre>
11730 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
11731 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
11732 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
11733 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
11734 </pre>
11735 <p><!--para 4 -->
11736 The fscanf macros for signed integers are:
11740 <!--page 236 -->
11741 <pre>
11742 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
11743 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
11744 </pre>
11745 <p><!--para 5 -->
11746 The fscanf macros for unsigned integers are:
11747 <pre>
11748 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
11749 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
11750 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
11751 </pre>
11752 <p><!--para 6 -->
11753 For each type that the implementation provides in <a href="#7.20"><stdint.h></a>, the corresponding
11754 fprintf macros shall be defined and the corresponding fscanf macros shall be
11755 defined unless the implementation does not have a suitable fscanf length modifier for
11756 the type.
11757 <p><!--para 7 -->
11758 EXAMPLE
11759 <pre>
11762 int main(void)
11763 {
11764 uintmax_t i = UINTMAX_MAX; // this type always exists
11767 return 0;
11768 }
11769 </pre>
11772 <p><b>Footnotes</b>
11773 <p><small><a name="note220" href="#note220">220)</a> Separate macros are given for use with fprintf and fscanf functions because, in the general case,
11774 different format specifiers may be required for fprintf and fscanf, even when the type is the
11775 same.
11776 </small>
11783 <p><b>Synopsis</b>
11784 <p><!--para 1 -->
11785 <pre>
11787 intmax_t imaxabs(intmax_t j);
11788 </pre>
11789 <p><b>Description</b>
11790 <p><!--para 2 -->
11791 The imaxabs function computes the absolute value of an integer j. If the result cannot
11793 <p><b>Returns</b>
11794 <p><!--para 3 -->
11795 The imaxabs function returns the absolute value.
11800 <!--page 237 -->
11802 <p><b>Footnotes</b>
11803 <p><small><a name="note221" href="#note221">221)</a> The absolute value of the most negative number cannot be represented in two's complement.
11804 </small>
11808 <p><b>Synopsis</b>
11809 <p><!--para 1 -->
11810 <pre>
11812 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
11813 </pre>
11814 <p><b>Description</b>
11815 <p><!--para 2 -->
11816 The imaxdiv function computes numer / denom and numer % denom in a single
11817 operation.
11818 <p><b>Returns</b>
11819 <p><!--para 3 -->
11820 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
11821 quotient and the remainder. The structure shall contain (in either order) the members
11822 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
11823 either part of the result cannot be represented, the behavior is undefined.
11827 <p><b>Synopsis</b>
11828 <p><!--para 1 -->
11829 <pre>
11831 intmax_t strtoimax(const char * restrict nptr,
11832 char ** restrict endptr, int base);
11833 uintmax_t strtoumax(const char * restrict nptr,
11834 char ** restrict endptr, int base);
11835 </pre>
11836 <p><b>Description</b>
11837 <p><!--para 2 -->
11838 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
11839 strtoul, and strtoull functions, except that the initial portion of the string is
11840 converted to intmax_t and uintmax_t representation, respectively.
11841 <p><b>Returns</b>
11842 <p><!--para 3 -->
11843 The strtoimax and strtoumax functions return the converted value, if any. If no
11844 conversion could be performed, zero is returned. If the correct value is outside the range
11845 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
11846 (according to the return type and sign of the value, if any), and the value of the macro
11847 ERANGE is stored in errno.
11848 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
11850 <!--page 238 -->
11854 <p><b>Synopsis</b>
11855 <p><!--para 1 -->
11856 <pre>
11859 intmax_t wcstoimax(const wchar_t * restrict nptr,
11860 wchar_t ** restrict endptr, int base);
11861 uintmax_t wcstoumax(const wchar_t * restrict nptr,
11862 wchar_t ** restrict endptr, int base);
11863 </pre>
11864 <p><b>Description</b>
11865 <p><!--para 2 -->
11866 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
11867 wcstoul, and wcstoull functions except that the initial portion of the wide string is
11868 converted to intmax_t and uintmax_t representation, respectively.
11869 <p><b>Returns</b>
11870 <p><!--para 3 -->
11871 The wcstoimax function returns the converted value, if any. If no conversion could be
11872 performed, zero is returned. If the correct value is outside the range of representable
11873 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
11874 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
11875 errno.
11876 <p><b> Forward references</b>: the wcstol, wcstoll, wcstoul, and wcstoull functions
11878 <!--page 239 -->
11882 <p><!--para 1 -->
11883 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
11884 to the corresponding tokens (on the right):
11885 <!--page 240 -->
11886 <pre>
11887 and &&
11888 and_eq &=
11889 bitand &
11890 bitor |
11891 compl ~
11892 not !
11893 not_eq !=
11894 or ||
11895 or_eq |=
11896 xor ^
11897 xor_eq ^=
11898 </pre>
11902 <p><!--para 1 -->
11903 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
11904 parameters of the standard integer types.
11905 <p><!--para 2 -->
11906 The macros, their meanings, and the constraints (or restrictions) on their values are listed
11908 <!--page 241 -->
11912 <p><!--para 1 -->
11913 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
11914 <p><!--para 2 -->
11915 The type is
11916 <pre>
11917 struct lconv
11918 </pre>
11919 which contains members related to the formatting of numeric values. The structure shall
11920 contain at least the following members, in any order. The semantics of the members and
11921 their normal ranges are explained in <a href="#7.11.2.1">7.11.2.1</a>. In the "C" locale, the members shall have
11922 the values specified in the comments.
11923 <!--page 242 -->
11924 <pre>
11934 char frac_digits; // CHAR_MAX
11935 char p_cs_precedes; // CHAR_MAX
11936 char n_cs_precedes; // CHAR_MAX
11937 char p_sep_by_space; // CHAR_MAX
11938 char n_sep_by_space; // CHAR_MAX
11939 char p_sign_posn; // CHAR_MAX
11940 char n_sign_posn; // CHAR_MAX
11942 char int_frac_digits; // CHAR_MAX
11943 char int_p_cs_precedes; // CHAR_MAX
11944 char int_n_cs_precedes; // CHAR_MAX
11945 char int_p_sep_by_space; // CHAR_MAX
11946 char int_n_sep_by_space; // CHAR_MAX
11947 char int_p_sign_posn; // CHAR_MAX
11948 char int_n_sign_posn; // CHAR_MAX
11949 </pre>
11950 <p><!--para 3 -->
11952 <pre>
11953 LC_ALL
11954 LC_COLLATE
11955 LC_CTYPE
11956 LC_MONETARY
11957 LC_NUMERIC
11958 LC_TIME
11959 </pre>
11960 which expand to integer constant expressions with distinct values, suitable for use as the
11961 first argument to the setlocale function.<sup><a href="#note222"><b>222)</b></a></sup> Additional macro definitions, beginning
11962 with the characters LC_ and an uppercase letter,<sup><a href="#note223"><b>223)</b></a></sup> may also be specified by the
11963 implementation.
11965 <p><b>Footnotes</b>
11966 <p><small><a name="note222" href="#note222">222)</a> ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
11967 </small>
11968 <p><small><a name="note223" href="#note223">223)</a> See ''future library directions'' (<a href="#7.31.6">7.31.6</a>).
11969 </small>
11976 <p><b>Synopsis</b>
11977 <p><!--para 1 -->
11978 <pre>
11980 char *setlocale(int category, const char *locale);
11981 </pre>
11982 <p><b>Description</b>
11983 <p><!--para 2 -->
11984 The setlocale function selects the appropriate portion of the program's locale as
11985 specified by the category and locale arguments. The setlocale function may be
11986 used to change or query the program's entire current locale or portions thereof. The value
11987 LC_ALL for category names the program's entire locale; the other values for
11988 category name only a portion of the program's locale. LC_COLLATE affects the
11989 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
11990 the character handling functions<sup><a href="#note224"><b>224)</b></a></sup> and the multibyte and wide character functions.
11991 LC_MONETARY affects the monetary formatting information returned by the
11992 localeconv function. LC_NUMERIC affects the decimal-point character for the
11993 formatted input/output functions and the string conversion functions, as well as the
11994 nonmonetary formatting information returned by the localeconv function. LC_TIME
11995 affects the behavior of the strftime and wcsftime functions.
11996 <p><!--para 3 -->
11999 implementation-defined strings may be passed as the second argument to setlocale.
12001 <!--page 243 -->
12002 <p><!--para 4 -->
12003 At program startup, the equivalent of
12004 <pre>
12006 </pre>
12007 is executed.
12008 <p><!--para 5 -->
12009 A call to the setlocale function may introduce a data race with other calls to the
12010 setlocale function or with calls to functions that are affected by the current locale.
12011 The implementation shall behave as if no library function calls the setlocale function.
12012 <p><b>Returns</b>
12013 <p><!--para 6 -->
12014 If a pointer to a string is given for locale and the selection can be honored, the
12015 setlocale function returns a pointer to the string associated with the specified
12016 category for the new locale. If the selection cannot be honored, the setlocale
12017 function returns a null pointer and the program's locale is not changed.
12018 <p><!--para 7 -->
12019 A null pointer for locale causes the setlocale function to return a pointer to the
12020 string associated with the category for the program's current locale; the program's
12022 <p><!--para 8 -->
12023 The pointer to string returned by the setlocale function is such that a subsequent call
12024 with that string value and its associated category will restore that part of the program's
12025 locale. The string pointed to shall not be modified by the program, but may be
12026 overwritten by a subsequent call to the setlocale function.
12027 <p><b> Forward references</b>: formatted input/output functions (<a href="#7.21.6">7.21.6</a>), multibyte/wide
12028 character conversion functions (<a href="#7.22.7">7.22.7</a>), multibyte/wide string conversion functions
12029 (<a href="#7.22.8">7.22.8</a>), numeric conversion functions (<a href="#7.22.1">7.22.1</a>), the strcoll function (<a href="#7.24.4.3">7.24.4.3</a>), the
12030 strftime function (<a href="#7.27.3.5">7.27.3.5</a>), the strxfrm function (<a href="#7.24.4.5">7.24.4.5</a>).
12032 <p><b>Footnotes</b>
12033 <p><small><a name="note224" href="#note224">224)</a> The only functions in <a href="#7.4">7.4</a> whose behavior is not affected by the current locale are isdigit and
12034 isxdigit.
12035 </small>
12036 <p><small><a name="note225" href="#note225">225)</a> The implementation shall arrange to encode in a string the various categories due to a heterogeneous
12037 locale when category has the value LC_ALL.
12038 </small>
12045 <p><b>Synopsis</b>
12046 <p><!--para 1 -->
12047 <pre>
12049 struct lconv *localeconv(void);
12050 </pre>
12051 <p><b>Description</b>
12052 <p><!--para 2 -->
12053 The localeconv function sets the components of an object with type struct lconv
12054 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
12055 according to the rules of the current locale.
12059 <!--page 244 -->
12060 <p><!--para 3 -->
12061 The members of the structure with type char * are pointers to strings, any of which
12063 the current locale or is of zero length. Apart from grouping and mon_grouping, the
12064 strings shall start and end in the initial shift state. The members with type char are
12065 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
12066 available in the current locale. The members include the following:
12067 char *decimal_point
12068 <pre>
12069 The decimal-point character used to format nonmonetary quantities.
12070 </pre>
12071 char *thousands_sep
12072 <pre>
12073 The character used to separate groups of digits before the decimal-point
12074 character in formatted nonmonetary quantities.
12075 </pre>
12076 char *grouping
12077 <pre>
12078 A string whose elements indicate the size of each group of digits in
12079 formatted nonmonetary quantities.
12080 </pre>
12081 char *mon_decimal_point
12082 <pre>
12083 The decimal-point used to format monetary quantities.
12084 </pre>
12085 char *mon_thousands_sep
12086 <pre>
12087 The separator for groups of digits before the decimal-point in formatted
12088 monetary quantities.
12089 </pre>
12090 char *mon_grouping
12091 <pre>
12092 A string whose elements indicate the size of each group of digits in
12093 formatted monetary quantities.
12094 </pre>
12095 char *positive_sign
12096 <pre>
12097 The string used to indicate a nonnegative-valued formatted monetary
12098 quantity.
12099 </pre>
12100 char *negative_sign
12101 <pre>
12102 The string used to indicate a negative-valued formatted monetary quantity.
12103 </pre>
12104 char *currency_symbol
12105 <pre>
12106 The local currency symbol applicable to the current locale.
12107 </pre>
12108 char frac_digits
12109 <pre>
12110 The number of fractional digits (those after the decimal-point) to be
12111 displayed in a locally formatted monetary quantity.
12112 </pre>
12113 char p_cs_precedes
12114 <!--page 245 -->
12115 <pre>
12116 Set to 1 or 0 if the currency_symbol respectively precedes or
12117 succeeds the value for a nonnegative locally formatted monetary quantity.
12118 </pre>
12119 char n_cs_precedes
12120 <pre>
12121 Set to 1 or 0 if the currency_symbol respectively precedes or
12122 succeeds the value for a negative locally formatted monetary quantity.
12123 </pre>
12124 char p_sep_by_space
12125 <pre>
12126 Set to a value indicating the separation of the currency_symbol, the
12127 sign string, and the value for a nonnegative locally formatted monetary
12128 quantity.
12129 </pre>
12130 char n_sep_by_space
12131 <pre>
12132 Set to a value indicating the separation of the currency_symbol, the
12133 sign string, and the value for a negative locally formatted monetary
12134 quantity.
12135 </pre>
12136 char p_sign_posn
12137 <pre>
12138 Set to a value indicating the positioning of the positive_sign for a
12139 nonnegative locally formatted monetary quantity.
12140 </pre>
12141 char n_sign_posn
12142 <pre>
12143 Set to a value indicating the positioning of the negative_sign for a
12144 negative locally formatted monetary quantity.
12145 </pre>
12146 char *int_curr_symbol
12147 <pre>
12148 The international currency symbol applicable to the current locale. The
12149 first three characters contain the alphabetic international currency symbol
12150 in accordance with those specified in ISO 4217. The fourth character
12151 (immediately preceding the null character) is the character used to separate
12152 the international currency symbol from the monetary quantity.
12153 </pre>
12154 char int_frac_digits
12155 <pre>
12156 The number of fractional digits (those after the decimal-point) to be
12157 displayed in an internationally formatted monetary quantity.
12158 </pre>
12159 char int_p_cs_precedes
12160 <pre>
12161 Set to 1 or 0 if the int_curr_symbol respectively precedes or
12162 succeeds the value for a nonnegative internationally formatted monetary
12163 quantity.
12164 </pre>
12165 char int_n_cs_precedes
12166 <pre>
12167 Set to 1 or 0 if the int_curr_symbol respectively precedes or
12168 succeeds the value for a negative internationally formatted monetary
12169 quantity.
12170 </pre>
12171 char int_p_sep_by_space
12172 <!--page 246 -->
12173 <pre>
12174 Set to a value indicating the separation of the int_curr_symbol, the
12175 sign string, and the value for a nonnegative internationally formatted
12176 monetary quantity.
12177 </pre>
12178 char int_n_sep_by_space
12179 <pre>
12180 Set to a value indicating the separation of the int_curr_symbol, the
12181 sign string, and the value for a negative internationally formatted monetary
12182 quantity.
12183 </pre>
12184 char int_p_sign_posn
12185 <pre>
12186 Set to a value indicating the positioning of the positive_sign for a
12187 nonnegative internationally formatted monetary quantity.
12188 </pre>
12189 char int_n_sign_posn
12190 <pre>
12191 Set to a value indicating the positioning of the negative_sign for a
12192 negative internationally formatted monetary quantity.
12193 </pre>
12194 <p><!--para 4 -->
12195 The elements of grouping and mon_grouping are interpreted according to the
12196 following:
12197 CHAR_MAX No further grouping is to be performed.
12198 0 The previous element is to be repeatedly used for the remainder of the
12199 <pre>
12200 digits.
12201 </pre>
12202 other The integer value is the number of digits that compose the current group.
12203 <pre>
12204 The next element is examined to determine the size of the next group of
12205 digits before the current group.
12206 </pre>
12207 <p><!--para 5 -->
12208 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
12209 and int_n_sep_by_space are interpreted according to the following:
12210 0 No space separates the currency symbol and value.
12211 1 If the currency symbol and sign string are adjacent, a space separates them from the
12212 <pre>
12213 value; otherwise, a space separates the currency symbol from the value.
12214 </pre>
12215 2 If the currency symbol and sign string are adjacent, a space separates them;
12216 <pre>
12217 otherwise, a space separates the sign string from the value.
12218 </pre>
12219 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
12220 int_curr_symbol is used instead of a space.
12221 <p><!--para 6 -->
12222 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
12223 int_n_sign_posn are interpreted according to the following:
12224 0 Parentheses surround the quantity and currency symbol.
12225 1 The sign string precedes the quantity and currency symbol.
12226 2 The sign string succeeds the quantity and currency symbol.
12227 3 The sign string immediately precedes the currency symbol.
12228 4 The sign string immediately succeeds the currency symbol.
12229 <!--page 247 -->
12230 <p><!--para 7 -->
12231 The implementation shall behave as if no library function calls the localeconv
12232 function.
12233 <p><b>Returns</b>
12234 <p><!--para 8 -->
12235 The localeconv function returns a pointer to the filled-in object. The structure
12236 pointed to by the return value shall not be modified by the program, but may be
12237 overwritten by a subsequent call to the localeconv function. In addition, calls to the
12238 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
12239 overwrite the contents of the structure.
12240 <p><!--para 9 -->
12241 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
12242 monetary quantities.
12243 <pre>
12244 Local format International format
12245 </pre>
12247 Country Positive Negative Positive Negative
12249 Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
12250 Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
12251 Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
12252 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
12253 <p><!--para 10 -->
12254 For these four countries, the respective values for the monetary members of the structure returned by
12255 localeconv could be:
12256 <pre>
12257 Country1 Country2 Country3 Country4
12258 </pre>
12266 frac_digits 2 0 2 2
12267 p_cs_precedes 0 1 1 1
12268 n_cs_precedes 0 1 1 1
12269 p_sep_by_space 1 0 1 0
12270 n_sep_by_space 1 0 2 0
12271 p_sign_posn 1 1 1 1
12272 n_sign_posn 1 1 4 2
12274 int_frac_digits 2 0 2 2
12275 int_p_cs_precedes 1 1 1 1
12276 int_n_cs_precedes 1 1 1 1
12277 int_p_sep_by_space 1 1 1 1
12278 int_n_sep_by_space 2 1 2 1
12279 int_p_sign_posn 1 1 1 1
12280 int_n_sign_posn 4 1 4 2
12281 <!--page 248 -->
12282 <p><!--para 11 -->
12283 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
12284 affect the formatted value.
12285 <pre>
12286 p_sep_by_space
12287 </pre>
12289 p_cs_precedes p_sign_posn 0 1 2
12291 <pre>
12297 </pre>
12299 <!--page 249 -->
12300 <pre>
12306 </pre>
12310 <p><!--para 1 -->
12311 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
12312 several macros. Most synopses specify a family of functions consisting of a principal
12313 function with one or more double parameters, a double return value, or both; and
12314 other functions with the same name but with f and l suffixes, which are corresponding
12315 functions with float and long double parameters, return values, or both.<sup><a href="#note226"><b>226)</b></a></sup>
12316 Integer arithmetic functions and conversion functions are discussed later.
12317 <p><!--para 2 -->
12318 The types
12319 <pre>
12320 float_t
12321 double_t
12322 </pre>
12323 are floating types at least as wide as float and double, respectively, and such that
12324 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
12325 float_t and double_t are float and double, respectively; if
12326 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
12327 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
12329 <p><!--para 3 -->
12330 The macro
12331 <pre>
12332 HUGE_VAL
12333 </pre>
12334 expands to a positive double constant expression, not necessarily representable as a
12335 float. The macros
12336 <pre>
12337 HUGE_VALF
12338 HUGE_VALL
12339 </pre>
12340 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note228"><b>228)</b></a></sup>
12341 <p><!--para 4 -->
12342 The macro
12343 <pre>
12344 INFINITY
12345 </pre>
12346 expands to a constant expression of type float representing positive or unsigned
12347 infinity, if available; else to a positive constant of type float that overflows at
12351 <!--page 250 -->
12353 <p><!--para 5 -->
12354 The macro
12355 <pre>
12356 NAN
12357 </pre>
12358 is defined if and only if the implementation supports quiet NaNs for the float type. It
12359 expands to a constant expression of type float representing a quiet NaN.
12360 <p><!--para 6 -->
12361 The number classification macros
12362 <pre>
12363 FP_INFINITE
12364 FP_NAN
12365 FP_NORMAL
12366 FP_SUBNORMAL
12367 FP_ZERO
12368 </pre>
12369 represent the mutually exclusive kinds of floating-point values. They expand to integer
12370 constant expressions with distinct values. Additional implementation-defined floating-
12371 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
12372 may also be specified by the implementation.
12373 <p><!--para 7 -->
12374 The macro
12375 <pre>
12376 FP_FAST_FMA
12377 </pre>
12378 is optionally defined. If defined, it indicates that the fma function generally executes
12379 about as fast as, or faster than, a multiply and an add of double operands.<sup><a href="#note230"><b>230)</b></a></sup> The
12380 macros
12381 <pre>
12382 FP_FAST_FMAF
12383 FP_FAST_FMAL
12384 </pre>
12385 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
12386 these macros expand to the integer constant 1.
12387 <p><!--para 8 -->
12388 The macros
12389 <pre>
12390 FP_ILOGB0
12391 FP_ILOGBNAN
12392 </pre>
12393 expand to integer constant expressions whose values are returned by ilogb(x) if x is
12394 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
12395 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
12398 <!--page 251 -->
12399 <p><!--para 9 -->
12400 The macros
12401 <pre>
12402 MATH_ERRNO
12403 MATH_ERREXCEPT
12404 </pre>
12405 expand to the integer constants 1 and 2, respectively; the macro
12406 <pre>
12407 math_errhandling
12408 </pre>
12409 expands to an expression that has type int and the value MATH_ERRNO,
12410 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
12411 constant for the duration of the program. It is unspecified whether
12412 math_errhandling is a macro or an identifier with external linkage. If a macro
12413 definition is suppressed or a program defines an identifier with the name
12414 math_errhandling, the behavior is undefined. If the expression
12415 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
12416 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
12419 <p><b>Footnotes</b>
12420 <p><small><a name="note226" href="#note226">226)</a> Particularly on systems with wide expression evaluation, a <a href="#7.12"><math.h></a> function might pass arguments
12421 and return values in wider format than the synopsis prototype indicates.
12422 </small>
12423 <p><small><a name="note227" href="#note227">227)</a> The types float_t and double_t are intended to be the implementation's most efficient types at
12424 least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
12425 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
12426 </small>
12427 <p><small><a name="note228" href="#note228">228)</a> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
12428 supports infinities.
12429 </small>
12430 <p><small><a name="note229" href="#note229">229)</a> In this case, using INFINITY will violate the constraint in <a href="#6.4.4">6.4.4</a> and thus require a diagnostic.
12431 </small>
12432 <p><small><a name="note230" href="#note230">230)</a> Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
12433 directly with a hardware multiply-add instruction. Software implementations are expected to be
12434 substantially slower.
12435 </small>
12439 <p><!--para 1 -->
12440 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
12441 values of its input arguments, except where stated otherwise. Each function shall execute
12442 as if it were a single operation without raising SIGFPE and without generating any of the
12443 floating-point exceptions ''invalid'', ''divide-by-zero'', or ''overflow'' except to reflect
12444 the result of the function.
12445 <p><!--para 2 -->
12446 For all functions, a domain error occurs if an input argument is outside the domain over
12447 which the mathematical function is defined. The description of each function lists any
12448 required domain errors; an implementation may define additional domain errors, provided
12449 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note231"><b>231)</b></a></sup> On a
12450 domain error, the function returns an implementation-defined value; if the integer
12451 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
12452 errno acquires the value EDOM; if the integer expression math_errhandling &
12453 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
12454 <p><!--para 3 -->
12455 Similarly, a pole error (also known as a singularity or infinitary) occurs if the
12456 mathematical function has an exact infinite result as the finite input argument(s) are
12457 approached in the limit (for example, log(0.0)). The description of each function lists
12458 any required pole errors; an implementation may define additional pole errors, provided
12459 that such errors are consistent with the mathematical definition of the function. On a pole
12460 error, the function returns an implementation-defined value; if the integer expression
12463 <!--page 252 -->
12464 math_errhandling & MATH_ERRNO is nonzero, the integer expression errno
12465 acquires the value ERANGE; if the integer expression math_errhandling &
12466 MATH_ERREXCEPT is nonzero, the ''divide-by-zero'' floating-point exception is raised.
12467 <p><!--para 4 -->
12468 Likewise, a range error occurs if the mathematical result of the function cannot be
12469 represented in an object of the specified type, due to extreme magnitude.
12470 <p><!--para 5 -->
12471 A floating result overflows if the magnitude of the mathematical result is finite but so
12472 large that the mathematical result cannot be represented without extraordinary roundoff
12473 error in an object of the specified type. If a floating result overflows and default rounding
12474 is in effect, then the function returns the value of the macro HUGE_VAL, HUGE_VALF, or
12475 HUGE_VALL according to the return type, with the same sign as the correct value of the
12476 function; if the integer expression math_errhandling & MATH_ERRNO is nonzero,
12477 the integer expression errno acquires the value ERANGE; if the integer expression
12478 math_errhandling & MATH_ERREXCEPT is nonzero, the ''overflow'' floating-
12479 point exception is raised.
12480 <p><!--para 6 -->
12481 The result underflows if the magnitude of the mathematical result is so small that the
12482 mathematical result cannot be represented, without extraordinary roundoff error, in an
12483 object of the specified type.<sup><a href="#note232"><b>232)</b></a></sup> If the result underflows, the function returns an
12484 implementation-defined value whose magnitude is no greater than the smallest
12485 normalized positive number in the specified type; if the integer expression
12486 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
12487 value ERANGE is implementation-defined; if the integer expression
12488 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
12489 floating-point exception is raised is implementation-defined.
12490 <p><!--para 7 -->
12491 If a domain, pole, or range error occurs and the integer expression
12492 math_errhandling & MATH_ERRNO is zero,<sup><a href="#note233"><b>233)</b></a></sup> then errno shall either be set to
12493 the value corresponding to the error or left unmodified. If no such error occurs, errno
12494 shall be left unmodified regardless of the setting of math_errhandling.
12499 <!--page 253 -->
12501 <p><b>Footnotes</b>
12502 <p><small><a name="note231" href="#note231">231)</a> In an implementation that supports infinities, this allows an infinity as an argument to be a domain
12503 error if the mathematical domain of the function does not include the infinity.
12504 </small>
12505 <p><small><a name="note232" href="#note232">232)</a> The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
12506 also ''flush-to-zero'' underflow.
12507 </small>
12508 <p><small><a name="note233" href="#note233">233)</a> Math errors are being indicated by the floating-point exception flags rather than by errno.
12509 </small>
12513 <p><b>Synopsis</b>
12514 <p><!--para 1 -->
12515 <pre>
12517 #pragma STDC FP_CONTRACT on-off-switch
12518 </pre>
12519 <p><b>Description</b>
12520 <p><!--para 2 -->
12521 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
12522 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
12523 either outside external declarations or preceding all explicit declarations and statements
12524 inside a compound statement. When outside external declarations, the pragma takes
12525 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
12526 the end of the translation unit. When inside a compound statement, the pragma takes
12527 effect from its occurrence until another FP_CONTRACT pragma is encountered
12528 (including within a nested compound statement), or until the end of the compound
12529 statement; at the end of a compound statement the state for the pragma is restored to its
12530 condition just before the compound statement. If this pragma is used in any other
12531 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
12532 implementation-defined.
12536 <p><!--para 1 -->
12537 In the synopses in this subclause, real-floating indicates that the argument shall be an
12538 expression of real floating type.
12542 <p><b>Synopsis</b>
12543 <p><!--para 1 -->
12544 <pre>
12546 int fpclassify(real-floating x);
12547 </pre>
12548 <p><b>Description</b>
12549 <p><!--para 2 -->
12550 The fpclassify macro classifies its argument value as NaN, infinite, normal,
12551 subnormal, zero, or into another implementation-defined category. First, an argument
12552 represented in a format wider than its semantic type is converted to its semantic type.
12553 Then classification is based on the type of the argument.<sup><a href="#note234"><b>234)</b></a></sup>
12554 <p><b>Returns</b>
12555 <p><!--para 3 -->
12556 The fpclassify macro returns the value of the number classification macro
12557 appropriate to the value of its argument.
12560 <!--page 254 -->
12562 <p><b>Footnotes</b>
12563 <p><small><a name="note234" href="#note234">234)</a> Since an expression can be evaluated with more range and precision than its type has, it is important to
12564 know the type that classification is based on. For example, a normal long double value might
12565 become subnormal when converted to double, and zero when converted to float.
12566 </small>
12570 <p><b>Synopsis</b>
12571 <p><!--para 1 -->
12572 <pre>
12574 int isfinite(real-floating x);
12575 </pre>
12576 <p><b>Description</b>
12577 <p><!--para 2 -->
12578 The isfinite macro determines whether its argument has a finite value (zero,
12579 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
12580 format wider than its semantic type is converted to its semantic type. Then determination
12581 is based on the type of the argument.
12582 <p><b>Returns</b>
12583 <p><!--para 3 -->
12584 The isfinite macro returns a nonzero value if and only if its argument has a finite
12585 value.
12589 <p><b>Synopsis</b>
12590 <p><!--para 1 -->
12591 <pre>
12593 int isinf(real-floating x);
12594 </pre>
12595 <p><b>Description</b>
12596 <p><!--para 2 -->
12597 The isinf macro determines whether its argument value is an infinity (positive or
12598 negative). First, an argument represented in a format wider than its semantic type is
12599 converted to its semantic type. Then determination is based on the type of the argument.
12600 <p><b>Returns</b>
12601 <p><!--para 3 -->
12602 The isinf macro returns a nonzero value if and only if its argument has an infinite
12603 value.
12607 <p><b>Synopsis</b>
12608 <p><!--para 1 -->
12609 <pre>
12611 int isnan(real-floating x);
12612 </pre>
12613 <p><b>Description</b>
12614 <p><!--para 2 -->
12615 The isnan macro determines whether its argument value is a NaN. First, an argument
12616 represented in a format wider than its semantic type is converted to its semantic type.
12617 Then determination is based on the type of the argument.<sup><a href="#note235"><b>235)</b></a></sup>
12620 <!--page 255 -->
12621 <p><b>Returns</b>
12622 <p><!--para 3 -->
12623 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
12625 <p><b>Footnotes</b>
12626 <p><small><a name="note235" href="#note235">235)</a> For the isnan macro, the type for determination does not matter unless the implementation supports
12627 NaNs in the evaluation type but not in the semantic type.
12628 </small>
12632 <p><b>Synopsis</b>
12633 <p><!--para 1 -->
12634 <pre>
12636 int isnormal(real-floating x);
12637 </pre>
12638 <p><b>Description</b>
12639 <p><!--para 2 -->
12640 The isnormal macro determines whether its argument value is normal (neither zero,
12641 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
12642 semantic type is converted to its semantic type. Then determination is based on the type
12643 of the argument.
12644 <p><b>Returns</b>
12645 <p><!--para 3 -->
12646 The isnormal macro returns a nonzero value if and only if its argument has a normal
12647 value.
12651 <p><b>Synopsis</b>
12652 <p><!--para 1 -->
12653 <pre>
12655 int signbit(real-floating x);
12656 </pre>
12657 <p><b>Description</b>
12658 <p><!--para 2 -->
12659 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note236"><b>236)</b></a></sup>
12660 <p><b>Returns</b>
12661 <p><!--para 3 -->
12662 The signbit macro returns a nonzero value if and only if the sign of its argument value
12663 is negative.
12668 <!--page 256 -->
12670 <p><b>Footnotes</b>
12671 <p><small><a name="note236" href="#note236">236)</a> The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
12672 unsigned, it is treated as positive.
12673 </small>
12680 <p><b>Synopsis</b>
12681 <p><!--para 1 -->
12682 <pre>
12684 double acos(double x);
12685 float acosf(float x);
12686 long double acosl(long double x);
12687 </pre>
12688 <p><b>Description</b>
12689 <p><!--para 2 -->
12690 The acos functions compute the principal value of the arc cosine of x. A domain error
12691 occurs for arguments not in the interval [-1, +1].
12692 <p><b>Returns</b>
12693 <p><!--para 3 -->
12694 The acos functions return arccos x in the interval [0, pi ] radians.
12698 <p><b>Synopsis</b>
12699 <p><!--para 1 -->
12700 <pre>
12702 double asin(double x);
12703 float asinf(float x);
12704 long double asinl(long double x);
12705 </pre>
12706 <p><b>Description</b>
12707 <p><!--para 2 -->
12708 The asin functions compute the principal value of the arc sine of x. A domain error
12709 occurs for arguments not in the interval [-1, +1].
12710 <p><b>Returns</b>
12711 <p><!--para 3 -->
12712 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
12716 <p><b>Synopsis</b>
12717 <p><!--para 1 -->
12718 <pre>
12720 double atan(double x);
12721 float atanf(float x);
12722 long double atanl(long double x);
12723 </pre>
12724 <p><b>Description</b>
12725 <p><!--para 2 -->
12726 The atan functions compute the principal value of the arc tangent of x.
12727 <!--page 257 -->
12728 <p><b>Returns</b>
12729 <p><!--para 3 -->
12730 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
12734 <p><b>Synopsis</b>
12735 <p><!--para 1 -->
12736 <pre>
12738 double atan2(double y, double x);
12739 float atan2f(float y, float x);
12740 long double atan2l(long double y, long double x);
12741 </pre>
12742 <p><b>Description</b>
12743 <p><!--para 2 -->
12744 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
12745 arguments to determine the quadrant of the return value. A domain error may occur if
12746 both arguments are zero.
12747 <p><b>Returns</b>
12748 <p><!--para 3 -->
12749 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
12753 <p><b>Synopsis</b>
12754 <p><!--para 1 -->
12755 <pre>
12757 double cos(double x);
12758 float cosf(float x);
12759 long double cosl(long double x);
12760 </pre>
12761 <p><b>Description</b>
12762 <p><!--para 2 -->
12763 The cos functions compute the cosine of x (measured in radians).
12764 <p><b>Returns</b>
12765 <p><!--para 3 -->
12766 The cos functions return cos x.
12770 <p><b>Synopsis</b>
12771 <p><!--para 1 -->
12772 <pre>
12774 double sin(double x);
12775 float sinf(float x);
12776 long double sinl(long double x);
12777 </pre>
12778 <p><b>Description</b>
12779 <p><!--para 2 -->
12780 The sin functions compute the sine of x (measured in radians).
12781 <!--page 258 -->
12782 <p><b>Returns</b>
12783 <p><!--para 3 -->
12784 The sin functions return sin x.
12788 <p><b>Synopsis</b>
12789 <p><!--para 1 -->
12790 <pre>
12792 double tan(double x);
12793 float tanf(float x);
12794 long double tanl(long double x);
12795 </pre>
12796 <p><b>Description</b>
12797 <p><!--para 2 -->
12798 The tan functions return the tangent of x (measured in radians).
12799 <p><b>Returns</b>
12800 <p><!--para 3 -->
12801 The tan functions return tan x.
12808 <p><b>Synopsis</b>
12809 <p><!--para 1 -->
12810 <pre>
12812 double acosh(double x);
12813 float acoshf(float x);
12814 long double acoshl(long double x);
12815 </pre>
12816 <p><b>Description</b>
12817 <p><!--para 2 -->
12818 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
12819 error occurs for arguments less than 1.
12820 <p><b>Returns</b>
12821 <p><!--para 3 -->
12822 The acosh functions return arcosh x in the interval [0, +(inf)].
12826 <p><b>Synopsis</b>
12827 <p><!--para 1 -->
12828 <pre>
12830 double asinh(double x);
12831 float asinhf(float x);
12832 long double asinhl(long double x);
12833 </pre>
12834 <p><b>Description</b>
12835 <p><!--para 2 -->
12836 The asinh functions compute the arc hyperbolic sine of x.
12837 <!--page 259 -->
12838 <p><b>Returns</b>
12839 <p><!--para 3 -->
12840 The asinh functions return arsinh x.
12844 <p><b>Synopsis</b>
12845 <p><!--para 1 -->
12846 <pre>
12848 double atanh(double x);
12849 float atanhf(float x);
12850 long double atanhl(long double x);
12851 </pre>
12852 <p><b>Description</b>
12853 <p><!--para 2 -->
12854 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
12855 for arguments not in the interval [-1, +1]. A pole error may occur if the argument equals
12856 -1 or +1.
12857 <p><b>Returns</b>
12858 <p><!--para 3 -->
12859 The atanh functions return artanh x.
12863 <p><b>Synopsis</b>
12864 <p><!--para 1 -->
12865 <pre>
12867 double cosh(double x);
12868 float coshf(float x);
12869 long double coshl(long double x);
12870 </pre>
12871 <p><b>Description</b>
12872 <p><!--para 2 -->
12873 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
12874 magnitude of x is too large.
12875 <p><b>Returns</b>
12876 <p><!--para 3 -->
12877 The cosh functions return cosh x.
12881 <p><b>Synopsis</b>
12882 <p><!--para 1 -->
12883 <pre>
12885 double sinh(double x);
12886 float sinhf(float x);
12887 long double sinhl(long double x);
12888 </pre>
12889 <p><b>Description</b>
12890 <p><!--para 2 -->
12891 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
12892 magnitude of x is too large.
12893 <!--page 260 -->
12894 <p><b>Returns</b>
12895 <p><!--para 3 -->
12896 The sinh functions return sinh x.
12900 <p><b>Synopsis</b>
12901 <p><!--para 1 -->
12902 <pre>
12904 double tanh(double x);
12905 float tanhf(float x);
12906 long double tanhl(long double x);
12907 </pre>
12908 <p><b>Description</b>
12909 <p><!--para 2 -->
12910 The tanh functions compute the hyperbolic tangent of x.
12911 <p><b>Returns</b>
12912 <p><!--para 3 -->
12913 The tanh functions return tanh x.
12920 <p><b>Synopsis</b>
12921 <p><!--para 1 -->
12922 <pre>
12924 double exp(double x);
12925 float expf(float x);
12926 long double expl(long double x);
12927 </pre>
12928 <p><b>Description</b>
12929 <p><!--para 2 -->
12930 The exp functions compute the base-e exponential of x. A range error occurs if the
12931 magnitude of x is too large.
12932 <p><b>Returns</b>
12933 <p><!--para 3 -->
12934 The exp functions return ex .
12938 <p><b>Synopsis</b>
12939 <p><!--para 1 -->
12940 <pre>
12942 double exp2(double x);
12943 float exp2f(float x);
12944 long double exp2l(long double x);
12945 </pre>
12946 <p><b>Description</b>
12947 <p><!--para 2 -->
12948 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
12949 magnitude of x is too large.
12950 <!--page 261 -->
12951 <p><b>Returns</b>
12952 <p><!--para 3 -->
12953 The exp2 functions return 2x .
12957 <p><b>Synopsis</b>
12958 <p><!--para 1 -->
12959 <pre>
12961 double expm1(double x);
12962 float expm1f(float x);
12963 long double expm1l(long double x);
12964 </pre>
12965 <p><b>Description</b>
12966 <p><!--para 2 -->
12967 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
12969 <p><b>Returns</b>
12970 <p><!--para 3 -->
12971 The expm1 functions return ex - 1.
12973 <p><b>Footnotes</b>
12974 <p><small><a name="note237" href="#note237">237)</a> For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
12975 </small>
12979 <p><b>Synopsis</b>
12980 <p><!--para 1 -->
12981 <pre>
12983 double frexp(double value, int *exp);
12984 float frexpf(float value, int *exp);
12985 long double frexpl(long double value, int *exp);
12986 </pre>
12987 <p><b>Description</b>
12988 <p><!--para 2 -->
12989 The frexp functions break a floating-point number into a normalized fraction and an
12990 integral power of 2. They store the integer in the int object pointed to by exp.
12991 <p><b>Returns</b>
12992 <p><!--para 3 -->
12993 If value is not a floating-point number or if the integral power of 2 is outside the range
12994 of int, the results are unspecified. Otherwise, the frexp functions return the value x,
12995 such that x has a magnitude in the interval [1/2, 1) or zero, and value equals x x 2*exp .
12996 If value is zero, both parts of the result are zero.
13001 <!--page 262 -->
13005 <p><b>Synopsis</b>
13006 <p><!--para 1 -->
13007 <pre>
13009 int ilogb(double x);
13010 int ilogbf(float x);
13011 int ilogbl(long double x);
13012 </pre>
13013 <p><b>Description</b>
13014 <p><!--para 2 -->
13015 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
13016 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
13017 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
13018 the corresponding logb function and casting the returned value to type int. A domain
13019 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
13020 the range of the return type, the numeric result is unspecified.
13021 <p><b>Returns</b>
13022 <p><!--para 3 -->
13023 The ilogb functions return the exponent of x as a signed int value.
13028 <p><b>Synopsis</b>
13029 <p><!--para 1 -->
13030 <pre>
13032 double ldexp(double x, int exp);
13033 float ldexpf(float x, int exp);
13034 long double ldexpl(long double x, int exp);
13035 </pre>
13036 <p><b>Description</b>
13037 <p><!--para 2 -->
13038 The ldexp functions multiply a floating-point number by an integral power of 2. A
13039 range error may occur.
13040 <p><b>Returns</b>
13041 <p><!--para 3 -->
13042 The ldexp functions return x x 2exp .
13046 <p><b>Synopsis</b>
13047 <p><!--para 1 -->
13048 <!--page 263 -->
13049 <pre>
13051 double log(double x);
13052 float logf(float x);
13053 long double logl(long double x);
13054 </pre>
13055 <p><b>Description</b>
13056 <p><!--para 2 -->
13057 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
13058 the argument is negative. A pole error may occur if the argument is zero.
13059 <p><b>Returns</b>
13060 <p><!--para 3 -->
13061 The log functions return loge x.
13065 <p><b>Synopsis</b>
13066 <p><!--para 1 -->
13067 <pre>
13069 double log10(double x);
13070 float log10f(float x);
13071 long double log10l(long double x);
13072 </pre>
13073 <p><b>Description</b>
13074 <p><!--para 2 -->
13075 The log10 functions compute the base-10 (common) logarithm of x. A domain error
13076 occurs if the argument is negative. A pole error may occur if the argument is zero.
13077 <p><b>Returns</b>
13078 <p><!--para 3 -->
13079 The log10 functions return log10 x.
13083 <p><b>Synopsis</b>
13084 <p><!--para 1 -->
13085 <pre>
13087 double log1p(double x);
13088 float log1pf(float x);
13089 long double log1pl(long double x);
13090 </pre>
13091 <p><b>Description</b>
13092 <p><!--para 2 -->
13093 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note238"><b>238)</b></a></sup>
13094 A domain error occurs if the argument is less than -1. A pole error may occur if the
13095 argument equals -1.
13096 <p><b>Returns</b>
13097 <p><!--para 3 -->
13098 The log1p functions return loge (1 + x).
13103 <!--page 264 -->
13105 <p><b>Footnotes</b>
13106 <p><small><a name="note238" href="#note238">238)</a> For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
13107 </small>
13111 <p><b>Synopsis</b>
13112 <p><!--para 1 -->
13113 <pre>
13115 double log2(double x);
13116 float log2f(float x);
13117 long double log2l(long double x);
13118 </pre>
13119 <p><b>Description</b>
13120 <p><!--para 2 -->
13121 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
13122 argument is less than zero. A pole error may occur if the argument is zero.
13123 <p><b>Returns</b>
13124 <p><!--para 3 -->
13125 The log2 functions return log2 x.
13129 <p><b>Synopsis</b>
13130 <p><!--para 1 -->
13131 <pre>
13133 double logb(double x);
13134 float logbf(float x);
13135 long double logbl(long double x);
13136 </pre>
13137 <p><b>Description</b>
13138 <p><!--para 2 -->
13139 The logb functions extract the exponent of x, as a signed integer value in floating-point
13140 format. If x is subnormal it is treated as though it were normalized; thus, for positive
13141 finite x,
13142 <pre>
13143 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX
13144 </pre>
13145 A domain error or pole error may occur if the argument is zero.
13146 <p><b>Returns</b>
13147 <p><!--para 3 -->
13148 The logb functions return the signed exponent of x.
13152 <p><b>Synopsis</b>
13153 <p><!--para 1 -->
13154 <pre>
13156 double modf(double value, double *iptr);
13157 float modff(float value, float *iptr);
13158 long double modfl(long double value, long double *iptr);
13159 </pre>
13160 <p><b>Description</b>
13161 <p><!--para 2 -->
13162 The modf functions break the argument value into integral and fractional parts, each of
13163 which has the same type and sign as the argument. They store the integral part (in
13164 <!--page 265 -->
13165 floating-point format) in the object pointed to by iptr.
13166 <p><b>Returns</b>
13167 <p><!--para 3 -->
13168 The modf functions return the signed fractional part of value.
13172 <p><b>Synopsis</b>
13173 <p><!--para 1 -->
13174 <pre>
13176 double scalbn(double x, int n);
13177 float scalbnf(float x, int n);
13178 long double scalbnl(long double x, int n);
13179 double scalbln(double x, long int n);
13180 float scalblnf(float x, long int n);
13181 long double scalblnl(long double x, long int n);
13182 </pre>
13183 <p><b>Description</b>
13184 <p><!--para 2 -->
13185 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
13186 normally by computing FLT_RADIXn explicitly. A range error may occur.
13187 <p><b>Returns</b>
13188 <p><!--para 3 -->
13189 The scalbn and scalbln functions return x x FLT_RADIXn .
13196 <p><b>Synopsis</b>
13197 <p><!--para 1 -->
13198 <pre>
13200 double cbrt(double x);
13201 float cbrtf(float x);
13202 long double cbrtl(long double x);
13203 </pre>
13204 <p><b>Description</b>
13205 <p><!--para 2 -->
13206 The cbrt functions compute the real cube root of x.
13207 <p><b>Returns</b>
13208 <p><!--para 3 -->
13209 The cbrt functions return x1/3 .
13210 <!--page 266 -->
13214 <p><b>Synopsis</b>
13215 <p><!--para 1 -->
13216 <pre>
13218 double fabs(double x);
13219 float fabsf(float x);
13220 long double fabsl(long double x);
13221 </pre>
13222 <p><b>Description</b>
13223 <p><!--para 2 -->
13224 The fabs functions compute the absolute value of a floating-point number x.
13225 <p><b>Returns</b>
13226 <p><!--para 3 -->
13227 The fabs functions return | x |.
13231 <p><b>Synopsis</b>
13232 <p><!--para 1 -->
13233 <pre>
13235 double hypot(double x, double y);
13236 float hypotf(float x, float y);
13237 long double hypotl(long double x, long double y);
13238 </pre>
13239 <p><b>Description</b>
13240 <p><!--para 2 -->
13241 The hypot functions compute the square root of the sum of the squares of x and y,
13242 without undue overflow or underflow. A range error may occur.
13243 <p><!--para 3 -->
13244 <p><b>Returns</b>
13245 <p><!--para 4 -->
13246 The hypot functions return (sqrt)x2 + y2 .
13247 <pre>
13248 -
13249 -----
13250 </pre>
13254 <p><b>Synopsis</b>
13255 <p><!--para 1 -->
13256 <pre>
13258 double pow(double x, double y);
13259 float powf(float x, float y);
13260 long double powl(long double x, long double y);
13261 </pre>
13262 <p><b>Description</b>
13263 <p><!--para 2 -->
13264 The pow functions compute x raised to the power y. A domain error occurs if x is finite
13265 and negative and y is finite and not an integer value. A range error may occur. A domain
13266 error may occur if x is zero and y is zero. A domain error or pole error may occur if x is
13267 zero and y is less than zero.
13268 <!--page 267 -->
13269 <p><b>Returns</b>
13270 <p><!--para 3 -->
13271 The pow functions return xy .
13275 <p><b>Synopsis</b>
13276 <p><!--para 1 -->
13277 <pre>
13279 double sqrt(double x);
13280 float sqrtf(float x);
13281 long double sqrtl(long double x);
13282 </pre>
13283 <p><b>Description</b>
13284 <p><!--para 2 -->
13285 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
13286 the argument is less than zero.
13287 <p><b>Returns</b>
13288 <p><!--para 3 -->
13289 The sqrt functions return (sqrt)x.
13290 <pre>
13291 -
13292 -
13293 </pre>
13300 <p><b>Synopsis</b>
13301 <p><!--para 1 -->
13302 <pre>
13304 double erf(double x);
13305 float erff(float x);
13306 long double erfl(long double x);
13307 </pre>
13308 <p><b>Description</b>
13309 <p><!--para 2 -->
13310 The erf functions compute the error function of x.
13311 <p><b>Returns</b>
13312 <p><!--para 3 -->
13313 <pre>
13314 2 x
13315 (integral) e-t dt.
13316 2
13317 </pre>
13318 The erf functions return erf x =
13319 <pre>
13320 (sqrt)pi
13321 -
13322 - 0
13323 </pre>
13328 <p><b>Synopsis</b>
13329 <p><!--para 1 -->
13330 <pre>
13332 double erfc(double x);
13333 float erfcf(float x);
13334 long double erfcl(long double x);
13335 </pre>
13336 <p><b>Description</b>
13337 <p><!--para 2 -->
13338 The erfc functions compute the complementary error function of x. A range error
13339 occurs if x is too large.
13340 <!--page 268 -->
13341 <p><b>Returns</b>
13342 <p><!--para 3 -->
13343 <pre>
13344 2 (inf)
13345 (integral) e-t dt.
13346 2
13347 </pre>
13348 The erfc functions return erfc x = 1 - erf x =
13349 <pre>
13350 (sqrt)pi
13351 -
13352 - x
13353 </pre>
13358 <p><b>Synopsis</b>
13359 <p><!--para 1 -->
13360 <pre>
13362 double lgamma(double x);
13363 float lgammaf(float x);
13364 long double lgammal(long double x);
13365 </pre>
13366 <p><b>Description</b>
13367 <p><!--para 2 -->
13368 The lgamma functions compute the natural logarithm of the absolute value of gamma of
13369 x. A range error occurs if x is too large. A pole error may occur if x is a negative integer
13370 or zero.
13371 <p><b>Returns</b>
13372 <p><!--para 3 -->
13373 The lgamma functions return loge | (Gamma)(x) |.
13377 <p><b>Synopsis</b>
13378 <p><!--para 1 -->
13379 <pre>
13381 double tgamma(double x);
13382 float tgammaf(float x);
13383 long double tgammal(long double x);
13384 </pre>
13385 <p><b>Description</b>
13386 <p><!--para 2 -->
13387 The tgamma functions compute the gamma function of x. A domain error or pole error
13388 may occur if x is a negative integer or zero. A range error occurs if the magnitude of x is
13389 too large and may occur if the magnitude of x is too small.
13390 <p><b>Returns</b>
13391 <p><!--para 3 -->
13392 The tgamma functions return (Gamma)(x).
13393 <!--page 269 -->
13400 <p><b>Synopsis</b>
13401 <p><!--para 1 -->
13402 <pre>
13404 double ceil(double x);
13405 float ceilf(float x);
13406 long double ceill(long double x);
13407 </pre>
13408 <p><b>Description</b>
13409 <p><!--para 2 -->
13410 The ceil functions compute the smallest integer value not less than x.
13411 <p><b>Returns</b>
13412 <p><!--para 3 -->
13413 The ceil functions return [^x^], expressed as a floating-point number.
13417 <p><b>Synopsis</b>
13418 <p><!--para 1 -->
13419 <pre>
13421 double floor(double x);
13422 float floorf(float x);
13423 long double floorl(long double x);
13424 </pre>
13425 <p><b>Description</b>
13426 <p><!--para 2 -->
13427 The floor functions compute the largest integer value not greater than x.
13428 <p><b>Returns</b>
13429 <p><!--para 3 -->
13430 The floor functions return [_x_], expressed as a floating-point number.
13434 <p><b>Synopsis</b>
13435 <p><!--para 1 -->
13436 <pre>
13438 double nearbyint(double x);
13439 float nearbyintf(float x);
13440 long double nearbyintl(long double x);
13441 </pre>
13442 <p><b>Description</b>
13443 <p><!--para 2 -->
13444 The nearbyint functions round their argument to an integer value in floating-point
13445 format, using the current rounding direction and without raising the ''inexact'' floating-
13446 point exception.
13447 <!--page 270 -->
13448 <p><b>Returns</b>
13449 <p><!--para 3 -->
13450 The nearbyint functions return the rounded integer value.
13454 <p><b>Synopsis</b>
13455 <p><!--para 1 -->
13456 <pre>
13458 double rint(double x);
13459 float rintf(float x);
13460 long double rintl(long double x);
13461 </pre>
13462 <p><b>Description</b>
13463 <p><!--para 2 -->
13464 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
13465 rint functions may raise the ''inexact'' floating-point exception if the result differs in
13466 value from the argument.
13467 <p><b>Returns</b>
13468 <p><!--para 3 -->
13469 The rint functions return the rounded integer value.
13473 <p><b>Synopsis</b>
13474 <p><!--para 1 -->
13475 <pre>
13477 long int lrint(double x);
13478 long int lrintf(float x);
13479 long int lrintl(long double x);
13480 long long int llrint(double x);
13481 long long int llrintf(float x);
13482 long long int llrintl(long double x);
13483 </pre>
13484 <p><b>Description</b>
13485 <p><!--para 2 -->
13486 The lrint and llrint functions round their argument to the nearest integer value,
13487 rounding according to the current rounding direction. If the rounded value is outside the
13488 range of the return type, the numeric result is unspecified and a domain error or range
13489 error may occur.
13490 <p><b>Returns</b>
13491 <p><!--para 3 -->
13492 The lrint and llrint functions return the rounded integer value.
13493 <!--page 271 -->
13497 <p><b>Synopsis</b>
13498 <p><!--para 1 -->
13499 <pre>
13501 double round(double x);
13502 float roundf(float x);
13503 long double roundl(long double x);
13504 </pre>
13505 <p><b>Description</b>
13506 <p><!--para 2 -->
13507 The round functions round their argument to the nearest integer value in floating-point
13508 format, rounding halfway cases away from zero, regardless of the current rounding
13509 direction.
13510 <p><b>Returns</b>
13511 <p><!--para 3 -->
13512 The round functions return the rounded integer value.
13516 <p><b>Synopsis</b>
13517 <p><!--para 1 -->
13518 <pre>
13520 long int lround(double x);
13521 long int lroundf(float x);
13522 long int lroundl(long double x);
13523 long long int llround(double x);
13524 long long int llroundf(float x);
13525 long long int llroundl(long double x);
13526 </pre>
13527 <p><b>Description</b>
13528 <p><!--para 2 -->
13529 The lround and llround functions round their argument to the nearest integer value,
13530 rounding halfway cases away from zero, regardless of the current rounding direction. If
13531 the rounded value is outside the range of the return type, the numeric result is unspecified
13532 and a domain error or range error may occur.
13533 <p><b>Returns</b>
13534 <p><!--para 3 -->
13535 The lround and llround functions return the rounded integer value.
13539 <p><b>Synopsis</b>
13540 <p><!--para 1 -->
13541 <!--page 272 -->
13542 <pre>
13544 double trunc(double x);
13545 float truncf(float x);
13546 long double truncl(long double x);
13547 </pre>
13548 <p><b>Description</b>
13549 <p><!--para 2 -->
13550 The trunc functions round their argument to the integer value, in floating format,
13551 nearest to but no larger in magnitude than the argument.
13552 <p><b>Returns</b>
13553 <p><!--para 3 -->
13554 The trunc functions return the truncated integer value.
13561 <p><b>Synopsis</b>
13562 <p><!--para 1 -->
13563 <pre>
13565 double fmod(double x, double y);
13566 float fmodf(float x, float y);
13567 long double fmodl(long double x, long double y);
13568 </pre>
13569 <p><b>Description</b>
13570 <p><!--para 2 -->
13571 The fmod functions compute the floating-point remainder of x/y.
13572 <p><b>Returns</b>
13573 <p><!--para 3 -->
13574 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
13575 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
13576 whether a domain error occurs or the fmod functions return zero is implementation-
13577 defined.
13581 <p><b>Synopsis</b>
13582 <p><!--para 1 -->
13583 <pre>
13585 double remainder(double x, double y);
13586 float remainderf(float x, float y);
13587 long double remainderl(long double x, long double y);
13588 </pre>
13589 <p><b>Description</b>
13590 <p><!--para 2 -->
13591 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note239"><b>239)</b></a></sup>
13596 <!--page 273 -->
13597 <p><b>Returns</b>
13598 <p><!--para 3 -->
13599 The remainder functions return x REM y. If y is zero, whether a domain error occurs
13600 or the functions return zero is implementation defined.
13602 <p><b>Footnotes</b>
13603 <p><small><a name="note239" href="#note239">239)</a> ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
13604 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
13605 | n - x/y | = 1/2, then n is even. If r = 0, its sign shall be that of x.'' This definition is applicable for
13606 all implementations.
13607 </small>
13611 <p><b>Synopsis</b>
13612 <p><!--para 1 -->
13613 <pre>
13615 double remquo(double x, double y, int *quo);
13616 float remquof(float x, float y, int *quo);
13617 long double remquol(long double x, long double y,
13618 int *quo);
13619 </pre>
13620 <p><b>Description</b>
13621 <p><!--para 2 -->
13622 The remquo functions compute the same remainder as the remainder functions. In
13623 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
13624 magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
13625 n is an implementation-defined integer greater than or equal to 3.
13626 <p><b>Returns</b>
13627 <p><!--para 3 -->
13628 The remquo functions return x REM y. If y is zero, the value stored in the object
13629 pointed to by quo is unspecified and whether a domain error occurs or the functions
13630 return zero is implementation defined.
13637 <p><b>Synopsis</b>
13638 <p><!--para 1 -->
13639 <pre>
13641 double copysign(double x, double y);
13642 float copysignf(float x, float y);
13643 long double copysignl(long double x, long double y);
13644 </pre>
13645 <p><b>Description</b>
13646 <p><!--para 2 -->
13647 The copysign functions produce a value with the magnitude of x and the sign of y.
13648 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
13649 represent a signed zero but do not treat negative zero consistently in arithmetic
13650 operations, the copysign functions regard the sign of zero as positive.
13651 <p><b>Returns</b>
13652 <p><!--para 3 -->
13653 The copysign functions return a value with the magnitude of x and the sign of y.
13654 <!--page 274 -->
13658 <p><b>Synopsis</b>
13659 <p><!--para 1 -->
13660 <pre>
13662 double nan(const char *tagp);
13663 float nanf(const char *tagp);
13664 long double nanl(const char *tagp);
13665 </pre>
13666 <p><b>Description</b>
13667 <p><!--para 2 -->
13672 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
13673 and strtold.
13674 <p><b>Returns</b>
13675 <p><!--para 3 -->
13676 The nan functions return a quiet NaN, if available, with content indicated through tagp.
13677 If the implementation does not support quiet NaNs, the functions return zero.
13678 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
13682 <p><b>Synopsis</b>
13683 <p><!--para 1 -->
13684 <pre>
13686 double nextafter(double x, double y);
13687 float nextafterf(float x, float y);
13688 long double nextafterl(long double x, long double y);
13689 </pre>
13690 <p><b>Description</b>
13691 <p><!--para 2 -->
13692 The nextafter functions determine the next representable value, in the type of the
13693 function, after x in the direction of y, where x and y are first converted to the type of the
13694 function.<sup><a href="#note240"><b>240)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
13695 if the magnitude of x is the largest finite value representable in the type and the result is
13696 infinite or not representable in the type.
13697 <p><b>Returns</b>
13698 <p><!--para 3 -->
13699 The nextafter functions return the next representable value in the specified format
13700 after x in the direction of y.
13703 <!--page 275 -->
13705 <p><b>Footnotes</b>
13706 <p><small><a name="note240" href="#note240">240)</a> The argument values are converted to the type of the function, even by a macro implementation of the
13707 function.
13708 </small>
13712 <p><b>Synopsis</b>
13713 <p><!--para 1 -->
13714 <pre>
13716 double nexttoward(double x, long double y);
13717 float nexttowardf(float x, long double y);
13718 long double nexttowardl(long double x, long double y);
13719 </pre>
13720 <p><b>Description</b>
13721 <p><!--para 2 -->
13722 The nexttoward functions are equivalent to the nextafter functions except that the
13723 second parameter has type long double and the functions return y converted to the
13726 <p><b>Footnotes</b>
13727 <p><small><a name="note241" href="#note241">241)</a> The result of the nexttoward functions is determined in the type of the function, without loss of
13728 range or precision in a floating second argument.
13729 </small>
13732 <h4><a name="7.12.12" href="#7.12.12">7.12.12 Maximum, minimum, and positive difference functions</a></h4>
13736 <p><b>Synopsis</b>
13737 <p><!--para 1 -->
13738 <pre>
13740 double fdim(double x, double y);
13741 float fdimf(float x, float y);
13742 long double fdiml(long double x, long double y);
13743 </pre>
13744 <p><b>Description</b>
13745 <p><!--para 2 -->
13746 The fdim functions determine the positive difference between their arguments:
13747 <pre>
13748 {x - y if x > y
13749 {
13750 {+0 if x <= y
13751 </pre>
13752 A range error may occur.
13753 <p><b>Returns</b>
13754 <p><!--para 3 -->
13755 The fdim functions return the positive difference value.
13759 <p><b>Synopsis</b>
13760 <p><!--para 1 -->
13761 <pre>
13763 double fmax(double x, double y);
13764 float fmaxf(float x, float y);
13765 long double fmaxl(long double x, long double y);
13766 </pre>
13770 <!--page 276 -->
13771 <p><b>Description</b>
13772 <p><!--para 2 -->
13773 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note242"><b>242)</b></a></sup>
13774 <p><b>Returns</b>
13775 <p><!--para 3 -->
13776 The fmax functions return the maximum numeric value of their arguments.
13778 <p><b>Footnotes</b>
13779 <p><small><a name="note242" href="#note242">242)</a> NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
13781 </small>
13785 <p><b>Synopsis</b>
13786 <p><!--para 1 -->
13787 <pre>
13789 double fmin(double x, double y);
13790 float fminf(float x, float y);
13791 long double fminl(long double x, long double y);
13792 </pre>
13793 <p><b>Description</b>
13794 <p><!--para 2 -->
13795 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note243"><b>243)</b></a></sup>
13796 <p><b>Returns</b>
13797 <p><!--para 3 -->
13798 The fmin functions return the minimum numeric value of their arguments.
13800 <p><b>Footnotes</b>
13801 <p><small><a name="note243" href="#note243">243)</a> The fmin functions are analogous to the fmax functions in their treatment of NaNs.
13802 </small>
13809 <p><b>Synopsis</b>
13810 <p><!--para 1 -->
13811 <pre>
13813 double fma(double x, double y, double z);
13814 float fmaf(float x, float y, float z);
13815 long double fmal(long double x, long double y,
13816 long double z);
13817 </pre>
13818 <p><b>Description</b>
13819 <p><!--para 2 -->
13820 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
13821 the value (as if) to infinite precision and round once to the result format, according to the
13822 current rounding mode. A range error may occur.
13823 <p><b>Returns</b>
13824 <p><!--para 3 -->
13825 The fma functions return (x x y) + z, rounded as one ternary operation.
13830 <!--page 277 -->
13834 <p><!--para 1 -->
13835 The relational and equality operators support the usual mathematical relationships
13836 between numeric values. For any ordered pair of numeric values exactly one of the
13837 relationships -- less, greater, and equal -- is true. Relational operators may raise the
13838 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
13839 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note244"><b>244)</b></a></sup> The following
13840 subclauses provide macros that are quiet (non floating-point exception raising) versions
13841 of the relational operators, and other comparison macros that facilitate writing efficient
13842 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
13843 the synopses in this subclause, real-floating indicates that the argument shall be an
13844 expression of real floating type<sup><a href="#note245"><b>245)</b></a></sup> (both arguments need not have the same type).<sup><a href="#note246"><b>246)</b></a></sup>
13846 <p><b>Footnotes</b>
13847 <p><small><a name="note244" href="#note244">244)</a> IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
13848 the operands compare unordered, as an error indicator for programs written without consideration of
13849 NaNs; the result in these cases is false.
13850 </small>
13851 <p><small><a name="note245" href="#note245">245)</a> If any argument is of integer type, or any other type that is not a real floating type, the behavior is
13852 undefined.
13853 </small>
13854 <p><small><a name="note246" href="#note246">246)</a> Whether an argument represented in a format wider than its semantic type is converted to the semantic
13855 type is unspecified.
13856 </small>
13860 <p><b>Synopsis</b>
13861 <p><!--para 1 -->
13862 <pre>
13864 int isgreater(real-floating x, real-floating y);
13865 </pre>
13866 <p><b>Description</b>
13867 <p><!--para 2 -->
13868 The isgreater macro determines whether its first argument is greater than its second
13869 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
13870 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
13871 exception when x and y are unordered.
13872 <p><b>Returns</b>
13873 <p><!--para 3 -->
13874 The isgreater macro returns the value of (x) > (y).
13878 <p><b>Synopsis</b>
13879 <p><!--para 1 -->
13880 <pre>
13882 int isgreaterequal(real-floating x, real-floating y);
13883 </pre>
13888 <!--page 278 -->
13889 <p><b>Description</b>
13890 <p><!--para 2 -->
13891 The isgreaterequal macro determines whether its first argument is greater than or
13892 equal to its second argument. The value of isgreaterequal(x, y) is always equal
13893 to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
13894 not raise the ''invalid'' floating-point exception when x and y are unordered.
13895 <p><b>Returns</b>
13896 <p><!--para 3 -->
13897 The isgreaterequal macro returns the value of (x) >= (y).
13901 <p><b>Synopsis</b>
13902 <p><!--para 1 -->
13903 <pre>
13905 int isless(real-floating x, real-floating y);
13906 </pre>
13907 <p><b>Description</b>
13908 <p><!--para 2 -->
13909 The isless macro determines whether its first argument is less than its second
13910 argument. The value of isless(x, y) is always equal to (x) < (y); however,
13911 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
13912 exception when x and y are unordered.
13913 <p><b>Returns</b>
13914 <p><!--para 3 -->
13915 The isless macro returns the value of (x) < (y).
13919 <p><b>Synopsis</b>
13920 <p><!--para 1 -->
13921 <pre>
13923 int islessequal(real-floating x, real-floating y);
13924 </pre>
13925 <p><b>Description</b>
13926 <p><!--para 2 -->
13927 The islessequal macro determines whether its first argument is less than or equal to
13928 its second argument. The value of islessequal(x, y) is always equal to
13929 (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
13930 the ''invalid'' floating-point exception when x and y are unordered.
13931 <p><b>Returns</b>
13932 <p><!--para 3 -->
13933 The islessequal macro returns the value of (x) <= (y).
13934 <!--page 279 -->
13938 <p><b>Synopsis</b>
13939 <p><!--para 1 -->
13940 <pre>
13942 int islessgreater(real-floating x, real-floating y);
13943 </pre>
13944 <p><b>Description</b>
13945 <p><!--para 2 -->
13946 The islessgreater macro determines whether its first argument is less than or
13947 greater than its second argument. The islessgreater(x, y) macro is similar to
13948 (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
13949 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
13950 and y twice).
13951 <p><b>Returns</b>
13952 <p><!--para 3 -->
13953 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
13957 <p><b>Synopsis</b>
13958 <p><!--para 1 -->
13959 <pre>
13961 int isunordered(real-floating x, real-floating y);
13962 </pre>
13963 <p><b>Description</b>
13964 <p><!--para 2 -->
13965 The isunordered macro determines whether its arguments are unordered.
13966 <p><b>Returns</b>
13967 <p><!--para 3 -->
13968 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
13969 <!--page 280 -->
13973 <p><!--para 1 -->
13974 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
13975 one type, for bypassing the normal function call and return discipline.<sup><a href="#note247"><b>247)</b></a></sup>
13976 <p><!--para 2 -->
13977 The type declared is
13978 <pre>
13979 jmp_buf
13980 </pre>
13981 which is an array type suitable for holding the information needed to restore a calling
13982 environment. The environment of a call to the setjmp macro consists of information
13983 sufficient for a call to the longjmp function to return execution to the correct block and
13984 invocation of that block, were it called recursively. It does not include the state of the
13985 floating-point status flags, of open files, or of any other component of the abstract
13986 machine.
13987 <p><!--para 3 -->
13988 It is unspecified whether setjmp is a macro or an identifier declared with external
13989 linkage. If a macro definition is suppressed in order to access an actual function, or a
13990 program defines an external identifier with the name setjmp, the behavior is undefined.
13992 <p><b>Footnotes</b>
13993 <p><small><a name="note247" href="#note247">247)</a> These functions are useful for dealing with unusual conditions encountered in a low-level function of
13994 a program.
13995 </small>
14002 <p><b>Synopsis</b>
14003 <p><!--para 1 -->
14004 <pre>
14006 int setjmp(jmp_buf env);
14007 </pre>
14008 <p><b>Description</b>
14009 <p><!--para 2 -->
14010 The setjmp macro saves its calling environment in its jmp_buf argument for later use
14011 by the longjmp function.
14012 <p><b>Returns</b>
14013 <p><!--para 3 -->
14014 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
14015 return is from a call to the longjmp function, the setjmp macro returns a nonzero
14016 value.
14017 <p><b>Environmental limits</b>
14018 <p><!--para 4 -->
14019 An invocation of the setjmp macro shall appear only in one of the following contexts:
14020 <ul>
14021 <li> the entire controlling expression of a selection or iteration statement;
14022 <li> one operand of a relational or equality operator with the other operand an integer
14023 constant expression, with the resulting expression being the entire controlling
14026 <!--page 281 -->
14027 expression of a selection or iteration statement;
14028 <li> the operand of a unary ! operator with the resulting expression being the entire
14029 controlling expression of a selection or iteration statement; or
14030 <li> the entire expression of an expression statement (possibly cast to void).
14031 </ul>
14032 <p><!--para 5 -->
14033 If the invocation appears in any other context, the behavior is undefined.
14040 <p><b>Synopsis</b>
14041 <p><!--para 1 -->
14042 <pre>
14044 _Noreturn void longjmp(jmp_buf env, int val);
14045 </pre>
14046 <p><b>Description</b>
14047 <p><!--para 2 -->
14048 The longjmp function restores the environment saved by the most recent invocation of
14049 the setjmp macro in the same invocation of the program with the corresponding
14050 jmp_buf argument. If there has been no such invocation, or if the invocation was from
14051 another thread of execution, or if the function containing the invocation of the setjmp
14052 macro has terminated execution<sup><a href="#note248"><b>248)</b></a></sup> in the interim, or if the invocation of the setjmp
14053 macro was within the scope of an identifier with variably modified type and execution has
14054 left that scope in the interim, the behavior is undefined.
14055 <p><!--para 3 -->
14056 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note249"><b>249)</b></a></sup>
14057 have state, as of the time the longjmp function was called, except that the values of
14058 objects of automatic storage duration that are local to the function containing the
14059 invocation of the corresponding setjmp macro that do not have volatile-qualified type
14060 and have been changed between the setjmp invocation and longjmp call are
14061 indeterminate.
14062 <p><b>Returns</b>
14063 <p><!--para 4 -->
14064 After longjmp is completed, thread execution continues as if the corresponding
14065 invocation of the setjmp macro had just returned the value specified by val. The
14066 longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
14067 the setjmp macro returns the value 1.
14068 <p><!--para 5 -->
14069 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
14070 might cause memory associated with a variable length array object to be squandered.
14074 <!--page 282 -->
14075 <!--page 283 -->
14076 <pre>
14078 jmp_buf buf;
14079 void g(int n);
14080 void h(int n);
14081 int n = 6;
14082 void f(void)
14083 {
14084 int x[n]; // valid: f is not terminated
14085 setjmp(buf);
14086 g(n);
14087 }
14088 void g(int n)
14089 {
14090 int a[n]; // a may remain allocated
14091 h(n);
14092 }
14093 void h(int n)
14094 {
14095 int b[n]; // b may remain allocated
14096 longjmp(buf, 2); // might cause memory loss
14097 }
14098 </pre>
14100 <p><b>Footnotes</b>
14101 <p><small><a name="note248" href="#note248">248)</a> For example, by executing a return statement or because another longjmp call has caused a
14102 transfer to a setjmp invocation in a function earlier in the set of nested calls.
14103 </small>
14104 <p><small><a name="note249" href="#note249">249)</a> This includes, but is not limited to, the floating-point status flags and the state of open files.
14105 </small>
14109 <p><!--para 1 -->
14110 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
14111 for handling various signals (conditions that may be reported during program execution).
14112 <p><!--para 2 -->
14113 The type defined is
14114 <pre>
14115 sig_atomic_t
14116 </pre>
14117 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
14118 an atomic entity, even in the presence of asynchronous interrupts.
14119 <p><!--para 3 -->
14120 The macros defined are
14121 <pre>
14122 SIG_DFL
14123 SIG_ERR
14124 SIG_IGN
14125 </pre>
14126 which expand to constant expressions with distinct values that have type compatible with
14127 the second argument to, and the return value of, the signal function, and whose values
14128 compare unequal to the address of any declarable function; and the following, which
14129 expand to positive integer constant expressions with type int and distinct values that are
14130 the signal numbers, each corresponding to the specified condition:
14131 <pre>
14132 SIGABRT abnormal termination, such as is initiated by the abort function
14133 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
14134 resulting in overflow
14135 SIGILL detection of an invalid function image, such as an invalid instruction
14136 SIGINT receipt of an interactive attention signal
14137 SIGSEGV an invalid access to storage
14138 SIGTERM a termination request sent to the program
14139 </pre>
14140 <p><!--para 4 -->
14141 An implementation need not generate any of these signals, except as a result of explicit
14142 calls to the raise function. Additional signals and pointers to undeclarable functions,
14143 with macro definitions beginning, respectively, with the letters SIG and an uppercase
14144 letter or with SIG_ and an uppercase letter,<sup><a href="#note250"><b>250)</b></a></sup> may also be specified by the
14145 implementation. The complete set of signals, their semantics, and their default handling
14146 is implementation-defined; all signal numbers shall be positive.
14151 <!--page 284 -->
14153 <p><b>Footnotes</b>
14154 <p><small><a name="note250" href="#note250">250)</a> See ''future library directions'' (<a href="#7.31.7">7.31.7</a>). The names of the signal numbers reflect the following terms
14155 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
14156 and termination.
14157 </small>
14164 <p><b>Synopsis</b>
14165 <p><!--para 1 -->
14166 <pre>
14168 void (*signal(int sig, void (*func)(int)))(int);
14169 </pre>
14170 <p><b>Description</b>
14171 <p><!--para 2 -->
14172 The signal function chooses one of three ways in which receipt of the signal number
14173 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
14174 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
14175 Otherwise, func shall point to a function to be called when that signal occurs. An
14176 invocation of such a function because of a signal, or (recursively) of any further functions
14177 called by that invocation (other than functions in the standard library),<sup><a href="#note251"><b>251)</b></a></sup> is called a
14178 signal handler.
14179 <p><!--para 3 -->
14180 When a signal occurs and func points to a function, it is implementation-defined
14181 whether the equivalent of signal(sig, SIG_DFL); is executed or the
14182 implementation prevents some implementation-defined set of signals (at least including
14183 sig) from occurring until the current signal handling has completed; in the case of
14184 SIGILL, the implementation may alternatively define that no action is taken. Then the
14185 equivalent of (*func)(sig); is executed. If and when the function returns, if the
14186 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
14187 value corresponding to a computational exception, the behavior is undefined; otherwise
14188 the program will resume execution at the point it was interrupted.
14189 <p><!--para 4 -->
14190 If the signal occurs as the result of calling the abort or raise function, the signal
14191 handler shall not call the raise function.
14192 <p><!--para 5 -->
14193 If the signal occurs other than as the result of calling the abort or raise function, the
14194 behavior is undefined if the signal handler refers to any object with static or thread
14195 storage duration that is not a lock-free atomic object other than by assigning a value to an
14196 object declared as volatile sig_atomic_t, or the signal handler calls any function
14197 in the standard library other than the abort function, the _Exit function, the
14198 quick_exit function, or the signal function with the first argument equal to the
14199 signal number corresponding to the signal that caused the invocation of the handler.
14200 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
14204 <!--page 285 -->
14205 <p><!--para 6 -->
14206 At program startup, the equivalent of
14207 <pre>
14208 signal(sig, SIG_IGN);
14209 </pre>
14210 may be executed for some signals selected in an implementation-defined manner; the
14211 equivalent of
14212 <pre>
14213 signal(sig, SIG_DFL);
14214 </pre>
14215 is executed for all other signals defined by the implementation.
14216 <p><!--para 7 -->
14217 Use of this function in a multi-threaded program results in undefined behavior. The
14218 implementation shall behave as if no library function calls the signal function.
14219 <p><b>Returns</b>
14220 <p><!--para 8 -->
14221 If the request can be honored, the signal function returns the value of func for the
14222 most recent successful call to signal for the specified signal sig. Otherwise, a value of
14223 SIG_ERR is returned and a positive value is stored in errno.
14224 <p><b> Forward references</b>: the abort function (<a href="#7.22.4.1">7.22.4.1</a>), the exit function (<a href="#7.22.4.4">7.22.4.4</a>), the
14225 _Exit function (<a href="#7.22.4.5">7.22.4.5</a>), the quick_exit function (<a href="#7.22.4.7">7.22.4.7</a>).
14227 <p><b>Footnotes</b>
14228 <p><small><a name="note251" href="#note251">251)</a> This includes functions called indirectly via standard library functions (e.g., a SIGABRT handler
14229 called via the abort function).
14230 </small>
14231 <p><small><a name="note252" href="#note252">252)</a> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
14232 </small>
14239 <p><b>Synopsis</b>
14240 <p><!--para 1 -->
14241 <pre>
14243 int raise(int sig);
14244 </pre>
14245 <p><b>Description</b>
14246 <p><!--para 2 -->
14247 The raise function carries out the actions described in <a href="#7.14.1.1">7.14.1.1</a> for the signal sig. If a
14248 signal handler is called, the raise function shall not return until after the signal handler
14249 does.
14250 <p><b>Returns</b>
14251 <p><!--para 3 -->
14252 The raise function returns zero if successful, nonzero if unsuccessful.
14253 <!--page 286 -->
14257 <p><!--para 1 -->
14259 <p><!--para 2 -->
14260 The macro
14261 <pre>
14262 alignas
14263 </pre>
14264 expands to _Alignas; the macro
14265 <pre>
14266 alignof
14267 </pre>
14268 expands to _Alignof.
14269 <p><!--para 3 -->
14270 The remaining macros are suitable for use in #if preprocessing directives. They are
14271 <pre>
14272 __alignas_is_defined
14273 </pre>
14274 and
14275 <pre>
14276 __alignof_is_defined
14277 </pre>
14278 which both expand to the integer constant 1.
14279 <!--page 287 -->
14283 <p><!--para 1 -->
14284 The header <a href="#7.16"><stdarg.h></a> declares a type and defines four macros, for advancing
14285 through a list of arguments whose number and types are not known to the called function
14286 when it is translated.
14287 <p><!--para 2 -->
14288 A function may be called with a variable number of arguments of varying types. As
14289 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
14290 parameter plays a special role in the access mechanism, and will be designated parmN in
14291 this description.
14292 <p><!--para 3 -->
14293 The type declared is
14294 <pre>
14295 va_list
14296 </pre>
14297 which is a complete object type suitable for holding information needed by the macros
14298 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
14299 desired, the called function shall declare an object (generally referred to as ap in this
14300 subclause) having type va_list. The object ap may be passed as an argument to
14301 another function; if that function invokes the va_arg macro with parameter ap, the
14302 value of ap in the calling function is indeterminate and shall be passed to the va_end
14305 <p><b>Footnotes</b>
14306 <p><small><a name="note253" href="#note253">253)</a> It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
14307 case the original function may make further use of the original list after the other function returns.
14308 </small>
14312 <p><!--para 1 -->
14313 The va_start and va_arg macros described in this subclause shall be implemented
14314 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
14315 identifiers declared with external linkage. If a macro definition is suppressed in order to
14316 access an actual function, or a program defines an external identifier with the same name,
14317 the behavior is undefined. Each invocation of the va_start and va_copy macros
14318 shall be matched by a corresponding invocation of the va_end macro in the same
14319 function.
14323 <p><b>Synopsis</b>
14324 <p><!--para 1 -->
14325 <pre>
14327 type va_arg(va_list ap, type);
14328 </pre>
14329 <p><b>Description</b>
14330 <p><!--para 2 -->
14331 The va_arg macro expands to an expression that has the specified type and the value of
14332 the next argument in the call. The parameter ap shall have been initialized by the
14333 va_start or va_copy macro (without an intervening invocation of the va_end
14335 <!--page 288 -->
14336 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
14337 values of successive arguments are returned in turn. The parameter type shall be a type
14338 name specified such that the type of a pointer to an object that has the specified type can
14339 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
14340 type is not compatible with the type of the actual next argument (as promoted according
14341 to the default argument promotions), the behavior is undefined, except for the following
14342 cases:
14343 <ul>
14344 <li> one type is a signed integer type, the other type is the corresponding unsigned integer
14345 type, and the value is representable in both types;
14346 <li> one type is pointer to void and the other is a pointer to a character type.
14347 </ul>
14348 <p><b>Returns</b>
14349 <p><!--para 3 -->
14350 The first invocation of the va_arg macro after that of the va_start macro returns the
14351 value of the argument after that specified by parmN . Successive invocations return the
14352 values of the remaining arguments in succession.
14356 <p><b>Synopsis</b>
14357 <p><!--para 1 -->
14358 <pre>
14360 void va_copy(va_list dest, va_list src);
14361 </pre>
14362 <p><b>Description</b>
14363 <p><!--para 2 -->
14364 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
14365 been applied to dest followed by the same sequence of uses of the va_arg macro as
14366 had previously been used to reach the present state of src. Neither the va_copy nor
14367 va_start macro shall be invoked to reinitialize dest without an intervening
14368 invocation of the va_end macro for the same dest.
14369 <p><b>Returns</b>
14370 <p><!--para 3 -->
14371 The va_copy macro returns no value.
14375 <p><b>Synopsis</b>
14376 <p><!--para 1 -->
14377 <pre>
14379 void va_end(va_list ap);
14380 </pre>
14381 <p><b>Description</b>
14382 <p><!--para 2 -->
14383 The va_end macro facilitates a normal return from the function whose variable
14384 argument list was referred to by the expansion of the va_start macro, or the function
14385 containing the expansion of the va_copy macro, that initialized the va_list ap. The
14386 va_end macro may modify ap so that it is no longer usable (without being reinitialized
14387 <!--page 289 -->
14388 by the va_start or va_copy macro). If there is no corresponding invocation of the
14389 va_start or va_copy macro, or if the va_end macro is not invoked before the
14390 return, the behavior is undefined.
14391 <p><b>Returns</b>
14392 <p><!--para 3 -->
14393 The va_end macro returns no value.
14397 <p><b>Synopsis</b>
14398 <p><!--para 1 -->
14399 <pre>
14401 void va_start(va_list ap, parmN);
14402 </pre>
14403 <p><b>Description</b>
14404 <p><!--para 2 -->
14405 The va_start macro shall be invoked before any access to the unnamed arguments.
14406 <p><!--para 3 -->
14407 The va_start macro initializes ap for subsequent use by the va_arg and va_end
14408 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
14409 without an intervening invocation of the va_end macro for the same ap.
14410 <p><!--para 4 -->
14411 The parameter parmN is the identifier of the rightmost parameter in the variable
14412 parameter list in the function definition (the one just before the , ...). If the parameter
14413 parmN is declared with the register storage class, with a function or array type, or
14414 with a type that is not compatible with the type that results after application of the default
14415 argument promotions, the behavior is undefined.
14416 <p><b>Returns</b>
14417 <p><!--para 5 -->
14418 The va_start macro returns no value.
14419 <p><!--para 6 -->
14420 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
14421 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
14422 pointers is specified by the first argument to f1.
14423 <!--page 290 -->
14424 <pre>
14426 #define MAXARGS 31
14427 void f1(int n_ptrs, ...)
14428 {
14429 va_list ap;
14430 char *array[MAXARGS];
14431 int ptr_no = 0;
14432 if (n_ptrs > MAXARGS)
14433 n_ptrs = MAXARGS;
14434 va_start(ap, n_ptrs);
14435 while (ptr_no < n_ptrs)
14436 array[ptr_no++] = va_arg(ap, char *);
14437 va_end(ap);
14438 f2(n_ptrs, array);
14439 }
14440 </pre>
14441 Each call to f1 is required to have visible the definition of the function or a declaration such as
14442 <pre>
14443 void f1(int, ...);
14444 </pre>
14446 <p><!--para 7 -->
14447 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
14448 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
14449 is gathered again and passed to function f4.
14450 <!--page 291 -->
14451 <pre>
14453 #define MAXARGS 31
14454 void f3(int n_ptrs, int f4_after, ...)
14455 {
14456 va_list ap, ap_save;
14457 char *array[MAXARGS];
14458 int ptr_no = 0;
14459 if (n_ptrs > MAXARGS)
14460 n_ptrs = MAXARGS;
14461 va_start(ap, f4_after);
14462 while (ptr_no < n_ptrs) {
14463 array[ptr_no++] = va_arg(ap, char *);
14464 if (ptr_no == f4_after)
14465 va_copy(ap_save, ap);
14466 }
14467 va_end(ap);
14468 f2(n_ptrs, array);
14469 // Now process the saved copy.
14470 n_ptrs -= f4_after;
14471 ptr_no = 0;
14472 while (ptr_no < n_ptrs)
14473 array[ptr_no++] = va_arg(ap_save, char *);
14474 va_end(ap_save);
14475 f4(n_ptrs, array);
14476 }
14477 </pre>
14484 <p><!--para 1 -->
14485 The header <a href="#7.17"><stdatomic.h></a> defines several macros and declares several types and
14486 functions for performing atomic operations on data shared between threads.<sup><a href="#note254"><b>254)</b></a></sup>
14487 <p><!--para 2 -->
14488 Implementations that define the macro __STDC_NO_ATOMICS__ need not provide
14489 this header nor support any of its facilities.
14490 <p><!--para 3 -->
14491 The macros defined are the atomic lock-free macros
14492 <pre>
14493 ATOMIC_BOOL_LOCK_FREE
14494 ATOMIC_CHAR_LOCK_FREE
14495 ATOMIC_CHAR16_T_LOCK_FREE
14496 ATOMIC_CHAR32_T_LOCK_FREE
14497 ATOMIC_WCHAR_T_LOCK_FREE
14498 ATOMIC_SHORT_LOCK_FREE
14499 ATOMIC_INT_LOCK_FREE
14500 ATOMIC_LONG_LOCK_FREE
14501 ATOMIC_LLONG_LOCK_FREE
14502 ATOMIC_POINTER_LOCK_FREE
14503 </pre>
14504 which indicate the lock-free property of the corresponding atomic types (both signed and
14505 unsigned); and
14506 <pre>
14507 ATOMIC_FLAG_INIT
14508 </pre>
14509 which expands to an initializer for an object of type atomic_flag.
14510 <p><!--para 4 -->
14511 The types include
14512 <pre>
14513 memory_order
14514 </pre>
14515 which is an enumerated type whose enumerators identify memory ordering constraints;
14516 <pre>
14517 atomic_flag
14518 </pre>
14519 which is a structure type representing a lock-free, primitive atomic flag; and several *
14520 atomic analogs of integer types.
14521 <p><!--para 5 -->
14522 In the following synopses:
14523 <ul>
14524 <li> An A refers to one of the atomic types.
14525 <li> A C refers to its corresponding non-atomic type. *
14526 <li> An M refers to the type of the other argument for arithmetic operations. For atomic
14527 integer types, M is C. For atomic pointer types, M is ptrdiff_t.
14529 <!--page 292 -->
14530 <li> The functions not ending in _explicit have the same semantics as the
14531 corresponding _explicit function with memory_order_seq_cst for the
14532 memory_order argument.
14533 </ul>
14534 <p><!--para 6 -->
14535 NOTE Many operations are volatile-qualified. The ''volatile as device register'' semantics have not
14536 changed in the standard. This qualification means that volatility is preserved when applying these
14537 operations to volatile objects.
14540 <p><b>Footnotes</b>
14541 <p><small><a name="note254" href="#note254">254)</a> See ''future library directions'' (<a href="#7.31.8">7.31.8</a>).
14542 </small>
14549 <p><b>Synopsis</b>
14550 <p><!--para 1 -->
14551 <pre>
14553 #define ATOMIC_VAR_INIT(C value)
14554 </pre>
14555 <p><b>Description</b>
14556 <p><!--para 2 -->
14557 The ATOMIC_VAR_INIT macro expands to a token sequence suitable for initializing an
14558 atomic object of a type that is initialization-compatible with value. An atomic object
14559 with automatic storage duration that is not explicitly initialized using
14560 ATOMIC_VAR_INIT is initially in an indeterminate state; however, the default (zero)
14561 initialization for objects with static or thread-local storage duration is guaranteed to
14562 produce a valid state.
14563 <p><!--para 3 -->
14564 Concurrent access to the variable being initialized, even via an atomic operation,
14565 constitutes a data race.
14566 <p><!--para 4 -->
14567 EXAMPLE
14568 <pre>
14569 atomic_int guide = ATOMIC_VAR_INIT(42);
14570 </pre>
14575 <p><b>Synopsis</b>
14576 <p><!--para 1 -->
14577 <pre>
14579 void atomic_init(volatile A *obj, C value);
14580 </pre>
14581 <p><b>Description</b>
14582 <p><!--para 2 -->
14583 The atomic_init generic function initializes the atomic object pointed to by obj to
14584 the value value, while also initializing any additional state that the implementation
14585 might need to carry for the atomic object.
14586 <p><!--para 3 -->
14587 Although this function initializes an atomic object, it does not avoid data races;
14588 concurrent access to the variable being initialized, even via an atomic operation,
14589 constitutes a data race.
14590 <!--page 293 -->
14591 <p><b>Returns</b>
14592 <p><!--para 4 -->
14593 The atomic_init generic function returns no value.
14594 <p><!--para 5 -->
14595 EXAMPLE
14596 <pre>
14597 atomic_int guide;
14598 atomic_init(&guide, 42);
14599 </pre>
14604 <p><!--para 1 -->
14605 The enumerated type memory_order specifies the detailed regular (non-atomic)
14606 memory synchronization operations as defined in <a href="#5.1.2.4">5.1.2.4</a> and may provide for operation
14607 ordering. Its enumeration constants are as follows:<sup><a href="#note255"><b>255)</b></a></sup>
14608 <pre>
14609 memory_order_relaxed
14610 memory_order_consume
14611 memory_order_acquire
14612 memory_order_release
14613 memory_order_acq_rel
14614 memory_order_seq_cst
14615 </pre>
14616 <p><!--para 2 -->
14617 For memory_order_relaxed, no operation orders memory.
14618 <p><!--para 3 -->
14619 For memory_order_release, memory_order_acq_rel, and
14620 memory_order_seq_cst, a store operation performs a release operation on the
14621 affected memory location.
14622 <p><!--para 4 -->
14623 For memory_order_acquire, memory_order_acq_rel, and
14624 memory_order_seq_cst, a load operation performs an acquire operation on the
14625 affected memory location.
14626 <p><!--para 5 -->
14627 For memory_order_consume, a load operation performs a consume operation on the
14628 affected memory location.
14629 <p><!--para 6 -->
14630 There shall be a single total order S on all memory_order_seq_cst operations,
14631 consistent with the ''happens before'' order and modification orders for all affected
14632 locations, such that each memory_order_seq_cst operation B that loads a value
14633 from an atomic object M observes one of the following values:
14634 <ul>
14635 <li> the result of the last modification A of M that precedes B in S, if it exists, or
14636 <li> if A exists, the result of some modification of M in the visible sequence of side
14637 effects with respect to B that is not memory_order_seq_cst and that does not
14638 happen before A, or
14643 <!--page 294 -->
14644 <li> if A does not exist, the result of some modification of M in the visible sequence of
14645 side effects with respect to B that is not memory_order_seq_cst.
14646 </ul>
14647 <p><!--para 7 -->
14648 NOTE 1 Although it is not explicitly required that S include lock operations, it can always be extended to
14649 an order that does include lock and unlock operations, since the ordering between those is already included
14650 in the ''happens before'' ordering.
14652 <p><!--para 8 -->
14653 NOTE 2 Atomic operations specifying memory_order_relaxed are relaxed only with respect to
14654 memory ordering. Implementations must still guarantee that any given atomic access to a particular atomic
14655 object be indivisible with respect to all other atomic accesses to that object.
14657 <p><!--para 9 -->
14658 For an atomic operation B that reads the value of an atomic object M, if there is a
14659 memory_order_seq_cst fence X sequenced before B, then B observes either the
14660 last memory_order_seq_cst modification of M preceding X in the total order S or
14661 a later modification of M in its modification order.
14662 <p><!--para 10 -->
14663 For atomic operations A and B on an atomic object M, where A modifies M and B takes
14664 its value, if there is a memory_order_seq_cst fence X such that A is sequenced
14665 before X and B follows X in S, then B observes either the effects of A or a later
14666 modification of M in its modification order.
14667 <p><!--para 11 -->
14668 For atomic operations A and B on an atomic object M, where A modifies M and B takes
14669 its value, if there are memory_order_seq_cst fences X and Y such that A is
14670 sequenced before X, Y is sequenced before B, and X precedes Y in S, then B observes
14671 either the effects of A or a later modification of M in its modification order.
14672 <p><!--para 12 -->
14673 Atomic read-modify-write operations shall always read the last value (in the modification
14674 order) stored before the write associated with the read-modify-write operation.
14675 <p><!--para 13 -->
14676 An atomic store shall only store a value that has been computed from constants and
14677 program input values by a finite sequence of program evaluations, such that each
14678 evaluation observes the values of variables as computed by the last prior assignment in
14679 the sequence.<sup><a href="#note256"><b>256)</b></a></sup> The ordering of evaluations in this sequence shall be such that
14680 <ul>
14681 <li> If an evaluation B observes a value computed by A in a different thread, then B does
14682 not happen before A.
14683 <li> If an evaluation A is included in the sequence, then all evaluations that assign to the
14684 same variable and happen before A are also included.
14685 </ul>
14686 <p><!--para 14 -->
14687 NOTE 3 The second requirement disallows ''out-of-thin-air'', or ''speculative'' stores of atomics when
14688 relaxed atomics are used. Since unordered operations are involved, evaluations may appear in this
14689 sequence out of thread order. For example, with x and y initially zero,
14694 <!--page 295 -->
14695 <pre>
14696 // Thread 1:
14697 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14698 atomic_store_explicit(&x, r1, memory_order_relaxed);
14699 </pre>
14701 <pre>
14702 // Thread 2:
14703 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14704 atomic_store_explicit(&y, 42, memory_order_relaxed);
14705 </pre>
14706 is allowed to produce r1 == 42 && r2 == 42. The sequence of evaluations justifying this consists of:
14707 <pre>
14708 atomic_store_explicit(&y, 42, memory_order_relaxed);
14709 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14710 atomic_store_explicit(&x, r1, memory_order_relaxed);
14711 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14712 </pre>
14713 On the other hand,
14714 <pre>
14715 // Thread 1:
14716 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14717 atomic_store_explicit(&x, r1, memory_order_relaxed);
14718 </pre>
14720 <pre>
14721 // Thread 2:
14722 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14723 atomic_store_explicit(&y, r2, memory_order_relaxed);
14724 </pre>
14725 is not allowed to produce r1 == 42 && r2 = 42, since there is no sequence of evaluations that results
14726 in the computation of 42. In the absence of ''relaxed'' operations and read-modify-write operations with
14727 weaker than memory_order_acq_rel ordering, the second requirement has no impact.
14729 <p><b>Recommended practice</b>
14730 <p><!--para 15 -->
14731 The requirements do not forbid r1 == 42 && r2 == 42 in the following example,
14732 with x and y initially zero:
14733 <pre>
14734 // Thread 1:
14735 r1 = atomic_load_explicit(&x, memory_order_relaxed);
14736 if (r1 == 42)
14737 atomic_store_explicit(&y, r1, memory_order_relaxed);
14738 </pre>
14740 <pre>
14741 // Thread 2:
14742 r2 = atomic_load_explicit(&y, memory_order_relaxed);
14743 if (r2 == 42)
14744 atomic_store_explicit(&x, 42, memory_order_relaxed);
14745 </pre>
14746 However, this is not useful behavior, and implementations should not allow it.
14747 <p><!--para 16 -->
14748 Implementations should make atomic stores visible to atomic loads within a reasonable
14749 amount of time.
14750 <!--page 296 -->
14752 <p><b>Footnotes</b>
14753 <p><small><a name="note255" href="#note255">255)</a> See ''future library directions'' (<a href="#7.31.8">7.31.8</a>).
14754 </small>
14755 <p><small><a name="note256" href="#note256">256)</a> Among other implications, atomic variables shall not decay.
14756 </small>
14760 <p><b>Synopsis</b>
14761 <p><!--para 1 -->
14762 <pre>
14764 type kill_dependency(type y);
14765 </pre>
14766 <p><b>Description</b>
14767 <p><!--para 2 -->
14768 The kill_dependency macro terminates a dependency chain; the argument does not
14769 carry a dependency to the return value.
14770 <p><b>Returns</b>
14771 <p><!--para 3 -->
14772 The kill_dependency macro returns the value of y.
14776 <p><!--para 1 -->
14777 This subclause introduces synchronization primitives called fences. Fences can have
14778 acquire semantics, release semantics, or both. A fence with acquire semantics is called
14779 an acquire fence; a fence with release semantics is called a release fence.
14780 <p><!--para 2 -->
14781 A release fence A synchronizes with an acquire fence B if there exist atomic operations
14782 X and Y , both operating on some atomic object M, such that A is sequenced before X, X
14783 modifies M, Y is sequenced before B, and Y reads the value written by X or a value
14784 written by any side effect in the hypothetical release sequence X would head if it were a
14785 release operation.
14786 <p><!--para 3 -->
14787 A release fence A synchronizes with an atomic operation B that performs an acquire
14788 operation on an atomic object M if there exists an atomic operation X such that A is
14789 sequenced before X, X modifies M, and B reads the value written by X or a value written
14790 by any side effect in the hypothetical release sequence X would head if it were a release
14791 operation.
14792 <p><!--para 4 -->
14793 An atomic operation A that is a release operation on an atomic object M synchronizes
14794 with an acquire fence B if there exists some atomic operation X on M such that X is
14795 sequenced before B and reads the value written by A or a value written by any side effect
14796 in the release sequence headed by A.
14800 <p><b>Synopsis</b>
14801 <p><!--para 1 -->
14802 <pre>
14804 void atomic_thread_fence(memory_order order);
14805 </pre>
14806 <p><b>Description</b>
14807 <p><!--para 2 -->
14808 Depending on the value of order, this operation:
14809 <ul>
14810 <li> has no effects, if order == memory_order_relaxed;
14811 <!--page 297 -->
14812 <li> is an acquire fence, if order == memory_order_acquire or order ==
14813 memory_order_consume;
14814 <li> is a release fence, if order == memory_order_release;
14815 <li> is both an acquire fence and a release fence, if order ==
14816 memory_order_acq_rel;
14817 <li> is a sequentially consistent acquire and release fence, if order ==
14818 memory_order_seq_cst.
14819 </ul>
14820 <p><b>Returns</b>
14821 <p><!--para 3 -->
14822 The atomic_thread_fence function returns no value.
14826 <p><b>Synopsis</b>
14827 <p><!--para 1 -->
14828 <pre>
14830 void atomic_signal_fence(memory_order order);
14831 </pre>
14832 <p><b>Description</b>
14833 <p><!--para 2 -->
14834 Equivalent to atomic_thread_fence(order), except that the resulting ordering
14835 constraints are established only between a thread and a signal handler executed in the
14836 same thread.
14837 <p><!--para 3 -->
14838 NOTE 1 The atomic_signal_fence function can be used to specify the order in which actions
14839 performed by the thread become visible to the signal handler.
14841 <p><!--para 4 -->
14842 NOTE 2 Compiler optimizations and reorderings of loads and stores are inhibited in the same way as with
14843 atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would
14844 have inserted are not emitted.
14846 <p><b>Returns</b>
14847 <p><!--para 5 -->
14848 The atomic_signal_fence function returns no value.
14852 <p><!--para 1 -->
14853 The atomic lock-free macros indicate the lock-free property of integer and address atomic
14854 types. A value of 0 indicates that the type is never lock-free; a value of 1 indicates that
14855 the type is sometimes lock-free; a value of 2 indicates that the type is always lock-free.
14856 <p><!--para 2 -->
14857 NOTE Operations that are lock-free should also be address-free. That is, atomic operations on the same
14858 memory location via two different addresses will communicate atomically. The implementation should not
14859 depend on any per-process state. This restriction enables communication via memory mapped into a
14860 process more than once and memory shared between two processes.
14861 <!--page 298 -->
14864 <h5><a name="7.17.5.1" href="#7.17.5.1">7.17.5.1 The atomic_is_lock_free generic function</a></h5>
14865 <p><b>Synopsis</b>
14866 <p><!--para 1 -->
14867 <pre>
14869 _Bool atomic_is_lock_free(const volatile A *obj);
14870 </pre>
14871 <p><b>Description</b>
14872 <p><!--para 2 -->
14873 The atomic_is_lock_free generic function indicates whether or not the object
14874 pointed to by obj is lock-free. *
14875 <p><b>Returns</b>
14876 <p><!--para 3 -->
14877 The atomic_is_lock_free generic function returns nonzero (true) if and only if the
14878 object's operations are lock-free. The result of a lock-free query on one object cannot be
14879 inferred from the result of a lock-free query on another object.
14883 <p><!--para 1 -->
14884 For each line in the following table,<sup><a href="#note257"><b>257)</b></a></sup> the atomic type name is declared as a type that
14885 has the same representation and alignment requirements as the corresponding direct
14891 <!--page 299 -->
14892 <pre>
14893 Atomic type name Direct type
14894 atomic_bool _Atomic _Bool
14895 atomic_char _Atomic char
14896 atomic_schar _Atomic signed char
14897 atomic_uchar _Atomic unsigned char
14898 atomic_short _Atomic short
14899 atomic_ushort _Atomic unsigned short
14900 atomic_int _Atomic int
14901 atomic_uint _Atomic unsigned int
14902 atomic_long _Atomic long
14903 atomic_ulong _Atomic unsigned long
14904 atomic_llong _Atomic long long
14905 atomic_ullong _Atomic unsigned long long
14906 atomic_char16_t _Atomic char16_t
14907 atomic_char32_t _Atomic char32_t
14908 atomic_wchar_t _Atomic wchar_t
14909 atomic_int_least8_t _Atomic int_least8_t
14910 atomic_uint_least8_t _Atomic uint_least8_t
14911 atomic_int_least16_t _Atomic int_least16_t
14912 atomic_uint_least16_t _Atomic uint_least16_t
14913 atomic_int_least32_t _Atomic int_least32_t
14914 atomic_uint_least32_t _Atomic uint_least32_t
14915 atomic_int_least64_t _Atomic int_least64_t
14916 atomic_uint_least64_t _Atomic uint_least64_t
14917 atomic_int_fast8_t _Atomic int_fast8_t
14918 atomic_uint_fast8_t _Atomic uint_fast8_t
14919 atomic_int_fast16_t _Atomic int_fast16_t
14920 atomic_uint_fast16_t _Atomic uint_fast16_t
14921 atomic_int_fast32_t _Atomic int_fast32_t
14922 atomic_uint_fast32_t _Atomic uint_fast32_t
14923 atomic_int_fast64_t _Atomic int_fast64_t
14924 atomic_uint_fast64_t _Atomic uint_fast64_t
14925 atomic_intptr_t _Atomic intptr_t
14926 atomic_uintptr_t _Atomic uintptr_t
14927 atomic_size_t _Atomic size_t
14928 atomic_ptrdiff_t _Atomic ptrdiff_t
14929 atomic_intmax_t _Atomic intmax_t
14930 atomic_uintmax_t _Atomic uintmax_t
14931 </pre>
14932 <p><!--para 2 -->
14934 <!--page 300 -->
14935 <p><!--para 3 -->
14936 NOTE The representation of atomic integer types need not have the same size as their corresponding
14937 regular types. They should have the same size whenever possible, as it eases effort required to port existing
14938 code.
14941 <p><b>Footnotes</b>
14942 <p><small><a name="note257" href="#note257">257)</a> See ''future library directions'' (<a href="#7.31.8">7.31.8</a>).
14943 </small>
14944 <p><small><a name="note258" href="#note258">258)</a> The same representation and alignment requirements are meant to imply interchangeability as
14945 arguments to functions, return values from functions, and members of unions.
14946 </small>
14950 <p><!--para 1 -->
14951 There are only a few kinds of operations on atomic types, though there are many
14952 instances of those kinds. This subclause specifies each general kind.
14956 <p><b>Synopsis</b>
14957 <p><!--para 1 -->
14958 <pre>
14960 void atomic_store(volatile A *object, C desired);
14961 void atomic_store_explicit(volatile A *object,
14962 C desired, memory_order order);
14963 </pre>
14964 <p><b>Description</b>
14965 <p><!--para 2 -->
14966 The order argument shall not be memory_order_acquire,
14967 memory_order_consume, nor memory_order_acq_rel. Atomically replace the
14968 value pointed to by object with the value of desired. Memory is affected according
14969 to the value of order.
14970 <p><b>Returns</b>
14971 <p><!--para 3 -->
14972 The atomic_store generic functions return no value.
14976 <p><b>Synopsis</b>
14977 <p><!--para 1 -->
14978 <pre>
14980 C atomic_load(volatile A *object);
14981 C atomic_load_explicit(volatile A *object,
14982 memory_order order);
14983 </pre>
14984 <p><b>Description</b>
14985 <p><!--para 2 -->
14986 The order argument shall not be memory_order_release nor
14987 memory_order_acq_rel. Memory is affected according to the value of order.
14988 <p><b>Returns</b>
14989 Atomically returns the value pointed to by object.
14990 <!--page 301 -->
14993 <h5><a name="7.17.7.3" href="#7.17.7.3">7.17.7.3 The atomic_exchange generic functions</a></h5>
14994 <p><b>Synopsis</b>
14995 <p><!--para 1 -->
14996 <pre>
14998 C atomic_exchange(volatile A *object, C desired);
14999 C atomic_exchange_explicit(volatile A *object,
15000 C desired, memory_order order);
15001 </pre>
15002 <p><b>Description</b>
15003 <p><!--para 2 -->
15004 Atomically replace the value pointed to by object with desired. Memory is affected
15005 according to the value of order. These operations are read-modify-write operations
15007 <p><b>Returns</b>
15008 <p><!--para 3 -->
15009 Atomically returns the value pointed to by object immediately before the effects.
15012 <h5><a name="7.17.7.4" href="#7.17.7.4">7.17.7.4 The atomic_compare_exchange generic functions</a></h5>
15013 <p><b>Synopsis</b>
15014 <p><!--para 1 -->
15015 <pre>
15017 _Bool atomic_compare_exchange_strong(volatile A *object,
15018 C *expected, C desired);
15019 _Bool atomic_compare_exchange_strong_explicit(
15020 volatile A *object, C *expected, C desired,
15021 memory_order success, memory_order failure);
15022 _Bool atomic_compare_exchange_weak(volatile A *object,
15023 C *expected, C desired);
15024 _Bool atomic_compare_exchange_weak_explicit(
15025 volatile A *object, C *expected, C desired,
15026 memory_order success, memory_order failure);
15027 </pre>
15028 <p><b>Description</b>
15029 <p><!--para 2 -->
15030 The failure argument shall not be memory_order_release nor
15031 memory_order_acq_rel. The failure argument shall be no stronger than the
15032 success argument. Atomically, compares the value pointed to by object for equality
15033 with that in expected, and if true, replaces the value pointed to by object with
15034 desired, and if false, updates the value in expected with the value pointed to by
15035 object. Further, if the comparison is true, memory is affected according to the value of
15036 success, and if the comparison is false, memory is affected according to the value of
15037 failure. These operations are atomic read-modify-write operations (<a href="#5.1.2.4">5.1.2.4</a>).
15038 <p><!--para 3 -->
15039 NOTE 1 For example, the effect of atomic_compare_exchange_strong is
15040 <!--page 302 -->
15041 <pre>
15042 if (memcmp(object, expected, sizeof (*object)) == 0)
15043 memcpy(object, &desired, sizeof (*object));
15044 else
15045 memcpy(expected, object, sizeof (*object));
15046 </pre>
15048 <p><!--para 4 -->
15049 A weak compare-and-exchange operation may fail spuriously. That is, even when the
15050 contents of memory referred to by expected and object are equal, it may return zero
15051 and store back to expected the same memory contents that were originally there.
15052 <p><!--para 5 -->
15053 NOTE 2 This spurious failure enables implementation of compare-and-exchange on a broader class of
15054 machines, e.g. load-locked store-conditional machines.
15056 <p><!--para 6 -->
15057 EXAMPLE A consequence of spurious failure is that nearly all uses of weak compare-and-exchange will
15058 be in a loop.
15059 <pre>
15060 exp = atomic_load(&cur);
15061 do {
15062 des = function(exp);
15063 } while (!atomic_compare_exchange_weak(&cur, &exp, des));
15064 </pre>
15065 When a compare-and-exchange is in a loop, the weak version will yield better performance on some
15066 platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the
15067 strong one is preferable.
15069 <p><b>Returns</b>
15070 <p><!--para 7 -->
15071 The result of the comparison.
15074 <h5><a name="7.17.7.5" href="#7.17.7.5">7.17.7.5 The atomic_fetch and modify generic functions</a></h5>
15075 <p><!--para 1 -->
15076 The following operations perform arithmetic and bitwise computations. All of these
15077 operations are applicable to an object of any atomic integer type. None of these *
15078 operations is applicable to atomic_bool. The key, operator, and computation
15079 correspondence is:
15080 key op computation
15081 add + addition
15082 sub - subtraction
15083 or | bitwise inclusive or
15084 xor ^ bitwise exclusive or
15085 and & bitwise and
15086 <p><b>Synopsis</b>
15087 <p><!--para 2 -->
15088 <pre>
15090 C atomic_fetch_key(volatile A *object, M operand);
15091 C atomic_fetch_key_explicit(volatile A *object,
15092 M operand, memory_order order);
15093 </pre>
15094 <p><b>Description</b>
15095 <p><!--para 3 -->
15096 Atomically replaces the value pointed to by object with the result of the computation
15097 applied to the value pointed to by object and the given operand. Memory is affected
15098 <!--page 303 -->
15099 according to the value of order. These operations are atomic read-modify-write
15100 operations (<a href="#5.1.2.4">5.1.2.4</a>). For signed integer types, arithmetic is defined to use two's
15101 complement representation with silent wrap-around on overflow; there are no undefined
15102 results. For address types, the result may be an undefined address, but the operations
15103 otherwise have no undefined behavior.
15104 <p><b>Returns</b>
15105 <p><!--para 4 -->
15106 Atomically, the value pointed to by object immediately before the effects.
15107 <p><!--para 5 -->
15108 NOTE The operation of the atomic_fetch and modify generic functions are nearly equivalent to the
15109 operation of the corresponding op= compound assignment operators. The only differences are that the
15110 compound assignment operators are not guaranteed to operate atomically, and the value yielded by a
15111 compound assignment operator is the updated value of the object, whereas the value returned by the
15112 atomic_fetch and modify generic functions is the previous value of the atomic object.
15117 <p><!--para 1 -->
15118 The atomic_flag type provides the classic test-and-set functionality. It has two
15119 states, set and clear.
15120 <p><!--para 2 -->
15121 Operations on an object of type atomic_flag shall be lock free.
15122 <p><!--para 3 -->
15123 NOTE Hence the operations should also be address-free. No other type requires lock-free operations, so
15124 the atomic_flag type is the minimum hardware-implemented type needed to conform to this
15125 International standard. The remaining types can be emulated with atomic_flag, though with less than
15126 ideal properties.
15128 <p><!--para 4 -->
15129 The macro ATOMIC_FLAG_INIT may be used to initialize an atomic_flag to the
15130 clear state. An atomic_flag that is not explicitly initialized with
15131 ATOMIC_FLAG_INIT is initially in an indeterminate state.
15132 <p><!--para 5 -->
15133 EXAMPLE
15134 <pre>
15135 atomic_flag guard = ATOMIC_FLAG_INIT;
15136 </pre>
15140 <h5><a name="7.17.8.1" href="#7.17.8.1">7.17.8.1 The atomic_flag_test_and_set functions</a></h5>
15141 <p><b>Synopsis</b>
15142 <p><!--para 1 -->
15143 <pre>
15145 _Bool atomic_flag_test_and_set(
15146 volatile atomic_flag *object);
15147 _Bool atomic_flag_test_and_set_explicit(
15148 volatile atomic_flag *object, memory_order order);
15149 </pre>
15150 <p><b>Description</b>
15151 <p><!--para 2 -->
15152 Atomically sets the value pointed to by object to true. Memory is affected according
15153 to the value of order. These operations are atomic read-modify-write operations
15155 <!--page 304 -->
15156 <p><b>Returns</b>
15157 <p><!--para 3 -->
15158 Atomically, the value of the object immediately before the effects.
15162 <p><b>Synopsis</b>
15163 <p><!--para 1 -->
15164 <pre>
15166 void atomic_flag_clear(volatile atomic_flag *object);
15167 void atomic_flag_clear_explicit(
15168 volatile atomic_flag *object, memory_order order);
15169 </pre>
15170 <p><b>Description</b>
15171 <p><!--para 2 -->
15172 The order argument shall not be memory_order_acquire nor
15173 memory_order_acq_rel. Atomically sets the value pointed to by object to false.
15174 Memory is affected according to the value of order.
15175 <p><b>Returns</b>
15176 <p><!--para 3 -->
15177 The atomic_flag_clear functions return no value.
15178 <!--page 305 -->
15182 <p><!--para 1 -->
15184 <p><!--para 2 -->
15185 The macro
15186 <pre>
15187 bool
15188 </pre>
15189 expands to _Bool.
15190 <p><!--para 3 -->
15191 The remaining three macros are suitable for use in #if preprocessing directives. They
15192 are
15193 <pre>
15194 true
15195 </pre>
15196 which expands to the integer constant 1,
15197 <pre>
15198 false
15199 </pre>
15200 which expands to the integer constant 0, and
15201 <pre>
15202 __bool_true_false_are_defined
15203 </pre>
15204 which expands to the integer constant 1.
15205 <p><!--para 4 -->
15206 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
15212 <!--page 306 -->
15214 <p><b>Footnotes</b>
15215 <p><small><a name="note259" href="#note259">259)</a> See ''future library directions'' (<a href="#7.31.9">7.31.9</a>).
15216 </small>
15220 <p><!--para 1 -->
15221 The header <a href="#7.19"><stddef.h></a> defines the following macros and declares the following types.
15222 Some are also defined in other headers, as noted in their respective subclauses.
15223 <p><!--para 2 -->
15224 The types are
15225 <pre>
15226 ptrdiff_t
15227 </pre>
15228 which is the signed integer type of the result of subtracting two pointers;
15229 <pre>
15230 size_t
15231 </pre>
15232 which is the unsigned integer type of the result of the sizeof operator;
15233 <pre>
15234 max_align_t
15235 </pre>
15236 which is an object type whose alignment is as great as is supported by the implementation
15237 in all contexts; and
15238 <pre>
15239 wchar_t
15240 </pre>
15241 which is an integer type whose range of values can represent distinct codes for all
15242 members of the largest extended character set specified among the supported locales; the
15243 null character shall have the code value zero. Each member of the basic character set
15244 shall have a code value equal to its value when used as the lone character in an integer
15245 character constant if an implementation does not define
15246 __STDC_MB_MIGHT_NEQ_WC__.
15247 <p><!--para 3 -->
15248 The macros are
15249 <pre>
15250 NULL
15251 </pre>
15252 which expands to an implementation-defined null pointer constant; and
15253 <pre>
15254 offsetof(type, member-designator)
15255 </pre>
15256 which expands to an integer constant expression that has type size_t, the value of
15257 which is the offset in bytes, to the structure member (designated by member-designator),
15258 from the beginning of its structure (designated by type). The type and member designator
15259 shall be such that given
15260 <pre>
15261 static type t;
15262 </pre>
15263 then the expression &(t.member-designator) evaluates to an address constant. (If the
15264 specified member is a bit-field, the behavior is undefined.)
15265 <p><b>Recommended practice</b>
15266 <p><!--para 4 -->
15267 The types used for size_t and ptrdiff_t should not have an integer conversion rank
15268 greater than that of signed long int unless the implementation supports objects
15269 large enough to make this necessary. *
15270 <!--page 307 -->
15274 <p><!--para 1 -->
15275 The header <a href="#7.20"><stdint.h></a> declares sets of integer types having specified widths, and
15276 defines corresponding sets of macros.<sup><a href="#note260"><b>260)</b></a></sup> It also defines macros that specify limits of
15277 integer types corresponding to types defined in other standard headers.
15278 <p><!--para 2 -->
15279 Types are defined in the following categories:
15280 <ul>
15281 <li> integer types having certain exact widths;
15282 <li> integer types having at least certain specified widths;
15283 <li> fastest integer types having at least certain specified widths;
15284 <li> integer types wide enough to hold pointers to objects;
15285 <li> integer types having greatest width.
15286 </ul>
15287 (Some of these types may denote the same type.)
15288 <p><!--para 3 -->
15289 Corresponding macros specify limits of the declared types and construct suitable
15290 constants.
15291 <p><!--para 4 -->
15292 For each type described herein that the implementation provides,<sup><a href="#note261"><b>261)</b></a></sup> <a href="#7.20"><stdint.h></a> shall
15293 declare that typedef name and define the associated macros. Conversely, for each type
15294 described herein that the implementation does not provide, <a href="#7.20"><stdint.h></a> shall not
15295 declare that typedef name nor shall it define the associated macros. An implementation
15296 shall provide those types described as ''required'', but need not provide any of the others
15297 (described as ''optional'').
15299 <p><b>Footnotes</b>
15300 <p><small><a name="note260" href="#note260">260)</a> See ''future library directions'' (<a href="#7.31.10">7.31.10</a>).
15301 </small>
15302 <p><small><a name="note261" href="#note261">261)</a> Some of these types may denote implementation-defined extended integer types.
15303 </small>
15307 <p><!--para 1 -->
15308 When typedef names differing only in the absence or presence of the initial u are defined,
15309 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
15310 implementation providing one of these corresponding types shall also provide the other.
15311 <p><!--para 2 -->
15312 In the following descriptions, the symbol N represents an unsigned decimal integer with
15313 no leading zeros (e.g., 8 or 24, but not 04 or 048).
15318 <!--page 308 -->
15322 <p><!--para 1 -->
15323 The typedef name intN_t designates a signed integer type with width N , no padding
15324 bits, and a two's complement representation. Thus, int8_t denotes such a signed
15325 integer type with a width of exactly 8 bits.
15326 <p><!--para 2 -->
15327 The typedef name uintN_t designates an unsigned integer type with width N and no
15328 padding bits. Thus, uint24_t denotes such an unsigned integer type with a width of
15329 exactly 24 bits.
15330 <p><!--para 3 -->
15331 These types are optional. However, if an implementation provides integer types with
15332 widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
15333 two's complement representation, it shall define the corresponding typedef names.
15337 <p><!--para 1 -->
15338 The typedef name int_leastN_t designates a signed integer type with a width of at
15339 least N , such that no signed integer type with lesser size has at least the specified width.
15340 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
15341 <p><!--para 2 -->
15342 The typedef name uint_leastN_t designates an unsigned integer type with a width
15343 of at least N , such that no unsigned integer type with lesser size has at least the specified
15344 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
15345 least 16 bits.
15346 <p><!--para 3 -->
15347 The following types are required:
15348 <pre>
15349 int_least8_t uint_least8_t
15350 int_least16_t uint_least16_t
15351 int_least32_t uint_least32_t
15352 int_least64_t uint_least64_t
15353 </pre>
15354 All other types of this form are optional.
15358 <p><!--para 1 -->
15359 Each of the following types designates an integer type that is usually fastest<sup><a href="#note262"><b>262)</b></a></sup> to operate
15360 with among all integer types that have at least the specified width.
15361 <p><!--para 2 -->
15362 The typedef name int_fastN_t designates the fastest signed integer type with a width
15363 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
15364 type with a width of at least N .
15369 <!--page 309 -->
15370 <p><!--para 3 -->
15371 The following types are required:
15372 <pre>
15373 int_fast8_t uint_fast8_t
15374 int_fast16_t uint_fast16_t
15375 int_fast32_t uint_fast32_t
15376 int_fast64_t uint_fast64_t
15377 </pre>
15378 All other types of this form are optional.
15380 <p><b>Footnotes</b>
15381 <p><small><a name="note262" href="#note262">262)</a> The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
15382 grounds for choosing one type over another, it will simply pick some integer type satisfying the
15383 signedness and width requirements.
15384 </small>
15387 <h5><a name="7.20.1.4" href="#7.20.1.4">7.20.1.4 Integer types capable of holding object pointers</a></h5>
15388 <p><!--para 1 -->
15389 The following type designates a signed integer type with the property that any valid
15390 pointer to void can be converted to this type, then converted back to pointer to void,
15391 and the result will compare equal to the original pointer:
15392 <pre>
15393 intptr_t
15394 </pre>
15395 The following type designates an unsigned integer type with the property that any valid
15396 pointer to void can be converted to this type, then converted back to pointer to void,
15397 and the result will compare equal to the original pointer:
15398 <pre>
15399 uintptr_t
15400 </pre>
15401 These types are optional.
15405 <p><!--para 1 -->
15406 The following type designates a signed integer type capable of representing any value of
15407 any signed integer type:
15408 <pre>
15409 intmax_t
15410 </pre>
15411 The following type designates an unsigned integer type capable of representing any value
15412 of any unsigned integer type:
15413 <pre>
15414 uintmax_t
15415 </pre>
15416 These types are required.
15420 <p><!--para 1 -->
15421 The following object-like macros specify the minimum and maximum limits of the types
15422 declared in <a href="#7.20"><stdint.h></a>. Each macro name corresponds to a similar type name in
15424 <p><!--para 2 -->
15425 Each instance of any defined macro shall be replaced by a constant expression suitable
15426 for use in #if preprocessing directives, and this expression shall have the same type as
15427 would an expression that is an object of the corresponding type converted according to
15428 the integer promotions. Its implementation-defined value shall be equal to or greater in
15429 magnitude (absolute value) than the corresponding value given below, with the same sign,
15430 except where stated to be exactly the given value.
15431 <!--page 310 -->
15435 <p><!--para 1 -->
15436 <ul>
15437 <li> minimum values of exact-width signed integer types
15438 <pre>
15439 INTN_MIN exactly -(2 N -1 )
15440 </pre>
15441 <li> maximum values of exact-width signed integer types
15442 <pre>
15443 INTN_MAX exactly 2 N -1 - 1
15444 </pre>
15445 <li> maximum values of exact-width unsigned integer types
15446 UINTN_MAX exactly 2 N - 1
15447 </ul>
15450 <h5><a name="7.20.2.2" href="#7.20.2.2">7.20.2.2 Limits of minimum-width integer types</a></h5>
15451 <p><!--para 1 -->
15452 <ul>
15453 <li> minimum values of minimum-width signed integer types
15454 <pre>
15455 INT_LEASTN_MIN -(2 N -1 - 1)
15456 </pre>
15457 <li> maximum values of minimum-width signed integer types
15458 <pre>
15459 INT_LEASTN_MAX 2 N -1 - 1
15460 </pre>
15461 <li> maximum values of minimum-width unsigned integer types
15462 UINT_LEASTN_MAX 2N - 1
15463 </ul>
15466 <h5><a name="7.20.2.3" href="#7.20.2.3">7.20.2.3 Limits of fastest minimum-width integer types</a></h5>
15467 <p><!--para 1 -->
15468 <ul>
15469 <li> minimum values of fastest minimum-width signed integer types
15470 <pre>
15471 INT_FASTN_MIN -(2 N -1 - 1)
15472 </pre>
15473 <li> maximum values of fastest minimum-width signed integer types
15474 INT_FASTN_MAX 2 N -1 - 1
15475 <li> maximum values of fastest minimum-width unsigned integer types
15476 UINT_FASTN_MAX 2N - 1
15477 </ul>
15480 <h5><a name="7.20.2.4" href="#7.20.2.4">7.20.2.4 Limits of integer types capable of holding object pointers</a></h5>
15481 <p><!--para 1 -->
15482 <ul>
15483 <li> minimum value of pointer-holding signed integer type
15484 <pre>
15485 INTPTR_MIN -(215 - 1)
15486 </pre>
15487 <li> maximum value of pointer-holding signed integer type
15488 INTPTR_MAX 215 - 1
15489 <li> maximum value of pointer-holding unsigned integer type
15490 UINTPTR_MAX 216 - 1
15491 <!--page 311 -->
15492 </ul>
15495 <h5><a name="7.20.2.5" href="#7.20.2.5">7.20.2.5 Limits of greatest-width integer types</a></h5>
15496 <p><!--para 1 -->
15497 <ul>
15498 <li> minimum value of greatest-width signed integer type
15499 INTMAX_MIN -(263 - 1)
15500 <li> maximum value of greatest-width signed integer type
15501 INTMAX_MAX 263 - 1
15502 <li> maximum value of greatest-width unsigned integer type
15503 UINTMAX_MAX 264 - 1
15504 </ul>
15508 <p><!--para 1 -->
15509 The following object-like macros specify the minimum and maximum limits of integer
15510 types corresponding to types defined in other standard headers.
15511 <p><!--para 2 -->
15512 Each instance of these macros shall be replaced by a constant expression suitable for use
15513 in #if preprocessing directives, and this expression shall have the same type as would an
15514 expression that is an object of the corresponding type converted according to the integer
15515 promotions. Its implementation-defined value shall be equal to or greater in magnitude
15516 (absolute value) than the corresponding value given below, with the same sign. An
15517 implementation shall define only the macros corresponding to those typedef names it
15519 <ul>
15520 <li> limits of ptrdiff_t
15521 PTRDIFF_MIN -65535
15522 PTRDIFF_MAX +65535
15523 <li> limits of sig_atomic_t
15524 SIG_ATOMIC_MIN see below
15525 SIG_ATOMIC_MAX see below
15526 <li> limit of size_t
15527 SIZE_MAX 65535
15528 <li> limits of wchar_t
15529 WCHAR_MIN see below
15530 WCHAR_MAX see below
15531 <li> limits of wint_t
15536 <!--page 312 -->
15537 WINT_MIN see below
15538 WINT_MAX see below
15539 </ul>
15540 <p><!--para 3 -->
15541 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
15542 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
15543 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
15544 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
15545 SIG_ATOMIC_MAX shall be no less than 255.
15546 <p><!--para 4 -->
15547 If wchar_t (see <a href="#7.19">7.19</a>) is defined as a signed integer type, the value of WCHAR_MIN
15548 shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
15549 otherwise, wchar_t is defined as an unsigned integer type, and the value of
15550 WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.<sup><a href="#note264"><b>264)</b></a></sup>
15551 <p><!--para 5 -->
15552 If wint_t (see <a href="#7.29">7.29</a>) is defined as a signed integer type, the value of WINT_MIN shall
15553 be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
15554 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
15555 shall be 0 and the value of WINT_MAX shall be no less than 65535.
15557 <p><b>Footnotes</b>
15558 <p><small><a name="note263" href="#note263">263)</a> A freestanding implementation need not provide all of these types.
15559 </small>
15560 <p><small><a name="note264" href="#note264">264)</a> The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
15561 character set.
15562 </small>
15566 <p><!--para 1 -->
15567 The following function-like macros expand to integer constants suitable for initializing
15568 objects that have integer types corresponding to types defined in <a href="#7.20"><stdint.h></a>. Each
15569 macro name corresponds to a similar type name in <a href="#7.20.1.2">7.20.1.2</a> or <a href="#7.20.1.5">7.20.1.5</a>.
15570 <p><!--para 2 -->
15571 The argument in any instance of these macros shall be an unsuffixed integer constant (as
15572 defined in <a href="#6.4.4.1">6.4.4.1</a>) with a value that does not exceed the limits for the corresponding type.
15573 <p><!--para 3 -->
15574 Each invocation of one of these macros shall expand to an integer constant expression
15575 suitable for use in #if preprocessing directives. The type of the expression shall have
15576 the same type as would an expression of the corresponding type converted according to
15577 the integer promotions. The value of the expression shall be that of the argument.
15580 <h5><a name="7.20.4.1" href="#7.20.4.1">7.20.4.1 Macros for minimum-width integer constants</a></h5>
15581 <p><!--para 1 -->
15582 The macro INTN_C(value) shall expand to an integer constant expression
15583 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
15584 to an integer constant expression corresponding to the type uint_leastN_t. For
15585 example, if uint_least64_t is a name for the type unsigned long long int,
15586 then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
15591 <!--page 313 -->
15594 <h5><a name="7.20.4.2" href="#7.20.4.2">7.20.4.2 Macros for greatest-width integer constants</a></h5>
15595 <p><!--para 1 -->
15596 The following macro expands to an integer constant expression having the value specified
15597 by its argument and the type intmax_t:
15598 <pre>
15599 INTMAX_C(value)
15600 </pre>
15601 The following macro expands to an integer constant expression having the value specified
15602 by its argument and the type uintmax_t:
15603 <!--page 314 -->
15604 <pre>
15605 UINTMAX_C(value)
15606 </pre>
15613 <p><!--para 1 -->
15614 The header <a href="#7.21"><stdio.h></a> defines several macros, and declares three types and many
15615 functions for performing input and output.
15616 <p><!--para 2 -->
15618 <pre>
15619 FILE
15620 </pre>
15621 which is an object type capable of recording all the information needed to control a
15622 stream, including its file position indicator, a pointer to its associated buffer (if any), an
15623 error indicator that records whether a read/write error has occurred, and an end-of-file
15624 indicator that records whether the end of the file has been reached; and
15625 <pre>
15626 fpos_t
15627 </pre>
15628 which is a complete object type other than an array type capable of recording all the
15629 information needed to specify uniquely every position within a file.
15630 <p><!--para 3 -->
15632 <pre>
15633 _IOFBF
15634 _IOLBF
15635 _IONBF
15636 </pre>
15637 which expand to integer constant expressions with distinct values, suitable for use as the
15638 third argument to the setvbuf function;
15639 <pre>
15640 BUFSIZ
15641 </pre>
15642 which expands to an integer constant expression that is the size of the buffer used by the
15643 setbuf function;
15644 <pre>
15645 EOF
15646 </pre>
15647 which expands to an integer constant expression, with type int and a negative value, that
15648 is returned by several functions to indicate end-of-file, that is, no more input from a
15649 stream;
15650 <pre>
15651 FOPEN_MAX
15652 </pre>
15653 which expands to an integer constant expression that is the minimum number of files that
15654 the implementation guarantees can be open simultaneously;
15655 <pre>
15656 FILENAME_MAX
15657 </pre>
15658 which expands to an integer constant expression that is the size needed for an array of
15659 char large enough to hold the longest file name string that the implementation
15660 <!--page 315 -->
15662 <pre>
15663 L_tmpnam
15664 </pre>
15665 which expands to an integer constant expression that is the size needed for an array of
15666 char large enough to hold a temporary file name string generated by the tmpnam
15667 function;
15668 <pre>
15669 SEEK_CUR
15670 SEEK_END
15671 SEEK_SET
15672 </pre>
15673 which expand to integer constant expressions with distinct values, suitable for use as the
15674 third argument to the fseek function;
15675 <pre>
15676 TMP_MAX
15677 </pre>
15678 which expands to an integer constant expression that is the minimum number of unique
15679 file names that can be generated by the tmpnam function;
15680 <pre>
15681 stderr
15682 stdin
15683 stdout
15684 </pre>
15685 which are expressions of type ''pointer to FILE'' that point to the FILE objects
15686 associated, respectively, with the standard error, input, and output streams.
15687 <p><!--para 4 -->
15688 The header <a href="#7.29"><wchar.h></a> declares a number of functions useful for wide character input
15689 and output. The wide character input/output functions described in that subclause
15690 provide operations analogous to most of those described here, except that the
15691 fundamental units internal to the program are wide characters. The external
15692 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
15694 <p><!--para 5 -->
15695 The input/output functions are given the following collective terms:
15696 <ul>
15697 <li> The wide character input functions -- those functions described in <a href="#7.29">7.29</a> that perform
15698 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
15699 fwscanf, wscanf, vfwscanf, and vwscanf.
15700 <li> The wide character output functions -- those functions described in <a href="#7.29">7.29</a> that perform
15701 output from wide characters and wide strings: fputwc, fputws, putwc,
15702 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
15705 <!--page 316 -->
15706 <li> The wide character input/output functions -- the union of the ungetwc function, the
15707 wide character input functions, and the wide character output functions.
15708 <li> The byte input/output functions -- those functions described in this subclause that
15709 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
15710 fscanf, fwrite, getc, getchar, printf, putc, putchar, puts, scanf,
15711 ungetc, vfprintf, vfscanf, vprintf, and vscanf.
15712 </ul>
15713 <p><b> Forward references</b>: files (<a href="#7.21.3">7.21.3</a>), the fseek function (<a href="#7.21.9.2">7.21.9.2</a>), streams (<a href="#7.21.2">7.21.2</a>), the
15714 tmpnam function (<a href="#7.21.4.4">7.21.4.4</a>), <a href="#7.29"><wchar.h></a> (<a href="#7.29">7.29</a>).
15716 <p><b>Footnotes</b>
15717 <p><small><a name="note265" href="#note265">265)</a> If the implementation imposes no practical limit on the length of file name strings, the value of
15718 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
15719 string. Of course, file name string contents are subject to other system-specific constraints; therefore
15720 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
15721 </small>
15725 <p><!--para 1 -->
15726 Input and output, whether to or from physical devices such as terminals and tape drives,
15727 or whether to or from files supported on structured storage devices, are mapped into
15728 logical data streams, whose properties are more uniform than their various inputs and
15729 outputs. Two forms of mapping are supported, for text streams and for binary
15731 <p><!--para 2 -->
15732 A text stream is an ordered sequence of characters composed into lines, each line
15733 consisting of zero or more characters plus a terminating new-line character. Whether the
15734 last line requires a terminating new-line character is implementation-defined. Characters
15735 may have to be added, altered, or deleted on input and output to conform to differing
15736 conventions for representing text in the host environment. Thus, there need not be a one-
15737 to-one correspondence between the characters in a stream and those in the external
15738 representation. Data read in from a text stream will necessarily compare equal to the data
15739 that were earlier written out to that stream only if: the data consist only of printing
15740 characters and the control characters horizontal tab and new-line; no new-line character is
15741 immediately preceded by space characters; and the last character is a new-line character.
15742 Whether space characters that are written out immediately before a new-line character
15743 appear when read in is implementation-defined.
15744 <p><!--para 3 -->
15745 A binary stream is an ordered sequence of characters that can transparently record
15746 internal data. Data read in from a binary stream shall compare equal to the data that were
15747 earlier written out to that stream, under the same implementation. Such a stream may,
15748 however, have an implementation-defined number of null characters appended to the end
15749 of the stream.
15750 <p><!--para 4 -->
15751 Each stream has an orientation. After a stream is associated with an external file, but
15752 before any operations are performed on it, the stream is without orientation. Once a wide
15753 character input/output function has been applied to a stream without orientation, the
15756 <!--page 317 -->
15757 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
15758 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
15759 Only a call to the freopen function or the fwide function can otherwise alter the
15760 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note267"><b>267)</b></a></sup>
15761 <p><!--para 5 -->
15762 Byte input/output functions shall not be applied to a wide-oriented stream and wide
15763 character input/output functions shall not be applied to a byte-oriented stream. The
15764 remaining stream operations do not affect, and are not affected by, a stream's orientation,
15765 except for the following additional restrictions:
15766 <ul>
15767 <li> Binary wide-oriented streams have the file-positioning restrictions ascribed to both
15768 text and binary streams.
15769 <li> For wide-oriented streams, after a successful call to a file-positioning function that
15770 leaves the file position indicator prior to the end-of-file, a wide character output
15771 function can overwrite a partial multibyte character; any file contents beyond the
15772 byte(s) written are henceforth indeterminate.
15773 </ul>
15774 <p><!--para 6 -->
15775 Each wide-oriented stream has an associated mbstate_t object that stores the current
15776 parse state of the stream. A successful call to fgetpos stores a representation of the
15777 value of this mbstate_t object as part of the value of the fpos_t object. A later
15778 successful call to fsetpos using the same stored fpos_t value restores the value of
15779 the associated mbstate_t object as well as the position within the controlled stream.
15780 <p><!--para 7 -->
15781 Each stream has an associated lock that is used to prevent data races when multiple
15782 threads of execution access a stream, and to restrict the interleaving of stream operations
15783 performed by multiple threads. Only one thread may hold this lock at a time. The lock is
15784 reentrant: a single thread may hold the lock multiple times at a given time.
15785 <p><!--para 8 -->
15786 All functions that read, write, position, or query the position of a stream lock the stream
15787 before accessing it. They release the lock associated with the stream when the access is
15788 complete.
15789 <p><b>Environmental limits</b>
15790 <p><!--para 9 -->
15791 An implementation shall support text files with lines containing at least 254 characters,
15792 including the terminating new-line character. The value of the macro BUFSIZ shall be at
15793 least 256.
15794 <p><b> Forward references</b>: the freopen function (<a href="#7.21.5.4">7.21.5.4</a>), the fwide function (<a href="#7.29.3.5">7.29.3.5</a>),
15795 mbstate_t (<a href="#7.30.1">7.30.1</a>), the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>), the fsetpos function
15801 <!--page 318 -->
15803 <p><b>Footnotes</b>
15804 <p><small><a name="note266" href="#note266">266)</a> An implementation need not distinguish between text streams and binary streams. In such an
15805 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
15806 line.
15807 </small>
15808 <p><small><a name="note267" href="#note267">267)</a> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
15809 </small>
15813 <p><!--para 1 -->
15814 A stream is associated with an external file (which may be a physical device) by opening
15815 a file, which may involve creating a new file. Creating an existing file causes its former
15816 contents to be discarded, if necessary. If a file can support positioning requests (such as a
15817 disk file, as opposed to a terminal), then a file position indicator associated with the
15818 stream is positioned at the start (character number zero) of the file, unless the file is
15819 opened with append mode in which case it is implementation-defined whether the file
15820 position indicator is initially positioned at the beginning or the end of the file. The file
15821 position indicator is maintained by subsequent reads, writes, and positioning requests, to
15822 facilitate an orderly progression through the file.
15823 <p><!--para 2 -->
15824 Binary files are not truncated, except as defined in <a href="#7.21.5.3">7.21.5.3</a>. Whether a write on a text
15825 stream causes the associated file to be truncated beyond that point is implementation-
15826 defined.
15827 <p><!--para 3 -->
15828 When a stream is unbuffered, characters are intended to appear from the source or at the
15829 destination as soon as possible. Otherwise characters may be accumulated and
15830 transmitted to or from the host environment as a block. When a stream is fully buffered,
15831 characters are intended to be transmitted to or from the host environment as a block when
15832 a buffer is filled. When a stream is line buffered, characters are intended to be
15833 transmitted to or from the host environment as a block when a new-line character is
15834 encountered. Furthermore, characters are intended to be transmitted as a block to the host
15835 environment when a buffer is filled, when input is requested on an unbuffered stream, or
15836 when input is requested on a line buffered stream that requires the transmission of
15837 characters from the host environment. Support for these characteristics is
15838 implementation-defined, and may be affected via the setbuf and setvbuf functions.
15839 <p><!--para 4 -->
15840 A file may be disassociated from a controlling stream by closing the file. Output streams
15841 are flushed (any unwritten buffer contents are transmitted to the host environment) before
15842 the stream is disassociated from the file. The value of a pointer to a FILE object is
15843 indeterminate after the associated file is closed (including the standard text streams).
15844 Whether a file of zero length (on which no characters have been written by an output
15845 stream) actually exists is implementation-defined.
15846 <p><!--para 5 -->
15847 The file may be subsequently reopened, by the same or another program execution, and
15848 its contents reclaimed or modified (if it can be repositioned at its start). If the main
15849 function returns to its original caller, or if the exit function is called, all open files are
15850 closed (hence all output streams are flushed) before program termination. Other paths to
15851 program termination, such as calling the abort function, need not close all files
15852 properly.
15853 <p><!--para 6 -->
15854 The address of the FILE object used to control a stream may be significant; a copy of a
15855 FILE object need not serve in place of the original.
15856 <!--page 319 -->
15857 <p><!--para 7 -->
15858 At program startup, three text streams are predefined and need not be opened explicitly
15859 <ul>
15860 <li> standard input (for reading conventional input), standard output (for writing
15861 </ul>
15862 conventional output), and standard error (for writing diagnostic output). As initially
15863 opened, the standard error stream is not fully buffered; the standard input and standard
15864 output streams are fully buffered if and only if the stream can be determined not to refer
15865 to an interactive device.
15866 <p><!--para 8 -->
15867 Functions that open additional (nontemporary) files require a file name, which is a string.
15868 The rules for composing valid file names are implementation-defined. Whether the same
15869 file can be simultaneously open multiple times is also implementation-defined.
15870 <p><!--para 9 -->
15871 Although both text and binary wide-oriented streams are conceptually sequences of wide
15872 characters, the external file associated with a wide-oriented stream is a sequence of
15873 multibyte characters, generalized as follows:
15874 <ul>
15875 <li> Multibyte encodings within files may contain embedded null bytes (unlike multibyte
15876 encodings valid for use internal to the program).
15877 <li> A file need not begin nor end in the initial shift state.<sup><a href="#note268"><b>268)</b></a></sup>
15878 </ul>
15879 <p><!--para 10 -->
15880 Moreover, the encodings used for multibyte characters may differ among files. Both the
15881 nature and choice of such encodings are implementation-defined.
15882 <p><!--para 11 -->
15883 The wide character input functions read multibyte characters from the stream and convert
15884 them to wide characters as if they were read by successive calls to the fgetwc function.
15885 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
15886 described by the stream's own mbstate_t object. The byte input functions read
15887 characters from the stream as if by successive calls to the fgetc function.
15888 <p><!--para 12 -->
15889 The wide character output functions convert wide characters to multibyte characters and
15890 write them to the stream as if they were written by successive calls to the fputwc
15891 function. Each conversion occurs as if by a call to the wcrtomb function, with the
15892 conversion state described by the stream's own mbstate_t object. The byte output
15893 functions write characters to the stream as if by successive calls to the fputc function.
15894 <p><!--para 13 -->
15895 In some cases, some of the byte input/output functions also perform conversions between
15896 multibyte characters and wide characters. These conversions also occur as if by calls to
15897 the mbrtowc and wcrtomb functions.
15898 <p><!--para 14 -->
15899 An encoding error occurs if the character sequence presented to the underlying
15900 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
15901 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
15904 <!--page 320 -->
15905 multibyte character. The wide character input/output functions and the byte input/output
15906 functions store the value of the macro EILSEQ in errno if and only if an encoding error
15907 occurs.
15908 <p><b>Environmental limits</b>
15909 <p><!--para 15 -->
15910 The value of FOPEN_MAX shall be at least eight, including the three standard text
15911 streams.
15912 <p><b> Forward references</b>: the exit function (<a href="#7.22.4.4">7.22.4.4</a>), the fgetc function (<a href="#7.21.7.1">7.21.7.1</a>), the
15913 fopen function (<a href="#7.21.5.3">7.21.5.3</a>), the fputc function (<a href="#7.21.7.3">7.21.7.3</a>), the setbuf function
15914 (<a href="#7.21.5.5">7.21.5.5</a>), the setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>), the fgetwc function (<a href="#7.29.3.1">7.29.3.1</a>), the
15915 fputwc function (<a href="#7.29.3.3">7.29.3.3</a>), conversion state (<a href="#7.29.6">7.29.6</a>), the mbrtowc function
15916 (<a href="#7.29.6.3.2">7.29.6.3.2</a>), the wcrtomb function (<a href="#7.29.6.3.3">7.29.6.3.3</a>).
15918 <p><b>Footnotes</b>
15919 <p><small><a name="note268" href="#note268">268)</a> Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
15920 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
15921 with state-dependent encoding that does not assuredly end in the initial shift state.
15922 </small>
15929 <p><b>Synopsis</b>
15930 <p><!--para 1 -->
15931 <pre>
15933 int remove(const char *filename);
15934 </pre>
15935 <p><b>Description</b>
15936 <p><!--para 2 -->
15937 The remove function causes the file whose name is the string pointed to by filename
15938 to be no longer accessible by that name. A subsequent attempt to open that file using that
15939 name will fail, unless it is created anew. If the file is open, the behavior of the remove
15940 function is implementation-defined.
15941 <p><b>Returns</b>
15942 <p><!--para 3 -->
15943 The remove function returns zero if the operation succeeds, nonzero if it fails.
15947 <p><b>Synopsis</b>
15948 <p><!--para 1 -->
15949 <pre>
15951 int rename(const char *old, const char *new);
15952 </pre>
15953 <p><b>Description</b>
15954 <p><!--para 2 -->
15955 The rename function causes the file whose name is the string pointed to by old to be
15956 henceforth known by the name given by the string pointed to by new. The file named
15957 old is no longer accessible by that name. If a file named by the string pointed to by new
15958 exists prior to the call to the rename function, the behavior is implementation-defined.
15959 <!--page 321 -->
15960 <p><b>Returns</b>
15961 <p><!--para 3 -->
15962 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note269"><b>269)</b></a></sup> in
15963 which case if the file existed previously it is still known by its original name.
15965 <p><b>Footnotes</b>
15966 <p><small><a name="note269" href="#note269">269)</a> Among the reasons the implementation may cause the rename function to fail are that the file is open
15967 or that it is necessary to copy its contents to effectuate its renaming.
15968 </small>
15972 <p><b>Synopsis</b>
15973 <p><!--para 1 -->
15974 <pre>
15976 FILE *tmpfile(void);
15977 </pre>
15978 <p><b>Description</b>
15979 <p><!--para 2 -->
15980 The tmpfile function creates a temporary binary file that is different from any other
15981 existing file and that will automatically be removed when it is closed or at program
15982 termination. If the program terminates abnormally, whether an open temporary file is
15984 <p><b>Recommended practice</b>
15985 <p><!--para 3 -->
15986 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
15987 program (this limit may be shared with tmpnam) and there should be no limit on the
15988 number simultaneously open other than this limit and any limit on the number of open
15989 files (FOPEN_MAX).
15990 <p><b>Returns</b>
15991 <p><!--para 4 -->
15992 The tmpfile function returns a pointer to the stream of the file that it created. If the file
15993 cannot be created, the tmpfile function returns a null pointer.
15998 <p><b>Synopsis</b>
15999 <p><!--para 1 -->
16000 <pre>
16002 char *tmpnam(char *s);
16003 </pre>
16004 <p><b>Description</b>
16005 <p><!--para 2 -->
16006 The tmpnam function generates a string that is a valid file name and that is not the same
16007 as the name of an existing file.<sup><a href="#note270"><b>270)</b></a></sup> The function is potentially capable of generating at
16010 <!--page 322 -->
16011 least TMP_MAX different strings, but any or all of them may already be in use by existing
16012 files and thus not be suitable return values.
16013 <p><!--para 3 -->
16014 The tmpnam function generates a different string each time it is called.
16015 <p><!--para 4 -->
16016 Calls to the tmpnam function with a null pointer argument may introduce data races with
16017 each other. The implementation shall behave as if no library function calls the tmpnam
16018 function.
16019 <p><b>Returns</b>
16020 <p><!--para 5 -->
16021 If no suitable string can be generated, the tmpnam function returns a null pointer.
16022 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
16023 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
16024 function may modify the same object). If the argument is not a null pointer, it is assumed
16025 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
16026 in that array and returns the argument as its value.
16027 <p><b>Environmental limits</b>
16028 <p><!--para 6 -->
16029 The value of the macro TMP_MAX shall be at least 25.
16031 <p><b>Footnotes</b>
16032 <p><small><a name="note270" href="#note270">270)</a> Files created using strings generated by the tmpnam function are temporary only in the sense that
16033 their names should not collide with those generated by conventional naming rules for the
16034 implementation. It is still necessary to use the remove function to remove such files when their use
16035 is ended, and before program termination.
16036 </small>
16043 <p><b>Synopsis</b>
16044 <p><!--para 1 -->
16045 <pre>
16047 int fclose(FILE *stream);
16048 </pre>
16049 <p><b>Description</b>
16050 <p><!--para 2 -->
16051 A successful call to the fclose function causes the stream pointed to by stream to be
16052 flushed and the associated file to be closed. Any unwritten buffered data for the stream
16053 are delivered to the host environment to be written to the file; any unread buffered data
16054 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
16055 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
16056 (and deallocated if it was automatically allocated).
16057 <p><b>Returns</b>
16058 <p><!--para 3 -->
16059 The fclose function returns zero if the stream was successfully closed, or EOF if any
16060 errors were detected.
16061 <!--page 323 -->
16065 <p><b>Synopsis</b>
16066 <p><!--para 1 -->
16067 <pre>
16069 int fflush(FILE *stream);
16070 </pre>
16071 <p><b>Description</b>
16072 <p><!--para 2 -->
16073 If stream points to an output stream or an update stream in which the most recent
16074 operation was not input, the fflush function causes any unwritten data for that stream
16075 to be delivered to the host environment to be written to the file; otherwise, the behavior is
16076 undefined.
16077 <p><!--para 3 -->
16078 If stream is a null pointer, the fflush function performs this flushing action on all
16079 streams for which the behavior is defined above.
16080 <p><b>Returns</b>
16081 <p><!--para 4 -->
16082 The fflush function sets the error indicator for the stream and returns EOF if a write
16083 error occurs, otherwise it returns zero.
16088 <p><b>Synopsis</b>
16089 <p><!--para 1 -->
16090 <pre>
16092 FILE *fopen(const char * restrict filename,
16093 const char * restrict mode);
16094 </pre>
16095 <p><b>Description</b>
16096 <p><!--para 2 -->
16097 The fopen function opens the file whose name is the string pointed to by filename,
16098 and associates a stream with it.
16099 <p><!--para 3 -->
16100 The argument mode points to a string. If the string is one of the following, the file is
16101 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note271"><b>271)</b></a></sup>
16102 r open text file for reading
16103 w truncate to zero length or create text file for writing
16104 wx create text file for writing
16105 a append; open or create text file for writing at end-of-file
16106 rb open binary file for reading
16107 wb truncate to zero length or create binary file for writing
16110 <!--page 324 -->
16111 wbx create binary file for writing
16112 ab append; open or create binary file for writing at end-of-file
16113 r+ open text file for update (reading and writing)
16114 w+ truncate to zero length or create text file for update
16115 w+x create text file for update
16116 a+ append; open or create text file for update, writing at end-of-file
16117 r+b or rb+ open binary file for update (reading and writing)
16118 w+b or wb+ truncate to zero length or create binary file for update
16119 w+bx or wb+x create binary file for update
16120 a+b or ab+ append; open or create binary file for update, writing at end-of-file
16121 <p><!--para 4 -->
16122 Opening a file with read mode ('r' as the first character in the mode argument) fails if
16123 the file does not exist or cannot be read.
16124 <p><!--para 5 -->
16125 Opening a file with exclusive mode ('x' as the last character in the mode argument)
16126 fails if the file already exists or cannot be created. Otherwise, the file is created with
16127 exclusive (also known as non-shared) access to the extent that the underlying system
16128 supports exclusive access.
16129 <p><!--para 6 -->
16130 Opening a file with append mode ('a' as the first character in the mode argument)
16131 causes all subsequent writes to the file to be forced to the then current end-of-file,
16132 regardless of intervening calls to the fseek function. In some implementations, opening
16133 a binary file with append mode ('b' as the second or third character in the above list of
16134 mode argument values) may initially position the file position indicator for the stream
16135 beyond the last data written, because of null character padding.
16136 <p><!--para 7 -->
16137 When a file is opened with update mode ('+' as the second or third character in the
16138 above list of mode argument values), both input and output may be performed on the
16139 associated stream. However, output shall not be directly followed by input without an
16140 intervening call to the fflush function or to a file positioning function (fseek,
16141 fsetpos, or rewind), and input shall not be directly followed by output without an
16142 intervening call to a file positioning function, unless the input operation encounters end-
16143 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
16144 binary stream in some implementations.
16145 <p><!--para 8 -->
16146 When opened, a stream is fully buffered if and only if it can be determined not to refer to
16147 an interactive device. The error and end-of-file indicators for the stream are cleared.
16148 <p><b>Returns</b>
16149 <p><!--para 9 -->
16150 The fopen function returns a pointer to the object controlling the stream. If the open
16151 operation fails, fopen returns a null pointer.
16153 <!--page 325 -->
16155 <p><b>Footnotes</b>
16156 <p><small><a name="note271" href="#note271">271)</a> If the string begins with one of the above sequences, the implementation might choose to ignore the
16157 remaining characters, or it might use them to select different kinds of a file (some of which might not
16159 </small>
16163 <p><b>Synopsis</b>
16164 <p><!--para 1 -->
16165 <pre>
16167 FILE *freopen(const char * restrict filename,
16168 const char * restrict mode,
16169 FILE * restrict stream);
16170 </pre>
16171 <p><b>Description</b>
16172 <p><!--para 2 -->
16173 The freopen function opens the file whose name is the string pointed to by filename
16174 and associates the stream pointed to by stream with it. The mode argument is used just
16176 <p><!--para 3 -->
16177 If filename is a null pointer, the freopen function attempts to change the mode of
16178 the stream to that specified by mode, as if the name of the file currently associated with
16179 the stream had been used. It is implementation-defined which changes of mode are
16180 permitted (if any), and under what circumstances.
16181 <p><!--para 4 -->
16182 The freopen function first attempts to close any file that is associated with the specified
16183 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
16184 stream are cleared.
16185 <p><b>Returns</b>
16186 <p><!--para 5 -->
16187 The freopen function returns a null pointer if the open operation fails. Otherwise,
16188 freopen returns the value of stream.
16190 <p><b>Footnotes</b>
16191 <p><small><a name="note272" href="#note272">272)</a> The primary use of the freopen function is to change the file associated with a standard text stream
16192 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
16193 returned by the fopen function may be assigned.
16194 </small>
16198 <p><b>Synopsis</b>
16199 <p><!--para 1 -->
16200 <pre>
16202 void setbuf(FILE * restrict stream,
16203 char * restrict buf);
16204 </pre>
16205 <p><b>Description</b>
16206 <p><!--para 2 -->
16207 Except that it returns no value, the setbuf function is equivalent to the setvbuf
16208 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
16209 is a null pointer), with the value _IONBF for mode.
16214 <!--page 326 -->
16215 <p><b>Returns</b>
16216 <p><!--para 3 -->
16217 The setbuf function returns no value.
16222 <p><b>Synopsis</b>
16223 <p><!--para 1 -->
16224 <pre>
16226 int setvbuf(FILE * restrict stream,
16227 char * restrict buf,
16228 int mode, size_t size);
16229 </pre>
16230 <p><b>Description</b>
16231 <p><!--para 2 -->
16232 The setvbuf function may be used only after the stream pointed to by stream has
16233 been associated with an open file and before any other operation (other than an
16234 unsuccessful call to setvbuf) is performed on the stream. The argument mode
16235 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
16236 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
16237 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
16238 used instead of a buffer allocated by the setvbuf function<sup><a href="#note273"><b>273)</b></a></sup> and the argument size
16239 specifies the size of the array; otherwise, size may determine the size of a buffer
16240 allocated by the setvbuf function. The contents of the array at any time are
16241 indeterminate.
16242 <p><b>Returns</b>
16243 <p><!--para 3 -->
16244 The setvbuf function returns zero on success, or nonzero if an invalid value is given
16245 for mode or if the request cannot be honored.
16250 <!--page 327 -->
16252 <p><b>Footnotes</b>
16253 <p><small><a name="note273" href="#note273">273)</a> The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
16254 before a buffer that has automatic storage duration is deallocated upon block exit.
16255 </small>
16259 <p><!--para 1 -->
16260 The formatted input/output functions shall behave as if there is a sequence point after the
16263 <p><b>Footnotes</b>
16264 <p><small><a name="note274" href="#note274">274)</a> The fprintf functions perform writes to memory for the %n specifier.
16265 </small>
16269 <p><b>Synopsis</b>
16270 <p><!--para 1 -->
16271 <pre>
16273 int fprintf(FILE * restrict stream,
16274 const char * restrict format, ...);
16275 </pre>
16276 <p><b>Description</b>
16277 <p><!--para 2 -->
16278 The fprintf function writes output to the stream pointed to by stream, under control
16279 of the string pointed to by format that specifies how subsequent arguments are
16280 converted for output. If there are insufficient arguments for the format, the behavior is
16281 undefined. If the format is exhausted while arguments remain, the excess arguments are
16282 evaluated (as always) but are otherwise ignored. The fprintf function returns when
16283 the end of the format string is encountered.
16284 <p><!--para 3 -->
16285 The format shall be a multibyte character sequence, beginning and ending in its initial
16286 shift state. The format is composed of zero or more directives: ordinary multibyte
16287 characters (not %), which are copied unchanged to the output stream; and conversion
16288 specifications, each of which results in fetching zero or more subsequent arguments,
16289 converting them, if applicable, according to the corresponding conversion specifier, and
16290 then writing the result to the output stream.
16291 <p><!--para 4 -->
16292 Each conversion specification is introduced by the character %. After the %, the following
16293 appear in sequence:
16294 <ul>
16295 <li> Zero or more flags (in any order) that modify the meaning of the conversion
16296 specification.
16297 <li> An optional minimum field width. If the converted value has fewer characters than the
16298 field width, it is padded with spaces (by default) on the left (or right, if the left
16299 adjustment flag, described later, has been given) to the field width. The field width
16300 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note275"><b>275)</b></a></sup>
16301 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
16302 o, u, x, and X conversions, the number of digits to appear after the decimal-point
16303 character for a, A, e, E, f, and F conversions, the maximum number of significant
16304 digits for the g and G conversions, or the maximum number of bytes to be written for
16307 <!--page 328 -->
16308 s conversions. The precision takes the form of a period (.) followed either by an
16309 asterisk * (described later) or by an optional decimal integer; if only the period is
16310 specified, the precision is taken as zero. If a precision appears with any other
16311 conversion specifier, the behavior is undefined.
16312 <li> An optional length modifier that specifies the size of the argument.
16313 <li> A conversion specifier character that specifies the type of conversion to be applied.
16314 </ul>
16315 <p><!--para 5 -->
16316 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
16317 this case, an int argument supplies the field width or precision. The arguments
16318 specifying field width, or precision, or both, shall appear (in that order) before the
16319 argument (if any) to be converted. A negative field width argument is taken as a - flag
16320 followed by a positive field width. A negative precision argument is taken as if the
16321 precision were omitted.
16322 <p><!--para 6 -->
16323 The flag characters and their meanings are:
16324 - The result of the conversion is left-justified within the field. (It is right-justified if
16325 <pre>
16326 this flag is not specified.)
16327 </pre>
16328 + The result of a signed conversion always begins with a plus or minus sign. (It
16329 <pre>
16330 begins with a sign only when a negative value is converted if this flag is not
16332 </pre>
16333 space If the first character of a signed conversion is not a sign, or if a signed conversion
16334 <pre>
16335 results in no characters, a space is prefixed to the result. If the space and + flags
16336 both appear, the space flag is ignored.
16337 </pre>
16338 # The result is converted to an ''alternative form''. For o conversion, it increases
16339 <pre>
16340 the precision, if and only if necessary, to force the first digit of the result to be a
16341 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
16342 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
16343 and G conversions, the result of converting a floating-point number always
16344 contains a decimal-point character, even if no digits follow it. (Normally, a
16345 decimal-point character appears in the result of these conversions only if a digit
16346 follows it.) For g and G conversions, trailing zeros are not removed from the
16347 result. For other conversions, the behavior is undefined.
16348 </pre>
16349 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
16350 <pre>
16351 (following any indication of sign or base) are used to pad to the field width rather
16352 than performing space padding, except when converting an infinity or NaN. If the
16353 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
16354 </pre>
16357 <!--page 329 -->
16358 <pre>
16359 conversions, if a precision is specified, the 0 flag is ignored. For other
16360 conversions, the behavior is undefined.
16361 </pre>
16362 <p><!--para 7 -->
16363 The length modifiers and their meanings are:
16364 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16365 <pre>
16366 signed char or unsigned char argument (the argument will have
16367 been promoted according to the integer promotions, but its value shall be
16368 converted to signed char or unsigned char before printing); or that
16369 a following n conversion specifier applies to a pointer to a signed char
16370 argument.
16371 </pre>
16372 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16373 <pre>
16374 short int or unsigned short int argument (the argument will
16375 have been promoted according to the integer promotions, but its value shall
16376 be converted to short int or unsigned short int before printing);
16377 or that a following n conversion specifier applies to a pointer to a short
16378 int argument.
16379 </pre>
16380 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16381 <pre>
16382 long int or unsigned long int argument; that a following n
16383 conversion specifier applies to a pointer to a long int argument; that a
16384 following c conversion specifier applies to a wint_t argument; that a
16385 following s conversion specifier applies to a pointer to a wchar_t
16386 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
16387 specifier.
16388 </pre>
16389 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16390 <pre>
16391 long long int or unsigned long long int argument; or that a
16392 following n conversion specifier applies to a pointer to a long long int
16393 argument.
16394 </pre>
16395 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
16396 <pre>
16397 an intmax_t or uintmax_t argument; or that a following n conversion
16398 specifier applies to a pointer to an intmax_t argument.
16399 </pre>
16400 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16401 <pre>
16402 size_t or the corresponding signed integer type argument; or that a
16403 following n conversion specifier applies to a pointer to a signed integer type
16404 corresponding to size_t argument.
16405 </pre>
16406 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16407 <!--page 330 -->
16408 <pre>
16409 ptrdiff_t or the corresponding unsigned integer type argument; or that a
16410 following n conversion specifier applies to a pointer to a ptrdiff_t
16411 argument.
16412 </pre>
16413 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16414 <pre>
16415 applies to a long double argument.
16416 </pre>
16417 If a length modifier appears with any conversion specifier other than as specified above,
16418 the behavior is undefined.
16419 <p><!--para 8 -->
16420 The conversion specifiers and their meanings are:
16421 d,i The int argument is converted to signed decimal in the style [-]dddd. The
16422 <pre>
16423 precision specifies the minimum number of digits to appear; if the value
16424 being converted can be represented in fewer digits, it is expanded with
16425 leading zeros. The default precision is 1. The result of converting a zero
16426 value with a precision of zero is no characters.
16427 </pre>
16428 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
16429 <pre>
16430 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
16431 letters abcdef are used for x conversion and the letters ABCDEF for X
16432 conversion. The precision specifies the minimum number of digits to appear;
16433 if the value being converted can be represented in fewer digits, it is expanded
16434 with leading zeros. The default precision is 1. The result of converting a
16435 zero value with a precision of zero is no characters.
16436 </pre>
16437 f,F A double argument representing a floating-point number is converted to
16438 <pre>
16439 decimal notation in the style [-]ddd.ddd, where the number of digits after
16440 the decimal-point character is equal to the precision specification. If the
16441 precision is missing, it is taken as 6; if the precision is zero and the # flag is
16442 not specified, no decimal-point character appears. If a decimal-point
16443 character appears, at least one digit appears before it. The value is rounded to
16444 the appropriate number of digits.
16445 A double argument representing an infinity is converted in one of the styles
16446 [-]inf or [-]infinity -- which style is implementation-defined. A
16447 double argument representing a NaN is converted in one of the styles
16448 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
16449 any n-char-sequence, is implementation-defined. The F conversion specifier
16450 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
16452 </pre>
16453 e,E A double argument representing a floating-point number is converted in the
16454 <pre>
16455 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
16456 argument is nonzero) before the decimal-point character and the number of
16457 digits after it is equal to the precision; if the precision is missing, it is taken as
16458 </pre>
16461 <!--page 331 -->
16462 <pre>
16463 6; if the precision is zero and the # flag is not specified, no decimal-point
16464 character appears. The value is rounded to the appropriate number of digits.
16465 The E conversion specifier produces a number with E instead of e
16466 introducing the exponent. The exponent always contains at least two digits,
16467 and only as many more digits as necessary to represent the exponent. If the
16468 value is zero, the exponent is zero.
16469 A double argument representing an infinity or NaN is converted in the style
16470 of an f or F conversion specifier.
16471 </pre>
16472 g,G A double argument representing a floating-point number is converted in
16473 <pre>
16474 style f or e (or in style F or E in the case of a G conversion specifier),
16475 depending on the value converted and the precision. Let P equal the
16476 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
16477 Then, if a conversion with style E would have an exponent of X:
16478 -- if P > X >= -4, the conversion is with style f (or F) and precision
16479 P - (X + 1).
16480 -- otherwise, the conversion is with style e (or E) and precision P - 1.
16481 Finally, unless the # flag is used, any trailing zeros are removed from the
16482 fractional portion of the result and the decimal-point character is removed if
16483 there is no fractional portion remaining.
16484 A double argument representing an infinity or NaN is converted in the style
16485 of an f or F conversion specifier.
16486 </pre>
16487 a,A A double argument representing a floating-point number is converted in the
16488 <pre>
16489 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
16490 nonzero if the argument is a normalized floating-point number and is
16491 otherwise unspecified) before the decimal-point character<sup><a href="#note278"><b>278)</b></a></sup> and the number
16492 of hexadecimal digits after it is equal to the precision; if the precision is
16493 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
16494 an exact representation of the value; if the precision is missing and
16495 FLT_RADIX is not a power of 2, then the precision is sufficient to
16496 </pre>
16501 <!--page 332 -->
16502 <pre>
16503 distinguish<sup><a href="#note279"><b>279)</b></a></sup> values of type double, except that trailing zeros may be
16504 omitted; if the precision is zero and the # flag is not specified, no decimal-
16505 point character appears. The letters abcdef are used for a conversion and
16506 the letters ABCDEF for A conversion. The A conversion specifier produces a
16507 number with X and P instead of x and p. The exponent always contains at
16508 least one digit, and only as many more digits as necessary to represent the
16509 decimal exponent of 2. If the value is zero, the exponent is zero.
16510 A double argument representing an infinity or NaN is converted in the style
16511 of an f or F conversion specifier.
16512 </pre>
16513 c If no l length modifier is present, the int argument is converted to an
16514 <pre>
16515 unsigned char, and the resulting character is written.
16516 If an l length modifier is present, the wint_t argument is converted as if by
16517 an ls conversion specification with no precision and an argument that points
16518 to the initial element of a two-element array of wchar_t, the first element
16519 containing the wint_t argument to the lc conversion specification and the
16520 second a null wide character.
16521 </pre>
16522 s If no l length modifier is present, the argument shall be a pointer to the initial
16523 <pre>
16524 element of an array of character type.<sup><a href="#note280"><b>280)</b></a></sup> Characters from the array are
16525 written up to (but not including) the terminating null character. If the
16526 precision is specified, no more than that many bytes are written. If the
16527 precision is not specified or is greater than the size of the array, the array shall
16528 contain a null character.
16529 If an l length modifier is present, the argument shall be a pointer to the initial
16530 element of an array of wchar_t type. Wide characters from the array are
16531 converted to multibyte characters (each as if by a call to the wcrtomb
16532 function, with the conversion state described by an mbstate_t object
16533 initialized to zero before the first wide character is converted) up to and
16534 including a terminating null wide character. The resulting multibyte
16535 characters are written up to (but not including) the terminating null character
16536 (byte). If no precision is specified, the array shall contain a null wide
16537 character. If a precision is specified, no more than that many bytes are
16538 written (including shift sequences, if any), and the array shall contain a null
16539 wide character if, to equal the multibyte character sequence length given by
16540 </pre>
16542 <!--page 333 -->
16543 <pre>
16544 the precision, the function would need to access a wide character one past the
16545 end of the array. In no case is a partial multibyte character written.<sup><a href="#note281"><b>281)</b></a></sup>
16546 </pre>
16547 p The argument shall be a pointer to void. The value of the pointer is
16548 <pre>
16549 converted to a sequence of printing characters, in an implementation-defined
16550 manner.
16551 </pre>
16552 n The argument shall be a pointer to signed integer into which is written the
16553 <pre>
16554 number of characters written to the output stream so far by this call to
16555 fprintf. No argument is converted, but one is consumed. If the conversion
16556 specification includes any flags, a field width, or a precision, the behavior is
16557 undefined.
16558 </pre>
16559 % A % character is written. No argument is converted. The complete
16560 <pre>
16561 conversion specification shall be %%.
16562 </pre>
16563 <p><!--para 9 -->
16564 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note282"><b>282)</b></a></sup> If any argument is
16565 not the correct type for the corresponding conversion specification, the behavior is
16566 undefined.
16567 <p><!--para 10 -->
16568 In no case does a nonexistent or small field width cause truncation of a field; if the result
16569 of a conversion is wider than the field width, the field is expanded to contain the
16570 conversion result.
16571 <p><!--para 11 -->
16572 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
16573 to a hexadecimal floating number with the given precision.
16574 <p><b>Recommended practice</b>
16575 <p><!--para 12 -->
16576 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
16577 representable in the given precision, the result should be one of the two adjacent numbers
16578 in hexadecimal floating style with the given precision, with the extra stipulation that the
16579 error should have a correct sign for the current rounding direction.
16580 <p><!--para 13 -->
16581 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
16582 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note283"><b>283)</b></a></sup> If the number of
16583 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
16584 representable with DECIMAL_DIG digits, then the result should be an exact
16585 representation with trailing zeros. Otherwise, the source value is bounded by two
16586 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
16589 <!--page 334 -->
16590 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
16591 the error should have a correct sign for the current rounding direction.
16592 <p><b>Returns</b>
16593 <p><!--para 14 -->
16594 The fprintf function returns the number of characters transmitted, or a negative value
16595 if an output or encoding error occurred.
16596 <p><b>Environmental limits</b>
16597 <p><!--para 15 -->
16598 The number of characters that can be produced by any single conversion shall be at least
16599 4095.
16600 <p><!--para 16 -->
16601 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
16602 places:
16603 <pre>
16606 /* ... */
16607 char *weekday, *month; // pointers to strings
16608 int day, hour, min;
16610 weekday, month, day, hour, min);
16612 </pre>
16614 <p><!--para 17 -->
16615 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
16616 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
16617 the first of which is denoted here by a and the second by an uppercase letter.
16618 <p><!--para 18 -->
16619 Given the following wide string with length seven,
16620 <pre>
16622 </pre>
16623 the seven calls
16624 <pre>
16632 </pre>
16633 will print the following seven lines:
16634 <pre>
16635 |1234567890123|
16636 | X Yabc Z W|
16637 | X Yabc Z |
16638 | X Yabc Z|
16639 | X Yabc Z W|
16640 | abc Z W|
16641 | Z|
16642 </pre>
16644 <p><b> Forward references</b>: conversion state (<a href="#7.29.6">7.29.6</a>), the wcrtomb function (<a href="#7.29.6.3.3">7.29.6.3.3</a>).
16645 <!--page 335 -->
16647 <p><b>Footnotes</b>
16648 <p><small><a name="note275" href="#note275">275)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
16649 </small>
16650 <p><small><a name="note276" href="#note276">276)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
16651 include a minus sign.
16652 </small>
16653 <p><small><a name="note277" href="#note277">277)</a> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
16654 the # and 0 flag characters have no effect.
16655 </small>
16656 <p><small><a name="note278" href="#note278">278)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
16657 that subsequent digits align to nibble (4-bit) boundaries.
16658 </small>
16659 <p><small><a name="note279" href="#note279">279)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
16660 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
16661 might suffice depending on the implementation's scheme for determining the digit to the left of the
16662 decimal-point character.
16663 </small>
16664 <p><small><a name="note280" href="#note280">280)</a> No special provisions are made for multibyte characters.
16665 </small>
16666 <p><small><a name="note281" href="#note281">281)</a> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
16667 </small>
16668 <p><small><a name="note282" href="#note282">282)</a> See ''future library directions'' (<a href="#7.31.11">7.31.11</a>).
16669 </small>
16670 <p><small><a name="note283" href="#note283">283)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
16671 given format specifier. The number of significant digits is determined by the format specifier, and in
16672 the case of fixed-point conversion by the source value as well.
16673 </small>
16677 <p><b>Synopsis</b>
16678 <p><!--para 1 -->
16679 <pre>
16681 int fscanf(FILE * restrict stream,
16682 const char * restrict format, ...);
16683 </pre>
16684 <p><b>Description</b>
16685 <p><!--para 2 -->
16686 The fscanf function reads input from the stream pointed to by stream, under control
16687 of the string pointed to by format that specifies the admissible input sequences and how
16688 they are to be converted for assignment, using subsequent arguments as pointers to the
16689 objects to receive the converted input. If there are insufficient arguments for the format,
16690 the behavior is undefined. If the format is exhausted while arguments remain, the excess
16691 arguments are evaluated (as always) but are otherwise ignored.
16692 <p><!--para 3 -->
16693 The format shall be a multibyte character sequence, beginning and ending in its initial
16694 shift state. The format is composed of zero or more directives: one or more white-space
16695 characters, an ordinary multibyte character (neither % nor a white-space character), or a
16696 conversion specification. Each conversion specification is introduced by the character %.
16697 After the %, the following appear in sequence:
16698 <ul>
16699 <li> An optional assignment-suppressing character *.
16700 <li> An optional decimal integer greater than zero that specifies the maximum field width
16701 (in characters).
16702 <li> An optional length modifier that specifies the size of the receiving object.
16703 <li> A conversion specifier character that specifies the type of conversion to be applied.
16704 </ul>
16705 <p><!--para 4 -->
16706 The fscanf function executes each directive of the format in turn. When all directives
16707 have been executed, or if a directive fails (as detailed below), the function returns.
16708 Failures are described as input failures (due to the occurrence of an encoding error or the
16709 unavailability of input characters), or matching failures (due to inappropriate input).
16710 <p><!--para 5 -->
16711 A directive composed of white-space character(s) is executed by reading input up to the
16712 first non-white-space character (which remains unread), or until no more characters can
16713 be read. The directive never fails.
16714 <p><!--para 6 -->
16715 A directive that is an ordinary multibyte character is executed by reading the next
16716 characters of the stream. If any of those characters differ from the ones composing the
16717 directive, the directive fails and the differing and subsequent characters remain unread.
16718 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
16719 read, the directive fails.
16720 <p><!--para 7 -->
16721 A directive that is a conversion specification defines a set of matching input sequences, as
16722 described below for each specifier. A conversion specification is executed in the
16723 <!--page 336 -->
16724 following steps:
16725 <p><!--para 8 -->
16726 Input white-space characters (as specified by the isspace function) are skipped, unless
16727 the specification includes a [, c, or n specifier.<sup><a href="#note284"><b>284)</b></a></sup>
16728 <p><!--para 9 -->
16729 An input item is read from the stream, unless the specification includes an n specifier. An
16730 input item is defined as the longest sequence of input characters which does not exceed
16731 any specified field width and which is, or is a prefix of, a matching input sequence.<sup><a href="#note285"><b>285)</b></a></sup>
16732 The first character, if any, after the input item remains unread. If the length of the input
16733 item is zero, the execution of the directive fails; this condition is a matching failure unless
16734 end-of-file, an encoding error, or a read error prevented input from the stream, in which
16735 case it is an input failure.
16736 <p><!--para 10 -->
16737 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
16738 count of input characters) is converted to a type appropriate to the conversion specifier. If
16739 the input item is not a matching sequence, the execution of the directive fails: this
16740 condition is a matching failure. Unless assignment suppression was indicated by a *, the
16741 result of the conversion is placed in the object pointed to by the first argument following
16742 the format argument that has not already received a conversion result. If this object
16743 does not have an appropriate type, or if the result of the conversion cannot be represented
16744 in the object, the behavior is undefined.
16745 <p><!--para 11 -->
16746 The length modifiers and their meanings are:
16747 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16748 <pre>
16749 to an argument with type pointer to signed char or unsigned char.
16750 </pre>
16751 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16752 <pre>
16753 to an argument with type pointer to short int or unsigned short
16754 int.
16755 </pre>
16756 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16757 <pre>
16758 to an argument with type pointer to long int or unsigned long
16759 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
16760 an argument with type pointer to double; or that a following c, s, or [
16761 conversion specifier applies to an argument with type pointer to wchar_t.
16762 </pre>
16763 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16764 <pre>
16765 to an argument with type pointer to long long int or unsigned
16766 long long int.
16767 </pre>
16771 <!--page 337 -->
16772 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16773 <pre>
16774 to an argument with type pointer to intmax_t or uintmax_t.
16775 </pre>
16776 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16777 <pre>
16778 to an argument with type pointer to size_t or the corresponding signed
16779 integer type.
16780 </pre>
16781 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16782 <pre>
16783 to an argument with type pointer to ptrdiff_t or the corresponding
16784 unsigned integer type.
16785 </pre>
16786 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16787 <pre>
16788 applies to an argument with type pointer to long double.
16789 </pre>
16790 If a length modifier appears with any conversion specifier other than as specified above,
16791 the behavior is undefined.
16792 <p><!--para 12 -->
16793 The conversion specifiers and their meanings are:
16794 d Matches an optionally signed decimal integer, whose format is the same as
16795 <pre>
16796 expected for the subject sequence of the strtol function with the value 10
16797 for the base argument. The corresponding argument shall be a pointer to
16798 signed integer.
16799 </pre>
16800 i Matches an optionally signed integer, whose format is the same as expected
16801 <pre>
16802 for the subject sequence of the strtol function with the value 0 for the
16803 base argument. The corresponding argument shall be a pointer to signed
16804 integer.
16805 </pre>
16806 o Matches an optionally signed octal integer, whose format is the same as
16807 <pre>
16808 expected for the subject sequence of the strtoul function with the value 8
16809 for the base argument. The corresponding argument shall be a pointer to
16810 unsigned integer.
16811 </pre>
16812 u Matches an optionally signed decimal integer, whose format is the same as
16813 <pre>
16814 expected for the subject sequence of the strtoul function with the value 10
16815 for the base argument. The corresponding argument shall be a pointer to
16816 unsigned integer.
16817 </pre>
16818 x Matches an optionally signed hexadecimal integer, whose format is the same
16819 <pre>
16820 as expected for the subject sequence of the strtoul function with the value
16821 16 for the base argument. The corresponding argument shall be a pointer to
16822 unsigned integer.
16823 </pre>
16824 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
16825 <!--page 338 -->
16826 <pre>
16827 format is the same as expected for the subject sequence of the strtod
16828 function. The corresponding argument shall be a pointer to floating.
16829 </pre>
16830 c Matches a sequence of characters of exactly the number specified by the field
16831 <pre>
16832 width (1 if no field width is present in the directive).<sup><a href="#note286"><b>286)</b></a></sup>
16833 If no l length modifier is present, the corresponding argument shall be a
16834 pointer to the initial element of a character array large enough to accept the
16835 sequence. No null character is added.
16836 If an l length modifier is present, the input shall be a sequence of multibyte
16837 characters that begins in the initial shift state. Each multibyte character in the
16838 sequence is converted to a wide character as if by a call to the mbrtowc
16839 function, with the conversion state described by an mbstate_t object
16840 initialized to zero before the first multibyte character is converted. The
16841 corresponding argument shall be a pointer to the initial element of an array of
16842 wchar_t large enough to accept the resulting sequence of wide characters.
16843 No null wide character is added.
16844 </pre>
16845 s Matches a sequence of non-white-space characters.<sup><a href="#note286"><b>286)</b></a></sup>
16846 <pre>
16847 If no l length modifier is present, the corresponding argument shall be a
16848 pointer to the initial element of a character array large enough to accept the
16849 sequence and a terminating null character, which will be added automatically.
16850 If an l length modifier is present, the input shall be a sequence of multibyte
16851 characters that begins in the initial shift state. Each multibyte character is
16852 converted to a wide character as if by a call to the mbrtowc function, with
16853 the conversion state described by an mbstate_t object initialized to zero
16854 before the first multibyte character is converted. The corresponding argument
16855 shall be a pointer to the initial element of an array of wchar_t large enough
16856 to accept the sequence and the terminating null wide character, which will be
16857 added automatically.
16858 </pre>
16859 [ Matches a nonempty sequence of characters from a set of expected characters
16860 <pre>
16862 If no l length modifier is present, the corresponding argument shall be a
16863 pointer to the initial element of a character array large enough to accept the
16864 sequence and a terminating null character, which will be added automatically.
16865 If an l length modifier is present, the input shall be a sequence of multibyte
16866 characters that begins in the initial shift state. Each multibyte character is
16867 converted to a wide character as if by a call to the mbrtowc function, with
16868 the conversion state described by an mbstate_t object initialized to zero
16869 </pre>
16871 <!--page 339 -->
16872 <pre>
16873 before the first multibyte character is converted. The corresponding argument
16874 shall be a pointer to the initial element of an array of wchar_t large enough
16875 to accept the sequence and the terminating null wide character, which will be
16876 added automatically.
16877 The conversion specifier includes all subsequent characters in the format
16878 string, up to and including the matching right bracket (]). The characters
16879 between the brackets (the scanlist) compose the scanset, unless the character
16880 after the left bracket is a circumflex (^), in which case the scanset contains all
16881 characters that do not appear in the scanlist between the circumflex and the
16882 right bracket. If the conversion specifier begins with [] or [^], the right
16883 bracket character is in the scanlist and the next following right bracket
16884 character is the matching right bracket that ends the specification; otherwise
16885 the first following right bracket character is the one that ends the
16886 specification. If a - character is in the scanlist and is not the first, nor the
16887 second where the first character is a ^, nor the last character, the behavior is
16888 implementation-defined.
16889 </pre>
16890 p Matches an implementation-defined set of sequences, which should be the
16891 <pre>
16892 same as the set of sequences that may be produced by the %p conversion of
16893 the fprintf function. The corresponding argument shall be a pointer to a
16894 pointer to void. The input item is converted to a pointer value in an
16895 implementation-defined manner. If the input item is a value converted earlier
16896 during the same program execution, the pointer that results shall compare
16897 equal to that value; otherwise the behavior of the %p conversion is undefined.
16898 </pre>
16899 n No input is consumed. The corresponding argument shall be a pointer to
16900 <pre>
16901 signed integer into which is to be written the number of characters read from
16902 the input stream so far by this call to the fscanf function. Execution of a
16903 %n directive does not increment the assignment count returned at the
16904 completion of execution of the fscanf function. No argument is converted,
16905 but one is consumed. If the conversion specification includes an assignment-
16906 suppressing character or a field width, the behavior is undefined.
16907 </pre>
16908 % Matches a single % character; no conversion or assignment occurs. The
16909 <pre>
16910 complete conversion specification shall be %%.
16911 </pre>
16912 <p><!--para 13 -->
16913 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note287"><b>287)</b></a></sup>
16914 <p><!--para 14 -->
16915 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
16916 respectively, a, e, f, g, and x.
16920 <!--page 340 -->
16921 <p><!--para 15 -->
16922 Trailing white space (including new-line characters) is left unread unless matched by a
16923 directive. The success of literal matches and suppressed assignments is not directly
16924 determinable other than via the %n directive.
16925 <p><b>Returns</b>
16926 <p><!--para 16 -->
16927 The fscanf function returns the value of the macro EOF if an input failure occurs
16928 before the first conversion (if any) has completed. Otherwise, the function returns the
16929 number of input items assigned, which can be fewer than provided for, or even zero, in
16930 the event of an early matching failure.
16931 <p><!--para 17 -->
16932 EXAMPLE 1 The call:
16933 <pre>
16935 /* ... */
16936 int n, i; float x; char name[50];
16938 </pre>
16939 with the input line:
16940 <pre>
16941 25 54.32E-1 thompson
16942 </pre>
16943 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
16944 thompson\0.
16946 <p><!--para 18 -->
16947 EXAMPLE 2 The call:
16948 <pre>
16950 /* ... */
16951 int i; float x; char name[50];
16953 </pre>
16954 with input:
16955 <pre>
16956 56789 0123 56a72
16957 </pre>
16958 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
16959 sequence 56\0. The next character read from the input stream will be a.
16961 <p><!--para 19 -->
16962 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
16963 <pre>
16965 /* ... */
16966 int count; float quant; char units[21], item[21];
16967 do {
16970 } while (!feof(stdin) && !ferror(stdin));
16971 </pre>
16972 <p><!--para 20 -->
16973 If the stdin stream contains the following lines:
16974 <!--page 341 -->
16975 <pre>
16976 2 quarts of oil
16977 -12.8degrees Celsius
16978 lots of luck
16979 10.0LBS of
16980 dirt
16981 100ergs of energy
16982 </pre>
16983 the execution of the above example will be analogous to the following assignments:
16984 <pre>
16986 count = 3;
16991 count = 3;
16993 count = EOF;
16994 </pre>
16996 <p><!--para 21 -->
16997 EXAMPLE 4 In:
16998 <pre>
17000 /* ... */
17001 int d1, d2, n1, n2, i;
17003 </pre>
17004 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure, the value
17005 of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
17007 <p><!--para 22 -->
17008 EXAMPLE 5 The call:
17009 <pre>
17011 /* ... */
17012 int n, i;
17014 </pre>
17015 will assign to n the value 1 and to i the value 42 because input white-space characters are skipped for both
17016 the % and d conversion specifiers.
17018 <p><!--para 23 -->
17019 EXAMPLE 6 In these examples, multibyte characters do have a state-dependent encoding, and the
17020 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
17021 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
17022 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
17023 entry into the alternate shift state.
17024 <p><!--para 24 -->
17025 After the call:
17026 <pre>
17028 /* ... */
17029 char str[50];
17031 </pre>
17032 with the input line:
17033 <pre>
17034 a(uparrow) X Y(downarrow) bc
17035 </pre>
17036 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
17037 characters, in the more general case) appears to be a single-byte white-space character.
17038 <p><!--para 25 -->
17039 In contrast, after the call:
17040 <!--page 342 -->
17041 <pre>
17044 /* ... */
17045 wchar_t wstr[50];
17047 </pre>
17048 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
17049 terminating null wide character.
17050 <p><!--para 26 -->
17051 However, the call:
17052 <pre>
17055 /* ... */
17056 wchar_t wstr[50];
17058 </pre>
17059 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
17060 string.
17061 <p><!--para 27 -->
17062 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
17063 character Y, after the call:
17064 <pre>
17067 /* ... */
17068 wchar_t wstr[50];
17070 </pre>
17071 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
17072 multibyte character.
17074 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>), the
17075 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.22.1.4">7.22.1.4</a>), conversion state
17078 <p><b>Footnotes</b>
17079 <p><small><a name="note284" href="#note284">284)</a> These white-space characters are not counted against a specified field width.
17080 </small>
17081 <p><small><a name="note285" href="#note285">285)</a> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
17082 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
17083 </small>
17084 <p><small><a name="note286" href="#note286">286)</a> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
17085 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
17086 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
17087 </small>
17088 <p><small><a name="note287" href="#note287">287)</a> See ''future library directions'' (<a href="#7.31.11">7.31.11</a>).
17089 </small>
17093 <p><b>Synopsis</b>
17094 <p><!--para 1 -->
17095 <pre>
17097 int printf(const char * restrict format, ...);
17098 </pre>
17099 <p><b>Description</b>
17100 <p><!--para 2 -->
17101 The printf function is equivalent to fprintf with the argument stdout interposed
17102 before the arguments to printf.
17103 <p><b>Returns</b>
17104 <p><!--para 3 -->
17105 The printf function returns the number of characters transmitted, or a negative value if
17106 an output or encoding error occurred.
17107 <!--page 343 -->
17111 <p><b>Synopsis</b>
17112 <p><!--para 1 -->
17113 <pre>
17115 int scanf(const char * restrict format, ...);
17116 </pre>
17117 <p><b>Description</b>
17118 <p><!--para 2 -->
17119 The scanf function is equivalent to fscanf with the argument stdin interposed
17120 before the arguments to scanf.
17121 <p><b>Returns</b>
17122 <p><!--para 3 -->
17123 The scanf function returns the value of the macro EOF if an input failure occurs before
17124 the first conversion (if any) has completed. Otherwise, the scanf function returns the
17125 number of input items assigned, which can be fewer than provided for, or even zero, in
17126 the event of an early matching failure.
17130 <p><b>Synopsis</b>
17131 <p><!--para 1 -->
17132 <pre>
17134 int snprintf(char * restrict s, size_t n,
17135 const char * restrict format, ...);
17136 </pre>
17137 <p><b>Description</b>
17138 <p><!--para 2 -->
17139 The snprintf function is equivalent to fprintf, except that the output is written into
17140 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
17141 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
17142 discarded rather than being written to the array, and a null character is written at the end
17143 of the characters actually written into the array. If copying takes place between objects
17144 that overlap, the behavior is undefined.
17145 <p><b>Returns</b>
17146 <p><!--para 3 -->
17147 The snprintf function returns the number of characters that would have been written
17148 had n been sufficiently large, not counting the terminating null character, or a negative
17149 value if an encoding error occurred. Thus, the null-terminated output has been
17150 completely written if and only if the returned value is nonnegative and less than n.
17154 <p><b>Synopsis</b>
17155 <p><!--para 1 -->
17156 <!--page 344 -->
17157 <pre>
17159 int sprintf(char * restrict s,
17160 const char * restrict format, ...);
17161 </pre>
17162 <p><b>Description</b>
17163 <p><!--para 2 -->
17164 The sprintf function is equivalent to fprintf, except that the output is written into
17165 an array (specified by the argument s) rather than to a stream. A null character is written
17166 at the end of the characters written; it is not counted as part of the returned value. If
17167 copying takes place between objects that overlap, the behavior is undefined.
17168 <p><b>Returns</b>
17169 <p><!--para 3 -->
17170 The sprintf function returns the number of characters written in the array, not
17171 counting the terminating null character, or a negative value if an encoding error occurred.
17175 <p><b>Synopsis</b>
17176 <p><!--para 1 -->
17177 <pre>
17179 int sscanf(const char * restrict s,
17180 const char * restrict format, ...);
17181 </pre>
17182 <p><b>Description</b>
17183 <p><!--para 2 -->
17184 The sscanf function is equivalent to fscanf, except that input is obtained from a
17185 string (specified by the argument s) rather than from a stream. Reaching the end of the
17186 string is equivalent to encountering end-of-file for the fscanf function. If copying
17187 takes place between objects that overlap, the behavior is undefined.
17188 <p><b>Returns</b>
17189 <p><!--para 3 -->
17190 The sscanf function returns the value of the macro EOF if an input failure occurs
17191 before the first conversion (if any) has completed. Otherwise, the sscanf function
17192 returns the number of input items assigned, which can be fewer than provided for, or even
17193 zero, in the event of an early matching failure.
17197 <p><b>Synopsis</b>
17198 <p><!--para 1 -->
17199 <pre>
17202 int vfprintf(FILE * restrict stream,
17203 const char * restrict format,
17204 va_list arg);
17205 </pre>
17206 <p><b>Description</b>
17207 <p><!--para 2 -->
17208 The vfprintf function is equivalent to fprintf, with the variable argument list
17209 replaced by arg, which shall have been initialized by the va_start macro (and
17210 possibly subsequent va_arg calls). The vfprintf function does not invoke the
17211 <!--page 345 -->
17213 <p><b>Returns</b>
17214 <p><!--para 3 -->
17215 The vfprintf function returns the number of characters transmitted, or a negative
17216 value if an output or encoding error occurred.
17217 <p><!--para 4 -->
17218 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
17219 <pre>
17222 void error(char *function_name, char *format, ...)
17223 {
17224 va_list args;
17225 va_start(args, format);
17226 // print out name of function causing error
17228 // print out remainder of message
17229 vfprintf(stderr, format, args);
17230 va_end(args);
17231 }
17232 </pre>
17235 <p><b>Footnotes</b>
17236 <p><small><a name="note288" href="#note288">288)</a> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
17237 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
17238 </small>
17242 <p><b>Synopsis</b>
17243 <p><!--para 1 -->
17244 <pre>
17247 int vfscanf(FILE * restrict stream,
17248 const char * restrict format,
17249 va_list arg);
17250 </pre>
17251 <p><b>Description</b>
17252 <p><!--para 2 -->
17253 The vfscanf function is equivalent to fscanf, with the variable argument list
17254 replaced by arg, which shall have been initialized by the va_start macro (and
17255 possibly subsequent va_arg calls). The vfscanf function does not invoke the
17257 <p><b>Returns</b>
17258 <p><!--para 3 -->
17259 The vfscanf function returns the value of the macro EOF if an input failure occurs
17260 before the first conversion (if any) has completed. Otherwise, the vfscanf function
17261 returns the number of input items assigned, which can be fewer than provided for, or even
17262 zero, in the event of an early matching failure.
17266 <!--page 346 -->
17270 <p><b>Synopsis</b>
17271 <p><!--para 1 -->
17272 <pre>
17275 int vprintf(const char * restrict format,
17276 va_list arg);
17277 </pre>
17278 <p><b>Description</b>
17279 <p><!--para 2 -->
17280 The vprintf function is equivalent to printf, with the variable argument list
17281 replaced by arg, which shall have been initialized by the va_start macro (and
17282 possibly subsequent va_arg calls). The vprintf function does not invoke the
17284 <p><b>Returns</b>
17285 <p><!--para 3 -->
17286 The vprintf function returns the number of characters transmitted, or a negative value
17287 if an output or encoding error occurred.
17291 <p><b>Synopsis</b>
17292 <p><!--para 1 -->
17293 <pre>
17296 int vscanf(const char * restrict format,
17297 va_list arg);
17298 </pre>
17299 <p><b>Description</b>
17300 <p><!--para 2 -->
17301 The vscanf function is equivalent to scanf, with the variable argument list replaced
17302 by arg, which shall have been initialized by the va_start macro (and possibly
17303 subsequent va_arg calls). The vscanf function does not invoke the va_end
17305 <p><b>Returns</b>
17306 <p><!--para 3 -->
17307 The vscanf function returns the value of the macro EOF if an input failure occurs
17308 before the first conversion (if any) has completed. Otherwise, the vscanf function
17309 returns the number of input items assigned, which can be fewer than provided for, or even
17310 zero, in the event of an early matching failure.
17311 <!--page 347 -->
17315 <p><b>Synopsis</b>
17316 <p><!--para 1 -->
17317 <pre>
17320 int vsnprintf(char * restrict s, size_t n,
17321 const char * restrict format,
17322 va_list arg);
17323 </pre>
17324 <p><b>Description</b>
17325 <p><!--para 2 -->
17326 The vsnprintf function is equivalent to snprintf, with the variable argument list
17327 replaced by arg, which shall have been initialized by the va_start macro (and
17328 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
17329 va_end macro.<sup><a href="#note288"><b>288)</b></a></sup> If copying takes place between objects that overlap, the behavior is
17330 undefined.
17331 <p><b>Returns</b>
17332 <p><!--para 3 -->
17333 The vsnprintf function returns the number of characters that would have been written
17334 had n been sufficiently large, not counting the terminating null character, or a negative
17335 value if an encoding error occurred. Thus, the null-terminated output has been
17336 completely written if and only if the returned value is nonnegative and less than n.
17340 <p><b>Synopsis</b>
17341 <p><!--para 1 -->
17342 <pre>
17345 int vsprintf(char * restrict s,
17346 const char * restrict format,
17347 va_list arg);
17348 </pre>
17349 <p><b>Description</b>
17350 <p><!--para 2 -->
17351 The vsprintf function is equivalent to sprintf, with the variable argument list
17352 replaced by arg, which shall have been initialized by the va_start macro (and
17353 possibly subsequent va_arg calls). The vsprintf function does not invoke the
17354 va_end macro.<sup><a href="#note288"><b>288)</b></a></sup> If copying takes place between objects that overlap, the behavior is
17355 undefined.
17356 <p><b>Returns</b>
17357 <p><!--para 3 -->
17358 The vsprintf function returns the number of characters written in the array, not
17359 counting the terminating null character, or a negative value if an encoding error occurred.
17360 <!--page 348 -->
17364 <p><b>Synopsis</b>
17365 <p><!--para 1 -->
17366 <pre>
17369 int vsscanf(const char * restrict s,
17370 const char * restrict format,
17371 va_list arg);
17372 </pre>
17373 <p><b>Description</b>
17374 <p><!--para 2 -->
17375 The vsscanf function is equivalent to sscanf, with the variable argument list
17376 replaced by arg, which shall have been initialized by the va_start macro (and
17377 possibly subsequent va_arg calls). The vsscanf function does not invoke the
17379 <p><b>Returns</b>
17380 <p><!--para 3 -->
17381 The vsscanf function returns the value of the macro EOF if an input failure occurs
17382 before the first conversion (if any) has completed. Otherwise, the vsscanf function
17383 returns the number of input items assigned, which can be fewer than provided for, or even
17384 zero, in the event of an early matching failure.
17391 <p><b>Synopsis</b>
17392 <p><!--para 1 -->
17393 <pre>
17395 int fgetc(FILE *stream);
17396 </pre>
17397 <p><b>Description</b>
17398 <p><!--para 2 -->
17399 If the end-of-file indicator for the input stream pointed to by stream is not set and a
17400 next character is present, the fgetc function obtains that character as an unsigned
17401 char converted to an int and advances the associated file position indicator for the
17402 stream (if defined).
17403 <p><b>Returns</b>
17404 <p><!--para 3 -->
17405 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
17406 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
17407 fgetc function returns the next character from the input stream pointed to by stream.
17408 If a read error occurs, the error indicator for the stream is set and the fgetc function
17412 <!--page 349 -->
17414 <p><b>Footnotes</b>
17415 <p><small><a name="note289" href="#note289">289)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
17416 </small>
17420 <p><b>Synopsis</b>
17421 <p><!--para 1 -->
17422 <pre>
17424 char *fgets(char * restrict s, int n,
17425 FILE * restrict stream);
17426 </pre>
17427 <p><b>Description</b>
17428 <p><!--para 2 -->
17429 The fgets function reads at most one less than the number of characters specified by n
17430 from the stream pointed to by stream into the array pointed to by s. No additional
17431 characters are read after a new-line character (which is retained) or after end-of-file. A
17432 null character is written immediately after the last character read into the array.
17433 <p><b>Returns</b>
17434 <p><!--para 3 -->
17435 The fgets function returns s if successful. If end-of-file is encountered and no
17436 characters have been read into the array, the contents of the array remain unchanged and a
17437 null pointer is returned. If a read error occurs during the operation, the array contents are
17438 indeterminate and a null pointer is returned.
17442 <p><b>Synopsis</b>
17443 <p><!--para 1 -->
17444 <pre>
17446 int fputc(int c, FILE *stream);
17447 </pre>
17448 <p><b>Description</b>
17449 <p><!--para 2 -->
17450 The fputc function writes the character specified by c (converted to an unsigned
17451 char) to the output stream pointed to by stream, at the position indicated by the
17452 associated file position indicator for the stream (if defined), and advances the indicator
17453 appropriately. If the file cannot support positioning requests, or if the stream was opened
17454 with append mode, the character is appended to the output stream.
17455 <p><b>Returns</b>
17456 <p><!--para 3 -->
17457 The fputc function returns the character written. If a write error occurs, the error
17458 indicator for the stream is set and fputc returns EOF.
17462 <p><b>Synopsis</b>
17463 <p><!--para 1 -->
17464 <!--page 350 -->
17465 <pre>
17467 int fputs(const char * restrict s,
17468 FILE * restrict stream);
17469 </pre>
17470 <p><b>Description</b>
17471 <p><!--para 2 -->
17472 The fputs function writes the string pointed to by s to the stream pointed to by
17473 stream. The terminating null character is not written.
17474 <p><b>Returns</b>
17475 <p><!--para 3 -->
17476 The fputs function returns EOF if a write error occurs; otherwise it returns a
17477 nonnegative value.
17481 <p><b>Synopsis</b>
17482 <p><!--para 1 -->
17483 <pre>
17485 int getc(FILE *stream);
17486 </pre>
17487 <p><b>Description</b>
17488 <p><!--para 2 -->
17489 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
17490 may evaluate stream more than once, so the argument should never be an expression
17491 with side effects.
17492 <p><b>Returns</b>
17493 <p><!--para 3 -->
17494 The getc function returns the next character from the input stream pointed to by
17495 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
17496 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
17497 getc returns EOF.
17501 <p><b>Synopsis</b>
17502 <p><!--para 1 -->
17503 <pre>
17505 int getchar(void);
17506 </pre>
17507 <p><b>Description</b>
17508 <p><!--para 2 -->
17509 The getchar function is equivalent to getc with the argument stdin.
17510 <p><b>Returns</b>
17511 <p><!--para 3 -->
17512 The getchar function returns the next character from the input stream pointed to by
17513 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
17514 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
17515 getchar returns EOF.
17516 <!--page 351 -->
17520 <p><b>Synopsis</b>
17521 <p><!--para 1 -->
17522 <pre>
17524 int putc(int c, FILE *stream);
17525 </pre>
17526 <p><b>Description</b>
17527 <p><!--para 2 -->
17528 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
17529 may evaluate stream more than once, so that argument should never be an expression
17530 with side effects.
17531 <p><b>Returns</b>
17532 <p><!--para 3 -->
17533 The putc function returns the character written. If a write error occurs, the error
17534 indicator for the stream is set and putc returns EOF.
17538 <p><b>Synopsis</b>
17539 <p><!--para 1 -->
17540 <pre>
17542 int putchar(int c);
17543 </pre>
17544 <p><b>Description</b>
17545 <p><!--para 2 -->
17546 The putchar function is equivalent to putc with the second argument stdout.
17547 <p><b>Returns</b>
17548 <p><!--para 3 -->
17549 The putchar function returns the character written. If a write error occurs, the error
17550 indicator for the stream is set and putchar returns EOF.
17554 <p><b>Synopsis</b>
17555 <p><!--para 1 -->
17556 <pre>
17558 int puts(const char *s);
17559 </pre>
17560 <p><b>Description</b>
17561 <p><!--para 2 -->
17562 The puts function writes the string pointed to by s to the stream pointed to by stdout,
17563 and appends a new-line character to the output. The terminating null character is not
17564 written.
17565 <p><b>Returns</b>
17566 <p><!--para 3 -->
17567 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
17568 value.
17569 <!--page 352 -->
17573 <p><b>Synopsis</b>
17574 <p><!--para 1 -->
17575 <pre>
17577 int ungetc(int c, FILE *stream);
17578 </pre>
17579 <p><b>Description</b>
17580 <p><!--para 2 -->
17581 The ungetc function pushes the character specified by c (converted to an unsigned
17582 char) back onto the input stream pointed to by stream. Pushed-back characters will be
17583 returned by subsequent reads on that stream in the reverse order of their pushing. A
17584 successful intervening call (with the stream pointed to by stream) to a file positioning
17585 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
17586 stream. The external storage corresponding to the stream is unchanged.
17587 <p><!--para 3 -->
17588 One character of pushback is guaranteed. If the ungetc function is called too many
17589 times on the same stream without an intervening read or file positioning operation on that
17590 stream, the operation may fail.
17591 <p><!--para 4 -->
17592 If the value of c equals that of the macro EOF, the operation fails and the input stream is
17593 unchanged.
17594 <p><!--para 5 -->
17595 A successful call to the ungetc function clears the end-of-file indicator for the stream.
17596 The value of the file position indicator for the stream after reading or discarding all
17597 pushed-back characters shall be the same as it was before the characters were pushed
17598 back. For a text stream, the value of its file position indicator after a successful call to the
17599 ungetc function is unspecified until all pushed-back characters are read or discarded.
17600 For a binary stream, its file position indicator is decremented by each successful call to
17601 the ungetc function; if its value was zero before a call, it is indeterminate after the
17603 <p><b>Returns</b>
17604 <p><!--para 6 -->
17605 The ungetc function returns the character pushed back after conversion, or EOF if the
17606 operation fails.
17612 <!--page 353 -->
17614 <p><b>Footnotes</b>
17615 <p><small><a name="note290" href="#note290">290)</a> See ''future library directions'' (<a href="#7.31.11">7.31.11</a>).
17616 </small>
17623 <p><b>Synopsis</b>
17624 <p><!--para 1 -->
17625 <pre>
17627 size_t fread(void * restrict ptr,
17628 size_t size, size_t nmemb,
17629 FILE * restrict stream);
17630 </pre>
17631 <p><b>Description</b>
17632 <p><!--para 2 -->
17633 The fread function reads, into the array pointed to by ptr, up to nmemb elements
17634 whose size is specified by size, from the stream pointed to by stream. For each
17635 object, size calls are made to the fgetc function and the results stored, in the order
17636 read, in an array of unsigned char exactly overlaying the object. The file position
17637 indicator for the stream (if defined) is advanced by the number of characters successfully
17638 read. If an error occurs, the resulting value of the file position indicator for the stream is
17639 indeterminate. If a partial element is read, its value is indeterminate.
17640 <p><b>Returns</b>
17641 <p><!--para 3 -->
17642 The fread function returns the number of elements successfully read, which may be
17643 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
17644 fread returns zero and the contents of the array and the state of the stream remain
17645 unchanged.
17649 <p><b>Synopsis</b>
17650 <p><!--para 1 -->
17651 <pre>
17653 size_t fwrite(const void * restrict ptr,
17654 size_t size, size_t nmemb,
17655 FILE * restrict stream);
17656 </pre>
17657 <p><b>Description</b>
17658 <p><!--para 2 -->
17659 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
17660 whose size is specified by size, to the stream pointed to by stream. For each object,
17661 size calls are made to the fputc function, taking the values (in order) from an array of
17662 unsigned char exactly overlaying the object. The file position indicator for the
17663 stream (if defined) is advanced by the number of characters successfully written. If an
17664 error occurs, the resulting value of the file position indicator for the stream is
17665 indeterminate.
17666 <!--page 354 -->
17667 <p><b>Returns</b>
17668 <p><!--para 3 -->
17669 The fwrite function returns the number of elements successfully written, which will be
17670 less than nmemb only if a write error is encountered. If size or nmemb is zero,
17671 fwrite returns zero and the state of the stream remains unchanged.
17678 <p><b>Synopsis</b>
17679 <p><!--para 1 -->
17680 <pre>
17682 int fgetpos(FILE * restrict stream,
17683 fpos_t * restrict pos);
17684 </pre>
17685 <p><b>Description</b>
17686 <p><!--para 2 -->
17687 The fgetpos function stores the current values of the parse state (if any) and file
17688 position indicator for the stream pointed to by stream in the object pointed to by pos.
17689 The values stored contain unspecified information usable by the fsetpos function for
17690 repositioning the stream to its position at the time of the call to the fgetpos function.
17691 <p><b>Returns</b>
17692 <p><!--para 3 -->
17693 If successful, the fgetpos function returns zero; on failure, the fgetpos function
17694 returns nonzero and stores an implementation-defined positive value in errno.
17699 <p><b>Synopsis</b>
17700 <p><!--para 1 -->
17701 <pre>
17703 int fseek(FILE *stream, long int offset, int whence);
17704 </pre>
17705 <p><b>Description</b>
17706 <p><!--para 2 -->
17707 The fseek function sets the file position indicator for the stream pointed to by stream.
17708 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
17709 <p><!--para 3 -->
17710 For a binary stream, the new position, measured in characters from the beginning of the
17711 file, is obtained by adding offset to the position specified by whence. The specified
17712 position is the beginning of the file if whence is SEEK_SET, the current value of the file
17713 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
17714 meaningfully support fseek calls with a whence value of SEEK_END.
17715 <p><!--para 4 -->
17716 For a text stream, either offset shall be zero, or offset shall be a value returned by
17717 an earlier successful call to the ftell function on a stream associated with the same file
17718 and whence shall be SEEK_SET.
17719 <!--page 355 -->
17720 <p><!--para 5 -->
17721 After determining the new position, a successful call to the fseek function undoes any
17722 effects of the ungetc function on the stream, clears the end-of-file indicator for the
17723 stream, and then establishes the new position. After a successful fseek call, the next
17724 operation on an update stream may be either input or output.
17725 <p><b>Returns</b>
17726 <p><!--para 6 -->
17727 The fseek function returns nonzero only for a request that cannot be satisfied.
17732 <p><b>Synopsis</b>
17733 <p><!--para 1 -->
17734 <pre>
17736 int fsetpos(FILE *stream, const fpos_t *pos);
17737 </pre>
17738 <p><b>Description</b>
17739 <p><!--para 2 -->
17740 The fsetpos function sets the mbstate_t object (if any) and file position indicator
17741 for the stream pointed to by stream according to the value of the object pointed to by
17742 pos, which shall be a value obtained from an earlier successful call to the fgetpos
17743 function on a stream associated with the same file. If a read or write error occurs, the
17744 error indicator for the stream is set and fsetpos fails.
17745 <p><!--para 3 -->
17746 A successful call to the fsetpos function undoes any effects of the ungetc function
17747 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
17748 parse state and position. After a successful fsetpos call, the next operation on an
17749 update stream may be either input or output.
17750 <p><b>Returns</b>
17751 <p><!--para 4 -->
17752 If successful, the fsetpos function returns zero; on failure, the fsetpos function
17753 returns nonzero and stores an implementation-defined positive value in errno.
17757 <p><b>Synopsis</b>
17758 <p><!--para 1 -->
17759 <pre>
17761 long int ftell(FILE *stream);
17762 </pre>
17763 <p><b>Description</b>
17764 <p><!--para 2 -->
17765 The ftell function obtains the current value of the file position indicator for the stream
17766 pointed to by stream. For a binary stream, the value is the number of characters from
17767 the beginning of the file. For a text stream, its file position indicator contains unspecified
17768 information, usable by the fseek function for returning the file position indicator for the
17769 stream to its position at the time of the ftell call; the difference between two such
17770 return values is not necessarily a meaningful measure of the number of characters written
17771 <!--page 356 -->
17772 or read.
17773 <p><b>Returns</b>
17774 <p><!--para 3 -->
17775 If successful, the ftell function returns the current value of the file position indicator
17776 for the stream. On failure, the ftell function returns -1L and stores an
17777 implementation-defined positive value in errno.
17781 <p><b>Synopsis</b>
17782 <p><!--para 1 -->
17783 <pre>
17785 void rewind(FILE *stream);
17786 </pre>
17787 <p><b>Description</b>
17788 <p><!--para 2 -->
17789 The rewind function sets the file position indicator for the stream pointed to by
17790 stream to the beginning of the file. It is equivalent to
17791 <pre>
17792 (void)fseek(stream, 0L, SEEK_SET)
17793 </pre>
17794 except that the error indicator for the stream is also cleared.
17795 <p><b>Returns</b>
17796 <p><!--para 3 -->
17797 The rewind function returns no value.
17804 <p><b>Synopsis</b>
17805 <p><!--para 1 -->
17806 <pre>
17808 void clearerr(FILE *stream);
17809 </pre>
17810 <p><b>Description</b>
17811 <p><!--para 2 -->
17812 The clearerr function clears the end-of-file and error indicators for the stream pointed
17813 to by stream.
17814 <p><b>Returns</b>
17815 <p><!--para 3 -->
17816 The clearerr function returns no value.
17817 <!--page 357 -->
17821 <p><b>Synopsis</b>
17822 <p><!--para 1 -->
17823 <pre>
17825 int feof(FILE *stream);
17826 </pre>
17827 <p><b>Description</b>
17828 <p><!--para 2 -->
17829 The feof function tests the end-of-file indicator for the stream pointed to by stream.
17830 <p><b>Returns</b>
17831 <p><!--para 3 -->
17832 The feof function returns nonzero if and only if the end-of-file indicator is set for
17833 stream.
17837 <p><b>Synopsis</b>
17838 <p><!--para 1 -->
17839 <pre>
17841 int ferror(FILE *stream);
17842 </pre>
17843 <p><b>Description</b>
17844 <p><!--para 2 -->
17845 The ferror function tests the error indicator for the stream pointed to by stream.
17846 <p><b>Returns</b>
17847 <p><!--para 3 -->
17848 The ferror function returns nonzero if and only if the error indicator is set for
17849 stream.
17853 <p><b>Synopsis</b>
17854 <p><!--para 1 -->
17855 <pre>
17857 void perror(const char *s);
17858 </pre>
17859 <p><b>Description</b>
17860 <p><!--para 2 -->
17861 The perror function maps the error number in the integer expression errno to an
17862 error message. It writes a sequence of characters to the standard error stream thus: first
17863 (if s is not a null pointer and the character pointed to by s is not the null character), the
17864 string pointed to by s followed by a colon (:) and a space; then an appropriate error
17865 message string followed by a new-line character. The contents of the error message
17866 strings are the same as those returned by the strerror function with argument errno.
17867 <p><b>Returns</b>
17868 <p><!--para 3 -->
17869 The perror function returns no value.
17871 <!--page 358 -->
17875 <p><!--para 1 -->
17876 The header <a href="#7.22"><stdlib.h></a> declares five types and several functions of general utility, and
17878 <p><!--para 2 -->
17880 <pre>
17881 div_t
17882 </pre>
17883 which is a structure type that is the type of the value returned by the div function,
17884 <pre>
17885 ldiv_t
17886 </pre>
17887 which is a structure type that is the type of the value returned by the ldiv function, and
17888 <pre>
17889 lldiv_t
17890 </pre>
17891 which is a structure type that is the type of the value returned by the lldiv function.
17892 <p><!--para 3 -->
17894 <pre>
17895 EXIT_FAILURE
17896 </pre>
17897 and
17898 <pre>
17899 EXIT_SUCCESS
17900 </pre>
17901 which expand to integer constant expressions that can be used as the argument to the
17902 exit function to return unsuccessful or successful termination status, respectively, to the
17903 host environment;
17904 <pre>
17905 RAND_MAX
17906 </pre>
17907 which expands to an integer constant expression that is the maximum value returned by
17908 the rand function; and
17909 <pre>
17910 MB_CUR_MAX
17911 </pre>
17912 which expands to a positive integer expression with type size_t that is the maximum
17913 number of bytes in a multibyte character for the extended character set specified by the
17914 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
17919 <!--page 359 -->
17921 <p><b>Footnotes</b>
17922 <p><small><a name="note291" href="#note291">291)</a> See ''future library directions'' (<a href="#7.31.12">7.31.12</a>).
17923 </small>
17927 <p><!--para 1 -->
17928 The functions atof, atoi, atol, and atoll need not affect the value of the integer
17929 expression errno on an error. If the value of the result cannot be represented, the
17930 behavior is undefined.
17934 <p><b>Synopsis</b>
17935 <p><!--para 1 -->
17936 <pre>
17938 double atof(const char *nptr);
17939 </pre>
17940 <p><b>Description</b>
17941 <p><!--para 2 -->
17942 The atof function converts the initial portion of the string pointed to by nptr to
17943 double representation. Except for the behavior on error, it is equivalent to
17944 <pre>
17945 strtod(nptr, (char **)NULL)
17946 </pre>
17947 <p><b>Returns</b>
17948 <p><!--para 3 -->
17949 The atof function returns the converted value.
17950 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
17954 <p><b>Synopsis</b>
17955 <p><!--para 1 -->
17956 <pre>
17958 int atoi(const char *nptr);
17959 long int atol(const char *nptr);
17960 long long int atoll(const char *nptr);
17961 </pre>
17962 <p><b>Description</b>
17963 <p><!--para 2 -->
17964 The atoi, atol, and atoll functions convert the initial portion of the string pointed
17965 to by nptr to int, long int, and long long int representation, respectively.
17966 Except for the behavior on error, they are equivalent to
17967 <pre>
17968 atoi: (int)strtol(nptr, (char **)NULL, 10)
17969 atol: strtol(nptr, (char **)NULL, 10)
17970 atoll: strtoll(nptr, (char **)NULL, 10)
17971 </pre>
17972 <p><b>Returns</b>
17973 <p><!--para 3 -->
17974 The atoi, atol, and atoll functions return the converted value.
17975 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
17977 <!--page 360 -->
17980 <h5><a name="7.22.1.3" href="#7.22.1.3">7.22.1.3 The strtod, strtof, and strtold functions</a></h5>
17981 <p><b>Synopsis</b>
17982 <p><!--para 1 -->
17983 <pre>
17985 double strtod(const char * restrict nptr,
17986 char ** restrict endptr);
17987 float strtof(const char * restrict nptr,
17988 char ** restrict endptr);
17989 long double strtold(const char * restrict nptr,
17990 char ** restrict endptr);
17991 </pre>
17992 <p><b>Description</b>
17993 <p><!--para 2 -->
17994 The strtod, strtof, and strtold functions convert the initial portion of the string
17995 pointed to by nptr to double, float, and long double representation,
17996 respectively. First, they decompose the input string into three parts: an initial, possibly
17997 empty, sequence of white-space characters (as specified by the isspace function), a
17998 subject sequence resembling a floating-point constant or representing an infinity or NaN;
17999 and a final string of one or more unrecognized characters, including the terminating null
18000 character of the input string. Then, they attempt to convert the subject sequence to a
18001 floating-point number, and return the result.
18002 <p><!--para 3 -->
18003 The expected form of the subject sequence is an optional plus or minus sign, then one of
18004 the following:
18005 <ul>
18006 <li> a nonempty sequence of decimal digits optionally containing a decimal-point
18008 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
18009 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
18010 <li> INF or INFINITY, ignoring case
18011 <li> NAN or NAN(n-char-sequence<sub>opt</sub>), ignoring case in the NAN part, where:
18012 <pre>
18013 n-char-sequence:
18014 digit
18015 nondigit
18016 n-char-sequence digit
18017 n-char-sequence nondigit
18018 </pre>
18019 </ul>
18020 The subject sequence is defined as the longest initial subsequence of the input string,
18021 starting with the first non-white-space character, that is of the expected form. The subject
18022 sequence contains no characters if the input string is not of the expected form.
18023 <p><!--para 4 -->
18024 If the subject sequence has the expected form for a floating-point number, the sequence of
18025 characters starting with the first digit or the decimal-point character (whichever occurs
18026 first) is interpreted as a floating constant according to the rules of <a href="#6.4.4.2">6.4.4.2</a>, except that the
18027 <!--page 361 -->
18028 decimal-point character is used in place of a period, and that if neither an exponent part
18029 nor a decimal-point character appears in a decimal floating point number, or if a binary
18030 exponent part does not appear in a hexadecimal floating point number, an exponent part
18031 of the appropriate type with value zero is assumed to follow the last digit in the string. If
18032 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note292"><b>292)</b></a></sup>
18033 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
18034 the return type, else like a floating constant that is too large for the range of the return
18035 type. A character sequence NAN or NAN(n-char-sequence<sub>opt</sub>) is interpreted as a quiet
18036 NaN, if supported in the return type, else like a subject sequence part that does not have
18037 the expected form; the meaning of the n-char sequence is implementation-defined.<sup><a href="#note293"><b>293)</b></a></sup> A
18038 pointer to the final string is stored in the object pointed to by endptr, provided that
18039 endptr is not a null pointer.
18040 <p><!--para 5 -->
18041 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
18042 value resulting from the conversion is correctly rounded.
18043 <p><!--para 6 -->
18045 accepted.
18046 <p><!--para 7 -->
18047 If the subject sequence is empty or does not have the expected form, no conversion is
18048 performed; the value of nptr is stored in the object pointed to by endptr, provided
18049 that endptr is not a null pointer.
18050 <p><b>Recommended practice</b>
18051 <p><!--para 8 -->
18052 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
18053 the result is not exactly representable, the result should be one of the two numbers in the
18054 appropriate internal format that are adjacent to the hexadecimal floating source value,
18055 with the extra stipulation that the error should have a correct sign for the current rounding
18056 direction.
18057 <p><!--para 9 -->
18058 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
18059 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
18060 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
18061 consider the two bounding, adjacent decimal strings L and U, both having
18062 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
18063 The result should be one of the (equal or adjacent) values that would be obtained by
18064 correctly rounding L and U according to the current rounding direction, with the extra
18066 <!--page 362 -->
18067 stipulation that the error with respect to D should have a correct sign for the current
18069 <p><b>Returns</b>
18070 <p><!--para 10 -->
18071 The functions return the converted value, if any. If no conversion could be performed,
18072 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
18073 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
18074 return type and sign of the value), and the value of the macro ERANGE is stored in
18075 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
18076 no greater than the smallest normalized positive number in the return type; whether
18077 errno acquires the value ERANGE is implementation-defined.
18079 <p><b>Footnotes</b>
18080 <p><small><a name="note292" href="#note292">292)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
18081 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
18082 methods may yield different results if rounding is toward positive or negative infinity. In either case,
18083 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
18084 </small>
18085 <p><small><a name="note293" href="#note293">293)</a> An implementation may use the n-char sequence to determine extra information to be represented in
18086 the NaN's significand.
18087 </small>
18088 <p><small><a name="note294" href="#note294">294)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
18089 to the same internal floating value, but if not will round to adjacent values.
18090 </small>
18093 <h5><a name="7.22.1.4" href="#7.22.1.4">7.22.1.4 The strtol, strtoll, strtoul, and strtoull functions</a></h5>
18094 <p><b>Synopsis</b>
18095 <p><!--para 1 -->
18096 <pre>
18098 long int strtol(
18099 const char * restrict nptr,
18100 char ** restrict endptr,
18101 int base);
18102 long long int strtoll(
18103 const char * restrict nptr,
18104 char ** restrict endptr,
18105 int base);
18106 unsigned long int strtoul(
18107 const char * restrict nptr,
18108 char ** restrict endptr,
18109 int base);
18110 unsigned long long int strtoull(
18111 const char * restrict nptr,
18112 char ** restrict endptr,
18113 int base);
18114 </pre>
18115 <p><b>Description</b>
18116 <p><!--para 2 -->
18117 The strtol, strtoll, strtoul, and strtoull functions convert the initial
18118 portion of the string pointed to by nptr to long int, long long int, unsigned
18119 long int, and unsigned long long int representation, respectively. First,
18120 they decompose the input string into three parts: an initial, possibly empty, sequence of
18121 white-space characters (as specified by the isspace function), a subject sequence
18124 <!--page 363 -->
18125 resembling an integer represented in some radix determined by the value of base, and a
18126 final string of one or more unrecognized characters, including the terminating null
18127 character of the input string. Then, they attempt to convert the subject sequence to an
18128 integer, and return the result.
18129 <p><!--para 3 -->
18130 If the value of base is zero, the expected form of the subject sequence is that of an
18131 integer constant as described in <a href="#6.4.4.1">6.4.4.1</a>, optionally preceded by a plus or minus sign, but
18132 not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
18133 expected form of the subject sequence is a sequence of letters and digits representing an
18134 integer with the radix specified by base, optionally preceded by a plus or minus sign,
18135 but not including an integer suffix. The letters from a (or A) through z (or Z) are
18136 ascribed the values 10 through 35; only letters and digits whose ascribed values are less
18137 than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
18138 optionally precede the sequence of letters and digits, following the sign if present.
18139 <p><!--para 4 -->
18140 The subject sequence is defined as the longest initial subsequence of the input string,
18141 starting with the first non-white-space character, that is of the expected form. The subject
18142 sequence contains no characters if the input string is empty or consists entirely of white
18143 space, or if the first non-white-space character is other than a sign or a permissible letter
18144 or digit.
18145 <p><!--para 5 -->
18146 If the subject sequence has the expected form and the value of base is zero, the sequence
18147 of characters starting with the first digit is interpreted as an integer constant according to
18148 the rules of <a href="#6.4.4.1">6.4.4.1</a>. If the subject sequence has the expected form and the value of base
18149 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
18150 as given above. If the subject sequence begins with a minus sign, the value resulting from
18151 the conversion is negated (in the return type). A pointer to the final string is stored in the
18152 object pointed to by endptr, provided that endptr is not a null pointer.
18153 <p><!--para 6 -->
18155 accepted.
18156 <p><!--para 7 -->
18157 If the subject sequence is empty or does not have the expected form, no conversion is
18158 performed; the value of nptr is stored in the object pointed to by endptr, provided
18159 that endptr is not a null pointer.
18160 <p><b>Returns</b>
18161 <p><!--para 8 -->
18162 The strtol, strtoll, strtoul, and strtoull functions return the converted
18163 value, if any. If no conversion could be performed, zero is returned. If the correct value
18164 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
18165 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
18166 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
18167 <!--page 364 -->
18170 <h4><a name="7.22.2" href="#7.22.2">7.22.2 Pseudo-random sequence generation functions</a></h4>
18174 <p><b>Synopsis</b>
18175 <p><!--para 1 -->
18176 <pre>
18178 int rand(void);
18179 </pre>
18180 <p><b>Description</b>
18181 <p><!--para 2 -->
18182 The rand function computes a sequence of pseudo-random integers in the range 0 to
18184 <p><!--para 3 -->
18185 The rand function is not required to avoid data races with other calls to pseudo-random
18186 sequence generation functions. The implementation shall behave as if no library function
18187 calls the rand function.
18188 <p><b>Returns</b>
18189 <p><!--para 4 -->
18190 The rand function returns a pseudo-random integer.
18191 <p><b>Environmental limits</b>
18192 <p><!--para 5 -->
18193 The value of the RAND_MAX macro shall be at least 32767.
18195 <p><b>Footnotes</b>
18196 <p><small><a name="note295" href="#note295">295)</a> There are no guarantees as to the quality of the random sequence produced and some implementations
18197 are known to produce sequences with distressingly non-random low-order bits. Applications with
18198 particular requirements should use a generator that is known to be sufficient for their needs.
18199 </small>
18203 <p><b>Synopsis</b>
18204 <p><!--para 1 -->
18205 <pre>
18207 void srand(unsigned int seed);
18208 </pre>
18209 <p><b>Description</b>
18210 <p><!--para 2 -->
18211 The srand function uses the argument as a seed for a new sequence of pseudo-random
18212 numbers to be returned by subsequent calls to rand. If srand is then called with the
18213 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
18214 called before any calls to srand have been made, the same sequence shall be generated
18215 as when srand is first called with a seed value of 1.
18216 <p><!--para 3 -->
18217 The srand function is not required to avoid data races with other calls to pseudo-
18218 random sequence generation functions. The implementation shall behave as if no library
18219 function calls the srand function.
18224 <!--page 365 -->
18225 <p><b>Returns</b>
18226 <p><!--para 4 -->
18227 The srand function returns no value.
18228 <p><!--para 5 -->
18229 EXAMPLE The following functions define a portable implementation of rand and srand.
18230 <pre>
18231 static unsigned long int next = 1;
18232 int rand(void) // RAND_MAX assumed to be 32767
18233 {
18234 next = next * 1103515245 + 12345;
18235 return (unsigned int)(next/65536) % 32768;
18236 }
18237 void srand(unsigned int seed)
18238 {
18239 next = seed;
18240 }
18241 </pre>
18246 <p><!--para 1 -->
18247 The order and contiguity of storage allocated by successive calls to the
18248 aligned_alloc, calloc, malloc, and realloc functions is unspecified. The
18249 pointer returned if the allocation succeeds is suitably aligned so that it may be assigned to
18250 a pointer to any type of object with a fundamental alignment requirement and then used
18251 to access such an object or an array of such objects in the space allocated (until the space
18252 is explicitly deallocated). The lifetime of an allocated object extends from the allocation
18253 until the deallocation. Each such allocation shall yield a pointer to an object disjoint from
18254 any other object. The pointer returned points to the start (lowest byte address) of the
18255 allocated space. If the space cannot be allocated, a null pointer is returned. If the size of
18256 the space requested is zero, the behavior is implementation-defined: either a null pointer
18257 is returned, or the behavior is as if the size were some nonzero value, except that the
18258 returned pointer shall not be used to access an object.
18259 <p><!--para 2 -->
18260 For purposes of determining the existence of a data race, memory allocation functions
18261 behave as though they accessed only memory locations accessible through their
18262 arguments and not other static duration storage. These functions may, however, visibly
18263 modify the storage that they allocate or deallocate. A call to free or realloc that
18264 deallocates a region p of memory synchronizes with any allocation call that allocates all
18265 or part of the region p. This synchronization occurs after any access of p by the
18266 deallocating function, and before any such access by the allocating function.
18270 <p><b>Synopsis</b>
18271 <p><!--para 1 -->
18272 <!--page 366 -->
18273 <pre>
18275 void *aligned_alloc(size_t alignment, size_t size);
18276 </pre>
18277 <p><b>Description</b>
18278 <p><!--para 2 -->
18279 The aligned_alloc function allocates space for an object whose alignment is
18280 specified by alignment, whose size is specified by size, and whose value is
18281 indeterminate. The value of alignment shall be a valid alignment supported by the
18282 implementation and the value of size shall be an integral multiple of alignment.
18283 <p><b>Returns</b>
18284 <p><!--para 3 -->
18285 The aligned_alloc function returns either a null pointer or a pointer to the allocated
18286 space.
18290 <p><b>Synopsis</b>
18291 <p><!--para 1 -->
18292 <pre>
18294 void *calloc(size_t nmemb, size_t size);
18295 </pre>
18296 <p><b>Description</b>
18297 <p><!--para 2 -->
18298 The calloc function allocates space for an array of nmemb objects, each of whose size
18299 is size. The space is initialized to all bits zero.<sup><a href="#note296"><b>296)</b></a></sup>
18300 <p><b>Returns</b>
18301 <p><!--para 3 -->
18302 The calloc function returns either a null pointer or a pointer to the allocated space.
18304 <p><b>Footnotes</b>
18305 <p><small><a name="note296" href="#note296">296)</a> Note that this need not be the same as the representation of floating-point zero or a null pointer
18306 constant.
18307 </small>
18311 <p><b>Synopsis</b>
18312 <p><!--para 1 -->
18313 <pre>
18315 void free(void *ptr);
18316 </pre>
18317 <p><b>Description</b>
18318 <p><!--para 2 -->
18319 The free function causes the space pointed to by ptr to be deallocated, that is, made
18320 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
18321 the argument does not match a pointer earlier returned by a memory management
18322 function, or if the space has been deallocated by a call to free or realloc, the
18323 behavior is undefined.
18324 <p><b>Returns</b>
18325 <p><!--para 3 -->
18326 The free function returns no value.
18331 <!--page 367 -->
18335 <p><b>Synopsis</b>
18336 <p><!--para 1 -->
18337 <pre>
18339 void *malloc(size_t size);
18340 </pre>
18341 <p><b>Description</b>
18342 <p><!--para 2 -->
18343 The malloc function allocates space for an object whose size is specified by size and
18344 whose value is indeterminate.
18345 <p><b>Returns</b>
18346 <p><!--para 3 -->
18347 The malloc function returns either a null pointer or a pointer to the allocated space.
18351 <p><b>Synopsis</b>
18352 <p><!--para 1 -->
18353 <pre>
18355 void *realloc(void *ptr, size_t size);
18356 </pre>
18357 <p><b>Description</b>
18358 <p><!--para 2 -->
18359 The realloc function deallocates the old object pointed to by ptr and returns a
18360 pointer to a new object that has the size specified by size. The contents of the new
18361 object shall be the same as that of the old object prior to deallocation, up to the lesser of
18362 the new and old sizes. Any bytes in the new object beyond the size of the old object have
18363 indeterminate values.
18364 <p><!--para 3 -->
18365 If ptr is a null pointer, the realloc function behaves like the malloc function for the
18366 specified size. Otherwise, if ptr does not match a pointer earlier returned by a memory
18367 management function, or if the space has been deallocated by a call to the free or
18368 realloc function, the behavior is undefined. If memory for the new object cannot be
18369 allocated, the old object is not deallocated and its value is unchanged.
18370 <p><b>Returns</b>
18371 <p><!--para 4 -->
18372 The realloc function returns a pointer to the new object (which may have the same
18373 value as a pointer to the old object), or a null pointer if the new object could not be
18374 allocated.
18375 <!--page 368 -->
18382 <p><b>Synopsis</b>
18383 <p><!--para 1 -->
18384 <pre>
18386 _Noreturn void abort(void);
18387 </pre>
18388 <p><b>Description</b>
18389 <p><!--para 2 -->
18390 The abort function causes abnormal program termination to occur, unless the signal
18391 SIGABRT is being caught and the signal handler does not return. Whether open streams
18392 with unwritten buffered data are flushed, open streams are closed, or temporary files are
18393 removed is implementation-defined. An implementation-defined form of the status
18394 unsuccessful termination is returned to the host environment by means of the function
18395 call raise(SIGABRT).
18396 <p><b>Returns</b>
18397 <p><!--para 3 -->
18398 The abort function does not return to its caller.
18402 <p><b>Synopsis</b>
18403 <p><!--para 1 -->
18404 <pre>
18406 int atexit(void (*func)(void));
18407 </pre>
18408 <p><b>Description</b>
18409 <p><!--para 2 -->
18410 The atexit function registers the function pointed to by func, to be called without
18411 arguments at normal program termination.<sup><a href="#note297"><b>297)</b></a></sup> It is unspecified whether a call to the
18412 atexit function that does not happen before the exit function is called will succeed.
18413 <p><b>Environmental limits</b>
18414 <p><!--para 3 -->
18415 The implementation shall support the registration of at least 32 functions.
18416 <p><b>Returns</b>
18417 <p><!--para 4 -->
18418 The atexit function returns zero if the registration succeeds, nonzero if it fails.
18419 <p><b> Forward references</b>: the at_quick_exit function (<a href="#7.22.4.3">7.22.4.3</a>), the exit function
18425 <!--page 369 -->
18427 <p><b>Footnotes</b>
18428 <p><small><a name="note297" href="#note297">297)</a> The atexit function registrations are distinct from the at_quick_exit registrations, so
18429 applications may need to call both registration functions with the same argument.
18430 </small>
18434 <p><b>Synopsis</b>
18435 <p><!--para 1 -->
18436 <pre>
18438 int at_quick_exit(void (*func)(void));
18439 </pre>
18440 <p><b>Description</b>
18441 <p><!--para 2 -->
18442 The at_quick_exit function registers the function pointed to by func, to be called
18443 without arguments should quick_exit be called.<sup><a href="#note298"><b>298)</b></a></sup> It is unspecified whether a call to
18444 the at_quick_exit function that does not happen before the quick_exit function
18445 is called will succeed.
18446 <p><b>Environmental limits</b>
18447 <p><!--para 3 -->
18448 The implementation shall support the registration of at least 32 functions.
18449 <p><b>Returns</b>
18450 <p><!--para 4 -->
18451 The at_quick_exit function returns zero if the registration succeeds, nonzero if it
18452 fails.
18455 <p><b>Footnotes</b>
18456 <p><small><a name="note298" href="#note298">298)</a> The at_quick_exit function registrations are distinct from the atexit registrations, so
18457 applications may need to call both registration functions with the same argument.
18458 </small>
18462 <p><b>Synopsis</b>
18463 <p><!--para 1 -->
18464 <pre>
18466 _Noreturn void exit(int status);
18467 </pre>
18468 <p><b>Description</b>
18469 <p><!--para 2 -->
18470 The exit function causes normal program termination to occur. No functions registered
18471 by the at_quick_exit function are called. If a program calls the exit function
18472 more than once, or calls the quick_exit function in addition to the exit function, the
18473 behavior is undefined.
18474 <p><!--para 3 -->
18475 First, all functions registered by the atexit function are called, in the reverse order of
18476 their registration,<sup><a href="#note299"><b>299)</b></a></sup> except that a function is called after any previously registered
18477 functions that had already been called at the time it was registered. If, during the call to
18478 any such function, a call to the longjmp function is made that would terminate the call
18479 to the registered function, the behavior is undefined.
18483 <!--page 370 -->
18484 <p><!--para 4 -->
18485 Next, all open streams with unwritten buffered data are flushed, all open streams are
18486 closed, and all files created by the tmpfile function are removed.
18487 <p><!--para 5 -->
18488 Finally, control is returned to the host environment. If the value of status is zero or
18489 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
18490 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
18491 of the status unsuccessful termination is returned. Otherwise the status returned is
18492 implementation-defined.
18493 <p><b>Returns</b>
18494 <p><!--para 6 -->
18495 The exit function cannot return to its caller.
18497 <p><b>Footnotes</b>
18498 <p><small><a name="note299" href="#note299">299)</a> Each function is called as many times as it was registered, and in the correct order with respect to
18499 other registered functions.
18500 </small>
18504 <p><b>Synopsis</b>
18505 <p><!--para 1 -->
18506 <pre>
18508 _Noreturn void _Exit(int status);
18509 </pre>
18510 <p><b>Description</b>
18511 <p><!--para 2 -->
18512 The _Exit function causes normal program termination to occur and control to be
18513 returned to the host environment. No functions registered by the atexit function, the
18514 at_quick_exit function, or signal handlers registered by the signal function are
18515 called. The status returned to the host environment is determined in the same way as for
18516 the exit function (<a href="#7.22.4.4">7.22.4.4</a>). Whether open streams with unwritten buffered data are
18517 flushed, open streams are closed, or temporary files are removed is implementation-
18518 defined.
18519 <p><b>Returns</b>
18520 <p><!--para 3 -->
18521 The _Exit function cannot return to its caller.
18525 <p><b>Synopsis</b>
18526 <p><!--para 1 -->
18527 <pre>
18529 char *getenv(const char *name);
18530 </pre>
18531 <p><b>Description</b>
18532 <p><!--para 2 -->
18533 The getenv function searches an environment list, provided by the host environment,
18534 for a string that matches the string pointed to by name. The set of environment names
18535 and the method for altering the environment list are implementation-defined. The
18536 getenv function need not avoid data races with other threads of execution that modify
18539 <!--page 371 -->
18540 <p><!--para 3 -->
18541 The implementation shall behave as if no library function calls the getenv function.
18542 <p><b>Returns</b>
18543 <p><!--para 4 -->
18544 The getenv function returns a pointer to a string associated with the matched list
18545 member. The string pointed to shall not be modified by the program, but may be
18546 overwritten by a subsequent call to the getenv function. If the specified name cannot
18547 be found, a null pointer is returned.
18549 <p><b>Footnotes</b>
18550 <p><small><a name="note300" href="#note300">300)</a> Many implementations provide non-standard functions that modify the environment list.
18551 </small>
18555 <p><b>Synopsis</b>
18556 <p><!--para 1 -->
18557 <pre>
18559 _Noreturn void quick_exit(int status);
18560 </pre>
18561 <p><b>Description</b>
18562 <p><!--para 2 -->
18563 The quick_exit function causes normal program termination to occur. No functions
18564 registered by the atexit function or signal handlers registered by the signal function
18565 are called. If a program calls the quick_exit function more than once, or calls the
18566 exit function in addition to the quick_exit function, the behavior is undefined. If a
18567 signal is raised while the quick_exit function is executing, the behavior is undefined.
18568 <p><!--para 3 -->
18569 The quick_exit function first calls all functions registered by the at_quick_exit
18570 function, in the reverse order of their registration,<sup><a href="#note301"><b>301)</b></a></sup> except that a function is called after
18571 any previously registered functions that had already been called at the time it was
18572 registered. If, during the call to any such function, a call to the longjmp function is
18573 made that would terminate the call to the registered function, the behavior is undefined.
18574 <p><!--para 4 -->
18575 Then control is returned to the host environment by means of the function call
18576 _Exit(status).
18577 <p><b>Returns</b>
18578 <p><!--para 5 -->
18579 The quick_exit function cannot return to its caller.
18581 <p><b>Footnotes</b>
18582 <p><small><a name="note301" href="#note301">301)</a> Each function is called as many times as it was registered, and in the correct order with respect to
18583 other registered functions.
18584 </small>
18588 <p><b>Synopsis</b>
18589 <p><!--para 1 -->
18590 <pre>
18592 int system(const char *string);
18593 </pre>
18594 <p><b>Description</b>
18595 <p><!--para 2 -->
18596 If string is a null pointer, the system function determines whether the host
18597 environment has a command processor. If string is not a null pointer, the system
18599 <!--page 372 -->
18600 function passes the string pointed to by string to that command processor to be
18601 executed in a manner which the implementation shall document; this might then cause the
18602 program calling system to behave in a non-conforming manner or to terminate.
18603 <p><b>Returns</b>
18604 <p><!--para 3 -->
18605 If the argument is a null pointer, the system function returns nonzero only if a
18606 command processor is available. If the argument is not a null pointer, and the system
18607 function does return, it returns an implementation-defined value.
18611 <p><!--para 1 -->
18612 These utilities make use of a comparison function to search or sort arrays of unspecified
18613 type. Where an argument declared as size_t nmemb specifies the length of the array
18614 for a function, nmemb can have the value zero on a call to that function; the comparison
18615 function is not called, a search finds no matching element, and sorting performs no
18616 rearrangement. Pointer arguments on such a call shall still have valid values, as described
18618 <p><!--para 2 -->
18619 The implementation shall ensure that the second argument of the comparison function
18620 (when called from bsearch), or both arguments (when called from qsort), are
18621 pointers to elements of the array.<sup><a href="#note302"><b>302)</b></a></sup> The first argument when called from bsearch
18622 shall equal key.
18623 <p><!--para 3 -->
18624 The comparison function shall not alter the contents of the array. The implementation
18625 may reorder elements of the array between calls to the comparison function, but shall not
18626 alter the contents of any individual element.
18627 <p><!--para 4 -->
18628 When the same objects (consisting of size bytes, irrespective of their current positions
18629 in the array) are passed more than once to the comparison function, the results shall be
18630 consistent with one another. That is, for qsort they shall define a total ordering on the
18631 array, and for bsearch the same object shall always compare the same way with the
18632 key.
18633 <p><!--para 5 -->
18634 A sequence point occurs immediately before and immediately after each call to the
18635 comparison function, and also between any call to the comparison function and any
18636 movement of the objects passed as arguments to that call.
18641 <!--page 373 -->
18643 <p><b>Footnotes</b>
18644 <p><small><a name="note302" href="#note302">302)</a> That is, if the value passed is p, then the following expressions are always nonzero:
18646 <pre>
18647 ((char *)p - (char *)base) % size == 0
18648 (char *)p >= (char *)base
18649 (char *)p < (char *)base + nmemb * size
18650 </pre>
18651 </small>
18655 <p><b>Synopsis</b>
18656 <p><!--para 1 -->
18657 <pre>
18659 void *bsearch(const void *key, const void *base,
18660 size_t nmemb, size_t size,
18661 int (*compar)(const void *, const void *));
18662 </pre>
18663 <p><b>Description</b>
18664 <p><!--para 2 -->
18665 The bsearch function searches an array of nmemb objects, the initial element of which
18666 is pointed to by base, for an element that matches the object pointed to by key. The
18667 size of each element of the array is specified by size.
18668 <p><!--para 3 -->
18669 The comparison function pointed to by compar is called with two arguments that point
18670 to the key object and to an array element, in that order. The function shall return an
18671 integer less than, equal to, or greater than zero if the key object is considered,
18672 respectively, to be less than, to match, or to be greater than the array element. The array
18673 shall consist of: all the elements that compare less than, all the elements that compare
18674 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note303"><b>303)</b></a></sup>
18675 <p><b>Returns</b>
18676 <p><!--para 4 -->
18677 The bsearch function returns a pointer to a matching element of the array, or a null
18678 pointer if no match is found. If two elements compare as equal, which element is
18679 matched is unspecified.
18681 <p><b>Footnotes</b>
18682 <p><small><a name="note303" href="#note303">303)</a> In practice, the entire array is sorted according to the comparison function.
18683 </small>
18687 <p><b>Synopsis</b>
18688 <p><!--para 1 -->
18689 <pre>
18691 void qsort(void *base, size_t nmemb, size_t size,
18692 int (*compar)(const void *, const void *));
18693 </pre>
18694 <p><b>Description</b>
18695 <p><!--para 2 -->
18696 The qsort function sorts an array of nmemb objects, the initial element of which is
18697 pointed to by base. The size of each object is specified by size.
18698 <p><!--para 3 -->
18699 The contents of the array are sorted into ascending order according to a comparison
18700 function pointed to by compar, which is called with two arguments that point to the
18701 objects being compared. The function shall return an integer less than, equal to, or
18702 greater than zero if the first argument is considered to be respectively less than, equal to,
18703 or greater than the second.
18706 <!--page 374 -->
18707 <p><!--para 4 -->
18708 If two elements compare as equal, their order in the resulting sorted array is unspecified.
18709 <p><b>Returns</b>
18710 <p><!--para 5 -->
18711 The qsort function returns no value.
18718 <p><b>Synopsis</b>
18719 <p><!--para 1 -->
18720 <pre>
18722 int abs(int j);
18723 long int labs(long int j);
18724 long long int llabs(long long int j);
18725 </pre>
18726 <p><b>Description</b>
18727 <p><!--para 2 -->
18728 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
18729 result cannot be represented, the behavior is undefined.<sup><a href="#note304"><b>304)</b></a></sup>
18730 <p><b>Returns</b>
18731 <p><!--para 3 -->
18732 The abs, labs, and llabs, functions return the absolute value.
18734 <p><b>Footnotes</b>
18735 <p><small><a name="note304" href="#note304">304)</a> The absolute value of the most negative number cannot be represented in two's complement.
18736 </small>
18740 <p><b>Synopsis</b>
18741 <p><!--para 1 -->
18742 <pre>
18744 div_t div(int numer, int denom);
18745 ldiv_t ldiv(long int numer, long int denom);
18746 lldiv_t lldiv(long long int numer, long long int denom);
18747 </pre>
18748 <p><b>Description</b>
18749 <p><!--para 2 -->
18750 The div, ldiv, and lldiv, functions compute numer / denom and numer %
18751 denom in a single operation.
18752 <p><b>Returns</b>
18753 <p><!--para 3 -->
18754 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
18755 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
18756 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
18757 each of which has the same type as the arguments numer and denom. If either part of
18758 the result cannot be represented, the behavior is undefined.
18763 <!--page 375 -->
18766 <h4><a name="7.22.7" href="#7.22.7">7.22.7 Multibyte/wide character conversion functions</a></h4>
18767 <p><!--para 1 -->
18768 The behavior of the multibyte character functions is affected by the LC_CTYPE category
18769 of the current locale. For a state-dependent encoding, each function is placed into its
18770 initial conversion state at program startup and can be returned to that state by a call for
18771 which its character pointer argument, s, is a null pointer. Subsequent calls with s as
18772 other than a null pointer cause the internal conversion state of the function to be altered as
18773 necessary. A call with s as a null pointer causes these functions to return a nonzero value
18774 if encodings have state dependency, and zero otherwise.<sup><a href="#note305"><b>305)</b></a></sup> Changing the LC_CTYPE
18775 category causes the conversion state of these functions to be indeterminate.
18777 <p><b>Footnotes</b>
18778 <p><small><a name="note305" href="#note305">305)</a> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
18779 character codes, but are grouped with an adjacent multibyte character.
18780 </small>
18784 <p><b>Synopsis</b>
18785 <p><!--para 1 -->
18786 <pre>
18788 int mblen(const char *s, size_t n);
18789 </pre>
18790 <p><b>Description</b>
18791 <p><!--para 2 -->
18792 If s is not a null pointer, the mblen function determines the number of bytes contained
18793 in the multibyte character pointed to by s. Except that the conversion state of the
18794 mbtowc function is not affected, it is equivalent to
18795 <pre>
18796 mbtowc((wchar_t *)0, (const char *)0, 0);
18797 mbtowc((wchar_t *)0, s, n);
18798 </pre>
18799 <p><!--para 3 -->
18800 The implementation shall behave as if no library function calls the mblen function.
18801 <p><b>Returns</b>
18802 <p><!--para 4 -->
18803 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
18804 character encodings, respectively, do or do not have state-dependent encodings. If s is
18805 not a null pointer, the mblen function either returns 0 (if s points to the null character),
18806 or returns the number of bytes that are contained in the multibyte character (if the next n
18807 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
18808 multibyte character).
18814 <!--page 376 -->
18818 <p><b>Synopsis</b>
18819 <p><!--para 1 -->
18820 <pre>
18822 int mbtowc(wchar_t * restrict pwc,
18823 const char * restrict s,
18824 size_t n);
18825 </pre>
18826 <p><b>Description</b>
18827 <p><!--para 2 -->
18828 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
18829 the byte pointed to by s to determine the number of bytes needed to complete the next
18830 multibyte character (including any shift sequences). If the function determines that the
18831 next multibyte character is complete and valid, it determines the value of the
18832 corresponding wide character and then, if pwc is not a null pointer, stores that value in
18833 the object pointed to by pwc. If the corresponding wide character is the null wide
18834 character, the function is left in the initial conversion state.
18835 <p><!--para 3 -->
18836 The implementation shall behave as if no library function calls the mbtowc function.
18837 <p><b>Returns</b>
18838 <p><!--para 4 -->
18839 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
18840 character encodings, respectively, do or do not have state-dependent encodings. If s is
18841 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
18842 or returns the number of bytes that are contained in the converted multibyte character (if
18843 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
18844 form a valid multibyte character).
18845 <p><!--para 5 -->
18846 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
18847 macro.
18851 <p><b>Synopsis</b>
18852 <p><!--para 1 -->
18853 <pre>
18855 int wctomb(char *s, wchar_t wc);
18856 </pre>
18857 <p><b>Description</b>
18858 <p><!--para 2 -->
18859 The wctomb function determines the number of bytes needed to represent the multibyte
18860 character corresponding to the wide character given by wc (including any shift
18861 sequences), and stores the multibyte character representation in the array whose first
18862 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
18863 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
18864 sequence needed to restore the initial shift state, and the function is left in the initial
18865 conversion state.
18866 <!--page 377 -->
18867 <p><!--para 3 -->
18868 The implementation shall behave as if no library function calls the wctomb function.
18869 <p><b>Returns</b>
18870 <p><!--para 4 -->
18871 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
18872 character encodings, respectively, do or do not have state-dependent encodings. If s is
18873 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
18874 to a valid multibyte character, or returns the number of bytes that are contained in the
18875 multibyte character corresponding to the value of wc.
18876 <p><!--para 5 -->
18877 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
18880 <h4><a name="7.22.8" href="#7.22.8">7.22.8 Multibyte/wide string conversion functions</a></h4>
18881 <p><!--para 1 -->
18882 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
18883 the current locale.
18887 <p><b>Synopsis</b>
18888 <p><!--para 1 -->
18889 <pre>
18891 size_t mbstowcs(wchar_t * restrict pwcs,
18892 const char * restrict s,
18893 size_t n);
18894 </pre>
18895 <p><b>Description</b>
18896 <p><!--para 2 -->
18897 The mbstowcs function converts a sequence of multibyte characters that begins in the
18898 initial shift state from the array pointed to by s into a sequence of corresponding wide
18899 characters and stores not more than n wide characters into the array pointed to by pwcs.
18900 No multibyte characters that follow a null character (which is converted into a null wide
18901 character) will be examined or converted. Each multibyte character is converted as if by
18902 a call to the mbtowc function, except that the conversion state of the mbtowc function is
18903 not affected.
18904 <p><!--para 3 -->
18905 No more than n elements will be modified in the array pointed to by pwcs. If copying
18906 takes place between objects that overlap, the behavior is undefined.
18907 <p><b>Returns</b>
18908 <p><!--para 4 -->
18909 If an invalid multibyte character is encountered, the mbstowcs function returns
18910 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
18911 elements modified, not including a terminating null wide character, if any.<sup><a href="#note306"><b>306)</b></a></sup>
18916 <!--page 378 -->
18918 <p><b>Footnotes</b>
18919 <p><small><a name="note306" href="#note306">306)</a> The array will not be null-terminated if the value returned is n.
18920 </small>
18924 <p><b>Synopsis</b>
18925 <p><!--para 1 -->
18926 <pre>
18928 size_t wcstombs(char * restrict s,
18929 const wchar_t * restrict pwcs,
18930 size_t n);
18931 </pre>
18932 <p><b>Description</b>
18933 <p><!--para 2 -->
18934 The wcstombs function converts a sequence of wide characters from the array pointed
18935 to by pwcs into a sequence of corresponding multibyte characters that begins in the
18936 initial shift state, and stores these multibyte characters into the array pointed to by s,
18937 stopping if a multibyte character would exceed the limit of n total bytes or if a null
18938 character is stored. Each wide character is converted as if by a call to the wctomb
18939 function, except that the conversion state of the wctomb function is not affected.
18940 <p><!--para 3 -->
18941 No more than n bytes will be modified in the array pointed to by s. If copying takes place
18942 between objects that overlap, the behavior is undefined.
18943 <p><b>Returns</b>
18944 <p><!--para 4 -->
18945 If a wide character is encountered that does not correspond to a valid multibyte character,
18946 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
18947 returns the number of bytes modified, not including a terminating null character, if
18949 <!--page 379 -->
18951 <p><!--para 1 -->
18953 <pre>
18954 noreturn
18955 </pre>
18956 which expands to _Noreturn.
18957 <!--page 380 -->
18964 <p><!--para 1 -->
18965 The header <a href="#7.24"><string.h></a> declares one type and several functions, and defines one
18966 macro useful for manipulating arrays of character type and other objects treated as arrays
18967 of character type.<sup><a href="#note307"><b>307)</b></a></sup> The type is size_t and the macro is NULL (both described in
18968 <a href="#7.19">7.19</a>). Various methods are used for determining the lengths of the arrays, but in all cases
18969 a char * or void * argument points to the initial (lowest addressed) character of the
18970 array. If an array is accessed beyond the end of an object, the behavior is undefined.
18971 <p><!--para 2 -->
18972 Where an argument declared as size_t n specifies the length of the array for a
18973 function, n can have the value zero on a call to that function. Unless explicitly stated
18974 otherwise in the description of a particular function in this subclause, pointer arguments
18975 on such a call shall still have valid values, as described in <a href="#7.1.4">7.1.4</a>. On such a call, a
18976 function that locates a character finds no occurrence, a function that compares two
18977 character sequences returns zero, and a function that copies characters copies zero
18978 characters.
18979 <p><!--para 3 -->
18980 For all functions in this subclause, each character shall be interpreted as if it had the type
18981 unsigned char (and therefore every possible object representation is valid and has a
18982 different value).
18984 <p><b>Footnotes</b>
18985 <p><small><a name="note307" href="#note307">307)</a> See ''future library directions'' (<a href="#7.31.13">7.31.13</a>).
18986 </small>
18993 <p><b>Synopsis</b>
18994 <p><!--para 1 -->
18995 <pre>
18997 void *memcpy(void * restrict s1,
18998 const void * restrict s2,
18999 size_t n);
19000 </pre>
19001 <p><b>Description</b>
19002 <p><!--para 2 -->
19003 The memcpy function copies n characters from the object pointed to by s2 into the
19004 object pointed to by s1. If copying takes place between objects that overlap, the behavior
19005 is undefined.
19006 <p><b>Returns</b>
19007 <p><!--para 3 -->
19008 The memcpy function returns the value of s1.
19013 <!--page 381 -->
19017 <p><b>Synopsis</b>
19018 <p><!--para 1 -->
19019 <pre>
19021 void *memmove(void *s1, const void *s2, size_t n);
19022 </pre>
19023 <p><b>Description</b>
19024 <p><!--para 2 -->
19025 The memmove function copies n characters from the object pointed to by s2 into the
19026 object pointed to by s1. Copying takes place as if the n characters from the object
19027 pointed to by s2 are first copied into a temporary array of n characters that does not
19028 overlap the objects pointed to by s1 and s2, and then the n characters from the
19029 temporary array are copied into the object pointed to by s1.
19030 <p><b>Returns</b>
19031 <p><!--para 3 -->
19032 The memmove function returns the value of s1.
19036 <p><b>Synopsis</b>
19037 <p><!--para 1 -->
19038 <pre>
19040 char *strcpy(char * restrict s1,
19041 const char * restrict s2);
19042 </pre>
19043 <p><b>Description</b>
19044 <p><!--para 2 -->
19045 The strcpy function copies the string pointed to by s2 (including the terminating null
19046 character) into the array pointed to by s1. If copying takes place between objects that
19047 overlap, the behavior is undefined.
19048 <p><b>Returns</b>
19049 <p><!--para 3 -->
19050 The strcpy function returns the value of s1.
19054 <p><b>Synopsis</b>
19055 <p><!--para 1 -->
19056 <pre>
19058 char *strncpy(char * restrict s1,
19059 const char * restrict s2,
19060 size_t n);
19061 </pre>
19062 <p><b>Description</b>
19063 <p><!--para 2 -->
19064 The strncpy function copies not more than n characters (characters that follow a null
19065 character are not copied) from the array pointed to by s2 to the array pointed to by
19066 <!--page 382 -->
19067 s1.<sup><a href="#note308"><b>308)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
19068 <p><!--para 3 -->
19069 If the array pointed to by s2 is a string that is shorter than n characters, null characters
19070 are appended to the copy in the array pointed to by s1, until n characters in all have been
19071 written.
19072 <p><b>Returns</b>
19073 <p><!--para 4 -->
19074 The strncpy function returns the value of s1.
19076 <p><b>Footnotes</b>
19077 <p><small><a name="note308" href="#note308">308)</a> Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
19078 not be null-terminated.
19079 </small>
19086 <p><b>Synopsis</b>
19087 <p><!--para 1 -->
19088 <pre>
19090 char *strcat(char * restrict s1,
19091 const char * restrict s2);
19092 </pre>
19093 <p><b>Description</b>
19094 <p><!--para 2 -->
19095 The strcat function appends a copy of the string pointed to by s2 (including the
19096 terminating null character) to the end of the string pointed to by s1. The initial character
19097 of s2 overwrites the null character at the end of s1. If copying takes place between
19098 objects that overlap, the behavior is undefined.
19099 <p><b>Returns</b>
19100 <p><!--para 3 -->
19101 The strcat function returns the value of s1.
19105 <p><b>Synopsis</b>
19106 <p><!--para 1 -->
19107 <pre>
19109 char *strncat(char * restrict s1,
19110 const char * restrict s2,
19111 size_t n);
19112 </pre>
19113 <p><b>Description</b>
19114 <p><!--para 2 -->
19115 The strncat function appends not more than n characters (a null character and
19116 characters that follow it are not appended) from the array pointed to by s2 to the end of
19117 the string pointed to by s1. The initial character of s2 overwrites the null character at the
19118 end of s1. A terminating null character is always appended to the result.<sup><a href="#note309"><b>309)</b></a></sup> If copying
19120 <!--page 383 -->
19121 takes place between objects that overlap, the behavior is undefined.
19122 <p><b>Returns</b>
19123 <p><!--para 3 -->
19124 The strncat function returns the value of s1.
19127 <p><b>Footnotes</b>
19128 <p><small><a name="note309" href="#note309">309)</a> Thus, the maximum number of characters that can end up in the array pointed to by s1 is
19129 strlen(s1)+n+1.
19130 </small>
19134 <p><!--para 1 -->
19135 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
19136 and strncmp is determined by the sign of the difference between the values of the first
19137 pair of characters (both interpreted as unsigned char) that differ in the objects being
19138 compared.
19142 <p><b>Synopsis</b>
19143 <p><!--para 1 -->
19144 <pre>
19146 int memcmp(const void *s1, const void *s2, size_t n);
19147 </pre>
19148 <p><b>Description</b>
19149 <p><!--para 2 -->
19150 The memcmp function compares the first n characters of the object pointed to by s1 to
19151 the first n characters of the object pointed to by s2.<sup><a href="#note310"><b>310)</b></a></sup>
19152 <p><b>Returns</b>
19153 <p><!--para 3 -->
19154 The memcmp function returns an integer greater than, equal to, or less than zero,
19155 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
19156 pointed to by s2.
19158 <p><b>Footnotes</b>
19159 <p><small><a name="note310" href="#note310">310)</a> The contents of ''holes'' used as padding for purposes of alignment within structure objects are
19160 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
19161 comparison.
19162 </small>
19166 <p><b>Synopsis</b>
19167 <p><!--para 1 -->
19168 <pre>
19170 int strcmp(const char *s1, const char *s2);
19171 </pre>
19172 <p><b>Description</b>
19173 <p><!--para 2 -->
19174 The strcmp function compares the string pointed to by s1 to the string pointed to by
19175 s2.
19176 <p><b>Returns</b>
19177 <p><!--para 3 -->
19178 The strcmp function returns an integer greater than, equal to, or less than zero,
19179 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
19181 <!--page 384 -->
19182 pointed to by s2.
19186 <p><b>Synopsis</b>
19187 <p><!--para 1 -->
19188 <pre>
19190 int strcoll(const char *s1, const char *s2);
19191 </pre>
19192 <p><b>Description</b>
19193 <p><!--para 2 -->
19194 The strcoll function compares the string pointed to by s1 to the string pointed to by
19195 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
19196 <p><b>Returns</b>
19197 <p><!--para 3 -->
19198 The strcoll function returns an integer greater than, equal to, or less than zero,
19199 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
19200 pointed to by s2 when both are interpreted as appropriate to the current locale.
19204 <p><b>Synopsis</b>
19205 <p><!--para 1 -->
19206 <pre>
19208 int strncmp(const char *s1, const char *s2, size_t n);
19209 </pre>
19210 <p><b>Description</b>
19211 <p><!--para 2 -->
19212 The strncmp function compares not more than n characters (characters that follow a
19213 null character are not compared) from the array pointed to by s1 to the array pointed to
19214 by s2.
19215 <p><b>Returns</b>
19216 <p><!--para 3 -->
19217 The strncmp function returns an integer greater than, equal to, or less than zero,
19218 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
19219 to, or less than the possibly null-terminated array pointed to by s2.
19223 <p><b>Synopsis</b>
19224 <p><!--para 1 -->
19225 <pre>
19227 size_t strxfrm(char * restrict s1,
19228 const char * restrict s2,
19229 size_t n);
19230 </pre>
19231 <p><b>Description</b>
19232 <p><!--para 2 -->
19233 The strxfrm function transforms the string pointed to by s2 and places the resulting
19234 string into the array pointed to by s1. The transformation is such that if the strcmp
19235 function is applied to two transformed strings, it returns a value greater than, equal to, or
19236 <!--page 385 -->
19237 less than zero, corresponding to the result of the strcoll function applied to the same
19238 two original strings. No more than n characters are placed into the resulting array
19239 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
19240 be a null pointer. If copying takes place between objects that overlap, the behavior is
19241 undefined.
19242 <p><b>Returns</b>
19243 <p><!--para 3 -->
19244 The strxfrm function returns the length of the transformed string (not including the
19245 terminating null character). If the value returned is n or more, the contents of the array
19246 pointed to by s1 are indeterminate.
19247 <p><!--para 4 -->
19248 EXAMPLE The value of the following expression is the size of the array needed to hold the
19249 transformation of the string pointed to by s.
19250 <pre>
19251 1 + strxfrm(NULL, s, 0)
19252 </pre>
19260 <p><b>Synopsis</b>
19261 <p><!--para 1 -->
19262 <pre>
19264 void *memchr(const void *s, int c, size_t n);
19265 </pre>
19266 <p><b>Description</b>
19267 <p><!--para 2 -->
19268 The memchr function locates the first occurrence of c (converted to an unsigned
19269 char) in the initial n characters (each interpreted as unsigned char) of the object
19270 pointed to by s. The implementation shall behave as if it reads the characters sequentially
19271 and stops as soon as a matching character is found.
19272 <p><b>Returns</b>
19273 <p><!--para 3 -->
19274 The memchr function returns a pointer to the located character, or a null pointer if the
19275 character does not occur in the object.
19279 <p><b>Synopsis</b>
19280 <p><!--para 1 -->
19281 <pre>
19283 char *strchr(const char *s, int c);
19284 </pre>
19285 <p><b>Description</b>
19286 <p><!--para 2 -->
19287 The strchr function locates the first occurrence of c (converted to a char) in the
19288 string pointed to by s. The terminating null character is considered to be part of the
19289 string.
19290 <!--page 386 -->
19291 <p><b>Returns</b>
19292 <p><!--para 3 -->
19293 The strchr function returns a pointer to the located character, or a null pointer if the
19294 character does not occur in the string.
19298 <p><b>Synopsis</b>
19299 <p><!--para 1 -->
19300 <pre>
19302 size_t strcspn(const char *s1, const char *s2);
19303 </pre>
19304 <p><b>Description</b>
19305 <p><!--para 2 -->
19306 The strcspn function computes the length of the maximum initial segment of the string
19307 pointed to by s1 which consists entirely of characters not from the string pointed to by
19308 s2.
19309 <p><b>Returns</b>
19310 <p><!--para 3 -->
19311 The strcspn function returns the length of the segment.
19315 <p><b>Synopsis</b>
19316 <p><!--para 1 -->
19317 <pre>
19319 char *strpbrk(const char *s1, const char *s2);
19320 </pre>
19321 <p><b>Description</b>
19322 <p><!--para 2 -->
19323 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
19324 character from the string pointed to by s2.
19325 <p><b>Returns</b>
19326 <p><!--para 3 -->
19327 The strpbrk function returns a pointer to the character, or a null pointer if no character
19328 from s2 occurs in s1.
19332 <p><b>Synopsis</b>
19333 <p><!--para 1 -->
19334 <pre>
19336 char *strrchr(const char *s, int c);
19337 </pre>
19338 <p><b>Description</b>
19339 <p><!--para 2 -->
19340 The strrchr function locates the last occurrence of c (converted to a char) in the
19341 string pointed to by s. The terminating null character is considered to be part of the
19342 string.
19343 <!--page 387 -->
19344 <p><b>Returns</b>
19345 <p><!--para 3 -->
19346 The strrchr function returns a pointer to the character, or a null pointer if c does not
19347 occur in the string.
19351 <p><b>Synopsis</b>
19352 <p><!--para 1 -->
19353 <pre>
19355 size_t strspn(const char *s1, const char *s2);
19356 </pre>
19357 <p><b>Description</b>
19358 <p><!--para 2 -->
19359 The strspn function computes the length of the maximum initial segment of the string
19360 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
19361 <p><b>Returns</b>
19362 <p><!--para 3 -->
19363 The strspn function returns the length of the segment.
19367 <p><b>Synopsis</b>
19368 <p><!--para 1 -->
19369 <pre>
19371 char *strstr(const char *s1, const char *s2);
19372 </pre>
19373 <p><b>Description</b>
19374 <p><!--para 2 -->
19375 The strstr function locates the first occurrence in the string pointed to by s1 of the
19376 sequence of characters (excluding the terminating null character) in the string pointed to
19377 by s2.
19378 <p><b>Returns</b>
19379 <p><!--para 3 -->
19380 The strstr function returns a pointer to the located string, or a null pointer if the string
19381 is not found. If s2 points to a string with zero length, the function returns s1.
19385 <p><b>Synopsis</b>
19386 <p><!--para 1 -->
19387 <pre>
19389 char *strtok(char * restrict s1,
19390 const char * restrict s2);
19391 </pre>
19392 <p><b>Description</b>
19393 <p><!--para 2 -->
19394 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
19395 sequence of tokens, each of which is delimited by a character from the string pointed to
19396 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
19397 sequence have a null first argument. The separator string pointed to by s2 may be
19398 different from call to call.
19399 <!--page 388 -->
19400 <p><!--para 3 -->
19401 The first call in the sequence searches the string pointed to by s1 for the first character
19402 that is not contained in the current separator string pointed to by s2. If no such character
19403 is found, then there are no tokens in the string pointed to by s1 and the strtok function
19404 returns a null pointer. If such a character is found, it is the start of the first token.
19405 <p><!--para 4 -->
19406 The strtok function then searches from there for a character that is contained in the
19407 current separator string. If no such character is found, the current token extends to the
19408 end of the string pointed to by s1, and subsequent searches for a token will return a null
19409 pointer. If such a character is found, it is overwritten by a null character, which
19410 terminates the current token. The strtok function saves a pointer to the following
19411 character, from which the next search for a token will start.
19412 <p><!--para 5 -->
19413 Each subsequent call, with a null pointer as the value of the first argument, starts
19414 searching from the saved pointer and behaves as described above.
19415 <p><!--para 6 -->
19416 The strtok function is not required to avoid data races with other calls to the strtok
19417 function.<sup><a href="#note311"><b>311)</b></a></sup> The implementation shall behave as if no library function calls the strtok
19418 function.
19419 <p><b>Returns</b>
19420 <p><!--para 7 -->
19421 The strtok function returns a pointer to the first character of a token, or a null pointer
19422 if there is no token.
19423 <p><!--para 8 -->
19424 EXAMPLE
19425 <pre>
19428 char *t;
19433 </pre>
19440 <!--page 389 -->
19442 <p><b>Footnotes</b>
19443 <p><small><a name="note311" href="#note311">311)</a> The strtok_s function can be used instead to avoid data races.
19444 </small>
19451 <p><b>Synopsis</b>
19452 <p><!--para 1 -->
19453 <pre>
19455 void *memset(void *s, int c, size_t n);
19456 </pre>
19457 <p><b>Description</b>
19458 <p><!--para 2 -->
19459 The memset function copies the value of c (converted to an unsigned char) into
19460 each of the first n characters of the object pointed to by s.
19461 <p><b>Returns</b>
19462 <p><!--para 3 -->
19463 The memset function returns the value of s.
19467 <p><b>Synopsis</b>
19468 <p><!--para 1 -->
19469 <pre>
19471 char *strerror(int errnum);
19472 </pre>
19473 <p><b>Description</b>
19474 <p><!--para 2 -->
19475 The strerror function maps the number in errnum to a message string. Typically,
19476 the values for errnum come from errno, but strerror shall map any value of type
19477 int to a message.
19478 <p><!--para 3 -->
19479 The strerror function is not required to avoid data races with other calls to the
19480 strerror function.<sup><a href="#note312"><b>312)</b></a></sup> The implementation shall behave as if no library function calls
19481 the strerror function.
19482 <p><b>Returns</b>
19483 <p><!--para 4 -->
19484 The strerror function returns a pointer to the string, the contents of which are locale-
19485 specific. The array pointed to shall not be modified by the program, but may be
19486 overwritten by a subsequent call to the strerror function.
19492 <!--page 390 -->
19494 <p><b>Footnotes</b>
19495 <p><small><a name="note312" href="#note312">312)</a> The strerror_s function can be used instead to avoid data races.
19496 </small>
19500 <p><b>Synopsis</b>
19501 <p><!--para 1 -->
19502 <pre>
19504 size_t strlen(const char *s);
19505 </pre>
19506 <p><b>Description</b>
19507 <p><!--para 2 -->
19508 The strlen function computes the length of the string pointed to by s.
19509 <p><b>Returns</b>
19510 <p><!--para 3 -->
19511 The strlen function returns the number of characters that precede the terminating null
19512 character.
19513 <!--page 391 -->
19517 <p><!--para 1 -->
19518 The header <a href="#7.25"><tgmath.h></a> includes the headers <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> and
19519 defines several type-generic macros.
19520 <p><!--para 2 -->
19521 Of the <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> functions without an f (float) or l (long
19522 double) suffix, several have one or more parameters whose corresponding real type is
19523 double. For each such function, except modf, there is a corresponding type-generic
19524 macro.<sup><a href="#note313"><b>313)</b></a></sup> The parameters whose corresponding real type is double in the function
19525 synopsis are generic parameters. Use of the macro invokes a function whose
19526 corresponding real type and type domain are determined by the arguments for the generic
19528 <p><!--para 3 -->
19529 Use of the macro invokes a function whose generic parameters have the corresponding
19530 real type determined as follows:
19531 <ul>
19532 <li> First, if any argument for generic parameters has type long double, the type
19533 determined is long double.
19534 <li> Otherwise, if any argument for generic parameters has type double or is of integer
19535 type, the type determined is double.
19536 <li> Otherwise, the type determined is float.
19537 </ul>
19538 <p><!--para 4 -->
19539 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
19540 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
19541 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
19542 corresponding type-generic macro for fabs and cabs is fabs.
19547 <!--page 392 -->
19548 <pre>
19550 function function macro
19551 acos cacos acos
19552 asin casin asin
19553 atan catan atan
19554 acosh cacosh acosh
19555 asinh casinh asinh
19556 atanh catanh atanh
19557 cos ccos cos
19558 sin csin sin
19559 tan ctan tan
19560 cosh ccosh cosh
19561 sinh csinh sinh
19562 tanh ctanh tanh
19563 exp cexp exp
19564 log clog log
19565 pow cpow pow
19566 sqrt csqrt sqrt
19567 fabs cabs fabs
19568 </pre>
19569 If at least one argument for a generic parameter is complex, then use of the macro invokes
19570 a complex function; otherwise, use of the macro invokes a real function.
19571 <p><!--para 5 -->
19572 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
19573 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
19574 name as the function. These type-generic macros are:
19575 <pre>
19576 atan2 fma llround remainder
19577 cbrt fmax log10 remquo
19578 ceil fmin log1p rint
19579 copysign fmod log2 round
19580 erf frexp logb scalbn
19581 erfc hypot lrint scalbln
19582 exp2 ilogb lround tgamma
19583 expm1 ldexp nearbyint trunc
19584 fdim lgamma nextafter
19585 floor llrint nexttoward
19586 </pre>
19587 If all arguments for generic parameters are real, then use of the macro invokes a real
19588 function; otherwise, use of the macro results in undefined behavior.
19589 <!--page 393 -->
19590 <p><!--para 6 -->
19591 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
19592 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
19593 function. These type-generic macros are:
19594 <pre>
19595 carg conj creal
19596 cimag cproj
19597 </pre>
19598 Use of the macro with any real or complex argument invokes a complex function.
19599 <p><!--para 7 -->
19600 EXAMPLE With the declarations
19601 <pre>
19603 int n;
19604 float f;
19605 double d;
19606 long double ld;
19607 float complex fc;
19608 double complex dc;
19609 long double complex ldc;
19610 </pre>
19611 functions invoked by use of type-generic macros are shown in the following table:
19612 <!--page 394 -->
19613 <pre>
19614 macro use invokes
19615 exp(n) exp(n), the function
19616 acosh(f) acoshf(f)
19617 sin(d) sin(d), the function
19618 atan(ld) atanl(ld)
19619 log(fc) clogf(fc)
19620 sqrt(dc) csqrt(dc)
19621 pow(ldc, f) cpowl(ldc, f)
19622 remainder(n, n) remainder(n, n), the function
19623 nextafter(d, f) nextafter(d, f), the function
19624 nexttoward(f, ld) nexttowardf(f, ld)
19625 copysign(n, ld) copysignl(n, ld)
19626 ceil(fc) undefined behavior
19627 rint(dc) undefined behavior
19628 fmax(ldc, ld) undefined behavior
19629 carg(n) carg(n), the function
19630 cproj(f) cprojf(f)
19631 creal(d) creal(d), the function
19632 cimag(ld) cimagl(ld)
19633 fabs(fc) cabsf(fc)
19634 carg(dc) carg(dc), the function
19635 cproj(ldc) cprojl(ldc)
19636 </pre>
19638 <p><b>Footnotes</b>
19639 <p><small><a name="note313" href="#note313">313)</a> Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
19640 make available the corresponding ordinary function.
19641 </small>
19642 <p><small><a name="note314" href="#note314">314)</a> If the type of the argument is not compatible with the type of the parameter for the selected function,
19643 the behavior is undefined.
19644 </small>
19651 <p><!--para 1 -->
19652 The header <a href="#7.26"><threads.h></a> includes the header <a href="#7.27"><time.h></a>, defines macros, and
19653 declares types, enumeration constants, and functions that support multiple threads of
19655 <p><!--para 2 -->
19656 Implementations that define the macro __STDC_NO_THREADS__ need not provide
19657 this header nor support any of its facilities.
19658 <p><!--para 3 -->
19659 The macros are
19660 <pre>
19661 thread_local
19662 </pre>
19663 which expands to _Thread_local;
19664 <pre>
19665 ONCE_FLAG_INIT
19666 </pre>
19667 which expands to a value that can be used to initialize an object of type once_flag;
19668 and
19669 <pre>
19670 TSS_DTOR_ITERATIONS
19671 </pre>
19672 which expands to an integer constant expression representing the maximum number of
19673 times that destructors will be called when a thread terminates.
19674 <p><!--para 4 -->
19675 The types are
19676 <pre>
19677 cnd_t
19678 </pre>
19679 which is a complete object type that holds an identifier for a condition variable;
19680 <pre>
19681 thrd_t
19682 </pre>
19683 which is a complete object type that holds an identifier for a thread;
19684 <pre>
19685 tss_t
19686 </pre>
19687 which is a complete object type that holds an identifier for a thread-specific storage
19688 pointer;
19689 <pre>
19690 mtx_t
19691 </pre>
19692 which is a complete object type that holds an identifier for a mutex;
19693 <pre>
19694 tss_dtor_t
19695 </pre>
19696 which is the function pointer type void (*)(void*), used for a destructor for a
19697 thread-specific storage pointer;
19701 <!--page 395 -->
19702 <pre>
19703 thrd_start_t
19704 </pre>
19705 which is the function pointer type int (*)(void*) that is passed to thrd_create
19706 to create a new thread; and
19707 <pre>
19708 once_flag
19709 </pre>
19710 which is a complete object type that holds a flag for use by call_once.
19711 <p><!--para 5 -->
19712 The enumeration constants are
19713 <pre>
19714 mtx_plain
19715 </pre>
19716 which is passed to mtx_init to create a mutex object that supports neither timeout nor
19717 test and return;
19718 <pre>
19719 mtx_recursive
19720 </pre>
19721 which is passed to mtx_init to create a mutex object that supports recursive locking;
19722 <pre>
19723 mtx_timed
19724 </pre>
19725 which is passed to mtx_init to create a mutex object that supports timeout;
19726 <pre>
19727 thrd_timedout
19728 </pre>
19729 which is returned by a timed wait function to indicate that the time specified in the call
19730 was reached without acquiring the requested resource;
19731 <pre>
19732 thrd_success
19733 </pre>
19734 which is returned by a function to indicate that the requested operation succeeded;
19735 <pre>
19736 thrd_busy
19737 </pre>
19738 which is returned by a function to indicate that the requested operation failed because a
19739 resource requested by a test and return function is already in use;
19740 <pre>
19741 thrd_error
19742 </pre>
19743 which is returned by a function to indicate that the requested operation failed; and
19744 <pre>
19745 thrd_nomem
19746 </pre>
19747 which is returned by a function to indicate that the requested operation failed because it
19748 was unable to allocate memory.
19750 <!--page 396 -->
19752 <p><b>Footnotes</b>
19753 <p><small><a name="note315" href="#note315">315)</a> See ''future library directions'' (<a href="#7.31.15">7.31.15</a>).
19754 </small>
19761 <p><b>Synopsis</b>
19762 <p><!--para 1 -->
19763 <pre>
19765 void call_once(once_flag *flag, void (*func)(void));
19766 </pre>
19767 <p><b>Description</b>
19768 <p><!--para 2 -->
19769 The call_once function uses the once_flag pointed to by flag to ensure that
19770 func is called exactly once, the first time the call_once function is called with that
19771 value of flag. Completion of an effective call to the call_once function synchronizes
19772 with all subsequent calls to the call_once function with the same value of flag.
19773 <p><b>Returns</b>
19774 <p><!--para 3 -->
19775 The call_once function returns no value.
19782 <p><b>Synopsis</b>
19783 <p><!--para 1 -->
19784 <pre>
19786 int cnd_broadcast(cnd_t *cond);
19787 </pre>
19788 <p><b>Description</b>
19789 <p><!--para 2 -->
19790 The cnd_broadcast function unblocks all of the threads that are blocked on the
19791 condition variable pointed to by cond at the time of the call. If no threads are blocked
19792 on the condition variable pointed to by cond at the time of the call, the function does
19793 nothing.
19794 <p><b>Returns</b>
19795 <p><!--para 3 -->
19796 The cnd_broadcast function returns thrd_success on success, or thrd_error
19797 if the request could not be honored.
19801 <p><b>Synopsis</b>
19802 <p><!--para 1 -->
19803 <pre>
19805 void cnd_destroy(cnd_t *cond);
19806 </pre>
19807 <p><b>Description</b>
19808 <p><!--para 2 -->
19809 The cnd_destroy function releases all resources used by the condition variable
19810 pointed to by cond. The cnd_destroy function requires that no threads be blocked
19811 waiting for the condition variable pointed to by cond.
19812 <!--page 397 -->
19813 <p><b>Returns</b>
19814 <p><!--para 3 -->
19815 The cnd_destroy function returns no value.
19819 <p><b>Synopsis</b>
19820 <p><!--para 1 -->
19821 <pre>
19823 int cnd_init(cnd_t *cond);
19824 </pre>
19825 <p><b>Description</b>
19826 <p><!--para 2 -->
19827 The cnd_init function creates a condition variable. If it succeeds it sets the variable
19828 pointed to by cond to a value that uniquely identifies the newly created condition
19829 variable. A thread that calls cnd_wait on a newly created condition variable will
19830 block.
19831 <p><b>Returns</b>
19832 <p><!--para 3 -->
19833 The cnd_init function returns thrd_success on success, or thrd_nomem if no
19834 memory could be allocated for the newly created condition, or thrd_error if the
19835 request could not be honored.
19839 <p><b>Synopsis</b>
19840 <p><!--para 1 -->
19841 <pre>
19843 int cnd_signal(cnd_t *cond);
19844 </pre>
19845 <p><b>Description</b>
19846 <p><!--para 2 -->
19847 The cnd_signal function unblocks one of the threads that are blocked on the
19848 condition variable pointed to by cond at the time of the call. If no threads are blocked
19849 on the condition variable at the time of the call, the function does nothing and return
19850 success.
19851 <p><b>Returns</b>
19852 <p><!--para 3 -->
19853 The cnd_signal function returns thrd_success on success or thrd_error if
19854 the request could not be honored.
19858 <p><b>Synopsis</b>
19859 <p><!--para 1 -->
19860 <!--page 398 -->
19861 <pre>
19863 int cnd_timedwait(cnd_t *restrict cond,
19864 mtx_t *restrict mtx,
19865 const struct timespec *restrict ts);
19866 </pre>
19867 <p><b>Description</b>
19868 <p><!--para 2 -->
19869 The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and
19870 endeavors to block until the condition variable pointed to by cond is signaled by a call to
19871 cnd_signal or to cnd_broadcast, or until after the TIME_UTC-based calendar
19872 time pointed to by ts. When the calling thread becomes unblocked it locks the variable
19873 pointed to by mtx before it returns. The cnd_timedwait function requires that the
19874 mutex pointed to by mtx be locked by the calling thread.
19875 <p><b>Returns</b>
19876 <p><!--para 3 -->
19877 The cnd_timedwait function returns thrd_success upon success, or
19878 thrd_timedout if the time specified in the call was reached without acquiring the
19879 requested resource, or thrd_error if the request could not be honored.
19883 <p><b>Synopsis</b>
19884 <p><!--para 1 -->
19885 <pre>
19887 int cnd_wait(cnd_t *cond, mtx_t *mtx);
19888 </pre>
19889 <p><b>Description</b>
19890 <p><!--para 2 -->
19891 The cnd_wait function atomically unlocks the mutex pointed to by mtx and endeavors
19892 to block until the condition variable pointed to by cond is signaled by a call to
19893 cnd_signal or to cnd_broadcast. When the calling thread becomes unblocked it
19894 locks the mutex pointed to by mtx before it returns. The cnd_wait function requires
19895 that the mutex pointed to by mtx be locked by the calling thread.
19896 <p><b>Returns</b>
19897 <p><!--para 3 -->
19898 The cnd_wait function returns thrd_success on success or thrd_error if the
19899 request could not be honored.
19906 <p><b>Synopsis</b>
19907 <p><!--para 1 -->
19908 <pre>
19910 void mtx_destroy(mtx_t *mtx);
19911 </pre>
19912 <p><b>Description</b>
19913 <p><!--para 2 -->
19914 The mtx_destroy function releases any resources used by the mutex pointed to by
19915 mtx. No threads can be blocked waiting for the mutex pointed to by mtx.
19916 <p><b>Returns</b>
19917 <p><!--para 3 -->
19918 The mtx_destroy function returns no value.
19919 <!--page 399 -->
19923 <p><b>Synopsis</b>
19924 <p><!--para 1 -->
19925 <pre>
19927 int mtx_init(mtx_t *mtx, int type);
19928 </pre>
19929 <p><b>Description</b>
19930 <p><!--para 2 -->
19931 The mtx_init function creates a mutex object with properties indicated by type,
19932 which must have one of the six values:
19933 mtx_plain for a simple non-recursive mutex,
19934 mtx_timed for a non-recursive mutex that supports timeout, *
19935 mtx_plain | mtx_recursive for a simple recursive mutex, or
19936 mtx_timed | mtx_recursive for a recursive mutex that supports timeout.
19937 <p><!--para 3 -->
19938 If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that
19939 uniquely identifies the newly created mutex.
19940 <p><b>Returns</b>
19941 <p><!--para 4 -->
19942 The mtx_init function returns thrd_success on success, or thrd_error if the
19943 request could not be honored.
19947 <p><b>Synopsis</b>
19948 <p><!--para 1 -->
19949 <pre>
19951 int mtx_lock(mtx_t *mtx);
19952 </pre>
19953 <p><b>Description</b>
19954 <p><!--para 2 -->
19955 The mtx_lock function blocks until it locks the mutex pointed to by mtx. If the mutex
19956 is non-recursive, it shall not be locked by the calling thread. Prior calls to mtx_unlock
19957 on the same mutex shall synchronize with this operation.
19958 <p><b>Returns</b>
19959 <p><!--para 3 -->
19960 The mtx_lock function returns thrd_success on success, or thrd_error if the *
19961 request could not be honored.
19965 <p><b>Synopsis</b>
19966 <p><!--para 1 -->
19967 <!--page 400 -->
19968 <pre>
19970 int mtx_timedlock(mtx_t *restrict mtx,
19971 const struct timespec *restrict ts);
19972 </pre>
19973 <p><b>Description</b>
19974 <p><!--para 2 -->
19975 The mtx_timedlock function endeavors to block until it locks the mutex pointed to by
19976 mtx or until after the TIME_UTC-based calendar time pointed to by ts. The specified
19977 mutex shall support timeout. If the operation succeeds, prior calls to mtx_unlock on
19978 the same mutex shall synchronize with this operation.
19979 <p><b>Returns</b>
19980 <p><!--para 3 -->
19981 The mtx_timedlock function returns thrd_success on success, or
19982 thrd_timedout if the time specified was reached without acquiring the requested
19983 resource, or thrd_error if the request could not be honored.
19987 <p><b>Synopsis</b>
19988 <p><!--para 1 -->
19989 <pre>
19991 int mtx_trylock(mtx_t *mtx);
19992 </pre>
19993 <p><b>Description</b>
19994 <p><!--para 2 -->
19995 The mtx_trylock function endeavors to lock the mutex pointed to by mtx. If the *
19996 mutex is already locked, the function returns without blocking. If the operation succeeds,
19997 prior calls to mtx_unlock on the same mutex shall synchronize with this operation.
19998 <p><b>Returns</b>
19999 <p><!--para 3 -->
20000 The mtx_trylock function returns thrd_success on success, or thrd_busy if
20001 the resource requested is already in use, or thrd_error if the request could not be
20002 honored.
20006 <p><b>Synopsis</b>
20007 <p><!--para 1 -->
20008 <pre>
20010 int mtx_unlock(mtx_t *mtx);
20011 </pre>
20012 <p><b>Description</b>
20013 <p><!--para 2 -->
20014 The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to
20015 by mtx shall be locked by the calling thread.
20016 <p><b>Returns</b>
20017 <p><!--para 3 -->
20018 The mtx_unlock function returns thrd_success on success or thrd_error if
20019 the request could not be honored.
20020 <!--page 401 -->
20027 <p><b>Synopsis</b>
20028 <p><!--para 1 -->
20029 <pre>
20031 int thrd_create(thrd_t *thr, thrd_start_t func,
20032 void *arg);
20033 </pre>
20034 <p><b>Description</b>
20035 <p><!--para 2 -->
20036 The thrd_create function creates a new thread executing func(arg). If the
20037 thrd_create function succeeds, it sets the object pointed to by thr to the identifier of
20038 the newly created thread. (A thread's identifier may be reused for a different thread once
20039 the original thread has exited and either been detached or joined to another thread.) The
20040 completion of the thrd_create function synchronizes with the beginning of the
20041 execution of the new thread.
20042 <p><b>Returns</b>
20043 <p><!--para 3 -->
20044 The thrd_create function returns thrd_success on success, or thrd_nomem if
20045 no memory could be allocated for the thread requested, or thrd_error if the request
20046 could not be honored.
20050 <p><b>Synopsis</b>
20051 <p><!--para 1 -->
20052 <pre>
20054 thrd_t thrd_current(void);
20055 </pre>
20056 <p><b>Description</b>
20057 <p><!--para 2 -->
20058 The thrd_current function identifies the thread that called it.
20059 <p><b>Returns</b>
20060 <p><!--para 3 -->
20061 The thrd_current function returns the identifier of the thread that called it.
20065 <p><b>Synopsis</b>
20066 <p><!--para 1 -->
20067 <pre>
20069 int thrd_detach(thrd_t thr);
20070 </pre>
20071 <p><b>Description</b>
20072 <p><!--para 2 -->
20073 The thrd_detach function tells the operating system to dispose of any resources
20074 allocated to the thread identified by thr when that thread terminates. The thread
20075 identified by thr shall not have been previously detached or joined with another thread.
20076 <!--page 402 -->
20077 <p><b>Returns</b>
20078 <p><!--para 3 -->
20079 The thrd_detach function returns thrd_success on success or thrd_error if
20080 the request could not be honored.
20084 <p><b>Synopsis</b>
20085 <p><!--para 1 -->
20086 <pre>
20088 int thrd_equal(thrd_t thr0, thrd_t thr1);
20089 </pre>
20090 <p><b>Description</b>
20091 <p><!--para 2 -->
20092 The thrd_equal function will determine whether the thread identified by thr0 refers
20093 to the thread identified by thr1.
20094 <p><b>Returns</b>
20095 <p><!--para 3 -->
20096 The thrd_equal function returns zero if the thread thr0 and the thread thr1 refer to
20097 different threads. Otherwise the thrd_equal function returns a nonzero value.
20101 <p><b>Synopsis</b>
20102 <p><!--para 1 -->
20103 <pre>
20105 _Noreturn void thrd_exit(int res);
20106 </pre>
20107 <p><b>Description</b>
20108 <p><!--para 2 -->
20109 The thrd_exit function terminates execution of the calling thread and sets its result
20110 code to res.
20111 <p><!--para 3 -->
20112 The program shall terminate normally after the last thread has been terminated. The
20113 behavior shall be as if the program called the exit function with the status
20114 EXIT_SUCCESS at thread termination time.
20115 <p><b>Returns</b>
20116 <p><!--para 4 -->
20117 The thrd_exit function returns no value.
20121 <p><b>Synopsis</b>
20122 <p><!--para 1 -->
20123 <pre>
20125 int thrd_join(thrd_t thr, int *res);
20126 </pre>
20127 <p><b>Description</b>
20128 <p><!--para 2 -->
20129 The thrd_join function joins the thread identified by thr with the current thread by
20130 blocking until the other thread has terminated. If the parameter res is not a null pointer,
20131 it stores the thread's result code in the integer pointed to by res. The termination of the
20132 <!--page 403 -->
20133 other thread synchronizes with the completion of the thrd_join function. The thread
20134 identified by thr shall not have been previously detached or joined with another thread.
20135 <p><b>Returns</b>
20136 <p><!--para 3 -->
20137 The thrd_join function returns thrd_success on success or thrd_error if the
20138 request could not be honored.
20142 <p><b>Synopsis</b>
20143 <p><!--para 1 -->
20144 <pre>
20146 int thrd_sleep(const struct timespec *duration,
20147 struct timespec *remaining);
20148 </pre>
20149 <p><b>Description</b>
20150 <p><!--para 2 -->
20151 The thrd_sleep function suspends execution of the calling thread until either the
20152 interval specified by duration has elapsed or a signal which is not being ignored is
20153 received. If interrupted by a signal and the remaining argument is not null, the
20154 amount of time remaining (the requested interval minus the time actually slept) is stored
20155 in the interval it points to. The duration and remaining arguments may point to the
20156 same object.
20157 <p><!--para 3 -->
20158 The suspension time may be longer than requested because the interval is rounded up to
20159 an integer multiple of the sleep resolution or because of the scheduling of other activity
20160 by the system. But, except for the case of being interrupted by a signal, the suspension
20161 time shall not be less than that specified, as measured by the system clock TIME_UTC.
20162 <p><b>Returns</b>
20163 <p><!--para 4 -->
20164 The thrd_sleep function returns zero if the requested time has elapsed, -1 if it has
20165 been interrupted by a signal, or a negative value if it fails.
20169 <p><b>Synopsis</b>
20170 <p><!--para 1 -->
20171 <pre>
20173 void thrd_yield(void);
20174 </pre>
20175 <p><b>Description</b>
20176 <p><!--para 2 -->
20177 The thrd_yield function endeavors to permit other threads to run, even if the current
20178 thread would ordinarily continue to run.
20179 <p><b>Returns</b>
20180 <p><!--para 3 -->
20181 The thrd_yield function returns no value.
20182 <!--page 404 -->
20189 <p><b>Synopsis</b>
20190 <p><!--para 1 -->
20191 <pre>
20193 int tss_create(tss_t *key, tss_dtor_t dtor);
20194 </pre>
20195 <p><b>Description</b>
20196 <p><!--para 2 -->
20197 The tss_create function creates a thread-specific storage pointer with destructor
20198 dtor, which may be null.
20199 <p><b>Returns</b>
20200 <p><!--para 3 -->
20201 If the tss_create function is successful, it sets the thread-specific storage pointed to
20202 by key to a value that uniquely identifies the newly created pointer and returns
20203 thrd_success; otherwise, thrd_error is returned and the thread-specific storage
20204 pointed to by key is set to an undefined value.
20208 <p><b>Synopsis</b>
20209 <p><!--para 1 -->
20210 <pre>
20212 void tss_delete(tss_t key);
20213 </pre>
20214 <p><b>Description</b>
20215 <p><!--para 2 -->
20216 The tss_delete function releases any resources used by the thread-specific storage
20217 identified by key.
20218 <p><b>Returns</b>
20219 <p><!--para 3 -->
20220 The tss_delete function returns no value.
20224 <p><b>Synopsis</b>
20225 <p><!--para 1 -->
20226 <pre>
20228 void *tss_get(tss_t key);
20229 </pre>
20230 <p><b>Description</b>
20231 <p><!--para 2 -->
20232 The tss_get function returns the value for the current thread held in the thread-specific
20233 storage identified by key.
20234 <p><b>Returns</b>
20235 <p><!--para 3 -->
20236 The tss_get function returns the value for the current thread if successful, or zero if
20237 unsuccessful.
20238 <!--page 405 -->
20242 <p><b>Synopsis</b>
20243 <p><!--para 1 -->
20244 <pre>
20246 int tss_set(tss_t key, void *val);
20247 </pre>
20248 <p><b>Description</b>
20249 <p><!--para 2 -->
20250 The tss_set function sets the value for the current thread held in the thread-specific
20251 storage identified by key to val.
20252 <p><b>Returns</b>
20253 <p><!--para 3 -->
20254 The tss_set function returns thrd_success on success or thrd_error if the
20255 request could not be honored. *
20256 <!--page 406 -->
20263 <p><!--para 1 -->
20264 The header <a href="#7.27"><time.h></a> defines two macros, and declares several types and functions for
20265 manipulating time. Many functions deal with a calendar time that represents the current
20266 date (according to the Gregorian calendar) and time. Some functions deal with local
20267 time, which is the calendar time expressed for some specific time zone, and with Daylight
20268 Saving Time, which is a temporary change in the algorithm for determining local time.
20269 The local time zone and Daylight Saving Time are implementation-defined.
20270 <p><!--para 2 -->
20272 <pre>
20273 CLOCKS_PER_SEC
20274 </pre>
20275 which expands to an expression with type clock_t (described below) that is the
20276 number per second of the value returned by the clock function; and
20277 <pre>
20278 TIME_UTC
20279 </pre>
20280 which expands to an integer constant greater than 0 that designates the UTC time
20282 <p><!--para 3 -->
20284 <pre>
20285 clock_t
20286 </pre>
20287 and
20288 <pre>
20289 time_t
20290 </pre>
20291 which are real types capable of representing times;
20292 <pre>
20293 struct timespec
20294 </pre>
20295 which holds an interval specified in seconds and nanoseconds (which may represent a
20296 calendar time based on a particular epoch); and
20297 <pre>
20298 struct tm
20299 </pre>
20300 which holds the components of a calendar time, called the broken-down time.
20301 <p><!--para 4 -->
20302 The range and precision of times representable in clock_t and time_t are
20303 implementation-defined. The timespec structure shall contain at least the following
20308 <!--page 407 -->
20309 <pre>
20310 time_t tv_sec; // whole seconds -- >= 0
20311 long tv_nsec; // nanoseconds -- [0, 999999999]
20312 </pre>
20313 The tm structure shall contain at least the following members, in any order. The
20314 semantics of the members and their normal ranges are expressed in the comments.<sup><a href="#note318"><b>318)</b></a></sup>
20315 <pre>
20316 int tm_sec; // seconds after the minute -- [0, 60]
20317 int tm_min; // minutes after the hour -- [0, 59]
20318 int tm_hour; // hours since midnight -- [0, 23]
20319 int tm_mday; // day of the month -- [1, 31]
20320 int tm_mon; // months since January -- [0, 11]
20321 int tm_year; // years since 1900
20322 int tm_wday; // days since Sunday -- [0, 6]
20323 int tm_yday; // days since January 1 -- [0, 365]
20324 int tm_isdst; // Daylight Saving Time flag
20325 </pre>
20326 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
20327 Saving Time is not in effect, and negative if the information is not available.
20329 <p><b>Footnotes</b>
20330 <p><small><a name="note316" href="#note316">316)</a> Implementations may define additional time bases, but are only required to support a real time clock
20331 based on UTC.
20332 </small>
20333 <p><small><a name="note317" href="#note317">317)</a> The tv_sec member is a linear count of seconds and may not have the normal semantics of a
20334 time_t. The semantics of the members and their normal ranges are expressed in the comments.
20335 </small>
20336 <p><small><a name="note318" href="#note318">318)</a> The range [0, 60] for tm_sec allows for a positive leap second.
20337 </small>
20344 <p><b>Synopsis</b>
20345 <p><!--para 1 -->
20346 <pre>
20348 clock_t clock(void);
20349 </pre>
20350 <p><b>Description</b>
20351 <p><!--para 2 -->
20352 The clock function determines the processor time used.
20353 <p><b>Returns</b>
20354 <p><!--para 3 -->
20355 The clock function returns the implementation's best approximation to the processor
20356 time used by the program since the beginning of an implementation-defined era related
20357 only to the program invocation. To determine the time in seconds, the value returned by
20358 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
20359 the processor time used is not available or its value cannot be represented, the function
20365 <!--page 408 -->
20367 <p><b>Footnotes</b>
20368 <p><small><a name="note319" href="#note319">319)</a> In order to measure the time spent in a program, the clock function should be called at the start of
20369 the program and its return value subtracted from the value returned by subsequent calls.
20370 </small>
20374 <p><b>Synopsis</b>
20375 <p><!--para 1 -->
20376 <pre>
20378 double difftime(time_t time1, time_t time0);
20379 </pre>
20380 <p><b>Description</b>
20381 <p><!--para 2 -->
20382 The difftime function computes the difference between two calendar times: time1 -
20383 time0.
20384 <p><b>Returns</b>
20385 <p><!--para 3 -->
20386 The difftime function returns the difference expressed in seconds as a double.
20390 <p><b>Synopsis</b>
20391 <p><!--para 1 -->
20392 <pre>
20394 time_t mktime(struct tm *timeptr);
20395 </pre>
20396 <p><b>Description</b>
20397 <p><!--para 2 -->
20398 The mktime function converts the broken-down time, expressed as local time, in the
20399 structure pointed to by timeptr into a calendar time value with the same encoding as
20400 that of the values returned by the time function. The original values of the tm_wday
20401 and tm_yday components of the structure are ignored, and the original values of the
20402 other components are not restricted to the ranges indicated above.<sup><a href="#note320"><b>320)</b></a></sup> On successful
20403 completion, the values of the tm_wday and tm_yday components of the structure are
20404 set appropriately, and the other components are set to represent the specified calendar
20405 time, but with their values forced to the ranges indicated above; the final value of
20406 tm_mday is not set until tm_mon and tm_year are determined.
20407 <p><b>Returns</b>
20408 <p><!--para 3 -->
20409 The mktime function returns the specified calendar time encoded as a value of type
20410 time_t. If the calendar time cannot be represented, the function returns the value
20411 (time_t)(-1).
20412 <p><!--para 4 -->
20413 EXAMPLE What day of the week is July 4, 2001?
20418 <!--page 409 -->
20419 <pre>
20422 static const char *const wday[] = {
20425 };
20426 struct tm time_str;
20427 /* ... */
20428 time_str.tm_year = 2001 - 1900;
20429 time_str.tm_mon = 7 - 1;
20430 time_str.tm_mday = 4;
20431 time_str.tm_hour = 0;
20432 time_str.tm_min = 0;
20433 time_str.tm_sec = 1;
20434 time_str.tm_isdst = -1;
20435 if (mktime(&time_str) == (time_t)(-1))
20436 time_str.tm_wday = 7;
20438 </pre>
20441 <p><b>Footnotes</b>
20442 <p><small><a name="note320" href="#note320">320)</a> Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
20443 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
20444 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
20445 </small>
20449 <p><b>Synopsis</b>
20450 <p><!--para 1 -->
20451 <pre>
20453 time_t time(time_t *timer);
20454 </pre>
20455 <p><b>Description</b>
20456 <p><!--para 2 -->
20457 The time function determines the current calendar time. The encoding of the value is
20458 unspecified.
20459 <p><b>Returns</b>
20460 <p><!--para 3 -->
20461 The time function returns the implementation's best approximation to the current
20462 calendar time. The value (time_t)(-1) is returned if the calendar time is not
20463 available. If timer is not a null pointer, the return value is also assigned to the object it
20464 points to.
20468 <p><b>Synopsis</b>
20469 <p><!--para 1 -->
20470 <pre>
20472 int timespec_get(struct timespec *ts, int base);
20473 </pre>
20474 <p><b>Description</b>
20475 <p><!--para 2 -->
20476 The timespec_get function sets the interval pointed to by ts to hold the current
20477 calendar time based on the specified time base.
20478 <p><!--para 3 -->
20479 If base is TIME_UTC, the tv_sec member is set to the number of seconds since an
20480 implementation defined epoch, truncated to a whole value and the tv_nsec member is
20481 set to the integral number of nanoseconds, rounded to the resolution of the system
20482 <!--page 410 -->
20484 <p><b>Returns</b>
20485 <p><!--para 4 -->
20486 If the timespec_get function is successful it returns the nonzero value base;
20487 otherwise, it returns zero.
20489 <p><b>Footnotes</b>
20490 <p><small><a name="note321" href="#note321">321)</a> Although a struct timespec object describes times with nanosecond resolution, the available
20491 resolution is system dependent and may even be greater than 1 second.
20492 </small>
20496 <p><!--para 1 -->
20497 Except for the strftime function, these functions each return a pointer to one of two
20498 types of static objects: a broken-down time structure or an array of char. Execution of
20499 any of the functions that return a pointer to one of these object types may overwrite the
20500 information in any object of the same type pointed to by the value returned from any
20501 previous call to any of them and the functions are not required to avoid data races with
20502 each other.<sup><a href="#note322"><b>322)</b></a></sup> The implementation shall behave as if no other library functions call these
20503 functions.
20505 <p><b>Footnotes</b>
20506 <p><small><a name="note322" href="#note322">322)</a> Alternative time conversion functions that do avoid data races are specified in <a href="#K.3.8.2">K.3.8.2</a>.
20507 </small>
20511 <p><b>Synopsis</b>
20512 <p><!--para 1 -->
20513 <pre>
20515 char *asctime(const struct tm *timeptr);
20516 </pre>
20517 <p><b>Description</b>
20518 <p><!--para 2 -->
20519 The asctime function converts the broken-down time in the structure pointed to by
20520 timeptr into a string in the form
20521 <pre>
20522 Sun Sep 16 01:03:52 1973\n\0
20523 </pre>
20524 using the equivalent of the following algorithm.
20525 char *asctime(const struct tm *timeptr)
20526 {
20527 <pre>
20528 static const char wday_name[7][3] = {
20530 };
20531 static const char mon_name[12][3] = {
20534 };
20535 static char result[26];
20536 </pre>
20540 <!--page 411 -->
20541 <pre>
20543 wday_name[timeptr->tm_wday],
20544 mon_name[timeptr->tm_mon],
20545 timeptr->tm_mday, timeptr->tm_hour,
20546 timeptr->tm_min, timeptr->tm_sec,
20547 1900 + timeptr->tm_year);
20548 return result;
20549 </pre>
20550 }
20551 <p><!--para 3 -->
20552 If any of the members of the broken-down time contain values that are outside their
20553 normal ranges,<sup><a href="#note323"><b>323)</b></a></sup> the behavior of the asctime function is undefined. Likewise, if the
20554 calculated year exceeds four digits or is less than the year 1000, the behavior is
20555 undefined.
20556 <p><b>Returns</b>
20557 <p><!--para 4 -->
20558 The asctime function returns a pointer to the string.
20560 <p><b>Footnotes</b>
20562 </small>
20566 <p><b>Synopsis</b>
20567 <p><!--para 1 -->
20568 <pre>
20570 char *ctime(const time_t *timer);
20571 </pre>
20572 <p><b>Description</b>
20573 <p><!--para 2 -->
20574 The ctime function converts the calendar time pointed to by timer to local time in the
20575 form of a string. It is equivalent to
20576 <pre>
20577 asctime(localtime(timer))
20578 </pre>
20579 <p><b>Returns</b>
20580 <p><!--para 3 -->
20581 The ctime function returns the pointer returned by the asctime function with that
20582 broken-down time as argument.
20587 <p><b>Synopsis</b>
20588 <p><!--para 1 -->
20589 <pre>
20591 struct tm *gmtime(const time_t *timer);
20592 </pre>
20597 <!--page 412 -->
20598 <p><b>Description</b>
20599 <p><!--para 2 -->
20600 The gmtime function converts the calendar time pointed to by timer into a broken-
20601 down time, expressed as UTC.
20602 <p><b>Returns</b>
20603 <p><!--para 3 -->
20604 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
20605 specified time cannot be converted to UTC.
20609 <p><b>Synopsis</b>
20610 <p><!--para 1 -->
20611 <pre>
20613 struct tm *localtime(const time_t *timer);
20614 </pre>
20615 <p><b>Description</b>
20616 <p><!--para 2 -->
20617 The localtime function converts the calendar time pointed to by timer into a
20618 broken-down time, expressed as local time.
20619 <p><b>Returns</b>
20620 <p><!--para 3 -->
20621 The localtime function returns a pointer to the broken-down time, or a null pointer if
20622 the specified time cannot be converted to local time.
20626 <p><b>Synopsis</b>
20627 <p><!--para 1 -->
20628 <pre>
20630 size_t strftime(char * restrict s,
20631 size_t maxsize,
20632 const char * restrict format,
20633 const struct tm * restrict timeptr);
20634 </pre>
20635 <p><b>Description</b>
20636 <p><!--para 2 -->
20637 The strftime function places characters into the array pointed to by s as controlled by
20638 the string pointed to by format. The format shall be a multibyte character sequence,
20639 beginning and ending in its initial shift state. The format string consists of zero or
20640 more conversion specifiers and ordinary multibyte characters. A conversion specifier
20641 consists of a % character, possibly followed by an E or O modifier character (described
20642 below), followed by a character that determines the behavior of the conversion specifier.
20643 All ordinary multibyte characters (including the terminating null character) are copied
20644 unchanged into the array. If copying takes place between objects that overlap, the
20645 behavior is undefined. No more than maxsize characters are placed into the array.
20646 <p><!--para 3 -->
20647 Each conversion specifier is replaced by appropriate characters as described in the
20648 following list. The appropriate characters are determined using the LC_TIME category
20649 <!--page 413 -->
20650 of the current locale and by the values of zero or more members of the broken-down time
20651 structure pointed to by timeptr, as specified in brackets in the description. If any of
20652 the specified values is outside the normal range, the characters stored are unspecified.
20653 %a is replaced by the locale's abbreviated weekday name. [tm_wday]
20654 %A is replaced by the locale's full weekday name. [tm_wday]
20655 %b is replaced by the locale's abbreviated month name. [tm_mon]
20656 %B is replaced by the locale's full month name. [tm_mon]
20657 %c is replaced by the locale's appropriate date and time representation. [all specified
20658 <pre>
20660 </pre>
20661 %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
20662 <pre>
20663 number (00-99). [tm_year]
20664 </pre>
20665 %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
20666 %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
20667 %e is replaced by the day of the month as a decimal number (1-31); a single digit is
20668 <pre>
20669 preceded by a space. [tm_mday]
20670 </pre>
20671 %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
20672 <pre>
20673 tm_mday]
20674 </pre>
20675 %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
20676 <pre>
20677 number (00-99). [tm_year, tm_wday, tm_yday]
20678 </pre>
20679 %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
20680 <pre>
20681 [tm_year, tm_wday, tm_yday]
20682 </pre>
20683 %h is equivalent to ''%b''. [tm_mon]
20684 %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
20685 %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
20686 %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
20687 %m is replaced by the month as a decimal number (01-12). [tm_mon]
20688 %M is replaced by the minute as a decimal number (00-59). [tm_min]
20689 %n is replaced by a new-line character.
20690 %p is replaced by the locale's equivalent of the AM/PM designations associated with a
20691 <pre>
20692 12-hour clock. [tm_hour]
20693 </pre>
20694 %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
20695 %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
20696 %S is replaced by the second as a decimal number (00-60). [tm_sec]
20697 %t is replaced by a horizontal-tab character.
20698 %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
20699 <pre>
20700 tm_sec]
20701 </pre>
20702 %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
20703 <pre>
20704 is 1. [tm_wday]
20705 </pre>
20706 %U is replaced by the week number of the year (the first Sunday as the first day of week
20707 <pre>
20708 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
20709 </pre>
20710 %V is replaced by the ISO 8601 week number (see below) as a decimal number
20711 <!--page 414 -->
20712 <pre>
20713 (01-53). [tm_year, tm_wday, tm_yday]
20714 </pre>
20715 %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
20716 <pre>
20717 [tm_wday]
20718 </pre>
20719 %W is replaced by the week number of the year (the first Monday as the first day of
20720 <pre>
20721 week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
20722 </pre>
20723 %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.27.1">7.27.1</a>]
20724 %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.27.1">7.27.1</a>]
20725 %y is replaced by the last 2 digits of the year as a decimal number (00-99).
20726 <pre>
20727 [tm_year]
20728 </pre>
20729 %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
20730 %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
20731 <pre>
20732 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
20733 zone is determinable. [tm_isdst]
20734 </pre>
20735 %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
20736 <pre>
20737 time zone is determinable. [tm_isdst]
20738 </pre>
20739 %% is replaced by %.
20740 <p><!--para 4 -->
20741 Some conversion specifiers can be modified by the inclusion of an E or O modifier
20742 character to indicate an alternative format or specification. If the alternative format or
20743 specification does not exist for the current locale, the modifier is ignored.
20744 %Ec is replaced by the locale's alternative date and time representation.
20745 %EC is replaced by the name of the base year (period) in the locale's alternative
20746 <pre>
20747 representation.
20748 </pre>
20749 %Ex is replaced by the locale's alternative date representation.
20750 %EX is replaced by the locale's alternative time representation.
20751 %Ey is replaced by the offset from %EC (year only) in the locale's alternative
20752 <pre>
20753 representation.
20754 </pre>
20755 %EY is replaced by the locale's full alternative year representation.
20756 %Od is replaced by the day of the month, using the locale's alternative numeric symbols
20757 <pre>
20758 (filled as needed with leading zeros, or with leading spaces if there is no alternative
20759 symbol for zero).
20760 </pre>
20761 %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
20762 <pre>
20763 (filled as needed with leading spaces).
20764 </pre>
20765 %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
20766 <pre>
20767 symbols.
20768 </pre>
20769 %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
20770 <pre>
20771 symbols.
20772 </pre>
20773 %Om is replaced by the month, using the locale's alternative numeric symbols.
20774 %OM is replaced by the minutes, using the locale's alternative numeric symbols.
20775 %OS is replaced by the seconds, using the locale's alternative numeric symbols.
20776 %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
20777 <!--page 415 -->
20778 <pre>
20779 representation, where Monday is 1.
20780 </pre>
20781 %OU is replaced by the week number, using the locale's alternative numeric symbols.
20782 %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
20783 <pre>
20784 symbols.
20785 </pre>
20786 %Ow is replaced by the weekday as a number, using the locale's alternative numeric
20787 <pre>
20788 symbols.
20789 </pre>
20790 %OW is replaced by the week number of the year, using the locale's alternative numeric
20791 <pre>
20792 symbols.
20793 </pre>
20794 %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
20795 <pre>
20796 symbols.
20797 </pre>
20798 <p><!--para 5 -->
20799 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
20800 weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
20801 which is also the week that includes the first Thursday of the year, and is also the first
20802 week that contains at least four days in the year. If the first Monday of January is the
20803 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
20804 for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
20805 December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
20806 the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
20807 %V is replaced by 01.
20808 <p><!--para 6 -->
20809 If a conversion specifier is not one of the above, the behavior is undefined.
20810 <p><!--para 7 -->
20812 following specifiers are:
20813 %a the first three characters of %A.
20814 %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
20815 %b the first three characters of %B.
20816 %B one of ''January'', ''February'', ... , ''December''.
20817 %c equivalent to ''%a %b %e %T %Y''.
20818 %p one of ''AM'' or ''PM''.
20819 %r equivalent to ''%I:%M:%S %p''.
20820 %x equivalent to ''%m/%d/%y''.
20821 %X equivalent to %T.
20822 %Z implementation-defined.
20823 <p><b>Returns</b>
20824 <p><!--para 8 -->
20825 If the total number of resulting characters including the terminating null character is not
20826 more than maxsize, the strftime function returns the number of characters placed
20827 into the array pointed to by s not including the terminating null character. Otherwise,
20828 zero is returned and the contents of the array are indeterminate.
20829 <!--page 416 -->
20833 <p><!--para 1 -->
20834 The header <a href="#7.28"><uchar.h></a> declares types and functions for manipulating Unicode
20835 characters.
20836 <p><!--para 2 -->
20837 The types declared are mbstate_t (described in <a href="#7.30.1">7.30.1</a>) and size_t (described in
20839 <pre>
20840 char16_t
20841 </pre>
20842 which is an unsigned integer type used for 16-bit characters and is the same type as
20844 <pre>
20845 char32_t
20846 </pre>
20847 which is an unsigned integer type used for 32-bit characters and is the same type as
20851 <h4><a name="7.28.1" href="#7.28.1">7.28.1 Restartable multibyte/wide character conversion functions</a></h4>
20852 <p><!--para 1 -->
20853 These functions have a parameter, ps, of type pointer to mbstate_t that points to an
20854 object that can completely describe the current conversion state of the associated
20855 multibyte character sequence, which the functions alter as necessary. If ps is a null
20856 pointer, each function uses its own internal mbstate_t object instead, which is
20857 initialized at program startup to the initial conversion state; the functions are not required
20858 to avoid data races with other calls to the same function in this case. The implementation
20859 behaves as if no library function calls these functions with a null pointer for ps.
20863 <p><b>Synopsis</b>
20864 <p><!--para 1 -->
20865 <pre>
20867 size_t mbrtoc16(char16_t * restrict pc16,
20868 const char * restrict s, size_t n,
20869 mbstate_t * restrict ps);
20870 </pre>
20871 <p><b>Description</b>
20872 <p><!--para 2 -->
20873 If s is a null pointer, the mbrtoc16 function is equivalent to the call:
20874 <pre>
20876 </pre>
20877 In this case, the values of the parameters pc16 and n are ignored.
20878 <p><!--para 3 -->
20879 If s is not a null pointer, the mbrtoc16 function inspects at most n bytes beginning with
20880 the byte pointed to by s to determine the number of bytes needed to complete the next
20881 multibyte character (including any shift sequences). If the function determines that the
20882 next multibyte character is complete and valid, it determines the values of the
20883 corresponding wide characters and then, if pc16 is not a null pointer, stores the value of
20884 the first (or only) such character in the object pointed to by pc16. Subsequent calls will
20885 <!--page 417 -->
20886 store successive wide characters without consuming any additional input until all the
20887 characters have been stored. If the corresponding wide character is the null wide
20888 character, the resulting state described is the initial conversion state.
20889 <p><b>Returns</b>
20890 <p><!--para 4 -->
20891 The mbrtoc16 function returns the first of the following that applies (given the current
20892 conversion state):
20893 0 if the next n or fewer bytes complete the multibyte character that
20894 <pre>
20895 corresponds to the null wide character (which is the value stored).
20896 </pre>
20897 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
20898 <pre>
20899 character (which is the value stored); the value returned is the number
20900 of bytes that complete the multibyte character.
20901 </pre>
20902 (size_t)(-3) if the next character resulting from a previous call has been stored (no
20903 <pre>
20904 bytes from the input have been consumed by this call).
20905 </pre>
20906 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
20907 <pre>
20908 multibyte character, and all n bytes have been processed (no value is
20910 </pre>
20911 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
20912 <pre>
20913 do not contribute to a complete and valid multibyte character (no
20914 value is stored); the value of the macro EILSEQ is stored in errno,
20915 and the conversion state is unspecified.
20916 </pre>
20918 <p><b>Footnotes</b>
20919 <p><small><a name="note324" href="#note324">324)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
20920 sequence of redundant shift sequences (for implementations with state-dependent encodings).
20921 </small>
20925 <p><b>Synopsis</b>
20926 <p><!--para 1 -->
20927 <pre>
20929 size_t c16rtomb(char * restrict s, char16_t c16,
20930 mbstate_t * restrict ps);
20931 </pre>
20932 <p><b>Description</b>
20933 <p><!--para 2 -->
20934 If s is a null pointer, the c16rtomb function is equivalent to the call
20935 <pre>
20936 c16rtomb(buf, L'\0', ps)
20937 </pre>
20938 where buf is an internal buffer.
20939 <p><!--para 3 -->
20940 If s is not a null pointer, the c16rtomb function determines the number of bytes needed
20941 to represent the multibyte character that corresponds to the wide character given by c16
20942 (including any shift sequences), and stores the multibyte character representation in the
20944 <!--page 418 -->
20945 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
20946 c16 is a null wide character, a null byte is stored, preceded by any shift sequence needed
20947 to restore the initial shift state; the resulting state described is the initial conversion state.
20948 <p><b>Returns</b>
20949 <p><!--para 4 -->
20950 The c16rtomb function returns the number of bytes stored in the array object (including
20951 any shift sequences). When c16 is not a valid wide character, an encoding error occurs:
20952 the function stores the value of the macro EILSEQ in errno and returns
20953 (size_t)(-1); the conversion state is unspecified.
20957 <p><b>Synopsis</b>
20958 <p><!--para 1 -->
20959 <pre>
20961 size_t mbrtoc32(char32_t * restrict pc32,
20962 const char * restrict s, size_t n,
20963 mbstate_t * restrict ps);
20964 </pre>
20965 <p><b>Description</b>
20966 <p><!--para 2 -->
20967 If s is a null pointer, the mbrtoc32 function is equivalent to the call:
20968 <pre>
20970 </pre>
20971 In this case, the values of the parameters pc32 and n are ignored.
20972 <p><!--para 3 -->
20973 If s is not a null pointer, the mbrtoc32 function inspects at most n bytes beginning with
20974 the byte pointed to by s to determine the number of bytes needed to complete the next
20975 multibyte character (including any shift sequences). If the function determines that the
20976 next multibyte character is complete and valid, it determines the values of the
20977 corresponding wide characters and then, if pc32 is not a null pointer, stores the value of
20978 the first (or only) such character in the object pointed to by pc32. Subsequent calls will
20979 store successive wide characters without consuming any additional input until all the
20980 characters have been stored. If the corresponding wide character is the null wide
20981 character, the resulting state described is the initial conversion state.
20982 <p><b>Returns</b>
20983 <p><!--para 4 -->
20984 The mbrtoc32 function returns the first of the following that applies (given the current
20985 conversion state):
20986 0 if the next n or fewer bytes complete the multibyte character that
20987 <pre>
20988 corresponds to the null wide character (which is the value stored).
20989 </pre>
20990 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
20991 <!--page 419 -->
20992 <pre>
20993 character (which is the value stored); the value returned is the number
20994 of bytes that complete the multibyte character.
20995 </pre>
20996 (size_t)(-3) if the next character resulting from a previous call has been stored (no
20997 <pre>
20998 bytes from the input have been consumed by this call).
20999 </pre>
21000 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
21001 <pre>
21002 multibyte character, and all n bytes have been processed (no value is
21004 </pre>
21005 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
21006 <pre>
21007 do not contribute to a complete and valid multibyte character (no
21008 value is stored); the value of the macro EILSEQ is stored in errno,
21009 and the conversion state is unspecified.
21010 </pre>
21012 <p><b>Footnotes</b>
21013 <p><small><a name="note325" href="#note325">325)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
21014 sequence of redundant shift sequences (for implementations with state-dependent encodings).
21015 </small>
21019 <p><b>Synopsis</b>
21020 <p><!--para 1 -->
21021 <pre>
21023 size_t c32rtomb(char * restrict s, char32_t c32,
21024 mbstate_t * restrict ps);
21025 </pre>
21026 <p><b>Description</b>
21027 <p><!--para 2 -->
21028 If s is a null pointer, the c32rtomb function is equivalent to the call
21029 <pre>
21030 c32rtomb(buf, L'\0', ps)
21031 </pre>
21032 where buf is an internal buffer.
21033 <p><!--para 3 -->
21034 If s is not a null pointer, the c32rtomb function determines the number of bytes needed
21035 to represent the multibyte character that corresponds to the wide character given by c32
21036 (including any shift sequences), and stores the multibyte character representation in the
21037 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
21038 c32 is a null wide character, a null byte is stored, preceded by any shift sequence needed
21039 to restore the initial shift state; the resulting state described is the initial conversion state.
21040 <p><b>Returns</b>
21041 <p><!--para 4 -->
21042 The c32rtomb function returns the number of bytes stored in the array object (including
21043 any shift sequences). When c32 is not a valid wide character, an encoding error occurs:
21044 the function stores the value of the macro EILSEQ in errno and returns
21045 (size_t)(-1); the conversion state is unspecified.
21050 <!--page 420 -->
21053 <h3><a name="7.29" href="#7.29">7.29 Extended multibyte and wide character utilities <wchar.h></a></h3>
21057 <p><!--para 1 -->
21058 The header <a href="#7.29"><wchar.h></a> defines four macros, and declares four data types, one tag, and
21060 <p><!--para 2 -->
21062 <pre>
21063 mbstate_t
21064 </pre>
21065 which is a complete object type other than an array type that can hold the conversion state
21066 information necessary to convert between sequences of multibyte characters and wide
21067 characters;
21068 <pre>
21069 wint_t
21070 </pre>
21071 which is an integer type unchanged by default argument promotions that can hold any
21072 value corresponding to members of the extended character set, as well as at least one
21073 value that does not correspond to any member of the extended character set (see WEOF
21075 <pre>
21076 struct tm
21077 </pre>
21078 which is declared as an incomplete structure type (the contents are described in <a href="#7.27.1">7.27.1</a>).
21079 <p><!--para 3 -->
21082 <pre>
21083 WEOF
21084 </pre>
21085 which expands to a constant expression of type wint_t whose value does not
21086 correspond to any member of the extended character set.<sup><a href="#note328"><b>328)</b></a></sup> It is accepted (and returned)
21087 by several functions in this subclause to indicate end-of-file, that is, no more input from a
21088 stream. It is also used as a wide character value that does not correspond to any member
21089 of the extended character set.
21090 <p><!--para 4 -->
21091 The functions declared are grouped as follows:
21092 <ul>
21093 <li> Functions that perform input and output of wide characters, or multibyte characters,
21094 or both;
21095 <li> Functions that provide wide string numeric conversion;
21096 <li> Functions that perform general wide string manipulation;
21099 <!--page 421 -->
21100 <li> Functions for wide string date and time conversion; and
21101 <li> Functions that provide extended capabilities for conversion between multibyte and
21102 wide character sequences.
21103 </ul>
21104 <p><!--para 5 -->
21105 Arguments to the functions in this subclause may point to arrays containing wchar_t
21106 values that do not correspond to members of the extended character set. Such values
21107 shall be processed according to the specified semantics, except that it is unspecified
21108 whether an encoding error occurs if such a value appears in the format string for a
21109 function in <a href="#7.29.2">7.29.2</a> or <a href="#7.29.5">7.29.5</a> and the specified semantics do not require that value to be
21110 processed by wcrtomb.
21111 <p><!--para 6 -->
21112 Unless explicitly stated otherwise, if the execution of a function described in this
21113 subclause causes copying to take place between objects that overlap, the behavior is
21114 undefined.
21116 <p><b>Footnotes</b>
21117 <p><small><a name="note326" href="#note326">326)</a> See ''future library directions'' (<a href="#7.31.16">7.31.16</a>).
21118 </small>
21119 <p><small><a name="note327" href="#note327">327)</a> wchar_t and wint_t can be the same integer type.
21120 </small>
21121 <p><small><a name="note328" href="#note328">328)</a> The value of the macro WEOF may differ from that of EOF and need not be negative.
21122 </small>
21125 <h4><a name="7.29.2" href="#7.29.2">7.29.2 Formatted wide character input/output functions</a></h4>
21126 <p><!--para 1 -->
21127 The formatted wide character input/output functions shall behave as if there is a sequence
21128 point after the actions associated with each specifier.<sup><a href="#note329"><b>329)</b></a></sup>
21130 <p><b>Footnotes</b>
21131 <p><small><a name="note329" href="#note329">329)</a> The fwprintf functions perform writes to memory for the %n specifier.
21132 </small>
21136 <p><b>Synopsis</b>
21137 <p><!--para 1 -->
21138 <pre>
21141 int fwprintf(FILE * restrict stream,
21142 const wchar_t * restrict format, ...);
21143 </pre>
21144 <p><b>Description</b>
21145 <p><!--para 2 -->
21146 The fwprintf function writes output to the stream pointed to by stream, under
21147 control of the wide string pointed to by format that specifies how subsequent arguments
21148 are converted for output. If there are insufficient arguments for the format, the behavior
21149 is undefined. If the format is exhausted while arguments remain, the excess arguments
21150 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
21151 when the end of the format string is encountered.
21152 <p><!--para 3 -->
21153 The format is composed of zero or more directives: ordinary wide characters (not %),
21154 which are copied unchanged to the output stream; and conversion specifications, each of
21155 which results in fetching zero or more subsequent arguments, converting them, if
21156 applicable, according to the corresponding conversion specifier, and then writing the
21157 result to the output stream.
21161 <!--page 422 -->
21162 <p><!--para 4 -->
21163 Each conversion specification is introduced by the wide character %. After the %, the
21164 following appear in sequence:
21165 <ul>
21166 <li> Zero or more flags (in any order) that modify the meaning of the conversion
21167 specification.
21168 <li> An optional minimum field width. If the converted value has fewer wide characters
21169 than the field width, it is padded with spaces (by default) on the left (or right, if the
21170 left adjustment flag, described later, has been given) to the field width. The field
21171 width takes the form of an asterisk * (described later) or a nonnegative decimal
21173 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
21174 o, u, x, and X conversions, the number of digits to appear after the decimal-point
21175 wide character for a, A, e, E, f, and F conversions, the maximum number of
21176 significant digits for the g and G conversions, or the maximum number of wide
21177 characters to be written for s conversions. The precision takes the form of a period
21178 (.) followed either by an asterisk * (described later) or by an optional decimal
21179 integer; if only the period is specified, the precision is taken as zero. If a precision
21180 appears with any other conversion specifier, the behavior is undefined.
21181 <li> An optional length modifier that specifies the size of the argument.
21182 <li> A conversion specifier wide character that specifies the type of conversion to be
21183 applied.
21184 </ul>
21185 <p><!--para 5 -->
21186 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
21187 this case, an int argument supplies the field width or precision. The arguments
21188 specifying field width, or precision, or both, shall appear (in that order) before the
21189 argument (if any) to be converted. A negative field width argument is taken as a - flag
21190 followed by a positive field width. A negative precision argument is taken as if the
21191 precision were omitted.
21192 <p><!--para 6 -->
21193 The flag wide characters and their meanings are:
21194 - The result of the conversion is left-justified within the field. (It is right-justified if
21195 <pre>
21196 this flag is not specified.)
21197 </pre>
21198 + The result of a signed conversion always begins with a plus or minus sign. (It
21199 <pre>
21200 begins with a sign only when a negative value is converted if this flag is not
21201 </pre>
21206 <!--page 423 -->
21207 <pre>
21209 </pre>
21210 space If the first wide character of a signed conversion is not a sign, or if a signed
21211 <pre>
21212 conversion results in no wide characters, a space is prefixed to the result. If the
21213 space and + flags both appear, the space flag is ignored.
21214 </pre>
21215 # The result is converted to an ''alternative form''. For o conversion, it increases
21216 <pre>
21217 the precision, if and only if necessary, to force the first digit of the result to be a
21218 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
21219 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
21220 and G conversions, the result of converting a floating-point number always
21221 contains a decimal-point wide character, even if no digits follow it. (Normally, a
21222 decimal-point wide character appears in the result of these conversions only if a
21223 digit follows it.) For g and G conversions, trailing zeros are not removed from the
21224 result. For other conversions, the behavior is undefined.
21225 </pre>
21226 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
21227 <pre>
21228 (following any indication of sign or base) are used to pad to the field width rather
21229 than performing space padding, except when converting an infinity or NaN. If the
21230 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
21231 conversions, if a precision is specified, the 0 flag is ignored. For other
21232 conversions, the behavior is undefined.
21233 </pre>
21234 <p><!--para 7 -->
21235 The length modifiers and their meanings are:
21236 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21237 <pre>
21238 signed char or unsigned char argument (the argument will have
21239 been promoted according to the integer promotions, but its value shall be
21240 converted to signed char or unsigned char before printing); or that
21241 a following n conversion specifier applies to a pointer to a signed char
21242 argument.
21243 </pre>
21244 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21245 <pre>
21246 short int or unsigned short int argument (the argument will
21247 have been promoted according to the integer promotions, but its value shall
21248 be converted to short int or unsigned short int before printing);
21249 or that a following n conversion specifier applies to a pointer to a short
21250 int argument.
21251 </pre>
21252 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21253 <pre>
21254 long int or unsigned long int argument; that a following n
21255 conversion specifier applies to a pointer to a long int argument; that a
21256 </pre>
21259 <!--page 424 -->
21260 <pre>
21261 following c conversion specifier applies to a wint_t argument; that a
21262 following s conversion specifier applies to a pointer to a wchar_t
21263 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
21264 specifier.
21265 </pre>
21266 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21267 <pre>
21268 long long int or unsigned long long int argument; or that a
21269 following n conversion specifier applies to a pointer to a long long int
21270 argument.
21271 </pre>
21272 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
21273 <pre>
21274 an intmax_t or uintmax_t argument; or that a following n conversion
21275 specifier applies to a pointer to an intmax_t argument.
21276 </pre>
21277 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21278 <pre>
21279 size_t or the corresponding signed integer type argument; or that a
21280 following n conversion specifier applies to a pointer to a signed integer type
21281 corresponding to size_t argument.
21282 </pre>
21283 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21284 <pre>
21285 ptrdiff_t or the corresponding unsigned integer type argument; or that a
21286 following n conversion specifier applies to a pointer to a ptrdiff_t
21287 argument.
21288 </pre>
21289 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
21290 <pre>
21291 applies to a long double argument.
21292 </pre>
21293 If a length modifier appears with any conversion specifier other than as specified above,
21294 the behavior is undefined.
21295 <p><!--para 8 -->
21296 The conversion specifiers and their meanings are:
21297 d,i The int argument is converted to signed decimal in the style [-]dddd. The
21298 <pre>
21299 precision specifies the minimum number of digits to appear; if the value
21300 being converted can be represented in fewer digits, it is expanded with
21301 leading zeros. The default precision is 1. The result of converting a zero
21302 value with a precision of zero is no wide characters.
21303 </pre>
21304 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
21305 <!--page 425 -->
21306 <pre>
21307 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
21308 letters abcdef are used for x conversion and the letters ABCDEF for X
21309 conversion. The precision specifies the minimum number of digits to appear;
21310 if the value being converted can be represented in fewer digits, it is expanded
21311 with leading zeros. The default precision is 1. The result of converting a
21312 zero value with a precision of zero is no wide characters.
21313 </pre>
21314 f,F A double argument representing a floating-point number is converted to
21315 <pre>
21316 decimal notation in the style [-]ddd.ddd, where the number of digits after
21317 the decimal-point wide character is equal to the precision specification. If the
21318 precision is missing, it is taken as 6; if the precision is zero and the # flag is
21319 not specified, no decimal-point wide character appears. If a decimal-point
21320 wide character appears, at least one digit appears before it. The value is
21321 rounded to the appropriate number of digits.
21322 A double argument representing an infinity is converted in one of the styles
21323 [-]inf or [-]infinity -- which style is implementation-defined. A
21324 double argument representing a NaN is converted in one of the styles
21325 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
21326 any n-wchar-sequence, is implementation-defined. The F conversion
21327 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
21329 </pre>
21330 e,E A double argument representing a floating-point number is converted in the
21331 <pre>
21332 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
21333 argument is nonzero) before the decimal-point wide character and the number
21334 of digits after it is equal to the precision; if the precision is missing, it is taken
21335 as 6; if the precision is zero and the # flag is not specified, no decimal-point
21336 wide character appears. The value is rounded to the appropriate number of
21337 digits. The E conversion specifier produces a number with E instead of e
21338 introducing the exponent. The exponent always contains at least two digits,
21339 and only as many more digits as necessary to represent the exponent. If the
21340 value is zero, the exponent is zero.
21341 A double argument representing an infinity or NaN is converted in the style
21342 of an f or F conversion specifier.
21343 </pre>
21344 g,G A double argument representing a floating-point number is converted in
21345 <pre>
21346 style f or e (or in style F or E in the case of a G conversion specifier),
21347 depending on the value converted and the precision. Let P equal the
21348 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
21349 Then, if a conversion with style E would have an exponent of X:
21350 -- if P > X >= -4, the conversion is with style f (or F) and precision
21351 P - (X + 1).
21352 -- otherwise, the conversion is with style e (or E) and precision P - 1.
21353 Finally, unless the # flag is used, any trailing zeros are removed from the
21354 </pre>
21357 <!--page 426 -->
21358 <pre>
21359 fractional portion of the result and the decimal-point wide character is
21360 removed if there is no fractional portion remaining.
21361 A double argument representing an infinity or NaN is converted in the style
21362 of an f or F conversion specifier.
21363 </pre>
21364 a,A A double argument representing a floating-point number is converted in the
21365 <pre>
21366 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
21367 nonzero if the argument is a normalized floating-point number and is
21368 otherwise unspecified) before the decimal-point wide character<sup><a href="#note333"><b>333)</b></a></sup> and the
21369 number of hexadecimal digits after it is equal to the precision; if the precision
21370 is missing and FLT_RADIX is a power of 2, then the precision is sufficient
21371 for an exact representation of the value; if the precision is missing and
21372 FLT_RADIX is not a power of 2, then the precision is sufficient to
21373 distinguish<sup><a href="#note334"><b>334)</b></a></sup> values of type double, except that trailing zeros may be
21374 omitted; if the precision is zero and the # flag is not specified, no decimal-
21375 point wide character appears. The letters abcdef are used for a conversion
21376 and the letters ABCDEF for A conversion. The A conversion specifier
21377 produces a number with X and P instead of x and p. The exponent always
21378 contains at least one digit, and only as many more digits as necessary to
21379 represent the decimal exponent of 2. If the value is zero, the exponent is
21380 zero.
21381 A double argument representing an infinity or NaN is converted in the style
21382 of an f or F conversion specifier.
21383 </pre>
21384 c If no l length modifier is present, the int argument is converted to a wide
21385 <pre>
21386 character as if by calling btowc and the resulting wide character is written.
21387 If an l length modifier is present, the wint_t argument is converted to
21388 wchar_t and written.
21389 </pre>
21390 s If no l length modifier is present, the argument shall be a pointer to the initial
21391 <pre>
21392 element of a character array containing a multibyte character sequence
21393 beginning in the initial shift state. Characters from the array are converted as
21394 if by repeated calls to the mbrtowc function, with the conversion state
21395 described by an mbstate_t object initialized to zero before the first
21396 multibyte character is converted, and written up to (but not including) the
21397 </pre>
21399 <!--page 427 -->
21400 <pre>
21401 terminating null wide character. If the precision is specified, no more than
21402 that many wide characters are written. If the precision is not specified or is
21403 greater than the size of the converted array, the converted array shall contain a
21404 null wide character.
21405 If an l length modifier is present, the argument shall be a pointer to the initial
21406 element of an array of wchar_t type. Wide characters from the array are
21407 written up to (but not including) a terminating null wide character. If the
21408 precision is specified, no more than that many wide characters are written. If
21409 the precision is not specified or is greater than the size of the array, the array
21410 shall contain a null wide character.
21411 </pre>
21412 p The argument shall be a pointer to void. The value of the pointer is
21413 <pre>
21414 converted to a sequence of printing wide characters, in an implementation-
21415 defined manner.
21416 </pre>
21417 n The argument shall be a pointer to signed integer into which is written the
21418 <pre>
21419 number of wide characters written to the output stream so far by this call to
21420 fwprintf. No argument is converted, but one is consumed. If the
21421 conversion specification includes any flags, a field width, or a precision, the
21422 behavior is undefined.
21423 </pre>
21424 % A % wide character is written. No argument is converted. The complete
21425 <pre>
21426 conversion specification shall be %%.
21427 </pre>
21428 <p><!--para 9 -->
21429 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note335"><b>335)</b></a></sup> If any argument is
21430 not the correct type for the corresponding conversion specification, the behavior is
21431 undefined.
21432 <p><!--para 10 -->
21433 In no case does a nonexistent or small field width cause truncation of a field; if the result
21434 of a conversion is wider than the field width, the field is expanded to contain the
21435 conversion result.
21436 <p><!--para 11 -->
21437 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
21438 to a hexadecimal floating number with the given precision.
21439 <p><b>Recommended practice</b>
21440 <p><!--para 12 -->
21441 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
21442 representable in the given precision, the result should be one of the two adjacent numbers
21443 in hexadecimal floating style with the given precision, with the extra stipulation that the
21444 error should have a correct sign for the current rounding direction.
21445 <p><!--para 13 -->
21446 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
21447 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note336"><b>336)</b></a></sup> If the number of
21449 <!--page 428 -->
21450 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
21451 representable with DECIMAL_DIG digits, then the result should be an exact
21452 representation with trailing zeros. Otherwise, the source value is bounded by two
21453 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
21454 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
21455 the error should have a correct sign for the current rounding direction.
21456 <p><b>Returns</b>
21457 <p><!--para 14 -->
21458 The fwprintf function returns the number of wide characters transmitted, or a negative
21459 value if an output or encoding error occurred.
21460 <p><b>Environmental limits</b>
21461 <p><!--para 15 -->
21462 The number of wide characters that can be produced by any single conversion shall be at
21463 least 4095.
21464 <p><!--para 16 -->
21465 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
21466 places:
21467 <pre>
21471 /* ... */
21472 wchar_t *weekday, *month; // pointers to wide strings
21473 int day, hour, min;
21475 weekday, month, day, hour, min);
21477 </pre>
21479 <p><b> Forward references</b>: the btowc function (<a href="#7.29.6.1.1">7.29.6.1.1</a>), the mbrtowc function
21482 <p><b>Footnotes</b>
21483 <p><small><a name="note330" href="#note330">330)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
21484 </small>
21485 <p><small><a name="note331" href="#note331">331)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
21486 include a minus sign.
21487 </small>
21488 <p><small><a name="note332" href="#note332">332)</a> When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
21489 meaning; the # and 0 flag wide characters have no effect.
21490 </small>
21491 <p><small><a name="note333" href="#note333">333)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
21492 character so that subsequent digits align to nibble (4-bit) boundaries.
21493 </small>
21494 <p><small><a name="note334" href="#note334">334)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
21495 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
21496 might suffice depending on the implementation's scheme for determining the digit to the left of the
21497 decimal-point wide character.
21498 </small>
21499 <p><small><a name="note335" href="#note335">335)</a> See ''future library directions'' (<a href="#7.31.16">7.31.16</a>).
21500 </small>
21501 <p><small><a name="note336" href="#note336">336)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
21502 given format specifier. The number of significant digits is determined by the format specifier, and in
21503 the case of fixed-point conversion by the source value as well.
21504 </small>
21508 <p><b>Synopsis</b>
21509 <p><!--para 1 -->
21510 <pre>
21513 int fwscanf(FILE * restrict stream,
21514 const wchar_t * restrict format, ...);
21515 </pre>
21516 <p><b>Description</b>
21517 <p><!--para 2 -->
21518 The fwscanf function reads input from the stream pointed to by stream, under
21519 control of the wide string pointed to by format that specifies the admissible input
21520 sequences and how they are to be converted for assignment, using subsequent arguments
21522 <!--page 429 -->
21523 as pointers to the objects to receive the converted input. If there are insufficient
21524 arguments for the format, the behavior is undefined. If the format is exhausted while
21525 arguments remain, the excess arguments are evaluated (as always) but are otherwise
21526 ignored.
21527 <p><!--para 3 -->
21528 The format is composed of zero or more directives: one or more white-space wide
21529 characters, an ordinary wide character (neither % nor a white-space wide character), or a
21530 conversion specification. Each conversion specification is introduced by the wide
21531 character %. After the %, the following appear in sequence:
21532 <ul>
21533 <li> An optional assignment-suppressing wide character *.
21534 <li> An optional decimal integer greater than zero that specifies the maximum field width
21535 (in wide characters).
21536 <li> An optional length modifier that specifies the size of the receiving object.
21537 <li> A conversion specifier wide character that specifies the type of conversion to be
21538 applied.
21539 </ul>
21540 <p><!--para 4 -->
21541 The fwscanf function executes each directive of the format in turn. When all directives
21542 have been executed, or if a directive fails (as detailed below), the function returns.
21543 Failures are described as input failures (due to the occurrence of an encoding error or the
21544 unavailability of input characters), or matching failures (due to inappropriate input).
21545 <p><!--para 5 -->
21546 A directive composed of white-space wide character(s) is executed by reading input up to
21547 the first non-white-space wide character (which remains unread), or until no more wide
21548 characters can be read. The directive never fails.
21549 <p><!--para 6 -->
21550 A directive that is an ordinary wide character is executed by reading the next wide
21551 character of the stream. If that wide character differs from the directive, the directive
21552 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
21553 of-file, an encoding error, or a read error prevents a wide character from being read, the
21554 directive fails.
21555 <p><!--para 7 -->
21556 A directive that is a conversion specification defines a set of matching input sequences, as
21557 described below for each specifier. A conversion specification is executed in the
21558 following steps:
21559 <p><!--para 8 -->
21560 Input white-space wide characters (as specified by the iswspace function) are skipped,
21561 unless the specification includes a [, c, or n specifier.<sup><a href="#note337"><b>337)</b></a></sup>
21562 <p><!--para 9 -->
21563 An input item is read from the stream, unless the specification includes an n specifier. An
21564 input item is defined as the longest sequence of input wide characters which does not
21565 exceed any specified field width and which is, or is a prefix of, a matching input
21568 <!--page 430 -->
21569 sequence.<sup><a href="#note338"><b>338)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
21570 length of the input item is zero, the execution of the directive fails; this condition is a
21571 matching failure unless end-of-file, an encoding error, or a read error prevented input
21572 from the stream, in which case it is an input failure.
21573 <p><!--para 10 -->
21574 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
21575 count of input wide characters) is converted to a type appropriate to the conversion
21576 specifier. If the input item is not a matching sequence, the execution of the directive fails:
21577 this condition is a matching failure. Unless assignment suppression was indicated by a *,
21578 the result of the conversion is placed in the object pointed to by the first argument
21579 following the format argument that has not already received a conversion result. If this
21580 object does not have an appropriate type, or if the result of the conversion cannot be
21581 represented in the object, the behavior is undefined.
21582 <p><!--para 11 -->
21583 The length modifiers and their meanings are:
21584 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21585 <pre>
21586 to an argument with type pointer to signed char or unsigned char.
21587 </pre>
21588 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21589 <pre>
21590 to an argument with type pointer to short int or unsigned short
21591 int.
21592 </pre>
21593 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21594 <pre>
21595 to an argument with type pointer to long int or unsigned long
21596 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
21597 an argument with type pointer to double; or that a following c, s, or [
21598 conversion specifier applies to an argument with type pointer to wchar_t.
21599 </pre>
21600 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21601 <pre>
21602 to an argument with type pointer to long long int or unsigned
21603 long long int.
21604 </pre>
21605 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21606 <pre>
21607 to an argument with type pointer to intmax_t or uintmax_t.
21608 </pre>
21609 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21610 <pre>
21611 to an argument with type pointer to size_t or the corresponding signed
21612 integer type.
21613 </pre>
21614 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21615 <pre>
21616 to an argument with type pointer to ptrdiff_t or the corresponding
21617 unsigned integer type.
21618 </pre>
21621 <!--page 431 -->
21622 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
21623 <pre>
21624 applies to an argument with type pointer to long double.
21625 </pre>
21626 If a length modifier appears with any conversion specifier other than as specified above,
21627 the behavior is undefined.
21628 <p><!--para 12 -->
21629 The conversion specifiers and their meanings are:
21630 d Matches an optionally signed decimal integer, whose format is the same as
21631 <pre>
21632 expected for the subject sequence of the wcstol function with the value 10
21633 for the base argument. The corresponding argument shall be a pointer to
21634 signed integer.
21635 </pre>
21636 i Matches an optionally signed integer, whose format is the same as expected
21637 <pre>
21638 for the subject sequence of the wcstol function with the value 0 for the
21639 base argument. The corresponding argument shall be a pointer to signed
21640 integer.
21641 </pre>
21642 o Matches an optionally signed octal integer, whose format is the same as
21643 <pre>
21644 expected for the subject sequence of the wcstoul function with the value 8
21645 for the base argument. The corresponding argument shall be a pointer to
21646 unsigned integer.
21647 </pre>
21648 u Matches an optionally signed decimal integer, whose format is the same as
21649 <pre>
21650 expected for the subject sequence of the wcstoul function with the value 10
21651 for the base argument. The corresponding argument shall be a pointer to
21652 unsigned integer.
21653 </pre>
21654 x Matches an optionally signed hexadecimal integer, whose format is the same
21655 <pre>
21656 as expected for the subject sequence of the wcstoul function with the value
21657 16 for the base argument. The corresponding argument shall be a pointer to
21658 unsigned integer.
21659 </pre>
21660 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
21661 <pre>
21662 format is the same as expected for the subject sequence of the wcstod
21663 function. The corresponding argument shall be a pointer to floating.
21664 </pre>
21665 c Matches a sequence of wide characters of exactly the number specified by the
21666 <!--page 432 -->
21667 <pre>
21668 field width (1 if no field width is present in the directive).
21669 If no l length modifier is present, characters from the input field are
21670 converted as if by repeated calls to the wcrtomb function, with the
21671 conversion state described by an mbstate_t object initialized to zero
21672 before the first wide character is converted. The corresponding argument
21673 shall be a pointer to the initial element of a character array large enough to
21674 accept the sequence. No null character is added.
21675 If an l length modifier is present, the corresponding argument shall be a
21676 pointer to the initial element of an array of wchar_t large enough to accept
21677 the sequence. No null wide character is added.
21678 </pre>
21679 s Matches a sequence of non-white-space wide characters.
21680 <pre>
21681 If no l length modifier is present, characters from the input field are
21682 converted as if by repeated calls to the wcrtomb function, with the
21683 conversion state described by an mbstate_t object initialized to zero
21684 before the first wide character is converted. The corresponding argument
21685 shall be a pointer to the initial element of a character array large enough to
21686 accept the sequence and a terminating null character, which will be added
21687 automatically.
21688 If an l length modifier is present, the corresponding argument shall be a
21689 pointer to the initial element of an array of wchar_t large enough to accept
21690 the sequence and the terminating null wide character, which will be added
21691 automatically.
21692 </pre>
21693 [ Matches a nonempty sequence of wide characters from a set of expected
21694 <!--page 433 -->
21695 <pre>
21696 characters (the scanset).
21697 If no l length modifier is present, characters from the input field are
21698 converted as if by repeated calls to the wcrtomb function, with the
21699 conversion state described by an mbstate_t object initialized to zero
21700 before the first wide character is converted. The corresponding argument
21701 shall be a pointer to the initial element of a character array large enough to
21702 accept the sequence and a terminating null character, which will be added
21703 automatically.
21704 If an l length modifier is present, the corresponding argument shall be a
21705 pointer to the initial element of an array of wchar_t large enough to accept
21706 the sequence and the terminating null wide character, which will be added
21707 automatically.
21708 The conversion specifier includes all subsequent wide characters in the
21709 format string, up to and including the matching right bracket (]). The wide
21710 characters between the brackets (the scanlist) compose the scanset, unless the
21711 wide character after the left bracket is a circumflex (^), in which case the
21712 scanset contains all wide characters that do not appear in the scanlist between
21713 the circumflex and the right bracket. If the conversion specifier begins with
21714 [] or [^], the right bracket wide character is in the scanlist and the next
21715 following right bracket wide character is the matching right bracket that ends
21716 the specification; otherwise the first following right bracket wide character is
21717 the one that ends the specification. If a - wide character is in the scanlist and
21718 is not the first, nor the second where the first wide character is a ^, nor the
21719 last character, the behavior is implementation-defined.
21720 </pre>
21721 p Matches an implementation-defined set of sequences, which should be the
21722 <pre>
21723 same as the set of sequences that may be produced by the %p conversion of
21724 the fwprintf function. The corresponding argument shall be a pointer to a
21725 pointer to void. The input item is converted to a pointer value in an
21726 implementation-defined manner. If the input item is a value converted earlier
21727 during the same program execution, the pointer that results shall compare
21728 equal to that value; otherwise the behavior of the %p conversion is undefined.
21729 </pre>
21730 n No input is consumed. The corresponding argument shall be a pointer to
21731 <pre>
21732 signed integer into which is to be written the number of wide characters read
21733 from the input stream so far by this call to the fwscanf function. Execution
21734 of a %n directive does not increment the assignment count returned at the
21735 completion of execution of the fwscanf function. No argument is
21736 converted, but one is consumed. If the conversion specification includes an
21737 assignment-suppressing wide character or a field width, the behavior is
21738 undefined.
21739 </pre>
21740 % Matches a single % wide character; no conversion or assignment occurs. The
21741 <pre>
21742 complete conversion specification shall be %%.
21743 </pre>
21744 <p><!--para 13 -->
21745 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note339"><b>339)</b></a></sup>
21746 <p><!--para 14 -->
21747 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
21748 respectively, a, e, f, g, and x.
21749 <p><!--para 15 -->
21750 Trailing white space (including new-line wide characters) is left unread unless matched
21751 by a directive. The success of literal matches and suppressed assignments is not directly
21752 determinable other than via the %n directive.
21753 <p><b>Returns</b>
21754 <p><!--para 16 -->
21755 The fwscanf function returns the value of the macro EOF if an input failure occurs
21756 before the first conversion (if any) has completed. Otherwise, the function returns the
21757 number of input items assigned, which can be fewer than provided for, or even zero, in
21758 the event of an early matching failure.
21759 <p><!--para 17 -->
21760 EXAMPLE 1 The call:
21761 <pre>
21764 /* ... */
21765 int n, i; float x; wchar_t name[50];
21767 </pre>
21771 <!--page 434 -->
21772 with the input line:
21773 <pre>
21774 25 54.32E-1 thompson
21775 </pre>
21776 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
21777 thompson\0.
21779 <p><!--para 18 -->
21780 EXAMPLE 2 The call:
21781 <pre>
21784 /* ... */
21785 int i; float x; double y;
21787 </pre>
21788 with input:
21789 <pre>
21790 56789 0123 56a72
21791 </pre>
21792 will assign to i the value 56 and to x the value 789.0, will skip past 0123, and will assign to y the value
21793 56.0. The next wide character read from the input stream will be a.
21795 <p><b> Forward references</b>: the wcstod, wcstof, and wcstold functions (<a href="#7.29.4.1.1">7.29.4.1.1</a>), the
21796 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.29.4.1.2">7.29.4.1.2</a>), the wcrtomb
21799 <p><b>Footnotes</b>
21800 <p><small><a name="note337" href="#note337">337)</a> These white-space wide characters are not counted against a specified field width.
21801 </small>
21802 <p><small><a name="note338" href="#note338">338)</a> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
21803 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
21804 </small>
21805 <p><small><a name="note339" href="#note339">339)</a> See ''future library directions'' (<a href="#7.31.16">7.31.16</a>).
21806 </small>
21810 <p><b>Synopsis</b>
21811 <p><!--para 1 -->
21812 <pre>
21814 int swprintf(wchar_t * restrict s,
21815 size_t n,
21816 const wchar_t * restrict format, ...);
21817 </pre>
21818 <p><b>Description</b>
21819 <p><!--para 2 -->
21820 The swprintf function is equivalent to fwprintf, except that the argument s
21821 specifies an array of wide characters into which the generated output is to be written,
21822 rather than written to a stream. No more than n wide characters are written, including a
21823 terminating null wide character, which is always added (unless n is zero).
21824 <p><b>Returns</b>
21825 <p><!--para 3 -->
21826 The swprintf function returns the number of wide characters written in the array, not
21827 counting the terminating null wide character, or a negative value if an encoding error
21828 occurred or if n or more wide characters were requested to be written.
21829 <!--page 435 -->
21833 <p><b>Synopsis</b>
21834 <p><!--para 1 -->
21835 <pre>
21837 int swscanf(const wchar_t * restrict s,
21838 const wchar_t * restrict format, ...);
21839 </pre>
21840 <p><b>Description</b>
21841 <p><!--para 2 -->
21842 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
21843 wide string from which the input is to be obtained, rather than from a stream. Reaching
21844 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
21845 function.
21846 <p><b>Returns</b>
21847 <p><!--para 3 -->
21848 The swscanf function returns the value of the macro EOF if an input failure occurs
21849 before the first conversion (if any) has completed. Otherwise, the swscanf function
21850 returns the number of input items assigned, which can be fewer than provided for, or even
21851 zero, in the event of an early matching failure.
21855 <p><b>Synopsis</b>
21856 <p><!--para 1 -->
21857 <pre>
21861 int vfwprintf(FILE * restrict stream,
21862 const wchar_t * restrict format,
21863 va_list arg);
21864 </pre>
21865 <p><b>Description</b>
21866 <p><!--para 2 -->
21867 The vfwprintf function is equivalent to fwprintf, with the variable argument list
21868 replaced by arg, which shall have been initialized by the va_start macro (and
21869 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
21871 <p><b>Returns</b>
21872 <p><!--para 3 -->
21873 The vfwprintf function returns the number of wide characters transmitted, or a
21874 negative value if an output or encoding error occurred.
21879 <!--page 436 -->
21880 <p><!--para 4 -->
21881 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
21882 routine.
21883 <pre>
21887 void error(char *function_name, wchar_t *format, ...)
21888 {
21889 va_list args;
21890 va_start(args, format);
21891 // print out name of function causing error
21893 // print out remainder of message
21894 vfwprintf(stderr, format, args);
21895 va_end(args);
21896 }
21897 </pre>
21900 <p><b>Footnotes</b>
21901 <p><small><a name="note340" href="#note340">340)</a> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
21902 invoke the va_arg macro, the value of arg after the return is indeterminate.
21903 </small>
21907 <p><b>Synopsis</b>
21908 <p><!--para 1 -->
21909 <pre>
21913 int vfwscanf(FILE * restrict stream,
21914 const wchar_t * restrict format,
21915 va_list arg);
21916 </pre>
21917 <p><b>Description</b>
21918 <p><!--para 2 -->
21919 The vfwscanf function is equivalent to fwscanf, with the variable argument list
21920 replaced by arg, which shall have been initialized by the va_start macro (and
21921 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
21923 <p><b>Returns</b>
21924 <p><!--para 3 -->
21925 The vfwscanf function returns the value of the macro EOF if an input failure occurs
21926 before the first conversion (if any) has completed. Otherwise, the vfwscanf function
21927 returns the number of input items assigned, which can be fewer than provided for, or even
21928 zero, in the event of an early matching failure.
21929 <!--page 437 -->
21933 <p><b>Synopsis</b>
21934 <p><!--para 1 -->
21935 <pre>
21938 int vswprintf(wchar_t * restrict s,
21939 size_t n,
21940 const wchar_t * restrict format,
21941 va_list arg);
21942 </pre>
21943 <p><b>Description</b>
21944 <p><!--para 2 -->
21945 The vswprintf function is equivalent to swprintf, with the variable argument list
21946 replaced by arg, which shall have been initialized by the va_start macro (and
21947 possibly subsequent va_arg calls). The vswprintf function does not invoke the
21949 <p><b>Returns</b>
21950 <p><!--para 3 -->
21951 The vswprintf function returns the number of wide characters written in the array, not
21952 counting the terminating null wide character, or a negative value if an encoding error
21953 occurred or if n or more wide characters were requested to be generated.
21957 <p><b>Synopsis</b>
21958 <p><!--para 1 -->
21959 <pre>
21962 int vswscanf(const wchar_t * restrict s,
21963 const wchar_t * restrict format,
21964 va_list arg);
21965 </pre>
21966 <p><b>Description</b>
21967 <p><!--para 2 -->
21968 The vswscanf function is equivalent to swscanf, with the variable argument list
21969 replaced by arg, which shall have been initialized by the va_start macro (and
21970 possibly subsequent va_arg calls). The vswscanf function does not invoke the
21972 <p><b>Returns</b>
21973 <p><!--para 3 -->
21974 The vswscanf function returns the value of the macro EOF if an input failure occurs
21975 before the first conversion (if any) has completed. Otherwise, the vswscanf function
21976 returns the number of input items assigned, which can be fewer than provided for, or even
21977 zero, in the event of an early matching failure.
21978 <!--page 438 -->
21982 <p><b>Synopsis</b>
21983 <p><!--para 1 -->
21984 <pre>
21987 int vwprintf(const wchar_t * restrict format,
21988 va_list arg);
21989 </pre>
21990 <p><b>Description</b>
21991 <p><!--para 2 -->
21992 The vwprintf function is equivalent to wprintf, with the variable argument list
21993 replaced by arg, which shall have been initialized by the va_start macro (and
21994 possibly subsequent va_arg calls). The vwprintf function does not invoke the
21996 <p><b>Returns</b>
21997 <p><!--para 3 -->
21998 The vwprintf function returns the number of wide characters transmitted, or a negative
21999 value if an output or encoding error occurred.
22003 <p><b>Synopsis</b>
22004 <p><!--para 1 -->
22005 <pre>
22008 int vwscanf(const wchar_t * restrict format,
22009 va_list arg);
22010 </pre>
22011 <p><b>Description</b>
22012 <p><!--para 2 -->
22013 The vwscanf function is equivalent to wscanf, with the variable argument list
22014 replaced by arg, which shall have been initialized by the va_start macro (and
22015 possibly subsequent va_arg calls). The vwscanf function does not invoke the
22017 <p><b>Returns</b>
22018 <p><!--para 3 -->
22019 The vwscanf function returns the value of the macro EOF if an input failure occurs
22020 before the first conversion (if any) has completed. Otherwise, the vwscanf function
22021 returns the number of input items assigned, which can be fewer than provided for, or even
22022 zero, in the event of an early matching failure.
22023 <!--page 439 -->
22027 <p><b>Synopsis</b>
22028 <p><!--para 1 -->
22029 <pre>
22031 int wprintf(const wchar_t * restrict format, ...);
22032 </pre>
22033 <p><b>Description</b>
22034 <p><!--para 2 -->
22035 The wprintf function is equivalent to fwprintf with the argument stdout
22036 interposed before the arguments to wprintf.
22037 <p><b>Returns</b>
22038 <p><!--para 3 -->
22039 The wprintf function returns the number of wide characters transmitted, or a negative
22040 value if an output or encoding error occurred.
22044 <p><b>Synopsis</b>
22045 <p><!--para 1 -->
22046 <pre>
22048 int wscanf(const wchar_t * restrict format, ...);
22049 </pre>
22050 <p><b>Description</b>
22051 <p><!--para 2 -->
22052 The wscanf function is equivalent to fwscanf with the argument stdin interposed
22053 before the arguments to wscanf.
22054 <p><b>Returns</b>
22055 <p><!--para 3 -->
22056 The wscanf function returns the value of the macro EOF if an input failure occurs
22057 before the first conversion (if any) has completed. Otherwise, the wscanf function
22058 returns the number of input items assigned, which can be fewer than provided for, or even
22059 zero, in the event of an early matching failure.
22066 <p><b>Synopsis</b>
22067 <p><!--para 1 -->
22068 <pre>
22071 wint_t fgetwc(FILE *stream);
22072 </pre>
22073 <p><b>Description</b>
22074 <p><!--para 2 -->
22075 If the end-of-file indicator for the input stream pointed to by stream is not set and a
22076 next wide character is present, the fgetwc function obtains that wide character as a
22077 wchar_t converted to a wint_t and advances the associated file position indicator for
22078 the stream (if defined).
22079 <!--page 440 -->
22080 <p><b>Returns</b>
22081 <p><!--para 3 -->
22082 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
22083 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
22084 the fgetwc function returns the next wide character from the input stream pointed to by
22085 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
22086 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
22087 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note341"><b>341)</b></a></sup>
22089 <p><b>Footnotes</b>
22090 <p><small><a name="note341" href="#note341">341)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
22091 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
22092 </small>
22096 <p><b>Synopsis</b>
22097 <p><!--para 1 -->
22098 <pre>
22101 wchar_t *fgetws(wchar_t * restrict s,
22102 int n, FILE * restrict stream);
22103 </pre>
22104 <p><b>Description</b>
22105 <p><!--para 2 -->
22106 The fgetws function reads at most one less than the number of wide characters
22107 specified by n from the stream pointed to by stream into the array pointed to by s. No
22108 additional wide characters are read after a new-line wide character (which is retained) or
22109 after end-of-file. A null wide character is written immediately after the last wide
22110 character read into the array.
22111 <p><b>Returns</b>
22112 <p><!--para 3 -->
22113 The fgetws function returns s if successful. If end-of-file is encountered and no
22114 characters have been read into the array, the contents of the array remain unchanged and a
22115 null pointer is returned. If a read or encoding error occurs during the operation, the array
22116 contents are indeterminate and a null pointer is returned.
22120 <p><b>Synopsis</b>
22121 <p><!--para 1 -->
22122 <pre>
22125 wint_t fputwc(wchar_t c, FILE *stream);
22126 </pre>
22127 <p><b>Description</b>
22128 <p><!--para 2 -->
22129 The fputwc function writes the wide character specified by c to the output stream
22130 pointed to by stream, at the position indicated by the associated file position indicator
22131 for the stream (if defined), and advances the indicator appropriately. If the file cannot
22133 <!--page 441 -->
22134 support positioning requests, or if the stream was opened with append mode, the
22135 character is appended to the output stream.
22136 <p><b>Returns</b>
22137 <p><!--para 3 -->
22138 The fputwc function returns the wide character written. If a write error occurs, the
22139 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
22140 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
22144 <p><b>Synopsis</b>
22145 <p><!--para 1 -->
22146 <pre>
22149 int fputws(const wchar_t * restrict s,
22150 FILE * restrict stream);
22151 </pre>
22152 <p><b>Description</b>
22153 <p><!--para 2 -->
22154 The fputws function writes the wide string pointed to by s to the stream pointed to by
22155 stream. The terminating null wide character is not written.
22156 <p><b>Returns</b>
22157 <p><!--para 3 -->
22158 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
22159 returns a nonnegative value.
22163 <p><b>Synopsis</b>
22164 <p><!--para 1 -->
22165 <pre>
22168 int fwide(FILE *stream, int mode);
22169 </pre>
22170 <p><b>Description</b>
22171 <p><!--para 2 -->
22172 The fwide function determines the orientation of the stream pointed to by stream. If
22173 mode is greater than zero, the function first attempts to make the stream wide oriented. If
22174 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note342"><b>342)</b></a></sup>
22175 Otherwise, mode is zero and the function does not alter the orientation of the stream.
22176 <p><b>Returns</b>
22177 <p><!--para 3 -->
22178 The fwide function returns a value greater than zero if, after the call, the stream has
22179 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
22180 stream has no orientation.
22183 <!--page 442 -->
22185 <p><b>Footnotes</b>
22186 <p><small><a name="note342" href="#note342">342)</a> If the orientation of the stream has already been determined, fwide does not change it.
22187 </small>
22191 <p><b>Synopsis</b>
22192 <p><!--para 1 -->
22193 <pre>
22196 wint_t getwc(FILE *stream);
22197 </pre>
22198 <p><b>Description</b>
22199 <p><!--para 2 -->
22200 The getwc function is equivalent to fgetwc, except that if it is implemented as a
22201 macro, it may evaluate stream more than once, so the argument should never be an
22202 expression with side effects.
22203 <p><b>Returns</b>
22204 <p><!--para 3 -->
22205 The getwc function returns the next wide character from the input stream pointed to by
22206 stream, or WEOF.
22210 <p><b>Synopsis</b>
22211 <p><!--para 1 -->
22212 <pre>
22214 wint_t getwchar(void);
22215 </pre>
22216 <p><b>Description</b>
22217 <p><!--para 2 -->
22218 The getwchar function is equivalent to getwc with the argument stdin.
22219 <p><b>Returns</b>
22220 <p><!--para 3 -->
22221 The getwchar function returns the next wide character from the input stream pointed to
22222 by stdin, or WEOF.
22226 <p><b>Synopsis</b>
22227 <p><!--para 1 -->
22228 <pre>
22231 wint_t putwc(wchar_t c, FILE *stream);
22232 </pre>
22233 <p><b>Description</b>
22234 <p><!--para 2 -->
22235 The putwc function is equivalent to fputwc, except that if it is implemented as a
22236 macro, it may evaluate stream more than once, so that argument should never be an
22237 expression with side effects.
22238 <p><b>Returns</b>
22239 <p><!--para 3 -->
22240 The putwc function returns the wide character written, or WEOF.
22241 <!--page 443 -->
22245 <p><b>Synopsis</b>
22246 <p><!--para 1 -->
22247 <pre>
22249 wint_t putwchar(wchar_t c);
22250 </pre>
22251 <p><b>Description</b>
22252 <p><!--para 2 -->
22253 The putwchar function is equivalent to putwc with the second argument stdout.
22254 <p><b>Returns</b>
22255 <p><!--para 3 -->
22256 The putwchar function returns the character written, or WEOF.
22260 <p><b>Synopsis</b>
22261 <p><!--para 1 -->
22262 <pre>
22265 wint_t ungetwc(wint_t c, FILE *stream);
22266 </pre>
22267 <p><b>Description</b>
22268 <p><!--para 2 -->
22269 The ungetwc function pushes the wide character specified by c back onto the input
22270 stream pointed to by stream. Pushed-back wide characters will be returned by
22271 subsequent reads on that stream in the reverse order of their pushing. A successful
22272 intervening call (with the stream pointed to by stream) to a file positioning function
22273 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
22274 stream. The external storage corresponding to the stream is unchanged.
22275 <p><!--para 3 -->
22276 One wide character of pushback is guaranteed, even if the call to the ungetwc function
22277 follows just after a call to a formatted wide character input function fwscanf,
22278 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
22279 on the same stream without an intervening read or file positioning operation on that
22280 stream, the operation may fail.
22281 <p><!--para 4 -->
22282 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
22283 unchanged.
22284 <p><!--para 5 -->
22285 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
22286 The value of the file position indicator for the stream after reading or discarding all
22287 pushed-back wide characters is the same as it was before the wide characters were pushed
22288 back. For a text or binary stream, the value of its file position indicator after a successful
22289 call to the ungetwc function is unspecified until all pushed-back wide characters are
22290 read or discarded.
22291 <!--page 444 -->
22292 <p><b>Returns</b>
22293 <p><!--para 6 -->
22294 The ungetwc function returns the wide character pushed back, or WEOF if the operation
22295 fails.
22299 <p><!--para 1 -->
22300 The header <a href="#7.29"><wchar.h></a> declares a number of functions useful for wide string
22301 manipulation. Various methods are used for determining the lengths of the arrays, but in
22302 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
22303 array. If an array is accessed beyond the end of an object, the behavior is undefined.
22304 <p><!--para 2 -->
22305 Where an argument declared as size_t n determines the length of the array for a
22306 function, n can have the value zero on a call to that function. Unless explicitly stated
22307 otherwise in the description of a particular function in this subclause, pointer arguments
22308 on such a call shall still have valid values, as described in <a href="#7.1.4">7.1.4</a>. On such a call, a
22309 function that locates a wide character finds no occurrence, a function that compares two
22310 wide character sequences returns zero, and a function that copies wide characters copies
22311 zero wide characters.
22314 <h5><a name="7.29.4.1" href="#7.29.4.1">7.29.4.1 Wide string numeric conversion functions</a></h5>
22317 <h5><a name="7.29.4.1.1" href="#7.29.4.1.1">7.29.4.1.1 The wcstod, wcstof, and wcstold functions</a></h5>
22318 <p><b>Synopsis</b>
22319 <p><!--para 1 -->
22320 <pre>
22322 double wcstod(const wchar_t * restrict nptr,
22323 wchar_t ** restrict endptr);
22324 float wcstof(const wchar_t * restrict nptr,
22325 wchar_t ** restrict endptr);
22326 long double wcstold(const wchar_t * restrict nptr,
22327 wchar_t ** restrict endptr);
22328 </pre>
22329 <p><b>Description</b>
22330 <p><!--para 2 -->
22331 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
22332 string pointed to by nptr to double, float, and long double representation,
22333 respectively. First, they decompose the input string into three parts: an initial, possibly
22334 empty, sequence of white-space wide characters (as specified by the iswspace
22335 function), a subject sequence resembling a floating-point constant or representing an
22336 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
22337 including the terminating null wide character of the input wide string. Then, they attempt
22338 to convert the subject sequence to a floating-point number, and return the result.
22339 <p><!--para 3 -->
22340 The expected form of the subject sequence is an optional plus or minus sign, then one of
22341 the following:
22342 <!--page 445 -->
22343 <ul>
22344 <li> a nonempty sequence of decimal digits optionally containing a decimal-point wide
22345 character, then an optional exponent part as defined for the corresponding single-byte
22347 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
22348 decimal-point wide character, then an optional binary exponent part as defined in
22350 <li> INF or INFINITY, or any other wide string equivalent except for case
22351 <li> NAN or NAN(n-wchar-sequence<sub>opt</sub>), or any other wide string equivalent except for
22352 case in the NAN part, where:
22353 <pre>
22354 n-wchar-sequence:
22355 digit
22356 nondigit
22357 n-wchar-sequence digit
22358 n-wchar-sequence nondigit
22359 </pre>
22360 </ul>
22361 The subject sequence is defined as the longest initial subsequence of the input wide
22362 string, starting with the first non-white-space wide character, that is of the expected form.
22363 The subject sequence contains no wide characters if the input wide string is not of the
22364 expected form.
22365 <p><!--para 4 -->
22366 If the subject sequence has the expected form for a floating-point number, the sequence of
22367 wide characters starting with the first digit or the decimal-point wide character
22368 (whichever occurs first) is interpreted as a floating constant according to the rules of
22369 <a href="#6.4.4.2">6.4.4.2</a>, except that the decimal-point wide character is used in place of a period, and that
22370 if neither an exponent part nor a decimal-point wide character appears in a decimal
22371 floating point number, or if a binary exponent part does not appear in a hexadecimal
22372 floating point number, an exponent part of the appropriate type with value zero is
22373 assumed to follow the last digit in the string. If the subject sequence begins with a minus
22374 sign, the sequence is interpreted as negated.<sup><a href="#note343"><b>343)</b></a></sup> A wide character sequence INF or
22375 INFINITY is interpreted as an infinity, if representable in the return type, else like a
22376 floating constant that is too large for the range of the return type. A wide character
22377 sequence NAN or NAN(n-wchar-sequence<sub>opt</sub>) is interpreted as a quiet NaN, if supported
22378 in the return type, else like a subject sequence part that does not have the expected form;
22379 the meaning of the n-wchar sequence is implementation-defined.<sup><a href="#note344"><b>344)</b></a></sup> A pointer to the
22381 <!--page 446 -->
22382 final wide string is stored in the object pointed to by endptr, provided that endptr is
22383 not a null pointer.
22384 <p><!--para 5 -->
22385 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
22386 value resulting from the conversion is correctly rounded.
22387 <p><!--para 6 -->
22389 accepted.
22390 <p><!--para 7 -->
22391 If the subject sequence is empty or does not have the expected form, no conversion is
22392 performed; the value of nptr is stored in the object pointed to by endptr, provided
22393 that endptr is not a null pointer.
22394 <p><b>Recommended practice</b>
22395 <p><!--para 8 -->
22396 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
22397 the result is not exactly representable, the result should be one of the two numbers in the
22398 appropriate internal format that are adjacent to the hexadecimal floating source value,
22399 with the extra stipulation that the error should have a correct sign for the current rounding
22400 direction.
22401 <p><!--para 9 -->
22402 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
22403 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
22404 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
22405 consider the two bounding, adjacent decimal strings L and U, both having
22406 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
22407 The result should be one of the (equal or adjacent) values that would be obtained by
22408 correctly rounding L and U according to the current rounding direction, with the extra
22409 stipulation that the error with respect to D should have a correct sign for the current
22411 <p><b>Returns</b>
22412 <p><!--para 10 -->
22413 The functions return the converted value, if any. If no conversion could be performed,
22414 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
22415 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
22416 return type and sign of the value), and the value of the macro ERANGE is stored in
22417 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
22418 no greater than the smallest normalized positive number in the return type; whether
22419 errno acquires the value ERANGE is implementation-defined.
22424 <!--page 447 -->
22426 <p><b>Footnotes</b>
22427 <p><small><a name="note343" href="#note343">343)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
22428 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
22429 methods may yield different results if rounding is toward positive or negative infinity. In either case,
22430 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
22431 </small>
22432 <p><small><a name="note344" href="#note344">344)</a> An implementation may use the n-wchar sequence to determine extra information to be represented in
22433 the NaN's significand.
22434 </small>
22435 <p><small><a name="note345" href="#note345">345)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
22436 to the same internal floating value, but if not will round to adjacent values.
22437 </small>
22440 <h5><a name="7.29.4.1.2" href="#7.29.4.1.2">7.29.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions</a></h5>
22441 <p><b>Synopsis</b>
22442 <p><!--para 1 -->
22443 <pre>
22445 long int wcstol(
22446 const wchar_t * restrict nptr,
22447 wchar_t ** restrict endptr,
22448 int base);
22449 long long int wcstoll(
22450 const wchar_t * restrict nptr,
22451 wchar_t ** restrict endptr,
22452 int base);
22453 unsigned long int wcstoul(
22454 const wchar_t * restrict nptr,
22455 wchar_t ** restrict endptr,
22456 int base);
22457 unsigned long long int wcstoull(
22458 const wchar_t * restrict nptr,
22459 wchar_t ** restrict endptr,
22460 int base);
22461 </pre>
22462 <p><b>Description</b>
22463 <p><!--para 2 -->
22464 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
22465 portion of the wide string pointed to by nptr to long int, long long int,
22466 unsigned long int, and unsigned long long int representation,
22467 respectively. First, they decompose the input string into three parts: an initial, possibly
22468 empty, sequence of white-space wide characters (as specified by the iswspace
22469 function), a subject sequence resembling an integer represented in some radix determined
22470 by the value of base, and a final wide string of one or more unrecognized wide
22471 characters, including the terminating null wide character of the input wide string. Then,
22472 they attempt to convert the subject sequence to an integer, and return the result.
22473 <p><!--para 3 -->
22474 If the value of base is zero, the expected form of the subject sequence is that of an
22475 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
22476 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
22477 value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
22478 is a sequence of letters and digits representing an integer with the radix specified by
22479 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
22480 The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
22481 letters and digits whose ascribed values are less than that of base are permitted. If the
22482 value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
22483 of letters and digits, following the sign if present.
22484 <!--page 448 -->
22485 <p><!--para 4 -->
22486 The subject sequence is defined as the longest initial subsequence of the input wide
22487 string, starting with the first non-white-space wide character, that is of the expected form.
22488 The subject sequence contains no wide characters if the input wide string is empty or
22489 consists entirely of white space, or if the first non-white-space wide character is other
22490 than a sign or a permissible letter or digit.
22491 <p><!--para 5 -->
22492 If the subject sequence has the expected form and the value of base is zero, the sequence
22493 of wide characters starting with the first digit is interpreted as an integer constant
22494 according to the rules of <a href="#6.4.4.1">6.4.4.1</a>. If the subject sequence has the expected form and the
22495 value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
22496 letter its value as given above. If the subject sequence begins with a minus sign, the value
22497 resulting from the conversion is negated (in the return type). A pointer to the final wide
22498 string is stored in the object pointed to by endptr, provided that endptr is not a null
22499 pointer.
22500 <p><!--para 6 -->
22502 accepted.
22503 <p><!--para 7 -->
22504 If the subject sequence is empty or does not have the expected form, no conversion is
22505 performed; the value of nptr is stored in the object pointed to by endptr, provided
22506 that endptr is not a null pointer.
22507 <p><b>Returns</b>
22508 <p><!--para 8 -->
22509 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
22510 value, if any. If no conversion could be performed, zero is returned. If the correct value
22511 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
22512 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
22513 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
22520 <p><b>Synopsis</b>
22521 <p><!--para 1 -->
22522 <pre>
22524 wchar_t *wcscpy(wchar_t * restrict s1,
22525 const wchar_t * restrict s2);
22526 </pre>
22527 <p><b>Description</b>
22528 <p><!--para 2 -->
22529 The wcscpy function copies the wide string pointed to by s2 (including the terminating
22530 null wide character) into the array pointed to by s1.
22531 <p><b>Returns</b>
22532 <p><!--para 3 -->
22533 The wcscpy function returns the value of s1.
22534 <!--page 449 -->
22538 <p><b>Synopsis</b>
22539 <p><!--para 1 -->
22540 <pre>
22542 wchar_t *wcsncpy(wchar_t * restrict s1,
22543 const wchar_t * restrict s2,
22544 size_t n);
22545 </pre>
22546 <p><b>Description</b>
22547 <p><!--para 2 -->
22548 The wcsncpy function copies not more than n wide characters (those that follow a null
22549 wide character are not copied) from the array pointed to by s2 to the array pointed to by
22551 <p><!--para 3 -->
22552 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
22553 wide characters are appended to the copy in the array pointed to by s1, until n wide
22554 characters in all have been written.
22555 <p><b>Returns</b>
22556 <p><!--para 4 -->
22557 The wcsncpy function returns the value of s1.
22559 <p><b>Footnotes</b>
22560 <p><small><a name="note346" href="#note346">346)</a> Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
22561 result will not be null-terminated.
22562 </small>
22566 <p><b>Synopsis</b>
22567 <p><!--para 1 -->
22568 <pre>
22570 wchar_t *wmemcpy(wchar_t * restrict s1,
22571 const wchar_t * restrict s2,
22572 size_t n);
22573 </pre>
22574 <p><b>Description</b>
22575 <p><!--para 2 -->
22576 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
22577 object pointed to by s1.
22578 <p><b>Returns</b>
22579 <p><!--para 3 -->
22580 The wmemcpy function returns the value of s1.
22585 <!--page 450 -->
22589 <p><b>Synopsis</b>
22590 <p><!--para 1 -->
22591 <pre>
22593 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
22594 size_t n);
22595 </pre>
22596 <p><b>Description</b>
22597 <p><!--para 2 -->
22598 The wmemmove function copies n wide characters from the object pointed to by s2 to
22599 the object pointed to by s1. Copying takes place as if the n wide characters from the
22600 object pointed to by s2 are first copied into a temporary array of n wide characters that
22601 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
22602 the temporary array are copied into the object pointed to by s1.
22603 <p><b>Returns</b>
22604 <p><!--para 3 -->
22605 The wmemmove function returns the value of s1.
22612 <p><b>Synopsis</b>
22613 <p><!--para 1 -->
22614 <pre>
22616 wchar_t *wcscat(wchar_t * restrict s1,
22617 const wchar_t * restrict s2);
22618 </pre>
22619 <p><b>Description</b>
22620 <p><!--para 2 -->
22621 The wcscat function appends a copy of the wide string pointed to by s2 (including the
22622 terminating null wide character) to the end of the wide string pointed to by s1. The initial
22623 wide character of s2 overwrites the null wide character at the end of s1.
22624 <p><b>Returns</b>
22625 <p><!--para 3 -->
22626 The wcscat function returns the value of s1.
22630 <p><b>Synopsis</b>
22631 <p><!--para 1 -->
22632 <pre>
22634 wchar_t *wcsncat(wchar_t * restrict s1,
22635 const wchar_t * restrict s2,
22636 size_t n);
22637 </pre>
22638 <p><b>Description</b>
22639 <p><!--para 2 -->
22640 The wcsncat function appends not more than n wide characters (a null wide character
22641 and those that follow it are not appended) from the array pointed to by s2 to the end of
22642 <!--page 451 -->
22643 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
22644 wide character at the end of s1. A terminating null wide character is always appended to
22646 <p><b>Returns</b>
22647 <p><!--para 3 -->
22648 The wcsncat function returns the value of s1.
22650 <p><b>Footnotes</b>
22651 <p><small><a name="note347" href="#note347">347)</a> Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
22652 wcslen(s1)+n+1.
22653 </small>
22657 <p><!--para 1 -->
22658 Unless explicitly stated otherwise, the functions described in this subclause order two
22659 wide characters the same way as two integers of the underlying integer type designated
22660 by wchar_t.
22664 <p><b>Synopsis</b>
22665 <p><!--para 1 -->
22666 <pre>
22668 int wcscmp(const wchar_t *s1, const wchar_t *s2);
22669 </pre>
22670 <p><b>Description</b>
22671 <p><!--para 2 -->
22672 The wcscmp function compares the wide string pointed to by s1 to the wide string
22673 pointed to by s2.
22674 <p><b>Returns</b>
22675 <p><!--para 3 -->
22676 The wcscmp function returns an integer greater than, equal to, or less than zero,
22677 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
22678 wide string pointed to by s2.
22682 <p><b>Synopsis</b>
22683 <p><!--para 1 -->
22684 <pre>
22686 int wcscoll(const wchar_t *s1, const wchar_t *s2);
22687 </pre>
22688 <p><b>Description</b>
22689 <p><!--para 2 -->
22690 The wcscoll function compares the wide string pointed to by s1 to the wide string
22691 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
22692 current locale.
22693 <p><b>Returns</b>
22694 <p><!--para 3 -->
22695 The wcscoll function returns an integer greater than, equal to, or less than zero,
22696 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
22699 <!--page 452 -->
22700 wide string pointed to by s2 when both are interpreted as appropriate to the current
22701 locale.
22705 <p><b>Synopsis</b>
22706 <p><!--para 1 -->
22707 <pre>
22709 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
22710 size_t n);
22711 </pre>
22712 <p><b>Description</b>
22713 <p><!--para 2 -->
22714 The wcsncmp function compares not more than n wide characters (those that follow a
22715 null wide character are not compared) from the array pointed to by s1 to the array
22716 pointed to by s2.
22717 <p><b>Returns</b>
22718 <p><!--para 3 -->
22719 The wcsncmp function returns an integer greater than, equal to, or less than zero,
22720 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
22721 to, or less than the possibly null-terminated array pointed to by s2.
22725 <p><b>Synopsis</b>
22726 <p><!--para 1 -->
22727 <pre>
22729 size_t wcsxfrm(wchar_t * restrict s1,
22730 const wchar_t * restrict s2,
22731 size_t n);
22732 </pre>
22733 <p><b>Description</b>
22734 <p><!--para 2 -->
22735 The wcsxfrm function transforms the wide string pointed to by s2 and places the
22736 resulting wide string into the array pointed to by s1. The transformation is such that if
22737 the wcscmp function is applied to two transformed wide strings, it returns a value greater
22738 than, equal to, or less than zero, corresponding to the result of the wcscoll function
22739 applied to the same two original wide strings. No more than n wide characters are placed
22740 into the resulting array pointed to by s1, including the terminating null wide character. If
22741 n is zero, s1 is permitted to be a null pointer.
22742 <p><b>Returns</b>
22743 <p><!--para 3 -->
22744 The wcsxfrm function returns the length of the transformed wide string (not including
22745 the terminating null wide character). If the value returned is n or greater, the contents of
22746 the array pointed to by s1 are indeterminate.
22747 <p><!--para 4 -->
22748 EXAMPLE The value of the following expression is the length of the array needed to hold the
22749 transformation of the wide string pointed to by s:
22750 <!--page 453 -->
22751 <pre>
22752 1 + wcsxfrm(NULL, s, 0)
22753 </pre>
22758 <p><b>Synopsis</b>
22759 <p><!--para 1 -->
22760 <pre>
22762 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
22763 size_t n);
22764 </pre>
22765 <p><b>Description</b>
22766 <p><!--para 2 -->
22767 The wmemcmp function compares the first n wide characters of the object pointed to by
22768 s1 to the first n wide characters of the object pointed to by s2.
22769 <p><b>Returns</b>
22770 <p><!--para 3 -->
22771 The wmemcmp function returns an integer greater than, equal to, or less than zero,
22772 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
22773 pointed to by s2.
22780 <p><b>Synopsis</b>
22781 <p><!--para 1 -->
22782 <pre>
22784 wchar_t *wcschr(const wchar_t *s, wchar_t c);
22785 </pre>
22786 <p><b>Description</b>
22787 <p><!--para 2 -->
22788 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
22789 The terminating null wide character is considered to be part of the wide string.
22790 <p><b>Returns</b>
22791 <p><!--para 3 -->
22792 The wcschr function returns a pointer to the located wide character, or a null pointer if
22793 the wide character does not occur in the wide string.
22797 <p><b>Synopsis</b>
22798 <p><!--para 1 -->
22799 <pre>
22801 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
22802 </pre>
22803 <p><b>Description</b>
22804 <p><!--para 2 -->
22805 The wcscspn function computes the length of the maximum initial segment of the wide
22806 string pointed to by s1 which consists entirely of wide characters not from the wide
22807 string pointed to by s2.
22808 <!--page 454 -->
22809 <p><b>Returns</b>
22810 <p><!--para 3 -->
22811 The wcscspn function returns the length of the segment.
22815 <p><b>Synopsis</b>
22816 <p><!--para 1 -->
22817 <pre>
22819 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
22820 </pre>
22821 <p><b>Description</b>
22822 <p><!--para 2 -->
22823 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
22824 any wide character from the wide string pointed to by s2.
22825 <p><b>Returns</b>
22826 <p><!--para 3 -->
22827 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
22828 no wide character from s2 occurs in s1.
22832 <p><b>Synopsis</b>
22833 <p><!--para 1 -->
22834 <pre>
22836 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
22837 </pre>
22838 <p><b>Description</b>
22839 <p><!--para 2 -->
22840 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
22841 s. The terminating null wide character is considered to be part of the wide string.
22842 <p><b>Returns</b>
22843 <p><!--para 3 -->
22844 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
22845 not occur in the wide string.
22849 <p><b>Synopsis</b>
22850 <p><!--para 1 -->
22851 <pre>
22853 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
22854 </pre>
22855 <p><b>Description</b>
22856 <p><!--para 2 -->
22857 The wcsspn function computes the length of the maximum initial segment of the wide
22858 string pointed to by s1 which consists entirely of wide characters from the wide string
22859 pointed to by s2.
22860 <p><b>Returns</b>
22861 <p><!--para 3 -->
22862 The wcsspn function returns the length of the segment.
22863 <!--page 455 -->
22867 <p><b>Synopsis</b>
22868 <p><!--para 1 -->
22869 <pre>
22871 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
22872 </pre>
22873 <p><b>Description</b>
22874 <p><!--para 2 -->
22875 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
22876 the sequence of wide characters (excluding the terminating null wide character) in the
22877 wide string pointed to by s2.
22878 <p><b>Returns</b>
22879 <p><!--para 3 -->
22880 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
22881 wide string is not found. If s2 points to a wide string with zero length, the function
22882 returns s1.
22886 <p><b>Synopsis</b>
22887 <p><!--para 1 -->
22888 <pre>
22890 wchar_t *wcstok(wchar_t * restrict s1,
22891 const wchar_t * restrict s2,
22892 wchar_t ** restrict ptr);
22893 </pre>
22894 <p><b>Description</b>
22895 <p><!--para 2 -->
22896 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
22897 a sequence of tokens, each of which is delimited by a wide character from the wide string
22898 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
22899 which the wcstok function stores information necessary for it to continue scanning the
22900 same wide string.
22901 <p><!--para 3 -->
22902 The first call in a sequence has a non-null first argument and stores an initial value in the
22903 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
22904 the object pointed to by ptr is required to have the value stored by the previous call in
22905 the sequence, which is then updated. The separator wide string pointed to by s2 may be
22906 different from call to call.
22907 <p><!--para 4 -->
22908 The first call in the sequence searches the wide string pointed to by s1 for the first wide
22909 character that is not contained in the current separator wide string pointed to by s2. If no
22910 such wide character is found, then there are no tokens in the wide string pointed to by s1
22911 and the wcstok function returns a null pointer. If such a wide character is found, it is
22912 the start of the first token.
22913 <p><!--para 5 -->
22914 The wcstok function then searches from there for a wide character that is contained in
22915 the current separator wide string. If no such wide character is found, the current token
22916 <!--page 456 -->
22917 extends to the end of the wide string pointed to by s1, and subsequent searches in the
22918 same wide string for a token return a null pointer. If such a wide character is found, it is
22919 overwritten by a null wide character, which terminates the current token.
22920 <p><!--para 6 -->
22921 In all cases, the wcstok function stores sufficient information in the pointer pointed to
22922 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
22923 value for ptr, shall start searching just past the element overwritten by a null wide
22924 character (if any).
22925 <p><b>Returns</b>
22926 <p><!--para 7 -->
22927 The wcstok function returns a pointer to the first wide character of a token, or a null
22928 pointer if there is no token.
22929 <p><!--para 8 -->
22930 EXAMPLE
22931 <pre>
22935 wchar_t *t, *ptr1, *ptr2;
22941 </pre>
22946 <p><b>Synopsis</b>
22947 <p><!--para 1 -->
22948 <pre>
22950 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
22951 size_t n);
22952 </pre>
22953 <p><b>Description</b>
22954 <p><!--para 2 -->
22955 The wmemchr function locates the first occurrence of c in the initial n wide characters of
22956 the object pointed to by s.
22957 <p><b>Returns</b>
22958 <p><!--para 3 -->
22959 The wmemchr function returns a pointer to the located wide character, or a null pointer if
22960 the wide character does not occur in the object.
22961 <!--page 457 -->
22968 <p><b>Synopsis</b>
22969 <p><!--para 1 -->
22970 <pre>
22972 size_t wcslen(const wchar_t *s);
22973 </pre>
22974 <p><b>Description</b>
22975 <p><!--para 2 -->
22976 The wcslen function computes the length of the wide string pointed to by s.
22977 <p><b>Returns</b>
22978 <p><!--para 3 -->
22979 The wcslen function returns the number of wide characters that precede the terminating
22980 null wide character.
22984 <p><b>Synopsis</b>
22985 <p><!--para 1 -->
22986 <pre>
22988 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
22989 </pre>
22990 <p><b>Description</b>
22991 <p><!--para 2 -->
22992 The wmemset function copies the value of c into each of the first n wide characters of
22993 the object pointed to by s.
22994 <p><b>Returns</b>
22995 <p><!--para 3 -->
22996 The wmemset function returns the value of s.
23003 <p><b>Synopsis</b>
23004 <p><!--para 1 -->
23005 <pre>
23008 size_t wcsftime(wchar_t * restrict s,
23009 size_t maxsize,
23010 const wchar_t * restrict format,
23011 const struct tm * restrict timeptr);
23012 </pre>
23013 <p><b>Description</b>
23014 <p><!--para 2 -->
23015 The wcsftime function is equivalent to the strftime function, except that:
23016 <ul>
23017 <li> The argument s points to the initial element of an array of wide characters into which
23018 the generated output is to be placed.
23019 <!--page 458 -->
23020 <li> The argument maxsize indicates the limiting number of wide characters.
23021 <li> The argument format is a wide string and the conversion specifiers are replaced by
23022 corresponding sequences of wide characters.
23023 <li> The return value indicates the number of wide characters.
23024 </ul>
23025 <p><b>Returns</b>
23026 <p><!--para 3 -->
23027 If the total number of resulting wide characters including the terminating null wide
23028 character is not more than maxsize, the wcsftime function returns the number of
23029 wide characters placed into the array pointed to by s not including the terminating null
23030 wide character. Otherwise, zero is returned and the contents of the array are
23031 indeterminate.
23034 <h4><a name="7.29.6" href="#7.29.6">7.29.6 Extended multibyte/wide character conversion utilities</a></h4>
23035 <p><!--para 1 -->
23036 The header <a href="#7.29"><wchar.h></a> declares an extended set of functions useful for conversion
23037 between multibyte characters and wide characters.
23038 <p><!--para 2 -->
23039 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.29.6.3">7.29.6.3</a> and
23040 <a href="#7.29.6.4">7.29.6.4</a> -- take as a last argument a pointer to an object of type mbstate_t that is used
23041 to describe the current conversion state from a particular multibyte character sequence to
23042 a wide character sequence (or the reverse) under the rules of a particular setting for the
23043 LC_CTYPE category of the current locale.
23044 <p><!--para 3 -->
23045 The initial conversion state corresponds, for a conversion in either direction, to the
23046 beginning of a new multibyte character in the initial shift state. A zero-valued
23047 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
23048 valued mbstate_t object can be used to initiate conversion involving any multibyte
23049 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
23050 been altered by any of the functions described in this subclause, and is then used with a
23051 different multibyte character sequence, or in the other conversion direction, or with a
23052 different LC_CTYPE category setting than on earlier function calls, the behavior is
23054 <p><!--para 4 -->
23055 On entry, each function takes the described conversion state (either internal or pointed to
23056 by an argument) as current. The conversion state described by the referenced object is
23057 altered as needed to track the shift state, and the position within a multibyte character, for
23058 the associated multibyte character sequence.
23063 <!--page 459 -->
23065 <p><b>Footnotes</b>
23066 <p><small><a name="note348" href="#note348">348)</a> Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
23067 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
23068 character string.
23069 </small>
23072 <h5><a name="7.29.6.1" href="#7.29.6.1">7.29.6.1 Single-byte/wide character conversion functions</a></h5>
23076 <p><b>Synopsis</b>
23077 <p><!--para 1 -->
23078 <pre>
23080 wint_t btowc(int c);
23081 </pre>
23082 <p><b>Description</b>
23083 <p><!--para 2 -->
23084 The btowc function determines whether c constitutes a valid single-byte character in the
23085 initial shift state.
23086 <p><b>Returns</b>
23087 <p><!--para 3 -->
23088 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
23089 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
23090 returns the wide character representation of that character.
23094 <p><b>Synopsis</b>
23095 <p><!--para 1 -->
23096 <pre>
23098 int wctob(wint_t c);
23099 </pre>
23100 <p><b>Description</b>
23101 <p><!--para 2 -->
23102 The wctob function determines whether c corresponds to a member of the extended
23103 character set whose multibyte character representation is a single byte when in the initial
23104 shift state.
23105 <p><b>Returns</b>
23106 <p><!--para 3 -->
23107 The wctob function returns EOF if c does not correspond to a multibyte character with
23108 length one in the initial shift state. Otherwise, it returns the single-byte representation of
23109 that character as an unsigned char converted to an int.
23116 <p><b>Synopsis</b>
23117 <p><!--para 1 -->
23118 <pre>
23120 int mbsinit(const mbstate_t *ps);
23121 </pre>
23122 <p><b>Description</b>
23123 <p><!--para 2 -->
23124 If ps is not a null pointer, the mbsinit function determines whether the referenced
23125 mbstate_t object describes an initial conversion state.
23126 <!--page 460 -->
23127 <p><b>Returns</b>
23128 <p><!--para 3 -->
23129 The mbsinit function returns nonzero if ps is a null pointer or if the referenced object
23130 describes an initial conversion state; otherwise, it returns zero.
23133 <h5><a name="7.29.6.3" href="#7.29.6.3">7.29.6.3 Restartable multibyte/wide character conversion functions</a></h5>
23134 <p><!--para 1 -->
23135 These functions differ from the corresponding multibyte character functions of <a href="#7.22.7">7.22.7</a>
23136 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
23137 pointer to mbstate_t that points to an object that can completely describe the current
23138 conversion state of the associated multibyte character sequence. If ps is a null pointer,
23139 each function uses its own internal mbstate_t object instead, which is initialized at
23140 program startup to the initial conversion state; the functions are not required to avoid data
23141 races with other calls to the same function in this case. The implementation behaves as if
23142 no library function calls these functions with a null pointer for ps.
23143 <p><!--para 2 -->
23144 Also unlike their corresponding functions, the return value does not represent whether the
23145 encoding is state-dependent.
23149 <p><b>Synopsis</b>
23150 <p><!--para 1 -->
23151 <pre>
23153 size_t mbrlen(const char * restrict s,
23154 size_t n,
23155 mbstate_t * restrict ps);
23156 </pre>
23157 <p><b>Description</b>
23158 <p><!--para 2 -->
23159 The mbrlen function is equivalent to the call:
23160 <pre>
23161 mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)
23162 </pre>
23163 where internal is the mbstate_t object for the mbrlen function, except that the
23164 expression designated by ps is evaluated only once.
23165 <p><b>Returns</b>
23166 <p><!--para 3 -->
23167 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
23168 or (size_t)(-1).
23170 <!--page 461 -->
23174 <p><b>Synopsis</b>
23175 <p><!--para 1 -->
23176 <pre>
23178 size_t mbrtowc(wchar_t * restrict pwc,
23179 const char * restrict s,
23180 size_t n,
23181 mbstate_t * restrict ps);
23182 </pre>
23183 <p><b>Description</b>
23184 <p><!--para 2 -->
23185 If s is a null pointer, the mbrtowc function is equivalent to the call:
23186 <pre>
23188 </pre>
23189 In this case, the values of the parameters pwc and n are ignored.
23190 <p><!--para 3 -->
23191 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
23192 the byte pointed to by s to determine the number of bytes needed to complete the next
23193 multibyte character (including any shift sequences). If the function determines that the
23194 next multibyte character is complete and valid, it determines the value of the
23195 corresponding wide character and then, if pwc is not a null pointer, stores that value in
23196 the object pointed to by pwc. If the corresponding wide character is the null wide
23197 character, the resulting state described is the initial conversion state.
23198 <p><b>Returns</b>
23199 <p><!--para 4 -->
23200 The mbrtowc function returns the first of the following that applies (given the current
23201 conversion state):
23202 0 if the next n or fewer bytes complete the multibyte character that
23203 <pre>
23204 corresponds to the null wide character (which is the value stored).
23205 </pre>
23206 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
23207 <pre>
23208 character (which is the value stored); the value returned is the number
23209 of bytes that complete the multibyte character.
23210 </pre>
23211 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
23212 <pre>
23213 multibyte character, and all n bytes have been processed (no value is
23215 </pre>
23216 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
23217 <pre>
23218 do not contribute to a complete and valid multibyte character (no
23219 value is stored); the value of the macro EILSEQ is stored in errno,
23220 and the conversion state is unspecified.
23221 </pre>
23223 <!--page 462 -->
23225 <p><b>Footnotes</b>
23226 <p><small><a name="note349" href="#note349">349)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
23227 sequence of redundant shift sequences (for implementations with state-dependent encodings).
23228 </small>
23232 <p><b>Synopsis</b>
23233 <p><!--para 1 -->
23234 <pre>
23236 size_t wcrtomb(char * restrict s,
23237 wchar_t wc,
23238 mbstate_t * restrict ps);
23239 </pre>
23240 <p><b>Description</b>
23241 <p><!--para 2 -->
23242 If s is a null pointer, the wcrtomb function is equivalent to the call
23243 <pre>
23244 wcrtomb(buf, L'\0', ps)
23245 </pre>
23246 where buf is an internal buffer.
23247 <p><!--para 3 -->
23248 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
23249 to represent the multibyte character that corresponds to the wide character given by wc
23250 (including any shift sequences), and stores the multibyte character representation in the
23251 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
23252 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
23253 to restore the initial shift state; the resulting state described is the initial conversion state.
23254 <p><b>Returns</b>
23255 <p><!--para 4 -->
23256 The wcrtomb function returns the number of bytes stored in the array object (including
23257 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
23258 the function stores the value of the macro EILSEQ in errno and returns
23259 (size_t)(-1); the conversion state is unspecified.
23262 <h5><a name="7.29.6.4" href="#7.29.6.4">7.29.6.4 Restartable multibyte/wide string conversion functions</a></h5>
23263 <p><!--para 1 -->
23264 These functions differ from the corresponding multibyte string functions of <a href="#7.22.8">7.22.8</a>
23265 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
23266 mbstate_t that points to an object that can completely describe the current conversion
23267 state of the associated multibyte character sequence. If ps is a null pointer, each function
23268 uses its own internal mbstate_t object instead, which is initialized at program startup
23269 to the initial conversion state; the functions are not required to avoid data races with other
23270 calls to the same function in this case. The implementation behaves as if no library
23271 function calls these functions with a null pointer for ps.
23272 <p><!--para 2 -->
23273 Also unlike their corresponding functions, the conversion source parameter, src, has a
23274 pointer-to-pointer type. When the function is storing the results of conversions (that is,
23275 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
23276 to reflect the amount of the source processed by that invocation.
23277 <!--page 463 -->
23281 <p><b>Synopsis</b>
23282 <p><!--para 1 -->
23283 <pre>
23285 size_t mbsrtowcs(wchar_t * restrict dst,
23286 const char ** restrict src,
23287 size_t len,
23288 mbstate_t * restrict ps);
23289 </pre>
23290 <p><b>Description</b>
23291 <p><!--para 2 -->
23292 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
23293 conversion state described by the object pointed to by ps, from the array indirectly
23294 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
23295 pointer, the converted characters are stored into the array pointed to by dst. Conversion
23296 continues up to and including a terminating null character, which is also stored.
23297 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
23298 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
23299 characters have been stored into the array pointed to by dst.<sup><a href="#note350"><b>350)</b></a></sup> Each conversion takes
23300 place as if by a call to the mbrtowc function.
23301 <p><!--para 3 -->
23302 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
23303 pointer (if conversion stopped due to reaching a terminating null character) or the address
23304 just past the last multibyte character converted (if any). If conversion stopped due to
23305 reaching a terminating null character and if dst is not a null pointer, the resulting state
23306 described is the initial conversion state.
23307 <p><b>Returns</b>
23308 <p><!--para 4 -->
23309 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
23310 character, an encoding error occurs: the mbsrtowcs function stores the value of the
23311 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
23312 unspecified. Otherwise, it returns the number of multibyte characters successfully
23313 converted, not including the terminating null character (if any).
23318 <!--page 464 -->
23320 <p><b>Footnotes</b>
23321 <p><small><a name="note350" href="#note350">350)</a> Thus, the value of len is ignored if dst is a null pointer.
23322 </small>
23326 <p><b>Synopsis</b>
23327 <p><!--para 1 -->
23328 <pre>
23330 size_t wcsrtombs(char * restrict dst,
23331 const wchar_t ** restrict src,
23332 size_t len,
23333 mbstate_t * restrict ps);
23334 </pre>
23335 <p><b>Description</b>
23336 <p><!--para 2 -->
23337 The wcsrtombs function converts a sequence of wide characters from the array
23338 indirectly pointed to by src into a sequence of corresponding multibyte characters that
23339 begins in the conversion state described by the object pointed to by ps. If dst is not a
23340 null pointer, the converted characters are then stored into the array pointed to by dst.
23341 Conversion continues up to and including a terminating null wide character, which is also
23342 stored. Conversion stops earlier in two cases: when a wide character is reached that does
23343 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
23344 next multibyte character would exceed the limit of len total bytes to be stored into the
23345 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
23347 <p><!--para 3 -->
23348 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
23349 pointer (if conversion stopped due to reaching a terminating null wide character) or the
23350 address just past the last wide character converted (if any). If conversion stopped due to
23351 reaching a terminating null wide character, the resulting state described is the initial
23352 conversion state.
23353 <p><b>Returns</b>
23354 <p><!--para 4 -->
23355 If conversion stops because a wide character is reached that does not correspond to a
23356 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
23357 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
23358 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
23359 character sequence, not including the terminating null character (if any).
23364 <!--page 465 -->
23366 <p><b>Footnotes</b>
23367 <p><small><a name="note351" href="#note351">351)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
23368 include those necessary to reach the initial shift state immediately before the null byte.
23369 </small>
23372 <h3><a name="7.30" href="#7.30">7.30 Wide character classification and mapping utilities <wctype.h></a></h3>
23376 <p><!--para 1 -->
23377 The header <a href="#7.30"><wctype.h></a> defines one macro, and declares three data types and many
23379 <p><!--para 2 -->
23380 The types declared are
23381 <pre>
23382 wint_t
23383 </pre>
23385 <pre>
23386 wctrans_t
23387 </pre>
23388 which is a scalar type that can hold values which represent locale-specific character
23389 mappings; and
23390 <pre>
23391 wctype_t
23392 </pre>
23393 which is a scalar type that can hold values which represent locale-specific character
23394 classifications.
23395 <p><!--para 3 -->
23397 <p><!--para 4 -->
23398 The functions declared are grouped as follows:
23399 <ul>
23400 <li> Functions that provide wide character classification;
23401 <li> Extensible functions that provide wide character classification;
23402 <li> Functions that provide wide character case mapping;
23403 <li> Extensible functions that provide wide character mapping.
23404 </ul>
23405 <p><!--para 5 -->
23406 For all functions described in this subclause that accept an argument of type wint_t, the
23407 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
23408 this argument has any other value, the behavior is undefined.
23409 <p><!--para 6 -->
23410 The behavior of these functions is affected by the LC_CTYPE category of the current
23411 locale.
23416 <!--page 466 -->
23418 <p><b>Footnotes</b>
23419 <p><small><a name="note352" href="#note352">352)</a> See ''future library directions'' (<a href="#7.31.17">7.31.17</a>).
23420 </small>
23424 <p><!--para 1 -->
23425 The header <a href="#7.30"><wctype.h></a> declares several functions useful for classifying wide
23426 characters.
23427 <p><!--para 2 -->
23428 The term printing wide character refers to a member of a locale-specific set of wide
23429 characters, each of which occupies at least one printing position on a display device. The
23430 term control wide character refers to a member of a locale-specific set of wide characters
23431 that are not printing wide characters.
23434 <h5><a name="7.30.2.1" href="#7.30.2.1">7.30.2.1 Wide character classification functions</a></h5>
23435 <p><!--para 1 -->
23436 The functions in this subclause return nonzero (true) if and only if the value of the
23437 argument wc conforms to that in the description of the function.
23438 <p><!--para 2 -->
23439 Each of the following functions returns true for each wide character that corresponds (as
23440 if by a call to the wctob function) to a single-byte character for which the corresponding
23441 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
23442 iswpunct functions may differ with respect to wide characters other than L' ' that are
23446 <p><b>Footnotes</b>
23447 <p><small><a name="note353" href="#note353">353)</a> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
23448 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
23449 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
23450 && iswspace(wc) is true, but not both.
23451 </small>
23455 <p><b>Synopsis</b>
23456 <p><!--para 1 -->
23457 <pre>
23459 int iswalnum(wint_t wc);
23460 </pre>
23461 <p><b>Description</b>
23462 <p><!--para 2 -->
23463 The iswalnum function tests for any wide character for which iswalpha or
23464 iswdigit is true.
23468 <p><b>Synopsis</b>
23469 <p><!--para 1 -->
23470 <pre>
23472 int iswalpha(wint_t wc);
23473 </pre>
23474 <p><b>Description</b>
23475 <p><!--para 2 -->
23476 The iswalpha function tests for any wide character for which iswupper or
23477 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
23479 <!--page 467 -->
23480 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
23483 <p><b>Footnotes</b>
23484 <p><small><a name="note354" href="#note354">354)</a> The functions iswlower and iswupper test true or false separately for each of these additional
23485 wide characters; all four combinations are possible.
23486 </small>
23490 <p><b>Synopsis</b>
23491 <p><!--para 1 -->
23492 <pre>
23494 int iswblank(wint_t wc);
23495 </pre>
23496 <p><b>Description</b>
23497 <p><!--para 2 -->
23498 The iswblank function tests for any wide character that is a standard blank wide
23499 character or is one of a locale-specific set of wide characters for which iswspace is true
23500 and that is used to separate words within a line of text. The standard blank wide
23502 locale, iswblank returns true only for the standard blank characters.
23506 <p><b>Synopsis</b>
23507 <p><!--para 1 -->
23508 <pre>
23510 int iswcntrl(wint_t wc);
23511 </pre>
23512 <p><b>Description</b>
23513 <p><!--para 2 -->
23514 The iswcntrl function tests for any control wide character.
23518 <p><b>Synopsis</b>
23519 <p><!--para 1 -->
23520 <pre>
23522 int iswdigit(wint_t wc);
23523 </pre>
23524 <p><b>Description</b>
23525 <p><!--para 2 -->
23526 The iswdigit function tests for any wide character that corresponds to a decimal-digit
23531 <p><b>Synopsis</b>
23532 <p><!--para 1 -->
23533 <pre>
23535 int iswgraph(wint_t wc);
23536 </pre>
23541 <!--page 468 -->
23542 <p><b>Description</b>
23543 <p><!--para 2 -->
23544 The iswgraph function tests for any wide character for which iswprint is true and
23547 <p><b>Footnotes</b>
23548 <p><small><a name="note355" href="#note355">355)</a> Note that the behavior of the iswgraph and iswpunct functions may differ from their
23549 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
23550 characters other than ' '.
23551 </small>
23555 <p><b>Synopsis</b>
23556 <p><!--para 1 -->
23557 <pre>
23559 int iswlower(wint_t wc);
23560 </pre>
23561 <p><b>Description</b>
23562 <p><!--para 2 -->
23563 The iswlower function tests for any wide character that corresponds to a lowercase
23564 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
23565 iswdigit, iswpunct, or iswspace is true.
23569 <p><b>Synopsis</b>
23570 <p><!--para 1 -->
23571 <pre>
23573 int iswprint(wint_t wc);
23574 </pre>
23575 <p><b>Description</b>
23576 <p><!--para 2 -->
23577 The iswprint function tests for any printing wide character.
23581 <p><b>Synopsis</b>
23582 <p><!--para 1 -->
23583 <pre>
23585 int iswpunct(wint_t wc);
23586 </pre>
23587 <p><b>Description</b>
23588 <p><!--para 2 -->
23589 The iswpunct function tests for any printing wide character that is one of a locale-
23590 specific set of punctuation wide characters for which neither iswspace nor iswalnum
23595 <p><b>Synopsis</b>
23596 <p><!--para 1 -->
23597 <pre>
23599 int iswspace(wint_t wc);
23600 </pre>
23604 <!--page 469 -->
23605 <p><b>Description</b>
23606 <p><!--para 2 -->
23607 The iswspace function tests for any wide character that corresponds to a locale-specific
23608 set of white-space wide characters for which none of iswalnum, iswgraph, or
23609 iswpunct is true.
23613 <p><b>Synopsis</b>
23614 <p><!--para 1 -->
23615 <pre>
23617 int iswupper(wint_t wc);
23618 </pre>
23619 <p><b>Description</b>
23620 <p><!--para 2 -->
23621 The iswupper function tests for any wide character that corresponds to an uppercase
23622 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
23623 iswdigit, iswpunct, or iswspace is true.
23627 <p><b>Synopsis</b>
23628 <p><!--para 1 -->
23629 <pre>
23631 int iswxdigit(wint_t wc);
23632 </pre>
23633 <p><b>Description</b>
23634 <p><!--para 2 -->
23635 The iswxdigit function tests for any wide character that corresponds to a
23639 <h5><a name="7.30.2.2" href="#7.30.2.2">7.30.2.2 Extensible wide character classification functions</a></h5>
23640 <p><!--para 1 -->
23641 The functions wctype and iswctype provide extensible wide character classification
23642 as well as testing equivalent to that performed by the functions described in the previous
23647 <p><b>Synopsis</b>
23648 <p><!--para 1 -->
23649 <pre>
23651 int iswctype(wint_t wc, wctype_t desc);
23652 </pre>
23653 <p><b>Description</b>
23654 <p><!--para 2 -->
23655 The iswctype function determines whether the wide character wc has the property
23656 described by desc. The current setting of the LC_CTYPE category shall be the same as
23657 during the call to wctype that returned the value desc.
23658 <p><!--para 3 -->
23659 Each of the following expressions has a truth-value equivalent to the call to the wide
23660 character classification function (<a href="#7.30.2.1">7.30.2.1</a>) in the comment that follows the expression:
23661 <!--page 470 -->
23662 <pre>
23675 </pre>
23676 <p><b>Returns</b>
23677 <p><!--para 4 -->
23678 The iswctype function returns nonzero (true) if and only if the value of the wide
23679 character wc has the property described by desc. If desc is zero, the iswctype
23680 function returns zero (false).
23685 <p><b>Synopsis</b>
23686 <p><!--para 1 -->
23687 <pre>
23689 wctype_t wctype(const char *property);
23690 </pre>
23691 <p><b>Description</b>
23692 <p><!--para 2 -->
23693 The wctype function constructs a value with type wctype_t that describes a class of
23694 wide characters identified by the string argument property.
23695 <p><!--para 3 -->
23696 The strings listed in the description of the iswctype function shall be valid in all
23697 locales as property arguments to the wctype function.
23698 <p><b>Returns</b>
23699 <p><!--para 4 -->
23700 If property identifies a valid class of wide characters according to the LC_CTYPE
23701 category of the current locale, the wctype function returns a nonzero value that is valid
23702 as the second argument to the iswctype function; otherwise, it returns zero.
23703 <!--page 471 -->
23707 <p><!--para 1 -->
23708 The header <a href="#7.30"><wctype.h></a> declares several functions useful for mapping wide characters.
23711 <h5><a name="7.30.3.1" href="#7.30.3.1">7.30.3.1 Wide character case mapping functions</a></h5>
23715 <p><b>Synopsis</b>
23716 <p><!--para 1 -->
23717 <pre>
23719 wint_t towlower(wint_t wc);
23720 </pre>
23721 <p><b>Description</b>
23722 <p><!--para 2 -->
23723 The towlower function converts an uppercase letter to a corresponding lowercase letter.
23724 <p><b>Returns</b>
23725 <p><!--para 3 -->
23726 If the argument is a wide character for which iswupper is true and there are one or
23727 more corresponding wide characters, as specified by the current locale, for which
23728 iswlower is true, the towlower function returns one of the corresponding wide
23729 characters (always the same one for any given locale); otherwise, the argument is
23730 returned unchanged.
23734 <p><b>Synopsis</b>
23735 <p><!--para 1 -->
23736 <pre>
23738 wint_t towupper(wint_t wc);
23739 </pre>
23740 <p><b>Description</b>
23741 <p><!--para 2 -->
23742 The towupper function converts a lowercase letter to a corresponding uppercase letter.
23743 <p><b>Returns</b>
23744 <p><!--para 3 -->
23745 If the argument is a wide character for which iswlower is true and there are one or
23746 more corresponding wide characters, as specified by the current locale, for which
23747 iswupper is true, the towupper function returns one of the corresponding wide
23748 characters (always the same one for any given locale); otherwise, the argument is
23749 returned unchanged.
23752 <h5><a name="7.30.3.2" href="#7.30.3.2">7.30.3.2 Extensible wide character case mapping functions</a></h5>
23753 <p><!--para 1 -->
23754 The functions wctrans and towctrans provide extensible wide character mapping as
23755 well as case mapping equivalent to that performed by the functions described in the
23757 <!--page 472 -->
23761 <p><b>Synopsis</b>
23762 <p><!--para 1 -->
23763 <pre>
23765 wint_t towctrans(wint_t wc, wctrans_t desc);
23766 </pre>
23767 <p><b>Description</b>
23768 <p><!--para 2 -->
23769 The towctrans function maps the wide character wc using the mapping described by
23770 desc. The current setting of the LC_CTYPE category shall be the same as during the call
23771 to wctrans that returned the value desc.
23772 <p><!--para 3 -->
23773 Each of the following expressions behaves the same as the call to the wide character case
23774 mapping function (<a href="#7.30.3.1">7.30.3.1</a>) in the comment that follows the expression:
23775 <pre>
23778 </pre>
23779 <p><b>Returns</b>
23780 <p><!--para 4 -->
23781 The towctrans function returns the mapped value of wc using the mapping described
23782 by desc. If desc is zero, the towctrans function returns the value of wc.
23786 <p><b>Synopsis</b>
23787 <p><!--para 1 -->
23788 <pre>
23790 wctrans_t wctrans(const char *property);
23791 </pre>
23792 <p><b>Description</b>
23793 <p><!--para 2 -->
23794 The wctrans function constructs a value with type wctrans_t that describes a
23795 mapping between wide characters identified by the string argument property.
23796 <p><!--para 3 -->
23797 The strings listed in the description of the towctrans function shall be valid in all
23798 locales as property arguments to the wctrans function.
23799 <p><b>Returns</b>
23800 <p><!--para 4 -->
23801 If property identifies a valid mapping of wide characters according to the LC_CTYPE
23802 category of the current locale, the wctrans function returns a nonzero value that is valid
23803 as the second argument to the towctrans function; otherwise, it returns zero.
23804 <!--page 473 -->
23808 <p><!--para 1 -->
23809 The following names are grouped under individual headers for convenience. All external
23810 names described below are reserved no matter what headers are included by the program.
23814 <p><!--para 1 -->
23815 The function names
23816 <pre>
23817 cerf cexpm1 clog2
23818 cerfc clog10 clgamma
23819 cexp2 clog1p ctgamma
23820 </pre>
23821 and the same names suffixed with f or l may be added to the declarations in the
23826 <p><!--para 1 -->
23827 Function names that begin with either is or to, and a lowercase letter may be added to
23832 <p><!--para 1 -->
23833 Macros that begin with E and a digit or E and an uppercase letter may be added to the
23838 <p><!--para 1 -->
23839 Macros that begin with FE_ and an uppercase letter may be added to the macros defined
23843 <h4><a name="7.31.5" href="#7.31.5">7.31.5 Format conversion of integer types <inttypes.h></a></h4>
23844 <p><!--para 1 -->
23845 Macros that begin with either PRI or SCN, and either a lowercase letter or X may be
23850 <p><!--para 1 -->
23851 Macros that begin with LC_ and an uppercase letter may be added to the macros defined
23856 <p><!--para 1 -->
23857 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
23862 <p><!--para 1 -->
23863 Macros that begin with ATOMIC_ and an uppercase letter may be added to the macros
23864 defined in the <a href="#7.17"><stdatomic.h></a> header. Typedef names that begin with either
23865 atomic_ or memory_, and a lowercase letter may be added to the declarations in the
23866 <a href="#7.17"><stdatomic.h></a> header. Enumeration constants that begin with memory_order_
23867 <!--page 474 -->
23868 and a lowercase letter may be added to the definition of the memory_order type in the
23869 <a href="#7.17"><stdatomic.h></a> header. Function names that begin with atomic_ and a lowercase
23870 letter may be added to the declarations in the <a href="#7.17"><stdatomic.h></a> header.
23874 <p><!--para 1 -->
23875 The ability to undefine and perhaps then redefine the macros bool, true, and false is
23876 an obsolescent feature.
23880 <p><!--para 1 -->
23881 Typedef names beginning with int or uint and ending with _t may be added to the
23882 types defined in the <a href="#7.20"><stdint.h></a> header. Macro names beginning with INT or UINT
23883 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
23888 <p><!--para 1 -->
23889 Lowercase letters may be added to the conversion specifiers and length modifiers in
23890 fprintf and fscanf. Other characters may be used in extensions.
23891 <p><!--para 2 -->
23892 The use of ungetc on a binary stream where the file position indicator is zero prior to
23893 the call is an obsolescent feature.
23897 <p><!--para 1 -->
23898 Function names that begin with str and a lowercase letter may be added to the
23903 <p><!--para 1 -->
23904 Function names that begin with str, mem, or wcs and a lowercase letter may be added
23909 Macros beginning with TIME_ and an uppercase letter may be added to the macros in the
23914 <p><!--para 1 -->
23915 Function names, type names, and enumeration constants that begin with either cnd_,
23916 mtx_, thrd_, or tss_, and a lowercase letter may be added to the declarations in the
23920 <h4><a name="7.31.16" href="#7.31.16">7.31.16 Extended multibyte and wide character utilities <wchar.h></a></h4>
23921 <p><!--para 1 -->
23922 Function names that begin with wcs and a lowercase letter may be added to the
23924 <p><!--para 2 -->
23925 Lowercase letters may be added to the conversion specifiers and length modifiers in
23926 fwprintf and fwscanf. Other characters may be used in extensions.
23927 <!--page 475 -->
23930 <h4><a name="7.31.17" href="#7.31.17">7.31.17 Wide character classification and mapping utilities</a></h4>
23932 <p><!--para 1 -->
23933 Function names that begin with is or to and a lowercase letter may be added to the
23935 <!--page 476 -->
23939 <pre>
23940 (informative)
23941 Language syntax summary
23942 </pre>
23943 <p><!--para 1 -->
23953 <pre>
23954 keyword
23955 identifier
23956 constant
23957 string-literal
23958 punctuator
23959 </pre>
23961 <!--page 477 -->
23962 <pre>
23963 header-name
23964 identifier
23965 pp-number
23966 character-constant
23967 string-literal
23968 punctuator
23969 each non-white-space character that cannot be one of the above
23970 </pre>
23975 <pre>
23976 auto * if unsigned
23977 break inline void
23978 case int volatile
23979 char long while
23980 const register _Alignas
23981 continue restrict _Alignof
23982 default return _Atomic
23983 do short _Bool
23984 double signed _Complex
23985 else sizeof _Generic
23986 enum static _Imaginary
23987 extern struct _Noreturn
23988 float switch _Static_assert
23989 for typedef _Thread_local
23990 goto union
23991 </pre>
23996 <pre>
23997 identifier-nondigit
23998 identifier identifier-nondigit
23999 identifier digit
24000 </pre>
24002 <pre>
24003 nondigit
24004 universal-character-name
24005 other implementation-defined characters
24006 </pre>
24008 <pre>
24009 _ a b c d e f g h i j k l m
24010 n o p q r s t u v w x y z
24011 A B C D E F G H I J K L M
24012 N O P Q R S T U V W X Y Z
24013 </pre>
24015 <!--page 478 -->
24016 <pre>
24017 0 1 2 3 4 5 6 7 8 9
24018 </pre>
24023 <pre>
24024 \u hex-quad
24025 \U hex-quad hex-quad
24026 </pre>
24028 <pre>
24029 hexadecimal-digit hexadecimal-digit
24030 hexadecimal-digit hexadecimal-digit
24031 </pre>
24036 <pre>
24037 integer-constant
24038 floating-constant
24039 enumeration-constant
24040 character-constant
24041 </pre>
24043 <pre>
24044 decimal-constant integer-suffix<sub>opt</sub>
24045 octal-constant integer-suffix<sub>opt</sub>
24046 hexadecimal-constant integer-suffix<sub>opt</sub>
24047 </pre>
24049 <pre>
24050 nonzero-digit
24051 decimal-constant digit
24052 </pre>
24054 <pre>
24055 0
24056 octal-constant octal-digit
24057 </pre>
24059 <pre>
24060 hexadecimal-prefix hexadecimal-digit
24061 hexadecimal-constant hexadecimal-digit
24062 </pre>
24064 <pre>
24065 0x 0X
24066 </pre>
24068 <pre>
24069 1 2 3 4 5 6 7 8 9
24070 </pre>
24072 <!--page 479 -->
24073 <pre>
24074 0 1 2 3 4 5 6 7
24075 </pre>
24077 <pre>
24078 0 1 2 3 4 5 6 7 8 9
24079 a b c d e f
24080 A B C D E F
24081 </pre>
24083 <pre>
24084 unsigned-suffix long-suffix<sub>opt</sub>
24085 unsigned-suffix long-long-suffix
24086 long-suffix unsigned-suffix<sub>opt</sub>
24087 long-long-suffix unsigned-suffix<sub>opt</sub>
24088 </pre>
24090 <pre>
24091 u U
24092 </pre>
24094 <pre>
24095 l L
24096 </pre>
24098 <pre>
24099 ll LL
24100 </pre>
24102 <pre>
24103 decimal-floating-constant
24104 hexadecimal-floating-constant
24105 </pre>
24107 <pre>
24108 fractional-constant exponent-part<sub>opt</sub> floating-suffix<sub>opt</sub>
24109 digit-sequence exponent-part floating-suffix<sub>opt</sub>
24110 </pre>
24112 <pre>
24113 hexadecimal-prefix hexadecimal-fractional-constant
24114 binary-exponent-part floating-suffix<sub>opt</sub>
24115 hexadecimal-prefix hexadecimal-digit-sequence
24116 binary-exponent-part floating-suffix<sub>opt</sub>
24117 </pre>
24119 <pre>
24120 digit-sequence<sub>opt</sub> . digit-sequence
24121 digit-sequence .
24122 </pre>
24124 <pre>
24125 e sign<sub>opt</sub> digit-sequence
24126 E sign<sub>opt</sub> digit-sequence
24127 </pre>
24129 <!--page 480 -->
24130 <pre>
24131 + -
24132 </pre>
24134 <pre>
24135 digit
24136 digit-sequence digit
24137 </pre>
24139 <pre>
24140 hexadecimal-digit-sequence<sub>opt</sub> .
24141 hexadecimal-digit-sequence
24142 hexadecimal-digit-sequence .
24143 </pre>
24145 <pre>
24146 p sign<sub>opt</sub> digit-sequence
24147 P sign<sub>opt</sub> digit-sequence
24148 </pre>
24150 <pre>
24151 hexadecimal-digit
24152 hexadecimal-digit-sequence hexadecimal-digit
24153 </pre>
24155 <pre>
24156 f l F L
24157 </pre>
24159 <pre>
24160 identifier
24161 </pre>
24163 <pre>
24164 ' c-char-sequence '
24165 L' c-char-sequence '
24166 u' c-char-sequence '
24167 U' c-char-sequence '
24168 </pre>
24170 <pre>
24171 c-char
24172 c-char-sequence c-char
24173 </pre>
24175 <pre>
24176 any member of the source character set except
24177 the single-quote ', backslash \, or new-line character
24178 escape-sequence
24179 </pre>
24181 <!--page 481 -->
24182 <pre>
24183 simple-escape-sequence
24184 octal-escape-sequence
24185 hexadecimal-escape-sequence
24186 universal-character-name
24187 </pre>
24189 <pre>
24190 \' \" \? \\
24191 \a \b \f \n \r \t \v
24192 </pre>
24194 <pre>
24195 \ octal-digit
24196 \ octal-digit octal-digit
24197 \ octal-digit octal-digit octal-digit
24198 </pre>
24200 <pre>
24201 \x hexadecimal-digit
24202 hexadecimal-escape-sequence hexadecimal-digit
24203 </pre>
24208 <pre>
24210 </pre>
24212 <pre>
24213 u8
24214 u
24215 U
24216 L
24217 </pre>
24219 <pre>
24220 s-char
24221 s-char-sequence s-char
24222 </pre>
24224 <pre>
24225 any member of the source character set except
24226 the double-quote ", backslash \, or new-line character
24227 escape-sequence
24228 </pre>
24233 <!--page 482 -->
24234 <pre>
24235 [ ] ( ) { } . ->
24236 ++ -- & * + - ~ !
24237 / % << >> < > <= >= == != ^ | && ||
24238 ? : ; ...
24239 = *= /= %= += -= <<= >>= &= ^= |=
24240 , # ##
24241 <: :> <% %> %: %:%:
24242 </pre>
24247 <pre>
24248 < h-char-sequence >
24250 </pre>
24252 <pre>
24253 h-char
24254 h-char-sequence h-char
24255 </pre>
24257 <pre>
24258 any member of the source character set except
24259 the new-line character and >
24260 </pre>
24262 <pre>
24263 q-char
24264 q-char-sequence q-char
24265 </pre>
24267 <pre>
24268 any member of the source character set except
24269 the new-line character and "
24270 </pre>
24275 <!--page 483 -->
24276 <pre>
24277 digit
24278 . digit
24279 pp-number digit
24280 pp-number identifier-nondigit
24281 pp-number e sign
24282 pp-number E sign
24283 pp-number p sign
24284 pp-number P sign
24285 pp-number .
24286 </pre>
24294 <pre>
24295 identifier
24296 constant
24297 string-literal
24298 ( expression )
24299 generic-selection
24300 </pre>
24302 <pre>
24303 _Generic ( assignment-expression , generic-assoc-list )
24304 </pre>
24306 <pre>
24307 generic-association
24308 generic-assoc-list , generic-association
24309 </pre>
24311 <pre>
24312 type-name : assignment-expression
24313 default : assignment-expression
24314 </pre>
24316 <pre>
24317 primary-expression
24318 postfix-expression [ expression ]
24320 postfix-expression . identifier
24321 postfix-expression -> identifier
24322 postfix-expression ++
24323 postfix-expression --
24324 ( type-name ) { initializer-list }
24325 ( type-name ) { initializer-list , }
24326 </pre>
24328 <pre>
24329 assignment-expression
24330 argument-expression-list , assignment-expression
24331 </pre>
24333 <!--page 484 -->
24334 <pre>
24335 postfix-expression
24336 ++ unary-expression
24337 -- unary-expression
24338 unary-operator cast-expression
24339 sizeof unary-expression
24340 sizeof ( type-name )
24341 _Alignof ( type-name )
24342 </pre>
24344 <pre>
24345 & * + - ~ !
24346 </pre>
24348 <pre>
24349 unary-expression
24350 ( type-name ) cast-expression
24351 </pre>
24353 <pre>
24354 cast-expression
24355 multiplicative-expression * cast-expression
24356 multiplicative-expression / cast-expression
24357 multiplicative-expression % cast-expression
24358 </pre>
24360 <pre>
24361 multiplicative-expression
24362 additive-expression + multiplicative-expression
24363 additive-expression - multiplicative-expression
24364 </pre>
24366 <pre>
24367 additive-expression
24368 shift-expression << additive-expression
24369 shift-expression >> additive-expression
24370 </pre>
24372 <pre>
24373 shift-expression
24374 relational-expression < shift-expression
24375 relational-expression > shift-expression
24376 relational-expression <= shift-expression
24377 relational-expression >= shift-expression
24378 </pre>
24380 <pre>
24381 relational-expression
24382 equality-expression == relational-expression
24383 equality-expression != relational-expression
24384 </pre>
24386 <pre>
24387 equality-expression
24388 AND-expression & equality-expression
24389 </pre>
24391 <!--page 485 -->
24392 <pre>
24393 AND-expression
24394 exclusive-OR-expression ^ AND-expression
24395 </pre>
24397 <pre>
24398 exclusive-OR-expression
24399 inclusive-OR-expression | exclusive-OR-expression
24400 </pre>
24402 <pre>
24403 inclusive-OR-expression
24404 logical-AND-expression && inclusive-OR-expression
24405 </pre>
24407 <pre>
24408 logical-AND-expression
24409 logical-OR-expression || logical-AND-expression
24410 </pre>
24412 <pre>
24413 logical-OR-expression
24414 logical-OR-expression ? expression : conditional-expression
24415 </pre>
24417 <pre>
24418 conditional-expression
24419 unary-expression assignment-operator assignment-expression
24420 </pre>
24422 <pre>
24424 </pre>
24426 <pre>
24427 assignment-expression
24428 expression , assignment-expression
24429 </pre>
24431 <pre>
24432 conditional-expression
24433 </pre>
24438 <pre>
24440 static_assert-declaration
24441 </pre>
24443 <pre>
24449 </pre>
24451 <!--page 486 -->
24452 <pre>
24453 init-declarator
24454 init-declarator-list , init-declarator
24455 </pre>
24457 <pre>
24458 declarator
24459 declarator = initializer
24460 </pre>
24462 <pre>
24463 typedef
24464 extern
24465 static
24466 _Thread_local
24467 auto
24468 register
24469 </pre>
24471 <pre>
24472 void
24473 char
24474 short
24475 int
24476 long
24477 float
24478 double
24479 signed
24480 unsigned
24481 _Bool
24482 _Complex
24483 atomic-type-specifier
24484 struct-or-union-specifier
24485 enum-specifier
24486 typedef-name
24487 </pre>
24489 <pre>
24491 struct-or-union identifier
24492 </pre>
24494 <pre>
24495 struct
24496 union
24497 </pre>
24499 <pre>
24500 struct-declaration
24501 struct-declaration-list struct-declaration
24502 </pre>
24504 <!--page 487 -->
24505 <pre>
24507 static_assert-declaration
24508 </pre>
24510 <pre>
24513 </pre>
24515 <pre>
24516 struct-declarator
24517 struct-declarator-list , struct-declarator
24518 </pre>
24520 <pre>
24521 declarator
24523 </pre>
24525 <pre>
24528 enum identifier
24529 </pre>
24531 <pre>
24532 enumerator
24533 enumerator-list , enumerator
24534 </pre>
24536 <pre>
24537 enumeration-constant
24538 enumeration-constant = constant-expression
24539 </pre>
24541 <pre>
24542 _Atomic ( type-name )
24543 </pre>
24545 <pre>
24546 const
24547 restrict
24548 volatile
24549 _Atomic
24550 </pre>
24552 <pre>
24553 inline
24554 _Noreturn
24555 </pre>
24557 <pre>
24558 _Alignas ( type-name )
24559 _Alignas ( constant-expression )
24560 </pre>
24562 <!--page 488 -->
24563 <pre>
24565 </pre>
24567 <pre>
24568 identifier
24569 ( declarator )
24572 direct-declarator [ type-qualifier-list static assignment-expression ]
24574 direct-declarator ( parameter-type-list )
24576 </pre>
24578 <pre>
24581 </pre>
24583 <pre>
24584 type-qualifier
24585 type-qualifier-list type-qualifier
24586 </pre>
24588 <pre>
24589 parameter-list
24590 parameter-list , ...
24591 </pre>
24593 <pre>
24594 parameter-declaration
24595 parameter-list , parameter-declaration
24596 </pre>
24598 <pre>
24599 declaration-specifiers declarator
24601 </pre>
24603 <pre>
24604 identifier
24605 identifier-list , identifier
24606 </pre>
24608 <pre>
24610 </pre>
24612 <!--page 489 -->
24613 <pre>
24614 pointer
24616 </pre>
24618 <pre>
24619 ( abstract-declarator )
24623 assignment-expression ]
24625 assignment-expression ]
24628 </pre>
24630 <pre>
24631 identifier
24632 </pre>
24634 <pre>
24635 assignment-expression
24636 { initializer-list }
24637 { initializer-list , }
24638 </pre>
24640 <pre>
24643 </pre>
24645 <pre>
24646 designator-list =
24647 </pre>
24649 <pre>
24650 designator
24651 designator-list designator
24652 </pre>
24654 <pre>
24655 [ constant-expression ]
24656 . identifier
24657 </pre>
24659 <!--page 490 -->
24660 <pre>
24661 _Static_assert ( constant-expression , string-literal ) ;
24662 </pre>
24667 <pre>
24668 labeled-statement
24669 compound-statement
24670 expression-statement
24671 selection-statement
24672 iteration-statement
24673 jump-statement
24674 </pre>
24676 <pre>
24677 identifier : statement
24678 case constant-expression : statement
24679 default : statement
24680 </pre>
24682 <pre>
24684 </pre>
24686 <pre>
24687 block-item
24688 block-item-list block-item
24689 </pre>
24691 <pre>
24692 declaration
24693 statement
24694 </pre>
24696 <pre>
24698 </pre>
24700 <pre>
24701 if ( expression ) statement
24702 if ( expression ) statement else statement
24703 switch ( expression ) statement
24704 </pre>
24706 <pre>
24707 while ( expression ) statement
24708 do statement while ( expression ) ;
24709 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
24711 </pre>
24713 <!--page 491 -->
24714 <pre>
24715 goto identifier ;
24716 continue ;
24717 break ;
24719 </pre>
24724 <pre>
24725 external-declaration
24726 translation-unit external-declaration
24727 </pre>
24729 <pre>
24730 function-definition
24731 declaration
24732 </pre>
24734 <pre>
24736 </pre>
24738 <pre>
24739 declaration
24740 declaration-list declaration
24741 </pre>
24746 <pre>
24748 </pre>
24750 <pre>
24751 group-part
24752 group group-part
24753 </pre>
24755 <pre>
24756 if-section
24757 control-line
24758 text-line
24759 # non-directive
24760 </pre>
24762 <pre>
24764 </pre>
24766 <pre>
24770 </pre>
24772 <pre>
24773 elif-group
24774 elif-groups elif-group
24775 </pre>
24777 <!--page 492 -->
24778 <pre>
24780 </pre>
24782 <pre>
24784 </pre>
24786 <pre>
24787 # endif new-line
24788 </pre>
24790 <pre>
24791 # include pp-tokens new-line
24792 # define identifier replacement-list new-line
24794 replacement-list new-line
24795 # define identifier lparen ... ) replacement-list new-line
24796 # define identifier lparen identifier-list , ... )
24797 replacement-list new-line
24798 # undef identifier new-line
24799 # line pp-tokens new-line
24802 # new-line
24803 </pre>
24805 <pre>
24807 </pre>
24809 <pre>
24810 pp-tokens new-line
24811 </pre>
24813 <pre>
24814 a ( character not immediately preceded by white-space
24815 </pre>
24817 <pre>
24819 </pre>
24821 <pre>
24822 preprocessing-token
24823 pp-tokens preprocessing-token
24824 </pre>
24826 <!--page 493 -->
24827 <pre>
24828 the new-line character
24829 </pre>
24833 <pre>
24834 (informative)
24835 Library summary
24836 </pre>
24840 <pre>
24841 NDEBUG
24842 static_assert
24843 void assert(scalar expression);
24844 </pre>
24848 <!--page 494 -->
24849 <!--page 495 -->
24850 <pre>
24851 __STDC_NO_COMPLEX__ imaginary
24852 complex _Imaginary_I
24853 _Complex_I I
24854 #pragma STDC CX_LIMITED_RANGE on-off-switch
24855 double complex cacos(double complex z);
24856 float complex cacosf(float complex z);
24857 long double complex cacosl(long double complex z);
24858 double complex casin(double complex z);
24859 float complex casinf(float complex z);
24860 long double complex casinl(long double complex z);
24861 double complex catan(double complex z);
24862 float complex catanf(float complex z);
24863 long double complex catanl(long double complex z);
24864 double complex ccos(double complex z);
24865 float complex ccosf(float complex z);
24866 long double complex ccosl(long double complex z);
24867 double complex csin(double complex z);
24868 float complex csinf(float complex z);
24869 long double complex csinl(long double complex z);
24870 double complex ctan(double complex z);
24871 float complex ctanf(float complex z);
24872 long double complex ctanl(long double complex z);
24873 double complex cacosh(double complex z);
24874 float complex cacoshf(float complex z);
24875 long double complex cacoshl(long double complex z);
24876 double complex casinh(double complex z);
24877 float complex casinhf(float complex z);
24878 long double complex casinhl(long double complex z);
24879 double complex catanh(double complex z);
24880 float complex catanhf(float complex z);
24881 long double complex catanhl(long double complex z);
24882 double complex ccosh(double complex z);
24883 float complex ccoshf(float complex z);
24884 long double complex ccoshl(long double complex z);
24885 double complex csinh(double complex z);
24886 float complex csinhf(float complex z);
24887 long double complex csinhl(long double complex z);
24888 double complex ctanh(double complex z);
24889 float complex ctanhf(float complex z);
24890 long double complex ctanhl(long double complex z);
24891 double complex cexp(double complex z);
24892 float complex cexpf(float complex z);
24893 long double complex cexpl(long double complex z);
24894 double complex clog(double complex z);
24895 float complex clogf(float complex z);
24896 long double complex clogl(long double complex z);
24897 double cabs(double complex z);
24898 float cabsf(float complex z);
24899 long double cabsl(long double complex z);
24900 double complex cpow(double complex x, double complex y);
24901 float complex cpowf(float complex x, float complex y);
24902 long double complex cpowl(long double complex x,
24903 long double complex y);
24904 double complex csqrt(double complex z);
24905 float complex csqrtf(float complex z);
24906 long double complex csqrtl(long double complex z);
24907 double carg(double complex z);
24908 float cargf(float complex z);
24909 long double cargl(long double complex z);
24910 double cimag(double complex z);
24911 float cimagf(float complex z);
24912 long double cimagl(long double complex z);
24913 double complex CMPLX(double x, double y);
24914 float complex CMPLXF(float x, float y);
24915 long double complex CMPLXL(long double x, long double y);
24916 double complex conj(double complex z);
24917 float complex conjf(float complex z);
24918 long double complex conjl(long double complex z);
24919 double complex cproj(double complex z);
24920 float complex cprojf(float complex z);
24921 long double complex cprojl(long double complex z);
24922 double creal(double complex z);
24923 float crealf(float complex z);
24924 long double creall(long double complex z);
24925 </pre>
24929 <pre>
24930 int isalnum(int c);
24931 int isalpha(int c);
24932 int isblank(int c);
24933 int iscntrl(int c);
24934 int isdigit(int c);
24935 int isgraph(int c);
24936 int islower(int c);
24937 int isprint(int c);
24938 int ispunct(int c);
24939 int isspace(int c);
24940 int isupper(int c);
24941 int isxdigit(int c);
24942 int tolower(int c);
24943 int toupper(int c);
24944 </pre>
24948 <pre>
24949 EDOM EILSEQ ERANGE errno
24950 __STDC_WANT_LIB_EXT1__
24951 errno_t
24952 </pre>
24956 <!--page 496 -->
24957 <pre>
24958 fenv_t FE_OVERFLOW FE_TOWARDZERO
24959 fexcept_t FE_UNDERFLOW FE_UPWARD
24960 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
24961 FE_INEXACT FE_DOWNWARD
24962 FE_INVALID FE_TONEAREST
24963 #pragma STDC FENV_ACCESS on-off-switch
24964 int feclearexcept(int excepts);
24965 int fegetexceptflag(fexcept_t *flagp, int excepts);
24966 int feraiseexcept(int excepts);
24967 int fesetexceptflag(const fexcept_t *flagp,
24968 int excepts);
24969 int fetestexcept(int excepts);
24970 int fegetround(void);
24971 int fesetround(int round);
24972 int fegetenv(fenv_t *envp);
24973 int feholdexcept(fenv_t *envp);
24974 int fesetenv(const fenv_t *envp);
24975 int feupdateenv(const fenv_t *envp);
24976 </pre>
24980 <pre>
24981 FLT_ROUNDS DBL_DIG FLT_MAX
24982 FLT_EVAL_METHOD LDBL_DIG DBL_MAX
24983 FLT_HAS_SUBNORM FLT_MIN_EXP LDBL_MAX
24984 DBL_HAS_SUBNORM DBL_MIN_EXP FLT_EPSILON
24985 LDBL_HAS_SUBNORM LDBL_MIN_EXP DBL_EPSILON
24986 FLT_RADIX FLT_MIN_10_EXP LDBL_EPSILON
24987 FLT_MANT_DIG DBL_MIN_10_EXP FLT_MIN
24988 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_MIN
24989 LDBL_MANT_DIG FLT_MAX_EXP LDBL_MIN
24990 FLT_DECIMAL_DIG DBL_MAX_EXP FLT_TRUE_MIN
24991 DBL_DECIMAL_DIG LDBL_MAX_EXP DBL_TRUE_MIN
24992 LDBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_TRUE_MIN
24993 DECIMAL_DIG DBL_MAX_10_EXP
24994 FLT_DIG LDBL_MAX_10_EXP
24995 </pre>
24998 <h3><a name="B.7" href="#B.7">B.7 Format conversion of integer types <inttypes.h></a></h3>
24999 <!--page 497 -->
25000 <pre>
25001 imaxdiv_t
25002 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
25003 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
25004 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
25005 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
25006 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
25007 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
25008 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
25009 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
25010 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
25011 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
25012 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
25013 intmax_t imaxabs(intmax_t j);
25014 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
25015 intmax_t strtoimax(const char * restrict nptr,
25016 char ** restrict endptr, int base);
25017 uintmax_t strtoumax(const char * restrict nptr,
25018 char ** restrict endptr, int base);
25019 intmax_t wcstoimax(const wchar_t * restrict nptr,
25020 wchar_t ** restrict endptr, int base);
25021 uintmax_t wcstoumax(const wchar_t * restrict nptr,
25022 wchar_t ** restrict endptr, int base);
25023 </pre>
25027 <pre>
25028 and bitor not_eq xor
25029 and_eq compl or xor_eq
25030 bitand not or_eq
25031 </pre>
25035 <pre>
25036 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
25037 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
25038 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
25039 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
25040 CHAR_MIN USHRT_MAX LONG_MAX
25041 </pre>
25045 <pre>
25046 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
25047 NULL LC_COLLATE LC_MONETARY LC_TIME
25048 char *setlocale(int category, const char *locale);
25049 struct lconv *localeconv(void);
25050 </pre>
25054 <!--page 498 -->
25055 <!--page 499 -->
25056 <!--page 500 -->
25057 <!--page 501 -->
25058 <!--page 502 -->
25059 <pre>
25060 float_t FP_INFINITE FP_FAST_FMAL
25061 double_t FP_NAN FP_ILOGB0
25062 HUGE_VAL FP_NORMAL FP_ILOGBNAN
25063 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
25064 HUGE_VALL FP_ZERO MATH_ERREXCEPT
25065 INFINITY FP_FAST_FMA math_errhandling
25066 NAN FP_FAST_FMAF
25067 #pragma STDC FP_CONTRACT on-off-switch
25068 int fpclassify(real-floating x);
25069 int isfinite(real-floating x);
25070 int isinf(real-floating x);
25071 int isnan(real-floating x);
25072 int isnormal(real-floating x);
25073 int signbit(real-floating x);
25074 double acos(double x);
25075 float acosf(float x);
25076 long double acosl(long double x);
25077 double asin(double x);
25078 float asinf(float x);
25079 long double asinl(long double x);
25080 double atan(double x);
25081 float atanf(float x);
25082 long double atanl(long double x);
25083 double atan2(double y, double x);
25084 float atan2f(float y, float x);
25085 long double atan2l(long double y, long double x);
25086 double cos(double x);
25087 float cosf(float x);
25088 long double cosl(long double x);
25089 double sin(double x);
25090 float sinf(float x);
25091 long double sinl(long double x);
25092 double tan(double x);
25093 float tanf(float x);
25094 long double tanl(long double x);
25095 double acosh(double x);
25096 float acoshf(float x);
25097 long double acoshl(long double x);
25098 double asinh(double x);
25099 float asinhf(float x);
25100 long double asinhl(long double x);
25101 double atanh(double x);
25102 float atanhf(float x);
25103 long double atanhl(long double x);
25104 double cosh(double x);
25105 float coshf(float x);
25106 long double coshl(long double x);
25107 double sinh(double x);
25108 float sinhf(float x);
25109 long double sinhl(long double x);
25110 double tanh(double x);
25111 float tanhf(float x);
25112 long double tanhl(long double x);
25113 double exp(double x);
25114 float expf(float x);
25115 long double expl(long double x);
25116 double exp2(double x);
25117 float exp2f(float x);
25118 long double exp2l(long double x);
25119 double expm1(double x);
25120 float expm1f(float x);
25121 long double expm1l(long double x);
25122 double frexp(double value, int *exp);
25123 float frexpf(float value, int *exp);
25124 long double frexpl(long double value, int *exp);
25125 int ilogb(double x);
25126 int ilogbf(float x);
25127 int ilogbl(long double x);
25128 double ldexp(double x, int exp);
25129 float ldexpf(float x, int exp);
25130 long double ldexpl(long double x, int exp);
25131 double log(double x);
25132 float logf(float x);
25133 long double logl(long double x);
25134 double log10(double x);
25135 float log10f(float x);
25136 long double log10l(long double x);
25137 double log1p(double x);
25138 float log1pf(float x);
25139 long double log1pl(long double x);
25140 double log2(double x);
25141 float log2f(float x);
25142 long double log2l(long double x);
25143 double logb(double x);
25144 float logbf(float x);
25145 long double logbl(long double x);
25146 double modf(double value, double *iptr);
25147 float modff(float value, float *iptr);
25148 long double modfl(long double value, long double *iptr);
25149 double scalbn(double x, int n);
25150 float scalbnf(float x, int n);
25151 long double scalbnl(long double x, int n);
25152 double scalbln(double x, long int n);
25153 float scalblnf(float x, long int n);
25154 long double scalblnl(long double x, long int n);
25155 double cbrt(double x);
25156 float cbrtf(float x);
25157 long double cbrtl(long double x);
25158 double fabs(double x);
25159 float fabsf(float x);
25160 long double fabsl(long double x);
25161 double hypot(double x, double y);
25162 float hypotf(float x, float y);
25163 long double hypotl(long double x, long double y);
25164 double pow(double x, double y);
25165 float powf(float x, float y);
25166 long double powl(long double x, long double y);
25167 double sqrt(double x);
25168 float sqrtf(float x);
25169 long double sqrtl(long double x);
25170 double erf(double x);
25171 float erff(float x);
25172 long double erfl(long double x);
25173 double erfc(double x);
25174 float erfcf(float x);
25175 long double erfcl(long double x);
25176 double lgamma(double x);
25177 float lgammaf(float x);
25178 long double lgammal(long double x);
25179 double tgamma(double x);
25180 float tgammaf(float x);
25181 long double tgammal(long double x);
25182 double ceil(double x);
25183 float ceilf(float x);
25184 long double ceill(long double x);
25185 double floor(double x);
25186 float floorf(float x);
25187 long double floorl(long double x);
25188 double nearbyint(double x);
25189 float nearbyintf(float x);
25190 long double nearbyintl(long double x);
25191 double rint(double x);
25192 float rintf(float x);
25193 long double rintl(long double x);
25194 long int lrint(double x);
25195 long int lrintf(float x);
25196 long int lrintl(long double x);
25197 long long int llrint(double x);
25198 long long int llrintf(float x);
25199 long long int llrintl(long double x);
25200 double round(double x);
25201 float roundf(float x);
25202 long double roundl(long double x);
25203 long int lround(double x);
25204 long int lroundf(float x);
25205 long int lroundl(long double x);
25206 long long int llround(double x);
25207 long long int llroundf(float x);
25208 long long int llroundl(long double x);
25209 double trunc(double x);
25210 float truncf(float x);
25211 long double truncl(long double x);
25212 double fmod(double x, double y);
25213 float fmodf(float x, float y);
25214 long double fmodl(long double x, long double y);
25215 double remainder(double x, double y);
25216 float remainderf(float x, float y);
25217 long double remainderl(long double x, long double y);
25218 double remquo(double x, double y, int *quo);
25219 float remquof(float x, float y, int *quo);
25220 long double remquol(long double x, long double y,
25221 int *quo);
25222 double copysign(double x, double y);
25223 float copysignf(float x, float y);
25224 long double copysignl(long double x, long double y);
25225 double nan(const char *tagp);
25226 float nanf(const char *tagp);
25227 long double nanl(const char *tagp);
25228 double nextafter(double x, double y);
25229 float nextafterf(float x, float y);
25230 long double nextafterl(long double x, long double y);
25231 double nexttoward(double x, long double y);
25232 float nexttowardf(float x, long double y);
25233 long double nexttowardl(long double x, long double y);
25234 double fdim(double x, double y);
25235 float fdimf(float x, float y);
25236 long double fdiml(long double x, long double y);
25237 double fmax(double x, double y);
25238 float fmaxf(float x, float y);
25239 long double fmaxl(long double x, long double y);
25240 double fmin(double x, double y);
25241 float fminf(float x, float y);
25242 long double fminl(long double x, long double y);
25243 double fma(double x, double y, double z);
25244 float fmaf(float x, float y, float z);
25245 long double fmal(long double x, long double y,
25246 long double z);
25247 int isgreater(real-floating x, real-floating y);
25248 int isgreaterequal(real-floating x, real-floating y);
25249 int isless(real-floating x, real-floating y);
25250 int islessequal(real-floating x, real-floating y);
25251 int islessgreater(real-floating x, real-floating y);
25252 int isunordered(real-floating x, real-floating y);
25253 </pre>
25257 <pre>
25258 jmp_buf
25259 int setjmp(jmp_buf env);
25260 _Noreturn void longjmp(jmp_buf env, int val);
25261 </pre>
25265 <!--page 503 -->
25266 <pre>
25267 sig_atomic_t SIG_IGN SIGILL SIGTERM
25268 SIG_DFL SIGABRT SIGINT
25269 SIG_ERR SIGFPE SIGSEGV
25270 void (*signal(int sig, void (*func)(int)))(int);
25271 int raise(int sig);
25272 </pre>
25276 <pre>
25277 alignas
25278 __alignas_is_defined
25279 </pre>
25283 <pre>
25284 va_list
25285 type va_arg(va_list ap, type);
25286 void va_copy(va_list dest, va_list src);
25287 void va_end(va_list ap);
25288 void va_start(va_list ap, parmN);
25289 </pre>
25293 <!--page 504 -->
25294 <!--page 505 -->
25295 <pre>
25296 ATOMIC_BOOL_LOCK_FREE atomic_uint
25297 ATOMIC_CHAR_LOCK_FREE atomic_long
25298 ATOMIC_CHAR16_T_LOCK_FREE atomic_ulong
25299 ATOMIC_CHAR32_T_LOCK_FREE atomic_llong
25300 ATOMIC_WCHAR_T_LOCK_FREE atomic_ullong
25301 ATOMIC_SHORT_LOCK_FREE atomic_char16_t
25302 ATOMIC_INT_LOCK_FREE atomic_char32_t
25303 ATOMIC_LONG_LOCK_FREE atomic_wchar_t
25304 ATOMIC_LLONG_LOCK_FREE atomic_int_least8_t
25305 ATOMIC_POINTER_LOCK_FREE atomic_uint_least8_t
25306 ATOMIC_FLAG_INIT atomic_int_least16_t
25307 memory_order atomic_uint_least16_t
25308 atomic_flag atomic_int_least32_t
25309 memory_order_relaxed * atomic_uint_least32_t
25310 memory_order_consume atomic_int_least64_t
25311 memory_order_acquire atomic_uint_least64_t
25312 memory_order_release atomic_int_fast8_t
25313 memory_order_acq_rel atomic_uint_fast8_t
25314 memory_order_seq_cst atomic_int_fast16_t
25315 atomic_bool atomic_uint_fast16_t
25316 atomic_char atomic_int_fast32_t
25317 atomic_schar atomic_uint_fast32_t
25318 atomic_uchar atomic_int_fast64_t
25319 atomic_short atomic_uint_fast64_t
25320 atomic_ushort atomic_intptr_t
25321 atomic_int atomic_uintptr_t
25322 atomic_size_t atomic_intmax_t
25323 atomic_ptrdiff_t atomic_uintmax_t
25324 #define ATOMIC_VAR_INIT(C value)
25325 void atomic_init(volatile A *obj, C value);
25326 type kill_dependency(type y);
25327 void atomic_thread_fence(memory_order order);
25328 void atomic_signal_fence(memory_order order);
25329 _Bool atomic_is_lock_free(const volatile A *obj);
25330 void atomic_store(volatile A *object, C desired);
25331 void atomic_store_explicit(volatile A *object,
25332 C desired, memory_order order);
25333 C atomic_load(volatile A *object);
25334 C atomic_load_explicit(volatile A *object,
25335 memory_order order);
25336 C atomic_exchange(volatile A *object, C desired);
25337 C atomic_exchange_explicit(volatile A *object,
25338 C desired, memory_order order);
25339 _Bool atomic_compare_exchange_strong(volatile A *object,
25340 C *expected, C desired);
25341 _Bool atomic_compare_exchange_strong_explicit(
25342 volatile A *object, C *expected, C desired,
25343 memory_order success, memory_order failure);
25344 _Bool atomic_compare_exchange_weak(volatile A *object,
25345 C *expected, C desired);
25346 _Bool atomic_compare_exchange_weak_explicit(
25347 volatile A *object, C *expected, C desired,
25348 memory_order success, memory_order failure);
25349 C atomic_fetch_key(volatile A *object, M operand);
25350 C atomic_fetch_key_explicit(volatile A *object,
25351 M operand, memory_order order);
25352 _Bool atomic_flag_test_and_set(
25353 volatile atomic_flag *object);
25354 _Bool atomic_flag_test_and_set_explicit(
25355 volatile atomic_flag *object, memory_order order);
25356 void atomic_flag_clear(volatile atomic_flag *object);
25357 void atomic_flag_clear_explicit(
25358 volatile atomic_flag *object, memory_order order);
25359 </pre>
25363 <pre>
25364 bool
25365 true
25366 false
25367 __bool_true_false_are_defined
25368 </pre>
25372 <pre>
25373 ptrdiff_t max_align_t NULL
25374 size_t wchar_t
25375 offsetof(type, member-designator)
25376 __STDC_WANT_LIB_EXT1__
25377 rsize_t
25378 </pre>
25382 <!--page 506 -->
25383 <pre>
25384 intN_t INT_LEASTN_MIN PTRDIFF_MAX
25385 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
25386 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
25387 uint_leastN_t INT_FASTN_MIN SIZE_MAX
25388 int_fastN_t INT_FASTN_MAX WCHAR_MIN
25389 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
25390 intptr_t INTPTR_MIN WINT_MIN
25391 uintptr_t INTPTR_MAX WINT_MAX
25392 intmax_t UINTPTR_MAX INTN_C(value)
25393 uintmax_t INTMAX_MIN UINTN_C(value)
25394 INTN_MIN INTMAX_MAX INTMAX_C(value)
25395 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
25396 UINTN_MAX PTRDIFF_MIN
25397 __STDC_WANT_LIB_EXT1__
25398 RSIZE_MAX
25399 </pre>
25403 <!--page 507 -->
25404 <!--page 508 -->
25405 <!--page 509 -->
25406 <pre>
25407 size_t _IOLBF FILENAME_MAX TMP_MAX
25408 FILE _IONBF L_tmpnam stderr
25409 fpos_t BUFSIZ SEEK_CUR stdin
25410 NULL EOF SEEK_END stdout
25411 _IOFBF FOPEN_MAX SEEK_SET
25412 int remove(const char *filename);
25413 int rename(const char *old, const char *new);
25414 FILE *tmpfile(void);
25415 char *tmpnam(char *s);
25416 int fclose(FILE *stream);
25417 int fflush(FILE *stream);
25418 FILE *fopen(const char * restrict filename,
25419 const char * restrict mode);
25420 FILE *freopen(const char * restrict filename,
25421 const char * restrict mode,
25422 FILE * restrict stream);
25423 void setbuf(FILE * restrict stream,
25424 char * restrict buf);
25425 int setvbuf(FILE * restrict stream,
25426 char * restrict buf,
25427 int mode, size_t size);
25428 int fprintf(FILE * restrict stream,
25429 const char * restrict format, ...);
25430 int fscanf(FILE * restrict stream,
25431 const char * restrict format, ...);
25432 int printf(const char * restrict format, ...);
25433 int scanf(const char * restrict format, ...);
25434 int snprintf(char * restrict s, size_t n,
25435 const char * restrict format, ...);
25436 int sprintf(char * restrict s,
25437 const char * restrict format, ...);
25438 int sscanf(const char * restrict s,
25439 const char * restrict format, ...);
25440 int vfprintf(FILE * restrict stream,
25441 const char * restrict format, va_list arg);
25442 int vfscanf(FILE * restrict stream,
25443 const char * restrict format, va_list arg);
25444 int vprintf(const char * restrict format, va_list arg);
25445 int vscanf(const char * restrict format, va_list arg);
25446 int vsnprintf(char * restrict s, size_t n,
25447 const char * restrict format, va_list arg);
25448 int vsprintf(char * restrict s,
25449 const char * restrict format, va_list arg);
25450 int vsscanf(const char * restrict s,
25451 const char * restrict format, va_list arg);
25452 int fgetc(FILE *stream);
25453 char *fgets(char * restrict s, int n,
25454 FILE * restrict stream);
25455 int fputc(int c, FILE *stream);
25456 int fputs(const char * restrict s,
25457 FILE * restrict stream);
25458 int getc(FILE *stream);
25459 int getchar(void);
25460 int putc(int c, FILE *stream);
25461 int putchar(int c);
25462 int puts(const char *s);
25463 int ungetc(int c, FILE *stream);
25464 size_t fread(void * restrict ptr,
25465 size_t size, size_t nmemb,
25466 FILE * restrict stream);
25467 size_t fwrite(const void * restrict ptr,
25468 size_t size, size_t nmemb,
25469 FILE * restrict stream);
25470 int fgetpos(FILE * restrict stream,
25471 fpos_t * restrict pos);
25472 int fseek(FILE *stream, long int offset, int whence);
25473 int fsetpos(FILE *stream, const fpos_t *pos);
25474 long int ftell(FILE *stream);
25475 void rewind(FILE *stream);
25476 void clearerr(FILE *stream);
25477 int feof(FILE *stream);
25478 int ferror(FILE *stream);
25479 void perror(const char *s);
25480 __STDC_WANT_LIB_EXT1__
25481 L_tmpnam_s TMP_MAX_S errno_t rsize_t
25482 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
25483 errno_t tmpnam_s(char *s, rsize_t maxsize);
25484 errno_t fopen_s(FILE * restrict * restrict streamptr,
25485 const char * restrict filename,
25486 const char * restrict mode);
25487 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
25488 const char * restrict filename,
25489 const char * restrict mode,
25490 FILE * restrict stream);
25491 int fprintf_s(FILE * restrict stream,
25492 const char * restrict format, ...);
25493 int fscanf_s(FILE * restrict stream,
25494 const char * restrict format, ...);
25495 int printf_s(const char * restrict format, ...);
25496 int scanf_s(const char * restrict format, ...);
25497 int snprintf_s(char * restrict s, rsize_t n,
25498 const char * restrict format, ...);
25499 int sprintf_s(char * restrict s, rsize_t n,
25500 const char * restrict format, ...);
25501 int sscanf_s(const char * restrict s,
25502 const char * restrict format, ...);
25503 int vfprintf_s(FILE * restrict stream,
25504 const char * restrict format,
25505 va_list arg);
25506 int vfscanf_s(FILE * restrict stream,
25507 const char * restrict format,
25508 va_list arg);
25509 int vprintf_s(const char * restrict format,
25510 va_list arg);
25511 int vscanf_s(const char * restrict format,
25512 va_list arg);
25513 int vsnprintf_s(char * restrict s, rsize_t n,
25514 const char * restrict format,
25515 va_list arg);
25516 int vsprintf_s(char * restrict s, rsize_t n,
25517 const char * restrict format,
25518 va_list arg);
25519 int vsscanf_s(const char * restrict s,
25520 const char * restrict format,
25521 va_list arg);
25522 char *gets_s(char *s, rsize_t n);
25523 </pre>
25527 <!--page 510 -->
25528 <!--page 511 -->
25529 <pre>
25530 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
25531 wchar_t lldiv_t EXIT_SUCCESS
25532 div_t NULL RAND_MAX
25533 double atof(const char *nptr);
25534 int atoi(const char *nptr);
25535 long int atol(const char *nptr);
25536 long long int atoll(const char *nptr);
25537 double strtod(const char * restrict nptr,
25538 char ** restrict endptr);
25539 float strtof(const char * restrict nptr,
25540 char ** restrict endptr);
25541 long double strtold(const char * restrict nptr,
25542 char ** restrict endptr);
25543 long int strtol(const char * restrict nptr,
25544 char ** restrict endptr, int base);
25545 long long int strtoll(const char * restrict nptr,
25546 char ** restrict endptr, int base);
25547 unsigned long int strtoul(
25548 const char * restrict nptr,
25549 char ** restrict endptr, int base);
25550 unsigned long long int strtoull(
25551 const char * restrict nptr,
25552 char ** restrict endptr, int base);
25553 int rand(void);
25554 void srand(unsigned int seed);
25555 void *aligned_alloc(size_t alignment, size_t size);
25556 void *calloc(size_t nmemb, size_t size);
25557 void free(void *ptr);
25558 void *malloc(size_t size);
25559 void *realloc(void *ptr, size_t size);
25560 _Noreturn void abort(void);
25561 int atexit(void (*func)(void));
25562 int at_quick_exit(void (*func)(void));
25563 _Noreturn void exit(int status);
25564 _Noreturn void _Exit(int status);
25565 char *getenv(const char *name);
25566 _Noreturn void quick_exit(int status);
25567 int system(const char *string);
25568 void *bsearch(const void *key, const void *base,
25569 size_t nmemb, size_t size,
25570 int (*compar)(const void *, const void *));
25571 void qsort(void *base, size_t nmemb, size_t size,
25572 int (*compar)(const void *, const void *));
25573 int abs(int j);
25574 long int labs(long int j);
25575 long long int llabs(long long int j);
25576 div_t div(int numer, int denom);
25577 ldiv_t ldiv(long int numer, long int denom);
25578 lldiv_t lldiv(long long int numer,
25579 long long int denom);
25580 int mblen(const char *s, size_t n);
25581 int mbtowc(wchar_t * restrict pwc,
25582 const char * restrict s, size_t n);
25583 int wctomb(char *s, wchar_t wchar);
25584 size_t mbstowcs(wchar_t * restrict pwcs,
25585 const char * restrict s, size_t n);
25586 size_t wcstombs(char * restrict s,
25587 const wchar_t * restrict pwcs, size_t n);
25588 __STDC_WANT_LIB_EXT1__
25589 errno_t
25590 rsize_t
25591 constraint_handler_t
25592 constraint_handler_t set_constraint_handler_s(
25593 constraint_handler_t handler);
25594 void abort_handler_s(
25595 const char * restrict msg,
25596 void * restrict ptr,
25597 errno_t error);
25598 void ignore_handler_s(
25599 const char * restrict msg,
25600 void * restrict ptr,
25601 errno_t error);
25602 errno_t getenv_s(size_t * restrict len,
25603 char * restrict value, rsize_t maxsize,
25604 const char * restrict name);
25605 void *bsearch_s(const void *key, const void *base,
25606 rsize_t nmemb, rsize_t size,
25607 int (*compar)(const void *k, const void *y,
25608 void *context),
25609 void *context);
25610 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
25611 int (*compar)(const void *x, const void *y,
25612 void *context),
25613 void *context);
25614 errno_t wctomb_s(int * restrict status,
25615 char * restrict s,
25616 rsize_t smax,
25617 wchar_t wc);
25618 errno_t mbstowcs_s(size_t * restrict retval,
25619 wchar_t * restrict dst, rsize_t dstmax,
25620 const char * restrict src, rsize_t len);
25621 errno_t wcstombs_s(size_t * restrict retval,
25622 char * restrict dst, rsize_t dstmax,
25623 const wchar_t * restrict src, rsize_t len);
25624 </pre>
25626 <pre>
25627 noreturn
25628 </pre>
25632 <!--page 512 -->
25633 <!--page 513 -->
25634 <pre>
25635 size_t
25636 NULL
25637 void *memcpy(void * restrict s1,
25638 const void * restrict s2, size_t n);
25639 void *memmove(void *s1, const void *s2, size_t n);
25640 char *strcpy(char * restrict s1,
25641 const char * restrict s2);
25642 char *strncpy(char * restrict s1,
25643 const char * restrict s2, size_t n);
25644 char *strcat(char * restrict s1,
25645 const char * restrict s2);
25646 char *strncat(char * restrict s1,
25647 const char * restrict s2, size_t n);
25648 int memcmp(const void *s1, const void *s2, size_t n);
25649 int strcmp(const char *s1, const char *s2);
25650 int strcoll(const char *s1, const char *s2);
25651 int strncmp(const char *s1, const char *s2, size_t n);
25652 size_t strxfrm(char * restrict s1,
25653 const char * restrict s2, size_t n);
25654 void *memchr(const void *s, int c, size_t n);
25655 char *strchr(const char *s, int c);
25656 size_t strcspn(const char *s1, const char *s2);
25657 char *strpbrk(const char *s1, const char *s2);
25658 char *strrchr(const char *s, int c);
25659 size_t strspn(const char *s1, const char *s2);
25660 char *strstr(const char *s1, const char *s2);
25661 char *strtok(char * restrict s1,
25662 const char * restrict s2);
25663 void *memset(void *s, int c, size_t n);
25664 char *strerror(int errnum);
25665 size_t strlen(const char *s);
25666 __STDC_WANT_LIB_EXT1__
25667 errno_t
25668 rsize_t
25669 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
25670 const void * restrict s2, rsize_t n);
25671 errno_t memmove_s(void *s1, rsize_t s1max,
25672 const void *s2, rsize_t n);
25673 errno_t strcpy_s(char * restrict s1,
25674 rsize_t s1max,
25675 const char * restrict s2);
25676 errno_t strncpy_s(char * restrict s1,
25677 rsize_t s1max,
25678 const char * restrict s2,
25679 rsize_t n);
25680 errno_t strcat_s(char * restrict s1,
25681 rsize_t s1max,
25682 const char * restrict s2);
25683 errno_t strncat_s(char * restrict s1,
25684 rsize_t s1max,
25685 const char * restrict s2,
25686 rsize_t n);
25687 char *strtok_s(char * restrict s1,
25688 rsize_t * restrict s1max,
25689 const char * restrict s2,
25690 char ** restrict ptr);
25691 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
25692 errno_t strerror_s(char *s, rsize_t maxsize,
25693 errno_t errnum);
25694 size_t strerrorlen_s(errno_t errnum);
25695 size_t strnlen_s(const char *s, size_t maxsize);
25696 </pre>
25700 <pre>
25701 acos sqrt fmod nextafter
25702 asin fabs frexp nexttoward
25703 atan atan2 hypot remainder
25704 acosh cbrt ilogb remquo
25705 asinh ceil ldexp rint
25706 atanh copysign lgamma round
25707 cos erf llrint scalbn
25708 sin erfc llround scalbln
25709 tan exp2 log10 tgamma
25710 cosh expm1 log1p trunc
25711 sinh fdim log2 carg
25712 tanh floor logb cimag
25713 exp fma lrint conj
25714 log fmax lround cproj
25715 pow fmin nearbyint creal
25716 </pre>
25720 <!--page 514 -->
25721 <pre>
25722 thread_local once_flag
25723 ONCE_FLAG_INIT mtx_plain *
25724 TSS_DTOR_ITERATIONS mtx_recursive
25725 cnd_t mtx_timed
25726 thrd_t thrd_timedout
25727 tss_t thrd_success
25728 mtx_t thrd_busy
25729 tss_dtor_t thrd_error
25730 thrd_start_t thrd_nomem
25731 void call_once(once_flag *flag, void (*func)(void));
25732 int cnd_broadcast(cnd_t *cond);
25733 void cnd_destroy(cnd_t *cond);
25734 int cnd_init(cnd_t *cond);
25735 int cnd_signal(cnd_t *cond);
25736 int cnd_timedwait(cnd_t *restrict cond,
25737 mtx_t *restrict mtx,
25738 const struct timespec *restrict ts);
25739 int cnd_wait(cnd_t *cond, mtx_t *mtx);
25740 void mtx_destroy(mtx_t *mtx);
25741 int mtx_init(mtx_t *mtx, int type);
25742 int mtx_lock(mtx_t *mtx);
25743 int mtx_timedlock(mtx_t *restrict mtx,
25744 const struct timespec *restrict ts);
25745 int mtx_trylock(mtx_t *mtx);
25746 int mtx_unlock(mtx_t *mtx);
25747 int thrd_create(thrd_t *thr, thrd_start_t func,
25748 void *arg);
25749 thrd_t thrd_current(void);
25750 int thrd_detach(thrd_t thr);
25751 int thrd_equal(thrd_t thr0, thrd_t thr1);
25752 _Noreturn void thrd_exit(int res);
25753 int thrd_join(thrd_t thr, int *res);
25754 int thrd_sleep(const struct timespec *duration,
25755 struct timespec *remaining);
25756 void thrd_yield(void);
25757 int tss_create(tss_t *key, tss_dtor_t dtor);
25758 void tss_delete(tss_t key);
25759 void *tss_get(tss_t key);
25760 int tss_set(tss_t key, void *val);
25761 </pre>
25765 <!--page 515 -->
25766 <pre>
25767 NULL size_t struct timespec
25768 CLOCKS_PER_SEC clock_t struct tm
25769 TIME_UTC time_t
25770 clock_t clock(void);
25771 double difftime(time_t time1, time_t time0);
25772 time_t mktime(struct tm *timeptr);
25773 time_t time(time_t *timer);
25774 int timespec_get(timespec *ts, int base);
25775 char *asctime(const struct tm *timeptr);
25776 char *ctime(const time_t *timer);
25777 struct tm *gmtime(const time_t *timer);
25778 struct tm *localtime(const time_t *timer);
25779 size_t strftime(char * restrict s,
25780 size_t maxsize,
25781 const char * restrict format,
25782 const struct tm * restrict timeptr);
25783 __STDC_WANT_LIB_EXT1__
25784 errno_t
25785 rsize_t
25786 errno_t asctime_s(char *s, rsize_t maxsize,
25787 const struct tm *timeptr);
25788 errno_t ctime_s(char *s, rsize_t maxsize,
25789 const time_t *timer);
25790 struct tm *gmtime_s(const time_t * restrict timer,
25791 struct tm * restrict result);
25792 struct tm *localtime_s(const time_t * restrict timer,
25793 struct tm * restrict result);
25794 </pre>
25798 <pre>
25799 mbstate_t size_t char16_t char32_t
25800 size_t mbrtoc16(char16_t * restrict pc16,
25801 const char * restrict s, size_t n,
25802 mbstate_t * restrict ps);
25803 size_t c16rtomb(char * restrict s, char16_t c16,
25804 mbstate_t * restrict ps);
25805 size_t mbrtoc32(char32_t * restrict pc32,
25806 const char * restrict s, size_t n,
25807 mbstate_t * restrict ps);
25808 size_t c32rtomb(char * restrict s, char32_t c32,
25809 mbstate_t * restrict ps);
25810 </pre>
25813 <h3><a name="B.28" href="#B.28">B.28 Extended multibyte/wide character utilities <wchar.h></a></h3>
25814 <!--page 516 -->
25815 <!--page 517 -->
25816 <!--page 518 -->
25817 <!--page 519 -->
25818 <!--page 520 -->
25819 <pre>
25820 wchar_t wint_t WCHAR_MAX
25821 size_t struct tm WCHAR_MIN
25822 mbstate_t NULL WEOF
25823 int fwprintf(FILE * restrict stream,
25824 const wchar_t * restrict format, ...);
25825 int fwscanf(FILE * restrict stream,
25826 const wchar_t * restrict format, ...);
25827 int swprintf(wchar_t * restrict s, size_t n,
25828 const wchar_t * restrict format, ...);
25829 int swscanf(const wchar_t * restrict s,
25830 const wchar_t * restrict format, ...);
25831 int vfwprintf(FILE * restrict stream,
25832 const wchar_t * restrict format, va_list arg);
25833 int vfwscanf(FILE * restrict stream,
25834 const wchar_t * restrict format, va_list arg);
25835 int vswprintf(wchar_t * restrict s, size_t n,
25836 const wchar_t * restrict format, va_list arg);
25837 int vswscanf(const wchar_t * restrict s,
25838 const wchar_t * restrict format, va_list arg);
25839 int vwprintf(const wchar_t * restrict format,
25840 va_list arg);
25841 int vwscanf(const wchar_t * restrict format,
25842 va_list arg);
25843 int wprintf(const wchar_t * restrict format, ...);
25844 int wscanf(const wchar_t * restrict format, ...);
25845 wint_t fgetwc(FILE *stream);
25846 wchar_t *fgetws(wchar_t * restrict s, int n,
25847 FILE * restrict stream);
25848 wint_t fputwc(wchar_t c, FILE *stream);
25849 int fputws(const wchar_t * restrict s,
25850 FILE * restrict stream);
25851 int fwide(FILE *stream, int mode);
25852 wint_t getwc(FILE *stream);
25853 wint_t getwchar(void);
25854 wint_t putwc(wchar_t c, FILE *stream);
25855 wint_t putwchar(wchar_t c);
25856 wint_t ungetwc(wint_t c, FILE *stream);
25857 double wcstod(const wchar_t * restrict nptr,
25858 wchar_t ** restrict endptr);
25859 float wcstof(const wchar_t * restrict nptr,
25860 wchar_t ** restrict endptr);
25861 long double wcstold(const wchar_t * restrict nptr,
25862 wchar_t ** restrict endptr);
25863 long int wcstol(const wchar_t * restrict nptr,
25864 wchar_t ** restrict endptr, int base);
25865 long long int wcstoll(const wchar_t * restrict nptr,
25866 wchar_t ** restrict endptr, int base);
25867 unsigned long int wcstoul(const wchar_t * restrict nptr,
25868 wchar_t ** restrict endptr, int base);
25869 unsigned long long int wcstoull(
25870 const wchar_t * restrict nptr,
25871 wchar_t ** restrict endptr, int base);
25872 wchar_t *wcscpy(wchar_t * restrict s1,
25873 const wchar_t * restrict s2);
25874 wchar_t *wcsncpy(wchar_t * restrict s1,
25875 const wchar_t * restrict s2, size_t n);
25876 wchar_t *wmemcpy(wchar_t * restrict s1,
25877 const wchar_t * restrict s2, size_t n);
25878 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
25879 size_t n);
25880 wchar_t *wcscat(wchar_t * restrict s1,
25881 const wchar_t * restrict s2);
25882 wchar_t *wcsncat(wchar_t * restrict s1,
25883 const wchar_t * restrict s2, size_t n);
25884 int wcscmp(const wchar_t *s1, const wchar_t *s2);
25885 int wcscoll(const wchar_t *s1, const wchar_t *s2);
25886 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
25887 size_t n);
25888 size_t wcsxfrm(wchar_t * restrict s1,
25889 const wchar_t * restrict s2, size_t n);
25890 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
25891 size_t n);
25892 wchar_t *wcschr(const wchar_t *s, wchar_t c);
25893 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
25894 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
25895 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
25896 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
25897 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
25898 wchar_t *wcstok(wchar_t * restrict s1,
25899 const wchar_t * restrict s2,
25900 wchar_t ** restrict ptr);
25901 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
25902 size_t wcslen(const wchar_t *s);
25903 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
25904 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
25905 const wchar_t * restrict format,
25906 const struct tm * restrict timeptr);
25907 wint_t btowc(int c);
25908 int wctob(wint_t c);
25909 int mbsinit(const mbstate_t *ps);
25910 size_t mbrlen(const char * restrict s, size_t n,
25911 mbstate_t * restrict ps);
25912 size_t mbrtowc(wchar_t * restrict pwc,
25913 const char * restrict s, size_t n,
25914 mbstate_t * restrict ps);
25915 size_t wcrtomb(char * restrict s, wchar_t wc,
25916 mbstate_t * restrict ps);
25917 size_t mbsrtowcs(wchar_t * restrict dst,
25918 const char ** restrict src, size_t len,
25919 mbstate_t * restrict ps);
25920 size_t wcsrtombs(char * restrict dst,
25921 const wchar_t ** restrict src, size_t len,
25922 mbstate_t * restrict ps);
25923 __STDC_WANT_LIB_EXT1__
25924 errno_t
25925 rsize_t
25926 int fwprintf_s(FILE * restrict stream,
25927 const wchar_t * restrict format, ...);
25928 int fwscanf_s(FILE * restrict stream,
25929 const wchar_t * restrict format, ...);
25930 int snwprintf_s(wchar_t * restrict s,
25931 rsize_t n,
25932 const wchar_t * restrict format, ...);
25933 int swprintf_s(wchar_t * restrict s, rsize_t n,
25934 const wchar_t * restrict format, ...);
25935 int swscanf_s(const wchar_t * restrict s,
25936 const wchar_t * restrict format, ...);
25937 int vfwprintf_s(FILE * restrict stream,
25938 const wchar_t * restrict format,
25939 va_list arg);
25940 int vfwscanf_s(FILE * restrict stream,
25941 const wchar_t * restrict format, va_list arg);
25942 int vsnwprintf_s(wchar_t * restrict s,
25943 rsize_t n,
25944 const wchar_t * restrict format,
25945 va_list arg);
25946 int vswprintf_s(wchar_t * restrict s,
25947 rsize_t n,
25948 const wchar_t * restrict format,
25949 va_list arg);
25950 int vswscanf_s(const wchar_t * restrict s,
25951 const wchar_t * restrict format,
25952 va_list arg);
25953 int vwprintf_s(const wchar_t * restrict format,
25954 va_list arg);
25955 int vwscanf_s(const wchar_t * restrict format,
25956 va_list arg);
25957 int wprintf_s(const wchar_t * restrict format, ...);
25958 int wscanf_s(const wchar_t * restrict format, ...);
25959 errno_t wcscpy_s(wchar_t * restrict s1,
25960 rsize_t s1max,
25961 const wchar_t * restrict s2);
25962 errno_t wcsncpy_s(wchar_t * restrict s1,
25963 rsize_t s1max,
25964 const wchar_t * restrict s2,
25965 rsize_t n);
25966 errno_t wmemcpy_s(wchar_t * restrict s1,
25967 rsize_t s1max,
25968 const wchar_t * restrict s2,
25969 rsize_t n);
25970 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
25971 const wchar_t *s2, rsize_t n);
25972 errno_t wcscat_s(wchar_t * restrict s1,
25973 rsize_t s1max,
25974 const wchar_t * restrict s2);
25975 errno_t wcsncat_s(wchar_t * restrict s1,
25976 rsize_t s1max,
25977 const wchar_t * restrict s2,
25978 rsize_t n);
25979 wchar_t *wcstok_s(wchar_t * restrict s1,
25980 rsize_t * restrict s1max,
25981 const wchar_t * restrict s2,
25982 wchar_t ** restrict ptr);
25983 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
25984 errno_t wcrtomb_s(size_t * restrict retval,
25985 char * restrict s, rsize_t smax,
25986 wchar_t wc, mbstate_t * restrict ps);
25987 errno_t mbsrtowcs_s(size_t * restrict retval,
25988 wchar_t * restrict dst, rsize_t dstmax,
25989 const char ** restrict src, rsize_t len,
25990 mbstate_t * restrict ps);
25991 errno_t wcsrtombs_s(size_t * restrict retval,
25992 char * restrict dst, rsize_t dstmax,
25993 const wchar_t ** restrict src, rsize_t len,
25994 mbstate_t * restrict ps);
25995 </pre>
25998 <h3><a name="B.29" href="#B.29">B.29 Wide character classification and mapping utilities <wctype.h></a></h3>
25999 <!--page 521 -->
26000 <pre>
26001 wint_t wctrans_t wctype_t WEOF
26002 int iswalnum(wint_t wc);
26003 int iswalpha(wint_t wc);
26004 int iswblank(wint_t wc);
26005 int iswcntrl(wint_t wc);
26006 int iswdigit(wint_t wc);
26007 int iswgraph(wint_t wc);
26008 int iswlower(wint_t wc);
26009 int iswprint(wint_t wc);
26010 int iswpunct(wint_t wc);
26011 int iswspace(wint_t wc);
26012 int iswupper(wint_t wc);
26013 int iswxdigit(wint_t wc);
26014 int iswctype(wint_t wc, wctype_t desc);
26015 wctype_t wctype(const char *property);
26016 wint_t towlower(wint_t wc);
26017 wint_t towupper(wint_t wc);
26018 wint_t towctrans(wint_t wc, wctrans_t desc);
26019 wctrans_t wctrans(const char *property);
26020 </pre>
26024 <pre>
26025 (informative)
26026 Sequence points
26027 </pre>
26030 <ul>
26031 <li> Between the evaluations of the function designator and actual arguments in a function
26033 <li> Between the evaluations of the first and second operands of the following operators:
26034 logical AND && (<a href="#6.5.13">6.5.13</a>); logical OR || (<a href="#6.5.14">6.5.14</a>); comma , (<a href="#6.5.17">6.5.17</a>).
26035 <li> Between the evaluations of the first operand of the conditional ? : operator and
26038 <li> Between the evaluation of a full expression and the next full expression to be
26039 evaluated. The following are full expressions: an initializer that is not part of a
26040 compound literal (<a href="#6.7.9">6.7.9</a>); the expression in an expression statement (<a href="#6.8.3">6.8.3</a>); the
26041 controlling expression of a selection statement (if or switch) (<a href="#6.8.4">6.8.4</a>); the
26042 controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the (optional)
26043 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the (optional) expression in a return
26046 <li> After the actions associated with each formatted input/output function conversion
26048 <li> Immediately before and immediately after each call to a comparison function, and
26049 also between any call to a comparison function and any movement of the objects
26051 <!--page 522 -->
26052 </ul>
26056 <pre>
26057 (normative)
26058 Universal character names for identifiers
26059 </pre>
26061 This clause lists the hexadecimal code values that are valid in universal character names
26062 in identifiers.
26078 3040-D7FF
26080 F900-FD3D, FD40-FDCF, FDF0-FE44, FE47-FFFD
26084 B0000-BFFFD, C0000-CFFFD, D0000-DFFFD, E0000-EFFFD
26090 <!--page 523 -->
26094 <pre>
26095 (informative)
26096 Implementation limits
26097 </pre>
26099 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
26100 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
26101 with the same sign. The values shall all be constant expressions suitable for use in #if
26102 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
26103 <pre>
26104 #define CHAR_BIT 8
26105 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
26106 #define CHAR_MIN 0 or SCHAR_MIN
26107 #define INT_MAX +32767
26108 #define INT_MIN -32767
26109 #define LONG_MAX +2147483647
26110 #define LONG_MIN -2147483647
26111 #define LLONG_MAX +9223372036854775807
26112 #define LLONG_MIN -9223372036854775807
26113 #define MB_LEN_MAX 1
26114 #define SCHAR_MAX +127
26115 #define SCHAR_MIN -127
26116 #define SHRT_MAX +32767
26117 #define SHRT_MIN -32767
26118 #define UCHAR_MAX 255
26119 #define USHRT_MAX 65535
26120 #define UINT_MAX 65535
26121 #define ULONG_MAX 4294967295
26122 #define ULLONG_MAX 18446744073709551615
26123 </pre>
26125 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
26126 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
26127 directives; all floating values shall be constant expressions. The components are
26130 The values given in the following list shall be replaced by implementation-defined
26131 expressions:
26132 <pre>
26133 #define FLT_EVAL_METHOD
26134 #define FLT_ROUNDS
26135 </pre>
26137 The values given in the following list shall be replaced by implementation-defined
26138 constant expressions that are greater or equal in magnitude (absolute value) to those
26139 shown, with the same sign:
26140 <!--page 524 -->
26141 <pre>
26142 #define DLB_DECIMAL_DIG 10
26143 #define DBL_DIG 10
26144 #define DBL_MANT_DIG
26145 #define DBL_MAX_10_EXP +37
26146 #define DBL_MAX_EXP
26147 #define DBL_MIN_10_EXP -37
26148 #define DBL_MIN_EXP
26149 #define DECIMAL_DIG 10
26150 #define FLT_DECIMAL_DIG 6
26151 #define FLT_DIG 6
26152 #define FLT_MANT_DIG
26153 #define FLT_MAX_10_EXP +37
26154 #define FLT_MAX_EXP
26155 #define FLT_MIN_10_EXP -37
26156 #define FLT_MIN_EXP
26157 #define FLT_RADIX 2
26158 #define LDLB_DECIMAL_DIG 10
26159 #define LDBL_DIG 10
26160 #define LDBL_MANT_DIG
26161 #define LDBL_MAX_10_EXP +37
26162 #define LDBL_MAX_EXP
26163 #define LDBL_MIN_10_EXP -37
26164 #define LDBL_MIN_EXP
26165 </pre>
26167 The values given in the following list shall be replaced by implementation-defined
26168 constant expressions with values that are greater than or equal to those shown:
26169 <pre>
26170 #define DBL_MAX 1E+37
26171 #define FLT_MAX 1E+37
26172 #define LDBL_MAX 1E+37
26173 </pre>
26175 The values given in the following list shall be replaced by implementation-defined
26176 constant expressions with (positive) values that are less than or equal to those shown:
26177 <!--page 525 -->
26178 <pre>
26179 #define DBL_EPSILON 1E-9
26180 #define DBL_MIN 1E-37
26181 #define FLT_EPSILON 1E-5
26182 #define FLT_MIN 1E-37
26183 #define LDBL_EPSILON 1E-9
26184 #define LDBL_MIN 1E-37
26185 </pre>
26189 <pre>
26190 (normative)
26191 IEC 60559 floating-point arithmetic
26192 </pre>
26197 This annex specifies C language support for the IEC 60559 floating-point standard. The
26198 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
26203 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
26205 defines __STDC_IEC_559__ shall conform to the specifications in this annex.<sup><a href="#note356"><b>356)</b></a></sup>
26206 Where a binding between the C language and IEC 60559 is indicated, the
26207 IEC 60559-specified behavior is adopted by reference, unless stated otherwise. Since
26208 negative and positive infinity are representable in IEC 60559 formats, all real numbers lie
26209 within the range of representable values.
26212 <p><small><a name="note356" href="#note356">356)</a> Implementations that do not define __STDC_IEC_559__ are not required to conform to these
26213 specifications.
26214 </small>
26219 The C floating types match the IEC 60559 formats as follows:
26220 <ul>
26223 <li> The long double type matches an IEC 60559 extended format,<sup><a href="#note357"><b>357)</b></a></sup> else a
26225 </ul>
26226 Any non-IEC 60559 extended format used for the long double type shall have more
26227 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note358"><b>358)</b></a></sup>
26232 <!--page 526 -->
26235 The long double type should match an IEC 60559 extended format.
26238 <p><small><a name="note357" href="#note357">357)</a> ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
26240 </small>
26241 <p><small><a name="note358" href="#note358">358)</a> A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
26242 all double values.
26243 </small>
26248 This specification does not define the behavior of signaling NaNs.<sup><a href="#note359"><b>359)</b></a></sup> It generally uses
26249 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
26250 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
26253 <p><small><a name="note359" href="#note359">359)</a> Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
26254 sufficient for closure of the arithmetic.
26255 </small>
26260 C operators and functions provide IEC 60559 required and recommended facilities as
26261 listed below.
26262 <ul>
26264 divide operations.
26265 <li> The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
26266 <li> The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
26267 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
26268 with additional information.
26269 <li> The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
26270 floating-point number to an integer value (in the same precision). The nearbyint
26271 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
26272 Appendix to ANSI/IEEE 854.
26274 floating-point precisions.
26276 from integer to floating point.
26278 but always round toward zero.
26279 <li> The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
26280 conversions, which honor the directed rounding mode, from floating point to the
26281 long int and long long int integer formats. The lrint and llrint
26282 functions can be used to implement IEC 60559 conversions from floating to other
26283 integer formats.
26284 <li> The translation time conversion of floating constants and the strtod, strtof,
26285 strtold, fprintf, fscanf, and related library functions in <a href="#7.22"><stdlib.h></a>,
26288 <!--page 527 -->
26289 <a href="#7.21"><stdio.h></a>, and <a href="#7.29"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
26290 strtold function in <a href="#7.22"><stdlib.h></a> provides the conv function recommended in the
26291 Appendix to ANSI/IEEE 854.
26293 identifies a need for additional comparison predicates to facilitate writing code that
26294 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
26296 supplement the language operators to address this need. The islessgreater and
26297 isunordered macros provide respectively a quiet version of the <> predicate and
26298 the unordered predicate recommended in the Appendix to IEC 60559.
26299 <li> The feclearexcept, feraiseexcept, and fetestexcept functions in
26300 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
26301 exception status flags. The fegetexceptflag and fesetexceptflag
26302 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
26303 one time. These functions are used in conjunction with the type fexcept_t and the
26304 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
26306 <li> The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
26307 to select among the IEC 60559 directed rounding modes represented by the rounding
26310 IEC 60559 directed rounding modes.
26311 <li> The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
26312 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
26313 the IEC 60559 status flags and control modes.
26314 <li> The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
26315 recommended in the Appendix to IEC 60559.
26316 <li> The fabs functions in <a href="#7.12"><math.h></a> provide the abs function recommended in the
26317 Appendix to IEC 60559.
26318 <li> The unary minus (-) operator provides the unary minus (-) operation recommended
26319 in the Appendix to IEC 60559.
26320 <li> The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
26321 recommended in the Appendix to IEC 60559.
26322 <li> The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
26324 <li> The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
26325 function recommended in the Appendix to IEC 60559 (but with a minor change to
26326 <!--page 528 -->
26327 better handle signed zeros).
26328 <li> The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
26329 the Appendix to IEC 60559.
26330 <li> The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
26331 Appendix to IEC 60559.
26332 <li> The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
26333 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
26334 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
26335 function recommended in the Appendix to IEC 60559 (except that the classification
26337 </ul>
26342 If the integer type is _Bool, <a href="#6.3.1.2">6.3.1.2</a> applies and no floating-point exceptions are raised
26343 (even for NaN). Otherwise, if the floating value is infinite or NaN or if the integral part
26344 of the floating value exceeds the range of the integer type, then the ''invalid'' floating-
26345 point exception is raised and the resulting value is unspecified. Otherwise, the resulting
26346 value is determined by <a href="#6.3.1.4">6.3.1.4</a>. Conversion of an integral floating value that does not
26347 exceed the range of the integer type raises no floating-point exceptions; whether
26348 conversion of a non-integral floating value raises the ''inexact'' floating-point exception is
26352 <p><small><a name="note360" href="#note360">360)</a> ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
26353 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
26354 cases where it matters, library functions can be used to effect such conversions with or without raising
26355 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
26357 </small>
26362 Conversion from the widest supported IEC 60559 format to decimal with
26363 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note361"><b>361)</b></a></sup>
26365 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
26366 particular, conversion between any supported IEC 60559 format and decimal with
26367 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
26368 rounding mode), which assures that conversion from the widest supported IEC 60559
26369 format to decimal with DECIMAL_DIG digits and back is the identity function.
26373 <!--page 529 -->
26375 Functions such as strtod that convert character sequences to floating types honor the
26376 rounding direction. Hence, if the rounding direction might be upward or downward, the
26377 implementation cannot convert a minus-signed sequence by negating the converted
26378 unsigned sequence.
26381 <p><small><a name="note361" href="#note361">361)</a> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
26385 </small>
26389 If the return expression is evaluated in a floating-point format different from the return
26390 type, the expression is converted as if by assignment<sup><a href="#note362"><b>362)</b></a></sup> to the return type of the function
26391 and the resulting value is returned to the caller.
26394 <p><small><a name="note362" href="#note362">362)</a> Assignment removes any extra range and precision.
26395 </small>
26400 A contracted expression is correctly rounded (once) and treats infinities, NaNs, signed
26401 zeros, subnormals, and the rounding directions in a manner consistent with the basic
26402 arithmetic operations covered by IEC 60559.
26405 A contracted expression should raise floating-point exceptions in a manner generally
26406 consistent with the basic arithmetic operations.
26411 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
26412 point exception status flags and directed-rounding control modes. It includes also
26413 IEC 60559 dynamic rounding precision and trap enablement modes, if the
26417 <p><small><a name="note363" href="#note363">363)</a> This specification does not require dynamic rounding precision nor trap enablement modes.
26418 </small>
26423 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
26424 status flags, and that rounding control modes can be set explicitly to affect result values of
26425 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
26426 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
26432 <!--page 530 -->
26435 <p><small><a name="note364" href="#note364">364)</a> If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
26436 point control modes will be the default ones and the floating-point status flags will not be tested,
26438 </small>
26443 During translation the IEC 60559 default modes are in effect:
26444 <ul>
26445 <li> The rounding direction mode is rounding to nearest.
26446 <li> The rounding precision mode (if supported) is set so that results are not shortened.
26447 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
26448 </ul>
26451 The implementation should produce a diagnostic message for each translation-time
26452 floating-point exception, other than ''inexact'';<sup><a href="#note365"><b>365)</b></a></sup> the implementation should then
26453 proceed with the translation of the program.
26456 <p><small><a name="note365" href="#note365">365)</a> As floating constants are converted to appropriate internal representations at translation time, their
26457 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
26458 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
26459 strtod, provide execution-time conversion of numeric strings.
26460 </small>
26465 At program startup the floating-point environment is initialized as prescribed by
26466 IEC 60559:
26467 <ul>
26468 <li> All floating-point exception status flags are cleared.
26469 <li> The rounding direction mode is rounding to nearest.
26470 <li> The dynamic rounding precision mode (if supported) is set so that results are not
26471 shortened.
26472 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
26473 </ul>
26478 An arithmetic constant expression of floating type, other than one in an initializer for an
26479 object that has static or thread storage duration, is evaluated (as if) during execution; thus,
26480 it is affected by any operative floating-point control modes and raises floating-point
26481 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
26484 EXAMPLE
26488 <!--page 531 -->
26489 <pre>
26491 #pragma STDC FENV_ACCESS ON
26492 void f(void)
26493 {
26498 /* ... */
26499 }
26500 </pre>
26502 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
26503 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
26504 execution time.
26508 <p><small><a name="note366" href="#note366">366)</a> Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like 1.0/3.0
26511 efficiency of translation-time evaluation through static initialization, such as
26513 <pre>
26515 </pre>
26516 </small>
26521 All computation for automatic initialization is done (as if) at execution time; thus, it is
26522 affected by any operative modes and raises floating-point exceptions as required by
26523 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
26524 for initialization of objects that have static or thread storage duration is done (as if) at
26525 translation time.
26527 EXAMPLE
26528 <pre>
26530 #pragma STDC FENV_ACCESS ON
26531 void f(void)
26532 {
26533 float u[] = { 1.1e75 }; // raises exceptions
26534 static float v = 1.1e75; // does not raise exceptions
26535 float w = 1.1e75; // raises exceptions
26536 double x = 1.1e75; // may raise exceptions
26537 float y = 1.1e75f; // may raise exceptions
26538 long double z = 1.1e75; // does not raise exceptions
26539 /* ... */
26540 }
26541 </pre>
26543 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
26544 done at translation time. The automatic initialization of u and w require an execution-time conversion to
26545 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
26546 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
26547 conversions is not to a narrower format, in which case no floating-point exception is raised.<sup><a href="#note367"><b>367)</b></a></sup> The
26548 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
26549 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
26553 <!--page 532 -->
26554 their internal representations occur at translation time in all cases.
26558 <p><small><a name="note367" href="#note367">367)</a> Use of float_t and double_t variables increases the likelihood of translation-time computation.
26559 For example, the automatic initialization
26561 <pre>
26562 double_t x = 1.1e75;
26563 </pre>
26564 could be done at translation time, regardless of the expression evaluation method.
26565 </small>
26570 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
26571 change floating-point status flags and control modes just as indicated by their
26572 specifications (including conformance to IEC 60559). They do not change flags or modes
26573 (so as to be detectable by the user) in any other cases.
26575 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
26576 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
26577 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
26578 before ''inexact''.
26583 This section identifies code transformations that might subvert IEC 60559-specified
26584 behavior, and others that do not.
26589 Floating-point arithmetic operations and external function calls may entail side effects
26590 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
26591 ''on''. The flags and modes in the floating-point environment may be regarded as global
26592 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
26593 flags.
26595 Concern about side effects may inhibit code motion and removal of seemingly useless
26596 code. For example, in
26597 <pre>
26599 #pragma STDC FENV_ACCESS ON
26600 void f(double x)
26601 {
26602 /* ... */
26604 /* ... */
26605 }
26606 </pre>
26607 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
26609 course these optimizations are valid if the implementation can rule out the nettlesome
26610 cases.)
26612 This specification does not require support for trap handlers that maintain information
26613 about the order or count of floating-point exceptions. Therefore, between function calls,
26614 floating-point exceptions need not be precise: the actual order and number of occurrences
26616 <!--page 533 -->
26617 the preceding loop could be treated as
26618 <pre>
26620 </pre>
26626 <pre>
26627 generally do not yield numerically equivalent expressions, if the
26628 constants are exact then such transformations can be made on
26629 IEC 60559 machines and others that round perfectly.
26630 </pre>
26632 <pre>
26634 </pre>
26636 <pre>
26637 infinite, or NaN.
26638 </pre>
26640 <pre>
26641 IEC 60559 machines, among others).
26642 </pre>
26644 <pre>
26645 is +0 but -(1 - 1) is -0 (in the default rounding direction).<sup><a href="#note369"><b>369)</b></a></sup>
26646 </pre>
26648 <pre>
26649 infinite.
26650 </pre>
26652 <pre>
26653 infinite, or -0.
26654 </pre>
26656 <pre>
26658 </pre>
26660 <pre>
26662 FENV_ACCESS pragma is ''off'', promising default rounding, then
26663 the implementation can replace x - 0 by x, even if x might be zero.
26664 </pre>
26666 <pre>
26668 downward).
26669 </pre>
26671 <!--page 534 -->
26674 <p><small><a name="note368" href="#note368">368)</a> Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
26675 other transformations that remove arithmetic operators.
26676 </small>
26677 <p><small><a name="note369" href="#note369">369)</a> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
26678 Examples include:
26680 <pre>
26682 </pre>
26683 and
26685 <pre>
26686 conj(csqrt(z)) is csqrt(conj(z)),
26687 </pre>
26688 for complex z.
26689 </small>
26694 x != x -> false The expression x != x is true if x is a NaN.
26695 x = x -> true The expression x = x is false if x is a NaN.
26696 x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically equal, these
26697 <pre>
26698 expressions are not equivalent because of side effects when x or y is a
26699 NaN and the state of the FENV_ACCESS pragma is ''on''. This
26700 transformation, which would be desirable if extra code were required
26701 to cause the ''invalid'' floating-point exception for unordered cases,
26702 could be performed provided the state of the FENV_ACCESS pragma
26703 is ''off''.
26704 </pre>
26705 The sense of relational operators shall be maintained. This includes handling unordered
26706 cases as expressed by the source code.
26708 EXAMPLE
26709 <pre>
26710 // calls g and raises ''invalid'' if a and b are unordered
26711 if (a < b)
26712 f();
26713 else
26714 g();
26715 </pre>
26716 is not equivalent to
26717 <pre>
26718 // calls f and raises ''invalid'' if a and b are unordered
26719 if (a >= b)
26720 g();
26721 else
26722 f();
26723 </pre>
26724 nor to
26725 <pre>
26726 // calls f without raising ''invalid'' if a and b are unordered
26727 if (isgreaterequal(a,b))
26728 g();
26729 else
26730 f();
26731 </pre>
26732 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
26733 <pre>
26734 // calls g without raising ''invalid'' if a and b are unordered
26735 if (isless(a,b))
26736 f();
26737 else
26738 g();
26739 </pre>
26740 but is equivalent to
26741 <!--page 535 -->
26742 <pre>
26743 if (!(a < b))
26744 g();
26745 else
26746 f();
26747 </pre>
26753 The implementation shall honor floating-point exceptions raised by execution-time
26754 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.8.4">F.8.4</a>
26755 and <a href="#F.8.5">F.8.5</a>.) An operation on constants that raises no floating-point exception can be
26756 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
26757 further check is required to assure that changing the rounding direction to downward does
26758 not alter the sign of the result,<sup><a href="#note370"><b>370)</b></a></sup> and implementations that support dynamic rounding
26759 precision modes shall assure further that the result of the operation raises no floating-
26760 point exception when converted to the semantic type of the operation.
26763 <p><small><a name="note370" href="#note370">370)</a> 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
26764 </small>
26769 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
26770 for IEC 60559 implementations.
26772 The Standard C macro HUGE_VAL and its float and long double analogs,
26773 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
26774 infinities.
26776 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
26777 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
26778 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
26779 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
26780 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
26782 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
26783 nonzero value.
26785 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
26786 subsequent subclauses of this annex.
26788 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
26789 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
26790 whose magnitude is too large.
26792 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
26796 <!--page 536 -->
26798 Whether or when library functions raise the ''inexact'' floating-point exception is
26799 unspecified, unless explicitly specified otherwise.
26801 Whether or when library functions raise an undeserved ''underflow'' floating-point
26802 exception is unspecified.<sup><a href="#note372"><b>372)</b></a></sup> Otherwise, as implied by <a href="#F.8.6">F.8.6</a>, the <a href="#7.12"><math.h></a> functions do
26803 not raise spurious floating-point exceptions (detectable by the user), other than the
26804 ''inexact'' floating-point exception.
26806 Whether the functions honor the rounding direction mode is implementation-defined,
26807 unless explicitly specified otherwise.
26809 Functions with a NaN argument return a NaN result and raise no floating-point exception,
26810 except where stated otherwise.
26812 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
26813 For families of functions, the specifications apply to all of the functions even though only
26814 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
26815 occurs in both an argument and the result, the result has the same sign as the argument.
26818 If a function with one or more NaN arguments returns a NaN result, the result should be
26819 the same as one of the NaN arguments (after possible type conversion), except perhaps
26820 for the sign.
26823 <p><small><a name="note371" href="#note371">371)</a> IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
26824 when the floating-point exception is raised.
26825 </small>
26826 <p><small><a name="note372" href="#note372">372)</a> It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
26827 avoiding them would be too costly.
26828 </small>
26836 <ul>
26838 <li> acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
26840 </ul>
26845 <ul>
26847 <li> asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
26853 <!--page 537 -->
26854 </ul>
26859 <ul>
26862 </ul>
26867 <ul>
26879 </ul>
26882 <p><small><a name="note373" href="#note373">373)</a> atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
26883 the ''divide-by-zero'' floating-point exception.
26884 </small>
26889 <ul>
26891 <li> cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
26892 </ul>
26897 <ul>
26899 <li> sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
26900 </ul>
26905 <ul>
26907 <li> tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
26912 <!--page 538 -->
26913 </ul>
26921 <ul>
26924 <li> acosh(+(inf)) returns +(inf).
26925 </ul>
26930 <ul>
26932 <li> asinh((+-)(inf)) returns (+-)(inf).
26933 </ul>
26938 <ul>
26940 <li> atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
26941 <li> atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
26943 </ul>
26948 <ul>
26950 <li> cosh((+-)(inf)) returns +(inf).
26951 </ul>
26956 <ul>
26958 <li> sinh((+-)(inf)) returns (+-)(inf).
26959 </ul>
26964 <ul>
26967 </ul>
26975 <ul>
26978 <li> exp(+(inf)) returns +(inf).
26979 <!--page 539 -->
26980 </ul>
26985 <ul>
26988 <li> exp2(+(inf)) returns +(inf).
26989 </ul>
26994 <ul>
26997 <li> expm1(+(inf)) returns +(inf).
26998 </ul>
27003 <ul>
27005 <li> frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
27006 pointed to by exp.
27007 <li> frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
27008 (and returns a NaN).
27009 </ul>
27011 frexp raises no floating-point exceptions.
27013 When the radix of the argument is a power of 2, the returned value is exact and is
27014 independent of the current rounding direction mode.
27016 On a binary system, the body of the frexp function might be
27017 <pre>
27018 {
27020 return scalbn(value, -(*exp));
27021 }
27022 </pre>
27027 When the correct result is representable in the range of the return type, the returned value
27028 is exact and is independent of the current rounding direction mode.
27030 If the correct result is outside the range of the return type, the numeric result is
27031 unspecified and the ''invalid'' floating-point exception is raised.
27033 ilogb(x), for x zero, infinite, or NaN, raises the ''invalid'' floating-point exception and
27035 <!--page 540 -->
27040 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
27045 <ul>
27049 <li> log(+(inf)) returns +(inf).
27050 </ul>
27055 <ul>
27059 <li> log10(+(inf)) returns +(inf).
27060 </ul>
27065 <ul>
27068 <li> log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
27070 <li> log1p(+(inf)) returns +(inf).
27071 </ul>
27076 <ul>
27080 <li> log2(+(inf)) returns +(inf).
27081 </ul>
27086 <ul>
27088 <li> logb((+-)(inf)) returns +(inf).
27089 </ul>
27091 The returned value is exact and is independent of the current rounding direction mode.
27092 <!--page 541 -->
27097 <ul>
27098 <li> modf((+-)x, iptr) returns a result with the same sign as x.
27099 <li> modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
27100 <li> modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
27101 NaN).
27102 </ul>
27104 The returned values are exact and are independent of the current rounding direction
27105 mode.
27107 modf behaves as though implemented by
27108 <pre>
27111 #pragma STDC FENV_ACCESS ON
27112 double modf(double value, double *iptr)
27113 {
27114 int save_round = fegetround();
27115 fesetround(FE_TOWARDZERO);
27116 *iptr = nearbyint(value);
27117 fesetround(save_round);
27118 return copysign(
27119 isinf(value) ? 0.0 :
27120 value - (*iptr), value);
27121 }
27122 </pre>
27127 <ul>
27130 <li> scalbn((+-)(inf), n) returns (+-)(inf).
27131 </ul>
27133 If the calculation does not overflow or underflow, the returned value is exact and
27134 independent of the current rounding direction mode.
27135 <!--page 542 -->
27143 <ul>
27145 <li> cbrt((+-)(inf)) returns (+-)(inf).
27146 </ul>
27151 <ul>
27153 <li> fabs((+-)(inf)) returns +(inf).
27154 </ul>
27156 The returned value is exact and is independent of the current rounding direction mode.
27161 <ul>
27162 <li> hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
27164 <li> hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
27165 </ul>
27170 <ul>
27171 <li> pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
27176 exception.
27182 <li> pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
27188 <!--page 543 -->
27195 </ul>
27200 sqrt is fully specified as a basic arithmetic operation in IEC 60559. The returned value
27201 is dependent on the current rounding direction mode.
27209 <ul>
27212 </ul>
27217 <ul>
27220 </ul>
27225 <ul>
27228 <li> lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
27229 x a negative integer or zero.
27230 <li> lgamma(-(inf)) returns +(inf).
27231 <li> lgamma(+(inf)) returns +(inf).
27232 </ul>
27237 <ul>
27238 <li> tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
27239 <li> tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
27240 negative integer.
27241 <li> tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
27242 <li> tgamma(+(inf)) returns +(inf).
27243 <!--page 544 -->
27244 </ul>
27252 <ul>
27254 <li> ceil((+-)(inf)) returns (+-)(inf).
27255 </ul>
27257 The returned value is independent of the current rounding direction mode.
27259 The double version of ceil behaves as though implemented by
27260 <pre>
27263 #pragma STDC FENV_ACCESS ON
27264 double ceil(double x)
27265 {
27266 double result;
27267 int save_round = fegetround();
27268 fesetround(FE_UPWARD);
27269 result = rint(x); // or nearbyint instead of rint
27270 fesetround(save_round);
27271 return result;
27272 }
27273 </pre>
27275 The ceil functions may, but are not required to, raise the ''inexact'' floating-point
27276 exception for finite non-integer arguments, as this implementation does.
27281 <ul>
27283 <li> floor((+-)(inf)) returns (+-)(inf).
27284 </ul>
27286 The returned value and is independent of the current rounding direction mode.
27288 See the sample implementation for ceil in <a href="#F.10.6.1">F.10.6.1</a>. The floor functions may, but are
27289 not required to, raise the ''inexact'' floating-point exception for finite non-integer
27290 arguments, as that implementation does.
27295 The nearbyint functions use IEC 60559 rounding according to the current rounding
27296 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
27297 value from the argument.
27298 <ul>
27300 <li> nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
27301 <!--page 545 -->
27302 </ul>
27307 The rint functions differ from the nearbyint functions only in that they do raise the
27308 ''inexact'' floating-point exception if the result differs in value from the argument.
27313 The lrint and llrint functions provide floating-to-integer conversion as prescribed
27314 by IEC 60559. They round according to the current rounding direction. If the rounded
27315 value is outside the range of the return type, the numeric result is unspecified and the
27316 ''invalid'' floating-point exception is raised. When they raise no other floating-point
27317 exception and the result differs from the argument, they raise the ''inexact'' floating-point
27318 exception.
27323 <ul>
27325 <li> round((+-)(inf)) returns (+-)(inf).
27326 </ul>
27328 The returned value is independent of the current rounding direction mode.
27330 The double version of round behaves as though implemented by
27331 <pre>
27334 #pragma STDC FENV_ACCESS ON
27335 double round(double x)
27336 {
27337 double result;
27338 fenv_t save_env;
27339 feholdexcept(&save_env);
27340 result = rint(x);
27341 if (fetestexcept(FE_INEXACT)) {
27342 fesetround(FE_TOWARDZERO);
27343 result = rint(copysign(0.5 + fabs(x), x));
27344 }
27345 feupdateenv(&save_env);
27346 return result;
27347 }
27348 </pre>
27349 The round functions may, but are not required to, raise the ''inexact'' floating-point
27350 exception for finite non-integer numeric arguments, as this implementation does.
27351 <!--page 546 -->
27356 The lround and llround functions differ from the lrint and llrint functions
27357 with the default rounding direction just in that the lround and llround functions
27358 round halfway cases away from zero and need not raise the ''inexact'' floating-point
27359 exception for non-integer arguments that round to within the range of the return type.
27364 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
27365 rounding direction). The returned value is exact.
27366 <ul>
27368 <li> trunc((+-)(inf)) returns (+-)(inf).
27369 </ul>
27371 The returned value is independent of the current rounding direction mode. The trunc
27372 functions may, but are not required to, raise the ''inexact'' floating-point exception for
27373 finite non-integer arguments.
27381 <ul>
27383 <li> fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
27384 infinite or y zero (and neither is a NaN).
27385 <li> fmod(x, (+-)(inf)) returns x for x not infinite.
27386 </ul>
27388 When subnormal results are supported, the returned value is exact and is independent of
27389 the current rounding direction mode.
27391 The double version of fmod behaves as though implemented by
27392 <!--page 547 -->
27393 <pre>
27396 #pragma STDC FENV_ACCESS ON
27397 double fmod(double x, double y)
27398 {
27399 double result;
27400 result = remainder(fabs(x), (y = fabs(y)));
27401 if (signbit(result)) result += y;
27402 return copysign(result, x);
27403 }
27404 </pre>
27409 The remainder functions are fully specified as a basic arithmetic operation in
27410 IEC 60559.
27412 When subnormal results are supported, the returned value is exact and is independent of
27413 the current rounding direction mode.
27418 The remquo functions follow the specifications for the remainder functions. They
27419 have no further specifications special to IEC 60559 implementations.
27421 When subnormal results are supported, the returned value is exact and is independent of
27422 the current rounding direction mode.
27430 copysign is specified in the Appendix to IEC 60559.
27432 The returned value is exact and is independent of the current rounding direction mode.
27437 All IEC 60559 implementations support quiet NaNs, in all floating formats.
27439 The returned value is exact and is independent of the current rounding direction mode.
27444 <ul>
27445 <li> nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
27446 for x finite and the function value infinite.
27447 <li> nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
27448 exceptions for the function value subnormal or zero and x != y.
27449 </ul>
27451 Even though underflow or overflow can occur, the returned value is independent of the
27452 current rounding direction mode.
27457 No additional requirements beyond those on nextafter.
27459 Even though underflow or overflow can occur, the returned value is independent of the
27460 current rounding direction mode.
27461 <!--page 548 -->
27464 <h4><a name="F.10.9" href="#F.10.9">F.10.9 Maximum, minimum, and positive difference functions</a></h4>
27469 No additional requirements.
27474 If just one argument is a NaN, the fmax functions return the other argument (if both
27475 arguments are NaNs, the functions return a NaN).
27477 The returned value is exact and is independent of the current rounding direction mode.
27480 <pre>
27481 { return (isgreaterequal(x, y) ||
27482 isnan(y)) ? x : y; }
27483 </pre>
27486 <p><small><a name="note374" href="#note374">374)</a> Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
27487 return +0; however, implementation in software might be impractical.
27488 </small>
27493 The fmin functions are analogous to the fmax functions (see <a href="#F.10.9.2">F.10.9.2</a>).
27495 The returned value is exact and is independent of the current rounding direction mode.
27503 <ul>
27504 <li> fma(x, y, z) computes xy + z, correctly rounded once.
27505 <li> fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
27506 exception if one of x and y is infinite, the other is zero, and z is a NaN.
27507 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
27508 one of x and y is infinite, the other is zero, and z is not a NaN.
27509 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
27510 times y is an exact infinity and z is also an infinity but with the opposite sign.
27515 <!--page 549 -->
27516 </ul>
27521 Relational operators and their corresponding comparison macros (<a href="#7.12.14">7.12.14</a>) produce
27522 equivalent result values, even if argument values are represented in wider formats. Thus,
27523 comparison macro arguments represented in formats wider than their semantic types are
27524 not converted to the semantic types, unless the wide evaluation method converts operands
27525 of relational operators to their semantic types. The standard wide evaluation methods
27526 characterized by FLT_EVAL_METHOD equal to 1 or 2 (<a href="#5.2.4.2.2">5.2.4.2.2</a>), do not convert
27527 operands of relational operators to their semantic types.
27528 <!--page 550 -->
27532 <pre>
27533 (normative)
27534 IEC 60559-compatible complex arithmetic
27535 </pre>
27540 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
27541 IEC 60559 real floating-point arithmetic. An implementation that defines
27542 __STDC_IEC_559_COMPLEX__ shall conform to the specifications in this annex.<sup><a href="#note375"><b>375)</b></a></sup>
27545 <p><small><a name="note375" href="#note375">375)</a> Implementations that do not define __STDC_IEC_559_COMPLEX__ are not required to conform
27546 to these specifications.
27547 </small>
27552 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
27553 used as a type specifier within declaration specifiers in the same way as _Complex is
27554 (thus, _Imaginary float is a valid type name).
27556 There are three imaginary types, designated as float _Imaginary, double
27557 _Imaginary, and long double _Imaginary. The imaginary types (along with
27558 the real floating and complex types) are floating types.
27560 For imaginary types, the corresponding real type is given by deleting the keyword
27561 _Imaginary from the type name.
27563 Each imaginary type has the same representation and alignment requirements as the
27564 corresponding real type. The value of an object of imaginary type is the value of the real
27565 representation times the imaginary unit.
27567 The imaginary type domain comprises the imaginary types.
27572 A complex or imaginary value with at least one infinite part is regarded as an infinity
27573 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
27574 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
27575 a zero if each of its parts is a zero.
27580 <!--page 551 -->
27588 Conversions among imaginary types follow rules analogous to those for real floating
27589 types.
27594 When a value of imaginary type is converted to a real type other than _Bool,<sup><a href="#note376"><b>376)</b></a></sup> the
27595 result is a positive zero.
27597 When a value of real type is converted to an imaginary type, the result is a positive
27598 imaginary zero.
27602 </small>
27607 When a value of imaginary type is converted to a complex type, the real part of the
27608 complex result value is a positive zero and the imaginary part of the complex result value
27609 is determined by the conversion rules for the corresponding real types.
27611 When a value of complex type is converted to an imaginary type, the real part of the
27612 complex value is discarded and the value of the imaginary part is converted according to
27613 the conversion rules for the corresponding real types.
27618 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
27619 operation with an imaginary operand.
27621 For most operand types, the value of the result of a binary operator with an imaginary or
27622 complex operand is completely determined, with reference to real arithmetic, by the usual
27623 mathematical formula. For some operand types, the usual mathematical formula is
27624 problematic because of its treatment of infinities and because of undue overflow or
27625 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
27626 not completely determined.
27631 <!--page 552 -->
27637 If one operand has real type and the other operand has imaginary type, then the result has
27638 imaginary type. If both operands have imaginary type, then the result has real type. (If
27639 either operand has complex type, then the result has complex type.)
27641 If the operands are not both complex, then the result and floating-point exception
27642 behavior of the * operator is defined by the usual mathematical formula:
27643 <pre>
27644 * u iv u + iv
27645 </pre>
27647 <pre>
27648 x xu i(xv) (xu) + i(xv)
27649 </pre>
27651 <pre>
27652 iy i(yu) -yv (-yv) + i(yu)
27653 </pre>
27655 <pre>
27656 x + iy (xu) + i(yu) (-yv) + i(xv)
27657 </pre>
27659 If the second operand is not complex, then the result and floating-point exception
27660 behavior of the / operator is defined by the usual mathematical formula:
27661 <pre>
27662 / u iv
27663 </pre>
27665 <pre>
27666 x x/u i(-x/v)
27667 </pre>
27669 <pre>
27670 iy i(y/u) y/v
27671 </pre>
27673 <pre>
27674 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)
27675 </pre>
27677 The * and / operators satisfy the following infinity properties for all real, imaginary, and
27679 <ul>
27680 <li> if one operand is an infinity and the other operand is a nonzero finite number or an
27681 infinity, then the result of the * operator is an infinity;
27682 <li> if the first operand is an infinity and the second operand is a finite number, then the
27683 result of the / operator is an infinity;
27684 <li> if the first operand is a finite number and the second operand is an infinity, then the
27685 result of the / operator is a zero;
27690 <!--page 553 -->
27691 <li> if the first operand is a nonzero finite number or an infinity and the second operand is
27692 a zero, then the result of the / operator is an infinity.
27693 </ul>
27695 If both operands of the * operator are complex or if the second operand of the / operator
27696 is complex, the operator raises floating-point exceptions if appropriate for the calculation
27697 of the parts of the result, and may raise spurious floating-point exceptions.
27699 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
27701 <!--page 554 -->
27702 <pre>
27705 /* Multiply z * w ... */
27706 double complex _Cmultd(double complex z, double complex w)
27707 {
27708 #pragma STDC FP_CONTRACT OFF
27709 double a, b, c, d, ac, bd, ad, bc, x, y;
27710 a = creal(z); b = cimag(z);
27711 c = creal(w); d = cimag(w);
27712 ac = a * c; bd = b * d;
27713 ad = a * d; bc = b * c;
27714 x = ac - bd; y = ad + bc;
27715 if (isnan(x) && isnan(y)) {
27716 /* Recover infinities that computed as NaN+iNaN ... */
27717 int recalc = 0;
27718 if (isinf(a) || isinf(b)) { // z is infinite
27722 if (isnan(c)) c = copysign(0.0, c);
27723 if (isnan(d)) d = copysign(0.0, d);
27724 recalc = 1;
27725 }
27726 if (isinf(c) || isinf(d)) { // w is infinite
27730 if (isnan(a)) a = copysign(0.0, a);
27731 if (isnan(b)) b = copysign(0.0, b);
27732 recalc = 1;
27733 }
27734 if (!recalc && (isinf(ac) || isinf(bd) ||
27735 isinf(ad) || isinf(bc))) {
27736 /* Recover infinities from overflow by changing NaNs to 0 ... */
27737 if (isnan(a)) a = copysign(0.0, a);
27738 if (isnan(b)) b = copysign(0.0, b);
27739 if (isnan(c)) c = copysign(0.0, c);
27740 if (isnan(d)) d = copysign(0.0, d);
27741 recalc = 1;
27742 }
27743 if (recalc) {
27744 x = INFINITY * ( a * c - b * d );
27745 y = INFINITY * ( a * d + b * c );
27746 }
27747 }
27748 return x + I * y;
27749 }
27750 </pre>
27752 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
27753 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
27756 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
27757 <!--page 555 -->
27758 <pre>
27761 /* Divide z / w ... */
27762 double complex _Cdivd(double complex z, double complex w)
27763 {
27764 #pragma STDC FP_CONTRACT OFF
27765 double a, b, c, d, logbw, denom, x, y;
27766 int ilogbw = 0;
27767 a = creal(z); b = cimag(z);
27768 c = creal(w); d = cimag(w);
27769 logbw = logb(fmax(fabs(c), fabs(d)));
27770 if (isfinite(logbw)) {
27771 ilogbw = (int)logbw;
27772 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
27773 }
27774 denom = c * c + d * d;
27775 x = scalbn((a * c + b * d) / denom, -ilogbw);
27776 y = scalbn((b * c - a * d) / denom, -ilogbw);
27777 /* Recover infinities and zeros that computed as NaN+iNaN; */
27778 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
27779 if (isnan(x) && isnan(y)) {
27781 (!isnan(a) || !isnan(b))) {
27782 x = copysign(INFINITY, c) * a;
27783 y = copysign(INFINITY, c) * b;
27784 }
27785 else if ((isinf(a) || isinf(b)) &&
27786 isfinite(c) && isfinite(d)) {
27789 x = INFINITY * ( a * c + b * d );
27790 y = INFINITY * ( b * c - a * d );
27791 }
27792 else if ((logbw == INFINITY) &&
27793 isfinite(a) && isfinite(b)) {
27796 x = 0.0 * ( a * c + b * d );
27797 y = 0.0 * ( b * c - a * d );
27798 }
27799 }
27800 return x + I * y;
27801 }
27802 </pre>
27804 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
27805 for multiplication. In the spirit of the multiplication example above, this code does not defend against
27806 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
27807 with division, provides better roundoff characteristics.
27811 <p><small><a name="note377" href="#note377">377)</a> These properties are already implied for those cases covered in the tables, but are required for all cases
27812 (at least where the state for CX_LIMITED_RANGE is ''off'').
27813 </small>
27819 If both operands have imaginary type, then the result has imaginary type. (If one operand
27820 has real type and the other operand has imaginary type, or if either operand has complex
27821 type, then the result has complex type.)
27823 In all cases the result and floating-point exception behavior of a + or - operator is defined
27824 by the usual mathematical formula:
27825 <pre>
27826 + or - u iv u + iv
27827 </pre>
27829 <pre>
27830 x x(+-)u x (+-) iv (x (+-) u) (+-) iv
27831 </pre>
27833 <pre>
27834 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)
27835 </pre>
27837 <pre>
27838 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)
27839 </pre>
27844 The macros
27845 <pre>
27846 imaginary
27847 </pre>
27848 and
27849 <pre>
27850 _Imaginary_I
27851 </pre>
27852 are defined, respectively, as _Imaginary and a constant expression of type const
27853 float _Imaginary with the value of the imaginary unit. The macro
27854 <pre>
27855 I
27856 </pre>
27857 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
27858 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
27859 imaginary.
27861 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
27862 particularly suited to IEC 60559 implementations. For families of functions, the
27863 specifications apply to all of the functions even though only the principal function is
27864 <!--page 556 -->
27865 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
27866 and the result, the result has the same sign as the argument.
27868 The functions are continuous onto both sides of their branch cuts, taking into account the
27871 Since complex and imaginary values are composed of real values, each function may be
27872 regarded as computing real values from real values. Except as noted, the functions treat
27873 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
27874 manner consistent with the specifications for real functions in F.10.<sup><a href="#note378"><b>378)</b></a></sup>
27876 The functions cimag, conj, cproj, and creal are fully specified for all
27877 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
27878 point exceptions.
27880 Each of the functions cabs and carg is specified by a formula in terms of a real
27882 <pre>
27883 cabs(x + iy) = hypot(x, y)
27884 carg(x + iy) = atan2(y, x)
27885 </pre>
27887 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
27888 a formula in terms of other complex functions (whose special cases are specified below):
27889 <pre>
27890 casin(z) = -i casinh(iz)
27891 catan(z) = -i catanh(iz)
27892 ccos(z) = ccosh(iz)
27893 csin(z) = -i csinh(iz)
27894 ctan(z) = -i ctanh(iz)
27895 </pre>
27897 For the other functions, the following subclauses specify behavior for special cases,
27898 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
27899 families of functions, the specifications apply to all of the functions even though only the
27900 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
27901 specifications for the upper half-plane imply the specifications for the lower half-plane; if
27902 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
27903 specifications for the first quadrant imply the specifications for the other three quadrants.
27905 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
27910 <!--page 557 -->
27913 <p><small><a name="note378" href="#note378">378)</a> As noted in <a href="#G.3">G.3</a>, a complex value with at least one infinite part is regarded as an infinity even if its
27914 other part is a NaN.
27915 </small>
27923 <ul>
27924 <li> cacos(conj(z)) = conj(cacos(z)).
27928 <li> cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27929 point exception, for nonzero finite x.
27930 <li> cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
27934 <li> cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
27935 result is unspecified).
27936 <li> cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27937 point exception, for finite y.
27938 <li> cacos(NaN + i (inf)) returns NaN - i (inf).
27939 <li> cacos(NaN + iNaN) returns NaN + iNaN.
27940 </ul>
27948 <ul>
27949 <li> cacosh(conj(z)) = conj(cacosh(z)).
27952 <li> cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
27953 floating-point exception, for finite x.
27954 <li> cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
27955 <li> cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
27958 <li> cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
27959 <!--page 558 -->
27960 <li> cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
27961 floating-point exception, for finite y.
27962 <li> cacosh(NaN + i (inf)) returns +(inf) + iNaN.
27963 <li> cacosh(NaN + iNaN) returns NaN + iNaN.
27964 </ul>
27969 <ul>
27970 <li> casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
27973 <li> casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
27974 floating-point exception, for finite x.
27975 <li> casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
27977 <li> casinh(+(inf) + iNaN) returns +(inf) + iNaN.
27978 <li> casinh(NaN + i0) returns NaN + i0.
27979 <li> casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
27980 floating-point exception, for finite nonzero y.
27981 <li> casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
27982 is unspecified).
27983 <li> casinh(NaN + iNaN) returns NaN + iNaN.
27984 </ul>
27989 <ul>
27990 <li> catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
27994 exception.
27996 <li> catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
27997 floating-point exception, for nonzero finite x.
28001 <!--page 559 -->
28002 <li> catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
28003 floating-point exception, for finite y.
28004 <li> catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
28005 unspecified).
28006 <li> catanh(NaN + iNaN) returns NaN + iNaN.
28007 </ul>
28012 <ul>
28013 <li> ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
28016 result is unspecified) and raises the ''invalid'' floating-point exception.
28018 result is unspecified).
28019 <li> ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
28020 exception, for finite nonzero x.
28021 <li> ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28022 point exception, for finite nonzero x.
28023 <li> ccosh(+(inf) + i0) returns +(inf) + i0.
28024 <li> ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
28025 <li> ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
28026 unspecified) and raises the ''invalid'' floating-point exception.
28027 <li> ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
28028 <li> ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
28029 result is unspecified).
28030 <li> ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28031 point exception, for all nonzero numbers y.
28032 <li> ccosh(NaN + iNaN) returns NaN + iNaN.
28033 </ul>
28038 <ul>
28039 <li> csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
28041 <li> csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
28042 unspecified) and raises the ''invalid'' floating-point exception.
28044 unspecified).
28045 <!--page 560 -->
28046 <li> csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
28047 exception, for positive finite x.
28048 <li> csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28049 point exception, for finite nonzero x.
28050 <li> csinh(+(inf) + i0) returns +(inf) + i0.
28051 <li> csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
28052 <li> csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
28053 unspecified) and raises the ''invalid'' floating-point exception.
28054 <li> csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
28055 is unspecified).
28056 <li> csinh(NaN + i0) returns NaN + i0.
28057 <li> csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28058 point exception, for all nonzero numbers y.
28059 <li> csinh(NaN + iNaN) returns NaN + iNaN.
28060 </ul>
28065 <ul>
28066 <li> ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
28068 <li> ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
28069 exception, for finite x.
28070 <li> ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28071 point exception, for finite x.
28073 <li> ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
28074 is unspecified).
28076 result is unspecified).
28077 <li> ctanh(NaN + i0) returns NaN + i0.
28078 <li> ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28079 point exception, for all nonzero numbers y.
28080 <li> ctanh(NaN + iNaN) returns NaN + iNaN.
28081 <!--page 561 -->
28082 </ul>
28090 <ul>
28091 <li> cexp(conj(z)) = conj(cexp(z)).
28093 <li> cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
28094 exception, for finite x.
28095 <li> cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28096 point exception, for finite x.
28097 <li> cexp(+(inf) + i0) returns +(inf) + i0.
28099 <li> cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
28100 <li> cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
28101 the result are unspecified).
28102 <li> cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
28103 exception (where the sign of the real part of the result is unspecified).
28104 <li> cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
28105 of the result are unspecified).
28106 <li> cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
28107 is unspecified).
28108 <li> cexp(NaN + i0) returns NaN + i0.
28109 <li> cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28110 point exception, for all nonzero numbers y.
28111 <li> cexp(NaN + iNaN) returns NaN + iNaN.
28112 </ul>
28117 <ul>
28118 <li> clog(conj(z)) = conj(clog(z)).
28120 exception.
28122 exception.
28124 <li> clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28125 point exception, for finite x.
28126 <!--page 562 -->
28127 <li> clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
28128 <li> clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
28131 <li> clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
28132 <li> clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28133 point exception, for finite y.
28134 <li> clog(NaN + i (inf)) returns +(inf) + iNaN.
28135 <li> clog(NaN + iNaN) returns NaN + iNaN.
28136 </ul>
28144 The cpow functions raise floating-point exceptions if appropriate for the calculation of
28145 the parts of the result, and may also raise spurious floating-point exceptions.<sup><a href="#note379"><b>379)</b></a></sup>
28148 <p><small><a name="note379" href="#note379">379)</a> This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
28149 implementations that treat special cases more carefully.
28150 </small>
28155 <ul>
28156 <li> csqrt(conj(z)) = conj(csqrt(z)).
28158 <li> csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
28159 <li> csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28160 point exception, for finite x.
28162 <li> csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
28163 <li> csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
28164 result is unspecified).
28165 <li> csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
28166 <li> csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
28167 point exception, for finite y.
28168 <li> csqrt(NaN + iNaN) returns NaN + iNaN.
28173 <!--page 563 -->
28174 </ul>
28179 Type-generic macros that accept complex arguments also accept imaginary arguments. If
28180 an argument is imaginary, the macro expands to an expression whose type is real,
28181 imaginary, or complex, as appropriate for the particular function: if the argument is
28182 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
28183 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
28184 the types of the others are complex.
28186 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
28187 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
28188 functions:
28189 <!--page 564 -->
28190 <pre>
28191 cos(iy) = cosh(y)
28192 sin(iy) = i sinh(y)
28193 tan(iy) = i tanh(y)
28194 cosh(iy) = cos(y)
28195 sinh(iy) = i sin(y)
28196 tanh(iy) = i tan(y)
28197 asin(iy) = i asinh(y)
28198 atan(iy) = i atanh(y)
28199 asinh(iy) = i asin(y)
28200 atanh(iy) = i atan(y)
28201 </pre>
28205 <pre>
28206 (informative)
28207 Language independent arithmetic
28208 </pre>
28215 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
28220 The relevant C arithmetic types meet the requirements of LIA-1 types if an
28221 implementation adds notification of exceptional arithmetic operations and meets the 1
28222 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
28227 The LIA-1 data type Boolean is implemented by the C data type bool with values of
28233 The signed C integer types int, long int, long long int, and the corresponding
28234 unsigned types are compatible with LIA-1. If an implementation adds support for the
28235 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
28237 in that overflows or out-of-bounds results silently wrap. An implementation that defines
28238 signed integer types as also being modulo need not detect integer overflow, in which case,
28239 only integer divide-by-zero need be detected.
28241 The parameters for the integer data types can be accessed by the following:
28242 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
28243 <pre>
28244 ULLONG_MAX
28245 </pre>
28246 minint INT_MIN, LONG_MIN, LLONG_MIN
28248 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
28249 is always 0 for the unsigned types, and is not provided for those types.
28250 <!--page 565 -->
28255 The integer operations on integer types are the following:
28256 addI x + y
28257 subI x - y
28258 mulI x * y
28259 divI, divtI x / y
28260 remI, remtI x % y
28261 negI -x
28262 absI abs(x), labs(x), llabs(x)
28263 eqI x == y
28264 neqI x != y
28265 lssI x < y
28266 leqI x <= y
28267 gtrI x > y
28268 geqI x >= y
28269 where x and y are expressions of the same integer type.
28274 The C floating-point types float, double, and long double are compatible with
28276 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
28277 with LIA-1. An implementation that uses IEC 60559 floating-point formats and
28278 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
28279 conformant types.
28283 <p><!--para 1 -->
28284 The parameters for a floating point data type can be accessed by the following:
28285 r FLT_RADIX
28286 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
28287 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
28288 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
28289 <p><!--para 2 -->
28290 The derived constants for the floating point types are accessed by the following:
28291 <!--page 566 -->
28292 fmax FLT_MAX, DBL_MAX, LDBL_MAX
28293 fminN FLT_MIN, DBL_MIN, LDBL_MIN
28294 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
28295 rnd_style FLT_ROUNDS
28299 <p><!--para 1 -->
28300 The floating-point operations on floating-point types are the following:
28301 addF x + y
28302 subF x - y
28303 mulF x * y
28304 divF x / y
28305 negF -x
28306 absF fabsf(x), fabs(x), fabsl(x)
28307 exponentF 1.f+logbf(x), 1.0+logb(x), 1.L+logbl(x)
28308 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
28309 <pre>
28310 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)
28311 </pre>
28312 intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
28313 fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
28314 eqF x == y
28315 neqF x != y
28316 lssF x < y
28317 leqF x <= y
28318 gtrF x > y
28319 geqF x >= y
28320 where x and y are expressions of the same floating point type, n is of type int, and li
28321 is of type long int.
28325 <p><!--para 1 -->
28326 The C Standard requires all floating types to use the same radix and rounding style, so
28327 that only one identifier for each is provided to map to LIA-1.
28328 <p><!--para 2 -->
28329 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
28330 truncate FLT_ROUNDS == 0
28331 <!--page 567 -->
28332 nearest FLT_ROUNDS == 1
28333 other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
28334 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
28335 in all relevant LIA-1 operations, not just addition as in C.
28339 <p><!--para 1 -->
28340 The LIA-1 type conversions are the following type casts:
28341 cvtI' -> I (int)i, (long int)i, (long long int)i,
28342 <pre>
28343 (unsigned int)i, (unsigned long int)i,
28344 (unsigned long long int)i
28345 </pre>
28346 cvtF -> I (int)x, (long int)x, (long long int)x,
28347 <pre>
28348 (unsigned int)x, (unsigned long int)x,
28349 (unsigned long long int)x
28350 </pre>
28351 cvtI -> F (float)i, (double)i, (long double)i
28352 cvtF' -> F (float)x, (double)x, (long double)x
28353 <p><!--para 2 -->
28354 In the above conversions from floating to integer, the use of (cast)x can be replaced with
28355 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
28356 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
28357 conversion functions, lrint(), llrint(), lround(), and llround(), can be
28358 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
28359 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
28360 <p><!--para 3 -->
28361 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
28362 fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
28363 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
28364 to 65535.0 which can then be cast to unsigned short int. But, the
28365 remainder() function is not useful for doing silent wrapping to signed integer types,
28366 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
28367 range -32767.0 to +32768.0 which is not, in general, in the range of signed short
28368 int.
28369 <p><!--para 4 -->
28370 C's conversions (casts) from floating-point to floating-point can meet LIA-1
28371 requirements if an implementation uses round-to-nearest (IEC 60559 default).
28372 <p><!--para 5 -->
28373 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
28374 implementation uses round-to-nearest.
28375 <!--page 568 -->
28379 <p><!--para 1 -->
28380 Notification is the process by which a user or program is informed that an exceptional
28381 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
28382 allows an implementation to cause a notification to occur when any arithmetic operation
28383 returns an exceptional value as defined in LIA-1 clause 5.
28387 <p><!--para 1 -->
28388 LIA-1 requires at least the following two alternatives for handling of notifications:
28389 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
28390 resume.
28391 <p><!--para 2 -->
28392 An implementation need only support a given notification alternative for the entire
28393 program. An implementation may support the ability to switch between notification
28394 alternatives during execution, but is not required to do so. An implementation can
28395 provide separate selection for each kind of notification, but this is not required.
28396 <p><!--para 3 -->
28397 C allows an implementation to provide notification. C's SIGFPE (for traps) and
28398 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
28399 can provide LIA-1 notification.
28400 <p><!--para 4 -->
28401 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
28402 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
28403 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
28404 and-resume behavior with the same constraint.
28408 <p><!--para 1 -->
28410 <p><!--para 2 -->
28411 The following mapping is for floating-point types:
28412 undefined FE_INVALID, FE_DIVBYZERO
28413 floating_overflow FE_OVERFLOW
28414 underflow FE_UNDERFLOW
28415 <p><!--para 3 -->
28416 The floating-point indicator interrogation and manipulation operations are:
28417 set_indicators feraiseexcept(i)
28418 clear_indicators feclearexcept(i)
28419 test_indicators fetestexcept(i)
28420 current_indicators fetestexcept(FE_ALL_EXCEPT)
28421 where i is an expression of type int representing a subset of the LIA-1 indicators.
28422 <p><!--para 4 -->
28423 C allows an implementation to provide the following LIA-1 required behavior: at
28424 program termination if any indicator is set the implementation shall send an unambiguous
28425 <!--page 569 -->
28427 <p><!--para 5 -->
28428 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
28429 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
28430 point indicators.
28434 <p><!--para 1 -->
28435 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
28436 math library functions (which are not permitted to invoke a user's signal handler for
28437 SIGFPE). An implementation can provide an alternative of notification through
28438 termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
28439 <p><!--para 2 -->
28440 LIA-1 does not require that traps be precise.
28441 <p><!--para 3 -->
28442 C does require that SIGFPE be the signal corresponding to LIA-1 arithmetic exceptions,
28443 if there is any signal raised for them.
28444 <p><!--para 4 -->
28445 C supports signal handlers for SIGFPE and allows trapping of LIA-1 arithmetic
28446 exceptions. When LIA-1 arithmetic exceptions do trap, C's signal-handler mechanism
28447 allows trap-and-terminate (either default implementation behavior or user replacement for
28448 it) or trap-and-resume, at the programmer's option.
28449 <!--page 570 -->
28453 <pre>
28454 (informative)
28455 Common warnings
28456 </pre>
28457 <p><!--para 1 -->
28458 An implementation may generate warnings in many situations, none of which are
28459 specified as part of this International Standard. The following are a few of the more
28460 common situations.
28461 <p><!--para 2 -->
28462 <ul>
28463 <li> A new struct or union type appears in a function prototype (<a href="#6.2.1">6.2.1</a>, <a href="#6.7.2.3">6.7.2.3</a>).
28464 <li> A block with initialization of an object that has automatic storage duration is jumped
28466 <li> An implicit narrowing conversion is encountered, such as the assignment of a long
28467 int or a double to an int, or a pointer to void to a pointer to any type other than
28469 <li> A hexadecimal floating constant cannot be represented exactly in its evaluation format
28471 <li> An integer character constant includes more than one character or a wide character
28474 <li> An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
28475 lvalue in one operand, and a side effect to, or an access to the value of, the identical
28477 <li> A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
28478 <li> The arguments in a function call do not agree in number and type with those of the
28481 <li> A value is given to an object of an enumerated type other than by assignment of an
28482 enumeration constant that is a member of that type, or an enumeration object that has
28483 the same type, or the value of a function that returns the same enumerated type
28488 <li> A constant expression is used as the controlling expression of a selection statement
28490 <!--page 571 -->
28491 <li> An incorrectly formed preprocessing group is encountered while skipping a
28494 <!--page 572 -->
28495 </ul>
28499 <pre>
28500 (informative)
28501 Portability issues
28502 </pre>
28503 <p><!--para 1 -->
28504 This annex collects some information about portability that appears in this International
28505 Standard.
28509 <p><!--para 1 -->
28510 The following are unspecified:
28511 <ul>
28513 <li> The termination status returned to the hosted environment if the return type of main
28515 <li> The values of objects that are neither lock-free atomic objects nor of type volatile
28516 sig_atomic_t and the state of the floating-point environment, when the
28517 processing of the abstract machine is interrupted by receipt of a signal (<a href="#5.1.2.3">5.1.2.3</a>).
28518 <li> The behavior of the display device if a printing character is written when the active
28520 <li> The behavior of the display device if a backspace character is written when the active
28522 <li> The behavior of the display device if a horizontal tab character is written when the
28523 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
28524 <li> The behavior of the display device if a vertical tab character is written when the active
28525 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
28526 <li> How an extended source character that does not correspond to a universal character
28527 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
28529 <li> The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
28530 <li> The values of bytes that correspond to union members other than the one last stored
28532 <li> The representation used when storing a value in an object that has more than one
28534 <li> The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
28535 <li> Whether certain operators can generate negative zeros and whether a negative zero
28537 <!--page 573 -->
28539 <li> The order in which subexpressions are evaluated and the order in which side effects
28540 take place, except as specified for the function-call (), &&, ||, ? :, and comma
28542 <li> The order in which the function designator, arguments, and subexpressions within the
28544 <li> The order of side effects among compound literal initialization list expressions
28546 <li> The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
28547 <li> The alignment of the addressable storage unit allocated to hold a bit-field (<a href="#6.7.2.1">6.7.2.1</a>).
28548 <li> Whether a call to an inline function uses the inline definition or the external definition
28550 <li> Whether or not a size expression is evaluated when it is part of the operand of a
28551 sizeof operator and changing the value of the size expression would not affect the
28553 <li> The order in which any side effects occur among the initialization list expressions in
28556 <li> When a fully expanded macro replacement list contains a function-like macro name
28557 as its last preprocessing token and the next preprocessing token from the source file is
28558 a (, and the fully expanded replacement of that macro ends with the name of the first
28559 macro and the next preprocessing token from the source file is again a (, whether that
28561 <li> The order in which # and ## operations are evaluated during macro substitution
28563 <li> The state of the floating-point status flags when execution passes from a part of the
28564 program translated with FENV_ACCESS ''off'' to a part translated with
28566 <li> The order in which feraiseexcept raises floating-point exceptions, except as
28568 <li> Whether math_errhandling is a macro or an identifier with external linkage
28570 <li> The results of the frexp functions when the specified value is not a floating-point
28572 <!--page 574 -->
28573 <li> The numeric result of the ilogb functions when the correct value is outside the
28574 range of the return type (<a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.10.3.5">F.10.3.5</a>).
28575 <li> The result of rounding when the value is out of range (<a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.10.6.5">F.10.6.5</a>).
28576 <li> The value stored by the remquo functions in the object pointed to by quo when y is
28578 <li> Whether a comparison macro argument that is represented in a format wider than its
28580 <li> Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
28581 <li> Whether va_copy and va_end are macros or identifiers with external linkage
28583 <li> The hexadecimal digit before the decimal point when a non-normalized floating-point
28584 number is printed with an a or A conversion specifier (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
28585 <li> The value of the file position indicator after a successful call to the ungetc function
28586 for a text stream, or the ungetwc function for any stream, until all pushed-back
28587 characters are read or discarded (<a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.29.3.10">7.29.3.10</a>).
28588 <li> The details of the value stored by the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>).
28589 <li> The details of the value returned by the ftell function for a text stream (<a href="#7.21.9.4">7.21.9.4</a>).
28590 <li> Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
28591 functions convert a minus-signed sequence to a negative number directly or by
28592 negating the value resulting from converting the corresponding unsigned sequence
28594 <li> The order and contiguity of storage allocated by successive calls to the calloc,
28596 <li> The amount of storage allocated by a successful call to the calloc, malloc, or
28598 <li> Whether a call to the atexit function that does not happen before the exit
28600 <li> Whether a call to the at_quick_exit function that does not happen before the
28602 <li> Which of two elements that compare as equal is matched by the bsearch function
28604 <li> The order of two elements that compare as equal in an array sorted by the qsort
28606 <!--page 575 -->
28607 <li> The encoding of the calendar time returned by the time function (<a href="#7.27.2.4">7.27.2.4</a>).
28608 <li> The characters stored by the strftime or wcsftime function if any of the time
28609 values being converted is outside the normal range (<a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.5.1">7.29.5.1</a>).
28610 <li> Whether an encoding error occurs if a wchar_t value that does not correspond to a
28611 member of the extended character set appears in the format string for a function in
28612 <a href="#7.29.2">7.29.2</a> or <a href="#7.29.5">7.29.5</a> and the specified semantics do not require that value to be processed
28614 <li> The conversion state after an encoding error occurs (<a href="#7.29.6.3.2">7.29.6.3.2</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>, <a href="#7.29.6.4.1">7.29.6.4.1</a>,
28616 <li> The resulting value when the ''invalid'' floating-point exception is raised during
28618 <li> Whether conversion of non-integer IEC 60559 floating values to integer raises the
28620 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
28622 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
28623 floating-point exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
28624 <li> The exponent value stored by frexp for a NaN or infinity (<a href="#F.10.3.4">F.10.3.4</a>).
28625 <li> The numeric result returned by the lrint, llrint, lround, and llround
28626 functions if the rounded value is outside the range of the return type (<a href="#F.10.6.5">F.10.6.5</a>,
28628 <li> The sign of one part of the complex result of several math functions for certain
28629 special cases in IEC 60559 compatible implementations (<a href="#G.6.1.1">G.6.1.1</a>, <a href="#G.6.2.2">G.6.2.2</a>, <a href="#G.6.2.3">G.6.2.3</a>,
28630 <a href="#G.6.2.4">G.6.2.4</a>, <a href="#G.6.2.5">G.6.2.5</a>, <a href="#G.6.2.6">G.6.2.6</a>, <a href="#G.6.3.1">G.6.3.1</a>, <a href="#G.6.4.2">G.6.4.2</a>).
28631 </ul>
28635 <p><!--para 1 -->
28636 The behavior is undefined in the following circumstances:
28637 <ul>
28638 <li> A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
28639 (clause 4).
28640 <li> A nonempty source file does not end in a new-line character which is not immediately
28641 preceded by a backslash character or ends in a partial preprocessing token or
28643 <li> Token concatenation produces a character sequence matching the syntax of a
28645 <li> A program in a hosted environment does not define a function named main using one
28647 <!--page 576 -->
28649 <li> A character not in the basic source character set is encountered in a source file, except
28650 in an identifier, a character constant, a string literal, a header name, a comment, or a
28652 <li> An identifier, comment, string literal, character constant, or header name contains an
28653 invalid multibyte character or does not begin and end in the initial shift state (<a href="#5.2.1.2">5.2.1.2</a>).
28654 <li> The same identifier has both internal and external linkage in the same translation unit
28657 <li> The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
28658 <li> The value of an object with automatic storage duration is used while it is
28659 indeterminate (<a href="#6.2.4">6.2.4</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.8">6.8</a>).
28660 <li> A trap representation is read by an lvalue expression that does not have character type
28662 <li> A trap representation is produced by a side effect that modifies any part of the object
28663 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
28664 <li> The operands to certain operators are such that they could produce a negative zero
28665 result, but the implementation does not support negative zeros (<a href="#6.2.6.2">6.2.6.2</a>).
28666 <li> Two declarations of the same object or function specify types that are not compatible
28668 <li> A program requires the formation of a composite type from a variable length array
28669 type whose size is specified by an expression that is not evaluated (<a href="#6.2.7">6.2.7</a>).
28670 <li> Conversion to or from an integer type produces a value outside the range that can be
28672 <li> Demotion of one real floating type to another produces a value outside the range that
28675 <li> A non-array lvalue with an incomplete type is used in a context that requires the value
28677 <li> An lvalue designating an object of automatic storage duration that could have been
28678 declared with the register storage class is used in a context that requires the value
28680 <li> An lvalue having array type is converted to a pointer to the initial element of the
28682 <!--page 577 -->
28683 <li> An attempt is made to use the value of a void expression, or an implicit or explicit
28685 <li> Conversion of a pointer to an integer type produces a value outside the range that can
28687 <li> Conversion between two pointer types produces a result that is incorrectly aligned
28689 <li> A pointer is used to call a function whose type is not compatible with the referenced
28691 <li> An unmatched ' or " character is encountered on a logical source line during
28695 <li> A universal character name in an identifier does not designate a character whose
28697 <li> The initial character of an identifier is a universal character name designating a digit
28699 <li> Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
28703 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
28705 <li> A side effect on a scalar object is unsequenced relative to either a different side effect
28706 on the same scalar object or a value computation using the value of the same scalar
28708 <li> An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
28709 <li> An object has its stored value accessed other than by an lvalue of an allowable type
28711 <li> For a call to a function without a function prototype in scope, the number of
28713 <li> For call to a function without a function prototype in scope where the function is
28714 defined with a function prototype, either the prototype ends with an ellipsis or the
28715 types of the arguments after promotion are not compatible with the types of the
28717 <!--page 578 -->
28718 <li> For a call to a function without a function prototype in scope where the function is not
28719 defined with a function prototype, the types of the arguments after promotion are not
28720 compatible with those of the parameters after promotion (with certain exceptions)
28722 <li> A function is defined with a type that is not compatible with the type (of the
28723 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
28725 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
28726 <li> A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
28727 <li> The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
28728 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
28729 integer type produces a result that does not point into, or just beyond, the same array
28731 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
28732 integer type produces a result that points just beyond the array object and is used as
28734 <li> Pointers that do not point into, or just beyond, the same array object are subtracted
28736 <li> An array subscript is out of range, even if an object is apparently accessible with the
28739 <li> The result of subtracting two pointers is not representable in an object of type
28741 <li> An expression is shifted by a negative number or by an amount greater than or equal
28743 <li> An expression having signed promoted type is left-shifted and either the value of the
28744 expression is negative or the result of shifting would be not be representable in the
28746 <li> Pointers that do not point to the same aggregate or union (nor just beyond the same
28748 <li> An object is assigned to an inexactly overlapping object or to an exactly overlapping
28750 <li> An expression that is required to be an integer constant expression does not have an
28751 integer type; has operands that are not integer constants, enumeration constants,
28752 character constants, sizeof expressions whose results are integer constants,
28753 <!--page 579 -->
28754 _Alignof expressions, or immediately-cast floating constants; or contains casts
28755 (outside operands to sizeof and _Alignof operators) other than conversions of
28757 <li> A constant expression in an initializer is not, or does not evaluate to, one of the
28758 following: an arithmetic constant expression, a null pointer constant, an address
28759 constant, or an address constant for a complete object type plus or minus an integer
28761 <li> An arithmetic constant expression does not have arithmetic type; has operands that
28762 are not integer constants, floating constants, enumeration constants, character
28763 constants, sizeof expressions whose results are integer constants, or _Alignof
28764 expressions; or contains casts (outside operands to sizeof or _Alignof operators)
28767 address &, or indirection * operator or a pointer cast in creating an address constant
28769 <li> An identifier for an object is declared with no linkage and the type of the object is
28770 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
28771 <li> A function is declared at block scope with an explicit storage-class specifier other
28773 <li> A structure or union is defined without any named members (including those
28775 <li> An attempt is made to access, or generate a pointer to just past, a flexible array
28776 member of a structure when the referenced object provides no elements for that array
28778 <li> When the complete type is needed, an incomplete structure or union type is not
28779 completed in the same scope by another declaration of the tag that defines the content
28781 <li> An attempt is made to modify an object defined with a const-qualified type through
28783 <li> An attempt is made to refer to an object defined with a volatile-qualified type through
28785 <li> The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>).
28786 <li> Two qualified types that are required to be compatible do not have the identically
28788 <li> An object which has been modified is accessed through a restrict-qualified pointer to
28789 a const-qualified type, or through a restrict-qualified pointer and another pointer that
28790 <!--page 580 -->
28792 <li> A restrict-qualified pointer is assigned a value based on another restricted pointer
28793 whose associated block neither began execution before the block associated with this
28795 <li> A function with external linkage is declared with an inline function specifier, but is
28797 <li> A function declared with a _Noreturn function specifier returns to its caller (<a href="#6.7.4">6.7.4</a>).
28798 <li> The definition of an object has an alignment specifier and another declaration of that
28800 <li> Declarations of an object in different translation units have different alignment
28802 <li> Two pointer types that are required to be compatible are not identically qualified, or
28804 <li> The size expression in an array declaration is not a constant expression and evaluates
28806 <li> In a context requiring two array types to be compatible, they do not have compatible
28807 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.6.2">6.7.6.2</a>).
28808 <li> A declaration of an array parameter includes the keyword static within the [ and
28809 ] and the corresponding argument does not provide access to the first element of an
28811 <li> A storage-class specifier or type qualifier modifies the keyword void as a function
28813 <li> In a context requiring two function types to be compatible, they do not have
28814 compatible return types, or their parameters disagree in use of the ellipsis terminator
28815 or the number and type of parameters (after default argument promotion, when there
28816 is no parameter type list or when one type is specified by a function definition with an
28818 <li> The value of an unnamed member of a structure or union is used (<a href="#6.7.9">6.7.9</a>).
28819 <li> The initializer for a scalar is neither a single expression nor a single expression
28821 <li> The initializer for a structure or union object that has automatic storage duration is
28822 neither an initializer list nor a single expression that has compatible structure or union
28824 <li> The initializer for an aggregate or union, other than an array initialized by a string
28825 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.9">6.7.9</a>).
28826 <!--page 581 -->
28827 <li> An identifier with external linkage is used, but in the program there does not exist
28828 exactly one external definition for the identifier, or the identifier is not used and there
28830 <li> A function definition includes an identifier list, but the types of the parameters are not
28832 <li> An adjusted parameter type in a function definition is not a complete object type
28834 <li> A function that accepts a variable number of arguments is defined without a
28836 <li> The } that terminates a function is reached, and the value of the function call is used
28838 <li> An identifier for an object with internal linkage and an incomplete type is declared
28840 <li> The token defined is generated during the expansion of a #if or #elif
28841 preprocessing directive, or the use of the defined unary operator does not match
28843 <li> The #include preprocessing directive that results after expansion does not match
28845 <li> The character sequence in an #include preprocessing directive does not start with a
28847 <li> There are sequences of preprocessing tokens within the list of macro arguments that
28849 <li> The result of the preprocessing operator # is not a valid character string literal
28851 <li> The result of the preprocessing operator ## is not a valid preprocessing token
28853 <li> The #line preprocessing directive that results after expansion does not match one of
28854 the two well-defined forms, or its digit sequence specifies zero or a number greater
28856 <li> A non-STDC #pragma preprocessing directive that is documented as causing
28857 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
28858 <li> A #pragma STDC preprocessing directive does not match one of the well-defined
28860 <li> The name of a predefined macro, or the identifier defined, is the subject of a
28862 <!--page 582 -->
28863 <li> An attempt is made to copy an object to an overlapping object by use of a library
28864 function, other than as explicitly allowed (e.g., memmove) (clause 7).
28865 <li> A file with the same name as one of the standard headers, not provided as part of the
28866 implementation, is placed in any of the standard places that are searched for included
28868 <li> A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
28869 <li> A function, object, type, or macro that is specified as being declared or defined by
28870 some standard header is used before any header that declares or defines it is included
28872 <li> A standard header is included while a macro is defined with the same name as a
28874 <li> The program attempts to declare a library function itself, rather than via a standard
28876 <li> The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
28878 <li> The program removes the definition of a macro whose name begins with an
28880 <li> An argument to a library function has an invalid value or a type not expected by a
28882 <li> The pointer passed to a library function array parameter does not have a value such
28884 <li> The macro definition of assert is suppressed in order to access an actual function
28887 <li> The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
28888 any context other than outside all external declarations or preceding all explicit
28889 declarations and statements inside a compound statement (<a href="#7.3.4">7.3.4</a>, <a href="#7.6.1">7.6.1</a>, <a href="#7.12.2">7.12.2</a>).
28890 <li> The value of an argument to a character handling function is neither equal to the value
28892 <li> A macro definition of errno is suppressed in order to access an actual object, or the
28894 <li> Part of the program tests floating-point status flags, sets floating-point control modes,
28895 or runs under non-default mode settings, but was translated with the state for the
28897 <!--page 583 -->
28898 <li> The exception-mask argument for one of the functions that provide access to the
28899 floating-point status flags has a nonzero value not obtained by bitwise OR of the
28901 <li> The fesetexceptflag function is used to set floating-point status flags that were
28902 not specified in the call to the fegetexceptflag function that provided the value
28904 <li> The argument to fesetenv or feupdateenv is neither an object set by a call to
28905 fegetenv or feholdexcept, nor is it an environment macro (<a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.6.4.4">7.6.4.4</a>).
28906 <li> The value of the result of an integer arithmetic or conversion function cannot be
28907 represented (<a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.22.6.1">7.22.6.1</a>, <a href="#7.22.6.2">7.22.6.2</a>, <a href="#7.22.1">7.22.1</a>).
28908 <li> The program modifies the string pointed to by the value returned by the setlocale
28910 <li> The program modifies the structure pointed to by the value returned by the
28912 <li> A macro definition of math_errhandling is suppressed or the program defines
28914 <li> An argument to a floating-point classification or comparison macro is not of real
28916 <li> A macro definition of setjmp is suppressed in order to access an actual function, or
28918 <li> An invocation of the setjmp macro occurs other than in an allowed context
28920 <li> The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
28921 <li> After a longjmp, there is an attempt to access the value of an object of automatic
28922 storage duration that does not have volatile-qualified type, local to the function
28923 containing the invocation of the corresponding setjmp macro, that was changed
28925 <li> The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
28926 <li> A signal handler returns when the signal corresponded to a computational exception
28928 <li> A signal handler called in response to SIGFPE, SIGILL, SIGSEGV, or any other
28929 implementation-defined value corresponding to a computational exception returns
28931 <li> A signal occurs as the result of calling the abort or raise function, and the signal
28933 <!--page 584 -->
28934 <li> A signal occurs other than as the result of calling the abort or raise function, and
28935 the signal handler refers to an object with static or thread storage duration that is not a
28936 lock-free atomic object other than by assigning a value to an object declared as
28937 volatile sig_atomic_t, or calls any function in the standard library other
28938 than the abort function, the _Exit function, the quick_exit function, or the
28940 <li> The value of errno is referred to after a signal occurred other than as the result of
28941 calling the abort or raise function and the corresponding signal handler obtained
28943 <li> A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
28944 <li> The signal function is used in a multi-threaded program (<a href="#7.14.1.1">7.14.1.1</a>).
28945 <li> A function with a variable number of arguments attempts to access its varying
28946 arguments other than through a properly declared and initialized va_list object, or
28947 before the va_start macro is invoked (<a href="#7.16">7.16</a>, <a href="#7.16.1.1">7.16.1.1</a>, <a href="#7.16.1.4">7.16.1.4</a>).
28948 <li> The macro va_arg is invoked using the parameter ap that was passed to a function
28950 <li> A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
28951 order to access an actual function, or the program defines an external identifier with
28953 <li> The va_start or va_copy macro is invoked without a corresponding invocation
28954 of the va_end macro in the same function, or vice versa (<a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.3">7.16.1.3</a>,
28956 <li> The type parameter to the va_arg macro is not such that a pointer to an object of
28958 <li> The va_arg macro is invoked when there is no actual next argument, or with a
28959 specified type that is not compatible with the promoted type of the actual next
28961 <li> The va_copy or va_start macro is called to initialize a va_list that was
28962 previously initialized by either macro without an intervening invocation of the
28963 va_end macro for the same va_list (<a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.4">7.16.1.4</a>).
28964 <li> The parameter parmN of a va_start macro is declared with the register
28965 storage class, with a function or array type, or with a type that is not compatible with
28966 the type that results after application of the default argument promotions (<a href="#7.16.1.4">7.16.1.4</a>).
28967 <li> The member designator parameter of an offsetof macro is an invalid right
28968 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.19">7.19</a>).
28969 <!--page 585 -->
28970 <li> The argument in an instance of one of the integer-constant macros is not a decimal,
28971 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
28973 <li> A byte input/output function is applied to a wide-oriented stream, or a wide character
28975 <li> Use is made of any portion of a file beyond the most recent wide character written to
28977 <li> The value of a pointer to a FILE object is used after the associated file is closed
28979 <li> The stream for the fflush function points to an input stream or to an update stream
28981 <li> The string pointed to by the mode argument in a call to the fopen function does not
28983 <li> An output operation on an update stream is followed by an input operation without an
28984 intervening call to the fflush function or a file positioning function, or an input
28985 operation on an update stream is followed by an output operation with an intervening
28987 <li> An attempt is made to use the contents of the array that was supplied in a call to the
28989 <li> There are insufficient arguments for the format in a call to one of the formatted
28990 input/output functions, or an argument does not have an appropriate type (<a href="#7.21.6.1">7.21.6.1</a>,
28991 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>).
28992 <li> The format in a call to one of the formatted input/output functions or to the
28993 strftime or wcsftime function is not a valid multibyte character sequence that
28994 begins and ends in its initial shift state (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>,
28996 <li> In a call to one of the formatted output functions, a precision appears with a
28997 conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
28998 <li> A conversion specification for a formatted output function uses an asterisk to denote
28999 an argument-supplied field width or precision, but the corresponding argument is not
29002 conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
29003 <li> A conversion specification for one of the formatted input/output functions uses a
29004 length modifier with a conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>,
29005 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29006 <!--page 586 -->
29007 <li> An s conversion specifier is encountered by one of the formatted output functions,
29008 and the argument is missing the null terminator (unless a precision is specified that
29009 does not require null termination) (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
29010 <li> An n conversion specification for one of the formatted input/output functions includes
29011 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.21.6.1">7.21.6.1</a>,
29012 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29013 <li> A % conversion specifier is encountered by one of the formatted input/output
29014 functions, but the complete conversion specification is not exactly %% (<a href="#7.21.6.1">7.21.6.1</a>,
29015 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29016 <li> An invalid conversion specification is found in the format for one of the formatted
29017 input/output functions, or the strftime or wcsftime function (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
29018 <a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.5.1">7.29.5.1</a>).
29019 <li> The number of characters or wide characters transmitted by a formatted output
29020 function (or written to an array, or that would have been written to an array) is greater
29022 <li> The number of input items assigned by a formatted input function is greater than
29024 <li> The result of a conversion by one of the formatted input functions cannot be
29025 represented in the corresponding object, or the receiving object does not have an
29027 <li> A c, s, or [ conversion specifier is encountered by one of the formatted input
29028 functions, and the array pointed to by the corresponding argument is not large enough
29029 to accept the input sequence (and a null terminator if the conversion specifier is s or
29031 <li> A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
29032 formatted input functions, but the input is not a valid multibyte character sequence
29033 that begins in the initial shift state (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29034 <li> The input item for a %p conversion by one of the formatted input functions is not a
29035 value converted earlier during the same program execution (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29036 <li> The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
29037 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
29038 vwscanf function is called with an improperly initialized va_list argument, or
29039 the argument is used (other than in an invocation of va_end) after the function
29040 returns (<a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>, <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>,
29041 <a href="#7.29.2.5">7.29.2.5</a>, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.7">7.29.2.7</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.10">7.29.2.10</a>).
29042 <li> The contents of the array supplied in a call to the fgets or fgetws function are
29043 used after a read error occurred (<a href="#7.21.7.2">7.21.7.2</a>, <a href="#7.29.3.2">7.29.3.2</a>).
29044 <!--page 587 -->
29045 <li> The file position indicator for a binary stream is used after a call to the ungetc
29047 <li> The file position indicator for a stream is used after an error occurred during a call to
29048 the fread or fwrite function (<a href="#7.21.8.1">7.21.8.1</a>, <a href="#7.21.8.2">7.21.8.2</a>).
29049 <li> A partial element read by a call to the fread function is used (<a href="#7.21.8.1">7.21.8.1</a>).
29050 <li> The fseek function is called for a text stream with a nonzero offset and either the
29051 offset was not returned by a previous successful call to the ftell function on a
29052 stream associated with the same file or whence is not SEEK_SET (<a href="#7.21.9.2">7.21.9.2</a>).
29053 <li> The fsetpos function is called to set a position that was not returned by a previous
29054 successful call to the fgetpos function on a stream associated with the same file
29056 <li> A non-null pointer returned by a call to the calloc, malloc, or realloc function
29058 <li> The value of a pointer that refers to space deallocated by a call to the free or
29060 <li> The alignment requested of the aligned_alloc function is not valid or not
29061 supported by the implementation, or the size requested is not an integral multiple of
29063 <li> The pointer argument to the free or realloc function does not match a pointer
29064 earlier returned by a memory management function, or the space has been deallocated
29065 by a call to free or realloc (<a href="#7.22.3.3">7.22.3.3</a>, <a href="#7.22.3.5">7.22.3.5</a>).
29066 <li> The value of the object allocated by the malloc function is used (<a href="#7.22.3.4">7.22.3.4</a>).
29067 <li> The value of any bytes in a new object allocated by the realloc function beyond
29069 <li> The program calls the exit or quick_exit function more than once, or calls both
29071 <li> During the call to a function registered with the atexit or at_quick_exit
29072 function, a call is made to the longjmp function that would terminate the call to the
29074 <li> The string set up by the getenv or strerror function is modified by the program
29076 <li> A signal is raised while the quick_exit function is executing (<a href="#7.22.4.7">7.22.4.7</a>).
29077 <li> A command is executed through the system function in a way that is documented as
29078 causing termination or some other form of undefined behavior (<a href="#7.22.4.8">7.22.4.8</a>).
29079 <!--page 588 -->
29080 <li> A searching or sorting utility function is called with an invalid pointer argument, even
29082 <li> The comparison function called by a searching or sorting utility function alters the
29083 contents of the array being searched or sorted, or returns ordering values
29085 <li> The array being searched by the bsearch function does not have its elements in
29087 <li> The current conversion state is used by a multibyte/wide character conversion
29089 <li> A string or wide string utility function is instructed to access an array beyond the end
29091 <li> A string or wide string utility function is called with an invalid pointer argument, even
29093 <li> The contents of the destination array are used after a call to the strxfrm,
29094 strftime, wcsxfrm, or wcsftime function in which the specified length was
29095 too small to hold the entire null-terminated result (<a href="#7.24.4.5">7.24.4.5</a>, <a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.4.4.4">7.29.4.4.4</a>,
29097 <li> The first argument in the very first call to the strtok or wcstok is a null pointer
29099 <li> The type of an argument to a type-generic macro is not compatible with the type of
29101 <li> A complex argument is supplied for a generic parameter of a type-generic macro that
29103 <li> At least one member of the broken-down time passed to asctime contains a value
29104 outside its normal range, or the calculated year exceeds four digits or is less than the
29106 <li> The argument corresponding to an s specifier without an l qualifier in a call to the
29107 fwprintf function does not point to a valid multibyte character sequence that
29109 <li> In a call to the wcstok function, the object pointed to by ptr does not have the
29110 value stored by the previous call for the same wide string (<a href="#7.29.4.5.7">7.29.4.5.7</a>).
29112 <li> The value of an argument of type wint_t to a wide character classification or case
29113 mapping function is neither equal to the value of WEOF nor representable as a
29115 <!--page 589 -->
29116 <li> The iswctype function is called using a different LC_CTYPE category from the
29117 one in effect for the call to the wctype function that returned the description
29119 <li> The towctrans function is called using a different LC_CTYPE category from the
29120 one in effect for the call to the wctrans function that returned the description
29122 </ul>
29127 A conforming implementation is required to document its choice of behavior in each of
29128 the areas listed in this subclause. The following are implementation-defined:
29133 <ul>
29134 <li> How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
29135 <li> Whether each nonempty sequence of white-space characters other than new-line is
29136 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
29137 </ul>
29142 <ul>
29143 <li> The mapping between physical source file multibyte characters and the source
29145 <li> The name and type of the function called at program startup in a freestanding
29147 <li> The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
29148 <li> An alternative manner in which the main function may be defined (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
29149 <li> The values given to the strings pointed to by the argv argument to main (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
29151 <li> Whether a program can have more than one thread of execution in a freestanding
29153 <li> The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
29154 <li> Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
29156 <li> Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
29158 <li> The set of environment names and the method for altering the environment list used
29160 <li> The manner of execution of the string by the system function (<a href="#7.22.4.8">7.22.4.8</a>).
29161 <!--page 590 -->
29162 </ul>
29167 <ul>
29168 <li> Which additional multibyte characters may appear in identifiers and their
29170 <li> The number of significant initial characters in an identifier (<a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2">6.4.2</a>).
29171 </ul>
29176 <ul>
29179 <li> The unique value of the member of the execution character set produced for each of
29181 <li> The value of a char object into which has been stored any character other than a
29183 <li> Which of signed char or unsigned char has the same range, representation,
29185 <li> The mapping of members of the source character set (in character constants and string
29186 literals) to members of the execution character set (<a href="#6.4.4.4">6.4.4.4</a>, <a href="#5.1.1.2">5.1.1.2</a>).
29187 <li> The value of an integer character constant containing more than one character or
29188 containing a character or escape sequence that does not map to a single-byte
29190 <li> The value of a wide character constant containing more than one multibyte character
29191 or a single multibyte character that maps to multiple members of the extended
29192 execution character set, or containing a multibyte character or escape sequence not
29194 <li> The current locale used to convert a wide character constant consisting of a single
29195 multibyte character that maps to a member of the extended execution character set
29197 <li> Whether differently-prefixed wide string literal tokens can be concatenated and, if so,
29199 <li> The current locale used to convert a wide string literal into corresponding wide
29201 <li> The value of a string literal containing a multibyte character or escape sequence not
29203 <li> The encoding of any of wchar_t, char16_t, and char32_t where the
29204 corresponding standard encoding macro (__STDC_ISO_10646__,
29206 <!--page 591 -->
29207 </ul>
29212 <ul>
29213 <li> Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
29214 <li> Whether signed integer types are represented using sign and magnitude, two's
29215 complement, or ones' complement, and whether the extraordinary value is a trap
29217 <li> The rank of any extended integer type relative to another extended integer type with
29219 <li> The result of, or the signal raised by, converting an integer to a signed integer type
29220 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
29222 </ul>
29227 <ul>
29228 <li> The accuracy of the floating-point operations and of the library functions in
29229 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
29230 <li> The accuracy of the conversions between floating-point internal representations and
29231 string representations performed by the library functions in <a href="#7.21"><stdio.h></a>,
29232 <a href="#7.22"><stdlib.h></a>, and <a href="#7.29"><wchar.h></a> (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
29233 <li> The rounding behaviors characterized by non-standard values of FLT_ROUNDS
29235 <li> The evaluation methods characterized by non-standard negative values of
29237 <li> The direction of rounding when an integer is converted to a floating-point number that
29239 <li> The direction of rounding when a floating-point number is converted to a narrower
29241 <li> How the nearest representable value or the larger or smaller representable value
29242 immediately adjacent to the nearest representable value is chosen for certain floating
29244 <li> Whether and how floating expressions are contracted when not disallowed by the
29247 <li> Additional floating-point exceptions, rounding modes, environments, and
29250 <!--page 592 -->
29251 </ul>
29256 <ul>
29257 <li> The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
29258 <li> The size of the result of subtracting two pointers to elements of the same array
29260 </ul>
29265 <ul>
29266 <li> The extent to which suggestions made by using the register storage-class
29268 <li> The extent to which suggestions made by using the inline function specifier are
29270 </ul>
29273 <h4><a name="J.3.9" href="#J.3.9">J.3.9 Structures, unions, enumerations, and bit-fields</a></h4>
29275 <ul>
29276 <li> Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
29278 <li> Allowable bit-field types other than _Bool, signed int, and unsigned int
29281 <li> Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
29283 <li> The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
29284 no problem unless binary data written by one implementation is read by another.
29286 </ul>
29291 <ul>
29292 <li> What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
29293 </ul>
29298 <ul>
29299 <li> The locations within #pragma directives where header name preprocessing tokens
29301 <li> How sequences in both forms of header names are mapped to headers or external
29303 <li> Whether the value of a character constant in a constant expression that controls
29304 conditional inclusion matches the value of the same character constant in the
29306 <li> Whether the value of a single-character character constant in a constant expression
29308 <!--page 593 -->
29309 <li> The places that are searched for an included < > delimited header, and how the places
29313 <li> The method by which preprocessing tokens (possibly resulting from macro
29314 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
29316 <li> Whether the # operator inserts a \ character before the \ character that begins a
29317 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
29318 <li> The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
29319 <li> The definitions for __DATE__ and __TIME__ when respectively, the date and
29321 </ul>
29326 <ul>
29327 <li> Any library facilities available to a freestanding program, other than the minimal set
29329 <li> The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
29330 <li> The representation of the floating-point status flags stored by the
29332 <li> Whether the feraiseexcept function raises the ''inexact'' floating-point
29333 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
29337 <li> The types defined for float_t and double_t when the value of the
29339 <li> Domain errors for the mathematics functions, other than those required by this
29341 <li> The values returned by the mathematics functions on domain errors or pole errors
29343 <li> The values returned by the mathematics functions on underflow range errors, whether
29344 errno is set to the value of the macro ERANGE when the integer expression
29345 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
29346 floating-point exception is raised when the integer expression math_errhandling
29348 <!--page 594 -->
29349 <li> Whether a domain error occurs or zero is returned when an fmod function has a
29351 <li> Whether a domain error occurs or zero is returned when a remainder function has
29355 <li> Whether a domain error occurs or zero is returned when a remquo function has a
29357 <li> Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
29358 of a signal handler, and, if not, the blocking of signals that is performed (<a href="#7.14.1.1">7.14.1.1</a>).
29360 <li> Whether the last line of a text stream requires a terminating new-line character
29362 <li> Whether space characters that are written out to a text stream immediately before a
29364 <li> The number of null characters that may be appended to data written to a binary
29366 <li> Whether the file position indicator of an append-mode stream is initially positioned at
29368 <li> Whether a write on a text stream causes the associated file to be truncated beyond that
29373 <li> Whether the same file can be simultaneously open multiple times (<a href="#7.21.3">7.21.3</a>).
29374 <li> The nature and choice of encodings used for multibyte characters in files (<a href="#7.21.3">7.21.3</a>).
29376 <li> The effect if a file with the new name exists prior to a call to the rename function
29378 <li> Whether an open temporary file is removed upon abnormal program termination
29380 <li> Which changes of mode are permitted (if any), and under what circumstances
29382 <!--page 595 -->
29383 <li> The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
29384 sequence printed for a NaN (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>).
29385 <li> The output for %p conversion in the fprintf or fwprintf function (<a href="#7.21.6.1">7.21.6.1</a>,
29387 <li> The interpretation of a - character that is neither the first nor the last character, nor
29388 the second where a ^ character is the first, in the scanlist for %[ conversion in the
29389 fscanf or fwscanf function (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>).
29390 <li> The set of sequences matched by a %p conversion and the interpretation of the
29391 corresponding input item in the fscanf or fwscanf function (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>).
29392 <li> The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
29393 functions on failure (<a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.9.4">7.21.9.4</a>).
29394 <li> The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
29395 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
29397 <li> Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
29398 function sets errno to ERANGE when underflow occurs (<a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>).
29399 <li> Whether the calloc, malloc, and realloc functions return a null pointer or a
29400 pointer to an allocated object when the size requested is zero (<a href="#7.22.3">7.22.3</a>).
29401 <li> Whether open streams with unwritten buffered data are flushed, open streams are
29402 closed, or temporary files are removed when the abort or _Exit function is called
29404 <li> The termination status returned to the host environment by the abort, exit,
29405 _Exit, or quick_exit function (<a href="#7.22.4.1">7.22.4.1</a>, <a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>).
29406 <li> The value returned by the system function when its argument is not a null pointer
29408 <li> The range and precision of times representable in clock_t and time_t (<a href="#7.27">7.27</a>). *
29412 <li> The replacement string for the %Z specifier to the strftime, and wcsftime
29413 functions in the "C" locale (<a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.5.1">7.29.5.1</a>).
29414 <li> Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
29415 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.10">F.10</a>).
29416 <!--page 596 -->
29417 </ul>
29422 <ul>
29423 <li> The values or expressions assigned to the macros specified in the headers
29424 <a href="#7.7"><float.h></a>, <a href="#7.10"><limits.h></a>, and <a href="#7.20"><stdint.h></a> (<a href="#5.2.4.2">5.2.4.2</a>, <a href="#7.20.2">7.20.2</a>, <a href="#7.20.3">7.20.3</a>).
29425 <li> The result of attempting to indirectly access an object with automatic or thread
29426 storage duration from a thread other than the one with which it is associated (<a href="#6.2.4">6.2.4</a>).
29427 <li> The number, order, and encoding of bytes in any object (when not explicitly specified
29429 <li> Whether any extended alignments are supported and the contexts in which they are
29431 <li> Valid alignment values other than those returned by an _Alignof expression for
29433 <li> The value of the result of the sizeof and _Alignof operators (<a href="#6.5.3.4">6.5.3.4</a>).
29434 </ul>
29439 The following characteristics of a hosted environment are locale-specific and are required
29440 to be documented by the implementation:
29441 <ul>
29442 <li> Additional members of the source and execution character sets beyond the basic
29444 <li> The presence, meaning, and representation of additional multibyte characters in the
29446 <li> The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
29451 <li> The sets of characters tested for by the isalpha, isblank, islower, ispunct,
29452 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
29453 iswspace, or iswupper functions (<a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, <a href="#7.4.1.10">7.4.1.10</a>,
29454 <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.30.2.1.2">7.30.2.1.2</a>, <a href="#7.30.2.1.3">7.30.2.1.3</a>, <a href="#7.30.2.1.7">7.30.2.1.7</a>, <a href="#7.30.2.1.9">7.30.2.1.9</a>, <a href="#7.30.2.1.10">7.30.2.1.10</a>, <a href="#7.30.2.1.11">7.30.2.1.11</a>).
29456 <li> Additional subject sequences accepted by the numeric conversion functions (<a href="#7.22.1">7.22.1</a>,
29458 <li> The collation sequence of the execution character set (<a href="#7.24.4.3">7.24.4.3</a>, <a href="#7.29.4.4.2">7.29.4.4.2</a>).
29459 <!--page 597 -->
29460 <li> The contents of the error message strings set up by the strerror function
29462 <li> The formats for time and date (<a href="#7.27.3.5">7.27.3.5</a>, <a href="#7.29.5.1">7.29.5.1</a>).
29463 <li> Character mappings that are supported by the towctrans function (<a href="#7.30.1">7.30.1</a>).
29464 <li> Character classifications that are supported by the iswctype function (<a href="#7.30.1">7.30.1</a>).
29465 </ul>
29470 The following extensions are widely used in many systems, but are not portable to all
29471 implementations. The inclusion of any extension that may cause a strictly conforming
29472 program to become invalid renders an implementation nonconforming. Examples of such
29473 extensions are new keywords, extra library functions declared in standard headers, or
29474 predefined macros with names that do not begin with an underscore.
29479 In a hosted environment, the main function receives a third argument, char *envp[],
29480 that points to a null-terminated array of pointers to char, each of which points to a string
29481 that provides information about the environment for this execution of the program
29487 Characters other than the underscore _, letters, and digits, that are not part of the basic
29488 source character set (such as the dollar sign $, or characters in national character sets)
29494 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
29499 A function identifier, or the identifier of an object the declaration of which contains the
29505 String literals are modifiable (in which case, identical string literals should denote distinct
29507 <!--page 598 -->
29512 Additional arithmetic types, such as __int128 or double double, and their
29513 appropriate conversions are defined (<a href="#6.2.5">6.2.5</a>, <a href="#6.3.1">6.3.1</a>). Additional floating types may have
29514 more range or precision than long double, may be used for evaluating expressions of
29515 other floating types, and may be used to define float_t or double_t. Additional
29516 floating types may also have less range or precision than float.
29521 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
29524 A pointer to a function may be cast to a pointer to an object or to void, allowing a
29525 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
29530 A bit-field may be declared with a type other than _Bool, unsigned int, or
29536 The fortran function specifier may be used in a function declaration to indicate that
29537 calls suitable for FORTRAN should be generated, or that a different representation for the
29543 The asm keyword may be used to insert assembly language directly into the translator
29544 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
29545 <pre>
29546 asm ( character-string-literal );
29547 </pre>
29552 There may be more than one external definition for the identifier of an object, with or
29553 without the explicit use of the keyword extern; if the definitions disagree, or more than
29555 <!--page 599 -->
29560 Macro names that do not begin with an underscore, describing the translation and
29561 execution environments, are defined by the implementation before translation begins
29567 If any floating-point status flags are set on normal termination after all calls to functions
29568 registered by the atexit function have been made (see <a href="#7.22.4.4">7.22.4.4</a>), the implementation
29569 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
29574 Handlers for specific signals are called with extra arguments in addition to the signal
29578 <h4><a name="J.5.15" href="#J.5.15">J.5.15 Additional stream types and file-opening modes</a></h4>
29582 Additional file-opening modes may be specified by characters appended to the mode
29588 The file position indicator is decremented by each successful call to the ungetc or
29589 ungetwc function for a text stream, except if its value was zero before a call (<a href="#7.21.7.10">7.21.7.10</a>,
29595 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
29596 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
29598 <!--page 600 -->
29602 <pre>
29603 (normative)
29604 Bounds-checking interfaces
29605 </pre>
29610 Traditionally, the C Library has contained many functions that trust the programmer to
29611 provide output character arrays big enough to hold the result being produced. Not only
29612 do these functions not check that the arrays are big enough, they frequently lack the
29613 information needed to perform such checks. While it is possible to write safe, robust, and
29614 error-free code using the existing library, the library tends to promote programming styles
29615 that lead to mysterious failures if a result is too big for the provided array.
29617 A common programming style is to declare character arrays large enough to handle most
29618 practical cases. However, if these arrays are not large enough to handle the resulting
29619 strings, data can be written past the end of the array overwriting other data and program
29620 structures. The program never gets any indication that a problem exists, and so never has
29621 a chance to recover or to fail gracefully.
29623 Worse, this style of programming has compromised the security of computers and
29624 networks. Buffer overflows can often be exploited to run arbitrary code with the
29625 permissions of the vulnerable (defective) program.
29627 If the programmer writes runtime checks to verify lengths before calling library
29628 functions, then those runtime checks frequently duplicate work done inside the library
29629 functions, which discover string lengths as a side effect of doing their job.
29631 This annex provides alternative library functions that promote safer, more secure
29632 programming. The alternative functions verify that output buffers are large enough for
29633 the intended result and return a failure indicator if they are not. Data is never written past
29634 the end of an array. All string results are null terminated.
29636 This annex also addresses another problem that complicates writing robust code:
29637 functions that are not reentrant because they return pointers to static objects owned by the
29638 function. Such functions can be troublesome since a previously returned result can
29639 change if the function is called again, perhaps by another thread.
29640 <!--page 601 -->
29645 This annex specifies a series of optional extensions that can be useful in the mitigation of
29646 security vulnerabilities in programs, and comprise new functions, macros, and types
29647 declared or defined in existing standard headers.
29649 An implementation that defines __STDC_LIB_EXT1__ shall conform to the
29652 Subclause <a href="#K.3">K.3</a> should be read as if it were merged into the parallel structure of named
29653 subclauses of clause 7.
29656 <p><small><a name="note380" href="#note380">380)</a> Implementations that do not define __STDC_LIB_EXT1__ are not required to conform to these
29657 specifications.
29658 </small>
29669 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are not
29670 declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
29671 defined as a macro which expands to the integer constant 0 at the point in the source file
29672 where the appropriate header is first included.
29674 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are
29675 declared and defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
29676 defined as a macro which expands to the integer constant 1 at the point in the source file
29679 It is implementation-defined whether the functions, macros, and types declared or defined
29680 in <a href="#K.3">K.3</a> and its subclauses are declared or defined by their respective headers if
29681 __STDC_WANT_LIB_EXT1__ is not defined as a macro at the point in the source file
29684 Within a preprocessing translation unit, __STDC_WANT_LIB_EXT1__ shall be
29685 defined identically for all inclusions of any headers from subclause <a href="#K.3">K.3</a>. If
29686 __STDC_WANT_LIB_EXT1__ is defined differently for any such inclusion, the
29687 implementation shall issue a diagnostic as if a preprocessor error directive were used.
29690 <!--page 602 -->
29693 <p><small><a name="note381" href="#note381">381)</a> Future revisions of this International Standard may define meanings for other values of
29694 __STDC_WANT_LIB_EXT1__.
29695 </small>
29696 <p><small><a name="note382" href="#note382">382)</a> Subclause <a href="#7.1.3">7.1.3</a> reserves certain names and patterns of names that an implementation may use in
29697 headers. All other names are not reserved, and a conforming implementation is not permitted to use
29698 them. While some of the names defined in <a href="#K.3">K.3</a> and its subclauses are reserved, others are not. If an
29699 unreserved name is defined in a header when __STDC_WANT_LIB_EXT1__ is defined as 0, the
29700 implementation is not conforming.
29701 </small>
29706 Each macro name in any of the following subclauses is reserved for use as specified if it
29707 is defined by any of its associated headers when included; unless explicitly stated
29710 All identifiers with external linkage in any of the following subclauses are reserved for
29711 use as identifiers with external linkage if any of them are used by the program. None of
29712 them are reserved if none of them are used.
29714 Each identifier with file scope listed in any of the following subclauses is reserved for use
29715 as a macro name and as an identifier with file scope in the same name space if it is
29716 defined by any of its associated headers when included.
29721 An implementation may set errno for the functions defined in this annex, but is not
29722 required to.
29727 Most functions in this annex include as part of their specification a list of runtime-
29728 constraints. These runtime-constraints are requirements on the program using the
29731 Implementations shall verify that the runtime-constraints for a function are not violated
29732 by the program. If a runtime-constraint is violated, the implementation shall call the
29733 currently registered runtime-constraint handler (see set_constraint_handler_s
29734 in <a href="#7.22"><stdlib.h></a>). Multiple runtime-constraint violations in the same call to a library
29735 function result in only one call to the runtime-constraint handler. It is unspecified which
29736 one of the multiple runtime-constraint violations cause the handler to be called.
29738 If the runtime-constraints section for a function states an action to be performed when a
29739 runtime-constraint violation occurs, the function shall perform the action before calling
29740 the runtime-constraint handler. If the runtime-constraints section lists actions that are
29741 prohibited when a runtime-constraint violation occurs, then such actions are prohibited to
29742 the function both before calling the handler and after the handler returns.
29744 The runtime-constraint handler might not return. If the handler does return, the library
29745 function whose runtime-constraint was violated shall return some indication of failure as
29746 given by the returns section in the function's specification.
29750 <!--page 603 -->
29753 <p><small><a name="note383" href="#note383">383)</a> Although runtime-constraints replace many cases of undefined behavior, undefined behavior still
29754 exists in this annex. Implementations are free to detect any case of undefined behavior and treat it as a
29755 runtime-constraint violation by calling the runtime-constraint handler. This license comes directly
29756 from the definition of undefined behavior.
29757 </small>
29764 The type is
29765 <pre>
29766 errno_t
29767 </pre>
29771 <p><small><a name="note384" href="#note384">384)</a> As a matter of programming style, errno_t may be used as the type of something that deals only
29772 with the values that might be found in errno. For example, a function which returns the value of
29773 errno might be declared as having the return type errno_t.
29774 </small>
29781 The type is
29782 <pre>
29783 rsize_t
29784 </pre>
29788 <p><small><a name="note385" href="#note385">385)</a> See the description of the RSIZE_MAX macro in <a href="#7.20"><stdint.h></a>.
29789 </small>
29796 The macro is
29797 <pre>
29798 RSIZE_MAX
29799 </pre>
29800 which expands to a value<sup><a href="#note386"><b>386)</b></a></sup> of type size_t. Functions that have parameters of type
29801 rsize_t consider it a runtime-constraint violation if the values of those parameters are
29802 greater than RSIZE_MAX.
29805 Extremely large object sizes are frequently a sign that an object's size was calculated
29806 incorrectly. For example, negative numbers appear as very large positive numbers when
29807 converted to an unsigned type like size_t. Also, some implementations do not support
29808 objects as large as the maximum value that can be represented by type size_t.
29810 For those reasons, it is sometimes beneficial to restrict the range of object sizes to detect
29811 programming errors. For implementations targeting machines with large address spaces,
29812 it is recommended that RSIZE_MAX be defined as the smaller of the size of the largest
29814 some legitimate, but very large, objects. Implementations targeting machines with small
29815 address spaces may wish to define RSIZE_MAX as SIZE_MAX, which means that there
29817 <!--page 604 -->
29818 is no object size that is considered a runtime-constraint violation.
29821 <p><small><a name="note386" href="#note386">386)</a> The macro RSIZE_MAX need not expand to a constant expression.
29822 </small>
29829 The macros are
29830 <pre>
29831 L_tmpnam_s
29832 </pre>
29833 which expands to an integer constant expression that is the size needed for an array of
29834 char large enough to hold a temporary file name string generated by the tmpnam_s
29835 function;
29836 <pre>
29837 TMP_MAX_S
29838 </pre>
29839 which expands to an integer constant expression that is the maximum number of unique
29840 file names that can be generated by the tmpnam_s function.
29842 The types are
29843 <pre>
29844 errno_t
29845 </pre>
29846 which is type int; and
29847 <pre>
29848 rsize_t
29849 </pre>
29850 which is the type size_t.
29859 <pre>
29860 #define __STDC_WANT_LIB_EXT1__ 1
29862 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
29863 </pre>
29864 Runtime-constraints
29866 streamptr shall not be a null pointer.
29868 If there is a runtime-constraint violation, tmpfile_s does not attempt to create a file.
29871 The tmpfile_s function creates a temporary binary file that is different from any other
29872 existing file and that will automatically be removed when it is closed or at program
29873 termination. If the program terminates abnormally, whether an open temporary file is
29874 removed is implementation-defined. The file is opened for update with "wb+" mode
29875 with the meaning that mode has in the fopen_s function (including the mode's effect
29876 on exclusive access and file permissions).
29877 <!--page 605 -->
29879 If the file was created successfully, then the pointer to FILE pointed to by streamptr
29880 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
29881 to FILE pointed to by streamptr will be set to a null pointer.
29883 It should be possible to open at least TMP_MAX_S temporary files during the lifetime of
29884 the program (this limit may be shared with tmpnam_s) and there should be no limit on
29885 the number simultaneously open other than this limit and any limit on the number of open
29886 files (FOPEN_MAX).
29889 The tmpfile_s function returns zero if it created the file. If it did not create the file or
29890 there was a runtime-constraint violation, tmpfile_s returns a nonzero value.
29896 <pre>
29897 #define __STDC_WANT_LIB_EXT1__ 1
29899 errno_t tmpnam_s(char *s, rsize_t maxsize);
29900 </pre>
29901 Runtime-constraints
29903 s shall not be a null pointer. maxsize shall be less than or equal to RSIZE_MAX.
29904 maxsize shall be greater than the length of the generated file name string.
29907 The tmpnam_s function generates a string that is a valid file name and that is not the
29908 same as the name of an existing file.<sup><a href="#note387"><b>387)</b></a></sup> The function is potentially capable of generating
29909 TMP_MAX_S different strings, but any or all of them may already be in use by existing
29910 files and thus not be suitable return values. The lengths of these strings shall be less than
29911 the value of the L_tmpnam_s macro.
29913 The tmpnam_s function generates a different string each time it is called.
29915 It is assumed that s points to an array of at least maxsize characters. This array will be
29916 set to generated string, as specified below.
29920 <!--page 606 -->
29922 The implementation shall behave as if no library function except tmpnam calls the
29926 After a program obtains a file name using the tmpnam_s function and before the
29927 program creates a file with that name, the possibility exists that someone else may create
29928 a file with that same name. To avoid this race condition, the tmpfile_s function
29929 should be used instead of tmpnam_s when possible. One situation that requires the use
29930 of the tmpnam_s function is when the program needs to create a temporary directory
29931 rather than a temporary file.
29934 If no suitable string can be generated, or if there is a runtime-constraint violation, the
29935 tmpnam_s function writes a null character to s[0] (only if s is not null and maxsize
29936 is greater than zero) and returns a nonzero value.
29938 Otherwise, the tmpnam_s function writes the string in the array pointed to by s and
29939 returns zero.
29942 The value of the macro TMP_MAX_S shall be at least 25.
29945 <p><small><a name="note387" href="#note387">387)</a> Files created using strings generated by the tmpnam_s function are temporary only in the sense that
29946 their names should not collide with those generated by conventional naming rules for the
29947 implementation. It is still necessary to use the remove function to remove such files when their use
29948 is ended, and before program termination. Implementations should take care in choosing the patterns
29949 used for names returned by tmpnam_s. For example, making a thread id part of the names avoids the
29950 race condition and possible conflict when multiple programs run simultaneously by the same user
29951 generate the same temporary file names.
29952 </small>
29953 <p><small><a name="note388" href="#note388">388)</a> An implementation may have tmpnam call tmpnam_s (perhaps so there is only one naming
29954 convention for temporary files), but this is not required.
29955 </small>
29964 <pre>
29965 #define __STDC_WANT_LIB_EXT1__ 1
29967 errno_t fopen_s(FILE * restrict * restrict streamptr,
29968 const char * restrict filename,
29969 const char * restrict mode);
29970 </pre>
29971 Runtime-constraints
29973 None of streamptr, filename, or mode shall be a null pointer.
29975 If there is a runtime-constraint violation, fopen_s does not attempt to open a file.
29976 Furthermore, if streamptr is not a null pointer, fopen_s sets *streamptr to the
29977 null pointer.
29982 <!--page 607 -->
29985 The fopen_s function opens the file whose name is the string pointed to by
29986 filename, and associates a stream with it.
29988 The mode string shall be as described for fopen, with the addition that modes starting
29989 with the character 'w' or 'a' may be preceded by the character 'u', see below:
29990 uw truncate to zero length or create text file for writing, default
29991 <pre>
29992 permissions
29993 </pre>
29994 uwx create text file for writing, default permissions
29995 ua append; open or create text file for writing at end-of-file, default
29996 <pre>
29997 permissions
29998 </pre>
29999 uwb truncate to zero length or create binary file for writing, default
30000 <pre>
30001 permissions
30002 </pre>
30003 uwbx create binary file for writing, default permissions
30004 uab append; open or create binary file for writing at end-of-file, default
30005 <pre>
30006 permissions
30007 </pre>
30008 uw+ truncate to zero length or create text file for update, default
30009 <pre>
30010 permissions
30011 </pre>
30012 uw+x create text file for update, default permissions
30013 ua+ append; open or create text file for update, writing at end-of-file,
30014 <pre>
30015 default permissions
30016 </pre>
30017 uw+b or uwb+ truncate to zero length or create binary file for update, default
30018 <pre>
30019 permissions
30020 </pre>
30021 uw+bx or uwb+x create binary file for update, default permissions
30022 ua+b or uab+ append; open or create binary file for update, writing at end-of-file,
30023 <pre>
30024 default permissions
30025 </pre>
30027 Opening a file with exclusive mode ('x' as the last character in the mode argument)
30028 fails if the file already exists or cannot be created.
30030 To the extent that the underlying system supports the concepts, files opened for writing
30031 shall be opened with exclusive (also known as non-shared) access. If the file is being
30032 created, and the first character of the mode string is not 'u', to the extent that the
30033 underlying system supports it, the file shall have a file permission that prevents other
30034 users on the system from accessing the file. If the file is being created and first character
30035 of the mode string is 'u', then by the time the file has been closed, it shall have the
30038 If the file was opened successfully, then the pointer to FILE pointed to by streamptr
30039 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
30042 <!--page 608 -->
30043 to FILE pointed to by streamptr will be set to a null pointer.
30046 The fopen_s function returns zero if it opened the file. If it did not open the file or if
30047 there was a runtime-constraint violation, fopen_s returns a nonzero value.
30050 <p><small><a name="note389" href="#note389">389)</a> These are the same permissions that the file would have been created with by fopen.
30051 </small>
30057 <pre>
30058 #define __STDC_WANT_LIB_EXT1__ 1
30060 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
30061 const char * restrict filename,
30062 const char * restrict mode,
30063 FILE * restrict stream);
30064 </pre>
30065 Runtime-constraints
30067 None of newstreamptr, mode, and stream shall be a null pointer.
30069 If there is a runtime-constraint violation, freopen_s neither attempts to close any file
30070 associated with stream nor attempts to open a file. Furthermore, if newstreamptr is
30071 not a null pointer, fopen_s sets *newstreamptr to the null pointer.
30074 The freopen_s function opens the file whose name is the string pointed to by
30075 filename and associates the stream pointed to by stream with it. The mode
30076 argument has the same meaning as in the fopen_s function (including the mode's effect
30077 on exclusive access and file permissions).
30079 If filename is a null pointer, the freopen_s function attempts to change the mode of
30080 the stream to that specified by mode, as if the name of the file currently associated with
30081 the stream had been used. It is implementation-defined which changes of mode are
30082 permitted (if any), and under what circumstances.
30084 The freopen_s function first attempts to close any file that is associated with stream.
30085 Failure to close the file is ignored. The error and end-of-file indicators for the stream are
30086 cleared.
30088 If the file was opened successfully, then the pointer to FILE pointed to by
30089 newstreamptr will be set to the value of stream. Otherwise, the pointer to FILE
30090 pointed to by newstreamptr will be set to a null pointer.
30093 The freopen_s function returns zero if it opened the file. If it did not open the file or
30094 there was a runtime-constraint violation, freopen_s returns a nonzero value.
30095 <!--page 609 -->
30100 Unless explicitly stated otherwise, if the execution of a function described in this
30101 subclause causes copying to take place between objects that overlap, the objects take on
30102 unspecified values.
30108 <pre>
30109 #define __STDC_WANT_LIB_EXT1__ 1
30111 int fprintf_s(FILE * restrict stream,
30112 const char * restrict format, ...);
30113 </pre>
30114 Runtime-constraints
30116 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note390"><b>390)</b></a></sup> (modified or
30117 not by flags, field width, or precision) shall not appear in the string pointed to by
30118 format. Any argument to fprintf_s corresponding to a %s specifier shall not be a
30119 null pointer.
30121 If there is a runtime-constraint violation,<sup><a href="#note391"><b>391)</b></a></sup> the fprintf_s function does not attempt
30122 to produce further output, and it is unspecified to what extent fprintf_s produced
30123 output before discovering the runtime-constraint violation.
30126 The fprintf_s function is equivalent to the fprintf function except for the explicit
30127 runtime-constraints listed above.
30130 The fprintf_s function returns the number of characters transmitted, or a negative
30131 value if an output error, encoding error, or runtime-constraint violation occurred.
30136 <!--page 610 -->
30139 <p><small><a name="note390" href="#note390">390)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30140 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30141 format string was %%n.
30142 </small>
30143 <p><small><a name="note391" href="#note391">391)</a> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
30144 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
30145 constraint violation.
30146 </small>
30152 <pre>
30153 #define __STDC_WANT_LIB_EXT1__ 1
30155 int fscanf_s(FILE * restrict stream,
30156 const char * restrict format, ...);
30157 </pre>
30158 Runtime-constraints
30160 Neither stream nor format shall be a null pointer. Any argument indirected though in
30161 order to store converted input shall not be a null pointer.
30163 If there is a runtime-constraint violation,<sup><a href="#note392"><b>392)</b></a></sup> the fscanf_s function does not attempt to
30164 perform further input, and it is unspecified to what extent fscanf_s performed input
30165 before discovering the runtime-constraint violation.
30168 The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion
30169 specifiers apply to a pair of arguments (unless assignment suppression is indicated by a
30170 *). The first of these arguments is the same as for fscanf. That argument is
30171 immediately followed in the argument list by the second argument, which has type
30172 rsize_t and gives the number of elements in the array pointed to by the first argument
30173 of the pair. If the first argument points to a scalar object, it is considered to be an array of
30176 A matching failure occurs if the number of elements in a receiving object is insufficient to
30177 hold the converted input (including any trailing null character).
30180 The fscanf_s function returns the value of the macro EOF if an input failure occurs
30181 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30183 <!--page 611 -->
30184 fscanf_s function returns the number of input items assigned, which can be fewer than
30185 provided for, or even zero, in the event of an early matching failure.
30187 EXAMPLE 1 The call:
30188 <pre>
30189 #define __STDC_WANT_LIB_EXT1__ 1
30191 /* ... */
30192 int n, i; float x; char name[50];
30194 </pre>
30195 with the input line:
30196 <pre>
30197 25 54.32E-1 thompson
30198 </pre>
30199 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
30200 thompson\0.
30203 EXAMPLE 2 The call:
30204 <pre>
30205 #define __STDC_WANT_LIB_EXT1__ 1
30207 /* ... */
30208 int n; char s[5];
30209 n = fscanf_s(stdin, "%s", s, sizeof s);
30210 </pre>
30211 with the input line:
30212 <pre>
30213 hello
30214 </pre>
30215 will assign to n the value 0 since a matching failure occurred because the sequence hello\0 requires an
30216 array of six characters to store it.
30220 <p><small><a name="note392" href="#note392">392)</a> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
30221 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
30222 constraint violation.
30223 </small>
30224 <p><small><a name="note393" href="#note393">393)</a> If the format is known at translation time, an implementation may issue a diagnostic for any argument
30225 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
30226 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
30227 the format is not known at translation time. For example, an implementation may issue a diagnostic
30228 for each argument after format that has of type pointer to one of char, signed char,
30229 unsigned char, or void that is not followed by an argument of a type compatible with
30230 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
30231 using the hh length modifier, a length argument must follow the pointer argument. Another useful
30232 diagnostic could flag any non-pointer argument following format that did not have a type
30233 compatible with rsize_t.
30234 </small>
30240 <pre>
30241 #define __STDC_WANT_LIB_EXT1__ 1
30243 int printf_s(const char * restrict format, ...);
30244 </pre>
30245 Runtime-constraints
30247 format shall not be a null pointer. The %n specifier<sup><a href="#note394"><b>394)</b></a></sup> (modified or not by flags, field
30248 width, or precision) shall not appear in the string pointed to by format. Any argument
30249 to printf_s corresponding to a %s specifier shall not be a null pointer.
30251 If there is a runtime-constraint violation, the printf_s function does not attempt to
30252 produce further output, and it is unspecified to what extent printf_s produced output
30253 before discovering the runtime-constraint violation.
30256 <!--page 612 -->
30259 The printf_s function is equivalent to the printf function except for the explicit
30260 runtime-constraints listed above.
30263 The printf_s function returns the number of characters transmitted, or a negative
30264 value if an output error, encoding error, or runtime-constraint violation occurred.
30267 <p><small><a name="note394" href="#note394">394)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30268 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30269 format string was %%n.
30270 </small>
30276 <pre>
30277 #define __STDC_WANT_LIB_EXT1__ 1
30279 int scanf_s(const char * restrict format, ...);
30280 </pre>
30281 Runtime-constraints
30283 format shall not be a null pointer. Any argument indirected though in order to store
30284 converted input shall not be a null pointer.
30286 If there is a runtime-constraint violation, the scanf_s function does not attempt to
30287 perform further input, and it is unspecified to what extent scanf_s performed input
30288 before discovering the runtime-constraint violation.
30291 The scanf_s function is equivalent to fscanf_s with the argument stdin
30292 interposed before the arguments to scanf_s.
30295 The scanf_s function returns the value of the macro EOF if an input failure occurs
30296 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30297 scanf_s function returns the number of input items assigned, which can be fewer than
30298 provided for, or even zero, in the event of an early matching failure.
30304 <pre>
30305 #define __STDC_WANT_LIB_EXT1__ 1
30307 int snprintf_s(char * restrict s, rsize_t n,
30308 const char * restrict format, ...);
30309 </pre>
30310 Runtime-constraints
30312 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30313 than RSIZE_MAX. The %n specifier<sup><a href="#note395"><b>395)</b></a></sup> (modified or not by flags, field width, or
30314 precision) shall not appear in the string pointed to by format. Any argument to
30315 <!--page 613 -->
30316 snprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
30317 error shall occur.
30319 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30320 than zero and less than RSIZE_MAX, then the snprintf_s function sets s[0] to the
30321 null character.
30324 The snprintf_s function is equivalent to the snprintf function except for the
30325 explicit runtime-constraints listed above.
30327 The snprintf_s function, unlike sprintf_s, will truncate the result to fit within the
30328 array pointed to by s.
30331 The snprintf_s function returns the number of characters that would have been
30332 written had n been sufficiently large, not counting the terminating null character, or a
30333 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
30334 output has been completely written if and only if the returned value is nonnegative and
30335 less than n.
30338 <p><small><a name="note395" href="#note395">395)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30339 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30340 format string was %%n.
30341 </small>
30347 <pre>
30348 #define __STDC_WANT_LIB_EXT1__ 1
30350 int sprintf_s(char * restrict s, rsize_t n,
30351 const char * restrict format, ...);
30352 </pre>
30353 Runtime-constraints
30355 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30356 than RSIZE_MAX. The number of characters (including the trailing null) required for the
30357 result to be written to the array pointed to by s shall not be greater than n. The %n
30358 specifier<sup><a href="#note396"><b>396)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
30359 string pointed to by format. Any argument to sprintf_s corresponding to a %s
30360 specifier shall not be a null pointer. No encoding error shall occur.
30364 <!--page 614 -->
30366 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30367 than zero and less than RSIZE_MAX, then the sprintf_s function sets s[0] to the
30368 null character.
30371 The sprintf_s function is equivalent to the sprintf function except for the
30372 parameter n and the explicit runtime-constraints listed above.
30374 The sprintf_s function, unlike snprintf_s, treats a result too big for the array
30375 pointed to by s as a runtime-constraint violation.
30378 If no runtime-constraint violation occurred, the sprintf_s function returns the number
30379 of characters written in the array, not counting the terminating null character. If an
30380 encoding error occurred, sprintf_s returns a negative value. If any other runtime-
30381 constraint violation occurred, sprintf_s returns zero.
30384 <p><small><a name="note396" href="#note396">396)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30385 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30386 format string was %%n.
30387 </small>
30393 <pre>
30394 #define __STDC_WANT_LIB_EXT1__ 1
30396 int sscanf_s(const char * restrict s,
30397 const char * restrict format, ...);
30398 </pre>
30399 Runtime-constraints
30401 Neither s nor format shall be a null pointer. Any argument indirected though in order
30402 to store converted input shall not be a null pointer.
30404 If there is a runtime-constraint violation, the sscanf_s function does not attempt to
30405 perform further input, and it is unspecified to what extent sscanf_s performed input
30406 before discovering the runtime-constraint violation.
30409 The sscanf_s function is equivalent to fscanf_s, except that input is obtained from
30410 a string (specified by the argument s) rather than from a stream. Reaching the end of the
30411 string is equivalent to encountering end-of-file for the fscanf_s function. If copying
30412 takes place between objects that overlap, the objects take on unspecified values.
30415 The sscanf_s function returns the value of the macro EOF if an input failure occurs
30416 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30417 sscanf_s function returns the number of input items assigned, which can be fewer than
30418 provided for, or even zero, in the event of an early matching failure.
30419 <!--page 615 -->
30425 <pre>
30426 #define __STDC_WANT_LIB_EXT1__ 1
30429 int vfprintf_s(FILE * restrict stream,
30430 const char * restrict format,
30431 va_list arg);
30432 </pre>
30433 Runtime-constraints
30435 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note397"><b>397)</b></a></sup> (modified or
30436 not by flags, field width, or precision) shall not appear in the string pointed to by
30437 format. Any argument to vfprintf_s corresponding to a %s specifier shall not be a
30438 null pointer.
30440 If there is a runtime-constraint violation, the vfprintf_s function does not attempt to
30441 produce further output, and it is unspecified to what extent vfprintf_s produced
30442 output before discovering the runtime-constraint violation.
30445 The vfprintf_s function is equivalent to the vfprintf function except for the
30446 explicit runtime-constraints listed above.
30449 The vfprintf_s function returns the number of characters transmitted, or a negative
30450 value if an output error, encoding error, or runtime-constraint violation occurred.
30453 <p><small><a name="note397" href="#note397">397)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30454 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30455 format string was %%n.
30456 </small>
30462 <pre>
30463 #define __STDC_WANT_LIB_EXT1__ 1
30466 int vfscanf_s(FILE * restrict stream,
30467 const char * restrict format,
30468 va_list arg);
30469 </pre>
30474 <!--page 616 -->
30475 Runtime-constraints
30477 Neither stream nor format shall be a null pointer. Any argument indirected though in
30478 order to store converted input shall not be a null pointer.
30480 If there is a runtime-constraint violation, the vfscanf_s function does not attempt to
30481 perform further input, and it is unspecified to what extent vfscanf_s performed input
30482 before discovering the runtime-constraint violation.
30485 The vfscanf_s function is equivalent to fscanf_s, with the variable argument list
30486 replaced by arg, which shall have been initialized by the va_start macro (and
30487 possibly subsequent va_arg calls). The vfscanf_s function does not invoke the
30491 The vfscanf_s function returns the value of the macro EOF if an input failure occurs
30492 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30493 vfscanf_s function returns the number of input items assigned, which can be fewer
30494 than provided for, or even zero, in the event of an early matching failure.
30497 <p><small><a name="note398" href="#note398">398)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
30498 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
30499 indeterminate.
30500 </small>
30506 <pre>
30507 #define __STDC_WANT_LIB_EXT1__ 1
30510 int vprintf_s(const char * restrict format,
30511 va_list arg);
30512 </pre>
30513 Runtime-constraints
30515 format shall not be a null pointer. The %n specifier<sup><a href="#note399"><b>399)</b></a></sup> (modified or not by flags, field
30516 width, or precision) shall not appear in the string pointed to by format. Any argument
30517 to vprintf_s corresponding to a %s specifier shall not be a null pointer.
30519 If there is a runtime-constraint violation, the vprintf_s function does not attempt to
30520 produce further output, and it is unspecified to what extent vprintf_s produced output
30521 before discovering the runtime-constraint violation.
30523 <!--page 617 -->
30526 The vprintf_s function is equivalent to the vprintf function except for the explicit
30527 runtime-constraints listed above.
30530 The vprintf_s function returns the number of characters transmitted, or a negative
30531 value if an output error, encoding error, or runtime-constraint violation occurred.
30534 <p><small><a name="note399" href="#note399">399)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30535 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30536 format string was %%n.
30537 </small>
30543 <pre>
30544 #define __STDC_WANT_LIB_EXT1__ 1
30547 int vscanf_s(const char * restrict format,
30548 va_list arg);
30549 </pre>
30550 Runtime-constraints
30552 format shall not be a null pointer. Any argument indirected though in order to store
30553 converted input shall not be a null pointer.
30555 If there is a runtime-constraint violation, the vscanf_s function does not attempt to
30556 perform further input, and it is unspecified to what extent vscanf_s performed input
30557 before discovering the runtime-constraint violation.
30560 The vscanf_s function is equivalent to scanf_s, with the variable argument list
30561 replaced by arg, which shall have been initialized by the va_start macro (and
30562 possibly subsequent va_arg calls). The vscanf_s function does not invoke the
30566 The vscanf_s function returns the value of the macro EOF if an input failure occurs
30567 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30568 vscanf_s function returns the number of input items assigned, which can be fewer than
30569 provided for, or even zero, in the event of an early matching failure.
30574 <!--page 618 -->
30577 <p><small><a name="note400" href="#note400">400)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
30578 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
30579 indeterminate.
30580 </small>
30586 <pre>
30587 #define __STDC_WANT_LIB_EXT1__ 1
30590 int vsnprintf_s(char * restrict s, rsize_t n,
30591 const char * restrict format,
30592 va_list arg);
30593 </pre>
30594 Runtime-constraints
30596 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30597 than RSIZE_MAX. The %n specifier<sup><a href="#note401"><b>401)</b></a></sup> (modified or not by flags, field width, or
30598 precision) shall not appear in the string pointed to by format. Any argument to
30599 vsnprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
30600 error shall occur.
30602 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30603 than zero and less than RSIZE_MAX, then the vsnprintf_s function sets s[0] to the
30604 null character.
30607 The vsnprintf_s function is equivalent to the vsnprintf function except for the
30608 explicit runtime-constraints listed above.
30610 The vsnprintf_s function, unlike vsprintf_s, will truncate the result to fit within
30611 the array pointed to by s.
30614 The vsnprintf_s function returns the number of characters that would have been
30615 written had n been sufficiently large, not counting the terminating null character, or a
30616 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
30617 output has been completely written if and only if the returned value is nonnegative and
30618 less than n.
30623 <!--page 619 -->
30626 <p><small><a name="note401" href="#note401">401)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30627 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30628 format string was %%n.
30629 </small>
30635 <pre>
30636 #define __STDC_WANT_LIB_EXT1__ 1
30639 int vsprintf_s(char * restrict s, rsize_t n,
30640 const char * restrict format,
30641 va_list arg);
30642 </pre>
30643 Runtime-constraints
30645 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30646 than RSIZE_MAX. The number of characters (including the trailing null) required for the
30647 result to be written to the array pointed to by s shall not be greater than n. The %n
30648 specifier<sup><a href="#note402"><b>402)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
30649 string pointed to by format. Any argument to vsprintf_s corresponding to a %s
30650 specifier shall not be a null pointer. No encoding error shall occur.
30652 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30653 than zero and less than RSIZE_MAX, then the vsprintf_s function sets s[0] to the
30654 null character.
30657 The vsprintf_s function is equivalent to the vsprintf function except for the
30658 parameter n and the explicit runtime-constraints listed above.
30660 The vsprintf_s function, unlike vsnprintf_s, treats a result too big for the array
30661 pointed to by s as a runtime-constraint violation.
30664 If no runtime-constraint violation occurred, the vsprintf_s function returns the
30665 number of characters written in the array, not counting the terminating null character. If
30666 an encoding error occurred, vsprintf_s returns a negative value. If any other
30667 runtime-constraint violation occurred, vsprintf_s returns zero.
30672 <!--page 620 -->
30675 <p><small><a name="note402" href="#note402">402)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30676 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30677 format string was %%n.
30678 </small>
30684 <pre>
30685 #define __STDC_WANT_LIB_EXT1__ 1
30688 int vsscanf_s(const char * restrict s,
30689 const char * restrict format,
30690 va_list arg);
30691 </pre>
30692 Runtime-constraints
30694 Neither s nor format shall be a null pointer. Any argument indirected though in order
30695 to store converted input shall not be a null pointer.
30697 If there is a runtime-constraint violation, the vsscanf_s function does not attempt to
30698 perform further input, and it is unspecified to what extent vsscanf_s performed input
30699 before discovering the runtime-constraint violation.
30702 The vsscanf_s function is equivalent to sscanf_s, with the variable argument list
30703 replaced by arg, which shall have been initialized by the va_start macro (and
30704 possibly subsequent va_arg calls). The vsscanf_s function does not invoke the
30708 The vsscanf_s function returns the value of the macro EOF if an input failure occurs
30709 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30710 vscanf_s function returns the number of input items assigned, which can be fewer than
30711 provided for, or even zero, in the event of an early matching failure.
30714 <p><small><a name="note403" href="#note403">403)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
30715 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
30716 indeterminate.
30717 </small>
30726 <pre>
30727 #define __STDC_WANT_LIB_EXT1__ 1
30729 char *gets_s(char *s, rsize_t n);
30730 </pre>
30735 <!--page 621 -->
30736 Runtime-constraints
30738 s shall not be a null pointer. n shall neither be equal to zero nor be greater than
30739 RSIZE_MAX. A new-line character, end-of-file, or read error shall occur within reading
30742 If there is a runtime-constraint violation, s[0] is set to the null character, and characters
30743 are read and discarded from stdin until a new-line character is read, or end-of-file or a
30744 read error occurs.
30747 The gets_s function reads at most one less than the number of characters specified by n
30748 from the stream pointed to by stdin, into the array pointed to by s. No additional
30749 characters are read after a new-line character (which is discarded) or after end-of-file.
30750 The discarded new-line character does not count towards number of characters read. A
30751 null character is written immediately after the last character read into the array.
30753 If end-of-file is encountered and no characters have been read into the array, or if a read
30754 error occurs during the operation, then s[0] is set to the null character, and the other
30755 elements of s take unspecified values.
30758 The fgets function allows properly-written programs to safely process input lines too
30759 long to store in the result array. In general this requires that callers of fgets pay
30760 attention to the presence or absence of a new-line character in the result array. Consider
30761 using fgets (along with any needed processing based on new-line characters) instead of
30762 gets_s.
30765 The gets_s function returns s if successful. If there was a runtime-constraint violation,
30766 or if end-of-file is encountered and no characters have been read into the array, or if a
30767 read error occurs during the operation, then a null pointer is returned.
30772 <!--page 622 -->
30775 <p><small><a name="note404" href="#note404">404)</a> The gets_s function, unlike the historical gets function, makes it a runtime-constraint violation for
30776 a line of input to overflow the buffer to store it. Unlike the fgets function, gets_s maintains a
30777 one-to-one relationship between input lines and successful calls to gets_s. Programs that use gets
30778 expect such a relationship.
30779 </small>
30786 The types are
30787 <pre>
30788 errno_t
30789 </pre>
30790 which is type int; and
30791 <pre>
30792 rsize_t
30793 </pre>
30794 which is the type size_t; and
30795 <pre>
30796 constraint_handler_t
30797 </pre>
30798 which has the following definition
30799 <pre>
30800 typedef void (*constraint_handler_t)(
30801 const char * restrict msg,
30802 void * restrict ptr,
30803 errno_t error);
30804 </pre>
30810 <h5><a name="K.3.6.1.1" href="#K.3.6.1.1">K.3.6.1.1 The set_constraint_handler_s function</a></h5>
30813 <pre>
30814 #define __STDC_WANT_LIB_EXT1__ 1
30816 constraint_handler_t set_constraint_handler_s(
30817 constraint_handler_t handler);
30818 </pre>
30821 The set_constraint_handler_s function sets the runtime-constraint handler to
30822 be handler. The runtime-constraint handler is the function to be called when a library
30823 function detects a runtime-constraint violation. Only the most recent handler registered
30824 with set_constraint_handler_s is called when a runtime-constraint violation
30825 occurs.
30827 When the handler is called, it is passed the following arguments in the following order:
30828 <ol>
30829 <li> A pointer to a character string describing the runtime-constraint violation.
30830 <li> A null pointer or a pointer to an implementation defined object.
30831 <li> If the function calling the handler has a return type declared as errno_t, the
30832 return value of the function is passed. Otherwise, a positive value of type
30833 errno_t is passed.
30834 <!--page 623 -->
30835 </ol>
30837 The implementation has a default constraint handler that is used if no calls to the
30838 set_constraint_handler_s function have been made. The behavior of the
30839 default handler is implementation-defined, and it may cause the program to exit or abort.
30841 If the handler argument to set_constraint_handler_s is a null pointer, the
30842 implementation default handler becomes the current constraint handler.
30845 The set_constraint_handler_s function returns a pointer to the previously
30849 <p><small><a name="note405" href="#note405">405)</a> If the previous handler was registered by calling set_constraint_handler_s with a null
30850 pointer argument, a pointer to the implementation default handler is returned (not NULL).
30851 </small>
30857 <pre>
30858 #define __STDC_WANT_LIB_EXT1__ 1
30860 void abort_handler_s(
30861 const char * restrict msg,
30862 void * restrict ptr,
30863 errno_t error);
30864 </pre>
30867 A pointer to the abort_handler_s function shall be a suitable argument to the
30868 set_constraint_handler_s function.
30870 The abort_handler_s function writes a message on the standard error stream in an
30871 implementation-defined format. The message shall include the string pointed to by msg.
30872 The abort_handler_s function then calls the abort function.<sup><a href="#note406"><b>406)</b></a></sup>
30875 The abort_handler_s function does not return to its caller.
30880 <!--page 624 -->
30883 <p><small><a name="note406" href="#note406">406)</a> Many implementations invoke a debugger when the abort function is called.
30884 </small>
30890 <pre>
30891 #define __STDC_WANT_LIB_EXT1__ 1
30893 void ignore_handler_s(
30894 const char * restrict msg,
30895 void * restrict ptr,
30896 errno_t error);
30897 </pre>
30900 A pointer to the ignore_handler_s function shall be a suitable argument to the
30901 set_constraint_handler_s function.
30903 The ignore_handler_s function simply returns to its caller.<sup><a href="#note407"><b>407)</b></a></sup>
30906 The ignore_handler_s function returns no value.
30909 <p><small><a name="note407" href="#note407">407)</a> If the runtime-constraint handler is set to the ignore_handler_s function, any library function in
30910 which a runtime-constraint violation occurs will return to its caller. The caller can determine whether
30911 a runtime-constraint violation occurred based on the library function's specification (usually, the
30912 library function returns a nonzero errno_t).
30913 </small>
30922 <pre>
30923 #define __STDC_WANT_LIB_EXT1__ 1
30925 errno_t getenv_s(size_t * restrict len,
30926 char * restrict value, rsize_t maxsize,
30927 const char * restrict name);
30928 </pre>
30929 Runtime-constraints
30931 name shall not be a null pointer. maxsize shall neither equal zero nor be greater than
30932 RSIZE_MAX. If maxsize is not equal to zero, then value shall not be a null pointer.
30934 If there is a runtime-constraint violation, the integer pointed to by len is set to 0 (if len
30935 is not null), and the environment list is not searched.
30938 The getenv_s function searches an environment list, provided by the host environment,
30939 for a string that matches the string pointed to by name.
30942 <!--page 625 -->
30944 If that name is found then getenv_s performs the following actions. If len is not a
30945 null pointer, the length of the string associated with the matched list member is stored in
30946 the integer pointed to by len. If the length of the associated string is less than maxsize,
30947 then the associated string is copied to the array pointed to by value.
30949 If that name is not found then getenv_s performs the following actions. If len is not
30950 a null pointer, zero is stored in the integer pointed to by len. If maxsize is greater than
30951 zero, then value[0] is set to the null character.
30953 The set of environment names and the method for altering the environment list are
30954 implementation-defined. The getenv_s function need not avoid data races with other
30955 threads of execution that modify the environment list.<sup><a href="#note408"><b>408)</b></a></sup>
30958 The getenv_s function returns zero if the specified name is found and the associated
30959 string was successfully stored in value. Otherwise, a nonzero value is returned.
30962 <p><small><a name="note408" href="#note408">408)</a> Many implementations provide non-standard functions that modify the environment list.
30963 </small>
30968 These utilities make use of a comparison function to search or sort arrays of unspecified
30969 type. Where an argument declared as size_t nmemb specifies the length of the array
30970 for a function, if nmemb has the value zero on a call to that function, then the comparison
30971 function is not called, a search finds no matching element, sorting performs no
30972 rearrangement, and the pointer to the array may be null.
30974 The implementation shall ensure that the second argument of the comparison function
30975 (when called from bsearch_s), or both arguments (when called from qsort_s), are
30976 pointers to elements of the array.<sup><a href="#note409"><b>409)</b></a></sup> The first argument when called from bsearch_s
30977 shall equal key.
30979 The comparison function shall not alter the contents of either the array or search key. The
30980 implementation may reorder elements of the array between calls to the comparison
30981 function, but shall not otherwise alter the contents of any individual element.
30983 When the same objects (consisting of size bytes, irrespective of their current positions
30984 in the array) are passed more than once to the comparison function, the results shall be
30985 consistent with one another. That is, for qsort_s they shall define a total ordering on
30986 the array, and for bsearch_s the same object shall always compare the same way with
30987 the key.
30989 <!--page 626 -->
30991 A sequence point occurs immediately before and immediately after each call to the
30992 comparison function, and also between any call to the comparison function and any
30993 movement of the objects passed as arguments to that call.
30996 <p><small><a name="note409" href="#note409">409)</a> That is, if the value passed is p, then the following expressions are always valid and nonzero:
30998 <pre>
30999 ((char *)p - (char *)base) % size == 0
31000 (char *)p >= (char *)base
31001 (char *)p < (char *)base + nmemb * size
31002 </pre>
31003 </small>
31009 <pre>
31010 #define __STDC_WANT_LIB_EXT1__ 1
31012 void *bsearch_s(const void *key, const void *base,
31013 rsize_t nmemb, rsize_t size,
31014 int (*compar)(const void *k, const void *y,
31015 void *context),
31016 void *context);
31017 </pre>
31018 Runtime-constraints
31020 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
31021 zero, then none of key, base, or compar shall be a null pointer.
31023 If there is a runtime-constraint violation, the bsearch_s function does not search the
31024 array.
31027 The bsearch_s function searches an array of nmemb objects, the initial element of
31028 which is pointed to by base, for an element that matches the object pointed to by key.
31029 The size of each element of the array is specified by size.
31031 The comparison function pointed to by compar is called with three arguments. The first
31032 two point to the key object and to an array element, in that order. The function shall
31033 return an integer less than, equal to, or greater than zero if the key object is considered,
31034 respectively, to be less than, to match, or to be greater than the array element. The array
31035 shall consist of: all the elements that compare less than, all the elements that compare
31036 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note410"><b>410)</b></a></sup>
31037 The third argument to the comparison function is the context argument passed to
31038 bsearch_s. The sole use of context by bsearch_s is to pass it to the comparison
31044 <!--page 627 -->
31047 The bsearch_s function returns a pointer to a matching element of the array, or a null
31048 pointer if no match is found or there is a runtime-constraint violation. If two elements
31049 compare as equal, which element is matched is unspecified.
31052 <p><small><a name="note410" href="#note410">410)</a> In practice, this means that the entire array has been sorted according to the comparison function.
31053 </small>
31054 <p><small><a name="note411" href="#note411">411)</a> The context argument is for the use of the comparison function in performing its duties. For
31055 example, it might specify a collating sequence used by the comparison function.
31056 </small>
31062 <pre>
31063 #define __STDC_WANT_LIB_EXT1__ 1
31065 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
31066 int (*compar)(const void *x, const void *y,
31067 void *context),
31068 void *context);
31069 </pre>
31070 Runtime-constraints
31072 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
31073 zero, then neither base nor compar shall be a null pointer.
31075 If there is a runtime-constraint violation, the qsort_s function does not sort the array.
31078 The qsort_s function sorts an array of nmemb objects, the initial element of which is
31079 pointed to by base. The size of each object is specified by size.
31081 The contents of the array are sorted into ascending order according to a comparison
31082 function pointed to by compar, which is called with three arguments. The first two
31083 point to the objects being compared. The function shall return an integer less than, equal
31084 to, or greater than zero if the first argument is considered to be respectively less than,
31085 equal to, or greater than the second. The third argument to the comparison function is the
31086 context argument passed to qsort_s. The sole use of context by qsort_s is to
31089 If two elements compare as equal, their relative order in the resulting sorted array is
31090 unspecified.
31093 The qsort_s function returns zero if there was no runtime-constraint violation.
31094 Otherwise, a nonzero value is returned.
31099 <!--page 628 -->
31102 <p><small><a name="note412" href="#note412">412)</a> The context argument is for the use of the comparison function in performing its duties. For
31103 example, it might specify a collating sequence used by the comparison function.
31104 </small>
31107 <h5><a name="K.3.6.4" href="#K.3.6.4">K.3.6.4 Multibyte/wide character conversion functions</a></h5>
31109 The behavior of the multibyte character functions is affected by the LC_CTYPE category
31110 of the current locale. For a state-dependent encoding, each function is placed into its
31111 initial conversion state by a call for which its character pointer argument, s, is a null
31112 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
31113 state of the function to be altered as necessary. A call with s as a null pointer causes
31114 these functions to set the int pointed to by their status argument to a nonzero value if
31115 encodings have state dependency, and zero otherwise.<sup><a href="#note413"><b>413)</b></a></sup> Changing the LC_CTYPE
31116 category causes the conversion state of these functions to be indeterminate.
31119 <p><small><a name="note413" href="#note413">413)</a> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
31120 character codes, but are grouped with an adjacent multibyte character.
31121 </small>
31127 <pre>
31128 #define __STDC_WANT_LIB_EXT1__ 1
31130 errno_t wctomb_s(int * restrict status,
31131 char * restrict s,
31132 rsize_t smax,
31133 wchar_t wc);
31134 </pre>
31135 Runtime-constraints
31137 Let n denote the number of bytes needed to represent the multibyte character
31138 corresponding to the wide character given by wc (including any shift sequences).
31140 If s is not a null pointer, then smax shall not be less than n, and smax shall not be
31141 greater than RSIZE_MAX. If s is a null pointer, then smax shall equal zero.
31143 If there is a runtime-constraint violation, wctomb_s does not modify the int pointed to
31144 by status, and if s is not a null pointer, no more than smax elements in the array
31145 pointed to by s will be accessed.
31148 The wctomb_s function determines n and stores the multibyte character representation
31149 of wc in the array whose first element is pointed to by s (if s is not a null pointer). The
31150 number of characters stored never exceeds MB_CUR_MAX or smax. If wc is a null wide
31151 character, a null byte is stored, preceded by any shift sequence needed to restore the
31152 initial shift state, and the function is left in the initial conversion state.
31154 The implementation shall behave as if no library function calls the wctomb_s function.
31158 <!--page 629 -->
31160 If s is a null pointer, the wctomb_s function stores into the int pointed to by status a
31161 nonzero or zero value, if multibyte character encodings, respectively, do or do not have
31162 state-dependent encodings.
31164 If s is not a null pointer, the wctomb_s function stores into the int pointed to by
31165 status either n or -1 if wc, respectively, does or does not correspond to a valid
31166 multibyte character.
31168 In no case will the int pointed to by status be set to a value greater than the
31169 MB_CUR_MAX macro.
31172 The wctomb_s function returns zero if successful, and a nonzero value if there was a
31173 runtime-constraint violation or wc did not correspond to a valid multibyte character.
31176 <h5><a name="K.3.6.5" href="#K.3.6.5">K.3.6.5 Multibyte/wide string conversion functions</a></h5>
31178 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
31179 the current locale.
31185 <pre>
31187 errno_t mbstowcs_s(size_t * restrict retval,
31188 wchar_t * restrict dst, rsize_t dstmax,
31189 const char * restrict src, rsize_t len);
31190 </pre>
31191 Runtime-constraints
31193 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
31194 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
31195 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
31196 zero. If dst is not a null pointer and len is not less than dstmax, then a null character
31197 shall occur within the first dstmax multibyte characters of the array pointed to by src.
31199 If there is a runtime-constraint violation, then mbstowcs_s does the following. If
31200 retval is not a null pointer, then mbstowcs_s sets *retval to (size_t)(-1). If
31201 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
31202 then mbstowcs_s sets dst[0] to the null wide character.
31205 The mbstowcs_s function converts a sequence of multibyte characters that begins in
31206 the initial shift state from the array pointed to by src into a sequence of corresponding
31207 wide characters. If dst is not a null pointer, the converted characters are stored into the
31208 array pointed to by dst. Conversion continues up to and including a terminating null
31209 character, which is also stored. Conversion stops earlier in two cases: when a sequence of
31210 <!--page 630 -->
31211 bytes is encountered that does not form a valid multibyte character, or (if dst is not a
31212 null pointer) when len wide characters have been stored into the array pointed to by
31213 dst.<sup><a href="#note414"><b>414)</b></a></sup> If dst is not a null pointer and no null wide character was stored into the array
31214 pointed to by dst, then dst[len] is set to the null wide character. Each conversion
31215 takes place as if by a call to the mbrtowc function.
31217 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
31218 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
31219 the mbstowcs_s function stores the value (size_t)(-1) into *retval.
31220 Otherwise, the mbstowcs_s function stores into *retval the number of multibyte
31221 characters successfully converted, not including the terminating null character (if any).
31223 All elements following the terminating null wide character (if any) written by
31224 mbstowcs_s in the array of dstmax wide characters pointed to by dst take
31227 If copying takes place between objects that overlap, the objects take on unspecified
31228 values.
31231 The mbstowcs_s function returns zero if no runtime-constraint violation and no
31232 encoding error occurred. Otherwise, a nonzero value is returned.
31235 <p><small><a name="note414" href="#note414">414)</a> Thus, the value of len is ignored if dst is a null pointer.
31236 </small>
31237 <p><small><a name="note415" href="#note415">415)</a> This allows an implementation to attempt converting the multibyte string before discovering a
31238 terminating null character did not occur where required.
31239 </small>
31245 <pre>
31247 errno_t wcstombs_s(size_t * restrict retval,
31248 char * restrict dst, rsize_t dstmax,
31249 const wchar_t * restrict src, rsize_t len);
31250 </pre>
31251 Runtime-constraints
31253 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
31254 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
31255 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
31256 zero. If dst is not a null pointer and len is not less than dstmax, then the conversion
31257 shall have been stopped (see below) because a terminating null wide character was
31258 reached or because an encoding error occurred.
31263 <!--page 631 -->
31265 If there is a runtime-constraint violation, then wcstombs_s does the following. If
31266 retval is not a null pointer, then wcstombs_s sets *retval to (size_t)(-1). If
31267 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
31268 then wcstombs_s sets dst[0] to the null character.
31271 The wcstombs_s function converts a sequence of wide characters from the array
31272 pointed to by src into a sequence of corresponding multibyte characters that begins in
31273 the initial shift state. If dst is not a null pointer, the converted characters are then stored
31274 into the array pointed to by dst. Conversion continues up to and including a terminating
31275 null wide character, which is also stored. Conversion stops earlier in two cases:
31276 <ul>
31277 <li> when a wide character is reached that does not correspond to a valid multibyte
31278 character;
31279 <li> (if dst is not a null pointer) when the next multibyte character would exceed the
31280 limit of n total bytes to be stored into the array pointed to by dst. If the wide
31281 character being converted is the null wide character, then n is the lesser of len or
31282 dstmax. Otherwise, n is the lesser of len or dstmax-1.
31283 </ul>
31284 If the conversion stops without converting a null wide character and dst is not a null
31285 pointer, then a null character is stored into the array pointed to by dst immediately
31286 following any multibyte characters already stored. Each conversion takes place as if by a
31289 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
31290 wide character that does not correspond to a valid multibyte character, an encoding error
31291 occurs: the wcstombs_s function stores the value (size_t)(-1) into *retval.
31292 Otherwise, the wcstombs_s function stores into *retval the number of bytes in the
31293 resulting multibyte character sequence, not including the terminating null character (if
31294 any).
31296 All elements following the terminating null character (if any) written by wcstombs_s
31297 in the array of dstmax elements pointed to by dst take unspecified values when
31300 If copying takes place between objects that overlap, the objects take on unspecified
31301 values.
31304 <!--page 632 -->
31307 The wcstombs_s function returns zero if no runtime-constraint violation and no
31308 encoding error occurred. Otherwise, a nonzero value is returned.
31311 <p><small><a name="note416" href="#note416">416)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
31312 include those necessary to reach the initial shift state immediately before the null byte. However, if
31313 the conversion stops before a terminating null wide character has been reached, the result will be null
31314 terminated, but might not end in the initial shift state.
31315 </small>
31316 <p><small><a name="note417" href="#note417">417)</a> When len is not less than dstmax, the implementation might fill the array before discovering a
31317 runtime-constraint violation.
31318 </small>
31325 The types are
31326 <pre>
31327 errno_t
31328 </pre>
31329 which is type int; and
31330 <pre>
31331 rsize_t
31332 </pre>
31333 which is the type size_t.
31342 <pre>
31343 #define __STDC_WANT_LIB_EXT1__ 1
31345 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
31346 const void * restrict s2, rsize_t n);
31347 </pre>
31348 Runtime-constraints
31350 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31351 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
31352 objects that overlap.
31354 If there is a runtime-constraint violation, the memcpy_s function stores zeros in the first
31355 s1max characters of the object pointed to by s1 if s1 is not a null pointer and s1max is
31356 not greater than RSIZE_MAX.
31359 The memcpy_s function copies n characters from the object pointed to by s2 into the
31360 object pointed to by s1.
31363 The memcpy_s function returns zero if there was no runtime-constraint violation.
31364 Otherwise, a nonzero value is returned.
31365 <!--page 633 -->
31371 <pre>
31372 #define __STDC_WANT_LIB_EXT1__ 1
31374 errno_t memmove_s(void *s1, rsize_t s1max,
31375 const void *s2, rsize_t n);
31376 </pre>
31377 Runtime-constraints
31379 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31380 RSIZE_MAX. n shall not be greater than s1max.
31382 If there is a runtime-constraint violation, the memmove_s function stores zeros in the
31383 first s1max characters of the object pointed to by s1 if s1 is not a null pointer and
31384 s1max is not greater than RSIZE_MAX.
31387 The memmove_s function copies n characters from the object pointed to by s2 into the
31388 object pointed to by s1. This copying takes place as if the n characters from the object
31389 pointed to by s2 are first copied into a temporary array of n characters that does not
31390 overlap the objects pointed to by s1 or s2, and then the n characters from the temporary
31391 array are copied into the object pointed to by s1.
31394 The memmove_s function returns zero if there was no runtime-constraint violation.
31395 Otherwise, a nonzero value is returned.
31401 <pre>
31402 #define __STDC_WANT_LIB_EXT1__ 1
31404 errno_t strcpy_s(char * restrict s1,
31405 rsize_t s1max,
31406 const char * restrict s2);
31407 </pre>
31408 Runtime-constraints
31410 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
31411 s1max shall not equal zero. s1max shall be greater than strnlen_s(s2, s1max).
31412 Copying shall not take place between objects that overlap.
31414 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31415 greater than zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the
31416 null character.
31417 <!--page 634 -->
31420 The strcpy_s function copies the string pointed to by s2 (including the terminating
31421 null character) into the array pointed to by s1.
31423 All elements following the terminating null character (if any) written by strcpy_s in
31424 the array of s1max characters pointed to by s1 take unspecified values when
31428 The strcpy_s function returns zero<sup><a href="#note419"><b>419)</b></a></sup> if there was no runtime-constraint violation.
31429 Otherwise, a nonzero value is returned.
31432 <p><small><a name="note418" href="#note418">418)</a> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
31433 any of those characters are null. Such an approach might write a character to every element of s1
31434 before discovering that the first element should be set to the null character.
31435 </small>
31436 <p><small><a name="note419" href="#note419">419)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 fit
31437 within the array pointed to by s1 and that the result in s1 is null terminated.
31438 </small>
31444 <pre>
31445 #define __STDC_WANT_LIB_EXT1__ 1
31447 errno_t strncpy_s(char * restrict s1,
31448 rsize_t s1max,
31449 const char * restrict s2,
31450 rsize_t n);
31451 </pre>
31452 Runtime-constraints
31454 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31455 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
31456 shall be greater than strnlen_s(s2, s1max). Copying shall not take place between
31457 objects that overlap.
31459 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31460 greater than zero and not greater than RSIZE_MAX, then strncpy_s sets s1[0] to the
31461 null character.
31464 The strncpy_s function copies not more than n successive characters (characters that
31465 follow a null character are not copied) from the array pointed to by s2 to the array
31466 pointed to by s1. If no null character was copied from s2, then s1[n] is set to a null
31467 character.
31470 <!--page 635 -->
31472 All elements following the terminating null character (if any) written by strncpy_s in
31473 the array of s1max characters pointed to by s1 take unspecified values when
31477 The strncpy_s function returns zero<sup><a href="#note421"><b>421)</b></a></sup> if there was no runtime-constraint violation.
31478 Otherwise, a nonzero value is returned.
31480 EXAMPLE 1 The strncpy_s function can be used to copy a string without the danger that the result
31481 will not be null terminated or that characters will be written past the end of the destination array.
31482 <pre>
31483 #define __STDC_WANT_LIB_EXT1__ 1
31485 /* ... */
31487 char src2[7] = {'g', 'o', 'o', 'd', 'b', 'y', 'e'};
31489 int r1, r2, r3;
31493 </pre>
31494 The first call will assign to r1 the value zero and to dst1 the sequence hello\0.
31495 The second call will assign to r2 a nonzero value and to dst2 the sequence \0.
31496 The third call will assign to r3 the value zero and to dst3 the sequence good\0.
31500 <p><small><a name="note420" href="#note420">420)</a> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
31501 any of those characters are null. Such an approach might write a character to every element of s1
31502 before discovering that the first element should be set to the null character.
31503 </small>
31504 <p><small><a name="note421" href="#note421">421)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 fit
31505 within the array pointed to by s1 and that the result in s1 is null terminated.
31506 </small>
31515 <pre>
31516 #define __STDC_WANT_LIB_EXT1__ 1
31518 errno_t strcat_s(char * restrict s1,
31519 rsize_t s1max,
31520 const char * restrict s2);
31521 </pre>
31522 Runtime-constraints
31524 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
31525 strcat_s.
31530 <!--page 636 -->
31532 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
31533 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note422"><b>422)</b></a></sup> m shall be greater than
31534 strnlen_s(s2, m). Copying shall not take place between objects that overlap.
31536 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31537 greater than zero and not greater than RSIZE_MAX, then strcat_s sets s1[0] to the
31538 null character.
31541 The strcat_s function appends a copy of the string pointed to by s2 (including the
31542 terminating null character) to the end of the string pointed to by s1. The initial character
31543 from s2 overwrites the null character at the end of s1.
31545 All elements following the terminating null character (if any) written by strcat_s in
31546 the array of s1max characters pointed to by s1 take unspecified values when
31550 The strcat_s function returns zero<sup><a href="#note424"><b>424)</b></a></sup> if there was no runtime-constraint violation.
31551 Otherwise, a nonzero value is returned.
31554 <p><small><a name="note422" href="#note422">422)</a> Zero means that s1 was not null terminated upon entry to strcat_s.
31555 </small>
31556 <p><small><a name="note423" href="#note423">423)</a> This allows an implementation to append characters from s2 to s1 while simultaneously checking if
31557 any of those characters are null. Such an approach might write a character to every element of s1
31558 before discovering that the first element should be set to the null character.
31559 </small>
31560 <p><small><a name="note424" href="#note424">424)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 were
31561 appended to the string pointed to by s1 and that the result in s1 is null terminated.
31562 </small>
31568 <pre>
31569 #define __STDC_WANT_LIB_EXT1__ 1
31571 errno_t strncat_s(char * restrict s1,
31572 rsize_t s1max,
31573 const char * restrict s2,
31574 rsize_t n);
31575 </pre>
31576 Runtime-constraints
31578 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
31579 strncat_s.
31581 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31582 RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.<sup><a href="#note425"><b>425)</b></a></sup> If n is not less
31585 <!--page 637 -->
31586 than m, then m shall be greater than strnlen_s(s2, m). Copying shall not take
31587 place between objects that overlap.
31589 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31590 greater than zero and not greater than RSIZE_MAX, then strncat_s sets s1[0] to the
31591 null character.
31594 The strncat_s function appends not more than n successive characters (characters
31595 that follow a null character are not copied) from the array pointed to by s2 to the end of
31596 the string pointed to by s1. The initial character from s2 overwrites the null character at
31597 the end of s1. If no null character was copied from s2, then s1[s1max-m+n] is set to
31598 a null character.
31600 All elements following the terminating null character (if any) written by strncat_s in
31601 the array of s1max characters pointed to by s1 take unspecified values when
31605 The strncat_s function returns zero<sup><a href="#note427"><b>427)</b></a></sup> if there was no runtime-constraint violation.
31606 Otherwise, a nonzero value is returned.
31608 EXAMPLE 1 The strncat_s function can be used to copy a string without the danger that the result
31609 will not be null terminated or that characters will be written past the end of the destination array.
31610 <pre>
31611 #define __STDC_WANT_LIB_EXT1__ 1
31613 /* ... */
31619 int r1, r2, r3, r4;
31624 </pre>
31625 After the first call r1 will have the value zero and s1 will contain the sequence goodbye\0.
31629 <!--page 638 -->
31630 After the second call r2 will have the value zero and s2 will contain the sequence hello\0.
31631 After the third call r3 will have a nonzero value and s3 will contain the sequence \0.
31632 After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0.
31636 <p><small><a name="note425" href="#note425">425)</a> Zero means that s1 was not null terminated upon entry to strncat_s.
31637 </small>
31638 <p><small><a name="note426" href="#note426">426)</a> This allows an implementation to append characters from s2 to s1 while simultaneously checking if
31639 any of those characters are null. Such an approach might write a character to every element of s1
31640 before discovering that the first element should be set to the null character.
31641 </small>
31642 <p><small><a name="note427" href="#note427">427)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 were
31643 appended to the string pointed to by s1 and that the result in s1 is null terminated.
31644 </small>
31653 <pre>
31654 #define __STDC_WANT_LIB_EXT1__ 1
31656 char *strtok_s(char * restrict s1,
31657 rsize_t * restrict s1max,
31658 const char * restrict s2,
31659 char ** restrict ptr);
31660 </pre>
31661 Runtime-constraints
31663 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
31664 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
31665 The end of the token found shall occur within the first *s1max characters of s1 for the
31666 first call, and shall occur within the first *s1max characters of where searching resumes
31667 on subsequent calls.
31669 If there is a runtime-constraint violation, the strtok_s function does not indirect
31670 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
31673 A sequence of calls to the strtok_s function breaks the string pointed to by s1 into a
31674 sequence of tokens, each of which is delimited by a character from the string pointed to
31675 by s2. The fourth argument points to a caller-provided char pointer into which the
31676 strtok_s function stores information necessary for it to continue scanning the same
31677 string.
31679 The first call in a sequence has a non-null first argument and s1max points to an object
31680 whose value is the number of elements in the character array pointed to by the first
31681 argument. The first call stores an initial value in the object pointed to by ptr and
31682 updates the value pointed to by s1max to reflect the number of elements that remain in
31683 relation to ptr. Subsequent calls in the sequence have a null first argument and the
31684 objects pointed to by s1max and ptr are required to have the values stored by the
31685 previous call in the sequence, which are then updated. The separator string pointed to by
31686 s2 may be different from call to call.
31688 The first call in the sequence searches the string pointed to by s1 for the first character
31689 that is not contained in the current separator string pointed to by s2. If no such character
31690 is found, then there are no tokens in the string pointed to by s1 and the strtok_s
31691 function returns a null pointer. If such a character is found, it is the start of the first token.
31692 <!--page 639 -->
31694 The strtok_s function then searches from there for the first character in s1 that is
31695 contained in the current separator string. If no such character is found, the current token
31696 extends to the end of the string pointed to by s1, and subsequent searches in the same
31697 string for a token return a null pointer. If such a character is found, it is overwritten by a
31698 null character, which terminates the current token.
31700 In all cases, the strtok_s function stores sufficient information in the pointer pointed
31701 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
31702 value for ptr, shall start searching just past the element overwritten by a null character
31703 (if any).
31706 The strtok_s function returns a pointer to the first character of a token, or a null
31707 pointer if there is no token or there is a runtime-constraint violation.
31709 EXAMPLE
31710 <pre>
31711 #define __STDC_WANT_LIB_EXT1__ 1
31713 static char str1[] = "?a???b,,,#c";
31714 static char str2[] = "\t \t";
31715 char *t, *ptr1, *ptr2;
31716 rsize_t max1 = sizeof (str1);
31717 rsize_t max2 = sizeof (str2);
31723 </pre>
31733 <pre>
31734 #define __STDC_WANT_LIB_EXT1__ 1
31736 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
31737 </pre>
31738 Runtime-constraints
31740 s shall not be a null pointer. Neither smax nor n shall be greater than RSIZE_MAX. n
31741 shall not be greater than smax.
31743 If there is a runtime-constraint violation, then if s is not a null pointer and smax is not
31744 greater than RSIZE_MAX, the memset_s function stores the value of c (converted to an
31745 unsigned char) into each of the first smax characters of the object pointed to by s.
31746 <!--page 640 -->
31749 The memset_s function copies the value of c (converted to an unsigned char) into
31750 each of the first n characters of the object pointed to by s. Unlike memset, any call to
31751 the memset_s function shall be evaluated strictly according to the rules of the abstract
31752 machine as described in (<a href="#5.1.2.3">5.1.2.3</a>). That is, any call to the memset_s function shall
31753 assume that the memory indicated by s and n may be accessible in the future and thus
31754 must contain the values indicated by c.
31757 The memset_s function returns zero if there was no runtime-constraint violation.
31758 Otherwise, a nonzero value is returned.
31764 <pre>
31765 #define __STDC_WANT_LIB_EXT1__ 1
31767 errno_t strerror_s(char *s, rsize_t maxsize,
31768 errno_t errnum);
31769 </pre>
31770 Runtime-constraints
31772 s shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX.
31773 maxsize shall not equal zero.
31775 If there is a runtime-constraint violation, then the array (if any) pointed to by s is not
31776 modified.
31779 The strerror_s function maps the number in errnum to a locale-specific message
31780 string. Typically, the values for errnum come from errno, but strerror_s shall
31781 map any value of type int to a message.
31783 If the length of the desired string is less than maxsize, then the string is copied to the
31784 array pointed to by s.
31786 Otherwise, if maxsize is greater than zero, then maxsize-1 characters are copied
31787 from the string to the array pointed to by s and then s[maxsize-1] is set to the null
31792 The strerror_s function returns zero if the length of the desired string was less than
31793 maxsize and there was no runtime-constraint violation. Otherwise, the strerror_s
31794 function returns a nonzero value.
31795 <!--page 641 -->
31801 <pre>
31802 #define __STDC_WANT_LIB_EXT1__ 1
31804 size_t strerrorlen_s(errno_t errnum);
31805 </pre>
31808 The strerrorlen_s function calculates the length of the (untruncated) locale-specific
31809 message string that the strerror_s function maps to errnum.
31812 The strerrorlen_s function returns the number of characters (not including the null
31813 character) in the full message string.
31819 <pre>
31820 #define __STDC_WANT_LIB_EXT1__ 1
31822 size_t strnlen_s(const char *s, size_t maxsize);
31823 </pre>
31826 The strnlen_s function computes the length of the string pointed to by s.
31829 If s is a null pointer,<sup><a href="#note428"><b>428)</b></a></sup> then the strnlen_s function returns zero.
31831 Otherwise, the strnlen_s function returns the number of characters that precede the
31832 terminating null character. If there is no null character in the first maxsize characters of
31833 s then strnlen_s returns maxsize. At most the first maxsize characters of s shall
31834 be accessed by strnlen_s.
31839 <!--page 642 -->
31842 <p><small><a name="note428" href="#note428">428)</a> Note that the strnlen_s function has no runtime-constraints. This lack of runtime-constraints
31843 along with the values returned for a null pointer or an unterminated string argument make
31844 strnlen_s useful in algorithms that gracefully handle such exceptional data.
31845 </small>
31852 The types are
31853 <pre>
31854 errno_t
31855 </pre>
31856 which is type int; and
31857 <pre>
31858 rsize_t
31859 </pre>
31860 which is the type size_t.
31865 A broken-down time is normalized if the values of the members of the tm structure are in
31869 <p><small><a name="note429" href="#note429">429)</a> The normal ranges are defined in <a href="#7.27.1">7.27.1</a>.
31870 </small>
31875 Like the strftime function, the asctime_s and ctime_s functions do not return a
31876 pointer to a static object, and other library functions are permitted to call them.
31882 <pre>
31883 #define __STDC_WANT_LIB_EXT1__ 1
31885 errno_t asctime_s(char *s, rsize_t maxsize,
31886 const struct tm *timeptr);
31887 </pre>
31888 Runtime-constraints
31890 Neither s nor timeptr shall be a null pointer. maxsize shall not be less than 26 and
31891 shall not be greater than RSIZE_MAX. The broken-down time pointed to by timeptr
31892 shall be normalized. The calendar year represented by the broken-down time pointed to
31893 by timeptr shall not be less than calendar year 0 and shall not be greater than calendar
31894 year 9999.
31896 If there is a runtime-constraint violation, there is no attempt to convert the time, and
31897 s[0] is set to a null character if s is not a null pointer and maxsize is not zero and is
31898 not greater than RSIZE_MAX.
31901 The asctime_s function converts the normalized broken-down time in the structure
31902 pointed to by timeptr into a 26 character (including the null character) string in the
31905 <!--page 643 -->
31906 form
31907 <pre>
31909 </pre>
31910 The fields making up this string are (in order):
31911 <ol>
31913 following three character weekday names: Sun, Mon, Tue, Wed, Thu, Fri, and Sat.
31914 <li> The character space.
31916 three character month names: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct,
31917 Nov, and Dec.
31918 <li> The character space.
31920 "%2d".
31921 <li> The character space.
31923 "%.2d".
31924 <li> The character colon.
31926 "%.2d".
31927 <li> The character colon.
31929 "%.2d".
31930 <li> The character space.
31932 format "%4d".
31933 <li> The character new line.
31934 <li> The null character.
31935 </ol>
31937 The strftime function allows more flexible formatting and supports locale-specific
31938 behavior. If you do not require the exact form of the result string produced by the
31939 asctime_s function, consider using the strftime function instead.
31942 The asctime_s function returns zero if the time was successfully converted and stored
31943 into the array pointed to by s. Otherwise, it returns a nonzero value.
31944 <!--page 644 -->
31950 <pre>
31951 #define __STDC_WANT_LIB_EXT1__ 1
31953 errno_t ctime_s(char *s, rsize_t maxsize,
31954 const time_t *timer);
31955 </pre>
31956 Runtime-constraints
31958 Neither s nor timer shall be a null pointer. maxsize shall not be less than 26 and
31959 shall not be greater than RSIZE_MAX.
31961 If there is a runtime-constraint violation, s[0] is set to a null character if s is not a null
31962 pointer and maxsize is not equal zero and is not greater than RSIZE_MAX.
31965 The ctime_s function converts the calendar time pointed to by timer to local time in
31966 the form of a string. It is equivalent to
31967 <pre>
31968 asctime_s(s, maxsize, localtime_s(timer))
31969 </pre>
31971 The strftime function allows more flexible formatting and supports locale-specific
31972 behavior. If you do not require the exact form of the result string produced by the
31973 ctime_s function, consider using the strftime function instead.
31976 The ctime_s function returns zero if the time was successfully converted and stored
31977 into the array pointed to by s. Otherwise, it returns a nonzero value.
31983 <pre>
31984 #define __STDC_WANT_LIB_EXT1__ 1
31986 struct tm *gmtime_s(const time_t * restrict timer,
31987 struct tm * restrict result);
31988 </pre>
31989 Runtime-constraints
31991 Neither timer nor result shall be a null pointer.
31993 If there is a runtime-constraint violation, there is no attempt to convert the time.
31996 The gmtime_s function converts the calendar time pointed to by timer into a broken-
31997 down time, expressed as UTC. The broken-down time is stored in the structure pointed
31998 <!--page 645 -->
31999 to by result.
32002 The gmtime_s function returns result, or a null pointer if the specified time cannot
32003 be converted to UTC or there is a runtime-constraint violation.
32009 <pre>
32010 #define __STDC_WANT_LIB_EXT1__ 1
32012 struct tm *localtime_s(const time_t * restrict timer,
32013 struct tm * restrict result);
32014 </pre>
32015 Runtime-constraints
32017 Neither timer nor result shall be a null pointer.
32019 If there is a runtime-constraint violation, there is no attempt to convert the time.
32022 The localtime_s function converts the calendar time pointed to by timer into a
32023 broken-down time, expressed as local time. The broken-down time is stored in the
32024 structure pointed to by result.
32027 The localtime_s function returns result, or a null pointer if the specified time
32028 cannot be converted to local time or there is a runtime-constraint violation.
32031 <h4><a name="K.3.9" href="#K.3.9">K.3.9 Extended multibyte and wide character utilities <wchar.h></a></h4>
32035 The types are
32036 <pre>
32037 errno_t
32038 </pre>
32039 which is type int; and
32040 <pre>
32041 rsize_t
32042 </pre>
32043 which is the type size_t.
32045 Unless explicitly stated otherwise, if the execution of a function described in this
32046 subclause causes copying to take place between objects that overlap, the objects take on
32047 unspecified values.
32048 <!--page 646 -->
32051 <h5><a name="K.3.9.1" href="#K.3.9.1">K.3.9.1 Formatted wide character input/output functions</a></h5>
32057 <pre>
32058 #define __STDC_WANT_LIB_EXT1__ 1
32060 int fwprintf_s(FILE * restrict stream,
32061 const wchar_t * restrict format, ...);
32062 </pre>
32063 Runtime-constraints
32065 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note430"><b>430)</b></a></sup> (modified or
32066 not by flags, field width, or precision) shall not appear in the wide string pointed to by
32067 format. Any argument to fwprintf_s corresponding to a %s specifier shall not be a
32068 null pointer.
32070 If there is a runtime-constraint violation, the fwprintf_s function does not attempt to
32071 produce further output, and it is unspecified to what extent fwprintf_s produced
32072 output before discovering the runtime-constraint violation.
32075 The fwprintf_s function is equivalent to the fwprintf function except for the
32076 explicit runtime-constraints listed above.
32079 The fwprintf_s function returns the number of wide characters transmitted, or a
32080 negative value if an output error, encoding error, or runtime-constraint violation occurred.
32083 <p><small><a name="note430" href="#note430">430)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32084 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32085 example, if the entire format string was L"%%n".
32086 </small>
32092 <pre>
32093 #define __STDC_WANT_LIB_EXT1__ 1
32096 int fwscanf_s(FILE * restrict stream,
32097 const wchar_t * restrict format, ...);
32098 </pre>
32099 Runtime-constraints
32101 Neither stream nor format shall be a null pointer. Any argument indirected though in
32102 order to store converted input shall not be a null pointer.
32105 <!--page 647 -->
32107 If there is a runtime-constraint violation, the fwscanf_s function does not attempt to
32108 perform further input, and it is unspecified to what extent fwscanf_s performed input
32109 before discovering the runtime-constraint violation.
32112 The fwscanf_s function is equivalent to fwscanf except that the c, s, and [
32113 conversion specifiers apply to a pair of arguments (unless assignment suppression is
32114 indicated by a *). The first of these arguments is the same as for fwscanf. That
32115 argument is immediately followed in the argument list by the second argument, which has
32116 type size_t and gives the number of elements in the array pointed to by the first
32117 argument of the pair. If the first argument points to a scalar object, it is considered to be
32120 A matching failure occurs if the number of elements in a receiving object is insufficient to
32121 hold the converted input (including any trailing null character).
32124 The fwscanf_s function returns the value of the macro EOF if an input failure occurs
32125 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32126 fwscanf_s function returns the number of input items assigned, which can be fewer
32127 than provided for, or even zero, in the event of an early matching failure.
32130 <p><small><a name="note431" href="#note431">431)</a> If the format is known at translation time, an implementation may issue a diagnostic for any argument
32131 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
32132 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
32133 the format is not known at translation time. For example, an implementation may issue a diagnostic
32134 for each argument after format that has of type pointer to one of char, signed char,
32135 unsigned char, or void that is not followed by an argument of a type compatible with
32136 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
32137 using the hh length modifier, a length argument must follow the pointer argument. Another useful
32138 diagnostic could flag any non-pointer argument following format that did not have a type
32139 compatible with rsize_t.
32140 </small>
32146 <pre>
32147 #define __STDC_WANT_LIB_EXT1__ 1
32149 int snwprintf_s(wchar_t * restrict s,
32150 rsize_t n,
32151 const wchar_t * restrict format, ...);
32152 </pre>
32153 Runtime-constraints
32155 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
32156 than RSIZE_MAX. The %n specifier<sup><a href="#note432"><b>432)</b></a></sup> (modified or not by flags, field width, or
32158 <!--page 648 -->
32159 precision) shall not appear in the wide string pointed to by format. Any argument to
32160 snwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
32161 error shall occur.
32163 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
32164 than zero and less than RSIZE_MAX, then the snwprintf_s function sets s[0] to the
32165 null wide character.
32168 The snwprintf_s function is equivalent to the swprintf function except for the
32169 explicit runtime-constraints listed above.
32171 The snwprintf_s function, unlike swprintf_s, will truncate the result to fit within
32172 the array pointed to by s.
32175 The snwprintf_s function returns the number of wide characters that would have
32176 been written had n been sufficiently large, not counting the terminating wide null
32177 character, or a negative value if a runtime-constraint violation occurred. Thus, the null-
32178 terminated output has been completely written if and only if the returned value is
32179 nonnegative and less than n.
32182 <p><small><a name="note432" href="#note432">432)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32183 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32184 example, if the entire format string was L"%%n".
32185 </small>
32191 <pre>
32192 #define __STDC_WANT_LIB_EXT1__ 1
32194 int swprintf_s(wchar_t * restrict s, rsize_t n,
32195 const wchar_t * restrict format, ...);
32196 </pre>
32197 Runtime-constraints
32199 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
32200 than RSIZE_MAX. The number of wide characters (including the trailing null) required
32201 for the result to be written to the array pointed to by s shall not be greater than n. The %n
32202 specifier<sup><a href="#note433"><b>433)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
32203 wide string pointed to by format. Any argument to swprintf_s corresponding to a
32204 %s specifier shall not be a null pointer. No encoding error shall occur.
32207 <!--page 649 -->
32209 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
32210 than zero and less than RSIZE_MAX, then the swprintf_s function sets s[0] to the
32211 null wide character.
32214 The swprintf_s function is equivalent to the swprintf function except for the
32215 explicit runtime-constraints listed above.
32217 The swprintf_s function, unlike snwprintf_s, treats a result too big for the array
32218 pointed to by s as a runtime-constraint violation.
32221 If no runtime-constraint violation occurred, the swprintf_s function returns the
32222 number of wide characters written in the array, not counting the terminating null wide
32223 character. If an encoding error occurred or if n or more wide characters are requested to
32224 be written, swprintf_s returns a negative value. If any other runtime-constraint
32225 violation occurred, swprintf_s returns zero.
32228 <p><small><a name="note433" href="#note433">433)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32229 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32230 example, if the entire format string was L"%%n".
32231 </small>
32237 <pre>
32238 #define __STDC_WANT_LIB_EXT1__ 1
32240 int swscanf_s(const wchar_t * restrict s,
32241 const wchar_t * restrict format, ...);
32242 </pre>
32243 Runtime-constraints
32245 Neither s nor format shall be a null pointer. Any argument indirected though in order
32246 to store converted input shall not be a null pointer.
32248 If there is a runtime-constraint violation, the swscanf_s function does not attempt to
32249 perform further input, and it is unspecified to what extent swscanf_s performed input
32250 before discovering the runtime-constraint violation.
32253 The swscanf_s function is equivalent to fwscanf_s, except that the argument s
32254 specifies a wide string from which the input is to be obtained, rather than from a stream.
32255 Reaching the end of the wide string is equivalent to encountering end-of-file for the
32256 fwscanf_s function.
32259 The swscanf_s function returns the value of the macro EOF if an input failure occurs
32260 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32261 swscanf_s function returns the number of input items assigned, which can be fewer
32262 than provided for, or even zero, in the event of an early matching failure.
32263 <!--page 650 -->
32269 <pre>
32270 #define __STDC_WANT_LIB_EXT1__ 1
32274 int vfwprintf_s(FILE * restrict stream,
32275 const wchar_t * restrict format,
32276 va_list arg);
32277 </pre>
32278 Runtime-constraints
32280 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note434"><b>434)</b></a></sup> (modified or
32281 not by flags, field width, or precision) shall not appear in the wide string pointed to by
32282 format. Any argument to vfwprintf_s corresponding to a %s specifier shall not be
32283 a null pointer.
32285 If there is a runtime-constraint violation, the vfwprintf_s function does not attempt
32286 to produce further output, and it is unspecified to what extent vfwprintf_s produced
32287 output before discovering the runtime-constraint violation.
32290 The vfwprintf_s function is equivalent to the vfwprintf function except for the
32291 explicit runtime-constraints listed above.
32294 The vfwprintf_s function returns the number of wide characters transmitted, or a
32295 negative value if an output error, encoding error, or runtime-constraint violation occurred.
32298 <p><small><a name="note434" href="#note434">434)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32299 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32300 example, if the entire format string was L"%%n".
32301 </small>
32307 <pre>
32308 #define __STDC_WANT_LIB_EXT1__ 1
32312 int vfwscanf_s(FILE * restrict stream,
32313 const wchar_t * restrict format, va_list arg);
32314 </pre>
32318 <!--page 651 -->
32319 Runtime-constraints
32321 Neither stream nor format shall be a null pointer. Any argument indirected though in
32322 order to store converted input shall not be a null pointer.
32324 If there is a runtime-constraint violation, the vfwscanf_s function does not attempt to
32325 perform further input, and it is unspecified to what extent vfwscanf_s performed input
32326 before discovering the runtime-constraint violation.
32329 The vfwscanf_s function is equivalent to fwscanf_s, with the variable argument
32330 list replaced by arg, which shall have been initialized by the va_start macro (and
32331 possibly subsequent va_arg calls). The vfwscanf_s function does not invoke the
32335 The vfwscanf_s function returns the value of the macro EOF if an input failure occurs
32336 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32337 vfwscanf_s function returns the number of input items assigned, which can be fewer
32338 than provided for, or even zero, in the event of an early matching failure.
32341 <p><small><a name="note435" href="#note435">435)</a> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
32342 value of arg after the return is indeterminate.
32343 </small>
32349 <pre>
32350 #define __STDC_WANT_LIB_EXT1__ 1
32353 int vsnwprintf_s(wchar_t * restrict s,
32354 rsize_t n,
32355 const wchar_t * restrict format,
32356 va_list arg);
32357 </pre>
32358 Runtime-constraints
32360 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
32361 than RSIZE_MAX. The %n specifier<sup><a href="#note436"><b>436)</b></a></sup> (modified or not by flags, field width, or
32362 precision) shall not appear in the wide string pointed to by format. Any argument to
32363 vsnwprintf_s corresponding to a %s specifier shall not be a null pointer. No
32364 encoding error shall occur.
32366 <!--page 652 -->
32368 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
32369 than zero and less than RSIZE_MAX, then the vsnwprintf_s function sets s[0] to
32370 the null wide character.
32373 The vsnwprintf_s function is equivalent to the vswprintf function except for the
32374 explicit runtime-constraints listed above.
32376 The vsnwprintf_s function, unlike vswprintf_s, will truncate the result to fit
32377 within the array pointed to by s.
32380 The vsnwprintf_s function returns the number of wide characters that would have
32381 been written had n been sufficiently large, not counting the terminating null character, or
32382 a negative value if a runtime-constraint violation occurred. Thus, the null-terminated
32383 output has been completely written if and only if the returned value is nonnegative and
32384 less than n.
32387 <p><small><a name="note436" href="#note436">436)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32388 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32389 example, if the entire format string was L"%%n".
32390 </small>
32396 <pre>
32397 #define __STDC_WANT_LIB_EXT1__ 1
32400 int vswprintf_s(wchar_t * restrict s,
32401 rsize_t n,
32402 const wchar_t * restrict format,
32403 va_list arg);
32404 </pre>
32405 Runtime-constraints
32407 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
32408 than RSIZE_MAX. The number of wide characters (including the trailing null) required
32409 for the result to be written to the array pointed to by s shall not be greater than n. The %n
32410 specifier<sup><a href="#note437"><b>437)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
32411 wide string pointed to by format. Any argument to vswprintf_s corresponding to a
32412 %s specifier shall not be a null pointer. No encoding error shall occur.
32414 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
32415 than zero and less than RSIZE_MAX, then the vswprintf_s function sets s[0] to the
32416 null wide character.
32418 <!--page 653 -->
32421 The vswprintf_s function is equivalent to the vswprintf function except for the
32422 explicit runtime-constraints listed above.
32424 The vswprintf_s function, unlike vsnwprintf_s, treats a result too big for the
32425 array pointed to by s as a runtime-constraint violation.
32428 If no runtime-constraint violation occurred, the vswprintf_s function returns the
32429 number of wide characters written in the array, not counting the terminating null wide
32430 character. If an encoding error occurred or if n or more wide characters are requested to
32431 be written, vswprintf_s returns a negative value. If any other runtime-constraint
32432 violation occurred, vswprintf_s returns zero.
32435 <p><small><a name="note437" href="#note437">437)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32436 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32437 example, if the entire format string was L"%%n".
32438 </small>
32444 <pre>
32445 #define __STDC_WANT_LIB_EXT1__ 1
32448 int vswscanf_s(const wchar_t * restrict s,
32449 const wchar_t * restrict format,
32450 va_list arg);
32451 </pre>
32452 Runtime-constraints
32454 Neither s nor format shall be a null pointer. Any argument indirected though in order
32455 to store converted input shall not be a null pointer.
32457 If there is a runtime-constraint violation, the vswscanf_s function does not attempt to
32458 perform further input, and it is unspecified to what extent vswscanf_s performed input
32459 before discovering the runtime-constraint violation.
32462 The vswscanf_s function is equivalent to swscanf_s, with the variable argument
32463 list replaced by arg, which shall have been initialized by the va_start macro (and
32464 possibly subsequent va_arg calls). The vswscanf_s function does not invoke the
32470 <!--page 654 -->
32473 The vswscanf_s function returns the value of the macro EOF if an input failure occurs
32474 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32475 vswscanf_s function returns the number of input items assigned, which can be fewer
32476 than provided for, or even zero, in the event of an early matching failure.
32479 <p><small><a name="note438" href="#note438">438)</a> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
32480 value of arg after the return is indeterminate.
32481 </small>
32487 <pre>
32488 #define __STDC_WANT_LIB_EXT1__ 1
32491 int vwprintf_s(const wchar_t * restrict format,
32492 va_list arg);
32493 </pre>
32494 Runtime-constraints
32496 format shall not be a null pointer. The %n specifier<sup><a href="#note439"><b>439)</b></a></sup> (modified or not by flags, field
32497 width, or precision) shall not appear in the wide string pointed to by format. Any
32498 argument to vwprintf_s corresponding to a %s specifier shall not be a null pointer.
32500 If there is a runtime-constraint violation, the vwprintf_s function does not attempt to
32501 produce further output, and it is unspecified to what extent vwprintf_s produced
32502 output before discovering the runtime-constraint violation.
32505 The vwprintf_s function is equivalent to the vwprintf function except for the
32506 explicit runtime-constraints listed above.
32509 The vwprintf_s function returns the number of wide characters transmitted, or a
32510 negative value if an output error, encoding error, or runtime-constraint violation occurred.
32515 <!--page 655 -->
32518 <p><small><a name="note439" href="#note439">439)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32519 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32520 example, if the entire format string was L"%%n".
32521 </small>
32527 <pre>
32528 #define __STDC_WANT_LIB_EXT1__ 1
32531 int vwscanf_s(const wchar_t * restrict format,
32532 va_list arg);
32533 </pre>
32534 Runtime-constraints
32536 format shall not be a null pointer. Any argument indirected though in order to store
32537 converted input shall not be a null pointer.
32539 If there is a runtime-constraint violation, the vwscanf_s function does not attempt to
32540 perform further input, and it is unspecified to what extent vwscanf_s performed input
32541 before discovering the runtime-constraint violation.
32544 The vwscanf_s function is equivalent to wscanf_s, with the variable argument list
32545 replaced by arg, which shall have been initialized by the va_start macro (and
32546 possibly subsequent va_arg calls). The vwscanf_s function does not invoke the
32550 The vwscanf_s function returns the value of the macro EOF if an input failure occurs
32551 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32552 vwscanf_s function returns the number of input items assigned, which can be fewer
32553 than provided for, or even zero, in the event of an early matching failure.
32556 <p><small><a name="note440" href="#note440">440)</a> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
32557 value of arg after the return is indeterminate.
32558 </small>
32564 <pre>
32565 #define __STDC_WANT_LIB_EXT1__ 1
32567 int wprintf_s(const wchar_t * restrict format, ...);
32568 </pre>
32569 Runtime-constraints
32571 format shall not be a null pointer. The %n specifier<sup><a href="#note441"><b>441)</b></a></sup> (modified or not by flags, field
32573 <!--page 656 -->
32574 width, or precision) shall not appear in the wide string pointed to by format. Any
32575 argument to wprintf_s corresponding to a %s specifier shall not be a null pointer.
32577 If there is a runtime-constraint violation, the wprintf_s function does not attempt to
32578 produce further output, and it is unspecified to what extent wprintf_s produced output
32579 before discovering the runtime-constraint violation.
32582 The wprintf_s function is equivalent to the wprintf function except for the explicit
32583 runtime-constraints listed above.
32586 The wprintf_s function returns the number of wide characters transmitted, or a
32587 negative value if an output error, encoding error, or runtime-constraint violation occurred.
32590 <p><small><a name="note441" href="#note441">441)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32591 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32592 example, if the entire format string was L"%%n".
32593 </small>
32599 <pre>
32600 #define __STDC_WANT_LIB_EXT1__ 1
32602 int wscanf_s(const wchar_t * restrict format, ...);
32603 </pre>
32604 Runtime-constraints
32606 format shall not be a null pointer. Any argument indirected though in order to store
32607 converted input shall not be a null pointer.
32609 If there is a runtime-constraint violation, the wscanf_s function does not attempt to
32610 perform further input, and it is unspecified to what extent wscanf_s performed input
32611 before discovering the runtime-constraint violation.
32614 The wscanf_s function is equivalent to fwscanf_s with the argument stdin
32615 interposed before the arguments to wscanf_s.
32618 The wscanf_s function returns the value of the macro EOF if an input failure occurs
32619 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32620 wscanf_s function returns the number of input items assigned, which can be fewer than
32621 provided for, or even zero, in the event of an early matching failure.
32622 <!--page 657 -->
32634 <pre>
32635 #define __STDC_WANT_LIB_EXT1__ 1
32637 errno_t wcscpy_s(wchar_t * restrict s1,
32638 rsize_t s1max,
32639 const wchar_t * restrict s2);
32640 </pre>
32641 Runtime-constraints
32643 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
32644 s1max shall not equal zero. s1max shall be greater than wcsnlen_s(s2, s1max).
32645 Copying shall not take place between objects that overlap.
32647 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32648 greater than zero and not greater than RSIZE_MAX, then wcscpy_s sets s1[0] to the
32649 null wide character.
32652 The wcscpy_s function copies the wide string pointed to by s2 (including the
32653 terminating null wide character) into the array pointed to by s1.
32655 All elements following the terminating null wide character (if any) written by
32656 wcscpy_s in the array of s1max wide characters pointed to by s1 take unspecified
32660 The wcscpy_s function returns zero<sup><a href="#note443"><b>443)</b></a></sup> if there was no runtime-constraint violation.
32661 Otherwise, a nonzero value is returned.
32666 <!--page 658 -->
32669 <p><small><a name="note442" href="#note442">442)</a> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
32670 if any of those wide characters are null. Such an approach might write a wide character to every
32671 element of s1 before discovering that the first element should be set to the null wide character.
32672 </small>
32673 <p><small><a name="note443" href="#note443">443)</a> A zero return value implies that all of the requested wide characters from the string pointed to by s2
32674 fit within the array pointed to by s1 and that the result in s1 is null terminated.
32675 </small>
32681 <pre>
32682 #define __STDC_WANT_LIB_EXT1__ 1
32684 errno_t wcsncpy_s(wchar_t * restrict s1,
32685 rsize_t s1max,
32686 const wchar_t * restrict s2,
32687 rsize_t n);
32688 </pre>
32689 Runtime-constraints
32691 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32692 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
32693 shall be greater than wcsnlen_s(s2, s1max). Copying shall not take place between
32694 objects that overlap.
32696 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32697 greater than zero and not greater than RSIZE_MAX, then wcsncpy_s sets s1[0] to the
32698 null wide character.
32701 The wcsncpy_s function copies not more than n successive wide characters (wide
32702 characters that follow a null wide character are not copied) from the array pointed to by
32703 s2 to the array pointed to by s1. If no null wide character was copied from s2, then
32704 s1[n] is set to a null wide character.
32706 All elements following the terminating null wide character (if any) written by
32707 wcsncpy_s in the array of s1max wide characters pointed to by s1 take unspecified
32711 The wcsncpy_s function returns zero<sup><a href="#note445"><b>445)</b></a></sup> if there was no runtime-constraint violation.
32712 Otherwise, a nonzero value is returned.
32714 EXAMPLE 1 The wcsncpy_s function can be used to copy a wide string without the danger that the
32715 result will not be null terminated or that wide characters will be written past the end of the destination
32716 array.
32721 <!--page 659 -->
32722 <pre>
32723 #define __STDC_WANT_LIB_EXT1__ 1
32725 /* ... */
32727 wchar_t src2[7] = {L'g', L'o', L'o', L'd', L'b', L'y', L'e'};
32729 int r1, r2, r3;
32733 </pre>
32734 The first call will assign to r1 the value zero and to dst1 the sequence of wide characters hello\0.
32735 The second call will assign to r2 a nonzero value and to dst2 the sequence of wide characters \0.
32736 The third call will assign to r3 the value zero and to dst3 the sequence of wide characters good\0.
32740 <p><small><a name="note444" href="#note444">444)</a> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
32741 if any of those wide characters are null. Such an approach might write a wide character to every
32742 element of s1 before discovering that the first element should be set to the null wide character.
32743 </small>
32744 <p><small><a name="note445" href="#note445">445)</a> A zero return value implies that all of the requested wide characters from the string pointed to by s2
32745 fit within the array pointed to by s1 and that the result in s1 is null terminated.
32746 </small>
32752 <pre>
32753 #define __STDC_WANT_LIB_EXT1__ 1
32755 errno_t wmemcpy_s(wchar_t * restrict s1,
32756 rsize_t s1max,
32757 const wchar_t * restrict s2,
32758 rsize_t n);
32759 </pre>
32760 Runtime-constraints
32762 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32763 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
32764 objects that overlap.
32766 If there is a runtime-constraint violation, the wmemcpy_s function stores zeros in the
32767 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
32768 s1max is not greater than RSIZE_MAX.
32771 The wmemcpy_s function copies n successive wide characters from the object pointed
32772 to by s2 into the object pointed to by s1.
32775 The wmemcpy_s function returns zero if there was no runtime-constraint violation.
32776 Otherwise, a nonzero value is returned.
32777 <!--page 660 -->
32783 <pre>
32784 #define __STDC_WANT_LIB_EXT1__ 1
32786 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
32787 const wchar_t *s2, rsize_t n);
32788 </pre>
32789 Runtime-constraints
32791 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32792 RSIZE_MAX. n shall not be greater than s1max.
32794 If there is a runtime-constraint violation, the wmemmove_s function stores zeros in the
32795 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
32796 s1max is not greater than RSIZE_MAX.
32799 The wmemmove_s function copies n successive wide characters from the object pointed
32800 to by s2 into the object pointed to by s1. This copying takes place as if the n wide
32801 characters from the object pointed to by s2 are first copied into a temporary array of n
32802 wide characters that does not overlap the objects pointed to by s1 or s2, and then the n
32803 wide characters from the temporary array are copied into the object pointed to by s1.
32806 The wmemmove_s function returns zero if there was no runtime-constraint violation.
32807 Otherwise, a nonzero value is returned.
32810 <h5><a name="K.3.9.2.2" href="#K.3.9.2.2">K.3.9.2.2 Wide string concatenation functions</a></h5>
32816 <pre>
32817 #define __STDC_WANT_LIB_EXT1__ 1
32819 errno_t wcscat_s(wchar_t * restrict s1,
32820 rsize_t s1max,
32821 const wchar_t * restrict s2);
32822 </pre>
32823 Runtime-constraints
32825 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
32826 wcscat_s.
32828 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
32829 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note446"><b>446)</b></a></sup> m shall be greater than
32830 wcsnlen_s(s2, m). Copying shall not take place between objects that overlap.
32831 <!--page 661 -->
32833 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32834 greater than zero and not greater than RSIZE_MAX, then wcscat_s sets s1[0] to the
32835 null wide character.
32838 The wcscat_s function appends a copy of the wide string pointed to by s2 (including
32839 the terminating null wide character) to the end of the wide string pointed to by s1. The
32840 initial wide character from s2 overwrites the null wide character at the end of s1.
32842 All elements following the terminating null wide character (if any) written by
32843 wcscat_s in the array of s1max wide characters pointed to by s1 take unspecified
32847 The wcscat_s function returns zero<sup><a href="#note448"><b>448)</b></a></sup> if there was no runtime-constraint violation.
32848 Otherwise, a nonzero value is returned.
32851 <p><small><a name="note446" href="#note446">446)</a> Zero means that s1 was not null terminated upon entry to wcscat_s.
32852 </small>
32853 <p><small><a name="note447" href="#note447">447)</a> This allows an implementation to append wide characters from s2 to s1 while simultaneously
32854 checking if any of those wide characters are null. Such an approach might write a wide character to
32855 every element of s1 before discovering that the first element should be set to the null wide character.
32856 </small>
32857 <p><small><a name="note448" href="#note448">448)</a> A zero return value implies that all of the requested wide characters from the wide string pointed to by
32858 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
32859 </small>
32865 <pre>
32866 #define __STDC_WANT_LIB_EXT1__ 1
32868 errno_t wcsncat_s(wchar_t * restrict s1,
32869 rsize_t s1max,
32870 const wchar_t * restrict s2,
32871 rsize_t n);
32872 </pre>
32873 Runtime-constraints
32875 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
32876 wcsncat_s.
32878 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32879 RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.<sup><a href="#note449"><b>449)</b></a></sup> If n is not less
32880 than m, then m shall be greater than wcsnlen_s(s2, m). Copying shall not take
32881 place between objects that overlap.
32884 <!--page 662 -->
32886 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32887 greater than zero and not greater than RSIZE_MAX, then wcsncat_s sets s1[0] to the
32888 null wide character.
32891 The wcsncat_s function appends not more than n successive wide characters (wide
32892 characters that follow a null wide character are not copied) from the array pointed to by
32893 s2 to the end of the wide string pointed to by s1. The initial wide character from s2
32894 overwrites the null wide character at the end of s1. If no null wide character was copied
32895 from s2, then s1[s1max-m+n] is set to a null wide character.
32897 All elements following the terminating null wide character (if any) written by
32898 wcsncat_s in the array of s1max wide characters pointed to by s1 take unspecified
32902 The wcsncat_s function returns zero<sup><a href="#note451"><b>451)</b></a></sup> if there was no runtime-constraint violation.
32903 Otherwise, a nonzero value is returned.
32905 EXAMPLE 1 The wcsncat_s function can be used to copy a wide string without the danger that the
32906 result will not be null terminated or that wide characters will be written past the end of the destination
32907 array.
32908 <pre>
32909 #define __STDC_WANT_LIB_EXT1__ 1
32911 /* ... */
32917 int r1, r2, r3, r4;
32922 </pre>
32923 After the first call r1 will have the value zero and s1 will be the wide character sequence goodbye\0.
32924 After the second call r2 will have the value zero and s2 will be the wide character sequence hello\0.
32925 After the third call r3 will have a nonzero value and s3 will be the wide character sequence \0.
32926 After the fourth call r4 will have the value zero and s4 will be the wide character sequence abcdef\0.
32931 <!--page 663 -->
32934 <p><small><a name="note449" href="#note449">449)</a> Zero means that s1 was not null terminated upon entry to wcsncat_s.
32935 </small>
32936 <p><small><a name="note450" href="#note450">450)</a> This allows an implementation to append wide characters from s2 to s1 while simultaneously
32937 checking if any of those wide characters are null. Such an approach might write a wide character to
32938 every element of s1 before discovering that the first element should be set to the null wide character.
32939 </small>
32940 <p><small><a name="note451" href="#note451">451)</a> A zero return value implies that all of the requested wide characters from the wide string pointed to by
32941 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
32942 </small>
32951 <pre>
32952 #define __STDC_WANT_LIB_EXT1__ 1
32954 wchar_t *wcstok_s(wchar_t * restrict s1,
32955 rsize_t * restrict s1max,
32956 const wchar_t * restrict s2,
32957 wchar_t ** restrict ptr);
32958 </pre>
32959 Runtime-constraints
32961 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
32962 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
32963 The end of the token found shall occur within the first *s1max wide characters of s1 for
32964 the first call, and shall occur within the first *s1max wide characters of where searching
32965 resumes on subsequent calls.
32967 If there is a runtime-constraint violation, the wcstok_s function does not indirect
32968 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
32971 A sequence of calls to the wcstok_s function breaks the wide string pointed to by s1
32972 into a sequence of tokens, each of which is delimited by a wide character from the wide
32973 string pointed to by s2. The fourth argument points to a caller-provided wchar_t
32974 pointer into which the wcstok_s function stores information necessary for it to
32975 continue scanning the same wide string.
32977 The first call in a sequence has a non-null first argument and s1max points to an object
32978 whose value is the number of elements in the wide character array pointed to by the first
32979 argument. The first call stores an initial value in the object pointed to by ptr and
32980 updates the value pointed to by s1max to reflect the number of elements that remain in
32981 relation to ptr. Subsequent calls in the sequence have a null first argument and the
32982 objects pointed to by s1max and ptr are required to have the values stored by the
32983 previous call in the sequence, which are then updated. The separator wide string pointed
32984 to by s2 may be different from call to call.
32986 The first call in the sequence searches the wide string pointed to by s1 for the first wide
32987 character that is not contained in the current separator wide string pointed to by s2. If no
32988 such wide character is found, then there are no tokens in the wide string pointed to by s1
32989 and the wcstok_s function returns a null pointer. If such a wide character is found, it is
32990 the start of the first token.
32991 <!--page 664 -->
32993 The wcstok_s function then searches from there for the first wide character in s1 that
32994 is contained in the current separator wide string. If no such wide character is found, the
32995 current token extends to the end of the wide string pointed to by s1, and subsequent
32996 searches in the same wide string for a token return a null pointer. If such a wide character
32997 is found, it is overwritten by a null wide character, which terminates the current token.
32999 In all cases, the wcstok_s function stores sufficient information in the pointer pointed
33000 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
33001 value for ptr, shall start searching just past the element overwritten by a null wide
33002 character (if any).
33005 The wcstok_s function returns a pointer to the first wide character of a token, or a null
33006 pointer if there is no token or there is a runtime-constraint violation.
33008 EXAMPLE
33009 <pre>
33010 #define __STDC_WANT_LIB_EXT1__ 1
33012 static wchar_t str1[] = L"?a???b,,,#c";
33013 static wchar_t str2[] = L"\t \t";
33014 wchar_t *t, *ptr1, *ptr2;
33015 rsize_t max1 = wcslen(str1)+1;
33016 rsize_t max2 = wcslen(str2)+1;
33022 </pre>
33032 <pre>
33033 #define __STDC_WANT_LIB_EXT1__ 1
33035 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
33036 </pre>
33039 The wcsnlen_s function computes the length of the wide string pointed to by s.
33042 If s is a null pointer,<sup><a href="#note452"><b>452)</b></a></sup> then the wcsnlen_s function returns zero.
33044 Otherwise, the wcsnlen_s function returns the number of wide characters that precede
33045 the terminating null wide character. If there is no null wide character in the first
33046 maxsize wide characters of s then wcsnlen_s returns maxsize. At most the first
33047 <!--page 665 -->
33048 maxsize wide characters of s shall be accessed by wcsnlen_s.
33051 <p><small><a name="note452" href="#note452">452)</a> Note that the wcsnlen_s function has no runtime-constraints. This lack of runtime-constraints
33052 along with the values returned for a null pointer or an unterminated wide string argument make
33053 wcsnlen_s useful in algorithms that gracefully handle such exceptional data.
33054 </small>
33057 <h5><a name="K.3.9.3" href="#K.3.9.3">K.3.9.3 Extended multibyte/wide character conversion utilities</a></h5>
33060 <h5><a name="K.3.9.3.1" href="#K.3.9.3.1">K.3.9.3.1 Restartable multibyte/wide character conversion functions</a></h5>
33062 Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the
33063 conversion state) to be a null pointer.
33069 <pre>
33071 errno_t wcrtomb_s(size_t * restrict retval,
33072 char * restrict s, rsize_t smax,
33073 wchar_t wc, mbstate_t * restrict ps);
33074 </pre>
33075 Runtime-constraints
33077 Neither retval nor ps shall be a null pointer. If s is not a null pointer, then smax
33078 shall not equal zero and shall not be greater than RSIZE_MAX. If s is not a null pointer,
33079 then smax shall be not be less than the number of bytes to be stored in the array pointed
33080 to by s. If s is a null pointer, then smax shall equal zero.
33082 If there is a runtime-constraint violation, then wcrtomb_s does the following. If s is
33083 not a null pointer and smax is greater than zero and not greater than RSIZE_MAX, then
33084 wcrtomb_s sets s[0] to the null character. If retval is not a null pointer, then
33085 wcrtomb_s sets *retval to (size_t)(-1).
33088 If s is a null pointer, the wcrtomb_s function is equivalent to the call
33089 <pre>
33091 </pre>
33092 where retval and buf are internal variables of the appropriate types, and the size of
33093 buf is greater than MB_CUR_MAX.
33095 If s is not a null pointer, the wcrtomb_s function determines the number of bytes
33096 needed to represent the multibyte character that corresponds to the wide character given
33097 by wc (including any shift sequences), and stores the multibyte character representation
33098 in the array whose first element is pointed to by s. At most MB_CUR_MAX bytes are
33099 stored. If wc is a null wide character, a null byte is stored, preceded by any shift
33100 sequence needed to restore the initial shift state; the resulting state described is the initial
33101 conversion state.
33103 <!--page 666 -->
33105 If wc does not correspond to a valid multibyte character, an encoding error occurs: the
33106 wcrtomb_s function stores the value (size_t)(-1) into *retval and the
33107 conversion state is unspecified. Otherwise, the wcrtomb_s function stores into
33108 *retval the number of bytes (including any shift sequences) stored in the array pointed
33109 to by s.
33112 The wcrtomb_s function returns zero if no runtime-constraint violation and no
33113 encoding error occurred. Otherwise, a nonzero value is returned.
33116 <h5><a name="K.3.9.3.2" href="#K.3.9.3.2">K.3.9.3.2 Restartable multibyte/wide string conversion functions</a></h5>
33118 Unlike mbsrtowcs and wcsrtombs, mbsrtowcs_s and wcsrtombs_s do not
33119 permit the ps parameter (the pointer to the conversion state) to be a null pointer.
33125 <pre>
33127 errno_t mbsrtowcs_s(size_t * restrict retval,
33128 wchar_t * restrict dst, rsize_t dstmax,
33129 const char ** restrict src, rsize_t len,
33130 mbstate_t * restrict ps);
33131 </pre>
33132 Runtime-constraints
33134 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
33135 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
33136 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
33137 not equal zero. If dst is not a null pointer and len is not less than dstmax, then a null
33138 character shall occur within the first dstmax multibyte characters of the array pointed to
33139 by *src.
33141 If there is a runtime-constraint violation, then mbsrtowcs_s does the following. If
33142 retval is not a null pointer, then mbsrtowcs_s sets *retval to (size_t)(-1).
33143 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
33144 then mbsrtowcs_s sets dst[0] to the null wide character.
33147 The mbsrtowcs_s function converts a sequence of multibyte characters that begins in
33148 the conversion state described by the object pointed to by ps, from the array indirectly
33149 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
33150 pointer, the converted characters are stored into the array pointed to by dst. Conversion
33151 continues up to and including a terminating null character, which is also stored.
33152 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
33153 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
33154 <!--page 667 -->
33155 characters have been stored into the array pointed to by dst.<sup><a href="#note453"><b>453)</b></a></sup> If dst is not a null
33156 pointer and no null wide character was stored into the array pointed to by dst, then
33157 dst[len] is set to the null wide character. Each conversion takes place as if by a call
33158 to the mbrtowc function.
33160 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
33161 pointer (if conversion stopped due to reaching a terminating null character) or the address
33162 just past the last multibyte character converted (if any). If conversion stopped due to
33163 reaching a terminating null character and if dst is not a null pointer, the resulting state
33164 described is the initial conversion state.
33166 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
33167 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
33168 the mbsrtowcs_s function stores the value (size_t)(-1) into *retval and the
33169 conversion state is unspecified. Otherwise, the mbsrtowcs_s function stores into
33170 *retval the number of multibyte characters successfully converted, not including the
33171 terminating null character (if any).
33173 All elements following the terminating null wide character (if any) written by
33174 mbsrtowcs_s in the array of dstmax wide characters pointed to by dst take
33177 If copying takes place between objects that overlap, the objects take on unspecified
33178 values.
33181 The mbsrtowcs_s function returns zero if no runtime-constraint violation and no
33182 encoding error occurred. Otherwise, a nonzero value is returned.
33185 <p><small><a name="note453" href="#note453">453)</a> Thus, the value of len is ignored if dst is a null pointer.
33186 </small>
33187 <p><small><a name="note454" href="#note454">454)</a> This allows an implementation to attempt converting the multibyte string before discovering a
33188 terminating null character did not occur where required.
33189 </small>
33195 <pre>
33197 errno_t wcsrtombs_s(size_t * restrict retval,
33198 char * restrict dst, rsize_t dstmax,
33199 const wchar_t ** restrict src, rsize_t len,
33200 mbstate_t * restrict ps);
33201 </pre>
33206 <!--page 668 -->
33207 Runtime-constraints
33209 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
33210 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
33211 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
33212 not equal zero. If dst is not a null pointer and len is not less than dstmax, then the
33213 conversion shall have been stopped (see below) because a terminating null wide character
33214 was reached or because an encoding error occurred.
33216 If there is a runtime-constraint violation, then wcsrtombs_s does the following. If
33217 retval is not a null pointer, then wcsrtombs_s sets *retval to (size_t)(-1).
33218 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
33219 then wcsrtombs_s sets dst[0] to the null character.
33222 The wcsrtombs_s function converts a sequence of wide characters from the array
33223 indirectly pointed to by src into a sequence of corresponding multibyte characters that
33224 begins in the conversion state described by the object pointed to by ps. If dst is not a
33225 null pointer, the converted characters are then stored into the array pointed to by dst.
33226 Conversion continues up to and including a terminating null wide character, which is also
33227 stored. Conversion stops earlier in two cases:
33228 <ul>
33229 <li> when a wide character is reached that does not correspond to a valid multibyte
33230 character;
33231 <li> (if dst is not a null pointer) when the next multibyte character would exceed the
33232 limit of n total bytes to be stored into the array pointed to by dst. If the wide
33233 character being converted is the null wide character, then n is the lesser of len or
33234 dstmax. Otherwise, n is the lesser of len or dstmax-1.
33235 </ul>
33236 If the conversion stops without converting a null wide character and dst is not a null
33237 pointer, then a null character is stored into the array pointed to by dst immediately
33238 following any multibyte characters already stored. Each conversion takes place as if by a
33241 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
33242 pointer (if conversion stopped due to reaching a terminating null wide character) or the
33243 address just past the last wide character converted (if any). If conversion stopped due to
33244 reaching a terminating null wide character, the resulting state described is the initial
33245 conversion state.
33248 <!--page 669 -->
33250 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
33251 wide character that does not correspond to a valid multibyte character, an encoding error
33252 occurs: the wcsrtombs_s function stores the value (size_t)(-1) into *retval
33253 and the conversion state is unspecified. Otherwise, the wcsrtombs_s function stores
33254 into *retval the number of bytes in the resulting multibyte character sequence, not
33255 including the terminating null character (if any).
33257 All elements following the terminating null character (if any) written by wcsrtombs_s
33258 in the array of dstmax elements pointed to by dst take unspecified values when
33261 If copying takes place between objects that overlap, the objects take on unspecified
33262 values.
33265 The wcsrtombs_s function returns zero if no runtime-constraint violation and no
33266 encoding error occurred. Otherwise, a nonzero value is returned.
33271 <!--page 670 -->
33274 <p><small><a name="note455" href="#note455">455)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
33275 include those necessary to reach the initial shift state immediately before the null byte. However, if
33276 the conversion stops before a terminating null wide character has been reached, the result will be null
33277 terminated, but might not end in the initial shift state.
33278 </small>
33279 <p><small><a name="note456" href="#note456">456)</a> When len is not less than dstmax, the implementation might fill the array before discovering a
33280 runtime-constraint violation.
33281 </small>
33285 <pre>
33286 (normative)
33287 Analyzability
33288 </pre>
33293 This annex specifies optional behavior that can aid in the analyzability of C programs.
33295 An implementation that defines __STDC_ANALYZABLE__ shall conform to the
33299 <p><small><a name="note457" href="#note457">457)</a> Implementations that do not define __STDC_ANALYZABLE__ are not required to conform to these
33300 specifications.
33301 </small>
33309 out-of-bounds store
33310 an (attempted) access (<a href="#3.1">3.1</a>) that, at run time, for a given computational state, would
33311 modify (or, for an object declared volatile, fetch) one or more bytes that lie outside
33312 the bounds permitted by this Standard.
33317 bounded undefined behavior
33320 NOTE 1 The behavior might perform a trap.
33323 NOTE 2 Any values produced or stored might be indeterminate values.
33329 critical undefined behavior
33330 undefined behavior that is not bounded undefined behavior.
33332 NOTE The behavior might perform an out-of-bounds store or perform a trap.
33337 <!--page 671 -->
33342 If the program performs a trap (<a href="#3.19.5">3.19.5</a>), the implementation is permitted to invoke a
33343 runtime-constraint handler. Any such semantics are implementation-defined.
33345 All undefined behavior shall be limited to bounded undefined behavior, except for the
33346 following which are permitted to result in critical undefined behavior:
33347 <ul>
33349 <li> A store is performed to an object that has two incompatible declarations (<a href="#6.2.7">6.2.7</a>),
33350 <li> A pointer is used to call a function whose type is not compatible with the referenced
33351 type (<a href="#6.2.7">6.2.7</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.5.2.2">6.5.2.2</a>).
33354 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
33355 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
33356 integer type produces a result that points just beyond the array object and is used as
33358 <li> An attempt is made to modify an object defined with a const-qualified type through
33360 <li> An argument to a function or macro defined in the standard library has an invalid
33361 value or a type not expected by a function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
33362 <li> The longjmp function is called with a jmp_buf argument where the most recent
33363 invocation of the setjmp macro in the same invocation of the program with the
33364 corresponding jmp_buf argument is nonexistent, or the invocation was from another
33365 thread of execution, or the function containing the invocation has terminated
33366 execution in the interim, or the invocation was within the scope of an identifier with
33367 variably modified type and execution has left that scope in the interim (<a href="#7.13.2.1">7.13.2.1</a>).
33368 <li> The value of a pointer that refers to space deallocated by a call to the free or realloc
33370 <li> A string or wide string utility function accesses an array beyond the end of an object
33372 <!--page 672 -->
33373 </ul>
33377 <ol>
33378 <li> ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
33379 published in The C Programming Language by Brian W. Kernighan and Dennis
33382 California, USA, November 1984.
33384 Processing Systems, Information Processing Systems Technical Report.
33386 Arithmetic.
33388 Floating-Point Arithmetic.
33392 symbols for use in the physical sciences and technology.
33394 information interchange.
33396 Fundamental terms.
33399 interchange -- Representation of dates and times.
33408 <!--page 673 -->
33410 Interface (POSIX) -- Part 2: Shell and Utilities.
33412 preparation of programming language standards.
33414 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
33426 syllables.
33428 Tibetan.
33430 additional characters.
33433 Identifiers for characters.
33435 Ethiopic.
33437 Unified Canadian Aboriginal Syllabics.
33439 Cherokee.
33441 arithmetic -- Part 1: Integer and floating point arithmetic.
33442 <!--page 674 -->
33444 their environments and system software interfaces -- Extensions for the
33445 programming language C to support new character data types.
33447 their environments and system software interfaces -- Extensions to the C library
33448 -- Part 1: Bounds-checking interfaces.
33449 <!--page 675 -->
33450 </ol>
33454 <pre>
33455 [^ x ^], <a href="#3.20">3.20</a> , (comma operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.17">6.5.17</a>
33456 , (comma punctuator), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>,
33458 ! (logical negation operator), <a href="#6.5.3.3">6.5.3.3</a> - (subtraction operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a>
33459 != (inequality operator), <a href="#6.5.9">6.5.9</a> - (unary minus operator), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a>
33460 # operator, <a href="#6.10.3.2">6.10.3.2</a> -- (postfix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a>
33461 # preprocessing directive, <a href="#6.10.7">6.10.7</a> -- (prefix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a>
33462 # punctuator, <a href="#6.10">6.10</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
33463 ## operator, <a href="#6.10.3.3">6.10.3.3</a> -> (structure/union pointer operator), <a href="#6.5.2.3">6.5.2.3</a>
33464 #define preprocessing directive, <a href="#6.10.3">6.10.3</a> . (structure/union member operator), <a href="#6.3.2.1">6.3.2.1</a>,
33466 #else preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.9">6.7.9</a>
33467 #endif preprocessing directive, <a href="#6.10.1">6.10.1</a> ... (ellipsis punctuator), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.10.3">6.10.3</a>
33468 #error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> / (division operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a>
33469 #if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, /* */ (comment delimiters), <a href="#6.4.9">6.4.9</a>
33470 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> // (comment delimiter), <a href="#6.4.9">6.4.9</a>
33471 #ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> /= (division assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
33472 #ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> : (colon punctuator), <a href="#6.7.2.1">6.7.2.1</a>
33473 #include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, :> (alternative spelling of ]), <a href="#6.4.6">6.4.6</a>
33474 <a href="#6.10.2">6.10.2</a> ; (semicolon punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>,
33475 #line preprocessing directive, <a href="#6.10.4">6.10.4</a> <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a>
33476 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
33477 #undef preprocessing directive, <a href="#6.10.3.5">6.10.3.5</a>, <a href="#7.1.3">7.1.3</a>, <% (alternative spelling of {), <a href="#6.4.6">6.4.6</a>
33479 % (remainder operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a> << (left-shift operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
33480 %: (alternative spelling of #), <a href="#6.4.6">6.4.6</a> <<= (left-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
33481 %:%: (alternative spelling of ##), <a href="#6.4.6">6.4.6</a> <= (less-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a>
33482 %= (remainder assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.2"><assert.h></a> header, <a href="#7.2">7.2</a>
33483 %> (alternative spelling of }), <a href="#6.4.6">6.4.6</a> <a href="#7.3"><complex.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>,
33484 & (address operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#7.3">7.3</a>, <a href="#7.25">7.25</a>, <a href="#7.31.1">7.31.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
33485 & (bitwise AND operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.10">6.5.10</a> <a href="#7.4"><ctype.h></a> header, <a href="#7.4">7.4</a>, <a href="#7.31.2">7.31.2</a>
33486 && (logical AND operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a> <a href="#7.5"><errno.h></a> header, <a href="#7.5">7.5</a>, <a href="#7.31.3">7.31.3</a>, <a href="#K.3.2">K.3.2</a>
33487 &= (bitwise AND assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.6"><fenv.h></a> header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>,
33488 ' ' (space character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.31.4">7.31.4</a>, <a href="#F">F</a>, <a href="#H">H</a>
33489 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.30.2.1.3">7.30.2.1.3</a> <a href="#7.7"><float.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.22.1.3">7.22.1.3</a>,
33491 ( ) (function-call operator), <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.8"><inttypes.h></a> header, <a href="#7.8">7.8</a>, <a href="#7.31.5">7.31.5</a>
33492 ( ) (parentheses punctuator), <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a> <a href="#7.9"><iso646.h></a> header, <a href="#4">4</a>, <a href="#7.9">7.9</a>
33493 ( ){ } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> <a href="#7.10"><limits.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
33494 * (asterisk punctuator), <a href="#6.7.6.1">6.7.6.1</a>, <a href="#6.7.6.2">6.7.6.2</a> <a href="#7.11"><locale.h></a> header, <a href="#7.11">7.11</a>, <a href="#7.31.6">7.31.6</a>
33495 * (indirection operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#7.12"><math.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.25">7.25</a>, <a href="#F">F</a>,
33496 * (multiplication operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10">F.10</a>, <a href="#J.5.17">J.5.17</a>
33497 <a href="#G.5.1">G.5.1</a> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
33498 *= (multiplication assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.14"><signal.h></a> header, <a href="#7.14">7.14</a>, <a href="#7.31.7">7.31.7</a>
33499 + (addition operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, <a href="#7.15"><stdalign.h></a> header, <a href="#4">4</a>, <a href="#7.15">7.15</a>
33500 <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a> <a href="#7.16"><stdarg.h></a> header, <a href="#4">4</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#7.16">7.16</a>
33501 + (unary plus operator), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.17"><stdatomic.h></a> header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.17">7.17</a>,
33502 ++ (postfix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> <a href="#7.31.8">7.31.8</a>
33503 ++ (prefix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> <a href="#7.18"><stdbool.h></a> header, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.31.9">7.31.9</a>, <a href="#H">H</a>
33505 <!--page 676 -->
33506 <a href="#7.19"><stddef.h></a> header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, \u (universal character names), <a href="#6.4.3">6.4.3</a>
33507 <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.19">7.19</a>, <a href="#K.3.3">K.3.3</a> \v (vertical-tab escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
33508 <a href="#7.20"><stdint.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.4.1.10">7.4.1.10</a>
33509 <a href="#7.20">7.20</a>, <a href="#7.31.10">7.31.10</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a> \x hexadecimal digits (hexadecimal-character
33510 <a href="#7.21"><stdio.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21">7.21</a>, <a href="#7.31.11">7.31.11</a>, <a href="#F">F</a>, escape sequence), <a href="#6.4.4.4">6.4.4.4</a>
33511 <a href="#K.3.5">K.3.5</a> ^ (bitwise exclusive OR operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a>
33512 <a href="#7.22"><stdlib.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.22">7.22</a>, <a href="#7.31.12">7.31.12</a>, <a href="#F">F</a>, ^= (bitwise exclusive OR assignment operator),
33514 <a href="#7.23"><stdnoreturn.h></a> header, <a href="#4">4</a>, <a href="#7.23">7.23</a> __alignas_is_defined macro, <a href="#7.15">7.15</a>
33515 <a href="#7.24"><string.h></a> header, <a href="#7.24">7.24</a>, <a href="#7.31.13">7.31.13</a>, <a href="#K.3.7">K.3.7</a> __alignof_is_defined macro, <a href="#7.15">7.15</a>
33516 <a href="#7.25"><tgmath.h></a> header, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> __bool_true_false_are_defined
33517 <a href="#7.26"><threads.h></a> header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.26">7.26</a>, macro, <a href="#7.18">7.18</a>
33519 <a href="#7.27"><time.h></a> header, <a href="#7.26.1">7.26.1</a>, <a href="#7.27">7.27</a>, <a href="#7.31.14">7.31.14</a>, <a href="#K.3.8">K.3.8</a> __DATE__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33520 <a href="#7.28"><uchar.h></a> header, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.28">7.28</a> __FILE__ macro, <a href="#6.10.8.1">6.10.8.1</a>, <a href="#7.2.1.1">7.2.1.1</a>
33521 <a href="#7.29"><wchar.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.29">7.29</a>, __func__ identifier, <a href="#6.4.2.2">6.4.2.2</a>, <a href="#7.2.1.1">7.2.1.1</a>
33522 <a href="#7.31.16">7.31.16</a>, <a href="#F">F</a>, <a href="#K.3.9">K.3.9</a> __LINE__ macro, <a href="#6.10.8.1">6.10.8.1</a>, <a href="#7.2.1.1">7.2.1.1</a>
33523 <a href="#7.30"><wctype.h></a> header, <a href="#7.30">7.30</a>, <a href="#7.31.17">7.31.17</a> __STDC_, <a href="#6.11.9">6.11.9</a>
33524 = (equal-sign punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.9">6.7.9</a> __STDC__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33525 = (simple assignment operator), <a href="#6.5.16.1">6.5.16.1</a> __STDC_ANALYZABLE__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#L.1">L.1</a>
33526 == (equality operator), <a href="#6.5.9">6.5.9</a> __STDC_HOSTED__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33527 > (greater-than operator), <a href="#6.5.8">6.5.8</a> __STDC_IEC_559__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#F.1">F.1</a>
33528 >= (greater-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a> __STDC_IEC_559_COMPLEX__ macro,
33529 >> (right-shift operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a> <a href="#6.10.8.3">6.10.8.3</a>, <a href="#G.1">G.1</a>
33530 >>= (right-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a> __STDC_ISO_10646__ macro, <a href="#6.10.8.2">6.10.8.2</a>
33531 ? : (conditional operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.15">6.5.15</a> __STDC_LIB_EXT1__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#K.2">K.2</a>
33533 [ ] (array subscript operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#6.10.8.2">6.10.8.2</a>, <a href="#7.19">7.19</a>
33534 [ ] (brackets punctuator), <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.9">6.7.9</a> __STDC_NO_ATOMICS__ macro, <a href="#6.10.8.3">6.10.8.3</a>,
33535 \ (backslash character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a> <a href="#7.17.1">7.17.1</a>
33536 \ (escape character), <a href="#6.4.4.4">6.4.4.4</a> __STDC_NO_COMPLEX__ macro, <a href="#6.10.8.3">6.10.8.3</a>,
33538 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> __STDC_NO_THREADS__ macro, <a href="#6.10.8.3">6.10.8.3</a>,
33539 \\ (backslash escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a> <a href="#7.26.1">7.26.1</a>
33540 \' (single-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> __STDC_NO_VLA__ macro, <a href="#6.10.8.3">6.10.8.3</a>
33541 \0 (null character), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> __STDC_UTF_16__ macro, <a href="#6.10.8.2">6.10.8.2</a>
33542 padding of binary stream, <a href="#7.21.2">7.21.2</a> __STDC_UTF_32__ macro, <a href="#6.10.8.2">6.10.8.2</a>
33543 \? (question-mark escape sequence), <a href="#6.4.4.4">6.4.4.4</a> __STDC_VERSION__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33544 \a (alert escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> __STDC_WANT_LIB_EXT1__ macro, <a href="#K.3.1.1">K.3.1.1</a>
33545 \b (backspace escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> __TIME__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33546 \f (form-feed escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, __VA_ARGS__ identifier, <a href="#6.10.3">6.10.3</a>, <a href="#6.10.3.1">6.10.3.1</a>
33548 \n (new-line escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, _Alignof operator, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3">6.5.3</a>, <a href="#6.5.3.4">6.5.3.4</a>
33550 \octal digits (octal-character escape sequence), _Atomic type specifier, <a href="#6.7.2.4">6.7.2.4</a>
33551 <a href="#6.4.4.4">6.4.4.4</a> _Bool type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#F.4">F.4</a>
33552 \r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, _Bool type conversions, <a href="#6.3.1.2">6.3.1.2</a>
33553 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> _Complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
33554 \t (horizontal-tab escape sequence), <a href="#5.2.2">5.2.2</a>, _Complex_I macro, <a href="#7.3.1">7.3.1</a>
33555 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.30.2.1.3">7.30.2.1.3</a> _Exit function, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>
33556 \U (universal character names), <a href="#6.4.3">6.4.3</a> _Imaginary keyword, <a href="#G.2">G.2</a>
33557 <!--page 677 -->
33558 _Imaginary types, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a> aliasing, <a href="#6.5">6.5</a>
33559 _Imaginary_I macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a> alignas macro, <a href="#7.15">7.15</a>
33560 _IOFBF macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.5">7.21.5.5</a>, <a href="#7.21.5.6">7.21.5.6</a> aligned_alloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.1">7.22.3.1</a>
33561 _IOLBF macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.6">7.21.5.6</a> alignment, <a href="#3.2">3.2</a>, <a href="#6.2.8">6.2.8</a>, <a href="#7.22.3.1">7.22.3.1</a>
33562 _IONBF macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.5">7.21.5.5</a>, <a href="#7.21.5.6">7.21.5.6</a> pointer, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.3">6.3.2.3</a>
33565 _Pragma operator, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a> alignment specifier, <a href="#6.7.5">6.7.5</a>
33566 _Static_assert, <a href="#6.7.10">6.7.10</a>, <a href="#7.2">7.2</a> alignof macro, <a href="#7.15">7.15</a>
33567 _Thread_local storage-class specifier, <a href="#6.2.4">6.2.4</a>, allocated storage, order and contiguity, <a href="#7.22.3">7.22.3</a>
33568 <a href="#6.7.1">6.7.1</a>, <a href="#7.26.1">7.26.1</a> alternative spellings header, <a href="#7.9">7.9</a>
33569 { } (braces punctuator), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a>, and macro, <a href="#7.9">7.9</a>
33571 { } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> bitwise (&), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.10">6.5.10</a>
33572 | (bitwise inclusive OR operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a> bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a>
33573 |= (bitwise inclusive OR assignment operator), logical (&&), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a>
33575 || (logical OR operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a> anonymous structure, <a href="#6.7.2.1">6.7.2.1</a>
33576 ~ (bitwise complement operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a> anonymous union, <a href="#6.7.2.1">6.7.2.1</a>
33578 abort function, <a href="#7.2.1.1">7.2.1.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.21.3">7.21.3</a>, ANSI/IEEE 854, <a href="#F.1">F.1</a>
33579 <a href="#7.22.4.1">7.22.4.1</a>, <a href="#K.3.6.1.2">K.3.6.1.2</a> argc (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a>
33583 complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a> function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
33584 integer, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.22.6.1">7.22.6.1</a> macro, substitution, <a href="#6.10.3.1">6.10.3.1</a>
33585 real, <a href="#7.12.7">7.12.7</a>, <a href="#F.10.4">F.10.4</a> argument, complex, <a href="#7.3.9.1">7.3.9.1</a>
33586 abstract declarator, <a href="#6.7.7">6.7.7</a> argv (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a>
33587 abstract machine, <a href="#5.1.2.3">5.1.2.3</a> arithmetic constant expression, <a href="#6.6">6.6</a>
33588 access, <a href="#3.1">3.1</a>, <a href="#6.7.3">6.7.3</a>, <a href="#L.2.1">L.2.1</a> arithmetic conversions, usual, see usual arithmetic
33589 accuracy, see floating-point accuracy conversions
33590 acos functions, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#F.10.1.1">F.10.1.1</a> arithmetic operators
33591 acos type-generic macro, <a href="#7.25">7.25</a> additive, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a>
33592 acosh functions, <a href="#7.12.5.1">7.12.5.1</a>, <a href="#F.10.2.1">F.10.2.1</a> bitwise, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a>, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a>
33593 acosh type-generic macro, <a href="#7.25">7.25</a> increment and decrement, <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.3.1">6.5.3.1</a>
33594 acquire fence, <a href="#7.17.4">7.17.4</a> multiplicative, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
33595 acquire operation, <a href="#5.1.2.4">5.1.2.4</a> shift, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
33598 actual parameter (deprecated), <a href="#3.3">3.3</a> arithmetic, pointer, <a href="#6.5.6">6.5.6</a>
33600 addition operator (+), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, argument, <a href="#6.9.1">6.9.1</a>
33601 <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a> declarator, <a href="#6.7.6.2">6.7.6.2</a>
33602 additive expressions, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> initialization, <a href="#6.7.9">6.7.9</a>
33604 address operator (&), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> parameter, <a href="#6.9.1">6.9.1</a>
33606 aggregate initialization, <a href="#6.7.9">6.7.9</a> subscript operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>
33608 alert escape sequence (\a), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> type, <a href="#6.2.5">6.2.5</a>
33609 <!--page 678 -->
33611 variable length, <a href="#6.7.6">6.7.6</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a> atomic_flag type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.8">7.17.8</a>
33612 arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a> atomic_flag_clear functions, <a href="#7.17.8.2">7.17.8.2</a>
33613 as-if rule, <a href="#5.1.2.3">5.1.2.3</a> ATOMIC_FLAG_INIT macro, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.8">7.17.8</a>
33616 asctime_s function, <a href="#K.3.8.2">K.3.8.2</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a> atomic_init generic function, <a href="#7.17.2.2">7.17.2.2</a>
33617 asin functions, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#F.10.1.2">F.10.1.2</a> ATOMIC_INT_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33618 asin type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> atomic_is_lock_free generic function,
33619 asinh functions, <a href="#7.12.5.2">7.12.5.2</a>, <a href="#F.10.2.2">F.10.2.2</a> <a href="#7.17.5.1">7.17.5.1</a>
33620 asinh type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> ATOMIC_LLONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33621 asm keyword, <a href="#J.5.10">J.5.10</a> atomic_load generic functions, <a href="#7.17.7.2">7.17.7.2</a>
33622 assert macro, <a href="#7.2.1.1">7.2.1.1</a> ATOMIC_LONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33623 assert.h header, <a href="#7.2">7.2</a> ATOMIC_LLONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33625 compound, <a href="#6.5.16.2">6.5.16.2</a> atomic_signal_fence function, <a href="#7.17.4.2">7.17.4.2</a>
33626 conversion, <a href="#6.5.16.1">6.5.16.1</a> atomic_store generic functions, <a href="#7.17.7.1">7.17.7.1</a>
33627 expression, <a href="#6.5.16">6.5.16</a> atomic_thread_fence function, <a href="#7.17.4.1">7.17.4.1</a>
33628 operators, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a> ATOMIC_VAR_INIT macro, <a href="#7.17.2.1">7.17.2.1</a>
33629 simple, <a href="#6.5.16.1">6.5.16.1</a> ATOMIC_WCHAR_T_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33630 associativity of operators, <a href="#6.5">6.5</a> atomics header, <a href="#7.17">7.17</a>, <a href="#7.31.8">7.31.8</a>
33631 asterisk punctuator (*), <a href="#6.7.6.1">6.7.6.1</a>, <a href="#6.7.6.2">6.7.6.2</a> auto storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
33632 at_quick_exit function, <a href="#7.22.4.2">7.22.4.2</a>, <a href="#7.22.4.3">7.22.4.3</a>, automatic storage duration, <a href="#5.2.3">5.2.3</a>, <a href="#6.2.4">6.2.4</a>
33633 <a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>
33634 atan functions, <a href="#7.12.4.3">7.12.4.3</a>, <a href="#F.10.1.3">F.10.1.3</a> backslash character (\), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
33635 atan type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> backslash escape sequence (\\), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a>
33636 atan2 functions, <a href="#7.12.4.4">7.12.4.4</a>, <a href="#F.10.1.4">F.10.1.4</a> backspace escape sequence (\b), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
33637 atan2 type-generic macro, <a href="#7.25">7.25</a> basic character set, <a href="#3.6">3.6</a>, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>
33638 atanh functions, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#F.10.2.3">F.10.2.3</a> basic types, <a href="#6.2.5">6.2.5</a>
33639 atanh type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> behavior, <a href="#3.4">3.4</a>
33640 atexit function, <a href="#7.22.4.2">7.22.4.2</a>, <a href="#7.22.4.3">7.22.4.3</a>, <a href="#7.22.4.4">7.22.4.4</a>, binary streams, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>,
33641 <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>, <a href="#J.5.13">J.5.13</a> <a href="#7.21.9.4">7.21.9.4</a>
33642 atof function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.1">7.22.1.1</a> bit, <a href="#3.5">3.5</a>
33643 atoi function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> high order, <a href="#3.6">3.6</a>
33644 atol function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> low order, <a href="#3.6">3.6</a>
33645 atoll function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> bit-field, <a href="#6.7.2.1">6.7.2.1</a>
33646 atomic lock-free macros, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.5">7.17.5</a> bitand macro, <a href="#7.9">7.9</a>
33648 atomic types, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.2.5">6.2.5</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, bitwise operators, <a href="#6.5">6.5</a>
33649 <a href="#6.5.2.3">6.5.2.3</a>, <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.16.2">6.5.16.2</a>, <a href="#6.7.2.4">6.7.2.4</a>, <a href="#6.10.8.3">6.10.8.3</a>, AND, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.10">6.5.10</a>
33651 ATOMIC_CHAR_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a> complement (~), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a>
33652 ATOMIC_CHAR16_T_LOCK_FREE macro, exclusive OR, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a>
33654 ATOMIC_CHAR32_T_LOCK_FREE macro, inclusive OR, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a>
33656 ATOMIC_CHAR_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a> shift, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
33658 functions, <a href="#7.17.7.4">7.17.7.4</a> block, <a href="#6.8">6.8</a>, <a href="#6.8.2">6.8.2</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a>
33659 atomic_exchange generic functions, <a href="#7.17.7.3">7.17.7.3</a> block scope, <a href="#6.2.1">6.2.1</a>
33661 <!--page 679 -->
33665 boolean type and values header, <a href="#7.18">7.18</a>, <a href="#7.31.9">7.31.9</a> catan functions, <a href="#7.3.5.3">7.3.5.3</a>, <a href="#G.6">G.6</a>
33666 boolean type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a> type-generic macro for, <a href="#7.25">7.25</a>
33667 bounded undefined behavior, <a href="#L.2.2">L.2.2</a> catanh functions, <a href="#7.3.6.3">7.3.6.3</a>, <a href="#G.6.2.3">G.6.2.3</a>
33668 braces punctuator ({ }), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a>, type-generic macro for, <a href="#7.25">7.25</a>
33669 <a href="#6.8.2">6.8.2</a> cbrt functions, <a href="#7.12.7.1">7.12.7.1</a>, <a href="#F.10.4.1">F.10.4.1</a>
33670 brackets operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> cbrt type-generic macro, <a href="#7.25">7.25</a>
33671 brackets punctuator ([ ]), <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.9">6.7.9</a> ccos functions, <a href="#7.3.5.4">7.3.5.4</a>, <a href="#G.6">G.6</a>
33673 break statement, <a href="#6.8.6.3">6.8.6.3</a> ccosh functions, <a href="#7.3.6.4">7.3.6.4</a>, <a href="#G.6.2.4">G.6.2.4</a>
33674 broken-down time, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.3">7.27.2.3</a>, <a href="#7.27.3">7.27.3</a>, type-generic macro for, <a href="#7.25">7.25</a>
33675 <a href="#7.27.3.1">7.27.3.1</a>, <a href="#7.27.3.3">7.27.3.3</a>, <a href="#7.27.3.4">7.27.3.4</a>, <a href="#7.27.3.5">7.27.3.5</a>, ceil functions, <a href="#7.12.9.1">7.12.9.1</a>, <a href="#F.10.6.1">F.10.6.1</a>
33676 <a href="#K.3.8.2.1">K.3.8.2.1</a>, <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a> ceil type-generic macro, <a href="#7.25">7.25</a>
33677 bsearch function, <a href="#7.22.5">7.22.5</a>, <a href="#7.22.5.1">7.22.5.1</a> cerf function, <a href="#7.31.1">7.31.1</a>
33678 bsearch_s function, <a href="#K.3.6.3">K.3.6.3</a>, <a href="#K.3.6.3.1">K.3.6.3.1</a> cerfc function, <a href="#7.31.1">7.31.1</a>
33679 btowc function, <a href="#7.29.6.1.1">7.29.6.1.1</a> cexp functions, <a href="#7.3.7.1">7.3.7.1</a>, <a href="#G.6.3.1">G.6.3.1</a>
33680 BUFSIZ macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.5.5">7.21.5.5</a> type-generic macro for, <a href="#7.25">7.25</a>
33681 byte, <a href="#3.6">3.6</a>, <a href="#6.5.3.4">6.5.3.4</a> cexp2 function, <a href="#7.31.1">7.31.1</a>
33682 byte input/output functions, <a href="#7.21.1">7.21.1</a> cexpm1 function, <a href="#7.31.1">7.31.1</a>
33683 byte-oriented stream, <a href="#7.21.2">7.21.2</a> char type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>,
33685 <a href="#C">C</a> program, <a href="#5.1.1.1">5.1.1.1</a> char type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
33687 c32rtomb function, <a href="#7.28.1.4">7.28.1.4</a> char16_t type, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.10.8.2">6.10.8.2</a>,
33688 cabs functions, <a href="#7.3.8.1">7.3.8.1</a>, <a href="#G.6">G.6</a> <a href="#7.28">7.28</a>
33689 type-generic macro for, <a href="#7.25">7.25</a> char32_t type, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.10.8.2">6.10.8.2</a>,
33690 cacos functions, <a href="#7.3.5.1">7.3.5.1</a>, <a href="#G.6.1.1">G.6.1.1</a> <a href="#7.28">7.28</a>
33691 type-generic macro for, <a href="#7.25">7.25</a> CHAR_BIT macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.7.2.1">6.7.2.1</a>
33692 cacosh functions, <a href="#7.3.6.1">7.3.6.1</a>, <a href="#G.6.2.1">G.6.2.1</a> CHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
33693 type-generic macro for, <a href="#7.25">7.25</a> CHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
33694 calendar time, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.2">7.27.2.2</a>, <a href="#7.27.2.3">7.27.2.3</a>, <a href="#7.27.2.4">7.27.2.4</a>, character, <a href="#3.7">3.7</a>, <a href="#3.7.1">3.7.1</a>
33695 <a href="#7.27.3.2">7.27.3.2</a>, <a href="#7.27.3.3">7.27.3.3</a>, <a href="#7.27.3.4">7.27.3.4</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>, character array initialization, <a href="#6.7.9">6.7.9</a>
33696 <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a> character case mapping functions, <a href="#7.4.2">7.4.2</a>
33697 call by value, <a href="#6.5.2.2">6.5.2.2</a> wide character, <a href="#7.30.3.1">7.30.3.1</a>
33698 call_once function, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.1">7.26.2.1</a> extensible, <a href="#7.30.3.2">7.30.3.2</a>
33699 calloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.2">7.22.3.2</a> character classification functions, <a href="#7.4.1">7.4.1</a>
33700 carg functions, <a href="#7.3.9.1">7.3.9.1</a>, <a href="#G.6">G.6</a> wide character, <a href="#7.30.2.1">7.30.2.1</a>
33701 carg type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> extensible, <a href="#7.30.2.2">7.30.2.2</a>
33702 carriage-return escape sequence (\r), <a href="#5.2.2">5.2.2</a>, character constant, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
33703 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> character display semantics, <a href="#5.2.2">5.2.2</a>
33704 carries a dependency, <a href="#5.1.2.4">5.1.2.4</a> character handling header, <a href="#7.4">7.4</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.31.2">7.31.2</a>
33705 case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> character input/output functions, <a href="#7.21.7">7.21.7</a>, <a href="#K.3.5.4">K.3.5.4</a>
33709 extensible, <a href="#7.30.3.2">7.30.3.2</a> character type conversion, <a href="#6.3.1.1">6.3.1.1</a>
33710 casin functions, <a href="#7.3.5.2">7.3.5.2</a>, <a href="#G.6">G.6</a> character types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.9">6.7.9</a>
33711 type-generic macro for, <a href="#7.25">7.25</a> characteristics of floating types header, <a href="#7.7">7.7</a>
33712 casinh functions, <a href="#7.3.6.2">7.3.6.2</a>, <a href="#G.6.2.2">G.6.2.2</a> cimag functions, <a href="#7.3.9.2">7.3.9.2</a>, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a>
33713 <!--page 680 -->
33714 cimag type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> complex macro, <a href="#7.3.1">7.3.1</a>
33715 cis function, <a href="#G.6">G.6</a> complex numbers, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a>
33716 classification functions complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#6.3.1.7">6.3.1.7</a>
33718 floating-point, <a href="#7.12.3">7.12.3</a> complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#G">G</a>
33719 wide character, <a href="#7.30.2.1">7.30.2.1</a> complex.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>,
33720 extensible, <a href="#7.30.2.2">7.30.2.2</a> <a href="#7.3">7.3</a>, <a href="#7.25">7.25</a>, <a href="#7.31.1">7.31.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
33722 clgamma function, <a href="#7.31.1">7.31.1</a> components of time, <a href="#7.27.1">7.27.1</a>, <a href="#K.3.8.1">K.3.8.1</a>
33724 clock_t type, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.1">7.27.2.1</a> compound assignment, <a href="#6.5.16.2">6.5.16.2</a>
33725 CLOCKS_PER_SEC macro, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.1">7.27.2.1</a> compound literals, <a href="#6.5.2.5">6.5.2.5</a>
33726 clog functions, <a href="#7.3.7.2">7.3.7.2</a>, <a href="#G.6.3.2">G.6.3.2</a> compound statement, <a href="#6.8.2">6.8.2</a>
33727 type-generic macro for, <a href="#7.25">7.25</a> compound-literal operator (( ){ }), <a href="#6.5.2.5">6.5.2.5</a>
33729 clog1p function, <a href="#7.31.1">7.31.1</a> string, <a href="#7.24.3">7.24.3</a>, <a href="#K.3.7.2">K.3.7.2</a>
33730 clog2 function, <a href="#7.31.1">7.31.1</a> wide string, <a href="#7.29.4.3">7.29.4.3</a>, <a href="#K.3.9.2.2">K.3.9.2.2</a>
33732 cnd_broadcast function, <a href="#7.26.3.1">7.26.3.1</a>, <a href="#7.26.3.5">7.26.3.5</a>, concatenation
33734 cnd_destroy function, <a href="#7.26.3.2">7.26.3.2</a> conditional features, <a href="#4">4</a>, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a>,
33735 cnd_init function, <a href="#7.26.3.3">7.26.3.3</a> <a href="#7.1.2">7.1.2</a>, <a href="#F.1">F.1</a>, <a href="#G.1">G.1</a>, <a href="#K.2">K.2</a>, <a href="#L.1">L.1</a>
33736 cnd_signal function, <a href="#7.26.3.4">7.26.3.4</a>, <a href="#7.26.3.5">7.26.3.5</a>, conditional inclusion, <a href="#6.10.1">6.10.1</a>
33737 <a href="#7.26.3.6">7.26.3.6</a> conditional operator (? :), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.15">6.5.15</a>
33740 cnd_wait function, <a href="#7.26.3.3">7.26.3.3</a>, <a href="#7.26.3.6">7.26.3.6</a> conj functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a>
33741 collating sequences, <a href="#5.2.1">5.2.1</a> conj type-generic macro, <a href="#7.25">7.25</a>
33742 colon punctuator (:), <a href="#6.7.2.1">6.7.2.1</a> const type qualifier, <a href="#6.7.3">6.7.3</a>
33743 comma operator (,), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.17">6.5.17</a> const-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.7.3">6.7.3</a>
33744 comma punctuator (,), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>, constant expression, <a href="#6.6">6.6</a>, <a href="#F.8.4">F.8.4</a>
33745 <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a> constants, <a href="#6.4.4">6.4.4</a>
33746 command processor, <a href="#7.22.4.8">7.22.4.8</a> as primary expression, <a href="#6.5.1">6.5.1</a>
33747 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> character, <a href="#6.4.4.4">6.4.4.4</a>
33748 comments, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.4.9">6.4.9</a> enumeration, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
33751 common initial sequence, <a href="#6.5.2.3">6.5.2.3</a> integer, <a href="#6.4.4.1">6.4.4.1</a>
33754 comparison functions, <a href="#7.22.5">7.22.5</a>, <a href="#7.22.5.1">7.22.5.1</a>, <a href="#7.22.5.2">7.22.5.2</a>, constraint_handler_t type, <a href="#K.3.6">K.3.6</a>
33755 <a href="#K.3.6.3">K.3.6.3</a>, <a href="#K.3.6.3.1">K.3.6.3.1</a>, <a href="#K.3.6.3.2">K.3.6.3.2</a> consume operation, <a href="#5.1.2.4">5.1.2.4</a>
33756 string, <a href="#7.24.4">7.24.4</a> content of structure/union/enumeration, <a href="#6.7.2.3">6.7.2.3</a>
33757 wide string, <a href="#7.29.4.4">7.29.4.4</a> contiguity of allocated storage, <a href="#7.22.3">7.22.3</a>
33758 comparison macros, <a href="#7.12.14">7.12.14</a> continue statement, <a href="#6.8.6.2">6.8.6.2</a>
33759 comparison, pointer, <a href="#6.5.8">6.5.8</a> contracted expression, <a href="#6.5">6.5</a>, <a href="#7.12.2">7.12.2</a>, <a href="#F.7">F.7</a>
33760 compatible type, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.6">6.7.6</a> control character, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a>
33762 complement operator (~), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a> conversion, <a href="#6.3">6.3</a>
33764 complex arithmetic header, <a href="#7.3">7.3</a>, <a href="#7.31.1">7.31.1</a> array argument, <a href="#6.9.1">6.9.1</a>
33765 <!--page 681 -->
33768 boolean, <a href="#6.3.1.2">6.3.1.2</a> cos functions, <a href="#7.12.4.5">7.12.4.5</a>, <a href="#F.10.1.5">F.10.1.5</a>
33769 boolean, characters, and integers, <a href="#6.3.1.1">6.3.1.1</a> cos type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a>
33770 by assignment, <a href="#6.5.16.1">6.5.16.1</a> cosh functions, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#F.10.2.4">F.10.2.4</a>
33771 by return statement, <a href="#6.8.6.4">6.8.6.4</a> cosh type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a>
33772 complex types, <a href="#6.3.1.6">6.3.1.6</a> cpow functions, <a href="#7.3.8.2">7.3.8.2</a>, <a href="#G.6.4.1">G.6.4.1</a>
33774 function, <a href="#6.3.2.1">6.3.2.1</a> cproj functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a>
33775 function argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> cproj type-generic macro, <a href="#7.25">7.25</a>
33776 function designators, <a href="#6.3.2.1">6.3.2.1</a> creal functions, <a href="#7.3.9.6">7.3.9.6</a>, <a href="#G.6">G.6</a>
33777 function parameter, <a href="#6.9.1">6.9.1</a> creal type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a>
33779 imaginary and complex, <a href="#G.4.3">G.4.3</a> csin functions, <a href="#7.3.5.5">7.3.5.5</a>, <a href="#G.6">G.6</a>
33781 lvalues, <a href="#6.3.2.1">6.3.2.1</a> csinh functions, <a href="#7.3.6.5">7.3.6.5</a>, <a href="#G.6.2.5">G.6.2.5</a>
33782 pointer, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> type-generic macro for, <a href="#7.25">7.25</a>
33783 real and complex, <a href="#6.3.1.7">6.3.1.7</a> csqrt functions, <a href="#7.3.8.3">7.3.8.3</a>, <a href="#G.6.4.2">G.6.4.2</a>
33784 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.25">7.25</a>
33785 real floating and integer, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> ctan functions, <a href="#7.3.5.6">7.3.5.6</a>, <a href="#G.6">G.6</a>
33786 real floating types, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#F.3">F.3</a> type-generic macro for, <a href="#7.25">7.25</a>
33787 signed and unsigned integers, <a href="#6.3.1.3">6.3.1.3</a> ctanh functions, <a href="#7.3.6.6">7.3.6.6</a>, <a href="#G.6.2.6">G.6.2.6</a>
33791 conversion functions ctime_s function, <a href="#K.3.8.2">K.3.8.2</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>
33792 multibyte/wide character, <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a> ctype.h header, <a href="#7.4">7.4</a>, <a href="#7.31.2">7.31.2</a>
33793 extended, <a href="#7.29.6">7.29.6</a>, <a href="#K.3.9.3">K.3.9.3</a> current object, <a href="#6.7.9">6.7.9</a>
33794 restartable, <a href="#7.28.1">7.28.1</a>, <a href="#7.29.6.3">7.29.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a> CX_LIMITED_RANGE pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.3.4">7.3.4</a>
33796 restartable, <a href="#7.29.6.4">7.29.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> data race, <a href="#5.1.2.4">5.1.2.4</a>, <a href="#7.1.4">7.1.4</a>, <a href="#7.22.2.1">7.22.2.1</a>, <a href="#7.22.2.2">7.22.2.2</a>, <a href="#7.22.3">7.22.3</a>,
33797 numeric, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> <a href="#7.22.4.6">7.22.4.6</a>, <a href="#7.24.5.8">7.24.5.8</a>, <a href="#7.24.6.2">7.24.6.2</a>, <a href="#7.27.3">7.27.3</a>, <a href="#7.28.1">7.28.1</a>,
33798 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.29.4.1">7.29.4.1</a> <a href="#7.29.6.3">7.29.6.3</a>, <a href="#7.29.6.4">7.29.6.4</a>, <a href="#K.3.6.2.1">K.3.6.2.1</a>
33800 time, <a href="#7.27.3">7.27.3</a>, <a href="#K.3.8.2">K.3.8.2</a> date and time header, <a href="#7.26.1">7.26.1</a>, <a href="#7.27">7.27</a>, <a href="#7.31.14">7.31.14</a>, <a href="#K.3.8">K.3.8</a>
33801 wide character, <a href="#7.29.5">7.29.5</a> Daylight Saving Time, <a href="#7.27.1">7.27.1</a>
33802 conversion specifier, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, DBL_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33804 conversion state, <a href="#7.22.7">7.22.7</a>, <a href="#7.28.1">7.28.1</a>, <a href="#7.28.1.1">7.28.1.1</a>, DBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33805 <a href="#7.28.1.2">7.28.1.2</a>, <a href="#7.28.1.3">7.28.1.3</a>, <a href="#7.28.1.4">7.28.1.4</a>, <a href="#7.29.6">7.29.6</a>, DBL_HAS_SUBNORM macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33806 <a href="#7.29.6.2.1">7.29.6.2.1</a>, <a href="#7.29.6.3">7.29.6.3</a>, <a href="#7.29.6.3.2">7.29.6.3.2</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>, DBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33807 <a href="#7.29.6.4">7.29.6.4</a>, <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#7.29.6.4.2">7.29.6.4.2</a>, <a href="#K.3.6.4">K.3.6.4</a>, DBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33808 <a href="#K.3.9.3.1">K.3.9.3.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>, DBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33810 conversion state functions, <a href="#7.29.6.2">7.29.6.2</a> DBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33812 string, <a href="#7.24.2">7.24.2</a>, <a href="#K.3.7.1">K.3.7.1</a> DBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33813 wide string, <a href="#7.29.4.2">7.29.4.2</a>, <a href="#K.3.9.2.1">K.3.9.2.1</a> DBL_TRUE_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33814 copysign functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#7.12.11.1">7.12.11.1</a>, <a href="#F.3">F.3</a>, decimal constant, <a href="#6.4.4.1">6.4.4.1</a>
33816 copysign type-generic macro, <a href="#7.25">7.25</a> decimal-point character, <a href="#7.1.1">7.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
33817 <!--page 682 -->
33818 DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#F.2">F.2</a>
33819 <a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#F.5">F.5</a> double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>,
33821 declarations, <a href="#6.7">6.7</a> double-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a>
33822 function, <a href="#6.7.6.3">6.7.6.3</a> double-quote escape sequence (\"), <a href="#6.4.4.4">6.4.4.4</a>,
33823 pointer, <a href="#6.7.6.1">6.7.6.1</a> <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a>
33826 declarator, <a href="#6.7.6">6.7.6</a> EDOM macro, <a href="#7.5">7.5</a>, <a href="#7.12.1">7.12.1</a>, see also domain error
33828 declarator type derivation, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.6">6.7.6</a> EILSEQ macro, <a href="#7.5">7.5</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.28.1.1">7.28.1.1</a>, <a href="#7.28.1.2">7.28.1.2</a>,
33829 decrement operators, see arithmetic operators, <a href="#7.28.1.3">7.28.1.3</a>, <a href="#7.28.1.4">7.28.1.4</a>, <a href="#7.29.3.1">7.29.3.1</a>, <a href="#7.29.3.3">7.29.3.3</a>,
33830 increment and decrement <a href="#7.29.6.3.2">7.29.6.3.2</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>, <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#7.29.6.4.2">7.29.6.4.2</a>,
33833 default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> elif preprocessing directive, <a href="#6.10.1">6.10.1</a>
33834 define preprocessing directive, <a href="#6.10.3">6.10.3</a> ellipsis punctuator (...), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.10.3">6.10.3</a>
33835 defined operator, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.8">6.10.8</a> else preprocessing directive, <a href="#6.10.1">6.10.1</a>
33838 dependency-ordered before, <a href="#5.1.2.4">5.1.2.4</a> encoding error, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
33839 derived declarator types, <a href="#6.2.5">6.2.5</a> <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.21.6.5">7.21.6.5</a>, <a href="#7.21.6.6">7.21.6.6</a>, <a href="#7.21.6.8">7.21.6.8</a>,
33840 derived types, <a href="#6.2.5">6.2.5</a> <a href="#7.21.6.10">7.21.6.10</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.28.1.1">7.28.1.1</a>,
33841 designated initializer, <a href="#6.7.9">6.7.9</a> <a href="#7.28.1.2">7.28.1.2</a>, <a href="#7.28.1.3">7.28.1.3</a>, <a href="#7.28.1.4">7.28.1.4</a>, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.1">7.29.2.1</a>,
33842 destringizing, <a href="#6.10.9">6.10.9</a> <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.2.3">7.29.2.3</a>, <a href="#7.29.2.5">7.29.2.5</a>, <a href="#7.29.2.7">7.29.2.7</a>,
33843 device input/output, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.11">7.29.2.11</a>, <a href="#7.29.3.1">7.29.3.1</a>, <a href="#7.29.3.2">7.29.3.2</a>,
33844 diagnostic message, <a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a> <a href="#7.29.3.3">7.29.3.3</a>, <a href="#7.29.3.4">7.29.3.4</a>, <a href="#7.29.6.3.2">7.29.6.3.2</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>,
33845 diagnostics, <a href="#5.1.1.3">5.1.1.3</a> <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#7.29.6.4.2">7.29.6.4.2</a>, <a href="#K.3.6.5.1">K.3.6.5.1</a>, <a href="#K.3.6.5.2">K.3.6.5.2</a>,
33846 diagnostics header, <a href="#7.2">7.2</a> <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>, <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a>
33848 digit, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> end-of-file indicator, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.1">7.21.7.1</a>,
33849 digraphs, <a href="#6.4.6">6.4.6</a> <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>,
33850 direct input/output functions, <a href="#7.21.8">7.21.8</a> <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.10.1">7.21.10.1</a>, <a href="#7.21.10.2">7.21.10.2</a>, <a href="#7.29.3.1">7.29.3.1</a>,
33854 division assignment operator (/=), <a href="#6.5.16.2">6.5.16.2</a> endif preprocessing directive, <a href="#6.10.1">6.10.1</a>
33855 division operator (/), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a> enum type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.2">6.7.2.2</a>
33857 documentation of implementation, <a href="#4">4</a> enumeration, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.2">6.7.2.2</a>
33858 domain error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#7.12.4.4">7.12.4.4</a>, enumeration constant, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
33859 <a href="#7.12.5.1">7.12.5.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#7.12.6.7">7.12.6.7</a>, enumeration content, <a href="#6.7.2.3">6.7.2.3</a>
33860 <a href="#7.12.6.8">7.12.6.8</a>, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, enumeration members, <a href="#6.7.2.2">6.7.2.2</a>
33861 <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#7.12.9.5">7.12.9.5</a>, enumeration specifiers, <a href="#6.7.2.2">6.7.2.2</a>
33862 <a href="#7.12.9.7">7.12.9.7</a>, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a> enumeration tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
33865 double _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, environment functions, <a href="#7.22.4">7.22.4</a>, <a href="#K.3.6.2">K.3.6.2</a>
33866 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> environment list, <a href="#7.22.4.6">7.22.4.6</a>, <a href="#K.3.6.2.1">K.3.6.2.1</a>
33867 double _Imaginary type, <a href="#G.2">G.2</a> environmental considerations, <a href="#5.2">5.2</a>
33868 double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.2">7.21.6.2</a>, environmental limits, <a href="#5.2.4">5.2.4</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.21.2">7.21.2</a>,
33869 <!--page 683 -->
33870 <a href="#7.21.3">7.21.3</a>, <a href="#7.21.4.4">7.21.4.4</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.22.2.1">7.22.2.1</a>, <a href="#7.22.4.2">7.22.4.2</a>, evaluation format, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#7.12">7.12</a>
33871 <a href="#7.22.4.3">7.22.4.3</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a> evaluation method, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#F.8.5">F.8.5</a>
33872 EOF macro, <a href="#7.4">7.4</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.1">7.21.5.1</a>, <a href="#7.21.5.2">7.21.5.2</a>, evaluation of expression, <a href="#5.1.2.3">5.1.2.3</a>
33873 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.21.6.7">7.21.6.7</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.11">7.21.6.11</a>, evaluation order, see order of evaluation
33874 <a href="#7.21.6.14">7.21.6.14</a>, <a href="#7.21.7.1">7.21.7.1</a>, <a href="#7.21.7.3">7.21.7.3</a>, <a href="#7.21.7.4">7.21.7.4</a>, exceptional condition, <a href="#6.5">6.5</a>
33875 <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.21.7.8">7.21.7.8</a>, <a href="#7.21.7.9">7.21.7.9</a>, excess precision, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>
33876 <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.2.4">7.29.2.4</a>, excess range, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>
33877 <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#7.29.2.10">7.29.2.10</a>, <a href="#7.29.2.12">7.29.2.12</a>, exclusive OR operators
33878 <a href="#7.29.3.4">7.29.3.4</a>, <a href="#7.29.6.1.1">7.29.6.1.1</a>, <a href="#7.29.6.1.2">7.29.6.1.2</a>, <a href="#K.3.5.3.7">K.3.5.3.7</a>, bitwise (^), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a>
33879 <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>, bitwise assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
33880 <a href="#K.3.9.1.5">K.3.9.1.5</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a>, executable program, <a href="#5.1.1.1">5.1.1.1</a>
33882 epoch, <a href="#7.27.2.5">7.27.2.5</a> execution environment, <a href="#5">5</a>, <a href="#5.1.2">5.1.2</a>, see also
33883 equal-sign punctuator (=), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.9">6.7.9</a> environmental limits
33884 equal-to operator, see equality operator execution sequence, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.8">6.8</a>
33885 equality expressions, <a href="#6.5.9">6.5.9</a> exit function, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.22">7.22</a>, <a href="#7.22.4.4">7.22.4.4</a>,
33886 equality operator (==), <a href="#6.5.9">6.5.9</a> <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>, <a href="#7.26.5.5">7.26.5.5</a>
33887 ERANGE macro, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.12.1">7.12.1</a>, EXIT_FAILURE macro, <a href="#7.22">7.22</a>, <a href="#7.22.4.4">7.22.4.4</a>
33888 <a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>, see EXIT_SUCCESS macro, <a href="#7.22">7.22</a>, <a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.26.5.5">7.26.5.5</a>
33889 also range error, pole error exp functions, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#F.10.3.1">F.10.3.1</a>
33890 erf functions, <a href="#7.12.8.1">7.12.8.1</a>, <a href="#F.10.5.1">F.10.5.1</a> exp type-generic macro, <a href="#7.25">7.25</a>
33891 erf type-generic macro, <a href="#7.25">7.25</a> exp2 functions, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#F.10.3.2">F.10.3.2</a>
33892 erfc functions, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#F.10.5.2">F.10.5.2</a> exp2 type-generic macro, <a href="#7.25">7.25</a>
33894 errno macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.3.2">7.3.2</a>, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, expm1 functions, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#F.10.3.3">F.10.3.3</a>
33895 <a href="#7.12.1">7.12.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.10.4">7.21.10.4</a>, expm1 type-generic macro, <a href="#7.25">7.25</a>
33896 <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.24.6.2">7.24.6.2</a>, <a href="#7.28.1.1">7.28.1.1</a>, exponent part, <a href="#6.4.4.2">6.4.4.2</a>
33897 <a href="#7.28.1.2">7.28.1.2</a>, <a href="#7.28.1.3">7.28.1.3</a>, <a href="#7.28.1.4">7.28.1.4</a>, <a href="#7.29.3.1">7.29.3.1</a>, exponential functions
33898 <a href="#7.29.3.3">7.29.3.3</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>, <a href="#7.29.6.3.2">7.29.6.3.2</a>, complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
33899 <a href="#7.29.6.3.3">7.29.6.3.3</a>, <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#7.29.6.4.2">7.29.6.4.2</a>, <a href="#J.5.17">J.5.17</a>, real, <a href="#7.12.6">7.12.6</a>, <a href="#F.10.3">F.10.3</a>
33900 <a href="#K.3.1.3">K.3.1.3</a>, <a href="#K.3.7.4.2">K.3.7.4.2</a> expression, <a href="#6.5">6.5</a>
33901 errno.h header, <a href="#7.5">7.5</a>, <a href="#7.31.3">7.31.3</a>, <a href="#K.3.2">K.3.2</a> assignment, <a href="#6.5.16">6.5.16</a>
33902 errno_t type, <a href="#K.3.2">K.3.2</a>, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.6">K.3.6</a>, <a href="#K.3.6.1.1">K.3.6.1.1</a>, cast, <a href="#6.5.4">6.5.4</a>
33903 <a href="#K.3.7">K.3.7</a>, <a href="#K.3.8">K.3.8</a>, <a href="#K.3.9">K.3.9</a> constant, <a href="#6.6">6.6</a>
33906 encoding, see encoding error order of evaluation, see order of evaluation
33910 error functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.10.5">F.10.5</a> expression statement, <a href="#6.8.3">6.8.3</a>
33911 error indicator, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.1">7.21.7.1</a>, extended alignment, <a href="#6.2.8">6.2.8</a>
33912 <a href="#7.21.7.3">7.21.7.3</a>, <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.21.7.7">7.21.7.7</a>, extended character set, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.1.2">5.2.1.2</a>
33913 <a href="#7.21.7.8">7.21.7.8</a>, <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.10.1">7.21.10.1</a>, <a href="#7.21.10.3">7.21.10.3</a>, extended characters, <a href="#5.2.1">5.2.1</a>
33914 <a href="#7.29.3.1">7.29.3.1</a>, <a href="#7.29.3.3">7.29.3.3</a> extended integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>,
33915 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> <a href="#7.20">7.20</a>
33916 error-handling functions, <a href="#7.21.10">7.21.10</a>, <a href="#7.24.6.2">7.24.6.2</a>, extended multibyte and wide character utilities
33917 <a href="#K.3.7.4.2">K.3.7.4.2</a>, <a href="#K.3.7.4.3">K.3.7.4.3</a> header, <a href="#7.29">7.29</a>, <a href="#7.31.16">7.31.16</a>
33918 errors header, <a href="#7.5">7.5</a>, <a href="#7.31.3">7.31.3</a> extended multibyte/wide character conversion
33919 escape character (\), <a href="#6.4.4.4">6.4.4.4</a> utilities, <a href="#7.29.6">7.29.6</a>, <a href="#K.3.9.3">K.3.9.3</a>
33920 escape sequences, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.11.4">6.11.4</a> extensible wide character case mapping functions,
33921 <!--page 684 -->
33922 <a href="#7.30.3.2">7.30.3.2</a> <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.8.1">7.21.8.1</a>
33923 extensible wide character classification functions, fgetpos function, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.3">7.21.9.3</a>
33924 <a href="#7.30.2.2">7.30.2.2</a> fgets function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.2">7.21.7.2</a>, <a href="#K.3.5.4.1">K.3.5.4.1</a>
33925 extern storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.7.1">6.7.1</a> fgetwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.29.3.1">7.29.3.1</a>,
33927 external identifiers, underscore, <a href="#7.1.3">7.1.3</a> fgetws function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.2">7.29.3.2</a>
33928 external linkage, <a href="#6.2.2">6.2.2</a> field width, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>
33930 external object definitions, <a href="#6.9.2">6.9.2</a> access functions, <a href="#7.21.5">7.21.5</a>, <a href="#K.3.5.2">K.3.5.2</a>
33932 fabs functions, <a href="#7.12.7.2">7.12.7.2</a>, <a href="#F.3">F.3</a>, <a href="#F.10.4.2">F.10.4.2</a> operations, <a href="#7.21.4">7.21.4</a>, <a href="#K.3.5.1">K.3.5.1</a>
33933 fabs type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> position indicator, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>,
33934 false macro, <a href="#7.18">7.18</a> <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.1">7.21.7.1</a>, <a href="#7.21.7.3">7.21.7.3</a>, <a href="#7.21.7.10">7.21.7.10</a>,
33935 fclose function, <a href="#7.21.5.1">7.21.5.1</a> <a href="#7.21.8.1">7.21.8.1</a>, <a href="#7.21.8.2">7.21.8.2</a>, <a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.2">7.21.9.2</a>,
33936 fdim functions, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#F.10.9.1">F.10.9.1</a> <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.9.4">7.21.9.4</a>, <a href="#7.21.9.5">7.21.9.5</a>, <a href="#7.29.3.1">7.29.3.1</a>,
33937 fdim type-generic macro, <a href="#7.25">7.25</a> <a href="#7.29.3.3">7.29.3.3</a>, <a href="#7.29.3.10">7.29.3.10</a>
33938 FE_ALL_EXCEPT macro, <a href="#7.6">7.6</a> positioning functions, <a href="#7.21.9">7.21.9</a>
33939 FE_DFL_ENV macro, <a href="#7.6">7.6</a> file scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.9">6.9</a>
33940 FE_DIVBYZERO macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> FILE type, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>
33941 FE_DOWNWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> FILENAME_MAX macro, <a href="#7.21.1">7.21.1</a>
33942 FE_INEXACT macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> flags, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>, see also floating-point
33943 FE_INVALID macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> status flag
33944 FE_OVERFLOW macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> flexible array member, <a href="#6.7.2.1">6.7.2.1</a>
33945 FE_TONEAREST macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> float _Complex type, <a href="#6.2.5">6.2.5</a>
33946 FE_TOWARDZERO macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> float _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>,
33947 FE_UNDERFLOW macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
33948 FE_UPWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> float _Imaginary type, <a href="#G.2">G.2</a>
33949 feclearexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.1">7.6.2.1</a>, <a href="#F.3">F.3</a> float type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#F.2">F.2</a>
33950 fegetenv function, <a href="#7.6.4.1">7.6.4.1</a>, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a> float type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>,
33951 fegetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.2">7.6.2.2</a>, <a href="#F.3">F.3</a> <a href="#6.3.1.8">6.3.1.8</a>
33952 fegetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.1">7.6.3.1</a>, <a href="#F.3">F.3</a> float.h header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.22.1.3">7.22.1.3</a>,
33953 feholdexcept function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>
33956 fences, <a href="#7.17.4">7.17.4</a> floating suffix, f or <a href="#F">F</a>, <a href="#6.4.4.2">6.4.4.2</a>
33957 fenv.h header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>,
33958 <a href="#7.31.4">7.31.4</a>, <a href="#F">F</a>, <a href="#H">H</a> <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a>
33959 FENV_ACCESS pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.6.1">7.6.1</a>, <a href="#F.8">F.8</a>, <a href="#F.9">F.9</a>, floating types, <a href="#6.2.5">6.2.5</a>, <a href="#6.11.1">6.11.1</a>
33960 <a href="#F.10">F.10</a> floating-point accuracy, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.5">6.5</a>,
33961 fenv_t type, <a href="#7.6">7.6</a> <a href="#7.22.1.3">7.22.1.3</a>, <a href="#F.5">F.5</a>, see also contracted expression
33962 feof function, <a href="#7.21.10.2">7.21.10.2</a> floating-point arithmetic functions, <a href="#7.12">7.12</a>, <a href="#F.10">F.10</a>
33963 feraiseexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.3">7.6.2.3</a>, <a href="#F.3">F.3</a> floating-point classification functions, <a href="#7.12.3">7.12.3</a>
33964 ferror function, <a href="#7.21.10.3">7.21.10.3</a> floating-point control mode, <a href="#7.6">7.6</a>, <a href="#F.8.6">F.8.6</a>
33965 fesetenv function, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#F.3">F.3</a> floating-point environment, <a href="#7.6">7.6</a>, <a href="#F.8">F.8</a>, <a href="#F.8.6">F.8.6</a>
33966 fesetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.4">7.6.2.4</a>, <a href="#F.3">F.3</a> floating-point environment header, <a href="#7.6">7.6</a>, <a href="#7.31.4">7.31.4</a>
33967 fesetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.2">7.6.3.2</a>, <a href="#F.3">F.3</a> floating-point exception, <a href="#7.6">7.6</a>, <a href="#7.6.2">7.6.2</a>, <a href="#F.10">F.10</a>
33968 fetestexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.5">7.6.2.5</a>, <a href="#F.3">F.3</a> floating-point number, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.2.5">6.2.5</a>
33969 feupdateenv function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a> floating-point rounding mode, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33970 fexcept_t type, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> floating-point status flag, <a href="#7.6">7.6</a>, <a href="#F.8.6">F.8.6</a>
33971 fflush function, <a href="#7.21.5.2">7.21.5.2</a>, <a href="#7.21.5.3">7.21.5.3</a> floor functions, <a href="#7.12.9.2">7.12.9.2</a>, <a href="#F.10.6.2">F.10.6.2</a>
33972 fgetc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.7.1">7.21.7.1</a>, floor type-generic macro, <a href="#7.25">7.25</a>
33973 <!--page 685 -->
33974 FLT_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> FP_NAN macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
33975 FLT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> FP_NORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
33976 FLT_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> FP_SUBNORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
33977 FLT_EVAL_METHOD macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.6">6.6</a>, <a href="#7.12">7.12</a>, FP_ZERO macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
33978 <a href="#F.10.11">F.10.11</a> fpclassify macro, <a href="#7.12.3.1">7.12.3.1</a>, <a href="#F.3">F.3</a>
33979 FLT_HAS_SUBNORM macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fpos_t type, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>
33980 FLT_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.1">7.21.6.1</a>,
33981 FLT_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.21.6.5">7.21.6.5</a>, <a href="#7.21.6.6">7.21.6.6</a>,
33982 FLT_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#F.3">F.3</a>, <a href="#K.3.5.3.1">K.3.5.3.1</a>
33983 FLT_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fprintf_s function, <a href="#K.3.5.3.1">K.3.5.3.1</a>
33984 FLT_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fputc function, <a href="#5.2.2">5.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.7.3">7.21.7.3</a>,
33985 FLT_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#7.21.7.7">7.21.7.7</a>, <a href="#7.21.8.2">7.21.8.2</a>
33986 FLT_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fputs function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.4">7.21.7.4</a>
33987 FLT_RADIX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.22.1.3">7.22.1.3</a>, fputwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.29.3.3">7.29.3.3</a>,
33988 <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a> <a href="#7.29.3.8">7.29.3.8</a>
33989 FLT_ROUNDS macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> fputws function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.4">7.29.3.4</a>
33990 FLT_TRUE_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> fread function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.8.1">7.21.8.1</a>
33991 fma functions, <a href="#7.12">7.12</a>, <a href="#7.12.13.1">7.12.13.1</a>, <a href="#F.10.10.1">F.10.10.1</a> free function, <a href="#7.22.3.3">7.22.3.3</a>, <a href="#7.22.3.5">7.22.3.5</a>
33992 fma type-generic macro, <a href="#7.25">7.25</a> freestanding execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>,
33993 fmax functions, <a href="#7.12.12.2">7.12.12.2</a>, <a href="#F.10.9.2">F.10.9.2</a> <a href="#5.1.2.1">5.1.2.1</a>
33994 fmax type-generic macro, <a href="#7.25">7.25</a> freopen function, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.5.4">7.21.5.4</a>
33995 fmin functions, <a href="#7.12.12.3">7.12.12.3</a>, <a href="#F.10.9.3">F.10.9.3</a> freopen_s function, <a href="#K.3.5.2.2">K.3.5.2.2</a>
33996 fmin type-generic macro, <a href="#7.25">7.25</a> frexp functions, <a href="#7.12.6.4">7.12.6.4</a>, <a href="#F.10.3.4">F.10.3.4</a>
33997 fmod functions, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#F.10.7.1">F.10.7.1</a> frexp type-generic macro, <a href="#7.25">7.25</a>
33998 fmod type-generic macro, <a href="#7.25">7.25</a> fscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
33999 fopen function, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.5.4">7.21.5.4</a>, <a href="#K.3.5.2.1">K.3.5.2.1</a> <a href="#7.21.6.4">7.21.6.4</a>, <a href="#7.21.6.7">7.21.6.7</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#F.3">F.3</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>
34000 FOPEN_MAX macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.4.3">7.21.4.3</a>, fscanf_s function, <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.5.3.4">K.3.5.3.4</a>,
34001 <a href="#K.3.5.1.1">K.3.5.1.1</a> <a href="#K.3.5.3.7">K.3.5.3.7</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>
34002 fopen_s function, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.2.1">K.3.5.2.1</a>, fseek function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.10">7.21.7.10</a>,
34003 <a href="#K.3.5.2.2">K.3.5.2.2</a> <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.9.4">7.21.9.4</a>, <a href="#7.21.9.5">7.21.9.5</a>, <a href="#7.29.3.10">7.29.3.10</a>
34004 for statement, <a href="#6.8.5">6.8.5</a>, <a href="#6.8.5.3">6.8.5.3</a> fsetpos function, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.10">7.21.7.10</a>,
34005 form-feed character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> <a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.29.3.10">7.29.3.10</a>
34006 form-feed escape sequence (\f), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, ftell function, <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.9.4">7.21.9.4</a>
34008 formal argument (deprecated), <a href="#3.16">3.16</a> full expression, <a href="#6.8">6.8</a>
34009 formal parameter, <a href="#3.16">3.16</a> fully buffered stream, <a href="#7.21.3">7.21.3</a>
34011 <a href="#7.31.5">7.31.5</a> argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
34012 formatted input/output functions, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.6">7.21.6</a>, body, <a href="#6.9.1">6.9.1</a>
34014 wide character, <a href="#7.29.2">7.29.2</a>, <a href="#K.3.9.1">K.3.9.1</a> library, <a href="#7.1.4">7.1.4</a>
34015 fortran keyword, <a href="#J.5.9">J.5.9</a> declarator, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.11.6">6.11.6</a>
34016 forward reference, <a href="#3.11">3.11</a> definition, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.7">6.11.7</a>
34017 FP_CONTRACT pragma, <a href="#6.5">6.5</a>, <a href="#6.10.6">6.10.6</a>, <a href="#7.12.2">7.12.2</a>, see designator, <a href="#6.3.2.1">6.3.2.1</a>
34020 FP_FAST_FMAF macro, <a href="#7.12">7.12</a> library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.4">7.1.4</a>
34021 FP_FAST_FMAL macro, <a href="#7.12">7.12</a> name length, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a>
34022 FP_ILOGB0 macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a> no-return, <a href="#6.7.4">6.7.4</a>
34023 FP_ILOGBNAN macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a> parameter, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a>
34024 FP_INFINITE macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> prototype, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.7">6.2.7</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>,
34025 <!--page 686 -->
34026 <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.6">6.11.6</a>, <a href="#6.11.7">6.11.7</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.12">7.12</a> header, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.2">7.1.2</a>, see also standard headers
34027 prototype scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.7.6.2">6.7.6.2</a> header names, <a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>, <a href="#6.10.2">6.10.2</a>
34028 recursive call, <a href="#6.5.2.2">6.5.2.2</a> hexadecimal constant, <a href="#6.4.4.1">6.4.4.1</a>
34029 return, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a> hexadecimal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
34032 type conversion, <a href="#6.3.2.1">6.3.2.1</a> (\x hexadecimal digits), <a href="#6.4.4.4">6.4.4.4</a>
34034 function type, <a href="#6.2.5">6.2.5</a> horizontal-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
34035 function-call operator (( )), <a href="#6.5.2.2">6.5.2.2</a> horizontal-tab escape sequence (\r), <a href="#7.30.2.1.3">7.30.2.1.3</a>
34036 function-like macro, <a href="#6.10.3">6.10.3</a> horizontal-tab escape sequence (\t), <a href="#5.2.2">5.2.2</a>,
34037 fundamental alignment, <a href="#6.2.8">6.2.8</a> <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a>
34038 future directions hosted execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.2">5.1.2.2</a>
34039 language, <a href="#6.11">6.11</a> HUGE_VAL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.22.1.3">7.22.1.3</a>,
34040 library, <a href="#7.31">7.31</a> <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#F.10">F.10</a>
34041 fwide function, <a href="#7.21.2">7.21.2</a>, <a href="#7.29.3.5">7.29.3.5</a> HUGE_VALF macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.22.1.3">7.22.1.3</a>,
34042 fwprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#F.10">F.10</a>
34043 <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.2.3">7.29.2.3</a>, <a href="#7.29.2.5">7.29.2.5</a>, HUGE_VALL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.22.1.3">7.22.1.3</a>,
34044 <a href="#7.29.2.11">7.29.2.11</a>, <a href="#K.3.9.1.1">K.3.9.1.1</a> <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#F.10">F.10</a>
34046 fwrite function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.8.2">7.21.8.2</a> complex, <a href="#7.3.6">7.3.6</a>, <a href="#G.6.2">G.6.2</a>
34047 fwscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, real, <a href="#7.12.5">7.12.5</a>, <a href="#F.10.2">F.10.2</a>
34048 <a href="#7.29.2.4">7.29.2.4</a>, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.12">7.29.2.12</a>, <a href="#7.29.3.10">7.29.3.10</a>, hypot functions, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#F.10.4.3">F.10.4.3</a>
34051 <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.14">K.3.9.1.14</a> <a href="#I">I</a> macro, <a href="#7.3.1">7.3.1</a>, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a>
34053 gamma functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.10.5">F.10.5</a> linkage, see linkage
34055 wide string, <a href="#7.29.4">7.29.4</a>, <a href="#K.3.9.2">K.3.9.2</a> name spaces, <a href="#6.2.3">6.2.3</a>
34056 general utilities header, <a href="#7.22">7.22</a>, <a href="#7.31.12">7.31.12</a> reserved, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a>, <a href="#K.3.1.2">K.3.1.2</a>
34057 general wide string utilities, <a href="#7.29.4">7.29.4</a>, <a href="#K.3.9.2">K.3.9.2</a> scope, <a href="#6.2.1">6.2.1</a>
34060 generic selection, <a href="#6.5.1">6.5.1</a>, <a href="#6.5.1.1">6.5.1.1</a> identifier nondigit, <a href="#6.4.2.1">6.4.2.1</a>
34061 getc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a> IEC 559, <a href="#F.1">F.1</a>
34062 getchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.6">7.21.7.6</a> IEC 60559, <a href="#2">2</a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.3.3">7.3.3</a>,
34063 getenv function, <a href="#7.22.4.6">7.22.4.6</a> <a href="#7.6">7.6</a>, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.14">7.12.14</a>, <a href="#F">F</a>, <a href="#G">G</a>,
34067 getwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.6">7.29.3.6</a>, <a href="#7.29.3.7">7.29.3.7</a> IEEE floating-point arithmetic standard, see
34068 getwchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.7">7.29.3.7</a> IEC 60559, ANSI/IEEE 754,
34070 gmtime_s function, <a href="#K.3.8.2.3">K.3.8.2.3</a> if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>,
34071 goto statement, <a href="#6.2.1">6.2.1</a>, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.6.1">6.8.6.1</a> <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a>
34073 greater-than operator (>), <a href="#6.5.8">6.5.8</a> ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a>
34074 greater-than-or-equal-to operator (>=), <a href="#6.5.8">6.5.8</a> ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a>
34076 happens before, <a href="#5.1.2.4">5.1.2.4</a> ilogb functions, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.10.3.5">F.10.3.5</a>
34077 <!--page 687 -->
34078 ilogb type-generic macro, <a href="#7.25">7.25</a> formatted, <a href="#7.29.2">7.29.2</a>, <a href="#K.3.9.1">K.3.9.1</a>
34079 imaginary macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a> input/output header, <a href="#7.21">7.21</a>, <a href="#7.31.11">7.31.11</a>, <a href="#K.3.5">K.3.5</a>
34081 imaginary type domain, <a href="#G.2">G.2</a> int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.7.2">6.7.2</a>
34082 imaginary types, <a href="#G">G</a> int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
34084 imaxdiv function, <a href="#7.8">7.8</a>, <a href="#7.8.2.2">7.8.2.2</a> INT_FASTN_MAX macros, <a href="#7.20.2.3">7.20.2.3</a>
34087 implementation limit, <a href="#3.13">3.13</a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.4.2.1">6.4.2.1</a>, INT_LEASTN_MAX macros, <a href="#7.20.2.2">7.20.2.2</a>
34088 <a href="#6.7.6">6.7.6</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#E">E</a>, see also environmental INT_LEASTN_MIN macros, <a href="#7.20.2.2">7.20.2.2</a>
34090 implementation-defined behavior, <a href="#3.4.1">3.4.1</a>, <a href="#4">4</a>, <a href="#J.3">J.3</a> INT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
34091 implementation-defined value, <a href="#3.19.1">3.19.1</a> INT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>
34092 implicit conversion, <a href="#6.3">6.3</a> integer arithmetic functions, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>,
34094 include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.2">6.10.2</a> integer character constant, <a href="#6.4.4.4">6.4.4.4</a>
34096 bitwise (|), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a> integer constant expression, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.6">6.6</a>, <a href="#6.7.2.1">6.7.2.1</a>,
34097 bitwise assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.7.10">6.7.10</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#6.10.1">6.10.1</a>,
34099 increment operators, see arithmetic operators, integer conversion rank, <a href="#6.3.1.1">6.3.1.1</a>
34100 increment and decrement integer promotions, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.3.1.1">6.3.1.1</a>,
34101 indeterminate value, <a href="#3.19.2">3.19.2</a> <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.3.3">6.5.3.3</a>, <a href="#6.5.7">6.5.7</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#7.20.2">7.20.2</a>, <a href="#7.20.3">7.20.3</a>,
34102 indeterminately sequenced, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>
34103 <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.16.2">6.5.16.2</a>, see also sequenced before, integer suffix, <a href="#6.4.4.1">6.4.4.1</a>
34104 unsequenced integer type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
34105 indirection operator (*), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a>
34106 inequality operator (!=), <a href="#6.5.9">6.5.9</a> integer types, <a href="#6.2.5">6.2.5</a>, <a href="#7.20">7.20</a>
34107 infinitary, <a href="#7.12.1">7.12.1</a> extended, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#7.20">7.20</a>
34108 INFINITY macro, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> integer types header, <a href="#7.20">7.20</a>, <a href="#7.31.10">7.31.10</a>
34109 initial position, <a href="#5.2.2">5.2.2</a> inter-thread happens before, <a href="#5.1.2.4">5.1.2.4</a>
34110 initial shift state, <a href="#5.2.1.2">5.2.1.2</a> interactive device, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.3">7.21.5.3</a>
34111 initialization, <a href="#5.1.2">5.1.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.5">6.5.2.5</a>, <a href="#6.7.9">6.7.9</a>, internal linkage, <a href="#6.2.2">6.2.2</a>
34115 permitted form, <a href="#6.6">6.6</a> INTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.2.5">7.20.2.5</a>
34116 string literal, <a href="#6.3.2.1">6.3.2.1</a> INTMAX_MIN macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.2.5">7.20.2.5</a>
34117 inline, <a href="#6.7.4">6.7.4</a> intmax_t type, <a href="#7.20.1.5">7.20.1.5</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
34118 inner scope, <a href="#6.2.1">6.2.1</a> <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>
34119 input failure, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#7.29.2.10">7.29.2.10</a>, INTN_C macros, <a href="#7.20.4.1">7.20.4.1</a>
34120 <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.5.3.4">K.3.5.3.4</a>, <a href="#K.3.5.3.7">K.3.5.3.7</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>, INTN_MAX macros, <a href="#7.20.2.1">7.20.2.1</a>
34121 <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>, <a href="#K.3.9.1.5">K.3.9.1.5</a>, INTN_MIN macros, <a href="#7.20.2.1">7.20.2.1</a>
34122 <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a>, <a href="#K.3.9.1.14">K.3.9.1.14</a> intN_t types, <a href="#7.20.1.1">7.20.1.1</a>
34124 character, <a href="#7.21.7">7.21.7</a>, <a href="#K.3.5.4">K.3.5.4</a> INTPTR_MIN macro, <a href="#7.20.2.4">7.20.2.4</a>
34126 formatted, <a href="#7.21.6">7.21.6</a>, <a href="#K.3.5.3">K.3.5.3</a> inttypes.h header, <a href="#7.8">7.8</a>, <a href="#7.31.5">7.31.5</a>
34127 wide character, <a href="#7.29.2">7.29.2</a>, <a href="#K.3.9.1">K.3.9.1</a> isalnum function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.9">7.4.1.9</a>, <a href="#7.4.1.10">7.4.1.10</a>
34128 wide character, <a href="#7.29.3">7.29.3</a> isalpha function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a>
34129 <!--page 688 -->
34130 isblank function, <a href="#7.4.1.3">7.4.1.3</a> iswpunct function, <a href="#7.30.2.1">7.30.2.1</a>, <a href="#7.30.2.1.2">7.30.2.1.2</a>,
34131 iscntrl function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.4">7.4.1.4</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.30.2.1.7">7.30.2.1.7</a>, <a href="#7.30.2.1.9">7.30.2.1.9</a>, <a href="#7.30.2.1.10">7.30.2.1.10</a>,
34132 <a href="#7.4.1.11">7.4.1.11</a> <a href="#7.30.2.1.11">7.30.2.1.11</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a>
34133 isdigit function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.5">7.4.1.5</a>, iswspace function, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>,
34134 <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.11.1.1">7.11.1.1</a> <a href="#7.29.4.1.1">7.29.4.1.1</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>, <a href="#7.30.2.1.2">7.30.2.1.2</a>, <a href="#7.30.2.1.6">7.30.2.1.6</a>,
34135 isfinite macro, <a href="#7.12.3.2">7.12.3.2</a>, <a href="#F.3">F.3</a> <a href="#7.30.2.1.7">7.30.2.1.7</a>, <a href="#7.30.2.1.9">7.30.2.1.9</a>, <a href="#7.30.2.1.10">7.30.2.1.10</a>,
34136 isgraph function, <a href="#7.4.1.6">7.4.1.6</a> <a href="#7.30.2.1.11">7.30.2.1.11</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a>
34137 isgreater macro, <a href="#7.12.14.1">7.12.14.1</a>, <a href="#F.3">F.3</a> iswupper function, <a href="#7.30.2.1.2">7.30.2.1.2</a>, <a href="#7.30.2.1.11">7.30.2.1.11</a>,
34138 isgreaterequal macro, <a href="#7.12.14.2">7.12.14.2</a>, <a href="#F.3">F.3</a> <a href="#7.30.2.2.1">7.30.2.2.1</a>, <a href="#7.30.3.1.1">7.30.3.1.1</a>, <a href="#7.30.3.1.2">7.30.3.1.2</a>
34139 isinf macro, <a href="#7.12.3.3">7.12.3.3</a> iswxdigit function, <a href="#7.30.2.1.12">7.30.2.1.12</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a>
34140 isless macro, <a href="#7.12.14.3">7.12.14.3</a>, <a href="#F.3">F.3</a> isxdigit function, <a href="#7.4.1.12">7.4.1.12</a>, <a href="#7.11.1.1">7.11.1.1</a>
34141 islessequal macro, <a href="#7.12.14.4">7.12.14.4</a>, <a href="#F.3">F.3</a> italic type convention, <a href="#3">3</a>, <a href="#6.1">6.1</a>
34142 islessgreater macro, <a href="#7.12.14.5">7.12.14.5</a>, <a href="#F.3">F.3</a> iteration statements, <a href="#6.8.5">6.8.5</a>
34143 islower function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.2.1">7.4.2.1</a>,
34145 isnan macro, <a href="#7.12.3.4">7.12.3.4</a>, <a href="#F.3">F.3</a> jump statements, <a href="#6.8.6">6.8.6</a>
34147 ISO 31-11, <a href="#2">2</a>, <a href="#3">3</a> keywords, <a href="#6.4.1">6.4.1</a>, <a href="#G.2">G.2</a>, <a href="#J.5.9">J.5.9</a>, <a href="#J.5.10">J.5.10</a>
34148 ISO 4217, <a href="#2">2</a>, <a href="#7.11.2.1">7.11.2.1</a> kill_dependency macro, <a href="#5.1.2.4">5.1.2.4</a>, <a href="#7.17.3.1">7.17.3.1</a>
34149 ISO 8601, <a href="#2">2</a>, <a href="#7.27.3.5">7.27.3.5</a> known constant size, <a href="#6.2.5">6.2.5</a>
34150 ISO/IEC 10646, <a href="#2">2</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.4.3">6.4.3</a>, <a href="#6.10.8.2">6.10.8.2</a>
34151 ISO/IEC 10976-1, <a href="#H.1">H.1</a> L_tmpnam macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.4.4">7.21.4.4</a>
34152 ISO/IEC 2382-1, <a href="#2">2</a>, <a href="#3">3</a> L_tmpnam_s macro, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
34153 ISO/IEC 646, <a href="#2">2</a>, <a href="#5.2.1.1">5.2.1.1</a> label name, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.3">6.2.3</a>
34155 iso646.h header, <a href="#4">4</a>, <a href="#7.9">7.9</a> labs function, <a href="#7.22.6.1">7.22.6.1</a>
34156 isprint function, <a href="#5.2.2">5.2.2</a>, <a href="#7.4.1.8">7.4.1.8</a> language, <a href="#6">6</a>
34157 ispunct function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, future directions, <a href="#6.11">6.11</a>
34159 isspace function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, Latin alphabet, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
34160 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.3">7.22.1.3</a>, LC_ALL macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
34161 <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.2.2">7.29.2.2</a> LC_COLLATE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.24.4.3">7.24.4.3</a>,
34162 isunordered macro, <a href="#7.12.14.6">7.12.14.6</a>, <a href="#F.3">F.3</a> <a href="#7.29.4.4.2">7.29.4.4.2</a>
34163 isupper function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.4.2.1">7.4.2.1</a>, LC_CTYPE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.22">7.22</a>, <a href="#7.22.7">7.22.7</a>,
34164 <a href="#7.4.2.2">7.4.2.2</a> <a href="#7.22.8">7.22.8</a>, <a href="#7.29.6">7.29.6</a>, <a href="#7.30.1">7.30.1</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a>, <a href="#7.30.2.2.2">7.30.2.2.2</a>,
34165 iswalnum function, <a href="#7.30.2.1.1">7.30.2.1.1</a>, <a href="#7.30.2.1.9">7.30.2.1.9</a>, <a href="#7.30.3.2.1">7.30.3.2.1</a>, <a href="#7.30.3.2.2">7.30.3.2.2</a>, <a href="#K.3.6.4">K.3.6.4</a>, <a href="#K.3.6.5">K.3.6.5</a>
34166 <a href="#7.30.2.1.10">7.30.2.1.10</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a> LC_MONETARY macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
34167 iswalpha function, <a href="#7.30.2.1.1">7.30.2.1.1</a>, <a href="#7.30.2.1.2">7.30.2.1.2</a>, LC_NUMERIC macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
34168 <a href="#7.30.2.2.1">7.30.2.2.1</a> LC_TIME macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.27.3.5">7.27.3.5</a>
34169 iswblank function, <a href="#7.30.2.1.3">7.30.2.1.3</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a> lconv structure type, <a href="#7.11">7.11</a>
34170 iswcntrl function, <a href="#7.30.2.1.2">7.30.2.1.2</a>, <a href="#7.30.2.1.4">7.30.2.1.4</a>, LDBL_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34171 <a href="#7.30.2.1.7">7.30.2.1.7</a>, <a href="#7.30.2.1.11">7.30.2.1.11</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a> LDBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34172 iswctype function, <a href="#7.30.2.2.1">7.30.2.2.1</a>, <a href="#7.30.2.2.2">7.30.2.2.2</a> LDBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34173 iswdigit function, <a href="#7.30.2.1.1">7.30.2.1.1</a>, <a href="#7.30.2.1.2">7.30.2.1.2</a>, LDBL_HAS_SUBNORM macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34174 <a href="#7.30.2.1.5">7.30.2.1.5</a>, <a href="#7.30.2.1.7">7.30.2.1.7</a>, <a href="#7.30.2.1.11">7.30.2.1.11</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a> LDBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34175 iswgraph function, <a href="#7.30.2.1">7.30.2.1</a>, <a href="#7.30.2.1.6">7.30.2.1.6</a>, LDBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34176 <a href="#7.30.2.1.10">7.30.2.1.10</a>, <a href="#7.30.2.2.1">7.30.2.2.1</a> LDBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34177 iswlower function, <a href="#7.30.2.1.2">7.30.2.1.2</a>, <a href="#7.30.2.1.7">7.30.2.1.7</a>, LDBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34178 <a href="#7.30.2.2.1">7.30.2.2.1</a>, <a href="#7.30.3.1.1">7.30.3.1.1</a>, <a href="#7.30.3.1.2">7.30.3.1.2</a> LDBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34179 iswprint function, <a href="#7.30.2.1.6">7.30.2.1.6</a>, <a href="#7.30.2.1.8">7.30.2.1.8</a>, LDBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34181 <!--page 689 -->
34182 LDBL_TRUE_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.10.6.7">F.10.6.7</a>
34183 ldexp functions, <a href="#7.12.6.6">7.12.6.6</a>, <a href="#F.10.3.6">F.10.3.6</a> llround type-generic macro, <a href="#7.25">7.25</a>
34186 ldiv_t type, <a href="#7.22">7.22</a> locale-specific behavior, <a href="#3.4.2">3.4.2</a>, <a href="#J.4">J.4</a>
34187 leading underscore in identifiers, <a href="#7.1.3">7.1.3</a> locale.h header, <a href="#7.11">7.11</a>, <a href="#7.31.6">7.31.6</a>
34188 left-shift assignment operator (<<=), <a href="#6.5.16.2">6.5.16.2</a> localeconv function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
34189 left-shift operator (<<), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a> localization header, <a href="#7.11">7.11</a>, <a href="#7.31.6">7.31.6</a>
34191 external name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> localtime_s function, <a href="#K.3.8.2.4">K.3.8.2.4</a>
34192 function name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> log functions, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#F.10.3.7">F.10.3.7</a>
34194 internal name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a> log10 functions, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#F.10.3.8">F.10.3.8</a>
34195 length function, <a href="#7.22.7.1">7.22.7.1</a>, <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.29.4.6.1">7.29.4.6.1</a>, log10 type-generic macro, <a href="#7.25">7.25</a>
34196 <a href="#7.29.6.3.1">7.29.6.3.1</a>, <a href="#K.3.7.4.4">K.3.7.4.4</a>, <a href="#K.3.9.2.4.1">K.3.9.2.4.1</a> log1p functions, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#F.10.3.9">F.10.3.9</a>
34197 length modifier, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, log1p type-generic macro, <a href="#7.25">7.25</a>
34198 <a href="#7.29.2.2">7.29.2.2</a> log2 functions, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#F.10.3.10">F.10.3.10</a>
34199 less-than operator (<), <a href="#6.5.8">6.5.8</a> log2 type-generic macro, <a href="#7.25">7.25</a>
34201 letter, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
34202 lexical elements, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a> real, <a href="#7.12.6">7.12.6</a>, <a href="#F.10.3">F.10.3</a>
34203 lgamma functions, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#F.10.5.3">F.10.5.3</a> logb functions, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#F.3">F.3</a>, <a href="#F.10.3.11">F.10.3.11</a>
34204 lgamma type-generic macro, <a href="#7.25">7.25</a> logb type-generic macro, <a href="#7.25">7.25</a>
34205 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7">7</a>, <a href="#K.3">K.3</a> logical operators
34206 future directions, <a href="#7.31">7.31</a> AND (&&), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a>
34208 terms, <a href="#7.1.1">7.1.1</a> OR (||), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a>
34209 use of functions, <a href="#7.1.4">7.1.4</a> logical source lines, <a href="#5.1.1.2">5.1.1.2</a>
34211 limits long double _Complex type conversion,
34212 environmental, see environmental limits <a href="#6.3.1.6">6.3.1.6</a>, <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
34214 numerical, see numerical limits long double suffix, l or <a href="#L">L</a>, <a href="#6.4.4.2">6.4.4.2</a>
34215 translation, see translation limits long double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>,
34216 limits.h header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a> <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#F.2">F.2</a>
34217 line buffered stream, <a href="#7.21.3">7.21.3</a> long double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>,
34218 line number, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8.1">6.10.8.1</a> <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
34219 line preprocessing directive, <a href="#6.10.4">6.10.4</a> long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.1">7.21.6.1</a>,
34220 lines, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#7.21.2">7.21.2</a> <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>
34221 preprocessing directive, <a href="#6.10">6.10</a> long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
34222 linkage, <a href="#6.2.2">6.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.4">6.7.4</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.9">6.9</a>, <a href="#6.9.2">6.9.2</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
34223 <a href="#6.11.2">6.11.2</a> long integer suffix, l or <a href="#L">L</a>, <a href="#6.4.4.1">6.4.4.1</a>
34224 llabs function, <a href="#7.22.6.1">7.22.6.1</a> long long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>,
34225 lldiv function, <a href="#7.22.6.2">7.22.6.2</a> <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>
34226 lldiv_t type, <a href="#7.22">7.22</a> long long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>,
34227 LLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
34228 <a href="#7.29.4.1.2">7.29.4.1.2</a> long long integer suffix, ll or LL, <a href="#6.4.4.1">6.4.4.1</a>
34229 LLONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, LONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>
34230 <a href="#7.29.4.1.2">7.29.4.1.2</a> LONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>
34231 llrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10.6.5">F.10.6.5</a> longjmp function, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>, <a href="#7.22.4.4">7.22.4.4</a>,
34233 <!--page 690 -->
34234 loop body, <a href="#6.8.5">6.8.5</a> <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.6.3.1">7.29.6.3.1</a>, <a href="#7.29.6.3.2">7.29.6.3.2</a>,
34235 low-order bit, <a href="#3.6">3.6</a> <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#K.3.6.5.1">K.3.6.5.1</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>
34236 lowercase letter, <a href="#5.2.1">5.2.1</a> mbsinit function, <a href="#7.29.6.2.1">7.29.6.2.1</a>
34237 lrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10.6.5">F.10.6.5</a> mbsrtowcs function, <a href="#7.29.6.4.1">7.29.6.4.1</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>
34238 lrint type-generic macro, <a href="#7.25">7.25</a> mbsrtowcs_s function, <a href="#K.3.9.3.2">K.3.9.3.2</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>
34239 lround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.10.6.7">F.10.6.7</a> mbstate_t type, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.1">7.21.6.1</a>,
34240 lround type-generic macro, <a href="#7.25">7.25</a> <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28">7.28</a>, <a href="#7.28.1">7.28.1</a>, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.1">7.29.2.1</a>,
34241 lvalue, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.3.1">6.5.3.1</a>, <a href="#6.5.16">6.5.16</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.6">7.29.6</a>, <a href="#7.29.6.2.1">7.29.6.2.1</a>, <a href="#7.29.6.3">7.29.6.3</a>,
34242 <a href="#6.7.2.4">6.7.2.4</a> <a href="#7.29.6.3.1">7.29.6.3.1</a>, <a href="#7.29.6.4">7.29.6.4</a>
34243 lvalue conversion, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a>, <a href="#6.5.16.1">6.5.16.1</a>, mbstowcs function, <a href="#6.4.5">6.4.5</a>, <a href="#7.22.8.1">7.22.8.1</a>, <a href="#7.29.6.4">7.29.6.4</a>
34245 mbtowc function, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.22.7.1">7.22.7.1</a>, <a href="#7.22.7.2">7.22.7.2</a>,
34246 macro argument substitution, <a href="#6.10.3.1">6.10.3.1</a> <a href="#7.22.8.1">7.22.8.1</a>, <a href="#7.29.6.3">7.29.6.3</a>
34249 macro invocation, <a href="#6.10.3">6.10.3</a> memchr function, <a href="#7.24.5.1">7.24.5.1</a>
34250 macro name, <a href="#6.10.3">6.10.3</a> memcmp function, <a href="#7.24.4">7.24.4</a>, <a href="#7.24.4.1">7.24.4.1</a>
34252 predefined, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a> memcpy_s function, <a href="#K.3.7.1.1">K.3.7.1.1</a>
34254 scope, <a href="#6.10.3.5">6.10.3.5</a> memmove_s function, <a href="#K.3.7.1.2">K.3.7.1.2</a>
34256 macro preprocessor, <a href="#6.10">6.10</a> memory management functions, <a href="#7.22.3">7.22.3</a>
34257 macro replacement, <a href="#6.10.3">6.10.3</a> memory_order type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.3">7.17.3</a>
34258 magnitude, complex, <a href="#7.3.8.1">7.3.8.1</a> memset function, <a href="#7.24.6.1">7.24.6.1</a>, <a href="#K.3.7.4.1">K.3.7.4.1</a>
34259 main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#6.7.3.1">6.7.3.1</a>, <a href="#6.7.4">6.7.4</a>, memset_s function, <a href="#K.3.7.4.1">K.3.7.4.1</a>
34260 <a href="#7.21.3">7.21.3</a> minimum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.10.9">F.10.9</a>
34261 malloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.4">7.22.3.4</a>, <a href="#7.22.3.5">7.22.3.5</a> minus operator, unary, <a href="#6.5.3.3">6.5.3.3</a>
34262 manipulation functions miscellaneous functions
34263 complex, <a href="#7.3.9">7.3.9</a> string, <a href="#7.24.6">7.24.6</a>, <a href="#K.3.7.4">K.3.7.4</a>
34264 real, <a href="#7.12.11">7.12.11</a>, <a href="#F.10.8">F.10.8</a> wide string, <a href="#7.29.4.6">7.29.4.6</a>, <a href="#K.3.9.2.4">K.3.9.2.4</a>
34265 matching failure, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#7.29.2.10">7.29.2.10</a>, mktime function, <a href="#7.27.2.3">7.27.2.3</a>
34266 <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a> modf functions, <a href="#7.12.6.12">7.12.6.12</a>, <a href="#F.10.3.12">F.10.3.12</a>
34267 math.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.25">7.25</a>, <a href="#F">F</a>, modifiable lvalue, <a href="#6.3.2.1">6.3.2.1</a>
34268 <a href="#F.10">F.10</a>, <a href="#J.5.17">J.5.17</a> modification order, <a href="#5.1.2.4">5.1.2.4</a>
34269 MATH_ERREXCEPT macro, <a href="#7.12">7.12</a>, <a href="#F.10">F.10</a> modulus functions, <a href="#7.12.6.12">7.12.6.12</a>
34270 math_errhandling macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.12">7.12</a>, <a href="#F.10">F.10</a> modulus, complex, <a href="#7.3.8.1">7.3.8.1</a>
34271 MATH_ERRNO macro, <a href="#7.12">7.12</a> mtx_destroy function, <a href="#7.26.4.1">7.26.4.1</a>
34272 mathematics header, <a href="#7.12">7.12</a> mtx_init function, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.4.2">7.26.4.2</a>
34273 max_align_t type, <a href="#7.19">7.19</a> mtx_lock function, <a href="#7.26.4.3">7.26.4.3</a>
34275 maximum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.10.9">F.10.9</a> mtx_timedlock function, <a href="#7.26.4.4">7.26.4.4</a>
34276 MB_CUR_MAX macro, <a href="#7.1.1">7.1.1</a>, <a href="#7.22">7.22</a>, <a href="#7.22.7.2">7.22.7.2</a>, mtx_trylock function, <a href="#7.26.4.5">7.26.4.5</a>
34277 <a href="#7.22.7.3">7.22.7.3</a>, <a href="#7.28.1.2">7.28.1.2</a>, <a href="#7.28.1.4">7.28.1.4</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>, mtx_unlock function, <a href="#7.26.4.3">7.26.4.3</a>, <a href="#7.26.4.4">7.26.4.4</a>,
34278 <a href="#K.3.6.4.1">K.3.6.4.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a> <a href="#7.26.4.5">7.26.4.5</a>, <a href="#7.26.4.6">7.26.4.6</a>
34279 MB_LEN_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.1.1">7.1.1</a>, <a href="#7.22">7.22</a> multibyte character, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
34280 mblen function, <a href="#7.22.7.1">7.22.7.1</a>, <a href="#7.29.6.3">7.29.6.3</a> multibyte conversion functions
34281 mbrlen function, <a href="#7.29.6.3.1">7.29.6.3.1</a> wide character, <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a>
34282 mbrtoc16 function, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.28.1.1">7.28.1.1</a> extended, <a href="#7.29.6">7.29.6</a>, <a href="#K.3.9.3">K.3.9.3</a>
34283 mbrtoc32 function, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.28.1.3">7.28.1.3</a> restartable, <a href="#7.28.1">7.28.1</a>, <a href="#7.29.6.3">7.29.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a>
34284 mbrtowc function, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, wide string, <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a>
34285 <!--page 691 -->
34286 restartable, <a href="#7.29.6.4">7.29.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> not macro, <a href="#7.9">7.9</a>
34289 <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a> null character (\0), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>
34290 extended, <a href="#7.29.6">7.29.6</a>, <a href="#K.3.9.3">K.3.9.3</a> padding of binary stream, <a href="#7.21.2">7.21.2</a>
34291 restartable, <a href="#7.28.1">7.28.1</a>, <a href="#7.29.6.3">7.29.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a> NULL macro, <a href="#7.11">7.11</a>, <a href="#7.19">7.19</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.22">7.22</a>, <a href="#7.24.1">7.24.1</a>,
34292 multibyte/wide string conversion functions, <a href="#7.27.1">7.27.1</a>, <a href="#7.29.1">7.29.1</a>
34293 <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a> null pointer, <a href="#6.3.2.3">6.3.2.3</a>
34294 restartable, <a href="#7.29.6.4">7.29.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> null pointer constant, <a href="#6.3.2.3">6.3.2.3</a>
34295 multidimensional array, <a href="#6.5.2.1">6.5.2.1</a> null preprocessing directive, <a href="#6.10.7">6.10.7</a>
34296 multiplication assignment operator (*=), <a href="#6.5.16.2">6.5.16.2</a> null statement, <a href="#6.8.3">6.8.3</a>
34297 multiplication operator (*), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, null wide character, <a href="#7.1.1">7.1.1</a>
34298 <a href="#G.5.1">G.5.1</a> number classification macros, <a href="#7.12">7.12</a>, <a href="#7.12.3.1">7.12.3.1</a>
34299 multiplicative expressions, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a> numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a>
34301 n-char sequence, <a href="#7.22.1.3">7.22.1.3</a> numerical limits, <a href="#5.2.4.2">5.2.4.2</a>
34304 external, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> object representation, <a href="#6.2.6.1">6.2.6.1</a>
34306 internal, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a> object-like macro, <a href="#6.10.3">6.10.3</a>
34308 structure/union member, <a href="#6.2.3">6.2.3</a> obsolescence, <a href="#6.11">6.11</a>, <a href="#7.31">7.31</a>
34310 named label, <a href="#6.8.1">6.8.1</a> octal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
34312 nan functions, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#F.2.1">F.2.1</a>, <a href="#F.10.8.2">F.10.8.2</a> <a href="#6.4.4.4">6.4.4.4</a>
34313 NAN macro, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> offsetof macro, <a href="#7.19">7.19</a>
34315 nearbyint functions, <a href="#7.12.9.3">7.12.9.3</a>, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, once_flag type, <a href="#7.26.1">7.26.1</a>
34317 nearbyint type-generic macro, <a href="#7.25">7.25</a> ones' complement, <a href="#6.2.6.2">6.2.6.2</a>
34318 nearest integer functions, <a href="#7.12.9">7.12.9</a>, <a href="#F.10.6">F.10.6</a> operand, <a href="#6.4.6">6.4.6</a>, <a href="#6.5">6.5</a>
34319 negation operator (!), <a href="#6.5.3.3">6.5.3.3</a> operating system, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#7.22.4.8">7.22.4.8</a>
34320 negative zero, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.12.11.1">7.12.11.1</a> operations on files, <a href="#7.21.4">7.21.4</a>, <a href="#K.3.5.1">K.3.5.1</a>
34321 new-line character, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#6.10.4">6.10.4</a> operator, <a href="#6.4.6">6.4.6</a>
34322 new-line escape sequence (\n), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, operators, <a href="#6.5">6.5</a>
34324 nextafter functions, <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, additive, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>
34327 nexttoward functions, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, <a href="#F.10.8.4">F.10.8.4</a> equality, <a href="#6.5.9">6.5.9</a>
34328 nexttoward type-generic macro, <a href="#7.25">7.25</a> multiplicative, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
34331 non-stop floating-point control mode, <a href="#7.6.4.2">7.6.4.2</a> preprocessing, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>, <a href="#6.10.9">6.10.9</a>
34332 nongraphic characters, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> relational, <a href="#6.5.8">6.5.8</a>
34336 normalized broken-down time, <a href="#K.3.8.1">K.3.8.1</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a> unary arithmetic, <a href="#6.5.3.3">6.5.3.3</a>
34337 <!--page 692 -->
34338 optional features, see conditional features portability, <a href="#4">4</a>, <a href="#J">J</a>
34341 bitwise exclusive (^), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a> positive difference functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.10.9">F.10.9</a>
34342 bitwise exclusive assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> postfix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a>
34343 bitwise inclusive (|), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a> postfix expressions, <a href="#6.5.2">6.5.2</a>
34344 bitwise inclusive assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> postfix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a>
34345 logical (||), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a> pow functions, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#F.10.4.4">F.10.4.4</a>
34348 order of evaluation, <a href="#6.5">6.5</a>, <a href="#6.5.16">6.5.16</a>, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>, complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a>
34350 ordinary identifier name space, <a href="#6.2.3">6.2.3</a> pp-number, <a href="#6.4.8">6.4.8</a>
34351 orientation of stream, <a href="#7.21.2">7.21.2</a>, <a href="#7.29.3.5">7.29.3.5</a> pragma operator, <a href="#6.10.9">6.10.9</a>
34352 out-of-bounds store, <a href="#L.2.1">L.2.1</a> pragma preprocessing directive, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a>
34354 over-aligned, <a href="#6.2.8">6.2.8</a> precedence of syntax rules, <a href="#5.1.1.2">5.1.1.2</a>
34355 precision, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.2.1">7.29.2.1</a>
34356 padding excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>
34357 binary stream, <a href="#7.21.2">7.21.2</a> predefined macro names, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a>
34358 bits, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.20.1.1">7.20.1.1</a> prefix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a>
34359 structure/union, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.7.2.1">6.7.2.1</a> prefix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a>
34360 parameter, <a href="#3.16">3.16</a> preprocessing concatenation, <a href="#6.10.3.3">6.10.3.3</a>
34361 array, <a href="#6.9.1">6.9.1</a> preprocessing directives, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10">6.10</a>
34362 ellipsis, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.10.3">6.10.3</a> preprocessing file, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.10">6.10</a>
34363 function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a> preprocessing numbers, <a href="#6.4">6.4</a>, <a href="#6.4.8">6.4.8</a>
34367 parameter type list, <a href="#6.7.6.3">6.7.6.3</a> _Pragma, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a>
34368 parentheses punctuator (( )), <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a> defined, <a href="#6.10.1">6.10.1</a>
34369 parenthesized expression, <a href="#6.5.1">6.5.1</a> preprocessing tokens, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>
34370 parse state, <a href="#7.21.2">7.21.2</a> preprocessing translation unit, <a href="#5.1.1.1">5.1.1.1</a>
34372 permitted form of initializer, <a href="#6.6">6.6</a> PRIcFASTN macros, <a href="#7.8.1">7.8.1</a>
34373 perror function, <a href="#7.21.10.4">7.21.10.4</a> PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a>
34374 phase angle, complex, <a href="#7.3.9.1">7.3.9.1</a> PRIcMAX macros, <a href="#7.8.1">7.8.1</a>
34375 physical source lines, <a href="#5.1.1.2">5.1.1.2</a> PRIcN macros, <a href="#7.8.1">7.8.1</a>
34377 plus operator, unary, <a href="#6.5.3.3">6.5.3.3</a> primary expression, <a href="#6.5.1">6.5.1</a>
34378 pointer arithmetic, <a href="#6.5.6">6.5.6</a> printf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.21.6.10">7.21.6.10</a>,
34380 pointer declarator, <a href="#6.7.6.1">6.7.6.1</a> printf_s function, <a href="#K.3.5.3.3">K.3.5.3.3</a>
34381 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> printing character, <a href="#5.2.2">5.2.2</a>, <a href="#7.4">7.4</a>, <a href="#7.4.1.8">7.4.1.8</a>
34382 pointer to function, <a href="#6.5.2.2">6.5.2.2</a> printing wide character, <a href="#7.30.2">7.30.2</a>
34384 pointer type conversion, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> program execution, <a href="#5.1.2.2.2">5.1.2.2.2</a>, <a href="#5.1.2.3">5.1.2.3</a>
34386 pole error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#7.12.6.8">7.12.6.8</a>, program image, <a href="#5.1.1.2">5.1.1.2</a>
34387 <a href="#7.12.6.9">7.12.6.9</a>, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#7.12.7.4">7.12.7.4</a>, program name (argv[0]), <a href="#5.1.2.2.1">5.1.2.2.1</a>
34388 <a href="#7.12.8.3">7.12.8.3</a>, <a href="#7.12.8.4">7.12.8.4</a> program parameters, <a href="#5.1.2.2.1">5.1.2.2.1</a>
34389 <!--page 693 -->
34390 program startup, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.1">5.1.2.2.1</a> recursion, <a href="#6.5.2.2">6.5.2.2</a>
34391 program structure, <a href="#5.1.1.1">5.1.1.1</a> recursive function call, <a href="#6.5.2.2">6.5.2.2</a>
34392 program termination, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>, redefinition of macro, <a href="#6.10.3">6.10.3</a>
34393 <a href="#5.1.2.3">5.1.2.3</a> reentrancy, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>
34396 promotions register storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
34397 default argument, <a href="#6.5.2.2">6.5.2.2</a> relational expressions, <a href="#6.5.8">6.5.8</a>
34398 integer, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.3.1.1">6.3.1.1</a> relaxed atomic operations, <a href="#5.1.2.4">5.1.2.4</a>
34400 pseudo-random sequence functions, <a href="#7.22.2">7.22.2</a> release operation, <a href="#5.1.2.4">5.1.2.4</a>
34401 PTRDIFF_MAX macro, <a href="#7.20.3">7.20.3</a> release sequence, <a href="#5.1.2.4">5.1.2.4</a>
34402 PTRDIFF_MIN macro, <a href="#7.20.3">7.20.3</a> reliability of data, interrupted, <a href="#5.1.2.3">5.1.2.3</a>
34403 ptrdiff_t type, <a href="#7.17.1">7.17.1</a>, <a href="#7.19">7.19</a>, <a href="#7.20.3">7.20.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, remainder assignment operator (%=), <a href="#6.5.16.2">6.5.16.2</a>
34404 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a> remainder functions, <a href="#7.12.10">7.12.10</a>, <a href="#F.10.7">F.10.7</a>
34405 punctuators, <a href="#6.4.6">6.4.6</a> remainder functions, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>,
34406 putc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.7">7.21.7.7</a>, <a href="#7.21.7.8">7.21.7.8</a> <a href="#F.10.7.2">F.10.7.2</a>
34407 putchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.8">7.21.7.8</a> remainder operator (%), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>
34408 puts function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.9">7.21.7.9</a> remainder type-generic macro, <a href="#7.25">7.25</a>
34409 putwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.8">7.29.3.8</a>, <a href="#7.29.3.9">7.29.3.9</a> remove function, <a href="#7.21.4.1">7.21.4.1</a>, <a href="#7.21.4.4">7.21.4.4</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
34410 putwchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.9">7.29.3.9</a> remquo functions, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, <a href="#F.10.7.3">F.10.7.3</a>
34412 qsort function, <a href="#7.22.5">7.22.5</a>, <a href="#7.22.5.2">7.22.5.2</a> rename function, <a href="#7.21.4.2">7.21.4.2</a>
34413 qsort_s function, <a href="#K.3.6.3">K.3.6.3</a>, <a href="#K.3.6.3.2">K.3.6.3.2</a> representations of types, <a href="#6.2.6">6.2.6</a>
34415 qualified version of type, <a href="#6.2.5">6.2.5</a> rescanning and replacement, <a href="#6.10.3.4">6.10.3.4</a>
34416 question-mark escape sequence (\?), <a href="#6.4.4.4">6.4.4.4</a> reserved identifiers, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a>, <a href="#K.3.1.2">K.3.1.2</a>
34417 quick_exit function, <a href="#7.22.4.3">7.22.4.3</a>, <a href="#7.22.4.4">7.22.4.4</a>, restartable multibyte/wide character conversion
34418 <a href="#7.22.4.7">7.22.4.7</a> functions, <a href="#7.28.1">7.28.1</a>, <a href="#7.29.6.3">7.29.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a>
34421 raise function, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a>, <a href="#7.22.4.1">7.22.4.1</a> restore calling environment function, <a href="#7.13.2">7.13.2</a>
34422 rand function, <a href="#7.22">7.22</a>, <a href="#7.22.2.1">7.22.2.1</a>, <a href="#7.22.2.2">7.22.2.2</a> restrict type qualifier, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a>
34423 RAND_MAX macro, <a href="#7.22">7.22</a>, <a href="#7.22.2.1">7.22.2.1</a> restrict-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a>
34425 excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> rewind function, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.5">7.21.9.5</a>,
34426 range error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#7.29.3.10">7.29.3.10</a>
34427 <a href="#7.12.6.2">7.12.6.2</a>, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#7.12.6.6">7.12.6.6</a>, right-shift assignment operator (>>=), <a href="#6.5.16.2">6.5.16.2</a>
34428 <a href="#7.12.6.13">7.12.6.13</a>, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.8.2">7.12.8.2</a>, right-shift operator (>>), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
34429 <a href="#7.12.8.3">7.12.8.3</a>, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, rint functions, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, <a href="#F.10.6.4">F.10.6.4</a>
34430 <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#7.12.13.1">7.12.13.1</a> rint type-generic macro, <a href="#7.25">7.25</a>
34431 rank, see integer conversion rank round functions, <a href="#7.12.9.6">7.12.9.6</a>, <a href="#F.10.6.6">F.10.6.6</a>
34432 read-modify-write operations, <a href="#5.1.2.4">5.1.2.4</a> round type-generic macro, <a href="#7.25">7.25</a>
34433 real floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, rounding mode, floating point, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34434 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> RSIZE_MAX macro, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>,
34435 real floating types, <a href="#6.2.5">6.2.5</a> <a href="#K.3.5.3.5">K.3.5.3.5</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a>, <a href="#K.3.5.3.12">K.3.5.3.12</a>, <a href="#K.3.5.3.13">K.3.5.3.13</a>,
34436 real type domain, <a href="#6.2.5">6.2.5</a> <a href="#K.3.5.4.1">K.3.5.4.1</a>, <a href="#K.3.6.2.1">K.3.6.2.1</a>, <a href="#K.3.6.3.1">K.3.6.3.1</a>, <a href="#K.3.6.3.2">K.3.6.3.2</a>,
34437 real types, <a href="#6.2.5">6.2.5</a> <a href="#K.3.6.4.1">K.3.6.4.1</a>, <a href="#K.3.6.5.1">K.3.6.5.1</a>, <a href="#K.3.6.5.2">K.3.6.5.2</a>, <a href="#K.3.7.1.1">K.3.7.1.1</a>,
34438 real-floating, <a href="#7.12.3">7.12.3</a> <a href="#K.3.7.1.2">K.3.7.1.2</a>, <a href="#K.3.7.1.3">K.3.7.1.3</a>, <a href="#K.3.7.1.4">K.3.7.1.4</a>, <a href="#K.3.7.2.1">K.3.7.2.1</a>,
34439 realloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.5">7.22.3.5</a> <a href="#K.3.7.2.2">K.3.7.2.2</a>, <a href="#K.3.7.3.1">K.3.7.3.1</a>, <a href="#K.3.7.4.1">K.3.7.4.1</a>, <a href="#K.3.7.4.2">K.3.7.4.2</a>,
34440 recommended practice, <a href="#3.17">3.17</a> <a href="#K.3.8.2.1">K.3.8.2.1</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>, <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a>,
34441 <!--page 694 -->
34442 <a href="#K.3.9.1.8">K.3.9.1.8</a>, <a href="#K.3.9.1.9">K.3.9.1.9</a>, <a href="#K.3.9.2.1.1">K.3.9.2.1.1</a>, <a href="#K.3.9.2.1.2">K.3.9.2.1.2</a>, <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6.1.1">K.3.6.1.1</a>, <a href="#K.3.6.1.2">K.3.6.1.2</a>, <a href="#K.3.6.1.3">K.3.6.1.3</a>
34443 <a href="#K.3.9.2.1.3">K.3.9.2.1.3</a>, <a href="#K.3.9.2.1.4">K.3.9.2.1.4</a>, <a href="#K.3.9.2.2.1">K.3.9.2.2.1</a>, setbuf function, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.1">7.21.5.1</a>, <a href="#7.21.5.5">7.21.5.5</a>
34444 <a href="#K.3.9.2.2.2">K.3.9.2.2.2</a>, <a href="#K.3.9.2.3.1">K.3.9.2.3.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a>, setjmp macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>
34445 <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>, <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a> setjmp.h header, <a href="#7.13">7.13</a>
34446 rsize_t type, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>, setlocale function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
34447 <a href="#K.3.6">K.3.6</a>, <a href="#K.3.7">K.3.7</a>, <a href="#K.3.8">K.3.8</a>, <a href="#K.3.9">K.3.9</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a> setvbuf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.1">7.21.5.1</a>,
34448 runtime-constraint, <a href="#3.18">3.18</a> <a href="#7.21.5.5">7.21.5.5</a>, <a href="#7.21.5.6">7.21.5.6</a>
34449 Runtime-constraint handling functions, <a href="#K.3.6.1">K.3.6.1</a> shall, <a href="#4">4</a>
34453 save calling environment function, <a href="#7.13.1">7.13.1</a> short identifier, character, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.3">6.4.3</a>
34454 scalar types, <a href="#6.2.5">6.2.5</a> short int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.1">7.21.6.1</a>,
34455 scalbln function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.10.3.13">F.10.3.13</a> <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>
34456 scalbln type-generic macro, <a href="#7.25">7.25</a> short int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
34457 scalbn function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.10.3.13">F.10.3.13</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
34458 scalbn type-generic macro, <a href="#7.25">7.25</a> SHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
34459 scanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.4">7.21.6.4</a>, <a href="#7.21.6.11">7.21.6.11</a> SHRT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
34460 scanf_s function, <a href="#K.3.5.3.4">K.3.5.3.4</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a> side effects, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.3.2.2">6.3.2.2</a>, <a href="#6.5">6.5</a>, <a href="#6.5.2.4">6.5.2.4</a>,
34461 scanlist, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a> <a href="#6.5.16">6.5.16</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.8.3">6.8.3</a>, <a href="#7.6">7.6</a>, <a href="#7.6.1">7.6.1</a>, <a href="#7.21.7.5">7.21.7.5</a>,
34462 scanset, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a> <a href="#7.21.7.7">7.21.7.7</a>, <a href="#7.29.3.6">7.29.3.6</a>, <a href="#7.29.3.8">7.29.3.8</a>, <a href="#F.8.1">F.8.1</a>, <a href="#F.9.1">F.9.1</a>,
34464 SCHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> SIG_ATOMIC_MAX macro, <a href="#7.20.3">7.20.3</a>
34465 SCNcFASTN macros, <a href="#7.8.1">7.8.1</a> SIG_ATOMIC_MIN macro, <a href="#7.20.3">7.20.3</a>
34466 SCNcLEASTN macros, <a href="#7.8.1">7.8.1</a> sig_atomic_t type, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>,
34468 SCNcN macros, <a href="#7.8.1">7.8.1</a> SIG_DFL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>
34469 SCNcPTR macros, <a href="#7.8.1">7.8.1</a> SIG_ERR macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>
34470 scope of identifier, <a href="#6.2.1">6.2.1</a>, <a href="#6.9.2">6.9.2</a> SIG_IGN macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>
34472 string, <a href="#7.24.5">7.24.5</a>, <a href="#K.3.7.3">K.3.7.3</a> SIGFPE macro, <a href="#7.12.1">7.12.1</a>, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#J.2">J.2</a>, <a href="#J.5.17">J.5.17</a>
34473 utility, <a href="#7.22.5">7.22.5</a>, <a href="#K.3.6.3">K.3.6.3</a> SIGILL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#J.2">J.2</a>
34474 wide string, <a href="#7.29.4.5">7.29.4.5</a>, <a href="#K.3.9.2.3">K.3.9.2.3</a> SIGINT macro, <a href="#7.14">7.14</a>
34475 SEEK_CUR macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.9.2">7.21.9.2</a> sign and magnitude, <a href="#6.2.6.2">6.2.6.2</a>
34476 SEEK_END macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.9.2">7.21.9.2</a> sign bit, <a href="#6.2.6.2">6.2.6.2</a>
34477 SEEK_SET macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.9.2">7.21.9.2</a> signal function, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>
34478 selection statements, <a href="#6.8.4">6.8.4</a> signal handler, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a>
34479 self-referential structure, <a href="#6.7.2.3">6.7.2.3</a> signal handling functions, <a href="#7.14.1">7.14.1</a>
34480 semicolon punctuator (;), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>, signal handling header, <a href="#7.14">7.14</a>, <a href="#7.31.7">7.31.7</a>
34481 <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a> signal.h header, <a href="#7.14">7.14</a>, <a href="#7.31.7">7.31.7</a>
34482 separate compilation, <a href="#5.1.1.1">5.1.1.1</a> signaling NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#F.2.1">F.2.1</a>
34483 separate translation, <a href="#5.1.1.1">5.1.1.1</a> signals, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1">7.14.1</a>
34484 sequence points, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.13">6.5.13</a>, <a href="#6.5.14">6.5.14</a>, signbit macro, <a href="#7.12.3.6">7.12.3.6</a>, <a href="#F.3">F.3</a>
34485 <a href="#6.5.15">6.5.15</a>, <a href="#6.5.17">6.5.17</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a>, <a href="#6.7.6">6.7.6</a>, <a href="#6.8">6.8</a>, signed char type, <a href="#6.2.5">6.2.5</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
34486 <a href="#7.1.4">7.1.4</a>, <a href="#7.21.6">7.21.6</a>, <a href="#7.22.5">7.22.5</a>, <a href="#7.29.2">7.29.2</a>, <a href="#C">C</a>, <a href="#K.3.6.3">K.3.6.3</a> <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>
34488 sequenced before, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.2.4">6.5.2.4</a>, signed integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>
34489 <a href="#6.5.16">6.5.16</a>, see also indeterminately sequenced, signed type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
34491 sequencing of statements, <a href="#6.8">6.8</a> signed types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>
34493 <!--page 695 -->
34494 SIGSEGV macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#J.2">J.2</a> <a href="#7.8"><inttypes.h></a>, <a href="#7.8">7.8</a>, <a href="#7.31.5">7.31.5</a>
34495 SIGTERM macro, <a href="#7.14">7.14</a> <a href="#7.9"><iso646.h></a>, <a href="#4">4</a>, <a href="#7.9">7.9</a>
34496 simple assignment operator (=), <a href="#6.5.16.1">6.5.16.1</a> <a href="#7.10"><limits.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
34497 sin functions, <a href="#7.12.4.6">7.12.4.6</a>, <a href="#F.10.1.6">F.10.1.6</a> <a href="#7.11"><locale.h></a>, <a href="#7.11">7.11</a>, <a href="#7.31.6">7.31.6</a>
34498 sin type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> <a href="#7.12"><math.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.25">7.25</a>, <a href="#F">F</a>, <a href="#F.10">F.10</a>,
34499 single-byte character, <a href="#3.7.1">3.7.1</a>, <a href="#5.2.1.2">5.2.1.2</a> <a href="#J.5.17">J.5.17</a>
34500 single-byte/wide character conversion functions, <a href="#7.13"><setjmp.h></a>, <a href="#7.13">7.13</a>
34501 <a href="#7.29.6.1">7.29.6.1</a> <a href="#7.14"><signal.h></a>, <a href="#7.14">7.14</a>, <a href="#7.31.7">7.31.7</a>
34502 single-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.15"><stdalign.h></a>, <a href="#4">4</a>, <a href="#7.15">7.15</a>
34503 single-quote escape sequence (\'), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> <a href="#7.16"><stdarg.h></a>, <a href="#4">4</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#7.16">7.16</a>
34504 singularity, <a href="#7.12.1">7.12.1</a> <a href="#7.17"><stdatomic.h></a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.17">7.17</a>,
34505 sinh functions, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#F.10.2.5">F.10.2.5</a> <a href="#7.31.8">7.31.8</a>
34506 sinh type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> <a href="#7.18"><stdbool.h></a>, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.31.9">7.31.9</a>, <a href="#H">H</a>
34507 SIZE_MAX macro, <a href="#7.20.3">7.20.3</a> <a href="#7.19"><stddef.h></a>, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>,
34508 size_t type, <a href="#6.2.8">6.2.8</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#7.19">7.19</a>, <a href="#7.20.3">7.20.3</a>, <a href="#7.21.1">7.21.1</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.19">7.19</a>, <a href="#K.3.3">K.3.3</a>
34509 <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22">7.22</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.27.1">7.27.1</a>, <a href="#7.28">7.28</a>, <a href="#7.20"><stdint.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.20">7.20</a>,
34510 <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>, <a href="#7.31.10">7.31.10</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>
34511 <a href="#K.3.5">K.3.5</a>, <a href="#K.3.6">K.3.6</a>, <a href="#K.3.7">K.3.7</a>, <a href="#K.3.8">K.3.8</a>, <a href="#K.3.9">K.3.9</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a> <a href="#7.21"><stdio.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21">7.21</a>, <a href="#7.31.11">7.31.11</a>, <a href="#F">F</a>, <a href="#K.3.5">K.3.5</a>
34512 sizeof operator, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3">6.5.3</a>, <a href="#6.5.3.4">6.5.3.4</a> <a href="#7.22"><stdlib.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.22">7.22</a>, <a href="#7.31.12">7.31.12</a>, <a href="#F">F</a>,
34513 sizes of integer types header, <a href="#7.10">7.10</a> <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6">K.3.6</a>
34514 snprintf function, <a href="#7.21.6.5">7.21.6.5</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.23"><stdnoreturn.h></a>, <a href="#4">4</a>, <a href="#7.23">7.23</a>
34515 <a href="#K.3.5.3.5">K.3.5.3.5</a> <a href="#7.24"><string.h></a>, <a href="#7.24">7.24</a>, <a href="#7.31.13">7.31.13</a>, <a href="#K.3.7">K.3.7</a>
34516 snprintf_s function, <a href="#K.3.5.3.5">K.3.5.3.5</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a> <a href="#7.25"><tgmath.h></a>, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a>
34517 snwprintf_s function, <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a> <a href="#7.26"><threads.h></a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.26">7.26</a>, <a href="#7.31.15">7.31.15</a>
34518 sorting utility functions, <a href="#7.22.5">7.22.5</a>, <a href="#K.3.6.3">K.3.6.3</a> <a href="#7.27"><time.h></a>, <a href="#7.26.1">7.26.1</a>, <a href="#7.27">7.27</a>, <a href="#7.31.14">7.31.14</a>, <a href="#K.3.8">K.3.8</a>
34519 source character set, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a> <a href="#7.28"><uchar.h></a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.28">7.28</a>
34520 source file, <a href="#5.1.1.1">5.1.1.1</a> <a href="#7.29"><wchar.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.29">7.29</a>, <a href="#7.31.16">7.31.16</a>,
34521 name, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8.1">6.10.8.1</a> <a href="#F">F</a>, <a href="#K.3.9">K.3.9</a>
34522 source file inclusion, <a href="#6.10.2">6.10.2</a> <a href="#7.30"><wctype.h></a>, <a href="#7.30">7.30</a>, <a href="#7.31.17">7.31.17</a>
34523 source lines, <a href="#5.1.1.2">5.1.1.2</a> standard input stream, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>
34524 source text, <a href="#5.1.1.2">5.1.1.2</a> standard integer types, <a href="#6.2.5">6.2.5</a>
34525 space character (' '), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, standard output stream, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>
34526 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.30.2.1.3">7.30.2.1.3</a> standard signed integer types, <a href="#6.2.5">6.2.5</a>
34527 sprintf function, <a href="#7.21.6.6">7.21.6.6</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a> state-dependent encoding, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a>
34528 sprintf_s function, <a href="#K.3.5.3.5">K.3.5.3.5</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a> statements, <a href="#6.8">6.8</a>
34529 sqrt functions, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10.4.5">F.10.4.5</a> break, <a href="#6.8.6.3">6.8.6.3</a>
34532 sscanf function, <a href="#7.21.6.7">7.21.6.7</a>, <a href="#7.21.6.14">7.21.6.14</a> do, <a href="#6.8.5.2">6.8.5.2</a>
34533 sscanf_s function, <a href="#K.3.5.3.7">K.3.5.3.7</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a> else, <a href="#6.8.4.1">6.8.4.1</a>
34534 standard error stream, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.10.4">7.21.10.4</a> expression, <a href="#6.8.3">6.8.3</a>
34535 standard headers, <a href="#4">4</a>, <a href="#7.1.2">7.1.2</a> for, <a href="#6.8.5.3">6.8.5.3</a>
34536 <a href="#7.2"><assert.h></a>, <a href="#7.2">7.2</a> goto, <a href="#6.8.6.1">6.8.6.1</a>
34537 <a href="#7.3"><complex.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.3">7.3</a>, if, <a href="#6.8.4.1">6.8.4.1</a>
34538 <a href="#7.25">7.25</a>, <a href="#7.31.1">7.31.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a> iteration, <a href="#6.8.5">6.8.5</a>
34539 <a href="#7.4"><ctype.h></a>, <a href="#7.4">7.4</a>, <a href="#7.31.2">7.31.2</a> jump, <a href="#6.8.6">6.8.6</a>
34540 <a href="#7.5"><errno.h></a>, <a href="#7.5">7.5</a>, <a href="#7.31.3">7.31.3</a>, <a href="#K.3.2">K.3.2</a> labeled, <a href="#6.8.1">6.8.1</a>
34541 <a href="#7.6"><fenv.h></a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, null, <a href="#6.8.3">6.8.3</a>
34542 <a href="#7.31.4">7.31.4</a>, <a href="#F">F</a>, <a href="#H">H</a> return, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a>
34543 <a href="#7.7"><float.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.22.1.3">7.22.1.3</a>, selection, <a href="#6.8.4">6.8.4</a>
34545 <!--page 696 -->
34546 switch, <a href="#6.8.4.2">6.8.4.2</a> strerrorlen_s function, <a href="#K.3.7.4.3">K.3.7.4.3</a>
34547 while, <a href="#6.8.5.1">6.8.5.1</a> strftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.27.3">7.27.3</a>, <a href="#7.27.3.5">7.27.3.5</a>,
34548 static assertions, <a href="#6.7.10">6.7.10</a> <a href="#7.29.5.1">7.29.5.1</a>, <a href="#K.3.8.2">K.3.8.2</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>
34550 static storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.7.1">6.7.1</a> strictly conforming program, <a href="#4">4</a>
34551 static, in array declarators, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.6.3">6.7.6.3</a> string, <a href="#7.1.1">7.1.1</a>
34552 static_assert declaration, <a href="#6.7.10">6.7.10</a> comparison functions, <a href="#7.24.4">7.24.4</a>
34553 static_assert macro, <a href="#7.2">7.2</a> concatenation functions, <a href="#7.24.3">7.24.3</a>, <a href="#K.3.7.2">K.3.7.2</a>
34554 stdalign.h header, <a href="#4">4</a>, <a href="#7.15">7.15</a> conversion functions, <a href="#7.11.1.1">7.11.1.1</a>
34555 stdarg.h header, <a href="#4">4</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#7.16">7.16</a> copying functions, <a href="#7.24.2">7.24.2</a>, <a href="#K.3.7.1">K.3.7.1</a>
34556 stdatomic.h header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.17">7.17</a>, library function conventions, <a href="#7.24.1">7.24.1</a>
34557 <a href="#7.31.8">7.31.8</a> literal, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.7.9">6.7.9</a>
34558 stdbool.h header, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.31.9">7.31.9</a>, <a href="#H">H</a> miscellaneous functions, <a href="#7.24.6">7.24.6</a>, <a href="#K.3.7.4">K.3.7.4</a>
34559 STDC, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a>
34560 stddef.h header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, search functions, <a href="#7.24.5">7.24.5</a>, <a href="#K.3.7.3">K.3.7.3</a>
34561 <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.19">7.19</a>, <a href="#K.3.3">K.3.3</a> string handling header, <a href="#7.24">7.24</a>, <a href="#7.31.13">7.31.13</a>, <a href="#K.3.7">K.3.7</a>
34562 stderr macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a> string.h header, <a href="#7.24">7.24</a>, <a href="#7.31.13">7.31.13</a>, <a href="#K.3.7">K.3.7</a>
34563 stdin macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.4">7.21.6.4</a>, stringizing, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.9">6.10.9</a>
34564 <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.29.2.12">7.29.2.12</a>, <a href="#7.29.3.7">7.29.3.7</a>, <a href="#K.3.5.3.4">K.3.5.3.4</a>, strlen function, <a href="#7.24.6.3">7.24.6.3</a>
34565 <a href="#K.3.5.4.1">K.3.5.4.1</a>, <a href="#K.3.9.1.14">K.3.9.1.14</a> strncat function, <a href="#7.24.3.2">7.24.3.2</a>
34566 stdint.h header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.20">7.20</a>, strncat_s function, <a href="#K.3.7.2.2">K.3.7.2.2</a>
34567 <a href="#7.31.10">7.31.10</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a> strncmp function, <a href="#7.24.4">7.24.4</a>, <a href="#7.24.4.4">7.24.4.4</a>
34568 stdio.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21">7.21</a>, <a href="#7.31.11">7.31.11</a>, <a href="#F">F</a>, strncpy function, <a href="#7.24.2.4">7.24.2.4</a>
34570 stdlib.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.22">7.22</a>, <a href="#7.31.12">7.31.12</a>, <a href="#F">F</a>, strnlen_s function, <a href="#K.3.7.4.4">K.3.7.4.4</a>
34571 <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6">K.3.6</a> stronger, <a href="#6.2.8">6.2.8</a>
34572 stdnoreturn.h header, <a href="#4">4</a>, <a href="#7.23">7.23</a> strpbrk function, <a href="#7.24.5.4">7.24.5.4</a>
34573 stdout macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.3">7.21.6.3</a>, strrchr function, <a href="#7.24.5.5">7.24.5.5</a>
34574 <a href="#7.21.7.8">7.21.7.8</a>, <a href="#7.21.7.9">7.21.7.9</a>, <a href="#7.29.2.11">7.29.2.11</a>, <a href="#7.29.3.9">7.29.3.9</a> strspn function, <a href="#7.24.5.6">7.24.5.6</a>
34575 storage duration, <a href="#6.2.4">6.2.4</a> strstr function, <a href="#7.24.5.7">7.24.5.7</a>
34576 storage order of array, <a href="#6.5.2.1">6.5.2.1</a> strtod function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.3">7.22.1.3</a>,
34577 storage unit (bit-field), <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.7.2.1">6.7.2.1</a> <a href="#7.29.2.2">7.29.2.2</a>, <a href="#F.3">F.3</a>
34578 storage-class specifiers, <a href="#6.7.1">6.7.1</a>, <a href="#6.11.5">6.11.5</a> strtof function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.22.1.3">7.22.1.3</a>, <a href="#F.3">F.3</a>
34579 strcat function, <a href="#7.24.3.1">7.24.3.1</a> strtoimax function, <a href="#7.8.2.3">7.8.2.3</a>
34580 strcat_s function, <a href="#K.3.7.2.1">K.3.7.2.1</a> strtok function, <a href="#7.24.5.8">7.24.5.8</a>
34581 strchr function, <a href="#7.24.5.2">7.24.5.2</a> strtok_s function, <a href="#K.3.7.3.1">K.3.7.3.1</a>
34582 strcmp function, <a href="#7.24.4">7.24.4</a>, <a href="#7.24.4.2">7.24.4.2</a> strtol function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.2">7.22.1.2</a>,
34583 strcoll function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.24.4.3">7.24.4.3</a>, <a href="#7.24.4.5">7.24.4.5</a> <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.2.2">7.29.2.2</a>
34584 strcpy function, <a href="#7.24.2.3">7.24.2.3</a> strtold function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.22.1.3">7.22.1.3</a>, <a href="#F.3">F.3</a>
34585 strcpy_s function, <a href="#K.3.7.1.3">K.3.7.1.3</a> strtoll function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1.2">7.22.1.2</a>, <a href="#7.22.1.4">7.22.1.4</a>
34586 strcspn function, <a href="#7.24.5.3">7.24.5.3</a> strtoul function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.2">7.22.1.2</a>,
34587 streams, <a href="#7.21.2">7.21.2</a>, <a href="#7.22.4.4">7.22.4.4</a> <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.29.2.2">7.29.2.2</a>
34588 fully buffered, <a href="#7.21.3">7.21.3</a> strtoull function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1.2">7.22.1.2</a>, <a href="#7.22.1.4">7.22.1.4</a>
34589 line buffered, <a href="#7.21.3">7.21.3</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
34591 standard error, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> struct lconv, <a href="#7.11">7.11</a>
34592 standard input, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> struct timespec, <a href="#7.27.1">7.27.1</a>
34593 standard output, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> struct tm, <a href="#7.27.1">7.27.1</a>
34595 strerror function, <a href="#7.21.10.4">7.21.10.4</a>, <a href="#7.24.6.2">7.24.6.2</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
34596 strerror_s function, <a href="#K.3.7.4.2">K.3.7.4.2</a>, <a href="#K.3.7.4.3">K.3.7.4.3</a> content, <a href="#6.7.2.3">6.7.2.3</a>
34597 <!--page 697 -->
34598 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> thrd_current function, <a href="#7.26.5.2">7.26.5.2</a>
34599 initialization, <a href="#6.7.9">6.7.9</a> thrd_detach function, <a href="#7.26.5.3">7.26.5.3</a>
34600 member alignment, <a href="#6.7.2.1">6.7.2.1</a> thrd_equal function, <a href="#7.26.5.4">7.26.5.4</a>
34601 member name space, <a href="#6.2.3">6.2.3</a> thrd_exit function, <a href="#7.26.5.5">7.26.5.5</a>
34602 member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a> thrd_join function, <a href="#7.26.5.6">7.26.5.6</a>
34603 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> thrd_sleep function, <a href="#7.26.5.7">7.26.5.7</a>
34605 tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a> thrd_t type, <a href="#7.26.1">7.26.1</a>
34606 type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a> thrd_yield function, <a href="#7.26.5.8">7.26.5.8</a>
34607 strxfrm function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.24.4.5">7.24.4.5</a> thread of execution, <a href="#5.1.2.4">5.1.2.4</a>, <a href="#7.1.4">7.1.4</a>, <a href="#7.6">7.6</a>, <a href="#7.22.4.6">7.22.4.6</a>,
34608 subnormal floating-point numbers, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#K.3.6.2.1">K.3.6.2.1</a>
34609 subscripting, <a href="#6.5.2.1">6.5.2.1</a> thread storage duration, <a href="#6.2.4">6.2.4</a>, <a href="#7.6">7.6</a>
34610 subtraction assignment operator (-=), <a href="#6.5.16.2">6.5.16.2</a> threads header, <a href="#7.26">7.26</a>, <a href="#7.31.15">7.31.15</a>
34611 subtraction operator (-), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a> threads.h header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.26">7.26</a>,
34614 integer constant, <a href="#6.4.4.1">6.4.4.1</a> broken down, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.3">7.27.2.3</a>, <a href="#7.27.3">7.27.3</a>, <a href="#7.27.3.1">7.27.3.1</a>,
34615 switch body, <a href="#6.8.4.2">6.8.4.2</a> <a href="#7.27.3.3">7.27.3.3</a>, <a href="#7.27.3.4">7.27.3.4</a>, <a href="#7.27.3.5">7.27.3.5</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a>,
34616 switch case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a>
34617 switch default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> calendar, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.2">7.27.2.2</a>, <a href="#7.27.2.3">7.27.2.3</a>, <a href="#7.27.2.4">7.27.2.4</a>,
34618 switch statement, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> <a href="#7.27.3.2">7.27.3.2</a>, <a href="#7.27.3.3">7.27.3.3</a>, <a href="#7.27.3.4">7.27.3.4</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>,
34619 swprintf function, <a href="#7.29.2.3">7.29.2.3</a>, <a href="#7.29.2.7">7.29.2.7</a>, <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a>
34620 <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a> components, <a href="#7.27.1">7.27.1</a>, <a href="#K.3.8.1">K.3.8.1</a>
34621 swprintf_s function, <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a> conversion functions, <a href="#7.27.3">7.27.3</a>, <a href="#K.3.8.2">K.3.8.2</a>
34622 swscanf function, <a href="#7.29.2.4">7.29.2.4</a>, <a href="#7.29.2.8">7.29.2.8</a> wide character, <a href="#7.29.5">7.29.5</a>
34623 swscanf_s function, <a href="#K.3.9.1.5">K.3.9.1.5</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a> local, <a href="#7.27.1">7.27.1</a>
34625 synchronization operation, <a href="#5.1.2.4">5.1.2.4</a> normalized broken down, <a href="#K.3.8.1">K.3.8.1</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a>
34626 synchronize with, <a href="#5.1.2.4">5.1.2.4</a> time base, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.5">7.27.2.5</a>
34628 syntax notation, <a href="#6.1">6.1</a> time.h header, <a href="#7.26.1">7.26.1</a>, <a href="#7.27">7.27</a>, <a href="#7.31.14">7.31.14</a>, <a href="#K.3.8">K.3.8</a>
34629 syntax rule precedence, <a href="#5.1.1.2">5.1.1.2</a> time_t type, <a href="#7.27.1">7.27.1</a>
34630 syntax summary, language, <a href="#A">A</a> TIME_UTC macro, <a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.26.4.4">7.26.4.4</a>, <a href="#7.26.5.7">7.26.5.7</a>,
34631 system function, <a href="#7.22.4.8">7.22.4.8</a> <a href="#7.27.1">7.27.1</a>, <a href="#7.27.2.5">7.27.2.5</a>
34633 tab characters, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> timespec_get function, <a href="#7.27.2.5">7.27.2.5</a>
34634 tag compatibility, <a href="#6.2.7">6.2.7</a> tm structure type, <a href="#7.27.1">7.27.1</a>, <a href="#7.29.1">7.29.1</a>, <a href="#K.3.8.1">K.3.8.1</a>
34635 tag name space, <a href="#6.2.3">6.2.3</a> TMP_MAX macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.21.4.4">7.21.4.4</a>
34636 tags, <a href="#6.7.2.3">6.7.2.3</a> TMP_MAX_S macro, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
34637 tan functions, <a href="#7.12.4.7">7.12.4.7</a>, <a href="#F.10.1.7">F.10.1.7</a> tmpfile function, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.22.4.4">7.22.4.4</a>
34638 tan type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> tmpfile_s function, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
34639 tanh functions, <a href="#7.12.5.6">7.12.5.6</a>, <a href="#F.10.2.6">F.10.2.6</a> tmpnam function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.21.4.4">7.21.4.4</a>,
34640 tanh type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> <a href="#K.3.5.1.2">K.3.5.1.2</a>
34641 temporary lifetime, <a href="#6.2.4">6.2.4</a> tmpnam_s function, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
34642 tentative definition, <a href="#6.9.2">6.9.2</a> token, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, see also preprocessing tokens
34644 text streams, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.9.4">7.21.9.4</a> token pasting, <a href="#6.10.3.3">6.10.3.3</a>
34645 tgamma functions, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#F.10.5.4">F.10.5.4</a> tolower function, <a href="#7.4.2.1">7.4.2.1</a>
34646 tgamma type-generic macro, <a href="#7.25">7.25</a> toupper function, <a href="#7.4.2.2">7.4.2.2</a>
34647 tgmath.h header, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> towctrans function, <a href="#7.30.3.2.1">7.30.3.2.1</a>, <a href="#7.30.3.2.2">7.30.3.2.2</a>
34648 thrd_create function, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.5.1">7.26.5.1</a> towlower function, <a href="#7.30.3.1.1">7.30.3.1.1</a>, <a href="#7.30.3.2.1">7.30.3.2.1</a>
34649 <!--page 698 -->
34650 towupper function, <a href="#7.30.3.1.2">7.30.3.1.2</a>, <a href="#7.30.3.2.1">7.30.3.2.1</a> UCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
34651 translation environment, <a href="#5">5</a>, <a href="#5.1.1">5.1.1</a> UINT_FASTN_MAX macros, <a href="#7.20.2.3">7.20.2.3</a>
34652 translation limits, <a href="#5.2.4.1">5.2.4.1</a> uint_fastN_t types, <a href="#7.20.1.3">7.20.1.3</a>
34653 translation phases, <a href="#5.1.1.2">5.1.1.2</a> uint_least16_t type, <a href="#7.28">7.28</a>
34654 translation unit, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.9">6.9</a> uint_least32_t type, <a href="#7.28">7.28</a>
34656 trap representation, <a href="#3.19.4">3.19.4</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.2.6.2">6.2.6.2</a>, uint_leastN_t types, <a href="#7.20.1.2">7.20.1.2</a>
34657 <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.5.2.3">6.5.2.3</a> UINT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
34659 complex, <a href="#7.3.5">7.3.5</a>, <a href="#G.6.1">G.6.1</a> UINTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.2.5">7.20.2.5</a>
34660 real, <a href="#7.12.4">7.12.4</a>, <a href="#F.10.1">F.10.1</a> uintmax_t type, <a href="#7.20.1.5">7.20.1.5</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
34661 trigraph sequences, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1.1">5.2.1.1</a> <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a>
34663 trunc functions, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#F.10.6.8">F.10.6.8</a> UINTN_MAX macros, <a href="#7.20.2.1">7.20.2.1</a>
34664 trunc type-generic macro, <a href="#7.25">7.25</a> uintN_t types, <a href="#7.20.1.1">7.20.1.1</a>
34665 truncation, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.3">7.21.5.3</a> UINTPTR_MAX macro, <a href="#7.20.2.4">7.20.2.4</a>
34666 truncation toward zero, <a href="#6.5.5">6.5.5</a> uintptr_t type, <a href="#7.20.1.4">7.20.1.4</a>
34667 tss_create function, <a href="#7.26.6.1">7.26.6.1</a> ULLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>,
34669 TSS_DTOR_ITERATIONS macro, <a href="#7.26.1">7.26.1</a> ULONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>,
34671 tss_get function, <a href="#7.26.6.3">7.26.6.3</a> unary arithmetic operators, <a href="#6.5.3.3">6.5.3.3</a>
34672 tss_set function, <a href="#7.26.6.4">7.26.6.4</a> unary expression, <a href="#6.5.3">6.5.3</a>
34673 tss_t type, <a href="#7.26.1">7.26.1</a> unary minus operator (-), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a>
34674 two's complement, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.20.1.1">7.20.1.1</a> unary operators, <a href="#6.5.3">6.5.3</a>
34675 type category, <a href="#6.2.5">6.2.5</a> unary plus operator (+), <a href="#6.5.3.3">6.5.3.3</a>
34677 type definitions, <a href="#6.7.8">6.7.8</a> undef preprocessing directive, <a href="#6.10.3.5">6.10.3.5</a>, <a href="#7.1.3">7.1.3</a>,
34679 type names, <a href="#6.7.7">6.7.7</a> undefined behavior, <a href="#3.4.3">3.4.3</a>, <a href="#4">4</a>, <a href="#J.2">J.2</a>
34680 type punning, <a href="#6.5.2.3">6.5.2.3</a> underscore character, <a href="#6.4.2.1">6.4.2.1</a>
34681 type qualifiers, <a href="#6.7.3">6.7.3</a> underscore, leading, in identifier, <a href="#7.1.3">7.1.3</a>
34682 type specifiers, <a href="#6.7.2">6.7.2</a> ungetc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>,
34683 type-generic macro, <a href="#7.25">7.25</a>, <a href="#G.7">G.7</a> <a href="#7.21.9.3">7.21.9.3</a>
34684 type-generic math header, <a href="#7.25">7.25</a> ungetwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3.10">7.29.3.10</a>
34685 typedef declaration, <a href="#6.7.8">6.7.8</a> Unicode, <a href="#7.28">7.28</a>, see also char16_t type,
34686 typedef storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.7.8">6.7.8</a> char32_t type, wchar_t type
34688 atomic, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.2.5">6.2.5</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a>, unicode utilities header, <a href="#7.28">7.28</a>
34689 <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.16.2">6.5.16.2</a>, <a href="#6.7.2.4">6.7.2.4</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.17.6">7.17.6</a> union
34691 compatible, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.6">6.7.6</a> content, <a href="#6.7.2.3">6.7.2.3</a>
34692 complex, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a> dot operator (.), <a href="#6.5.2.3">6.5.2.3</a>
34696 imaginary, <a href="#G">G</a> member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a>
34697 restrict qualified, <a href="#6.7.3">6.7.3</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
34700 uchar.h header, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.28">7.28</a> type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a>
34701 <!--page 699 -->
34702 universal character name, <a href="#6.4.3">6.4.3</a> value bits, <a href="#6.2.6.2">6.2.6.2</a>
34703 unnormalized floating-point numbers, <a href="#5.2.4.2.2">5.2.4.2.2</a> variable arguments, <a href="#6.10.3">6.10.3</a>
34704 unqualified type, <a href="#6.2.5">6.2.5</a> variable arguments header, <a href="#7.16">7.16</a>
34705 unqualified version of type, <a href="#6.2.5">6.2.5</a> variable length array, <a href="#6.7.6">6.7.6</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a>
34706 unsequenced, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a>, <a href="#6.5.16">6.5.16</a>, see also variably modified type, <a href="#6.7.6">6.7.6</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a>
34707 indeterminately sequenced, sequenced vertical-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
34708 before vertical-tab escape sequence (\v), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
34709 unsigned char type, <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a> <a href="#7.4.1.10">7.4.1.10</a>
34710 unsigned integer suffix, u or <a href="#U">U</a>, <a href="#6.4.4.1">6.4.4.1</a> vfprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#K.3.5.3.8">K.3.5.3.8</a>
34711 unsigned integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a> vfprintf_s function, <a href="#K.3.5.3.8">K.3.5.3.8</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>,
34712 unsigned type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34713 <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> vfscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>
34714 unsigned types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, vfscanf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
34715 <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a> <a href="#K.3.5.3.14">K.3.5.3.14</a>
34716 unspecified behavior, <a href="#3.4.4">3.4.4</a>, <a href="#4">4</a>, <a href="#J.1">J.1</a> vfwprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.5">7.29.2.5</a>, <a href="#K.3.9.1.6">K.3.9.1.6</a>
34717 unspecified value, <a href="#3.19.3">3.19.3</a> vfwprintf_s function, <a href="#K.3.9.1.6">K.3.9.1.6</a>
34718 uppercase letter, <a href="#5.2.1">5.2.1</a> vfwscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.3.10">7.29.3.10</a>
34719 use of library functions, <a href="#7.1.4">7.1.4</a> vfwscanf_s function, <a href="#K.3.9.1.7">K.3.9.1.7</a>
34720 USHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> visibility of identifier, <a href="#6.2.1">6.2.1</a>
34721 usual arithmetic conversions, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.5.5">6.5.5</a>, <a href="#6.5.6">6.5.6</a>, visible sequence of side effects, <a href="#5.1.2.4">5.1.2.4</a>
34722 <a href="#6.5.8">6.5.8</a>, <a href="#6.5.9">6.5.9</a>, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a>, <a href="#6.5.15">6.5.15</a> visible side effect, <a href="#5.1.2.4">5.1.2.4</a>
34725 UTF-8 string literal, see string literal void function parameter, <a href="#6.7.6.3">6.7.6.3</a>
34726 utilities, general, <a href="#7.22">7.22</a>, <a href="#7.31.12">7.31.12</a>, <a href="#K.3.6">K.3.6</a> void type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.2">6.3.2.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>,
34727 wide string, <a href="#7.29.4">7.29.4</a>, <a href="#K.3.9.2">K.3.9.2</a> <a href="#K.3.9.1.2">K.3.9.1.2</a>
34728 utilities, unicode, <a href="#7.28">7.28</a> void type conversion, <a href="#6.3.2.2">6.3.2.2</a>
34730 va_arg macro, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.1">7.16.1.1</a>, <a href="#7.16.1.2">7.16.1.2</a>, volatile type qualifier, <a href="#6.7.3">6.7.3</a>
34731 <a href="#7.16.1.4">7.16.1.4</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>, volatile-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a>
34732 <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>, vprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.10">7.21.6.10</a>,
34733 <a href="#7.29.2.5">7.29.2.5</a>, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.7">7.29.2.7</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#K.3.5.3.10">K.3.5.3.10</a>
34734 <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.10">7.29.2.10</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, vprintf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.10">K.3.5.3.10</a>,
34735 <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a> <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34736 va_copy macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.1">7.16.1.1</a>, vscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.11">7.21.6.11</a>
34737 <a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.3">7.16.1.3</a> vscanf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
34738 va_end macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.3">7.16.1.3</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34739 <a href="#7.16.1.4">7.16.1.4</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>, vsnprintf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.12">7.21.6.12</a>,
34740 <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>, <a href="#K.3.5.3.12">K.3.5.3.12</a>
34741 <a href="#7.29.2.5">7.29.2.5</a>, <a href="#7.29.2.6">7.29.2.6</a>, <a href="#7.29.2.7">7.29.2.7</a>, <a href="#7.29.2.8">7.29.2.8</a>, vsnprintf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
34742 <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.10">7.29.2.10</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.12">K.3.5.3.12</a>, <a href="#K.3.5.3.13">K.3.5.3.13</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34743 <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a> vsnwprintf_s function, <a href="#K.3.9.1.8">K.3.9.1.8</a>, <a href="#K.3.9.1.9">K.3.9.1.9</a>
34744 va_list type, <a href="#7.16">7.16</a>, <a href="#7.16.1.3">7.16.1.3</a> vsprintf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.13">7.21.6.13</a>,
34745 va_start macro, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.1">7.16.1.1</a>, <a href="#K.3.5.3.13">K.3.5.3.13</a>
34746 <a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.3">7.16.1.3</a>, <a href="#7.16.1.4">7.16.1.4</a>, <a href="#7.21.6.8">7.21.6.8</a>, vsprintf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
34747 <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>, <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#K.3.5.3.12">K.3.5.3.12</a>, <a href="#K.3.5.3.13">K.3.5.3.13</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34748 <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>, <a href="#7.29.2.5">7.29.2.5</a>, <a href="#7.29.2.6">7.29.2.6</a>, vsscanf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.14">7.21.6.14</a>
34749 <a href="#7.29.2.7">7.29.2.7</a>, <a href="#7.29.2.8">7.29.2.8</a>, <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.10">7.29.2.10</a>, vsscanf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
34750 <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>
34751 <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a> vswprintf function, <a href="#7.29.2.7">7.29.2.7</a>, <a href="#K.3.9.1.8">K.3.9.1.8</a>,
34753 <!--page 700 -->
34754 vswprintf_s function, <a href="#K.3.9.1.8">K.3.9.1.8</a>, <a href="#K.3.9.1.9">K.3.9.1.9</a> wcstoll function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>
34755 vswscanf function, <a href="#7.29.2.8">7.29.2.8</a> wcstombs function, <a href="#7.22.8.2">7.22.8.2</a>, <a href="#7.29.6.4">7.29.6.4</a>
34756 vswscanf_s function, <a href="#K.3.9.1.10">K.3.9.1.10</a> wcstombs_s function, <a href="#K.3.6.5.2">K.3.6.5.2</a>
34757 vwprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.9">7.29.2.9</a>, <a href="#K.3.9.1.11">K.3.9.1.11</a> wcstoul function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>,
34758 vwprintf_s function, <a href="#K.3.9.1.11">K.3.9.1.11</a> <a href="#7.29.4.1.2">7.29.4.1.2</a>
34759 vwscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.10">7.29.2.10</a>, <a href="#7.29.3.10">7.29.3.10</a> wcstoull function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.29.4.1.2">7.29.4.1.2</a>
34760 vwscanf_s function, <a href="#K.3.9.1.12">K.3.9.1.12</a> wcstoumax function, <a href="#7.8.2.4">7.8.2.4</a>
34762 warnings, <a href="#I">I</a> wctob function, <a href="#7.29.6.1.2">7.29.6.1.2</a>, <a href="#7.30.2.1">7.30.2.1</a>
34763 wchar.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.29">7.29</a>, <a href="#7.31.16">7.31.16</a>, wctomb function, <a href="#7.22.7.3">7.22.7.3</a>, <a href="#7.22.8.2">7.22.8.2</a>, <a href="#7.29.6.3">7.29.6.3</a>
34764 <a href="#F">F</a>, <a href="#K.3.9">K.3.9</a> wctomb_s function, <a href="#K.3.6.4.1">K.3.6.4.1</a>
34765 WCHAR_MAX macro, <a href="#7.20.3">7.20.3</a>, <a href="#7.29.1">7.29.1</a> wctrans function, <a href="#7.30.3.2.1">7.30.3.2.1</a>, <a href="#7.30.3.2.2">7.30.3.2.2</a>
34766 WCHAR_MIN macro, <a href="#7.20.3">7.20.3</a>, <a href="#7.29.1">7.29.1</a> wctrans_t type, <a href="#7.30.1">7.30.1</a>, <a href="#7.30.3.2.2">7.30.3.2.2</a>
34767 wchar_t type, <a href="#3.7.3">3.7.3</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.10.8.2">6.10.8.2</a>, <a href="#7.19">7.19</a>, wctype function, <a href="#7.30.2.2.1">7.30.2.2.1</a>, <a href="#7.30.2.2.2">7.30.2.2.2</a>
34768 <a href="#7.20.3">7.20.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22">7.22</a>, <a href="#7.29.1">7.29.1</a>, wctype.h header, <a href="#7.30">7.30</a>, <a href="#7.31.17">7.31.17</a>
34769 <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.2">7.29.2.2</a> wctype_t type, <a href="#7.30.1">7.30.1</a>, <a href="#7.30.2.2.2">7.30.2.2.2</a>
34770 wcrtomb function, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.1">7.29.1</a>, weaker, <a href="#6.2.8">6.2.8</a>
34771 <a href="#7.29.2.2">7.29.2.2</a>, <a href="#7.29.6.3.3">7.29.6.3.3</a>, <a href="#7.29.6.4.2">7.29.6.4.2</a>, <a href="#J.1">J.1</a>, WEOF macro, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.3.1">7.29.3.1</a>, <a href="#7.29.3.3">7.29.3.3</a>, <a href="#7.29.3.6">7.29.3.6</a>,
34772 <a href="#K.3.6.5.2">K.3.6.5.2</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a>, <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a> <a href="#7.29.3.7">7.29.3.7</a>, <a href="#7.29.3.8">7.29.3.8</a>, <a href="#7.29.3.9">7.29.3.9</a>, <a href="#7.29.3.10">7.29.3.10</a>,
34773 wcrtomb_s function, <a href="#K.3.9.3.1">K.3.9.3.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a> <a href="#7.29.6.1.1">7.29.6.1.1</a>, <a href="#7.30.1">7.30.1</a>
34774 wcscat function, <a href="#7.29.4.3.1">7.29.4.3.1</a> while statement, <a href="#6.8.5.1">6.8.5.1</a>
34775 wcscat_s function, <a href="#K.3.9.2.2.1">K.3.9.2.2.1</a> white space, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#7.4.1.10">7.4.1.10</a>,
34777 wcscmp function, <a href="#7.29.4.4.1">7.29.4.4.1</a>, <a href="#7.29.4.4.4">7.29.4.4.4</a> white-space characters, <a href="#6.4">6.4</a>
34778 wcscoll function, <a href="#7.29.4.4.2">7.29.4.4.2</a>, <a href="#7.29.4.4.4">7.29.4.4.4</a> wide character, <a href="#3.7.3">3.7.3</a>
34779 wcscpy function, <a href="#7.29.4.2.1">7.29.4.2.1</a> case mapping functions, <a href="#7.30.3.1">7.30.3.1</a>
34780 wcscpy_s function, <a href="#K.3.9.2.1.1">K.3.9.2.1.1</a> extensible, <a href="#7.30.3.2">7.30.3.2</a>
34781 wcscspn function, <a href="#7.29.4.5.2">7.29.4.5.2</a> classification functions, <a href="#7.30.2.1">7.30.2.1</a>
34782 wcsftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.29.5.1">7.29.5.1</a> extensible, <a href="#7.30.2.2">7.30.2.2</a>
34783 wcslen function, <a href="#7.29.4.6.1">7.29.4.6.1</a> constant, <a href="#6.4.4.4">6.4.4.4</a>
34784 wcsncat function, <a href="#7.29.4.3.2">7.29.4.3.2</a> formatted input/output functions, <a href="#7.29.2">7.29.2</a>,
34786 wcsncmp function, <a href="#7.29.4.4.3">7.29.4.4.3</a> input functions, <a href="#7.21.1">7.21.1</a>
34787 wcsncpy function, <a href="#7.29.4.2.2">7.29.4.2.2</a> input/output functions, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.3">7.29.3</a>
34788 wcsncpy_s function, <a href="#K.3.9.2.1.2">K.3.9.2.1.2</a> output functions, <a href="#7.21.1">7.21.1</a>
34789 wcsnlen_s function, <a href="#K.3.9.2.4.1">K.3.9.2.4.1</a> single-byte conversion functions, <a href="#7.29.6.1">7.29.6.1</a>
34790 wcspbrk function, <a href="#7.29.4.5.3">7.29.4.5.3</a> wide character classification and mapping utilities
34791 wcsrchr function, <a href="#7.29.4.5.4">7.29.4.5.4</a> header, <a href="#7.30">7.30</a>, <a href="#7.31.17">7.31.17</a>
34792 wcsrtombs function, <a href="#7.29.6.4.2">7.29.6.4.2</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> wide string, <a href="#7.1.1">7.1.1</a>
34793 wcsrtombs_s function, <a href="#K.3.9.3.2">K.3.9.3.2</a>, <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a> wide string comparison functions, <a href="#7.29.4.4">7.29.4.4</a>
34794 wcsspn function, <a href="#7.29.4.5.5">7.29.4.5.5</a> wide string concatenation functions, <a href="#7.29.4.3">7.29.4.3</a>,
34796 wcstod function, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a> wide string copying functions, <a href="#7.29.4.2">7.29.4.2</a>, <a href="#K.3.9.2.1">K.3.9.2.1</a>
34798 wcstof function, <a href="#7.29.4.1.1">7.29.4.1.1</a> wide string miscellaneous functions, <a href="#7.29.4.6">7.29.4.6</a>,
34800 wcstok function, <a href="#7.29.4.5.7">7.29.4.5.7</a> wide string numeric conversion functions, <a href="#7.8.2.4">7.8.2.4</a>,
34802 wcstol function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.29.2.2">7.29.2.2</a>, wide string search functions, <a href="#7.29.4.5">7.29.4.5</a>, <a href="#K.3.9.2.3">K.3.9.2.3</a>
34805 <!--page 701 -->
34808 wint_t type, <a href="#7.20.3">7.20.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.1">7.29.2.1</a>,
34817 wprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.9">7.29.2.9</a>, <a href="#7.29.2.11">7.29.2.11</a>,
34820 wscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.29.2.10">7.29.2.10</a>, <a href="#7.29.2.12">7.29.2.12</a>,
34826 </pre>
34828 </body></html>