| blob | 6502e1f38fc038edb2365d7c53478b6b7cf9b4a8 |
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 (N1256) 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>
308 <ul>
315 </ul>
318 <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="#7.29"> 7.29 Wide character classification and mapping utilities <wctype.h></a>
362 <ul>
365 <ul>
368 </ul>
370 <ul>
373 </ul>
374 </ul>
376 <ul>
388 <!--page 9 -->
389 <li><a href="#7.30.12"> 7.30.12 Extended multibyte and wide character utilities <wchar.h></a>
390 <li><a href="#7.30.13"> 7.30.13 Wide character classification and mapping utilities <wctype.h></a>
391 </ul>
392 </ul>
394 <ul>
398 </ul>
400 <ul>
428 <li><a href="#B.28"> B.28 Wide character classification and mapping utilities <wctype.h></a>
429 </ul>
432 <ul>
435 </ul>
437 <!--page 10 -->
439 <ul>
450 <ul>
462 </ul>
463 </ul>
465 <ul>
470 <ul>
474 </ul>
476 <ul>
479 </ul>
481 <ul>
486 </ul>
488 </ul>
490 <ul>
494 <!--page 11 -->
495 </ul>
498 <ul>
504 </ul>
506 <ul>
510 <ul>
512 <ul>
517 </ul>
522 <ul>
527 </ul>
529 <ul>
535 </ul>
537 <ul>
542 </ul>
544 <ul>
547 </ul>
549 <ul>
552 <!--page 12 -->
554 </ul>
555 </ul>
556 </ul>
558 <ul>
562 </ul>
565 <!--page 13 -->
566 </ul>
571 ISO (the International Organization for Standardization) and IEC (the International
572 Electrotechnical Commission) form the specialized system for worldwide
573 standardization. National bodies that are member of ISO or IEC participate in the
574 development of International Standards through technical committees established by the
575 respective organization to deal with particular fields of technical activity. ISO and IEC
576 technical committees collaborate in fields of mutual interest. Other international
577 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
578 take part in the work.
580 International Standards are drafted in accordance with the rules given in the ISO/IEC
581 Directives, Part 2. This International Standard was drafted in accordance with the fifth
582 edition (2004).
584 In the field of information technology, ISO and IEC have established a joint technical
585 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
586 committee are circulated to national bodies for voting. Publication as an International
587 Standard requires approval by at least 75% of the national bodies casting a vote.
589 Attention is drawn to the possibility that some of the elements of this document may be
590 the subject of patent rights. ISO and IEC shall not be held responsible for identifying any
591 or all such patent rights.
593 This International Standard was prepared by Joint Technical Committee ISO/IEC JTC 1,
594 Information technology, Subcommittee SC 22, Programming languages, their
595 environments and system software interfaces. The Working Group responsible for this
596 standard (WG 14) maintains a site on the World Wide Web at http://www.open-
597 std.org/JTC1/SC22/WG14/ containing additional information relevant to this
598 standard such as a Rationale for many of the decisions made during its preparation and a
599 log of Defect Reports and Responses.
604 <ul>
605 <li> conditional (optional) features (including some that were previously mandatory)
606 <li> support for multiple threads of execution including an improved memory sequencing
610 <li> querying and specifying alignment of objects (<a href="#7.15"><stdalign.h></a>, <a href="#7.22"><stdlib.h></a>)
611 <li> Unicode characters and strings (<a href="#7.27"><uchar.h></a>) (originally specified in
613 <li> type-generic expressions
614 <!--page 14 -->
615 <li> static assertions
616 <li> anonymous structures and unions
617 <li> no-return functions
619 <li> support for opening files for exclusive access
621 <li> added the aligned_alloc, at_quick_exit, and quick_exit functions
623 <li> (conditional) support for bounds-checking interfaces (originally specified in
625 <li> (conditional) support for analyzability
626 </ul>
628 Major changes in the second edition included:
629 <ul>
630 <li> restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
631 in AMD1)
632 <li> wide character library support in <a href="#7.28"><wchar.h></a> and <a href="#7.29"><wctype.h></a> (originally
633 specified in AMD1)
634 <li> more precise aliasing rules via effective type
635 <li> restricted pointers
636 <li> variable length arrays
637 <li> flexible array members
638 <li> static and type qualifiers in parameter array declarators
641 <li> the long long int type and library functions
642 <li> increased minimum translation limits
644 <li> remove implicit int
645 <li> reliable integer division
646 <li> universal character names (\u and \U)
647 <li> extended identifiers
648 <li> hexadecimal floating-point constants and %a and %A printf/scanf conversion
649 specifiers
650 <!--page 15 -->
651 <li> compound literals
652 <li> designated initializers
653 <li> // comments
654 <li> extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.20"><stdint.h></a>
655 <li> remove implicit function declaration
656 <li> preprocessor arithmetic done in intmax_t/uintmax_t
657 <li> mixed declarations and code
658 <li> new block scopes for selection and iteration statements
659 <li> integer constant type rules
660 <li> integer promotion rules
661 <li> macros with a variable number of arguments
662 <li> the vscanf family of functions in <a href="#7.21"><stdio.h></a> and <a href="#7.28"><wchar.h></a>
664 <li> treatment of error conditions by math library functions (math_errhandling)
667 <li> trailing comma allowed in enum declaration
668 <li> %lf conversion specifier allowed in printf
669 <li> inline functions
672 <li> idempotent type qualifiers
673 <li> empty macro arguments
674 <li> new structure type compatibility rules (tag compatibility)
675 <li> additional predefined macro names
676 <li> _Pragma preprocessing operator
677 <li> standard pragmas
678 <li> __func__ predefined identifier
679 <li> va_copy macro
680 <li> additional strftime conversion specifiers
681 <li> LIA compatibility annex
682 <!--page 16 -->
683 <li> deprecate ungetc at the beginning of a binary file
684 <li> remove deprecation of aliased array parameters
685 <li> conversion of array to pointer not limited to lvalues
686 <li> relaxed constraints on aggregate and union initialization
687 <li> relaxed restrictions on portable header names
688 <li> return without expression not permitted in function that returns a value (and vice
689 versa)
690 </ul>
692 Annexes D, F, G, K, and L form a normative part of this standard; annexes A, B, C, E, H, *
693 I, J, the bibliography, and the index are for information only. In accordance with Part 2 of
694 the ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples
695 are also for information only.
696 <!--page 17 -->
701 With the introduction of new devices and extended character sets, new features may be
702 added to this International Standard. Subclauses in the language and library clauses warn
703 implementors and programmers of usages which, though valid in themselves, may
704 conflict with future additions.
706 Certain features are obsolescent, which means that they may be considered for
707 withdrawal in future revisions of this International Standard. They are retained because
708 of their widespread use, but their use in new implementations (for implementation
709 features) or new programs (for language [<a href="#6.11">6.11</a>] or library features [<a href="#7.30">7.30</a>]) is discouraged.
711 This International Standard is divided into four major subdivisions:
712 <ul>
717 </ul>
719 Examples are provided to illustrate possible forms of the constructions described.
720 Footnotes are provided to emphasize consequences of the rules described in that
721 subclause or elsewhere in this International Standard. References are used to refer to
722 other related subclauses. Recommendations are provided to give advice or guidance to
723 implementors. Annexes provide additional information and summarize the information
724 contained in this International Standard. A bibliography lists documents that were
725 referred to during the preparation of the standard.
727 The language clause (clause 6) is derived from ''The C Reference Manual''.
730 <!--page 18 -->
731 <!--page 19 -->
742 This International Standard specifies the form and establishes the interpretation of
743 programs written in the C programming language.<sup><a href="#note1"><b>1)</b></a></sup> It specifies
744 <ul>
745 <li> the representation of C programs;
746 <li> the syntax and constraints of the C language;
747 <li> the semantic rules for interpreting C programs;
748 <li> the representation of input data to be processed by C programs;
749 <li> the representation of output data produced by C programs;
750 <li> the restrictions and limits imposed by a conforming implementation of C.
751 </ul>
753 This International Standard does not specify
754 <ul>
755 <li> the mechanism by which C programs are transformed for use by a data-processing
756 system;
757 <li> the mechanism by which C programs are invoked for use by a data-processing
758 system;
759 <li> the mechanism by which input data are transformed for use by a C program;
760 <li> the mechanism by which output data are transformed after being produced by a C
761 program;
762 <li> the size or complexity of a program and its data that will exceed the capacity of any
763 specific data-processing system or the capacity of a particular processor;
764 <li> all minimal requirements of a data-processing system that is capable of supporting a
765 conforming implementation.
768 <!--page 20 -->
769 </ul>
772 <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
773 data-processing systems. It is intended for use by implementors and programmers.
774 </small>
779 The following referenced documents are indispensable for the application of this
780 document. For dated references, only the edition cited applies. For undated references,
781 the latest edition of the referenced document (including any amendments) applies.
784 use in the physical sciences and technology.
787 interchange.
790 terms.
792 ISO 4217, Codes for the representation of currencies and funds.
794 ISO 8601, Data elements and interchange formats -- Information interchange --
795 Representation of dates and times.
797 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
798 Character Set (UCS).
802 <!--page 21 -->
807 For the purposes of this International Standard, the following definitions apply. Other
808 terms are defined where they appear in italic type or on the left side of a syntax rule.
809 Terms explicitly defined in this International Standard are not to be presumed to refer
810 implicitly to similar terms defined elsewhere. Terms not defined in this International
820 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
823 NOTE 2 ''Modify'' includes the case where the new value being stored is the same as the previous value.
826 NOTE 3 Expressions that are not evaluated do not access objects.
833 requirement that objects of a particular type be located on storage boundaries with
834 addresses that are particular multiples of a byte address
840 actual argument
841 actual parameter (deprecated)
842 expression in the comma-separated list bounded by the parentheses in a function call
843 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
844 by the parentheses in a function-like macro invocation
850 external appearance or action
856 unspecified behavior where each implementation documents how the choice is made
858 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
859 when a signed integer is shifted right.
866 behavior that depends on local conventions of nationality, culture, and language that each
867 implementation documents
868 <!--page 22 -->
870 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
871 characters other than the 26 lowercase Latin letters.
878 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
879 for which this International Standard imposes no requirements
881 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
882 results, to behaving during translation or program execution in a documented manner characteristic of the
883 environment (with or without the issuance of a diagnostic message), to terminating a translation or
884 execution (with the issuance of a diagnostic message).
887 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
894 use of an unspecified value, or other behavior where this International Standard provides
895 two or more possibilities and imposes no further requirements on which is chosen in any
896 instance
898 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
899 evaluated.
906 unit of data storage in the execution environment large enough to hold an object that may
907 have one of two values
909 NOTE It need not be possible to express the address of each individual bit of an object.
916 addressable unit of data storage large enough to hold any member of the basic character
917 set of the execution environment
919 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
922 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
923 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
924 bit.
932 representation of data
938 single-byte character
940 <!--page 23 -->
946 sequence of one or more bytes representing a member of the extended character set of
947 either the source or the execution environment
949 NOTE The extended character set is a superset of the basic character set.
956 bit representation that fits in an object of type wchar_t, capable of representing any
957 character in the current locale
963 restriction, either syntactic or semantic, by which the exposition of language elements is
964 to be interpreted
970 representation in the result format that is nearest in value, subject to the current rounding
971 mode, to what the result would be given unlimited range and precision
977 message belonging to an implementation-defined subset of the implementation's message
978 output
984 reference to a later subclause of this International Standard that contains additional
985 information relevant to this subclause
991 particular set of software, running in a particular translation environment under particular
992 control options, that performs translation of programs for, and supports execution of
993 functions in, a particular execution environment
999 restriction imposed upon programs by the implementation
1005 either an object of scalar type, or a maximal sequence of adjacent bit-fields all having
1006 nonzero width
1007 <!--page 24 -->
1009 NOTE 1 Two threads of execution can update and access separate memory locations without interfering
1010 with each other.
1013 NOTE 2 A bit-field and an adjacent non-bit-field member are in separate memory locations. The same
1014 applies to two bit-fields, if one is declared inside a nested structure declaration and the other is not, or if the
1015 two are separated by a zero-length bit-field declaration, or if they are separated by a non-bit-field member
1016 declaration. It is not safe to concurrently update two non-atomic bit-fields in the same structure if all
1017 members declared between them are also (non-zero-length) bit-fields, no matter what the sizes of those
1018 intervening bit-fields happen to be.
1021 EXAMPLE A structure declared as
1022 <pre>
1023 struct {
1024 char a;
1026 struct { int ee:8; } e;
1027 }
1028 </pre>
1029 contains four separate memory locations: The member a, and bit-fields d and e.ee are each separate
1030 memory locations, and can be modified concurrently without interfering with each other. The bit-fields b
1031 and c together constitute the fourth memory location. The bit-fields b and c cannot be concurrently
1032 modified, but b and a, for example, can be.
1039 region of data storage in the execution environment, the contents of which can represent
1040 values
1042 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>.
1049 formal parameter
1050 formal argument (deprecated)
1051 object declared as part of a function declaration or definition that acquires a value on
1052 entry to the function, or an identifier from the comma-separated list bounded by the
1053 parentheses immediately following the macro name in a function-like macro definition
1059 specification that is strongly recommended as being in keeping with the intent of the
1060 standard, but that may be impractical for some implementations
1066 requirement on a program when calling a library function
1068 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
1069 need not be diagnosed at translation time.
1072 NOTE 2 Implementations that support the extensions in <a href="#K">annex K</a> are required to verify that the runtime-
1073 constraints for a library function are not violated by the program; see <a href="#K.3.1.4">K.3.1.4</a>.
1074 <!--page 25 -->
1080 precise meaning of the contents of an object when interpreted as having a specific type
1086 unspecified value where each implementation documents how the choice is made
1092 either an unspecified value or a trap representation
1098 valid value of the relevant type where this International Standard imposes no
1099 requirements on which value is chosen in any instance
1101 NOTE An unspecified value cannot be a trap representation.
1108 an object representation that need not represent a value of the object type
1114 interrupt execution of the program such that no further operations are performed
1116 NOTE In this International Standard, when the word ''trap'' is not immediately followed by
1121 <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
1122 representation might perform a trap but is not required to (see <a href="#6.2.6.1">6.2.6.1</a>).
1123 </small>
1129 ceiling of x: the least integer greater than or equal to x
1138 floor of x: the greatest integer less than or equal to x
1145 <!--page 26 -->
1150 In this International Standard, ''shall'' is to be interpreted as a requirement on an
1151 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
1152 prohibition.
1154 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint or runtime-
1155 constraint is violated, the behavior is undefined. Undefined behavior is otherwise
1156 indicated in this International Standard by the words ''undefined behavior'' or by the
1157 omission of any explicit definition of behavior. There is no difference in emphasis among
1158 these three; they all describe ''behavior that is undefined''.
1160 A program that is correct in all other aspects, operating on correct data, containing
1161 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
1163 The implementation shall not successfully translate a preprocessing translation unit
1164 containing a #error preprocessing directive unless it is part of a group skipped by
1165 conditional inclusion.
1167 A strictly conforming program shall use only those features of the language and library
1168 specified in this International Standard.<sup><a href="#note3"><b>3)</b></a></sup> It shall not produce output dependent on any
1169 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
1170 minimum implementation limit.
1172 The two forms of conforming implementation are hosted and freestanding. A conforming
1173 hosted implementation shall accept any strictly conforming program. A conforming
1174 freestanding implementation shall accept any strictly conforming program that does not
1175 use complex types and in which the use of the features specified in the library clause
1176 (clause 7) is confined to the contents of the standard headers <a href="#7.7"><float.h></a>,
1177 <a href="#7.9"><iso646.h></a>, <a href="#7.10"><limits.h></a>, <a href="#7.15"><stdalign.h></a>, <a href="#7.16"><stdarg.h></a>, <a href="#7.18"><stdbool.h></a>,
1178 <a href="#7.19"><stddef.h></a>, and <a href="#7.20"><stdint.h></a>. A conforming implementation may have extensions
1179 (including additional library functions), provided they do not alter the behavior of any
1184 <!--page 27 -->
1186 A conforming program is one that is acceptable to a conforming implementation.<sup><a href="#note5"><b>5)</b></a></sup>
1188 An implementation shall be accompanied by a document that defines all implementation-
1189 defined and locale-specific characteristics and all extensions.
1190 <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>),
1191 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>
1192 (<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>),
1193 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>
1194 (<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>).
1199 <!--page 28 -->
1202 <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
1203 by an appropriate conditional inclusion preprocessing directive using the related macro. For example:
1205 <pre>
1206 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
1207 /* ... */
1208 fesetround(FE_UPWARD);
1209 /* ... */
1210 #endif
1211 </pre>
1213 </small>
1214 <p><small><a name="note4" href="#note4">4)</a> This implies that a conforming implementation reserves no identifiers other than those explicitly
1215 reserved in this International Standard.
1216 </small>
1217 <p><small><a name="note5" href="#note5">5)</a> Strictly conforming programs are intended to be maximally portable among conforming
1218 implementations. Conforming programs may depend upon nonportable features of a conforming
1219 implementation.
1220 </small>
1225 An implementation translates C source files and executes C programs in two data-
1226 processing-system environments, which will be called the translation environment and
1227 the execution environment in this International Standard. Their characteristics define and
1228 constrain the results of executing conforming C programs constructed according to the
1229 syntactic and semantic rules for conforming implementations.
1231 have been noted.
1242 A C program need not all be translated at the same time. The text of the program is kept
1243 in units called source files, (or preprocessing files) in this International Standard. A
1244 source file together with all the headers and source files included via the preprocessing
1245 directive #include is known as a preprocessing translation unit. After preprocessing, a
1246 preprocessing translation unit is called a translation unit. Previously translated translation
1247 units may be preserved individually or in libraries. The separate translation units of a
1248 program communicate by (for example) calls to functions whose identifiers have external
1249 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
1250 of data files. Translation units may be separately translated and then later linked to
1251 produce an executable program.
1252 <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>),
1258 The precedence among the syntax rules of translation is specified by the following
1260 <ol>
1261 <li> Physical source file multibyte characters are mapped, in an implementation-
1262 defined manner, to the source character set (introducing new-line characters for
1263 end-of-line indicators) if necessary. Trigraph sequences are replaced by
1264 corresponding single-character internal representations.
1268 <!--page 29 -->
1269 <li> Each instance of a backslash character (\) immediately followed by a new-line
1270 character is deleted, splicing physical source lines to form logical source lines.
1271 Only the last backslash on any physical source line shall be eligible for being part
1272 of such a splice. A source file that is not empty shall end in a new-line character,
1273 which shall not be immediately preceded by a backslash character before any such
1274 splicing takes place.
1275 <li> The source file is decomposed into preprocessing tokens<sup><a href="#note7"><b>7)</b></a></sup> and sequences of
1276 white-space characters (including comments). A source file shall not end in a
1277 partial preprocessing token or in a partial comment. Each comment is replaced by
1278 one space character. New-line characters are retained. Whether each nonempty
1279 sequence of white-space characters other than new-line is retained or replaced by
1280 one space character is implementation-defined.
1281 <li> Preprocessing directives are executed, macro invocations are expanded, and
1282 _Pragma unary operator expressions are executed. If a character sequence that
1283 matches the syntax of a universal character name is produced by token
1284 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
1285 directive causes the named header or source file to be processed from phase 1
1286 through phase 4, recursively. All preprocessing directives are then deleted.
1287 <li> Each source character set member and escape sequence in character constants and
1288 string literals is converted to the corresponding member of the execution character
1289 set; if there is no corresponding member, it is converted to an implementation-
1291 <li> Adjacent string literal tokens are concatenated.
1292 <li> White-space characters separating tokens are no longer significant. Each
1293 preprocessing token is converted into a token. The resulting tokens are
1294 syntactically and semantically analyzed and translated as a translation unit.
1295 <li> All external object and function references are resolved. Library components are
1296 linked to satisfy external references to functions and objects not defined in the
1297 current translation. All such translator output is collected into a program image
1298 which contains information needed for execution in its execution environment.
1299 </ol>
1300 <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>),
1301 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>).
1305 <!--page 30 -->
1308 <p><small><a name="note6" href="#note6">6)</a> Implementations shall behave as if these separate phases occur, even though many are typically folded
1309 together in practice. Source files, translation units, and translated translation units need not
1310 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
1311 and any external representation. The description is conceptual only, and does not specify any
1312 particular implementation.
1313 </small>
1314 <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
1315 context-dependent. For example, see the handling of < within a #include preprocessing directive.
1316 </small>
1317 <p><small><a name="note8" href="#note8">8)</a> An implementation need not convert all non-corresponding source characters to the same execution
1318 character.
1319 </small>
1324 A conforming implementation shall produce at least one diagnostic message (identified in
1325 an implementation-defined manner) if a preprocessing translation unit or translation unit
1326 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1327 specified as undefined or implementation-defined. Diagnostic messages need not be
1330 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1331 <pre>
1332 char i;
1333 int i;
1334 </pre>
1335 because in those cases where wording in this International Standard describes the behavior for a construct
1336 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1340 <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
1341 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1342 valid program is still correctly translated. It may also successfully translate an invalid program.
1343 </small>
1348 Two execution environments are defined: freestanding and hosted. In both cases,
1349 program startup occurs when a designated C function is called by the execution
1350 environment. All objects with static storage duration shall be initialized (set to their
1351 initial values) before program startup. The manner and timing of such initialization are
1352 otherwise unspecified. Program termination returns control to the execution
1353 environment.
1354 <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>).
1359 In a freestanding environment (in which C program execution may take place without any
1360 benefit of an operating system), the name and type of the function called at program
1361 startup are implementation-defined. Any library facilities available to a freestanding
1362 program, other than the minimal set required by clause 4, are implementation-defined.
1364 The effect of program termination in a freestanding environment is implementation-
1365 defined.
1370 A hosted environment need not be provided, but shall conform to the following
1371 specifications if present.
1376 <!--page 31 -->
1381 The function called at program startup is named main. The implementation declares no
1382 prototype for this function. It shall be defined with a return type of int and with no
1383 parameters:
1384 <pre>
1385 int main(void) { /* ... */ }
1386 </pre>
1387 or with two parameters (referred to here as argc and argv, though any names may be
1388 used, as they are local to the function in which they are declared):
1389 <pre>
1390 int main(int argc, char *argv[]) { /* ... */ }
1391 </pre>
1392 or equivalent;<sup><a href="#note10"><b>10)</b></a></sup> or in some other implementation-defined manner.
1394 If they are declared, the parameters to the main function shall obey the following
1395 constraints:
1396 <ul>
1397 <li> The value of argc shall be nonnegative.
1398 <li> argv[argc] shall be a null pointer.
1400 argv[argc-1] inclusive shall contain pointers to strings, which are given
1401 implementation-defined values by the host environment prior to program startup. The
1402 intent is to supply to the program information determined prior to program startup
1403 from elsewhere in the hosted environment. If the host environment is not capable of
1404 supplying strings with letters in both uppercase and lowercase, the implementation
1405 shall ensure that the strings are received in lowercase.
1408 program name is not available from the host environment. If the value of argc is
1410 represent the program parameters.
1411 <li> The parameters argc and argv and the strings pointed to by the argv array shall
1412 be modifiable by the program, and retain their last-stored values between program
1413 startup and program termination.
1414 </ul>
1417 <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
1418 char ** argv, and so on.
1419 </small>
1424 In a hosted environment, a program may use all the functions, macros, type definitions,
1425 and objects described in the library clause (clause 7).
1430 <!--page 32 -->
1435 If the return type of the main function is a type compatible with int, a return from the
1436 initial call to the main function is equivalent to calling the exit function with the value
1437 returned by the main function as its argument;<sup><a href="#note11"><b>11)</b></a></sup> reaching the } that terminates the
1438 main function returns a value of 0. If the return type is not compatible with int, the
1439 termination status returned to the host environment is unspecified.
1440 <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>).
1443 <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
1444 will have ended in the former case, even where they would not have in the latter.
1445 </small>
1450 The semantic descriptions in this International Standard describe the behavior of an
1451 abstract machine in which issues of optimization are irrelevant.
1453 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1454 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
1455 the execution environment. Evaluation of an expression in general includes both value
1456 computations and initiation of side effects. Value computation for an lvalue expression
1457 includes determining the identity of the designated object.
1459 Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations
1460 executed by a single thread, which induces a partial order among those evaluations.
1461 Given any two evaluations A and B, if A is sequenced before B, then the execution of A
1462 shall precede the execution of B. (Conversely, if A is sequenced before B, then B is
1463 sequenced after A.) If A is not sequenced before or after B, then A and B are
1464 unsequenced. Evaluations A and B are indeterminately sequenced when A is sequenced
1465 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
1466 between the evaluation of expressions A and B implies that every value computation and
1467 side effect associated with A is sequenced before every value computation and side effect
1470 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1471 actual implementation need not evaluate part of an expression if it can deduce that its
1472 value is not used and that no needed side effects are produced (including any caused by
1474 <!--page 33 -->
1475 calling a function or accessing a volatile object).
1477 When the processing of the abstract machine is interrupted by receipt of a signal, the
1478 values of objects that are neither lock-free atomic objects nor of type volatile
1479 sig_atomic_t are unspecified, and the value of any object that is modified by the
1480 handler that is neither a lock-free atomic object nor of type volatile
1481 sig_atomic_t becomes undefined.
1483 The least requirements on a conforming implementation are:
1484 <ul>
1485 <li> Accesses to volatile objects are evaluated strictly according to the rules of the abstract
1486 machine.
1487 <li> At program termination, all data written into files shall be identical to the result that
1488 execution of the program according to the abstract semantics would have produced.
1489 <li> The input and output dynamics of interactive devices shall take place as specified in
1490 <a href="#7.21.3">7.21.3</a>. The intent of these requirements is that unbuffered or line-buffered output
1491 appear as soon as possible, to ensure that prompting messages actually appear prior to
1492 a program waiting for input.
1493 </ul>
1494 This is the observable behavior of the program.
1496 What constitutes an interactive device is implementation-defined.
1498 More stringent correspondences between abstract and actual semantics may be defined by
1499 each implementation.
1501 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1502 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1503 abstract semantics. The keyword volatile would then be redundant.
1505 Alternatively, an implementation might perform various optimizations within each translation unit, such
1506 that the actual semantics would agree with the abstract semantics only when making function calls across
1507 translation unit boundaries. In such an implementation, at the time of each function entry and function
1508 return where the calling function and the called function are in different translation units, the values of all
1509 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1510 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1511 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1512 type of implementation, objects referred to by interrupt service routines activated by the signal function
1513 would require explicit specification of volatile storage, as well as other implementation-defined
1514 restrictions.
1517 EXAMPLE 2 In executing the fragment
1518 <pre>
1519 char c1, c2;
1520 /* ... */
1521 c1 = c1 + c2;
1522 </pre>
1523 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1524 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1525 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1526 produce the same result, possibly omitting the promotions.
1527 <!--page 34 -->
1529 EXAMPLE 3 Similarly, in the fragment
1530 <pre>
1531 float f1, f2;
1532 double d;
1533 /* ... */
1534 f1 = f2 * d;
1535 </pre>
1536 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1537 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1538 were replaced by the constant 2.0, which has type double).
1541 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1542 semantics. Values are independent of whether they are represented in a register or in memory. For
1543 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1544 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1545 perform their specified conversion. For the fragment
1546 <pre>
1547 double d1, d2;
1548 float f;
1549 d1 = f = expression;
1550 d2 = (float) expression;
1551 </pre>
1552 the values assigned to d1 and d2 are required to have been converted to float.
1555 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1556 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1557 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1558 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1559 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1561 <pre>
1562 double x, y, z;
1563 /* ... */
1564 x = (x * y) * z; // not equivalent to x *= y * z;
1565 z = (x - y) + y ; // not equivalent to z = x;
1566 z = x + x * y; // not equivalent to z = x * (1.0 + y);
1568 </pre>
1571 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1572 <pre>
1573 int a, b;
1574 /* ... */
1576 </pre>
1577 the expression statement behaves exactly the same as
1578 <pre>
1580 </pre>
1581 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1582 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1583 which overflows produce an explicit trap and in which the range of values representable by an int is
1585 <pre>
1586 a = ((a + b) + 32765);
1587 </pre>
1588 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1589 while the original expression would not; nor can the expression be rewritten either as
1590 <!--page 35 -->
1591 <pre>
1592 a = ((a + 32765) + b);
1593 </pre>
1594 or
1595 <pre>
1596 a = (a + (b + 32765));
1597 </pre>
1598 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1599 in which overflow silently generates some value and where positive and negative overflows cancel, the
1600 above expression statement can be rewritten by the implementation in any of the above ways because the
1601 same result will occur.
1604 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1605 following fragment
1606 <pre>
1608 int sum;
1609 char *p;
1610 /* ... */
1612 </pre>
1613 the expression statement is grouped as if it were written as
1614 <pre>
1616 </pre>
1617 but the actual increment of p can occur at any time between the previous sequence point and the next
1618 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1619 value.
1621 <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>), the
1625 <p><small><a name="note12" href="#note12">12)</a> The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
1626 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1627 values of floating-point operations. Implementations that support such floating-point state are
1628 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1629 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1630 effects matter, freeing the implementations in other cases.
1631 </small>
1632 <p><small><a name="note13" href="#note13">13)</a> The executions of unsequenced evaluations can interleave. Indeterminately sequenced evaluations
1633 cannot interleave, but can be executed in any order.
1634 </small>
1637 <h5><a name="5.1.2.4" href="#5.1.2.4">5.1.2.4 Multi-threaded executions and data races</a></h5>
1639 Under a hosted implementation, a program can have more than one thread of execution
1640 (or thread) running concurrently. The execution of each thread proceeds as defined by
1641 the remainder of this standard. The execution of the entire program consists of an
1642 execution of all of its threads.<sup><a href="#note14"><b>14)</b></a></sup> Under a freestanding implementation, it is
1643 implementation-defined whether a program can have more than one thread of execution.
1645 The value of an object visible to a thread T at a particular point is the initial value of the
1646 object, a value stored in the object by T , or a value stored in the object by another thread,
1647 according to the rules below.
1649 NOTE 1 In some cases, there may instead be undefined behavior. Much of this section is motivated by
1650 the desire to support atomic operations with explicit and detailed visibility constraints. However, it also
1651 implicitly supports a simpler view for more restricted programs.
1654 Two expression evaluations conflict if one of them modifies a memory location and the
1655 other one reads or modifies the same memory location.
1660 <!--page 36 -->
1662 The library defines a number of atomic operations (<a href="#7.17">7.17</a>) and operations on mutexes
1663 (<a href="#7.25.4">7.25.4</a>) that are specially identified as synchronization operations. These operations play
1664 a special role in making assignments in one thread visible to another. A synchronization
1665 operation on one or more memory locations is either an acquire operation, a release
1666 operation, both an acquire and release operation, or a consume operation. A
1667 synchronization operation without an associated memory location is a fence and can be
1668 either an acquire fence, a release fence, or both an acquire and release fence. In addition,
1669 there are relaxed atomic operations, which are not synchronization operations, and
1670 atomic read-modify-write operations, which have special characteristics.
1672 NOTE 2 For example, a call that acquires a mutex will perform an acquire operation on the locations
1673 composing the mutex. Correspondingly, a call that releases the same mutex will perform a release
1674 operation on those same locations. Informally, performing a release operation on A forces prior side effects
1675 on other memory locations to become visible to other threads that later perform an acquire or consume
1676 operation on A. We do not include relaxed atomic operations as synchronization operations although, like
1677 synchronization operations, they cannot contribute to data races.
1680 All modifications to a particular atomic object M occur in some particular total order,
1681 called the modification order of M. If A and B are modifications of an atomic object M,
1682 and A happens before B, then A shall precede B in the modification order of M, which is
1683 defined below.
1685 NOTE 3 This states that the modification orders must respect the ''happens before'' relation.
1688 NOTE 4 There is a separate order for each atomic object. There is no requirement that these can be
1689 combined into a single total order for all objects. In general this will be impossible since different threads
1690 may observe modifications to different variables in inconsistent orders.
1693 A release sequence on an atomic object M is a maximal contiguous sub-sequence of side
1694 effects in the modification order of M, where the first operation is a release and every
1695 subsequent operation either is performed by the same thread that performed the release or
1696 is an atomic read-modify-write operation.
1698 Certain library calls synchronize with other library calls performed by another thread. In
1699 particular, an atomic operation A that performs a release operation on an object M
1700 synchronizes with an atomic operation B that performs an acquire operation on M and
1701 reads a value written by any side effect in the release sequence headed by A.
1703 NOTE 5 Except in the specified cases, reading a later value does not necessarily ensure visibility as
1704 described below. Such a requirement would sometimes interfere with efficient implementation.
1707 NOTE 6 The specifications of the synchronization operations define when one reads the value written by
1708 another. For atomic variables, the definition is clear. All operations on a given mutex occur in a single total
1709 order. Each mutex acquisition ''reads the value written'' by the last mutex release.
1712 An evaluation A carries a dependency <sup><a href="#note15"><b>15)</b></a></sup> to an evaluation B if:
1715 <!--page 37 -->
1716 <ul>
1717 <li> the value of A is used as an operand of B, unless:
1718 <ul>
1719 <li> B is an invocation of the kill_dependency macro,
1723 <li> A is the left operand of a ? : operator, or
1725 <li> A is the left operand of a , operator;
1726 </ul>
1727 or
1728 <li> A writes a scalar object or bit-field M, B reads from M the value written by A, and A
1729 is sequenced before B, or
1730 <li> for some evaluation X, A carries a dependency to X and X carries a dependency to B.
1731 </ul>
1733 An evaluation A is dependency-ordered before<sup><a href="#note16"><b>16)</b></a></sup> an evaluation B if:
1734 <ul>
1735 <li> A performs a release operation on an atomic object M, and B performs a consume
1736 operation on M and reads a value written by any side effect in the release sequence
1737 headed by A, or
1738 <li> for some evaluation X, A is dependency-ordered before X and X carries a
1739 dependency to B.
1740 </ul>
1742 An evaluation A inter-thread happens before an evaluation B if A synchronizes with B, A
1743 is dependency-ordered before B, or, for some evaluation X:
1744 <ul>
1745 <li> A synchronizes with X and X is sequenced before B,
1746 <li> A is sequenced before X and X inter-thread happens before B, or
1747 <li> A inter-thread happens before X and X inter-thread happens before B.
1748 </ul>
1750 NOTE 7 The ''inter-thread happens before'' relation describes arbitrary concatenations of ''sequenced
1751 before'', ''synchronizes with'', and ''dependency-ordered before'' relationships, with two exceptions. The
1752 first exception is that a concatenation is not permitted to end with ''dependency-ordered before'' followed
1753 by ''sequenced before''. The reason for this limitation is that a consume operation participating in a
1754 ''dependency-ordered before'' relationship provides ordering only with respect to operations to which this
1755 consume operation actually carries a dependency. The reason that this limitation applies only to the end of
1756 such a concatenation is that any subsequent release operation will provide the required ordering for a prior
1757 consume operation. The second exception is that a concatenation is not permitted to consist entirely of
1758 ''sequenced before''. The reasons for this limitation are (1) to permit ''inter-thread happens before'' to be
1759 transitively closed and (2) the ''happens before'' relation, defined below, provides for relationships
1760 consisting entirely of ''sequenced before''.
1763 An evaluation A happens before an evaluation B if A is sequenced before B or A inter-
1764 thread happens before B.
1768 <!--page 38 -->
1770 A visible side effect A on an object M with respect to a value computation B of M
1771 satisfies the conditions:
1772 <ul>
1773 <li> A happens before B, and
1774 <li> there is no other side effect X to M such that A happens before X and X happens
1775 before B.
1776 </ul>
1777 The value of a non-atomic scalar object M, as determined by evaluation B, shall be the
1778 value stored by the visible side effect A.
1780 NOTE 8 If there is ambiguity about which side effect to a non-atomic object is visible, then there is a data
1781 race and the behavior is undefined.
1784 NOTE 9 This states that operations on ordinary variables are not visibly reordered. This is not actually
1785 detectable without data races, but it is necessary to ensure that data races, as defined here, and with suitable
1786 restrictions on the use of atomics, correspond to data races in a simple interleaved (sequentially consistent)
1787 execution.
1790 The visible sequence of side effects on an atomic object M, with respect to a value
1791 computation B of M, is a maximal contiguous sub-sequence of side effects in the
1792 modification order of M, where the first side effect is visible with respect to B, and for
1793 every subsequent side effect, it is not the case that B happens before it. The value of an
1794 atomic object M, as determined by evaluation B, shall be the value stored by some
1795 operation in the visible sequence of M with respect to B. Furthermore, if a value
1796 computation A of an atomic object M happens before a value computation B of M, and
1797 the value computed by A corresponds to the value stored by side effect X, then the value
1798 computed by B shall either equal the value computed by A, or be the value stored by side
1799 effect Y , where Y follows X in the modification order of M.
1801 NOTE 10 This effectively disallows compiler reordering of atomic operations to a single object, even if
1802 both operations are ''relaxed'' loads. By doing so, we effectively make the ''cache coherence'' guarantee
1803 provided by most hardware available to C atomic operations.
1806 NOTE 11 The visible sequence depends on the ''happens before'' relation, which in turn depends on the
1807 values observed by loads of atomics, which we are restricting here. The intended reading is that there must
1808 exist an association of atomic loads with modifications they observe that, together with suitably chosen
1809 modification orders and the ''happens before'' relation derived as described above, satisfy the resulting
1810 constraints as imposed here.
1813 The execution of a program contains a data race if it contains two conflicting actions in
1814 different threads, at least one of which is not atomic, and neither happens before the
1815 other. Any such data race results in undefined behavior.
1817 NOTE 12 It can be shown that programs that correctly use simple mutexes and
1818 memory_order_seq_cst operations to prevent all data races, and use no other synchronization
1819 operations, behave as though the operations executed by their constituent threads were simply interleaved,
1820 with each value computation of an object being the last value stored in that interleaving. This is normally
1821 referred to as ''sequential consistency''. However, this applies only to data-race-free programs, and data-
1822 race-free programs cannot observe most program transformations that do not change single-threaded
1823 program semantics. In fact, most single-threaded program transformations continue to be allowed, since
1824 any program that behaves differently as a result must contain undefined behavior.
1825 <!--page 39 -->
1827 NOTE 13 Compiler transformations that introduce assignments to a potentially shared memory location
1828 that would not be modified by the abstract machine are generally precluded by this standard, since such an
1829 assignment might overwrite another assignment by a different thread in cases in which an abstract machine
1830 execution would not have encountered a data race. This includes implementations of data member
1831 assignment that overwrite adjacent members in separate memory locations. We also generally preclude
1832 reordering of atomic loads in cases in which the atomics in question may alias, since this may violate the
1833 "visible sequence" rules.
1836 NOTE 14 Transformations that introduce a speculative read of a potentially shared memory location may
1837 not preserve the semantics of the program as defined in this standard, since they potentially introduce a data
1838 race. However, they are typically valid in the context of an optimizing compiler that targets a specific
1839 machine with well-defined semantics for data races. They would be invalid for a hypothetical machine that
1840 is not tolerant of races or provides hardware race detection.
1841 <!--page 40 -->
1844 <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
1845 atomic operations, for example, allow executions inconsistent with a simple interleaving as described
1846 below.
1847 </small>
1848 <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
1849 strictly intra-thread.
1850 </small>
1851 <p><small><a name="note16" href="#note16">16)</a> The ''dependency-ordered before'' relation is analogous to the ''synchronizes with'' relation, but uses
1852 release/consume in place of release/acquire.
1853 </small>
1861 Two sets of characters and their associated collating sequences shall be defined: the set in
1862 which source files are written (the source character set), and the set interpreted in the
1863 execution environment (the execution character set). Each set is further divided into a
1864 basic character set, whose contents are given by this subclause, and a set of zero or more
1865 locale-specific members (which are not members of the basic character set) called
1866 extended characters. The combined set is also called the extended character set. The
1867 values of the members of the execution character set are implementation-defined.
1869 In a character constant or string literal, members of the execution character set shall be
1870 represented by corresponding members of the source character set or by escape
1871 sequences consisting of the backslash \ followed by one or more characters. A byte with
1872 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1873 is used to terminate a character string.
1875 Both the basic source and basic execution character sets shall have the following
1876 members: the 26 uppercase letters of the Latin alphabet
1877 <pre>
1878 A B C D E F G H I J K L M
1879 N O P Q R S T U V W X Y Z
1880 </pre>
1881 the 26 lowercase letters of the Latin alphabet
1882 <pre>
1883 a b c d e f g h i j k l m
1884 n o p q r s t u v w x y z
1885 </pre>
1886 the 10 decimal digits
1887 <pre>
1888 0 1 2 3 4 5 6 7 8 9
1889 </pre>
1890 the following 29 graphic characters
1891 <pre>
1892 ! " # % & ' ( ) * + , - . / :
1893 ; < = > ? [ \ ] ^ _ { | } ~
1894 </pre>
1895 the space character, and control characters representing horizontal tab, vertical tab, and
1896 form feed. The representation of each member of the source and execution basic
1897 character sets shall fit in a byte. In both the source and execution basic character sets, the
1898 value of each character after 0 in the above list of decimal digits shall be one greater than
1899 the value of the previous. In source files, there shall be some way of indicating the end of
1900 each line of text; this International Standard treats such an end-of-line indicator as if it
1901 were a single new-line character. In the basic execution character set, there shall be
1902 control characters representing alert, backspace, carriage return, and new line. If any
1903 other characters are encountered in a source file (except in an identifier, a character
1904 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1905 <!--page 41 -->
1906 converted to a token), the behavior is undefined.
1907 <p><!--para 4 -->
1908 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1909 Standard the term does not include other characters that are letters in other alphabets.
1910 <p><!--para 5 -->
1911 The universal character name construct provides a way to name other characters.
1912 <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>),
1913 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>).
1917 <p><!--para 1 -->
1918 Before any other processing takes place, each occurrence of one of the following
1919 sequences of three characters (called trigraph sequences<sup><a href="#note17"><b>17)</b></a></sup>) is replaced with the
1920 corresponding single character.
1921 <pre>
1922 ??= # ??) ] ??! |
1923 ??( [ ??' ^ ??> }
1924 ??/ \ ??< { ??- ~
1925 </pre>
1926 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1927 above is not changed.
1928 <p><!--para 2 -->
1929 EXAMPLE 1
1930 <pre>
1931 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
1932 </pre>
1933 becomes
1934 <pre>
1935 #define arraycheck(a, b) a[b] || b[a]
1936 </pre>
1938 <p><!--para 3 -->
1939 EXAMPLE 2 The following source line
1940 <pre>
1942 </pre>
1943 becomes (after replacement of the trigraph sequence ??/)
1944 <pre>
1946 </pre>
1949 <p><b>Footnotes</b>
1950 <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
1951 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1952 </small>
1956 <p><!--para 1 -->
1957 The source character set may contain multibyte characters, used to represent members of
1958 the extended character set. The execution character set may also contain multibyte
1959 characters, which need not have the same encoding as for the source character set. For
1960 both character sets, the following shall hold:
1961 <ul>
1962 <li> The basic character set shall be present and each character shall be encoded as a
1963 single byte.
1964 <li> The presence, meaning, and representation of any additional members is locale-
1965 specific.
1967 <!--page 42 -->
1968 <li> A multibyte character set may have a state-dependent encoding, wherein each
1969 sequence of multibyte characters begins in an initial shift state and enters other
1970 locale-specific shift states when specific multibyte characters are encountered in the
1971 sequence. While in the initial shift state, all single-byte characters retain their usual
1972 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1973 in the sequence is a function of the current shift state.
1974 <li> A byte with all bits zero shall be interpreted as a null character independent of shift
1975 state. Such a byte shall not occur as part of any other multibyte character.
1976 </ul>
1977 <p><!--para 2 -->
1978 For source files, the following shall hold:
1979 <ul>
1980 <li> An identifier, comment, string literal, character constant, or header name shall begin
1981 and end in the initial shift state.
1982 <li> An identifier, comment, string literal, character constant, or header name shall consist
1983 of a sequence of valid multibyte characters.
1984 </ul>
1988 <p><!--para 1 -->
1989 The active position is that location on a display device where the next character output by
1990 the fputc function would appear. The intent of writing a printing character (as defined
1991 by the isprint function) to a display device is to display a graphic representation of
1992 that character at the active position and then advance the active position to the next
1993 position on the current line. The direction of writing is locale-specific. If the active
1994 position is at the final position of a line (if there is one), the behavior of the display device
1995 is unspecified.
1996 <p><!--para 2 -->
1997 Alphabetic escape sequences representing nongraphic characters in the execution
1998 character set are intended to produce actions on display devices as follows:
1999 \a (alert) Produces an audible or visible alert without changing the active position.
2000 \b (backspace) Moves the active position to the previous position on the current line. If
2001 <pre>
2002 the active position is at the initial position of a line, the behavior of the display
2003 device is unspecified.
2004 </pre>
2005 \f ( form feed) Moves the active position to the initial position at the start of the next
2006 <pre>
2007 logical page.
2008 </pre>
2009 \n (new line) Moves the active position to the initial position of the next line.
2010 \r (carriage return) Moves the active position to the initial position of the current line.
2011 \t (horizontal tab) Moves the active position to the next horizontal tabulation position
2012 <pre>
2013 on the current line. If the active position is at or past the last defined horizontal
2014 tabulation position, the behavior of the display device is unspecified.
2015 </pre>
2016 \v (vertical tab) Moves the active position to the initial position of the next vertical
2017 <!--page 43 -->
2018 <pre>
2019 tabulation position. If the active position is at or past the last defined vertical
2020 tabulation position, the behavior of the display device is unspecified.
2021 </pre>
2022 <p><!--para 3 -->
2023 Each of these escape sequences shall produce a unique implementation-defined value
2024 which can be stored in a single char object. The external representations in a text file
2025 need not be identical to the internal representations, and are outside the scope of this
2026 International Standard.
2027 <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>).
2031 <p><!--para 1 -->
2032 Functions shall be implemented such that they may be interrupted at any time by a signal,
2033 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
2034 invocations' control flow (after the interruption), function return values, or objects with
2035 automatic storage duration. All such objects shall be maintained outside the function
2036 image (the instructions that compose the executable representation of a function) on a
2037 per-invocation basis.
2041 <p><!--para 1 -->
2042 Both the translation and execution environments constrain the implementation of
2043 language translators and libraries. The following summarizes the language-related
2044 environmental limits on a conforming implementation; the library-related limits are
2045 discussed in clause 7.
2049 <p><!--para 1 -->
2050 The implementation shall be able to translate and execute at least one program that
2051 contains at least one instance of every one of the following limits:<sup><a href="#note18"><b>18)</b></a></sup>
2052 <ul>
2053 <li> 127 nesting levels of blocks
2054 <li> 63 nesting levels of conditional inclusion
2055 <li> 12 pointer, array, and function declarators (in any combinations) modifying an
2056 arithmetic, structure, union, or void type in a declaration
2057 <li> 63 nesting levels of parenthesized declarators within a full declarator
2058 <li> 63 nesting levels of parenthesized expressions within a full expression
2059 <li> 63 significant initial characters in an internal identifier or a macro name (each
2060 universal character name or extended source character is considered a single
2061 character)
2062 <li> 31 significant initial characters in an external identifier (each universal character name
2063 specifying a short identifier of 0000FFFF or less is considered 6 characters, each
2066 <!--page 44 -->
2067 <pre>
2068 universal character name specifying a short identifier of 00010000 or more is
2069 considered 10 characters, and each extended source character is considered the same
2070 number of characters as the corresponding universal character name, if any)<sup><a href="#note19"><b>19)</b></a></sup>
2071 </pre>
2072 <li> 4095 external identifiers in one translation unit
2073 <li> 511 identifiers with block scope declared in one block
2074 <li> 4095 macro identifiers simultaneously defined in one preprocessing translation unit
2075 <li> 127 parameters in one function definition
2076 <li> 127 arguments in one function call
2077 <li> 127 parameters in one macro definition
2078 <li> 127 arguments in one macro invocation
2079 <li> 4095 characters in a logical source line
2080 <li> 4095 characters in a string literal (after concatenation)
2081 <li> 65535 bytes in an object (in a hosted environment only)
2082 <li> 15 nesting levels for #included files
2083 <li> 1023 case labels for a switch statement (excluding those for any nested switch
2084 statements)
2085 <li> 1023 members in a single structure or union
2086 <li> 1023 enumeration constants in a single enumeration
2087 <li> 63 levels of nested structure or union definitions in a single struct-declaration-list
2088 </ul>
2090 <p><b>Footnotes</b>
2091 <p><small><a name="note18" href="#note18">18)</a> Implementations should avoid imposing fixed translation limits whenever possible.
2092 </small>
2093 <p><small><a name="note19" href="#note19">19)</a> See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
2094 </small>
2098 <p><!--para 1 -->
2099 An implementation is required to document all the limits specified in this subclause,
2100 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
2102 <p><b> Forward references</b>: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>).
2105 <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>
2106 <p><!--para 1 -->
2107 The values given below shall be replaced by constant expressions suitable for use in #if
2108 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
2109 following shall be replaced by expressions that have the same type as would an
2110 expression that is an object of the corresponding type converted according to the integer
2111 promotions. Their implementation-defined values shall be equal or greater in magnitude
2114 <!--page 45 -->
2115 (absolute value) to those shown, with the same sign.
2116 <ul>
2117 <li> number of bits for smallest object that is not a bit-field (byte)
2118 CHAR_BIT 8
2119 <li> minimum value for an object of type signed char
2120 SCHAR_MIN -127 // -(27 - 1)
2121 <li> maximum value for an object of type signed char
2122 SCHAR_MAX +127 // 27 - 1
2123 <li> maximum value for an object of type unsigned char
2124 UCHAR_MAX 255 // 28 - 1
2125 <li> minimum value for an object of type char
2126 CHAR_MIN see below
2127 <li> maximum value for an object of type char
2128 CHAR_MAX see below
2129 <li> maximum number of bytes in a multibyte character, for any supported locale
2130 MB_LEN_MAX 1
2131 <li> minimum value for an object of type short int
2132 SHRT_MIN -32767 // -(215 - 1)
2133 <li> maximum value for an object of type short int
2134 SHRT_MAX +32767 // 215 - 1
2135 <li> maximum value for an object of type unsigned short int
2136 USHRT_MAX 65535 // 216 - 1
2137 <li> minimum value for an object of type int
2138 INT_MIN -32767 // -(215 - 1)
2139 <li> maximum value for an object of type int
2140 INT_MAX +32767 // 215 - 1
2141 <li> maximum value for an object of type unsigned int
2142 UINT_MAX 65535 // 216 - 1
2143 <li> minimum value for an object of type long int
2144 LONG_MIN -2147483647 // -(231 - 1)
2145 <li> maximum value for an object of type long int
2146 LONG_MAX +2147483647 // 231 - 1
2147 <li> maximum value for an object of type unsigned long int
2148 ULONG_MAX 4294967295 // 232 - 1
2149 <!--page 46 -->
2150 <li> minimum value for an object of type long long int
2151 LLONG_MIN -9223372036854775807 // -(263 - 1)
2152 <li> maximum value for an object of type long long int
2153 LLONG_MAX +9223372036854775807 // 263 - 1
2154 <li> maximum value for an object of type unsigned long long int
2155 ULLONG_MAX 18446744073709551615 // 264 - 1
2156 </ul>
2157 <p><!--para 2 -->
2158 If the value of an object of type char is treated as a signed integer when used in an
2159 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
2160 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
2161 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
2162 UCHAR_MAX.<sup><a href="#note20"><b>20)</b></a></sup> The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
2163 <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>).
2165 <p><b>Footnotes</b>
2167 </small>
2170 <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>
2171 <p><!--para 1 -->
2172 The characteristics of floating types are defined in terms of a model that describes a
2173 representation of floating-point numbers and values that provide information about an
2174 implementation's floating-point arithmetic.<sup><a href="#note21"><b>21)</b></a></sup> The following parameters are used to
2175 define the model for each floating-point type:
2176 <pre>
2177 s sign ((+-)1)
2178 b base or radix of exponent representation (an integer > 1)
2179 e exponent (an integer between a minimum emin and a maximum emax )
2180 p precision (the number of base-b digits in the significand)
2181 fk nonnegative integers less than b (the significand digits)
2182 </pre>
2183 <p><!--para 2 -->
2184 A floating-point number (x) is defined by the following model:
2185 <pre>
2186 p
2187 x = sb e (Sum) f k b-k ,
2188 k=1
2189 emin <= e <= emax
2190 </pre>
2192 <p><!--para 3 -->
2193 In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be
2194 able to contain other kinds of floating-point numbers, such as subnormal floating-point
2195 numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0,
2196 e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and
2197 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
2198 through almost every arithmetic operation without raising a floating-point exception; a
2199 signaling NaN generally raises a floating-point exception when occurring as an
2202 <!--page 47 -->
2204 <p><!--para 4 -->
2205 An implementation may give zero and values that are not floating-point numbers (such as
2206 infinities and NaNs) a sign or may leave them unsigned. Wherever such values are
2207 unsigned, any requirement in this International Standard to retrieve the sign shall produce
2208 an unspecified sign, and any requirement to set the sign shall be ignored.
2209 <p><!--para 5 -->
2210 The minimum range of representable values for a floating type is the most negative finite
2211 floating-point number representable in that type through the most positive finite floating-
2212 point number representable in that type. In addition, if negative infinity is representable
2213 in a type, the range of that type is extended to all negative real numbers; likewise, if
2214 positive infinity is representable in a type, the range of that type is extended to all positive
2215 real numbers.
2216 <p><!--para 6 -->
2217 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
2218 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
2219 defined, as is the accuracy of the conversion between floating-point internal
2220 representations and string representations performed by the library functions in
2221 <a href="#7.21"><stdio.h></a>, <a href="#7.22"><stdlib.h></a>, and <a href="#7.28"><wchar.h></a>. The implementation may state that the
2222 accuracy is unknown.
2223 <p><!--para 7 -->
2224 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
2225 expressions suitable for use in #if preprocessing directives; all floating values shall be
2226 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
2227 and FLT_ROUNDS have separate names for all three floating-point types. The floating-
2228 point model representation is provided for all values except FLT_EVAL_METHOD and
2229 FLT_ROUNDS.
2230 <p><!--para 8 -->
2231 The rounding mode for floating-point addition is characterized by the implementation-
2233 <pre>
2234 -1 indeterminable
2235 0 toward zero
2236 1 to nearest
2237 2 toward positive infinity
2238 3 toward negative infinity
2239 </pre>
2240 All other values for FLT_ROUNDS characterize implementation-defined rounding
2241 behavior.
2244 <!--page 48 -->
2245 <p><!--para 9 -->
2246 Except for assignment and cast (which remove all extra range and precision), the values
2247 yielded by operators with floating operands and values subject to the usual arithmetic
2248 conversions and of floating constants are evaluated to a format whose range and precision
2249 may be greater than required by the type. The use of evaluation formats is characterized
2250 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note24"><b>24)</b></a></sup>
2251 <pre>
2252 -1 indeterminable;
2253 0 evaluate all operations and constants just to the range and precision of the
2254 type;
2255 1 evaluate operations and constants of type float and double to the
2256 range and precision of the double type, evaluate long double
2257 operations and constants to the range and precision of the long double
2258 type;
2259 2 evaluate all operations and constants to the range and precision of the
2260 long double type.
2261 </pre>
2262 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
2263 behavior.
2264 <p><!--para 10 -->
2265 The presence or absence of subnormal numbers is characterized by the implementation-
2266 defined values of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and
2267 LDBL_HAS_SUBNORM:
2268 <pre>
2271 1 present (type does support subnormal numbers)
2272 </pre>
2273 <p><!--para 11 -->
2274 The values given in the following list shall be replaced by constant expressions with
2275 implementation-defined values that are greater or equal in magnitude (absolute value) to
2276 those shown, with the same sign:
2277 <ul>
2278 <li> radix of exponent representation, b
2279 FLT_RADIX 2
2284 <!--page 49 -->
2285 <li> number of base-FLT_RADIX digits in the floating-point significand, p
2286 FLT_MANT_DIG
2287 DBL_MANT_DIG
2288 LDBL_MANT_DIG
2289 <li> number of decimal digits, n, such that any floating-point number with p radix b digits
2290 can be rounded to a floating-point number with n decimal digits and back again
2291 without change to the value,
2292 <pre>
2293 { p log10 b if b is a power of 10
2294 {
2295 { [^1 + p log10 b^] otherwise
2296 </pre>
2297 FLT_DECIMAL_DIG 6
2298 DBL_DECIMAL_DIG 10
2299 LDBL_DECIMAL_DIG 10
2300 <li> number of decimal digits, n, such that any floating-point number in the widest
2301 supported floating type with pmax radix b digits can be rounded to a floating-point
2302 number with n decimal digits and back again without change to the value,
2303 <pre>
2304 { pmax log10 b if b is a power of 10
2305 {
2306 { [^1 + pmax log10 b^] otherwise
2307 </pre>
2308 DECIMAL_DIG 10
2309 <li> number of decimal digits, q, such that any floating-point number with q decimal digits
2310 can be rounded into a floating-point number with p radix b digits and back again
2311 without change to the q decimal digits,
2312 <pre>
2313 { p log10 b if b is a power of 10
2314 {
2315 { [_( p - 1) log10 b_] otherwise
2316 </pre>
2317 FLT_DIG 6
2318 DBL_DIG 10
2319 LDBL_DIG 10
2320 <li> minimum negative integer such that FLT_RADIX raised to one less than that power is
2321 a normalized floating-point number, emin
2322 FLT_MIN_EXP
2323 DBL_MIN_EXP
2324 LDBL_MIN_EXP
2325 <!--page 50 -->
2326 <li> minimum negative integer such that 10 raised to that power is in the range of
2327 normalized floating-point numbers, [^log10 b emin -1 ^]
2328 <pre>
2329 [ ]
2330 </pre>
2331 FLT_MIN_10_EXP -37
2332 DBL_MIN_10_EXP -37
2333 LDBL_MIN_10_EXP -37
2334 <li> maximum integer such that FLT_RADIX raised to one less than that power is a
2335 representable finite floating-point number, emax
2336 <pre>
2337 FLT_MAX_EXP
2338 DBL_MAX_EXP
2339 LDBL_MAX_EXP
2340 </pre>
2341 <li> maximum integer such that 10 raised to that power is in the range of representable
2342 finite floating-point numbers, [_log10 ((1 - b- p )b emax )_]
2343 <pre>
2344 FLT_MAX_10_EXP +37
2345 DBL_MAX_10_EXP +37
2346 LDBL_MAX_10_EXP +37
2347 </pre>
2348 </ul>
2349 <p><!--para 12 -->
2350 The values given in the following list shall be replaced by constant expressions with
2351 implementation-defined values that are greater than or equal to those shown:
2352 <ul>
2353 <li> maximum representable finite floating-point number, (1 - b- p )b emax
2354 <pre>
2355 FLT_MAX 1E+37
2356 DBL_MAX 1E+37
2357 LDBL_MAX 1E+37
2358 </pre>
2359 </ul>
2360 <p><!--para 13 -->
2361 The values given in the following list shall be replaced by constant expressions with
2362 implementation-defined (positive) values that are less than or equal to those shown:
2363 <ul>
2364 <li> the difference between 1 and the least value greater than 1 that is representable in the
2365 given floating point type, b1- p
2366 <pre>
2367 FLT_EPSILON 1E-5
2368 DBL_EPSILON 1E-9
2369 LDBL_EPSILON 1E-9
2370 </pre>
2371 <li> minimum normalized positive floating-point number, b emin -1
2372 <!--page 51 -->
2373 <pre>
2374 FLT_MIN 1E-37
2375 DBL_MIN 1E-37
2376 LDBL_MIN 1E-37
2377 </pre>
2379 FLT_TRUE_MIN 1E-37
2380 DBL_TRUE_MIN 1E-37
2381 LDBL_TRUE_MIN 1E-37
2382 </ul>
2383 <p><b>Recommended practice</b>
2384 <p><!--para 14 -->
2385 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
2386 should be the identity function.
2387 <p><!--para 15 -->
2388 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
2389 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
2390 float:
2391 <pre>
2392 6
2393 x = s16e (Sum) f k 16-k ,
2394 k=1
2395 -31 <= e <= +32
2396 </pre>
2398 <pre>
2399 FLT_RADIX 16
2400 FLT_MANT_DIG 6
2401 FLT_EPSILON 9.53674316E-07F
2402 FLT_DECIMAL_DIG 9
2403 FLT_DIG 6
2404 FLT_MIN_EXP -31
2405 FLT_MIN 2.93873588E-39F
2406 FLT_MIN_10_EXP -38
2407 FLT_MAX_EXP +32
2408 FLT_MAX 3.40282347E+38F
2409 FLT_MAX_10_EXP +38
2410 </pre>
2412 <p><!--para 16 -->
2413 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
2414 single-precision and double-precision numbers in IEC 60559,<sup><a href="#note28"><b>28)</b></a></sup> and the appropriate values in a
2416 <pre>
2417 24
2418 x f = s2e (Sum) f k 2-k ,
2419 k=1
2420 -125 <= e <= +128
2421 </pre>
2423 <pre>
2424 53
2425 x d = s2e (Sum) f k 2-k ,
2426 k=1
2427 -1021 <= e <= +1024
2428 </pre>
2430 <pre>
2431 FLT_RADIX 2
2432 DECIMAL_DIG 17
2433 FLT_MANT_DIG 24
2434 FLT_EPSILON 1.19209290E-07F // decimal constant
2435 FLT_EPSILON 0X1P-23F // hex constant
2436 FLT_DECIMAL_DIG 9
2437 </pre>
2440 <!--page 52 -->
2441 <pre>
2442 FLT_DIG 6
2443 FLT_MIN_EXP -125
2444 FLT_MIN 1.17549435E-38F // decimal constant
2445 FLT_MIN 0X1P-126F // hex constant
2446 FLT_TRUE_MIN 1.40129846E-45F // decimal constant
2447 FLT_TRUE_MIN 0X1P-149F // hex constant
2448 FLT_HAS_SUBNORM 1
2449 FLT_MIN_10_EXP -37
2450 FLT_MAX_EXP +128
2451 FLT_MAX 3.40282347E+38F // decimal constant
2452 FLT_MAX 0X1.fffffeP127F // hex constant
2453 FLT_MAX_10_EXP +38
2454 DBL_MANT_DIG 53
2455 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
2456 DBL_EPSILON 0X1P-52 // hex constant
2457 DBL_DECIMAL_DIG 17
2458 DBL_DIG 15
2459 DBL_MIN_EXP -1021
2460 DBL_MIN 2.2250738585072014E-308 // decimal constant
2461 DBL_MIN 0X1P-1022 // hex constant
2462 DBL_TRUE_MIN 4.9406564584124654E-324 // decimal constant
2463 DBL_TRUE_MIN 0X1P-1074 // hex constant
2464 DBL_HAS_SUBNORM 1
2465 DBL_MIN_10_EXP -307
2466 DBL_MAX_EXP +1024
2467 DBL_MAX 1.7976931348623157E+308 // decimal constant
2468 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
2469 DBL_MAX_10_EXP +308
2470 </pre>
2471 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
2472 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
2473 precision), then DECIMAL_DIG would be 21.
2475 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
2476 <a href="#7.3"><complex.h></a> (<a href="#7.3">7.3</a>), extended multibyte and wide character utilities <a href="#7.28"><wchar.h></a>
2477 (<a href="#7.28">7.28</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>
2478 (<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>).
2479 <!--page 53 -->
2481 <p><b>Footnotes</b>
2482 <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
2483 does not require the floating-point arithmetic of the implementation to be identical.
2484 </small>
2485 <p><small><a name="note22" href="#note22">22)</a> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
2486 IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
2487 similar behavior.
2488 </small>
2489 <p><small><a name="note23" href="#note23">23)</a> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
2491 </small>
2492 <p><small><a name="note24" href="#note24">24)</a> The evaluation method determines evaluation formats of expressions involving all floating types, not
2493 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
2494 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
2495 double.
2496 </small>
2497 <p><small><a name="note25" href="#note25">25)</a> Characterization as indeterminable is intended if floating-point operations do not consistently interpret
2498 subnormal representations as zero, nor as nonzero.
2499 </small>
2500 <p><small><a name="note26" href="#note26">26)</a> Characterization as absent is intended if no floating-point operations produce subnormal results from
2501 non-subnormal inputs, even if the type format includes representations of subnormal numbers.
2502 </small>
2503 <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
2504 positive number no greater than the minimum normalized positive number for the type.
2505 </small>
2506 <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
2507 limits are one less than shown here.
2508 </small>
2515 <p><!--para 1 -->
2516 In the syntax notation used in this clause, syntactic categories (nonterminals) are
2517 indicated by italic type, and literal words and character set members (terminals) by bold
2518 type. A colon (:) following a nonterminal introduces its definition. Alternative
2519 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
2520 optional symbol is indicated by the subscript ''opt'', so that
2521 <pre>
2522 { expression<sub>opt</sub> }
2523 </pre>
2524 indicates an optional expression enclosed in braces.
2525 <p><!--para 2 -->
2526 When syntactic categories are referred to in the main text, they are not italicized and
2527 words are separated by spaces instead of hyphens.
2528 <p><!--para 3 -->
2536 <p><!--para 1 -->
2537 An identifier can denote an object; a function; a tag or a member of a structure, union, or
2538 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
2539 same identifier can denote different entities at different points in the program. A member
2540 of an enumeration is called an enumeration constant. Macro names and macro
2541 parameters are not considered further here, because prior to the semantic phase of
2542 program translation any occurrences of macro names in the source file are replaced by the
2543 preprocessing token sequences that constitute their macro definitions.
2544 <p><!--para 2 -->
2545 For each different entity that an identifier designates, the identifier is visible (i.e., can be
2546 used) only within a region of program text called its scope. Different entities designated
2547 by the same identifier either have different scopes, or are in different name spaces. There
2548 are four kinds of scopes: function, file, block, and function prototype. (A function
2549 prototype is a declaration of a function that declares the types of its parameters.)
2550 <p><!--para 3 -->
2551 A label name is the only kind of identifier that has function scope. It can be used (in a
2552 goto statement) anywhere in the function in which it appears, and is declared implicitly
2553 by its syntactic appearance (followed by a : and a statement).
2554 <p><!--para 4 -->
2555 Every other identifier has scope determined by the placement of its declaration (in a
2556 declarator or type specifier). If the declarator or type specifier that declares the identifier
2557 appears outside of any block or list of parameters, the identifier has file scope, which
2558 terminates at the end of the translation unit. If the declarator or type specifier that
2559 declares the identifier appears inside a block or within the list of parameter declarations in
2560 a function definition, the identifier has block scope, which terminates at the end of the
2561 associated block. If the declarator or type specifier that declares the identifier appears
2562 <!--page 54 -->
2563 within the list of parameter declarations in a function prototype (not part of a function
2564 definition), the identifier has function prototype scope, which terminates at the end of the
2565 function declarator. If an identifier designates two different entities in the same name
2566 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will end
2567 strictly before the scope of the other entity (the outer scope). Within the inner scope, the
2568 identifier designates the entity declared in the inner scope; the entity declared in the outer
2569 scope is hidden (and not visible) within the inner scope.
2570 <p><!--para 5 -->
2571 Unless explicitly stated otherwise, where this International Standard uses the term
2572 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
2573 entity in the relevant name space whose declaration is visible at the point the identifier
2574 occurs.
2575 <p><!--para 6 -->
2576 Two identifiers have the same scope if and only if their scopes terminate at the same
2577 point.
2578 <p><!--para 7 -->
2579 Structure, union, and enumeration tags have scope that begins just after the appearance of
2580 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
2581 begins just after the appearance of its defining enumerator in an enumerator list. Any
2582 other identifier has scope that begins just after the completion of its declarator.
2583 <p><!--para 8 -->
2584 As a special case, a type name (which is not a declaration of an identifier) is considered to
2585 have a scope that begins just after the place within the type name where the omitted
2586 identifier would appear were it not omitted.
2587 <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
2588 (<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>),
2593 <p><!--para 1 -->
2594 An identifier declared in different scopes or in the same scope more than once can be
2595 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
2596 three kinds of linkage: external, internal, and none.
2597 <p><!--para 2 -->
2598 In the set of translation units and libraries that constitutes an entire program, each
2599 declaration of a particular identifier with external linkage denotes the same object or
2600 function. Within one translation unit, each declaration of an identifier with internal
2601 linkage denotes the same object or function. Each declaration of an identifier with no
2602 linkage denotes a unique entity.
2603 <p><!--para 3 -->
2604 If the declaration of a file scope identifier for an object or a function contains the storage-
2605 class specifier static, the identifier has internal linkage.<sup><a href="#note30"><b>30)</b></a></sup>
2609 <!--page 55 -->
2610 <p><!--para 4 -->
2611 For an identifier declared with the storage-class specifier extern in a scope in which a
2612 prior declaration of that identifier is visible,<sup><a href="#note31"><b>31)</b></a></sup> if the prior declaration specifies internal or
2613 external linkage, the linkage of the identifier at the later declaration is the same as the
2614 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
2615 declaration specifies no linkage, then the identifier has external linkage.
2616 <p><!--para 5 -->
2617 If the declaration of an identifier for a function has no storage-class specifier, its linkage
2618 is determined exactly as if it were declared with the storage-class specifier extern. If
2619 the declaration of an identifier for an object has file scope and no storage-class specifier,
2620 its linkage is external.
2621 <p><!--para 6 -->
2622 The following identifiers have no linkage: an identifier declared to be anything other than
2623 an object or a function; an identifier declared to be a function parameter; a block scope
2624 identifier for an object declared without the storage-class specifier extern.
2625 <p><!--para 7 -->
2626 If, within a translation unit, the same identifier appears with both internal and external
2627 linkage, the behavior is undefined.
2628 <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>),
2631 <p><b>Footnotes</b>
2632 <p><small><a name="note29" href="#note29">29)</a> There is no linkage between different identifiers.
2633 </small>
2634 <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
2636 </small>
2637 <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.
2638 </small>
2642 <p><!--para 1 -->
2643 If more than one declaration of a particular identifier is visible at any point in a
2644 translation unit, the syntactic context disambiguates uses that refer to different entities.
2645 Thus, there are separate name spaces for various categories of identifiers, as follows:
2646 <ul>
2647 <li> label names (disambiguated by the syntax of the label declaration and use);
2648 <li> the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note32"><b>32)</b></a></sup>
2649 of the keywords struct, union, or enum);
2650 <li> the members of structures or unions; each structure or union has a separate name
2651 space for its members (disambiguated by the type of the expression used to access the
2652 member via the . or -> operator);
2653 <li> all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
2654 enumeration constants).
2655 </ul>
2656 <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>),
2657 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
2660 <!--page 56 -->
2662 <p><b>Footnotes</b>
2663 <p><small><a name="note32" href="#note32">32)</a> There is only one name space for tags even though three are possible.
2664 </small>
2668 <p><!--para 1 -->
2669 An object has a storage duration that determines its lifetime. There are four storage
2670 durations: static, thread, automatic, and allocated. Allocated storage is described in
2672 <p><!--para 2 -->
2673 The lifetime of an object is the portion of program execution during which storage is
2674 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note33"><b>33)</b></a></sup> and retains
2675 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
2676 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
2677 the object it points to (or just past) reaches the end of its lifetime.
2678 <p><!--para 3 -->
2679 An object whose identifier is declared without the storage-class specifier
2680 _Thread_local, and either with external or internal linkage or with the storage-class
2681 specifier static, has static storage duration. Its lifetime is the entire execution of the
2682 program and its stored value is initialized only once, prior to program startup.
2683 <p><!--para 4 -->
2684 An object whose identifier is declared with the storage-class specifier _Thread_local
2685 has thread storage duration. Its lifetime is the entire execution of the thread for which it
2686 is created, and its stored value is initialized when the thread is started. There is a distinct
2687 object per thread, and use of the declared name in an expression refers to the object
2688 associated with the thread evaluating the expression. The result of attempting to
2689 indirectly access an object with thread storage duration from a thread other than the one
2690 with which the object is associated is implementation-defined.
2691 <p><!--para 5 -->
2692 An object whose identifier is declared with no linkage and without the storage-class
2693 specifier static has automatic storage duration, as do some compound literals. The
2694 result of attempting to indirectly access an object with automatic storage duration from a
2695 thread other than the one with which the object is associated is implementation-defined.
2696 <p><!--para 6 -->
2697 For such an object that does not have a variable length array type, its lifetime extends
2698 from entry into the block with which it is associated until execution of that block ends in
2699 any way. (Entering an enclosed block or calling a function suspends, but does not end,
2700 execution of the current block.) If the block is entered recursively, a new instance of the
2701 object is created each time. The initial value of the object is indeterminate. If an
2702 initialization is specified for the object, it is performed each time the declaration or
2703 compound literal is reached in the execution of the block; otherwise, the value becomes
2704 indeterminate each time the declaration is reached.
2708 <!--page 57 -->
2709 <p><!--para 7 -->
2710 For such an object that does have a variable length array type, its lifetime extends from
2711 the declaration of the object until execution of the program leaves the scope of the
2712 declaration.<sup><a href="#note35"><b>35)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2713 each time. The initial value of the object is indeterminate.
2714 <p><!--para 8 -->
2715 A non-lvalue expression with structure or union type, where the structure or union
2716 contains a member with array type (including, recursively, members of all contained
2717 structures and unions) refers to an object with automatic storage duration and temporary
2718 lifetime.<sup><a href="#note36"><b>36)</b></a></sup> Its lifetime begins when the expression is evaluated and its initial value is the
2719 value of the expression. Its lifetime ends when the evaluation of the containing full
2720 expression or full declarator ends. Any attempt to modify an object with temporary
2721 lifetime results in undefined behavior.
2722 <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
2723 (<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>).
2725 <p><b>Footnotes</b>
2726 <p><small><a name="note33" href="#note33">33)</a> The term ''constant address'' means that two pointers to the object constructed at possibly different
2727 times will compare equal. The address may be different during two different executions of the same
2728 program.
2729 </small>
2730 <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.
2731 </small>
2732 <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
2733 embedded block prior to the declaration, leaves the scope of the declaration.
2734 </small>
2735 <p><small><a name="note36" href="#note36">36)</a> The address of such an object is taken implicitly when an array member is accessed.
2736 </small>
2740 <p><!--para 1 -->
2741 The meaning of a value stored in an object or returned by a function is determined by the
2742 type of the expression used to access it. (An identifier declared to be an object is the
2743 simplest such expression; the type is specified in the declaration of the identifier.) Types
2744 are partitioned into object types (types that describe objects) and function types (types
2745 that describe functions). At various points within a translation unit an object type may be
2746 incomplete (lacking sufficient information to determine the size of objects of that type) or
2748 <p><!--para 2 -->
2749 An object declared as type _Bool is large enough to store the values 0 and 1.
2750 <p><!--para 3 -->
2751 An object declared as type char is large enough to store any member of the basic
2752 execution character set. If a member of the basic execution character set is stored in a
2753 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2754 a char object, the resulting value is implementation-defined but shall be within the range
2755 of values that can be represented in that type.
2756 <p><!--para 4 -->
2757 There are five standard signed integer types, designated as signed char, short
2758 int, int, long int, and long long int. (These and other types may be
2759 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2760 implementation-defined extended signed integer types.<sup><a href="#note38"><b>38)</b></a></sup> The standard and extended
2761 signed integer types are collectively called signed integer types.<sup><a href="#note39"><b>39)</b></a></sup>
2763 <!--page 58 -->
2764 <p><!--para 5 -->
2765 An object declared as type signed char occupies the same amount of storage as a
2766 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2767 architecture of the execution environment (large enough to contain any value in the range
2769 <p><!--para 6 -->
2770 For each of the signed integer types, there is a corresponding (but different) unsigned
2771 integer type (designated with the keyword unsigned) that uses the same amount of
2772 storage (including sign information) and has the same alignment requirements. The type
2773 _Bool and the unsigned integer types that correspond to the standard signed integer
2774 types are the standard unsigned integer types. The unsigned integer types that
2775 correspond to the extended signed integer types are the extended unsigned integer types.
2776 The standard and extended unsigned integer types are collectively called unsigned integer
2778 <p><!--para 7 -->
2779 The standard signed integer types and standard unsigned integer types are collectively
2780 called the standard integer types, the extended signed integer types and extended
2781 unsigned integer types are collectively called the extended integer types.
2782 <p><!--para 8 -->
2783 For any two integer types with the same signedness and different integer conversion rank
2784 (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
2785 subrange of the values of the other type.
2786 <p><!--para 9 -->
2787 The range of nonnegative values of a signed integer type is a subrange of the
2788 corresponding unsigned integer type, and the representation of the same value in each
2789 type is the same.<sup><a href="#note41"><b>41)</b></a></sup> A computation involving unsigned operands can never overflow,
2790 because a result that cannot be represented by the resulting unsigned integer type is
2791 reduced modulo the number that is one greater than the largest value that can be
2792 represented by the resulting type.
2793 <p><!--para 10 -->
2794 There are three real floating types, designated as float, double, and long
2795 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
2796 type double; the set of values of the type double is a subset of the set of values of the
2797 type long double.
2800 <!--page 59 -->
2801 <p><!--para 11 -->
2802 There are three complex types, designated as float _Complex, double
2803 _Complex, and long double _Complex.<sup><a href="#note43"><b>43)</b></a></sup> (Complex types are a conditional
2804 feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.) The real floating and
2805 complex types are collectively called the floating types.
2806 <p><!--para 12 -->
2807 For each floating type there is a corresponding real type, which is always a real floating
2808 type. For real floating types, it is the same type. For complex types, it is the type given
2809 by deleting the keyword _Complex from the type name.
2810 <p><!--para 13 -->
2811 Each complex type has the same representation and alignment requirements as an array
2812 type containing exactly two elements of the corresponding real type; the first element is
2813 equal to the real part, and the second element to the imaginary part, of the complex
2814 number.
2815 <p><!--para 14 -->
2816 The type char, the signed and unsigned integer types, and the floating types are
2817 collectively called the basic types. The basic types are complete object types. Even if the
2818 implementation defines two or more basic types to have the same representation, they are
2820 <p><!--para 15 -->
2821 The three types char, signed char, and unsigned char are collectively called
2822 the character types. The implementation shall define char to have the same range,
2823 representation, and behavior as either signed char or unsigned char.<sup><a href="#note45"><b>45)</b></a></sup>
2824 <p><!--para 16 -->
2825 An enumeration comprises a set of named integer constant values. Each distinct
2826 enumeration constitutes a different enumerated type.
2827 <p><!--para 17 -->
2828 The type char, the signed and unsigned integer types, and the enumerated types are
2829 collectively called integer types. The integer and real floating types are collectively called
2830 real types.
2831 <p><!--para 18 -->
2832 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2833 belongs to one type domain: the real type domain comprises the real types, the complex
2834 type domain comprises the complex types.
2835 <p><!--para 19 -->
2836 The void type comprises an empty set of values; it is an incomplete object type that
2837 cannot be completed.
2841 <!--page 60 -->
2842 <p><!--para 20 -->
2843 Any number of derived types can be constructed from the object and function types, as
2844 follows:
2845 <ul>
2846 <li> An array type describes a contiguously allocated nonempty set of objects with a
2847 particular member object type, called the element type. The element type shall be
2848 complete whenever the array type is specified. Array types are characterized by their
2849 element type and by the number of elements in the array. An array type is said to be
2850 derived from its element type, and if its element type is T , the array type is sometimes
2851 called ''array of T ''. The construction of an array type from an element type is called
2852 ''array type derivation''.
2853 <li> A structure type describes a sequentially allocated nonempty set of member objects
2854 (and, in certain circumstances, an incomplete array), each of which has an optionally
2855 specified name and possibly distinct type.
2856 <li> A union type describes an overlapping nonempty set of member objects, each of
2857 which has an optionally specified name and possibly distinct type.
2858 <li> A function type describes a function with specified return type. A function type is
2859 characterized by its return type and the number and types of its parameters. A
2860 function type is said to be derived from its return type, and if its return type is T , the
2861 function type is sometimes called ''function returning T ''. The construction of a
2862 function type from a return type is called ''function type derivation''.
2863 <li> A pointer type may be derived from a function type or an object type, called the
2864 referenced type. A pointer type describes an object whose value provides a reference
2865 to an entity of the referenced type. A pointer type derived from the referenced type T
2866 is sometimes called ''pointer to T ''. The construction of a pointer type from a
2867 referenced type is called ''pointer type derivation''. A pointer type is a complete
2868 object type.
2869 <li> An atomic type describes the type designated by the construct _Atomic ( type-
2870 name ). (Atomic types are a conditional feature that implementations need not
2872 </ul>
2873 These methods of constructing derived types can be applied recursively.
2874 <p><!--para 21 -->
2875 Arithmetic types and pointer types are collectively called scalar types. Array and
2876 structure types are collectively called aggregate types.<sup><a href="#note46"><b>46)</b></a></sup>
2877 <p><!--para 22 -->
2878 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2879 that type, by specifying the size in a later declaration (with internal or external linkage).
2880 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
2883 <!--page 61 -->
2884 type. It is completed, for all declarations of that type, by declaring the same structure or
2885 union tag with its defining content later in the same scope.
2886 <p><!--para 23 -->
2887 A type has known constant size if the type is not incomplete and is not a variable length
2888 array type.
2889 <p><!--para 24 -->
2890 Array, function, and pointer types are collectively called derived declarator types. A
2891 declarator type derivation from a type T is the construction of a derived declarator type
2892 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2893 T.
2894 <p><!--para 25 -->
2895 A type is characterized by its type category, which is either the outermost derivation of a
2896 derived type (as noted above in the construction of derived types), or the type itself if the
2897 type consists of no derived types.
2898 <p><!--para 26 -->
2899 Any type so far mentioned is an unqualified type. Each unqualified type has several
2900 qualified versions of its type,<sup><a href="#note47"><b>47)</b></a></sup> corresponding to the combinations of one, two, or all
2901 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2902 versions of a type are distinct types that belong to the same type category and have the
2903 same representation and alignment requirements.<sup><a href="#note48"><b>48)</b></a></sup> A derived type is not qualified by the
2904 qualifiers (if any) of the type from which it is derived.
2905 <p><!--para 27 -->
2906 Further, there is the _Atomic qualifier. The presence of the _Atomic qualifier
2907 designates an atomic type. The size, representation, and alignment of an atomic type
2908 need not be the same as those of the corresponding unqualified type. Therefore, this
2909 Standard explicitly uses the phrase ''atomic, qualified or unqualified type'' whenever the
2910 atomic version of a type is permitted along with the other qualified versions of a type.
2911 The phrase ''qualified or unqualified type'', without specific mention of atomic, does not
2912 include the atomic types.
2913 <p><!--para 28 -->
2914 A pointer to void shall have the same representation and alignment requirements as a
2915 pointer to a character type.<sup><a href="#note48"><b>48)</b></a></sup> Similarly, pointers to qualified or unqualified versions of
2916 compatible types shall have the same representation and alignment requirements. All
2917 pointers to structure types shall have the same representation and alignment requirements
2918 as each other. All pointers to union types shall have the same representation and
2919 alignment requirements as each other. Pointers to other types need not have the same
2920 representation or alignment requirements.
2921 <p><!--para 29 -->
2922 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2923 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2924 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2927 <!--page 62 -->
2928 qualified float'' and is a pointer to a qualified type.
2930 <p><!--para 30 -->
2931 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
2932 function returning struct tag''. The array has length five and the function has a single parameter of type
2933 float. Its type category is array.
2935 <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>).
2937 <p><b>Footnotes</b>
2938 <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
2939 different points within a translation unit.
2940 </small>
2941 <p><small><a name="note38" href="#note38">38)</a> Implementation-defined keywords shall have the form of an identifier reserved for any use as
2943 </small>
2944 <p><small><a name="note39" href="#note39">39)</a> Therefore, any statement in this Standard about signed integer types also applies to the extended
2945 signed integer types.
2946 </small>
2947 <p><small><a name="note40" href="#note40">40)</a> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2948 unsigned integer types.
2949 </small>
2950 <p><small><a name="note41" href="#note41">41)</a> The same representation and alignment requirements are meant to imply interchangeability as
2951 arguments to functions, return values from functions, and members of unions.
2952 </small>
2953 <p><small><a name="note42" href="#note42">42)</a> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2954 </small>
2955 <p><small><a name="note43" href="#note43">43)</a> A specification for imaginary types is in <a href="#G">annex G</a>.
2956 </small>
2957 <p><small><a name="note44" href="#note44">44)</a> An implementation may define new keywords that provide alternative ways to designate a basic (or
2958 any other) type; this does not violate the requirement that all basic types be different.
2959 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2961 </small>
2962 <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
2963 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2964 other two and is not compatible with either.
2965 </small>
2966 <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
2967 contain one member at a time.
2968 </small>
2969 <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.
2970 </small>
2971 <p><small><a name="note48" href="#note48">48)</a> The same representation and alignment requirements are meant to imply interchangeability as
2972 arguments to functions, return values from functions, and members of unions.
2973 </small>
2980 <p><!--para 1 -->
2981 The representations of all types are unspecified except as stated in this subclause.
2982 <p><!--para 2 -->
2983 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2984 the number, order, and encoding of which are either explicitly specified or
2985 implementation-defined.
2986 <p><!--para 3 -->
2987 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2989 <p><!--para 4 -->
2990 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2991 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2992 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
2993 called the object representation of the value. Values stored in bit-fields consist of m bits,
2994 where m is the size specified for the bit-field. The object representation is the set of m
2995 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
2996 than NaNs) with the same object representation compare equal, but values that compare
2997 equal may have different object representations.
2998 <p><!--para 5 -->
2999 Certain object representations need not represent a value of the object type. If the stored
3000 value of an object has such a representation and is read by an lvalue expression that does
3001 not have character type, the behavior is undefined. If such a representation is produced
3002 by a side effect that modifies all or any part of the object by an lvalue expression that
3003 does not have character type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup> Such a representation is called
3004 a trap representation.
3005 <p><!--para 6 -->
3006 When a value is stored in an object of structure or union type, including in a member
3007 object, the bytes of the object representation that correspond to any padding bytes take
3008 unspecified values.<sup><a href="#note51"><b>51)</b></a></sup> The value of a structure or union object is never a trap
3011 <!--page 63 -->
3012 representation, even though the value of a member of the structure or union object may be
3013 a trap representation.
3014 <p><!--para 7 -->
3015 When a value is stored in a member of an object of union type, the bytes of the object
3016 representation that do not correspond to that member but do correspond to other members
3017 take unspecified values.
3018 <p><!--para 8 -->
3019 Where an operator is applied to a value that has more than one object representation,
3020 which object representation is used shall not affect the value of the result.<sup><a href="#note52"><b>52)</b></a></sup> Where a
3021 value is stored in an object using a type that has more than one object representation for
3022 that value, it is unspecified which representation is used, but a trap representation shall
3023 not be generated.
3024 <p><!--para 9 -->
3025 Loads and stores of objects with atomic types are done with
3026 memory_order_seq_cst semantics.
3027 <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
3028 designators (<a href="#6.3.2.1">6.3.2.1</a>), order and consistency (<a href="#7.17.3">7.17.3</a>).
3030 <p><b>Footnotes</b>
3031 <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
3032 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
3033 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
3034 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
3035 type unsigned char range from 0 to 2
3037 <pre>
3038 CHAR_BIT
3039 - 1.
3040 </pre>
3041 </small>
3042 <p><small><a name="note50" href="#note50">50)</a> Thus, an automatic variable can be initialized to a trap representation without causing undefined
3043 behavior, but the value of the variable cannot be used until a proper value is stored in it.
3044 </small>
3045 <p><small><a name="note51" href="#note51">51)</a> Thus, for example, structure assignment need not copy any padding bits.
3046 </small>
3047 <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
3048 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
3049 defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
3050 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
3051 on values of type T may distinguish between them.
3052 </small>
3056 <p><!--para 1 -->
3057 For unsigned integer types other than unsigned char, the bits of the object
3058 representation shall be divided into two groups: value bits and padding bits (there need
3059 not be any of the latter). If there are N value bits, each bit shall represent a different
3060 power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of
3061 representing values from 0 to 2 N - 1 using a pure binary representation; this shall be
3062 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note53"><b>53)</b></a></sup>
3063 <p><!--para 2 -->
3064 For signed integer types, the bits of the object representation shall be divided into three
3065 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
3066 signed char shall not have any padding bits. There shall be exactly one sign bit.
3067 Each bit that is a value bit shall have the same value as the same bit in the object
3068 representation of the corresponding unsigned type (if there are M value bits in the signed
3069 type and N in the unsigned type, then M <= N ). If the sign bit is zero, it shall not affect
3071 <!--page 64 -->
3072 the resulting value. If the sign bit is one, the value shall be modified in one of the
3073 following ways:
3074 <ul>
3075 <li> the corresponding value with sign bit 0 is negated (sign and magnitude);
3076 <li> the sign bit has the value -(2 M ) (two's complement);
3077 <li> the sign bit has the value -(2 M - 1) (ones' complement).
3078 </ul>
3079 Which of these applies is implementation-defined, as is whether the value with sign bit 1
3080 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
3081 complement), is a trap representation or a normal value. In the case of sign and
3082 magnitude and ones' complement, if this representation is a normal value it is called a
3083 negative zero.
3084 <p><!--para 3 -->
3085 If the implementation supports negative zeros, they shall be generated only by:
3086 <ul>
3087 <li> the &, |, ^, ~, <<, and >> operators with operands that produce such a value;
3088 <li> the +, -, *, /, and % operators where one operand is a negative zero and the result is
3089 zero;
3090 <li> compound assignment operators based on the above cases.
3091 </ul>
3092 It is unspecified whether these cases actually generate a negative zero or a normal zero,
3093 and whether a negative zero becomes a normal zero when stored in an object.
3094 <p><!--para 4 -->
3095 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
3096 and >> operators with operands that would produce such a value is undefined.
3097 <p><!--para 5 -->
3098 The values of any padding bits are unspecified.<sup><a href="#note54"><b>54)</b></a></sup> A valid (non-trap) object representation
3099 of a signed integer type where the sign bit is zero is a valid object representation of the
3100 corresponding unsigned type, and shall represent the same value. For any integer type,
3101 the object representation where all the bits are zero shall be a representation of the value
3102 zero in that type.
3103 <p><!--para 6 -->
3104 The precision of an integer type is the number of bits it uses to represent values,
3105 excluding any sign and padding bits. The width of an integer type is the same but
3106 including any sign bit; thus for unsigned integer types the two values are the same, while
3107 for signed integer types the width is one greater than the precision.
3112 <!--page 65 -->
3114 <p><b>Footnotes</b>
3115 <p><small><a name="note53" href="#note53">53)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
3116 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
3117 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
3118 with unsigned types. All other combinations of padding bits are alternative object representations of
3119 the value specified by the value bits.
3120 </small>
3121 <p><small><a name="note54" href="#note54">54)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
3122 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
3123 representation other than as part of an exceptional condition such as an overflow. All other
3124 combinations of padding bits are alternative object representations of the value specified by the value
3125 bits.
3126 </small>
3130 <p><!--para 1 -->
3131 Two types have compatible type if their types are the same. Additional rules for
3132 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
3133 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,
3134 union, or enumerated types declared in separate translation units are compatible if their
3135 tags and members satisfy the following requirements: If one is declared with a tag, the
3136 other shall be declared with the same tag. If both are completed anywhere within their
3137 respective translation units, then the following additional requirements apply: there shall
3138 be a one-to-one correspondence between their members such that each pair of
3139 corresponding members are declared with compatible types; if one member of the pair is
3140 declared with an alignment specifier, the other is declared with an equivalent alignment
3141 specifier; and if one member of the pair is declared with a name, the other is declared
3142 with the same name. For two structures, corresponding members shall be declared in the
3143 same order. For two structures or unions, corresponding bit-fields shall have the same
3144 widths. For two enumerations, corresponding members shall have the same values.
3145 <p><!--para 2 -->
3146 All declarations that refer to the same object or function shall have compatible type;
3147 otherwise, the behavior is undefined.
3148 <p><!--para 3 -->
3149 A composite type can be constructed from two types that are compatible; it is a type that
3150 is compatible with both of the two types and satisfies the following conditions:
3151 <ul>
3152 <li> If both types are array types, the following rules are applied:
3153 <ul>
3154 <li> If one type is an array of known constant size, the composite type is an array of
3155 that size.
3156 <li> Otherwise, if one type is a variable length array whose size is specified by an
3157 expression that is not evaluated, the behavior is undefined.
3158 <li> Otherwise, if one type is a variable length array whose size is specified, the
3159 composite type is a variable length array of that size.
3160 <li> Otherwise, if one type is a variable length array of unspecified size, the composite
3161 type is a variable length array of unspecified size.
3162 <li> Otherwise, both types are arrays of unknown size and the composite type is an
3163 array of unknown size.
3164 </ul>
3165 The element type of the composite type is the composite type of the two element
3166 types.
3167 <li> If only one type is a function type with a parameter type list (a function prototype),
3168 the composite type is a function prototype with the parameter type list.
3171 <!--page 66 -->
3172 <li> If both types are function types with parameter type lists, the type of each parameter
3173 in the composite parameter type list is the composite type of the corresponding
3174 parameters.
3175 </ul>
3176 These rules apply recursively to the types from which the two types are derived.
3177 <p><!--para 4 -->
3178 For an identifier with internal or external linkage declared in a scope in which a prior
3179 declaration of that identifier is visible,<sup><a href="#note56"><b>56)</b></a></sup> if the prior declaration specifies internal or
3180 external linkage, the type of the identifier at the later declaration becomes the composite
3181 type.
3183 <p><!--para 5 -->
3184 EXAMPLE Given the following two file scope declarations:
3185 <pre>
3186 int f(int (*)(), double (*)[3]);
3187 int f(int (*)(char *), double (*)[]);
3188 </pre>
3189 The resulting composite type for the function is:
3190 <pre>
3191 int f(int (*)(char *), double (*)[3]);
3192 </pre>
3195 <p><b>Footnotes</b>
3196 <p><small><a name="note55" href="#note55">55)</a> Two types need not be identical to be compatible.
3197 </small>
3198 <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.
3199 </small>
3203 <p><!--para 1 -->
3204 Complete object types have alignment requirements which place restrictions on the
3205 addresses at which objects of that type may be allocated. An alignment is an
3206 implementation-defined integer value representing the number of bytes between
3207 successive addresses at which a given object can be allocated. An object type imposes an
3208 alignment requirement on every object of that type: stricter alignment can be requested
3209 using the _Alignas keyword.
3210 <p><!--para 2 -->
3211 A fundamental alignment is represented by an alignment less than or equal to the greatest
3212 alignment supported by the implementation in all contexts, which is equal to
3213 alignof(max_align_t).
3214 <p><!--para 3 -->
3215 An extended alignment is represented by an alignment greater than
3216 alignof(max_align_t). It is implementation-defined whether any extended
3217 alignments are supported and the contexts in which they are supported. A type having an
3218 extended alignment requirement is an over-aligned type.<sup><a href="#note57"><b>57)</b></a></sup>
3219 <p><!--para 4 -->
3220 Alignments are represented as values of the type size_t. Valid alignments include only
3221 those values returned by an alignof expression for fundamental types, plus an
3222 additional implementation-defined set of values, which may be empty. Every valid
3223 alignment value shall be a nonnegative integral power of two.
3226 <!--page 67 -->
3227 <p><!--para 5 -->
3228 Alignments have an order from weaker to stronger or stricter alignments. Stricter
3229 alignments have larger alignment values. An address that satisfies an alignment
3230 requirement also satisfies any weaker valid alignment requirement.
3231 <p><!--para 6 -->
3232 The alignment requirement of a complete type can be queried using an alignof
3233 expression. The types char, signed char, and unsigned char shall have the
3234 weakest alignment requirement.
3235 <p><!--para 7 -->
3236 Comparing alignments is meaningful and provides the obvious results:
3237 <ul>
3238 <li> Two alignments are equal when their numeric values are equal.
3239 <li> Two alignments are different when their numeric values are not equal.
3240 <li> When an alignment is larger than another it represents a stricter alignment.
3241 <!--page 68 -->
3242 </ul>
3244 <p><b>Footnotes</b>
3245 <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
3246 alignment has been applied.
3247 </small>
3251 <p><!--para 1 -->
3252 Several operators convert operand values from one type to another automatically. This
3253 subclause specifies the result required from such an implicit conversion, as well as those
3254 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
3255 the conversions performed by most ordinary operators; it is supplemented as required by
3257 <p><!--para 2 -->
3258 Conversion of an operand value to a compatible type causes no change to the value or the
3259 representation.
3267 <p><!--para 1 -->
3268 Every integer type has an integer conversion rank defined as follows:
3269 <ul>
3270 <li> No two signed integer types shall have the same rank, even if they have the same
3271 representation.
3272 <li> The rank of a signed integer type shall be greater than the rank of any signed integer
3273 type with less precision.
3274 <li> The rank of long long int shall be greater than the rank of long int, which
3275 shall be greater than the rank of int, which shall be greater than the rank of short
3276 int, which shall be greater than the rank of signed char.
3277 <li> The rank of any unsigned integer type shall equal the rank of the corresponding
3278 signed integer type, if any.
3279 <li> The rank of any standard integer type shall be greater than the rank of any extended
3280 integer type with the same width.
3281 <li> The rank of char shall equal the rank of signed char and unsigned char.
3282 <li> The rank of _Bool shall be less than the rank of all other standard integer types.
3283 <li> The rank of any enumerated type shall equal the rank of the compatible integer type
3285 <li> The rank of any extended signed integer type relative to another extended signed
3286 integer type with the same precision is implementation-defined, but still subject to the
3287 other rules for determining the integer conversion rank.
3288 <li> For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
3289 greater rank than T3, then T1 has greater rank than T3.
3290 </ul>
3291 <p><!--para 2 -->
3292 The following may be used in an expression wherever an int or unsigned int may
3293 be used:
3294 <!--page 69 -->
3295 <ul>
3296 <li> An object or expression with an integer type (other than int or unsigned int)
3297 whose integer conversion rank is less than or equal to the rank of int and
3298 unsigned int.
3299 <li> A bit-field of type _Bool, int, signed int, or unsigned int.
3300 </ul>
3301 If an int can represent all values of the original type (as restricted by the width, for a
3302 bit-field), the value is converted to an int; otherwise, it is converted to an unsigned
3303 int. These are called the integer promotions.<sup><a href="#note58"><b>58)</b></a></sup> All other types are unchanged by the
3304 integer promotions.
3305 <p><!--para 3 -->
3306 The integer promotions preserve value including sign. As discussed earlier, whether a
3307 ''plain'' char is treated as signed is implementation-defined.
3308 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
3311 <p><b>Footnotes</b>
3312 <p><small><a name="note58" href="#note58">58)</a> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
3313 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
3314 shift operators, as specified by their respective subclauses.
3315 </small>
3319 <p><!--para 1 -->
3320 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
3323 <p><b>Footnotes</b>
3324 <p><small><a name="note59" href="#note59">59)</a> NaNs do not compare equal to 0 and thus convert to 1.
3325 </small>
3329 <p><!--para 1 -->
3330 When a value with integer type is converted to another integer type other than _Bool, if
3331 the value can be represented by the new type, it is unchanged.
3332 <p><!--para 2 -->
3333 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
3334 subtracting one more than the maximum value that can be represented in the new type
3336 <p><!--para 3 -->
3337 Otherwise, the new type is signed and the value cannot be represented in it; either the
3338 result is implementation-defined or an implementation-defined signal is raised.
3340 <p><b>Footnotes</b>
3341 <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.
3342 </small>
3346 <p><!--para 1 -->
3347 When a finite value of real floating type is converted to an integer type other than _Bool,
3348 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
3349 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note61"><b>61)</b></a></sup>
3352 <!--page 70 -->
3353 <p><!--para 2 -->
3354 When a value of integer type is converted to a real floating type, if the value being
3355 converted can be represented exactly in the new type, it is unchanged. If the value being
3356 converted is in the range of values that can be represented but cannot be represented
3357 exactly, the result is either the nearest higher or nearest lower representable value, chosen
3358 in an implementation-defined manner. If the value being converted is outside the range of
3359 values that can be represented, the behavior is undefined. Results of some implicit
3360 conversions (<a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>) may be represented in greater precision and range than that
3361 required by the new type.
3363 <p><b>Footnotes</b>
3364 <p><small><a name="note61" href="#note61">61)</a> The remaindering operation performed when a value of integer type is converted to unsigned type
3365 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
3366 range of portable real floating values is (-1, Utype_MAX+1).
3367 </small>
3371 <p><!--para 1 -->
3372 When a value of real floating type is converted to a real floating type, if the value being
3373 converted can be represented exactly in the new type, it is unchanged. If the value being
3374 converted is in the range of values that can be represented but cannot be represented
3375 exactly, the result is either the nearest higher or nearest lower representable value, chosen
3376 in an implementation-defined manner. If the value being converted is outside the range of
3377 values that can be represented, the behavior is undefined. Results of some implicit
3378 conversions (<a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>) may be represented in greater precision and range than that
3379 required by the new type.
3383 <p><!--para 1 -->
3384 When a value of complex type is converted to another complex type, both the real and
3385 imaginary parts follow the conversion rules for the corresponding real types.
3389 <p><!--para 1 -->
3390 When a value of real type is converted to a complex type, the real part of the complex
3391 result value is determined by the rules of conversion to the corresponding real type and
3392 the imaginary part of the complex result value is a positive zero or an unsigned zero.
3393 <p><!--para 2 -->
3394 When a value of complex type is converted to a real type, the imaginary part of the
3395 complex value is discarded and the value of the real part is converted according to the
3396 conversion rules for the corresponding real type.
3400 <p><!--para 1 -->
3401 Many operators that expect operands of arithmetic type cause conversions and yield result
3402 types in a similar way. The purpose is to determine a common real type for the operands
3403 and result. For the specified operands, each operand is converted, without change of type
3404 domain, to a type whose corresponding real type is the common real type. Unless
3405 explicitly stated otherwise, the common real type is also the corresponding real type of
3406 the result, whose type domain is the type domain of the operands if they are the same,
3407 and complex otherwise. This pattern is called the usual arithmetic conversions:
3408 <!--page 71 -->
3409 <pre>
3410 First, if the corresponding real type of either operand is long double, the other
3411 operand is converted, without change of type domain, to a type whose
3412 corresponding real type is long double.
3413 Otherwise, if the corresponding real type of either operand is double, the other
3414 operand is converted, without change of type domain, to a type whose
3415 corresponding real type is double.
3416 Otherwise, if the corresponding real type of either operand is float, the other
3417 operand is converted, without change of type domain, to a type whose
3419 Otherwise, the integer promotions are performed on both operands. Then the
3420 following rules are applied to the promoted operands:
3421 If both operands have the same type, then no further conversion is needed.
3422 Otherwise, if both operands have signed integer types or both have unsigned
3423 integer types, the operand with the type of lesser integer conversion rank is
3424 converted to the type of the operand with greater rank.
3425 Otherwise, if the operand that has unsigned integer type has rank greater or
3426 equal to the rank of the type of the other operand, then the operand with
3427 signed integer type is converted to the type of the operand with unsigned
3428 integer type.
3429 Otherwise, if the type of the operand with signed integer type can represent
3430 all of the values of the type of the operand with unsigned integer type, then
3431 the operand with unsigned integer type is converted to the type of the
3432 operand with signed integer type.
3433 Otherwise, both operands are converted to the unsigned integer type
3434 corresponding to the type of the operand with signed integer type.
3435 </pre>
3436 <p><!--para 2 -->
3437 The values of floating operands and of the results of floating expressions may be
3438 represented in greater precision and range than that required by the type; the types are not
3444 <!--page 72 -->
3446 <p><b>Footnotes</b>
3447 <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
3448 float operand to double (and yields a double _Complex result).
3449 </small>
3450 <p><small><a name="note63" href="#note63">63)</a> The cast and assignment operators are still required to remove extra range and precision.
3451 </small>
3457 <h5><a name="6.3.2.1" href="#6.3.2.1">6.3.2.1 Lvalues, arrays, and function designators</a></h5>
3458 <p><!--para 1 -->
3459 An lvalue is an expression (with an object type other than void) that potentially
3460 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
3461 behavior is undefined. When an object is said to have a particular type, the type is
3462 specified by the lvalue used to designate the object. A modifiable lvalue is an lvalue that
3463 does not have array type, does not have an incomplete type, does not have a const-
3464 qualified type, and if it is a structure or union, does not have any member (including,
3465 recursively, any member or element of all contained aggregates or unions) with a const-
3466 qualified type.
3467 <p><!--para 2 -->
3468 Except when it is the operand of the sizeof operator, the unary & operator, the ++
3469 operator, the -- operator, or the left operand of the . operator or an assignment operator,
3470 an lvalue that does not have array type is converted to the value stored in the designated
3471 object (and is no longer an lvalue); this is called lvalue conversion. If the lvalue has
3472 qualified type, the value has the unqualified version of the type of the lvalue; additionally,
3473 if the lvalue has atomic type, the value has the non-atomic version of the type of the
3474 lvalue; otherwise, the value has the type of the lvalue. If the lvalue has an incomplete
3475 type and does not have array type, the behavior is undefined. If the lvalue designates an
3476 object of automatic storage duration that could have been declared with the register
3477 storage class (never had its address taken), and that object is uninitialized (not declared
3478 with an initializer and no assignment to it has been performed prior to use), the behavior
3479 is undefined.
3480 <p><!--para 3 -->
3481 Except when it is the operand of the sizeof operator or the unary & operator, or is a
3482 string literal used to initialize an array, an expression that has type ''array of type'' is
3483 converted to an expression with type ''pointer to type'' that points to the initial element of
3484 the array object and is not an lvalue. If the array object has register storage class, the
3485 behavior is undefined.
3486 <p><!--para 4 -->
3487 A function designator is an expression that has function type. Except when it is the
3488 operand of the sizeof operator<sup><a href="#note65"><b>65)</b></a></sup> or the unary & operator, a function designator with
3489 type ''function returning type'' is converted to an expression that has type ''pointer to
3492 <!--page 73 -->
3493 function returning type''.
3494 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
3495 (<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
3496 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
3497 (<a href="#6.5.3.1">6.5.3.1</a>), the sizeof operator (<a href="#6.5.3.4">6.5.3.4</a>), structure and union members (<a href="#6.5.2.3">6.5.2.3</a>).
3499 <p><b>Footnotes</b>
3500 <p><small><a name="note64" href="#note64">64)</a> The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
3501 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
3502 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
3503 as the ''value of an expression''.
3504 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
3505 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
3506 </small>
3507 <p><small><a name="note65" href="#note65">65)</a> Because this conversion does not occur, the operand of the sizeof operator remains a function
3509 </small>
3513 <p><!--para 1 -->
3514 The (nonexistent) value of a void expression (an expression that has type void) shall not
3515 be used in any way, and implicit or explicit conversions (except to void) shall not be
3516 applied to such an expression. If an expression of any other type is evaluated as a void
3517 expression, its value or designator is discarded. (A void expression is evaluated for its
3518 side effects.)
3522 <p><!--para 1 -->
3523 A pointer to void may be converted to or from a pointer to any object type. A pointer to
3524 any object type may be converted to a pointer to void and back again; the result shall
3525 compare equal to the original pointer.
3526 <p><!--para 2 -->
3527 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
3528 the q-qualified version of the type; the values stored in the original and converted pointers
3529 shall compare equal.
3530 <p><!--para 3 -->
3531 An integer constant expression with the value 0, or such an expression cast to type
3532 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
3533 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
3534 to a pointer to any object or function.
3535 <p><!--para 4 -->
3536 Conversion of a null pointer to another pointer type yields a null pointer of that type.
3537 Any two null pointers shall compare equal.
3538 <p><!--para 5 -->
3539 An integer may be converted to any pointer type. Except as previously specified, the
3540 result is implementation-defined, might not be correctly aligned, might not point to an
3541 entity of the referenced type, and might be a trap representation.<sup><a href="#note67"><b>67)</b></a></sup>
3542 <p><!--para 6 -->
3543 Any pointer type may be converted to an integer type. Except as previously specified, the
3544 result is implementation-defined. If the result cannot be represented in the integer type,
3545 the behavior is undefined. The result need not be in the range of values of any integer
3546 type.
3551 <!--page 74 -->
3552 <p><!--para 7 -->
3553 A pointer to an object type may be converted to a pointer to a different object type. If the
3554 resulting pointer is not correctly aligned<sup><a href="#note68"><b>68)</b></a></sup> for the referenced type, the behavior is
3555 undefined. Otherwise, when converted back again, the result shall compare equal to the
3556 original pointer. When a pointer to an object is converted to a pointer to a character type,
3557 the result points to the lowest addressed byte of the object. Successive increments of the
3558 result, up to the size of the object, yield pointers to the remaining bytes of the object.
3559 <p><!--para 8 -->
3560 A pointer to a function of one type may be converted to a pointer to a function of another
3561 type and back again; the result shall compare equal to the original pointer. If a converted
3562 pointer is used to call a function whose type is not compatible with the referenced type,
3563 the behavior is undefined.
3564 <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
3565 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>).
3570 <!--page 75 -->
3572 <p><b>Footnotes</b>
3573 <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>.
3574 </small>
3575 <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
3576 be consistent with the addressing structure of the execution environment.
3577 </small>
3578 <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
3579 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
3580 correctly aligned for a pointer to type C.
3581 </small>
3585 <p><b>Syntax</b>
3586 <p><!--para 1 -->
3587 <pre>
3588 token:
3589 keyword
3590 identifier
3591 constant
3592 string-literal
3593 punctuator
3594 preprocessing-token:
3595 header-name
3596 identifier
3597 pp-number
3598 character-constant
3599 string-literal
3600 punctuator
3601 each non-white-space character that cannot be one of the above
3602 </pre>
3603 <p><b>Constraints</b>
3604 <p><!--para 2 -->
3605 Each preprocessing token that is converted to a token shall have the lexical form of a
3606 keyword, an identifier, a constant, a string literal, or a punctuator.
3607 <p><b>Semantics</b>
3608 <p><!--para 3 -->
3609 A token is the minimal lexical element of the language in translation phases 7 and 8. The
3610 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
3611 A preprocessing token is the minimal lexical element of the language in translation
3612 phases 3 through 6. The categories of preprocessing tokens are: header names,
3613 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
3614 single non-white-space characters that do not lexically match the other preprocessing
3615 token categories.<sup><a href="#note69"><b>69)</b></a></sup> If a ' or a " character matches the last category, the behavior is
3616 undefined. Preprocessing tokens can be separated by white space; this consists of
3617 comments (described later), or white-space characters (space, horizontal tab, new-line,
3618 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
3619 during translation phase 4, white space (or the absence thereof) serves as more than
3620 preprocessing token separation. White space may appear within a preprocessing token
3621 only as part of a header name or between the quotation characters in a character constant
3622 or string literal.
3626 <!--page 76 -->
3628 If the input stream has been parsed into preprocessing tokens up to a given character, the
3629 next preprocessing token is the longest sequence of characters that could constitute a
3630 preprocessing token. There is one exception to this rule: header name preprocessing
3631 tokens are recognized only within #include preprocessing directives and in
3632 implementation-defined locations within #pragma directives. In such contexts, a
3633 sequence of characters that could be either a header name or a string literal is recognized
3634 as the former.
3636 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
3637 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
3638 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
3639 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
3640 not E is a macro name.
3643 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
3644 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
3646 <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>),
3647 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
3648 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
3649 (<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
3653 <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
3654 occur in source files.
3655 </small>
3661 <pre>
3662 keyword: one of
3663 alignof goto union
3664 auto if unsigned
3665 break inline void
3666 case int volatile
3667 char long while
3668 const register _Alignas
3669 continue restrict _Atomic
3670 default return _Bool
3671 do short _Complex
3672 double signed _Generic
3673 else sizeof _Imaginary
3674 enum static _Noreturn
3675 extern struct _Static_assert
3676 float switch _Thread_local
3677 for typedef
3678 </pre>
3682 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
3683 <!--page 77 -->
3687 <p><small><a name="note70" href="#note70">70)</a> One possible specification for imaginary types appears in <a href="#G">annex G</a>.
3688 </small>
3697 <pre>
3698 identifier:
3699 identifier-nondigit
3700 identifier identifier-nondigit
3701 identifier digit
3702 identifier-nondigit:
3703 nondigit
3704 universal-character-name
3705 other implementation-defined characters
3706 nondigit: one of
3707 _ a b c d e f g h i j k l m
3708 n o p q r s t u v w x y z
3709 A B C D E F G H I J K L M
3710 N O P Q R S T U V W X Y Z
3711 digit: one of
3712 0 1 2 3 4 5 6 7 8 9
3713 </pre>
3716 An identifier is a sequence of nondigit characters (including the underscore _, the
3717 lowercase and uppercase Latin letters, and other characters) and digits, which designates
3718 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
3719 There is no specific limit on the maximum length of an identifier.
3721 Each universal character name in an identifier shall designate a character whose encoding
3722 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
3723 shall not be a universal character name designating a character whose encoding falls into
3724 one of the ranges specified in <a href="#D.2">D.2</a>. An implementation may allow multibyte characters
3725 that are not part of the basic source character set to appear in identifiers; which characters
3726 and their correspondence to universal character names is implementation-defined.
3730 <!--page 78 -->
3732 When preprocessing tokens are converted to tokens during translation phase 7, if a
3733 preprocessing token could be converted to either a keyword or an identifier, it is converted
3734 to a keyword.
3737 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
3738 characters in an identifier; the limit for an external name (an identifier that has external
3739 linkage) may be more restrictive than that for an internal name (a macro name or an
3740 identifier that does not have external linkage). The number of significant characters in an
3741 identifier is implementation-defined.
3743 Any identifiers that differ in a significant character are different identifiers. If two
3744 identifiers differ only in nonsignificant characters, the behavior is undefined.
3745 <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>).
3748 <p><small><a name="note71" href="#note71">71)</a> On systems in which linkers cannot accept extended characters, an encoding of the universal character
3749 name may be used in forming valid external identifiers. For example, some otherwise unused
3750 character or sequence of characters may be used to encode the \u in a universal character name.
3751 Extended characters may produce a long external identifier.
3752 </small>
3758 The identifier __func__ shall be implicitly declared by the translator as if,
3759 immediately following the opening brace of each function definition, the declaration
3760 <pre>
3761 static const char __func__[] = "function-name";
3762 </pre>
3763 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note72"><b>72)</b></a></sup>
3765 This name is encoded as if the implicit declaration had been written in the source
3766 character set and then translated into the execution character set as indicated in translation
3767 phase 5.
3769 EXAMPLE Consider the code fragment:
3770 <pre>
3772 void myfunc(void)
3773 {
3774 printf("%s\n", __func__);
3775 /* ... */
3776 }
3777 </pre>
3778 Each time the function is called, it will print to the standard output stream:
3779 <pre>
3780 myfunc
3781 </pre>
3788 <!--page 79 -->
3791 <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
3792 identifier is explicitly declared using the name __func__, the behavior is undefined.
3793 </small>
3799 <pre>
3800 universal-character-name:
3801 \u hex-quad
3802 \U hex-quad hex-quad
3803 hex-quad:
3804 hexadecimal-digit hexadecimal-digit
3805 hexadecimal-digit hexadecimal-digit
3806 </pre>
3809 A universal character name shall not specify a character whose short identifier is less than
3814 Universal character names may be used in identifiers, character constants, and string
3815 literals to designate characters that are not in the basic character set.
3818 The universal character name \Unnnnnnnn designates the character whose eight-digit
3819 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note74"><b>74)</b></a></sup> Similarly, the universal
3820 character name \unnnn designates the character whose four-digit short identifier is nnnn
3821 (and whose eight-digit short identifier is 0000nnnn).
3826 <!--page 80 -->
3829 <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
3830 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
3831 UTF-16).
3833 </small>
3834 <p><small><a name="note74" href="#note74">74)</a> Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
3835 </small>
3841 <pre>
3842 constant:
3843 integer-constant
3844 floating-constant
3845 enumeration-constant
3846 character-constant
3847 </pre>
3850 Each constant shall have a type and the value of a constant shall be in the range of
3851 representable values for its type.
3854 Each constant has a type, determined by its form and value, as detailed later.
3860 <!--page 81 -->
3861 <pre>
3862 integer-constant:
3866 decimal-constant:
3867 nonzero-digit
3868 decimal-constant digit
3869 octal-constant:
3870 0
3871 octal-constant octal-digit
3872 hexadecimal-constant:
3873 hexadecimal-prefix hexadecimal-digit
3874 hexadecimal-constant hexadecimal-digit
3875 hexadecimal-prefix: one of
3877 nonzero-digit: one of
3878 1 2 3 4 5 6 7 8 9
3879 octal-digit: one of
3880 0 1 2 3 4 5 6 7
3881 hexadecimal-digit: one of
3882 0 1 2 3 4 5 6 7 8 9
3883 a b c d e f
3884 A B C D E F
3885 integer-suffix:
3887 unsigned-suffix long-long-suffix
3890 unsigned-suffix: one of
3891 u U
3892 long-suffix: one of
3893 l L
3894 long-long-suffix: one of
3895 ll LL
3896 </pre>
3899 An integer constant begins with a digit, but has no period or exponent part. It may have a
3900 prefix that specifies its base and a suffix that specifies its type.
3902 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3903 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3905 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3910 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3912 The type of an integer constant is the first of the corresponding list in which its value can
3913 be represented.
3914 <!--page 82 -->
3915 <pre>
3916 Octal or Hexadecimal
3917 </pre>
3918 Suffix Decimal Constant Constant
3920 none int int
3921 <pre>
3922 long int unsigned int
3923 long long int long int
3924 unsigned long int
3925 long long int
3926 unsigned long long int
3927 </pre>
3929 u or U unsigned int unsigned int
3930 <pre>
3931 unsigned long int unsigned long int
3932 unsigned long long int unsigned long long int
3933 </pre>
3935 l or L long int long int
3936 <pre>
3937 long long int unsigned long int
3938 long long int
3939 unsigned long long int
3940 </pre>
3942 Both u or U unsigned long int unsigned long int
3943 and l or L unsigned long long int unsigned long long int
3945 ll or LL long long int long long int
3946 <pre>
3947 unsigned long long int
3948 </pre>
3950 Both u or U unsigned long long int unsigned long long int
3951 and ll or LL
3953 If an integer constant cannot be represented by any type in its list, it may have an
3954 extended integer type, if the extended integer type can represent its value. If all of the
3955 types in the list for the constant are signed, the extended integer type shall be signed. If
3956 all of the types in the list for the constant are unsigned, the extended integer type shall be
3957 unsigned. If the list contains both signed and unsigned types, the extended integer type
3958 may be signed or unsigned. If an integer constant cannot be represented by any type in
3959 its list and has no extended integer type, then the integer constant has no type.
3960 <!--page 83 -->
3966 <!--page 84 -->
3967 <pre>
3968 floating-constant:
3969 decimal-floating-constant
3970 hexadecimal-floating-constant
3971 decimal-floating-constant:
3974 hexadecimal-floating-constant:
3975 hexadecimal-prefix hexadecimal-fractional-constant
3977 hexadecimal-prefix hexadecimal-digit-sequence
3979 fractional-constant:
3981 digit-sequence .
3982 exponent-part:
3985 sign: one of
3986 + -
3987 digit-sequence:
3988 digit
3989 digit-sequence digit
3990 hexadecimal-fractional-constant:
3992 hexadecimal-digit-sequence
3993 hexadecimal-digit-sequence .
3994 binary-exponent-part:
3997 hexadecimal-digit-sequence:
3998 hexadecimal-digit
3999 hexadecimal-digit-sequence hexadecimal-digit
4000 floating-suffix: one of
4001 f l F L
4002 </pre>
4005 A floating constant has a significand part that may be followed by an exponent part and a
4006 suffix that specifies its type. The components of the significand part may include a digit
4007 sequence representing the whole-number part, followed by a period (.), followed by a
4008 digit sequence representing the fraction part. The components of the exponent part are an
4009 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
4010 Either the whole-number part or the fraction part has to be present; for decimal floating
4011 constants, either the period or the exponent part has to be present.
4014 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
4015 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
4016 floating constants, the exponent indicates the power of 10 by which the significand part is
4017 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
4018 by which the significand part is to be scaled. For decimal floating constants, and also for
4019 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
4020 the nearest representable value, or the larger or smaller representable value immediately
4021 adjacent to the nearest representable value, chosen in an implementation-defined manner.
4022 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
4023 correctly rounded.
4025 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
4026 type float. If suffixed by the letter l or L, it has type long double.
4028 Floating constants are converted to internal format as if at translation-time. The
4029 conversion of a floating constant shall not raise an exceptional condition or a floating-
4030 point exception at execution time. All floating constants of the same source form<sup><a href="#note75"><b>75)</b></a></sup> shall
4031 convert to the same internal format with the same value.
4034 The implementation should produce a diagnostic message if a hexadecimal constant
4035 cannot be represented exactly in its evaluation format; the implementation should then
4036 proceed with the translation of the program.
4038 The translation-time conversion of floating constants should match the execution-time
4039 conversion of character strings by library functions, such as strtod, given matching
4040 inputs suitable for both conversions, the same result format, and default execution-time
4043 <!--page 85 -->
4046 <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
4047 convert to the same internal format and value.
4048 </small>
4049 <p><small><a name="note76" href="#note76">76)</a> The specification for the library functions recommends more accurate conversion than required for
4051 </small>
4057 <pre>
4058 enumeration-constant:
4059 identifier
4060 </pre>
4063 An identifier declared as an enumeration constant has type int.
4070 <!--page 86 -->
4071 <pre>
4072 character-constant:
4073 ' c-char-sequence '
4074 L' c-char-sequence '
4075 u' c-char-sequence '
4076 U' c-char-sequence '
4077 c-char-sequence:
4078 c-char
4079 c-char-sequence c-char
4080 c-char:
4081 any member of the source character set except
4082 the single-quote ', backslash \, or new-line character
4083 escape-sequence
4084 escape-sequence:
4085 simple-escape-sequence
4086 octal-escape-sequence
4087 hexadecimal-escape-sequence
4088 universal-character-name
4089 simple-escape-sequence: one of
4090 \' \" \? \\
4091 \a \b \f \n \r \t \v
4092 octal-escape-sequence:
4093 \ octal-digit
4094 \ octal-digit octal-digit
4095 \ octal-digit octal-digit octal-digit
4096 hexadecimal-escape-sequence:
4097 \x hexadecimal-digit
4098 hexadecimal-escape-sequence hexadecimal-digit
4099 </pre>
4100 <p><b>Description</b>
4101 <p><!--para 2 -->
4102 An integer character constant is a sequence of one or more multibyte characters enclosed
4103 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
4104 letter L, u, or U. With a few exceptions detailed later, the elements of the sequence are
4105 any members of the source character set; they are mapped in an implementation-defined
4106 manner to members of the execution character set.
4107 <p><!--para 3 -->
4108 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
4109 arbitrary integer values are representable according to the following table of escape
4110 sequences:
4111 <pre>
4112 single quote ' \'
4113 double quote " \"
4114 question mark ? \?
4115 backslash \ \\
4116 octal character \octal digits
4117 hexadecimal character \x hexadecimal digits
4118 </pre>
4120 The double-quote " and question-mark ? are representable either by themselves or by the
4121 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
4122 shall be represented, respectively, by the escape sequences \' and \\.
4124 The octal digits that follow the backslash in an octal escape sequence are taken to be part
4125 of the construction of a single character for an integer character constant or of a single
4126 wide character for a wide character constant. The numerical value of the octal integer so
4127 formed specifies the value of the desired character or wide character.
4129 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
4130 sequence are taken to be part of the construction of a single character for an integer
4131 character constant or of a single wide character for a wide character constant. The
4132 numerical value of the hexadecimal integer so formed specifies the value of the desired
4133 character or wide character.
4135 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
4136 constitute the escape sequence.
4138 In addition, characters not in the basic character set are representable by universal
4139 character names and certain nongraphic characters are representable by escape sequences
4140 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
4142 <!--page 87 -->
4145 The value of an octal or hexadecimal escape sequence shall be in the range of
4146 representable values for the corresponding type:
4147 <pre>
4148 Prefix Corresponding Type
4149 none unsigned char
4150 L the unsigned type corresponding to wchar_t
4151 u char16_t
4152 U char32_t
4153 </pre>
4156 An integer character constant has type int. The value of an integer character constant
4157 containing a single character that maps to a single-byte execution character is the
4158 numerical value of the representation of the mapped character interpreted as an integer.
4159 The value of an integer character constant containing more than one character (e.g.,
4160 'ab'), or containing a character or escape sequence that does not map to a single-byte
4161 execution character, is implementation-defined. If an integer character constant contains
4162 a single character or escape sequence, its value is the one that results when an object with
4163 type char whose value is that of the single character or escape sequence is converted to
4164 type int.
4166 A wide character constant prefixed by the letter L has type wchar_t, an integer type
4167 defined in the <a href="#7.19"><stddef.h></a> header; a wide character constant prefixed by the letter u or
4168 U has type char16_t or char32_t, respectively, unsigned integer types defined in the
4169 <a href="#7.27"><uchar.h></a> header. The value of a wide character constant containing a single
4170 multibyte character that maps to a single member of the extended execution character set
4171 is the wide character corresponding to that multibyte character, as defined by the
4172 mbtowc, mbrtoc16, or mbrtoc32 function as appropriate for its type, with an
4173 implementation-defined current locale. The value of a wide character constant containing
4174 more than one multibyte character or a single multibyte character that maps to multiple
4175 members of the extended execution character set, or containing a multibyte character or
4176 escape sequence not represented in the extended execution character set, is
4177 implementation-defined.
4182 EXAMPLE 2 Consider implementations that use two's complement representation for integers and eight
4183 bits for objects that have type char. In an implementation in which type char has the same range of
4184 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
4185 same range of values as unsigned char, the character constant '\xFF' has the value +255.
4190 <!--page 88 -->
4192 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
4193 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
4194 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
4195 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
4196 escape sequence is terminated after three octal digits. (The value of this two-character integer character
4197 constant is implementation-defined.)
4200 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
4201 L'\1234' specifies the implementation-defined value that results from the combination of the values
4204 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbtowc function
4205 (<a href="#7.22.7.2">7.22.7.2</a>), Unicode utilities <a href="#7.27"><uchar.h></a> (<a href="#7.27">7.27</a>).
4208 <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,
4209 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
4210 </small>
4216 <pre>
4217 string-literal:
4219 encoding-prefix:
4220 u8
4221 u
4222 U
4223 L
4224 s-char-sequence:
4225 s-char
4226 s-char-sequence s-char
4227 s-char:
4228 any member of the source character set except
4229 the double-quote ", backslash \, or new-line character
4230 escape-sequence
4231 </pre>
4232 <p><b>Constraints</b>
4233 <p><!--para 2 -->
4234 A sequence of adjacent string literal tokens shall not include both a wide string literal and
4235 a UTF-8 string literal.
4236 <p><b>Description</b>
4237 <p><!--para 3 -->
4238 A character string literal is a sequence of zero or more multibyte characters enclosed in
4240 A wide string literal is the same, except prefixed by the letter L, u, or U.
4241 <p><!--para 4 -->
4242 The same considerations apply to each element of the sequence in a string literal as if it
4243 were in an integer character constant (for a character or UTF-8 string literal) or a wide
4244 character constant (for a wide string literal), except that the single-quote ' is
4245 representable either by itself or by the escape sequence \', but the double-quote " shall
4246 <!--page 89 -->
4247 be represented by the escape sequence \".
4248 <p><b>Semantics</b>
4249 <p><!--para 5 -->
4250 In translation phase 6, the multibyte character sequences specified by any sequence of
4251 adjacent character and identically-prefixed string literal tokens are concatenated into a
4252 single multibyte character sequence. If any of the tokens has an encoding prefix, the
4253 resulting multibyte character sequence is treated as having the same prefix; otherwise, it
4254 is treated as a character string literal. Whether differently-prefixed wide string literal
4255 tokens can be concatenated and, if so, the treatment of the resulting multibyte character
4256 sequence are implementation-defined.
4257 <p><!--para 6 -->
4258 In translation phase 7, a byte or code of value zero is appended to each multibyte
4259 character sequence that results from a string literal or literals.<sup><a href="#note78"><b>78)</b></a></sup> The multibyte character
4260 sequence is then used to initialize an array of static storage duration and length just
4261 sufficient to contain the sequence. For character string literals, the array elements have
4262 type char, and are initialized with the individual bytes of the multibyte character
4263 sequence. For UTF-8 string literals, the array elements have type char, and are
4264 initialized with the characters of the multibyte character sequence, as encoded in UTF-8.
4265 For wide string literals prefixed by the letter L, the array elements have type wchar_t
4266 and are initialized with the sequence of wide characters corresponding to the multibyte
4267 character sequence, as defined by the mbstowcs function with an implementation-
4268 defined current locale. For wide string literals prefixed by the letter u or U, the array
4269 elements have type char16_t or char32_t, respectively, and are initialized with the
4270 sequence of wide characters corresponding to the multibyte character sequence, as
4271 defined by successive calls to the mbrtoc16, or mbrtoc32 function as appropriate for
4272 its type, with an implementation-defined current locale. The value of a string literal
4273 containing a multibyte character or escape sequence not represented in the execution
4274 character set is implementation-defined.
4275 <p><!--para 7 -->
4276 It is unspecified whether these arrays are distinct provided their elements have the
4277 appropriate values. If the program attempts to modify such an array, the behavior is
4278 undefined.
4279 <p><!--para 8 -->
4280 EXAMPLE 1 This pair of adjacent character string literals
4281 <pre>
4283 </pre>
4284 produces a single character string literal containing the two characters whose values are '\x12' and '3',
4285 because escape sequences are converted into single members of the execution character set just prior to
4286 adjacent string literal concatenation.
4288 <p><!--para 9 -->
4289 EXAMPLE 2 Each of the sequences of adjacent string literal tokens
4293 <!--page 90 -->
4294 <pre>
4299 </pre>
4300 is equivalent to the string literal
4301 <pre>
4303 </pre>
4304 Likewise, each of the sequences
4305 <pre>
4310 </pre>
4311 is equivalent to
4312 <pre>
4314 </pre>
4316 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbstowcs
4317 function (<a href="#7.22.8.1">7.22.8.1</a>), Unicode utilities <a href="#7.27"><uchar.h></a> (<a href="#7.27">7.27</a>).
4319 <p><b>Footnotes</b>
4320 <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
4321 \0 escape sequence.
4322 </small>
4326 <p><b>Syntax</b>
4327 <p><!--para 1 -->
4328 <pre>
4329 punctuator: one of
4330 [ ] ( ) { } . ->
4331 ++ -- & * + - ~ !
4332 / % << >> < > <= >= == != ^ | && ||
4333 ? : ; ...
4334 = *= /= %= += -= <<= >>= &= ^= |=
4335 , # ##
4336 <: :> <% %> %: %:%:
4337 </pre>
4338 <p><b>Semantics</b>
4339 <p><!--para 2 -->
4340 A punctuator is a symbol that has independent syntactic and semantic significance.
4341 Depending on context, it may specify an operation to be performed (which in turn may
4342 yield a value or a function designator, produce a side effect, or some combination thereof)
4343 in which case it is known as an operator (other forms of operator also exist in some
4344 contexts). An operand is an entity on which an operator acts.
4345 <!--page 91 -->
4346 <p><!--para 3 -->
4348 <pre>
4349 <: :> <% %> %: %:%:
4350 </pre>
4351 behave, respectively, the same as the six tokens
4352 <pre>
4353 [ ] { } # ##
4354 </pre>
4356 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
4359 <p><b>Footnotes</b>
4360 <p><small><a name="note79" href="#note79">79)</a> These tokens are sometimes called ''digraphs''.
4361 </small>
4362 <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
4363 interchanged.
4364 </small>
4368 <p><b>Syntax</b>
4369 <p><!--para 1 -->
4370 <pre>
4371 header-name:
4372 < h-char-sequence >
4374 h-char-sequence:
4375 h-char
4376 h-char-sequence h-char
4377 h-char:
4378 any member of the source character set except
4379 the new-line character and >
4380 q-char-sequence:
4381 q-char
4382 q-char-sequence q-char
4383 q-char:
4384 any member of the source character set except
4385 the new-line character and "
4386 </pre>
4389 The sequences in both forms of header names are mapped in an implementation-defined
4392 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
4393 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
4398 <!--page 92 -->
4399 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note81"><b>81)</b></a></sup> Header name
4400 preprocessing tokens are recognized only within #include preprocessing directives and
4401 in implementation-defined locations within #pragma directives.<sup><a href="#note82"><b>82)</b></a></sup>
4403 EXAMPLE The following sequence of characters:
4404 <pre>
4407 #define const.member@$
4408 </pre>
4409 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
4410 by a { on the left and a } on the right).
4411 <pre>
4414 {#}{define} {const}{.}{member}{@}{$}
4415 </pre>
4420 <p><small><a name="note81" href="#note81">81)</a> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
4421 </small>
4422 <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>.
4423 </small>
4429 <pre>
4430 pp-number:
4431 digit
4432 . digit
4433 pp-number digit
4434 pp-number identifier-nondigit
4435 pp-number e sign
4436 pp-number E sign
4437 pp-number p sign
4438 pp-number P sign
4439 pp-number .
4440 </pre>
4443 A preprocessing number begins with a digit optionally preceded by a period (.) and may
4444 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
4445 p+, p-, P+, or P-.
4447 Preprocessing number tokens lexically include all floating and integer constant tokens.
4450 A preprocessing number does not have type or a value; it acquires both after a successful
4451 conversion (as part of translation phase 7) to a floating constant token or an integer
4452 constant token.
4455 <!--page 93 -->
4460 Except within a character constant, a string literal, or a comment, the characters /*
4461 introduce a comment. The contents of such a comment are examined only to identify
4462 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note83"><b>83)</b></a></sup>
4464 Except within a character constant, a string literal, or a comment, the characters //
4465 introduce a comment that includes all multibyte characters up to, but not including, the
4466 next new-line character. The contents of such a comment are examined only to identify
4467 multibyte characters and to find the terminating new-line character.
4469 EXAMPLE
4470 <pre>
4471 "a//b" // four-character string literal
4472 #include "//e" // undefined behavior
4473 // */ // comment, not syntax error
4474 f = g/**//h; // equivalent to f = g / h;
4475 //\
4476 i(); // part of a two-line comment
4477 /\
4478 / j(); // part of a two-line comment
4479 #define glue(x,y) x##y
4480 glue(/,/) k(); // syntax error, not comment
4481 /*//*/ l(); // equivalent to l();
4482 m = n//**/o
4483 + p; // equivalent to m = n + p;
4484 </pre>
4489 <!--page 94 -->
4493 </small>
4498 An expression is a sequence of operators and operands that specifies computation of a
4499 value, or that designates an object or a function, or that generates side effects, or that
4500 performs a combination thereof. The value computations of the operands of an operator
4501 are sequenced before the value computation of the result of the operator.
4503 If a side effect on a scalar object is unsequenced relative to either a different side effect
4504 on the same scalar object or a value computation using the value of the same scalar
4505 object, the behavior is undefined. If there are multiple allowable orderings of the
4506 subexpressions of an expression, the behavior is undefined if such an unsequenced side
4509 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note85"><b>85)</b></a></sup> Except as specified
4510 later, side effects and value computations of subexpressions are unsequenced.<sup><a href="#note86"><b>86)</b></a></sup> *
4512 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
4513 collectively described as bitwise operators) are required to have operands that have
4514 integer type. These operators yield values that depend on the internal representations of
4515 integers, and have implementation-defined and undefined aspects for signed types.
4517 If an exceptional condition occurs during the evaluation of an expression (that is, if the
4518 result is not mathematically defined or not in the range of representable values for its
4519 type), the behavior is undefined.
4523 <!--page 95 -->
4525 The effective type of an object for an access to its stored value is the declared type of the
4526 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
4527 lvalue having a type that is not a character type, then the type of the lvalue becomes the
4528 effective type of the object for that access and for subsequent accesses that do not modify
4529 the stored value. If a value is copied into an object having no declared type using
4530 memcpy or memmove, or is copied as an array of character type, then the effective type
4531 of the modified object for that access and for subsequent accesses that do not modify the
4532 value is the effective type of the object from which the value is copied, if it has one. For
4533 all other accesses to an object having no declared type, the effective type of the object is
4534 simply the type of the lvalue used for the access.
4536 An object shall have its stored value accessed only by an lvalue expression that has one of
4538 <ul>
4539 <li> a type compatible with the effective type of the object,
4540 <li> a qualified version of a type compatible with the effective type of the object,
4541 <li> a type that is the signed or unsigned type corresponding to the effective type of the
4542 object,
4543 <li> a type that is the signed or unsigned type corresponding to a qualified version of the
4544 effective type of the object,
4545 <li> an aggregate or union type that includes one of the aforementioned types among its
4546 members (including, recursively, a member of a subaggregate or contained union), or
4547 <li> a character type.
4548 </ul>
4550 A floating expression may be contracted, that is, evaluated as though it were a single
4551 operation, thereby omitting rounding errors implied by the source code and the
4552 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
4553 way to disallow contracted expressions. Otherwise, whether and how expressions are
4555 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), copying functions (<a href="#7.23.2">7.23.2</a>).
4558 <!--page 96 -->
4561 <p><small><a name="note84" href="#note84">84)</a> This paragraph renders undefined statement expressions such as
4563 <pre>
4564 i = ++i + 1;
4565 a[i++] = i;
4566 </pre>
4567 while allowing
4569 <pre>
4570 i = i + 1;
4571 a[i] = i;
4572 </pre>
4574 </small>
4575 <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
4576 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
4577 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
4578 <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
4579 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
4580 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
4582 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
4583 indicated in each subclause by the syntax for the expressions discussed therein.
4584 </small>
4585 <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
4586 indeterminately sequenced evaluations of its subexpressions need not be performed consistently in
4587 different evaluations.
4588 </small>
4590 </small>
4591 <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.
4592 </small>
4593 <p><small><a name="note89" href="#note89">89)</a> The intermediate operations in the contracted expression are evaluated as if to infinite precision and
4594 range, while the final operation is rounded to the format determined by the expression evaluation
4595 method. A contracted expression might also omit the raising of floating-point exceptions.
4596 </small>
4597 <p><small><a name="note90" href="#note90">90)</a> This license is specifically intended to allow implementations to exploit fast machine instructions that
4598 combine multiple C operators. As contractions potentially undermine predictability, and can even
4599 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
4600 documented.
4601 </small>
4607 <pre>
4608 primary-expression:
4609 identifier
4610 constant
4611 string-literal
4612 ( expression )
4613 generic-selection
4614 </pre>
4617 An identifier is a primary expression, provided it has been declared as designating an
4618 object (in which case it is an lvalue) or a function (in which case it is a function
4621 A constant is a primary expression. Its type depends on its form and value, as detailed in
4624 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>.
4626 A parenthesized expression is a primary expression. Its type and value are identical to
4627 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
4628 expression if the unparenthesized expression is, respectively, an lvalue, a function
4629 designator, or a void expression.
4633 <p><small><a name="note91" href="#note91">91)</a> Thus, an undeclared identifier is a violation of the syntax.
4634 </small>
4640 <pre>
4641 generic-selection:
4642 _Generic ( assignment-expression , generic-assoc-list )
4643 generic-assoc-list:
4644 generic-association
4645 generic-assoc-list , generic-association
4646 generic-association:
4647 type-name : assignment-expression
4648 default : assignment-expression
4649 </pre>
4652 A generic selection shall have no more than one default generic association. The type
4653 name in a generic association shall specify a complete object type other than a variably
4655 <!--page 97 -->
4656 modified type. No two generic associations in the same generic selection shall specify
4657 compatible types. The controlling expression of a generic selection shall have type
4658 compatible with at most one of the types named in its generic association list. If a
4659 generic selection has no default generic association, its controlling expression shall
4660 have type compatible with exactly one of the types named in its generic association list.
4663 The controlling expression of a generic selection is not evaluated. If a generic selection
4664 has a generic association with a type name that is compatible with the type of the
4665 controlling expression, then the result expression of the generic selection is the
4666 expression in that generic association. Otherwise, the result expression of the generic
4667 selection is the expression in the default generic association. None of the expressions
4668 from any other generic association of the generic selection is evaluated.
4670 The type and value of a generic selection are identical to those of its result expression. It
4671 is an lvalue, a function designator, or a void expression if its result expression is,
4672 respectively, an lvalue, a function designator, or a void expression.
4674 EXAMPLE The cbrt type-generic macro could be implemented as follows:
4675 <pre>
4676 #define cbrt(X) _Generic((X), \
4677 long double: cbrtl, \
4678 default: cbrt, \
4679 float: cbrtf \
4680 )(X)
4681 </pre>
4688 <!--page 98 -->
4689 <pre>
4690 postfix-expression:
4691 primary-expression
4692 postfix-expression [ expression ]
4694 postfix-expression . identifier
4695 postfix-expression -> identifier
4696 postfix-expression ++
4697 postfix-expression --
4698 ( type-name ) { initializer-list }
4699 ( type-name ) { initializer-list , }
4700 argument-expression-list:
4701 assignment-expression
4702 argument-expression-list , assignment-expression
4703 </pre>
4709 One of the expressions shall have type ''pointer to complete object type'', the other
4710 expression shall have integer type, and the result has type ''type''.
4713 A postfix expression followed by an expression in square brackets [] is a subscripted
4714 designation of an element of an array object. The definition of the subscript operator []
4715 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
4716 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
4717 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
4718 element of E1 (counting from zero).
4720 Successive subscript operators designate an element of a multidimensional array object.
4722 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
4723 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
4724 implicitly as a result of subscripting, the result is the referenced (n - 1)-dimensional
4725 array, which itself is converted into a pointer if used as other than an lvalue. It follows
4726 from this that arrays are stored in row-major order (last subscript varies fastest).
4728 EXAMPLE Consider the array object defined by the declaration
4729 <pre>
4731 </pre>
4732 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
4733 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
4734 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
4735 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
4736 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
4737 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
4738 yields an int.
4740 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
4747 The expression that denotes the called function<sup><a href="#note92"><b>92)</b></a></sup> shall have type pointer to function
4748 returning void or returning a complete object type other than an array type.
4750 If the expression that denotes the called function has a type that includes a prototype, the
4751 number of arguments shall agree with the number of parameters. Each argument shall
4754 <!--page 99 -->
4755 have a type such that its value may be assigned to an object with the unqualified version
4756 of the type of its corresponding parameter.
4759 A postfix expression followed by parentheses () containing a possibly empty, comma-
4760 separated list of expressions is a function call. The postfix expression denotes the called
4761 function. The list of expressions specifies the arguments to the function.
4763 An argument may be an expression of any complete object type. In preparing for the call
4764 to a function, the arguments are evaluated, and each parameter is assigned the value of the
4767 If the expression that denotes the called function has type pointer to function returning an
4768 object type, the function call expression has the same type as that object type, and has the
4769 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void. *
4771 If the expression that denotes the called function has a type that does not include a
4772 prototype, the integer promotions are performed on each argument, and arguments that
4773 have type float are promoted to double. These are called the default argument
4774 promotions. If the number of arguments does not equal the number of parameters, the
4775 behavior is undefined. If the function is defined with a type that includes a prototype, and
4776 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
4777 promotion are not compatible with the types of the parameters, the behavior is undefined.
4778 If the function is defined with a type that does not include a prototype, and the types of
4779 the arguments after promotion are not compatible with those of the parameters after
4780 promotion, the behavior is undefined, except for the following cases:
4781 <ul>
4782 <li> one promoted type is a signed integer type, the other promoted type is the
4783 corresponding unsigned integer type, and the value is representable in both types;
4784 <li> both types are pointers to qualified or unqualified versions of a character type or
4785 void.
4786 </ul>
4788 If the expression that denotes the called function has a type that does include a prototype,
4789 the arguments are implicitly converted, as if by assignment, to the types of the
4790 corresponding parameters, taking the type of each parameter to be the unqualified version
4791 of its declared type. The ellipsis notation in a function prototype declarator causes
4792 argument type conversion to stop after the last declared parameter. The default argument
4793 promotions are performed on trailing arguments.
4797 <!--page 100 -->
4799 No other conversions are performed implicitly; in particular, the number and types of
4800 arguments are not compared with those of the parameters in a function definition that
4801 does not include a function prototype declarator.
4803 If the function is defined with a type that is not compatible with the type (of the
4804 expression) pointed to by the expression that denotes the called function, the behavior is
4805 undefined.
4807 There is a sequence point after the evaluations of the function designator and the actual
4808 arguments but before the actual call. Every evaluation in the calling function (including
4809 other function calls) that is not otherwise specifically sequenced before or after the
4810 execution of the body of the called function is indeterminately sequenced with respect to
4813 Recursive function calls shall be permitted, both directly and indirectly through any chain
4814 of other functions.
4816 EXAMPLE In the function call
4817 <pre>
4818 (*pf[f1()]) (f2(), f3() + f4())
4819 </pre>
4820 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
4821 the function pointed to by pf[f1()] is called.
4823 <p><b> Forward references</b>: function declarators (including prototypes) (<a href="#6.7.6.3">6.7.6.3</a>), function
4824 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>).
4827 <p><small><a name="note92" href="#note92">92)</a> Most often, this is the result of converting an identifier that is a function designator.
4828 </small>
4829 <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
4830 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
4831 change the value of the object pointed to. A parameter declared to have array or function type is
4833 </small>
4834 <p><small><a name="note94" href="#note94">94)</a> In other words, function executions do not ''interleave'' with each other.
4835 </small>
4841 The first operand of the . operator shall have an atomic, qualified, or unqualified
4842 structure or union type, and the second operand shall name a member of that type.
4844 The first operand of the -> operator shall have type ''pointer to atomic, qualified, or
4845 unqualified structure'' or ''pointer to atomic, qualified, or unqualified union'', and the
4846 second operand shall name a member of the type pointed to.
4849 A postfix expression followed by the . operator and an identifier designates a member of
4850 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
4851 the first expression is an lvalue. If the first expression has qualified type, the result has
4852 the so-qualified version of the type of the designated member.
4854 <!--page 101 -->
4856 A postfix expression followed by the -> operator and an identifier designates a member
4857 of a structure or union object. The value is that of the named member of the object to
4858 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
4859 a qualified type, the result has the so-qualified version of the type of the designated
4860 member.
4862 Accessing a member of an atomic structure or union object results in undefined
4865 One special guarantee is made in order to simplify the use of unions: if a union contains
4866 several structures that share a common initial sequence (see below), and if the union
4867 object currently contains one of these structures, it is permitted to inspect the common
4868 initial part of any of them anywhere that a declaration of the completed type of the union
4869 is visible. Two structures share a common initial sequence if corresponding members
4870 have compatible types (and, for bit-fields, the same widths) for a sequence of one or more
4871 initial members.
4873 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
4874 union, f().x is a valid postfix expression but is not an lvalue.
4877 EXAMPLE 2 In:
4878 <pre>
4879 struct s { int i; const int ci; };
4880 struct s s;
4881 const struct s cs;
4882 volatile struct s vs;
4883 </pre>
4884 the various members have the types:
4885 <pre>
4886 s.i int
4887 s.ci const int
4888 cs.i const int
4889 cs.ci const int
4890 vs.i volatile int
4891 vs.ci volatile const int
4892 </pre>
4897 <!--page 102 -->
4899 EXAMPLE 3 The following is a valid fragment:
4900 <pre>
4901 union {
4902 struct {
4903 int alltypes;
4904 } n;
4905 struct {
4906 int type;
4907 int intnode;
4908 } ni;
4909 struct {
4910 int type;
4911 double doublenode;
4912 } nf;
4913 } u;
4914 u.nf.type = 1;
4916 /* ... */
4917 if (u.n.alltypes == 1)
4918 if (sin(u.nf.doublenode) == 0.0)
4919 /* ... */
4920 </pre>
4921 The following is not a valid fragment (because the union type is not visible within function f):
4922 <pre>
4923 struct t1 { int m; };
4924 struct t2 { int m; };
4925 int f(struct t1 *p1, struct t2 *p2)
4926 {
4929 return p1->m;
4930 }
4931 int g()
4932 {
4933 union {
4934 struct t1 s1;
4935 struct t2 s2;
4936 } u;
4937 /* ... */
4939 }
4940 </pre>
4942 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
4944 <!--page 103 -->
4947 <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
4948 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
4949 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
4950 punning''). This might be a trap representation.
4951 </small>
4952 <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
4954 </small>
4955 <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
4956 with access to a member from another thread, where at least one access is a modification. Members
4957 can be safely accessed using a non-atomic object which is assigned to or from the atomic object.
4958 </small>
4961 <h5><a name="6.5.2.4" href="#6.5.2.4">6.5.2.4 Postfix increment and decrement operators</a></h5>
4964 The operand of the postfix increment or decrement operator shall have atomic, qualified,
4965 or unqualified real or pointer type, and shall be a modifiable lvalue.
4968 The result of the postfix ++ operator is the value of the operand. As a side effect, the
4969 value of the operand object is incremented (that is, the value 1 of the appropriate type is
4970 added to it). See the discussions of additive operators and compound assignment for
4971 information on constraints, types, and conversions and the effects of operations on
4972 pointers. The value computation of the result is sequenced before the side effect of
4973 updating the stored value of the operand. With respect to an indeterminately-sequenced
4974 function call, the operation of postfix ++ is a single evaluation. Postfix ++ on an object
4975 with atomic type is a read-modify-write operation with memory_order_seq_cst
4978 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
4979 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
4980 it).
4981 <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>).
4984 <p><small><a name="note98" href="#note98">98)</a> Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence
4985 where T is the type of E:
4987 <pre>
4988 T tmp;
4989 T result = E;
4990 do {
4991 tmp = result + 1;
4993 </pre>
4994 with result being the result of the operation.
4995 </small>
5001 The type name shall specify a complete object type or an array of unknown size, but not a
5002 variable length array type.
5004 All the constraints for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.
5007 A postfix expression that consists of a parenthesized type name followed by a brace-
5008 enclosed list of initializers is a compound literal. It provides an unnamed object whose
5012 <!--page 104 -->
5014 If the type name specifies an array of unknown size, the size is determined by the
5015 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
5016 completed array type. Otherwise (when the type name specifies an object type), the type
5017 of the compound literal is that specified by the type name. In either case, the result is an
5018 lvalue.
5020 The value of the compound literal is that of an unnamed object initialized by the
5021 initializer list. If the compound literal occurs outside the body of a function, the object
5022 has static storage duration; otherwise, it has automatic storage duration associated with
5023 the enclosing block.
5025 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>
5027 String literals, and compound literals with const-qualified types, need not designate
5030 EXAMPLE 1 The file scope definition
5031 <pre>
5033 </pre>
5034 initializes p to point to the first element of an array of two ints, the first having the value two and the
5035 second, four. The expressions in this compound literal are required to be constant. The unnamed object
5036 has static storage duration.
5039 EXAMPLE 2 In contrast, in
5040 <pre>
5041 void f(void)
5042 {
5043 int *p;
5044 /*...*/
5045 p = (int [2]){*p};
5046 /*...*/
5047 }
5048 </pre>
5049 p is assigned the address of the first element of an array of two ints, the first having the value previously
5050 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
5051 unnamed object has automatic storage duration.
5054 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
5055 created using compound literals can be passed to functions without depending on member order:
5056 <pre>
5059 </pre>
5060 Or, if drawline instead expected pointers to struct point:
5064 <!--page 105 -->
5065 <pre>
5068 </pre>
5071 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
5072 <pre>
5074 </pre>
5077 EXAMPLE 5 The following three expressions have different meanings:
5078 <pre>
5079 "/tmp/fileXXXXXX"
5080 (char []){"/tmp/fileXXXXXX"}
5081 (const char []){"/tmp/fileXXXXXX"}
5082 </pre>
5083 The first always has static storage duration and has type array of char, but need not be modifiable; the last
5084 two have automatic storage duration when they occur within the body of a function, and the first of these
5085 two is modifiable.
5088 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
5089 and can even be shared. For example,
5090 <pre>
5092 </pre>
5093 might yield 1 if the literals' storage is shared.
5096 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
5097 linked object. For example, there is no way to write a self-referential compound literal that could be used
5098 as the function argument in place of the named object endless_zeros below:
5099 <pre>
5100 struct int_list { int car; struct int_list *cdr; };
5102 eval(endless_zeros);
5103 </pre>
5106 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
5107 <pre>
5108 struct s { int i; };
5109 int f (void)
5110 {
5111 struct s *p = 0, *q;
5112 int j = 0;
5113 again:
5114 q = p, p = &((struct s){ j++ });
5117 }
5118 </pre>
5119 The function f() always returns the value 1.
5121 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
5122 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
5123 have an indeterminate value, which would result in undefined behavior.
5125 <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>).
5126 <!--page 106 -->
5129 <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
5130 or void only, and the result of a cast expression is not an lvalue.
5131 </small>
5132 <p><small><a name="note100" href="#note100">100)</a> For example, subobjects without explicit initializers are initialized to zero.
5133 </small>
5134 <p><small><a name="note101" href="#note101">101)</a> This allows implementations to share storage for string literals and constant compound literals with
5135 the same or overlapping representations.
5136 </small>
5142 <pre>
5143 unary-expression:
5144 postfix-expression
5145 ++ unary-expression
5146 -- unary-expression
5147 unary-operator cast-expression
5148 sizeof unary-expression
5149 sizeof ( type-name )
5150 alignof ( type-name )
5151 unary-operator: one of
5152 & * + - ~ !
5153 </pre>
5156 <h5><a name="6.5.3.1" href="#6.5.3.1">6.5.3.1 Prefix increment and decrement operators</a></h5>
5159 The operand of the prefix increment or decrement operator shall have atomic, qualified,
5160 or unqualified real or pointer type, and shall be a modifiable lvalue.
5163 The value of the operand of the prefix ++ operator is incremented. The result is the new
5164 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
5165 See the discussions of additive operators and compound assignment for information on
5166 constraints, types, side effects, and conversions and the effects of operations on pointers.
5168 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
5169 operand is decremented.
5170 <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>).
5176 The operand of the unary & operator shall be either a function designator, the result of a
5177 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
5178 not declared with the register storage-class specifier.
5180 The operand of the unary * operator shall have pointer type.
5183 The unary & operator yields the address of its operand. If the operand has type ''type'',
5184 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
5185 neither that operator nor the & operator is evaluated and the result is as if both were
5186 omitted, except that the constraints on the operators still apply and the result is not an
5187 <!--page 107 -->
5188 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
5189 the unary * that is implied by the [] is evaluated and the result is as if the & operator
5190 were removed and the [] operator were changed to a + operator. Otherwise, the result is
5191 a pointer to the object or function designated by its operand.
5193 The unary * operator denotes indirection. If the operand points to a function, the result is
5194 a function designator; if it points to an object, the result is an lvalue designating the
5195 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
5196 invalid value has been assigned to the pointer, the behavior of the unary * operator is
5198 <p><b> Forward references</b>: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
5202 <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
5203 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
5204 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
5205 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
5206 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
5207 address inappropriately aligned for the type of object pointed to, and the address of an object after the
5208 end of its lifetime.
5209 </small>
5215 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
5216 integer type; of the ! operator, scalar type.
5219 The result of the unary + operator is the value of its (promoted) operand. The integer
5220 promotions are performed on the operand, and the result has the promoted type.
5222 The result of the unary - operator is the negative of its (promoted) operand. The integer
5223 promotions are performed on the operand, and the result has the promoted type.
5225 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
5226 each bit in the result is set if and only if the corresponding bit in the converted operand is
5227 not set). The integer promotions are performed on the operand, and the result has the
5228 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
5229 to the maximum value representable in that type minus E.
5231 The result of the logical negation operator ! is 0 if the value of its operand compares
5233 The expression !E is equivalent to (0==E).
5237 <!--page 108 -->
5243 The sizeof operator shall not be applied to an expression that has function type or an
5244 incomplete type, to the parenthesized name of such a type, or to an expression that
5245 designates a bit-field member. The alignof operator shall not be applied to a function
5246 type or an incomplete type.
5249 The sizeof operator yields the size (in bytes) of its operand, which may be an
5250 expression or the parenthesized name of a type. The size is determined from the type of
5251 the operand. The result is an integer. If the type of the operand is a variable length array
5252 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
5253 integer constant.
5255 The alignof operator yields the alignment requirement of its operand type. The result
5256 is an integer constant. When applied to an array type, the result is the alignment
5257 requirement of the element type.
5259 When sizeof is applied to an operand that has type char, unsigned char, or
5260 signed char, (or a qualified version thereof) the result is 1. When applied to an
5261 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
5262 applied to an operand that has structure or union type, the result is the total number of
5263 bytes in such an object, including internal and trailing padding.
5265 The value of the result of both operators is implementation-defined, and its type (an
5266 unsigned integer type) is size_t, defined in <a href="#7.19"><stddef.h></a> (and other headers).
5268 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
5269 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
5270 allocate and return a pointer to void. For example:
5271 <pre>
5272 extern void *alloc(size_t);
5273 double *dp = alloc(sizeof *dp);
5274 </pre>
5275 The implementation of the alloc function should ensure that its return value is aligned suitably for
5276 conversion to a pointer to double.
5279 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
5280 <pre>
5281 sizeof array / sizeof array[0]
5282 </pre>
5285 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
5286 function:
5287 <pre>
5289 </pre>
5293 <!--page 109 -->
5294 <pre>
5295 size_t fsize3(int n)
5296 {
5297 char b[n+3]; // variable length array
5298 return sizeof b; // execution time sizeof
5299 }
5300 int main()
5301 {
5302 size_t size;
5304 return 0;
5305 }
5306 </pre>
5308 <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>),
5309 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>).
5312 <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
5314 </small>
5320 <pre>
5321 cast-expression:
5322 unary-expression
5323 ( type-name ) cast-expression
5324 </pre>
5327 Unless the type name specifies a void type, the type name shall specify atomic, qualified,
5328 or unqualified scalar type, and the operand shall have scalar type.
5330 Conversions that involve pointers, other than where permitted by the constraints of
5333 A pointer type shall not be converted to any floating type. A floating type shall not be
5334 converted to any pointer type.
5337 Preceding an expression by a parenthesized type name converts the value of the
5338 expression to the named type. This construction is called a cast.<sup><a href="#note104"><b>104)</b></a></sup> A cast that specifies
5339 no conversion has no effect on the type or value of an expression.
5341 If the value of the expression is represented with greater precision or range than required
5342 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
5343 type of the expression is the same as the named type and removes any extra range and
5344 precision.
5345 <p><b> Forward references</b>: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
5346 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>).
5348 <!--page 110 -->
5351 <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
5352 unqualified version of the type.
5353 </small>
5359 <pre>
5360 multiplicative-expression:
5361 cast-expression
5362 multiplicative-expression * cast-expression
5363 multiplicative-expression / cast-expression
5364 multiplicative-expression % cast-expression
5365 </pre>
5368 Each of the operands shall have arithmetic type. The operands of the % operator shall
5369 have integer type.
5372 The usual arithmetic conversions are performed on the operands.
5374 The result of the binary * operator is the product of the operands.
5376 The result of the / operator is the quotient from the division of the first operand by the
5377 second; the result of the % operator is the remainder. In both operations, if the value of
5378 the second operand is zero, the behavior is undefined.
5380 When integers are divided, the result of the / operator is the algebraic quotient with any
5381 fractional part discarded.<sup><a href="#note105"><b>105)</b></a></sup> If the quotient a/b is representable, the expression
5382 (a/b)*b + a%b shall equal a; otherwise, the behavior of both a/b and a%b is
5383 undefined.
5386 <p><small><a name="note105" href="#note105">105)</a> This is often called ''truncation toward zero''.
5387 </small>
5393 <pre>
5394 additive-expression:
5395 multiplicative-expression
5396 additive-expression + multiplicative-expression
5397 additive-expression - multiplicative-expression
5398 </pre>
5401 For addition, either both operands shall have arithmetic type, or one operand shall be a
5402 pointer to a complete object type and the other shall have integer type. (Incrementing is
5403 equivalent to adding 1.)
5405 For subtraction, one of the following shall hold:
5410 <!--page 111 -->
5411 <ul>
5412 <li> both operands have arithmetic type;
5413 <li> both operands are pointers to qualified or unqualified versions of compatible complete
5414 object types; or
5415 <li> the left operand is a pointer to a complete object type and the right operand has
5416 integer type.
5417 </ul>
5418 (Decrementing is equivalent to subtracting 1.)
5421 If both operands have arithmetic type, the usual arithmetic conversions are performed on
5422 them.
5424 The result of the binary + operator is the sum of the operands.
5426 The result of the binary - operator is the difference resulting from the subtraction of the
5427 second operand from the first.
5429 For the purposes of these operators, a pointer to an object that is not an element of an
5430 array behaves the same as a pointer to the first element of an array of length one with the
5431 type of the object as its element type.
5433 When an expression that has integer type is added to or subtracted from a pointer, the
5434 result has the type of the pointer operand. If the pointer operand points to an element of
5435 an array object, and the array is large enough, the result points to an element offset from
5436 the original element such that the difference of the subscripts of the resulting and original
5437 array elements equals the integer expression. In other words, if the expression P points to
5438 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
5439 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
5440 the array object, provided they exist. Moreover, if the expression P points to the last
5441 element of an array object, the expression (P)+1 points one past the last element of the
5442 array object, and if the expression Q points one past the last element of an array object,
5443 the expression (Q)-1 points to the last element of the array object. If both the pointer
5444 operand and the result point to elements of the same array object, or one past the last
5445 element of the array object, the evaluation shall not produce an overflow; otherwise, the
5446 behavior is undefined. If the result points one past the last element of the array object, it
5447 shall not be used as the operand of a unary * operator that is evaluated.
5449 When two pointers are subtracted, both shall point to elements of the same array object,
5450 or one past the last element of the array object; the result is the difference of the
5451 subscripts of the two array elements. The size of the result is implementation-defined,
5452 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.19"><stddef.h></a> header.
5453 If the result is not representable in an object of that type, the behavior is undefined. In
5454 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
5455 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
5456 <!--page 112 -->
5457 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
5458 an array object or one past the last element of an array object, and the expression Q points
5459 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
5461 expression P points one past the last element of the array object, even though the
5462 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note106"><b>106)</b></a></sup>
5464 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
5465 <pre>
5466 {
5468 int a[n][m];
5472 n = p - a; // n == 1
5473 }
5474 </pre>
5476 If array a in the above example were declared to be an array of known constant size, and pointer p were
5477 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
5478 the same.
5480 <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>
5484 <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
5485 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
5486 by the size of the object originally pointed to, and the resulting pointer is converted back to the
5487 original type. For pointer subtraction, the result of the difference between the character pointers is
5488 similarly divided by the size of the object originally pointed to.
5489 When viewed in this way, an implementation need only provide one extra byte (which may overlap
5490 another object in the program) just after the end of the object in order to satisfy the ''one past the last
5491 element'' requirements.
5492 </small>
5498 <pre>
5499 shift-expression:
5500 additive-expression
5501 shift-expression << additive-expression
5502 shift-expression >> additive-expression
5503 </pre>
5506 Each of the operands shall have integer type.
5509 The integer promotions are performed on each of the operands. The type of the result is
5510 that of the promoted left operand. If the value of the right operand is negative or is
5512 <!--page 113 -->
5513 greater than or equal to the width of the promoted left operand, the behavior is undefined.
5515 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
5516 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
5517 one more than the maximum value representable in the result type. If E1 has a signed
5518 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
5519 the resulting value; otherwise, the behavior is undefined.
5521 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
5522 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
5523 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
5524 resulting value is implementation-defined.
5530 <pre>
5531 relational-expression:
5532 shift-expression
5533 relational-expression < shift-expression
5534 relational-expression > shift-expression
5535 relational-expression <= shift-expression
5536 relational-expression >= shift-expression
5537 </pre>
5540 One of the following shall hold:
5541 <ul>
5542 <li> both operands have real type; or *
5543 <li> both operands are pointers to qualified or unqualified versions of compatible object
5544 types.
5545 </ul>
5548 If both of the operands have arithmetic type, the usual arithmetic conversions are
5549 performed.
5551 For the purposes of these operators, a pointer to an object that is not an element of an
5552 array behaves the same as a pointer to the first element of an array of length one with the
5553 type of the object as its element type.
5555 When two pointers are compared, the result depends on the relative locations in the
5556 address space of the objects pointed to. If two pointers to object types both point to the
5557 same object, or both point one past the last element of the same array object, they
5558 compare equal. If the objects pointed to are members of the same aggregate object,
5559 pointers to structure members declared later compare greater than pointers to members
5560 declared earlier in the structure, and pointers to array elements with larger subscript
5561 values compare greater than pointers to elements of the same array with lower subscript
5562 <!--page 114 -->
5563 values. All pointers to members of the same union object compare equal. If the
5564 expression P points to an element of an array object and the expression Q points to the
5565 last element of the same array object, the pointer expression Q+1 compares greater than
5566 P. In all other cases, the behavior is undefined.
5568 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
5573 <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
5574 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
5575 </small>
5581 <pre>
5582 equality-expression:
5583 relational-expression
5584 equality-expression == relational-expression
5585 equality-expression != relational-expression
5586 </pre>
5589 One of the following shall hold:
5590 <ul>
5591 <li> both operands have arithmetic type;
5592 <li> both operands are pointers to qualified or unqualified versions of compatible types;
5593 <li> one operand is a pointer to an object type and the other is a pointer to a qualified or
5594 unqualified version of void; or
5595 <li> one operand is a pointer and the other is a null pointer constant.
5596 </ul>
5599 The == (equal to) and != (not equal to) operators are analogous to the relational
5600 operators except for their lower precedence.<sup><a href="#note108"><b>108)</b></a></sup> Each of the operators yields 1 if the
5601 specified relation is true and 0 if it is false. The result has type int. For any pair of
5602 operands, exactly one of the relations is true.
5604 If both of the operands have arithmetic type, the usual arithmetic conversions are
5605 performed. Values of complex types are equal if and only if both their real parts are equal
5606 and also their imaginary parts are equal. Any two values of arithmetic types from
5607 different type domains are equal if and only if the results of their conversions to the
5608 (complex) result type determined by the usual arithmetic conversions are equal.
5612 <!--page 115 -->
5614 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
5615 null pointer constant, the null pointer constant is converted to the type of the pointer. If
5616 one operand is a pointer to an object type and the other is a pointer to a qualified or
5617 unqualified version of void, the former is converted to the type of the latter.
5619 Two pointers compare equal if and only if both are null pointers, both are pointers to the
5620 same object (including a pointer to an object and a subobject at its beginning) or function,
5621 both are pointers to one past the last element of the same array object, or one is a pointer
5622 to one past the end of one array object and the other is a pointer to the start of a different
5623 array object that happens to immediately follow the first array object in the address
5626 For the purposes of these operators, a pointer to an object that is not an element of an
5627 array behaves the same as a pointer to the first element of an array of length one with the
5628 type of the object as its element type.
5631 <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.
5632 </small>
5633 <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
5634 adjacent members of a structure with no padding between them, or because the implementation chose
5635 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
5636 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
5637 behavior.
5638 </small>
5644 <pre>
5645 AND-expression:
5646 equality-expression
5647 AND-expression & equality-expression
5648 </pre>
5651 Each of the operands shall have integer type.
5654 The usual arithmetic conversions are performed on the operands.
5656 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
5657 the result is set if and only if each of the corresponding bits in the converted operands is
5658 set).
5663 <!--page 116 -->
5669 <pre>
5670 exclusive-OR-expression:
5671 AND-expression
5672 exclusive-OR-expression ^ AND-expression
5673 </pre>
5676 Each of the operands shall have integer type.
5679 The usual arithmetic conversions are performed on the operands.
5681 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
5682 in the result is set if and only if exactly one of the corresponding bits in the converted
5683 operands is set).
5689 <pre>
5690 inclusive-OR-expression:
5691 exclusive-OR-expression
5692 inclusive-OR-expression | exclusive-OR-expression
5693 </pre>
5696 Each of the operands shall have integer type.
5699 The usual arithmetic conversions are performed on the operands.
5701 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
5702 the result is set if and only if at least one of the corresponding bits in the converted
5703 operands is set).
5704 <!--page 117 -->
5710 <pre>
5711 logical-AND-expression:
5712 inclusive-OR-expression
5713 logical-AND-expression && inclusive-OR-expression
5714 </pre>
5717 Each of the operands shall have scalar type.
5720 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
5721 yields 0. The result has type int.
5723 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
5724 if the second operand is evaluated, there is a sequence point between the evaluations of
5725 the first and second operands. If the first operand compares equal to 0, the second
5726 operand is not evaluated.
5732 <pre>
5733 logical-OR-expression:
5734 logical-AND-expression
5735 logical-OR-expression || logical-AND-expression
5736 </pre>
5739 Each of the operands shall have scalar type.
5743 yields 0. The result has type int.
5745 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; if the
5746 second operand is evaluated, there is a sequence point between the evaluations of the first
5747 and second operands. If the first operand compares unequal to 0, the second operand is
5748 not evaluated.
5749 <!--page 118 -->
5755 <pre>
5756 conditional-expression:
5757 logical-OR-expression
5758 logical-OR-expression ? expression : conditional-expression
5759 </pre>
5762 The first operand shall have scalar type.
5764 One of the following shall hold for the second and third operands:
5765 <ul>
5766 <li> both operands have arithmetic type;
5767 <li> both operands have the same structure or union type;
5768 <li> both operands have void type;
5769 <li> both operands are pointers to qualified or unqualified versions of compatible types;
5770 <li> one operand is a pointer and the other is a null pointer constant; or
5771 <li> one operand is a pointer to an object type and the other is a pointer to a qualified or
5772 unqualified version of void.
5773 </ul>
5776 The first operand is evaluated; there is a sequence point between its evaluation and the
5777 evaluation of the second or third operand (whichever is evaluated). The second operand
5778 is evaluated only if the first compares unequal to 0; the third operand is evaluated only if
5779 the first compares equal to 0; the result is the value of the second or third operand
5780 (whichever is evaluated), converted to the type described below.<sup><a href="#note110"><b>110)</b></a></sup> *
5782 If both the second and third operands have arithmetic type, the result type that would be
5783 determined by the usual arithmetic conversions, were they applied to those two operands,
5784 is the type of the result. If both the operands have structure or union type, the result has
5785 that type. If both operands have void type, the result has void type.
5787 If both the second and third operands are pointers or one is a null pointer constant and the
5788 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
5789 of the types referenced by both operands. Furthermore, if both operands are pointers to
5790 compatible types or to differently qualified versions of compatible types, the result type is
5791 a pointer to an appropriately qualified version of the composite type; if one operand is a
5792 null pointer constant, the result has the type of the other operand; otherwise, one operand
5793 is a pointer to void or a qualified version of void, in which case the result type is a
5794 pointer to an appropriately qualified version of void.
5796 <!--page 119 -->
5798 EXAMPLE The common type that results when the second and third operands are pointers is determined
5799 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
5800 pointers have compatible types.
5802 Given the declarations
5803 <pre>
5804 const void *c_vp;
5805 void *vp;
5806 const int *c_ip;
5807 volatile int *v_ip;
5808 int *ip;
5809 const char *c_cp;
5810 </pre>
5811 the third column in the following table is the common type that is the result of a conditional expression in
5812 which the first two columns are the second and third operands (in either order):
5813 <pre>
5814 c_vp c_ip const void *
5815 v_ip 0 volatile int *
5816 c_ip v_ip const volatile int *
5817 vp c_cp const void *
5818 ip c_ip const int *
5819 vp ip void *
5820 </pre>
5824 <p><small><a name="note110" href="#note110">110)</a> A conditional expression does not yield an lvalue.
5825 </small>
5831 <pre>
5832 assignment-expression:
5833 conditional-expression
5834 unary-expression assignment-operator assignment-expression
5835 assignment-operator: one of
5837 </pre>
5840 An assignment operator shall have a modifiable lvalue as its left operand.
5843 An assignment operator stores a value in the object designated by the left operand. An
5844 assignment expression has the value of the left operand after the assignment,<sup><a href="#note111"><b>111)</b></a></sup> but is not
5845 an lvalue. The type of an assignment expression is the type the left operand would have
5846 after lvalue conversion. The side effect of updating the stored value of the left operand is
5847 sequenced after the value computations of the left and right operands. The evaluations of
5848 the operands are unsequenced.
5853 <!--page 120 -->
5856 <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
5857 when the object has volatile-qualified type.
5858 </small>
5865 <ul>
5866 <li> the left operand has atomic, qualified, or unqualified arithmetic type, and the right has
5867 arithmetic type;
5868 <li> the left operand has an atomic, qualified, or unqualified version of a structure or union
5869 type compatible with the type of the right;
5870 <li> the left operand has atomic, qualified, or unqualified pointer type, and (considering
5871 the type the left operand would have after lvalue conversion) both operands are
5872 pointers to qualified or unqualified versions of compatible types, and the type pointed
5873 to by the left has all the qualifiers of the type pointed to by the right;
5874 <li> the left operand has atomic, qualified, or unqualified pointer type, and (considering
5875 the type the left operand would have after lvalue conversion) one operand is a pointer
5876 to an object type, and the other is a pointer to a qualified or unqualified version of
5877 void, and the type pointed to by the left has all the qualifiers of the type pointed to
5878 by the right;
5879 <li> the left operand is an atomic, qualified, or unqualified pointer, and the right is a null
5880 pointer constant; or
5881 <li> the left operand has type atomic, qualified, or unqualified _Bool, and the right is a
5882 pointer.
5883 </ul>
5886 In simple assignment (=), the value of the right operand is converted to the type of the
5887 assignment expression and replaces the value stored in the object designated by the left
5888 operand.
5890 If the value being stored in an object is read from another object that overlaps in any way
5891 the storage of the first object, then the overlap shall be exact and the two objects shall
5892 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
5893 undefined.
5895 EXAMPLE 1 In the program fragment
5900 <!--page 121 -->
5901 <pre>
5902 int f(void);
5903 char c;
5904 /* ... */
5905 if ((c = f()) == -1)
5906 /* ... */
5907 </pre>
5908 the int value returned by the function may be truncated when stored in the char, and then converted back
5909 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
5910 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
5911 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
5912 variable c should be declared as int.
5915 EXAMPLE 2 In the fragment:
5916 <pre>
5917 char c;
5918 int i;
5919 long l;
5920 l = (c = i);
5921 </pre>
5922 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
5923 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
5924 that is, long int type.
5927 EXAMPLE 3 Consider the fragment:
5928 <pre>
5929 const char **cpp;
5930 char *p;
5931 const char c = 'A';
5932 cpp = &p; // constraint violation
5933 *cpp = &c; // valid
5934 *p = 0; // valid
5935 </pre>
5936 The first assignment is unsafe because it would allow the following valid code to attempt to change the
5937 value of the const object c.
5941 <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
5942 (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
5943 qualifiers that were applied to the type category of the expression (for example, it removes const but
5944 not volatile from the type int volatile * const).
5945 </small>
5951 For the operators += and -= only, either the left operand shall be an atomic, qualified, or
5952 unqualified pointer to a complete object type, and the right shall have integer type; or the
5953 left operand shall have atomic, qualified, or unqualified arithmetic type, and the right
5954 shall have arithmetic type.
5956 For the other operators, the left operand shall have atomic, qualified, or unqualified
5957 arithmetic type, and (considering the type the left operand would have after lvalue
5958 conversion) each operand shall have arithmetic type consistent with those allowed by the
5959 corresponding binary operator.
5962 A compound assignment of the form E1 op = E2 is equivalent to the simple assignment
5963 expression E1 = E1 op (E2), except that the lvalue E1 is evaluated only once, and with
5964 respect to an indeterminately-sequenced function call, the operation of a compound
5965 <!--page 122 -->
5966 assignment is a single evaluation. If E1 has an atomic type, compound assignment is a
5967 read-modify-write operation with memory_order_seq_cst memory order
5971 <p><small><a name="note113" href="#note113">113)</a> Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence
5972 where T is the type of E1:
5974 <pre>
5975 T tmp = E1;
5976 T result;
5977 do {
5978 result = tmp op (E2);
5980 </pre>
5981 with result being the result of the operation.
5982 </small>
5988 <pre>
5989 expression:
5990 assignment-expression
5991 expression , assignment-expression
5992 </pre>
5995 The left operand of a comma operator is evaluated as a void expression; there is a
5996 sequence point between its evaluation and that of the right operand. Then the right
5997 operand is evaluated; the result has its type and value.<sup><a href="#note114"><b>114)</b></a></sup> *
5999 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
6000 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
6001 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
6002 expression of a conditional operator in such contexts. In the function call
6003 <pre>
6005 </pre>
6006 the function has three arguments, the second of which has the value 5.
6013 <!--page 123 -->
6016 <p><small><a name="note114" href="#note114">114)</a> A comma operator does not yield an lvalue.
6017 </small>
6023 <pre>
6024 constant-expression:
6025 conditional-expression
6026 </pre>
6029 A constant expression can be evaluated during translation rather than runtime, and
6030 accordingly may be used in any place that a constant may be.
6033 Constant expressions shall not contain assignment, increment, decrement, function-call,
6034 or comma operators, except when they are contained within a subexpression that is not
6037 Each constant expression shall evaluate to a constant that is in the range of representable
6038 values for its type.
6041 An expression that evaluates to a constant is required in several contexts. If a floating
6042 expression is evaluated in the translation environment, the arithmetic precision and range
6043 shall be at least as great as if the expression were being evaluated in the execution
6046 An integer constant expression<sup><a href="#note117"><b>117)</b></a></sup> shall have integer type and shall only have operands
6047 that are integer constants, enumeration constants, character constants, sizeof
6048 expressions whose results are integer constants, and floating constants that are the
6049 immediate operands of casts. Cast operators in an integer constant expression shall only
6050 convert arithmetic types to integer types, except as part of an operand to the sizeof
6051 operator.
6053 More latitude is permitted for constant expressions in initializers. Such a constant
6054 expression shall be, or evaluate to, one of the following:
6055 <ul>
6056 <li> an arithmetic constant expression,
6060 <!--page 124 -->
6061 <li> a null pointer constant,
6062 <li> an address constant, or
6063 <li> an address constant for a complete object type plus or minus an integer constant
6064 expression.
6065 </ul>
6067 An arithmetic constant expression shall have arithmetic type and shall only have
6068 operands that are integer constants, floating constants, enumeration constants, character
6069 constants, and sizeof expressions. Cast operators in an arithmetic constant expression
6070 shall only convert arithmetic types to arithmetic types, except as part of an operand to a
6071 sizeof operator whose result is an integer constant.
6073 An address constant is a null pointer, a pointer to an lvalue designating an object of static
6074 storage duration, or a pointer to a function designator; it shall be created explicitly using
6075 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
6076 an expression of array or function type. The array-subscript [] and member-access .
6077 and -> operators, the address & and indirection * unary operators, and pointer casts may
6078 be used in the creation of an address constant, but the value of an object shall not be
6079 accessed by use of these operators.
6081 An implementation may accept other forms of constant expressions.
6083 The semantic rules for the evaluation of a constant expression are the same as for
6085 <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>).
6090 <!--page 125 -->
6093 <p><small><a name="note115" href="#note115">115)</a> The operand of a sizeof operator is usually not evaluated (<a href="#6.5.3.4">6.5.3.4</a>).
6094 </small>
6095 <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
6096 the translation environment.
6097 </small>
6098 <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
6099 member of a structure, the value of an enumeration constant, and the size of a non-variable length
6100 array. Further constraints that apply to the integer constant expressions used in conditional-inclusion
6102 </small>
6105 <pre>
6107 </pre>
6108 the expression is a valid integer constant expression with value one.
6109 </small>
6115 <pre>
6116 declaration:
6118 static_assert-declaration
6119 declaration-specifiers:
6125 init-declarator-list:
6126 init-declarator
6127 init-declarator-list , init-declarator
6128 init-declarator:
6129 declarator
6130 declarator = initializer
6131 </pre>
6134 A declaration other than a static_assert declaration shall declare at least a declarator
6135 (other than the parameters of a function or the members of a structure or union), a tag, or
6136 the members of an enumeration.
6138 If an identifier has no linkage, there shall be no more than one declaration of the identifier
6139 (in a declarator or type specifier) with the same scope and in the same name space, except
6140 that a typedef name can be redefined to denote the same type as it currently does and tags
6143 All declarations in the same scope that refer to the same object or function shall specify
6144 compatible types.
6147 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
6148 of an identifier is a declaration for that identifier that:
6149 <ul>
6150 <li> for an object, causes storage to be reserved for that object;
6155 <!--page 126 -->
6156 <li> for an enumeration constant or typedef name, is the (only) declaration of the
6157 identifier.
6158 </ul>
6160 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
6161 storage duration, and part of the type of the entities that the declarators denote. The init-
6162 declarator-list is a comma-separated sequence of declarators, each of which may have
6163 additional type information, or an initializer, or both. The declarators contain the
6164 identifiers (if any) being declared.
6166 If an identifier for an object is declared with no linkage, the type for the object shall be
6167 complete by the end of its declarator, or by the end of its init-declarator if it has an
6168 initializer; in the case of function parameters (including in prototypes), it is the adjusted
6170 <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
6171 (<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>).
6174 <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>.
6175 </small>
6181 <pre>
6182 storage-class-specifier:
6183 typedef
6184 extern
6185 static
6186 _Thread_local
6187 auto
6188 register
6189 </pre>
6192 At most, one storage-class specifier may be given in the declaration specifiers in a
6193 declaration, except that _Thread_local may appear with static or extern.<sup><a href="#note120"><b>120)</b></a></sup>
6195 In the declaration of an object with block scope, if the declaration specifiers include
6196 _Thread_local, they shall also include either static or extern. If
6197 _Thread_local appears in any declaration of an object, it shall be present in every
6198 declaration of that object.
6201 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
6202 only; it is discussed in <a href="#6.7.8">6.7.8</a>. The meanings of the various linkages and storage durations
6207 <!--page 127 -->
6209 A declaration of an identifier for an object with storage-class specifier register
6210 suggests that access to the object be as fast as possible. The extent to which such
6211 suggestions are effective is implementation-defined.<sup><a href="#note121"><b>121)</b></a></sup>
6213 The declaration of an identifier for a function that has block scope shall have no explicit
6214 storage-class specifier other than extern.
6216 If an aggregate or union object is declared with a storage-class specifier other than
6217 typedef, the properties resulting from the storage-class specifier, except with respect to
6218 linkage, also apply to the members of the object, and so on recursively for any aggregate
6219 or union member objects.
6223 <p><small><a name="note120" href="#note120">120)</a> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
6224 </small>
6225 <p><small><a name="note121" href="#note121">121)</a> The implementation may treat any register declaration simply as an auto declaration. However,
6226 whether or not addressable storage is actually used, the address of any part of an object declared with
6227 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
6228 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
6229 <a href="#6.3.2.1">6.3.2.1</a>). Thus, the only operator that can be applied to an array declared with storage-class specifier
6230 register is sizeof.
6231 </small>
6237 <pre>
6238 type-specifier:
6239 void
6240 char
6241 short
6242 int
6243 long
6244 float
6245 double
6246 signed
6247 unsigned
6248 _Bool
6249 _Complex
6250 atomic-type-specifier
6251 struct-or-union-specifier
6252 enum-specifier
6253 typedef-name
6254 </pre>
6257 At least one type specifier shall be given in the declaration specifiers in each declaration,
6258 and in the specifier-qualifier list in each struct declaration and type name. Each list of
6261 <!--page 128 -->
6262 type specifiers shall be one of the following multisets (delimited by commas, when there
6263 is more than one multiset per item); the type specifiers may occur in any order, possibly
6264 intermixed with the other declaration specifiers.
6265 <ul>
6266 <li> void
6267 <li> char
6268 <li> signed char
6269 <li> unsigned char
6270 <li> short, signed short, short int, or signed short int
6271 <li> unsigned short, or unsigned short int
6272 <li> int, signed, or signed int
6273 <li> unsigned, or unsigned int
6274 <li> long, signed long, long int, or signed long int
6275 <li> unsigned long, or unsigned long int
6276 <li> long long, signed long long, long long int, or
6277 signed long long int
6278 <li> unsigned long long, or unsigned long long int
6279 <li> float
6280 <li> double
6281 <li> long double
6282 <li> _Bool
6283 <li> float _Complex
6284 <li> double _Complex
6285 <li> long double _Complex
6286 <li> atomic type specifier
6287 <li> struct or union specifier
6288 <li> enum specifier
6289 <li> typedef name
6290 </ul>
6292 The type specifier _Complex shall not be used if the implementation does not support
6294 <!--page 129 -->
6297 Specifiers for structures, unions, enumerations, and atomic types are discussed in <a href="#6.7.2.1">6.7.2.1</a>
6298 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
6301 Each of the comma-separated multisets designates the same type, except that for bit-
6302 fields, it is implementation-defined whether the specifier int designates the same type as
6303 signed int or the same type as unsigned int.
6304 <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>),
6305 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>).
6311 <pre>
6312 struct-or-union-specifier:
6314 struct-or-union identifier
6315 struct-or-union:
6316 struct
6317 union
6318 struct-declaration-list:
6319 struct-declaration
6320 struct-declaration-list struct-declaration
6321 struct-declaration:
6323 static_assert-declaration
6324 specifier-qualifier-list:
6327 struct-declarator-list:
6328 struct-declarator
6329 struct-declarator-list , struct-declarator
6330 struct-declarator:
6331 declarator
6333 </pre>
6336 A struct-declaration that does not declare an anonymous structure or anonymous union
6337 shall contain a struct-declarator-list.
6338 <!--page 130 -->
6340 A structure or union shall not contain a member with incomplete or function type (hence,
6341 a structure shall not contain an instance of itself, but may contain a pointer to an instance
6342 of itself), except that the last member of a structure with more than one named member
6343 may have incomplete array type; such a structure (and any union containing, possibly
6344 recursively, a member that is such a structure) shall not be a member of a structure or an
6345 element of an array.
6347 The expression that specifies the width of a bit-field shall be an integer constant
6348 expression with a nonnegative value that does not exceed the width of an object of the
6349 type that would be specified were the colon and expression omitted.<sup><a href="#note122"><b>122)</b></a></sup> If the value is
6350 zero, the declaration shall have no declarator.
6352 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
6353 int, unsigned int, or some other implementation-defined type. It is
6354 implementation-defined whether atomic types are permitted.
6357 As discussed in <a href="#6.2.5">6.2.5</a>, a structure is a type consisting of a sequence of members, whose
6358 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
6359 of members whose storage overlap.
6361 Structure and union specifiers have the same form. The keywords struct and union
6362 indicate that the type being specified is, respectively, a structure type or a union type.
6364 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
6365 within a translation unit. The struct-declaration-list is a sequence of declarations for the
6366 members of the structure or union. If the struct-declaration-list contains no named
6367 members, no anonymous structures, and no anonymous unions, the behavior is undefined.
6368 The type is incomplete until immediately after the } that terminates the list, and complete
6369 thereafter.
6371 A member of a structure or union may have any complete object type other than a
6372 variably modified type.<sup><a href="#note123"><b>123)</b></a></sup> In addition, a member may be declared to consist of a
6373 specified number of bits (including a sign bit, if any). Such a member is called a
6376 A bit-field is interpreted as having a signed or unsigned integer type consisting of the
6377 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
6379 <!--page 131 -->
6380 type _Bool, the value of the bit-field shall compare equal to the value stored; a _Bool
6381 bit-field has the semantics of a _Bool.
6383 An implementation may allocate any addressable storage unit large enough to hold a bit-
6384 field. If enough space remains, a bit-field that immediately follows another bit-field in a
6385 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
6386 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
6387 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
6388 low-order or low-order to high-order) is implementation-defined. The alignment of the
6389 addressable storage unit is unspecified.
6391 A bit-field declaration with no declarator, but only a colon and a width, indicates an
6392 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
6393 indicates that no further bit-field is to be packed into the unit in which the previous bit-
6394 field, if any, was placed.
6396 An unnamed member of structure type with no tag is called an anonymous structure; an
6397 unnamed member of union type with no tag is called an anonymous union. The members
6398 of an anonymous structure or union are considered to be members of the containing
6399 structure or union. This applies recursively if the containing structure or union is also
6400 anonymous.
6402 Each non-bit-field member of a structure or union object is aligned in an implementation-
6403 defined manner appropriate to its type.
6405 Within a structure object, the non-bit-field members and the units in which bit-fields
6406 reside have addresses that increase in the order in which they are declared. A pointer to a
6407 structure object, suitably converted, points to its initial member (or if that member is a
6408 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
6409 padding within a structure object, but not at its beginning.
6411 The size of a union is sufficient to contain the largest of its members. The value of at
6412 most one of the members can be stored in a union object at any time. A pointer to a
6413 union object, suitably converted, points to each of its members (or if a member is a bit-
6414 field, then to the unit in which it resides), and vice versa.
6416 There may be unnamed padding at the end of a structure or union.
6418 As a special case, the last element of a structure with more than one named member may
6419 have an incomplete array type; this is called a flexible array member. In most situations,
6422 <!--page 132 -->
6423 the flexible array member is ignored. In particular, the size of the structure is as if the
6424 flexible array member were omitted except that it may have more trailing padding than
6425 the omission would imply. However, when a . (or ->) operator has a left operand that is
6426 (a pointer to) a structure with a flexible array member and the right operand names that
6427 member, it behaves as if that member were replaced with the longest array (with the same
6428 element type) that would not make the structure larger than the object being accessed; the
6429 offset of the array shall remain that of the flexible array member, even if this would differ
6430 from that of the replacement array. If this array would have no elements, it behaves as if
6431 it had one element but the behavior is undefined if any attempt is made to access that
6432 element or to generate a pointer one past it.
6434 EXAMPLE 1 The following illustrates anonymous structures and unions:
6435 <pre>
6436 struct v {
6437 union { // anonymous union
6438 struct { int i, j; }; // anonymous structure
6439 struct { long k, l; } w;
6440 };
6441 int m;
6442 } v1;
6443 v1.i = 2; // valid
6444 v1.k = 3; // invalid: inner structure is not anonymous
6445 v1.w.k = 5; // valid
6446 </pre>
6449 EXAMPLE 2 After the declaration:
6450 <pre>
6451 struct s { int n; double d[]; };
6452 </pre>
6453 the structure struct s has a flexible array member d. A typical way to use this is:
6454 <pre>
6455 int m = /* some value */;
6456 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
6457 </pre>
6458 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
6459 p had been declared as:
6460 <pre>
6461 struct { int n; double d[m]; } *p;
6462 </pre>
6463 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
6464 not be the same).
6466 Following the above declaration:
6467 <pre>
6468 struct s t1 = { 0 }; // valid
6470 t1.n = 4; // valid
6472 </pre>
6473 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
6474 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
6475 <pre>
6476 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)
6477 </pre>
6478 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
6479 code.
6480 <!--page 133 -->
6482 After the further declaration:
6483 <pre>
6484 struct ss { int n; };
6485 </pre>
6486 the expressions:
6487 <pre>
6488 sizeof (struct s) >= sizeof (struct ss)
6489 sizeof (struct s) >= offsetof(struct s, d)
6490 </pre>
6491 are always equal to 1.
6493 If sizeof (double) is 8, then after the following code is executed:
6494 <pre>
6495 struct s *s1;
6496 struct s *s2;
6497 s1 = malloc(sizeof (struct s) + 64);
6498 s2 = malloc(sizeof (struct s) + 46);
6499 </pre>
6500 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
6501 purposes, as if the identifiers had been declared as:
6502 <pre>
6503 struct { int n; double d[8]; } *s1;
6504 struct { int n; double d[5]; } *s2;
6505 </pre>
6507 Following the further successful assignments:
6508 <pre>
6509 s1 = malloc(sizeof (struct s) + 10);
6510 s2 = malloc(sizeof (struct s) + 6);
6511 </pre>
6512 they then behave as if the declarations were:
6513 <pre>
6514 struct { int n; double d[1]; } *s1, *s2;
6515 </pre>
6516 and:
6517 <pre>
6518 double *dp;
6520 *dp = 42; // valid
6522 *dp = 42; // undefined behavior
6523 </pre>
6525 The assignment:
6526 <pre>
6527 *s1 = *s2;
6528 </pre>
6529 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
6530 of the structure, they might be copied or simply overwritten with indeterminate values.
6532 <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>).
6533 <!--page 134 -->
6536 <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
6537 value bits) of a _Bool may be just 1 bit.
6538 </small>
6539 <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
6541 </small>
6542 <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
6543 or arrays of bit-field objects.
6544 </small>
6545 <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,
6546 then it is implementation-defined whether the bit-field is signed or unsigned.
6547 </small>
6548 <p><small><a name="note126" href="#note126">126)</a> An unnamed bit-field structure member is useful for padding to conform to externally imposed
6549 layouts.
6550 </small>
6556 <pre>
6557 enum-specifier:
6560 enum identifier
6561 enumerator-list:
6562 enumerator
6563 enumerator-list , enumerator
6564 enumerator:
6565 enumeration-constant
6566 enumeration-constant = constant-expression
6567 </pre>
6570 The expression that defines the value of an enumeration constant shall be an integer
6571 constant expression that has a value representable as an int.
6574 The identifiers in an enumerator list are declared as constants that have type int and
6575 may appear wherever such are permitted.<sup><a href="#note127"><b>127)</b></a></sup> An enumerator with = defines its
6576 enumeration constant as the value of the constant expression. If the first enumerator has
6577 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
6578 defines its enumeration constant as the value of the constant expression obtained by
6579 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
6580 = may produce enumeration constants with values that duplicate other values in the same
6581 enumeration.) The enumerators of an enumeration are also known as its members.
6583 Each enumerated type shall be compatible with char, a signed integer type, or an
6584 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note128"><b>128)</b></a></sup> but shall be
6585 capable of representing the values of all the members of the enumeration. The
6586 enumerated type is incomplete until immediately after the } that terminates the list of
6587 enumerator declarations, and complete thereafter.
6592 <!--page 135 -->
6594 EXAMPLE The following fragment:
6595 <pre>
6596 enum hue { chartreuse, burgundy, claret=20, winedark };
6597 enum hue col, *cp;
6598 col = claret;
6599 cp = &col;
6600 if (*cp != burgundy)
6601 /* ... */
6602 </pre>
6603 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
6604 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
6609 <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
6610 each other and from other identifiers declared in ordinary declarators.
6611 </small>
6612 <p><small><a name="note128" href="#note128">128)</a> An implementation may delay the choice of which integer type until all enumeration constants have
6613 been seen.
6614 </small>
6620 A specific type shall have its content defined at most once.
6622 Where two declarations that use the same tag declare the same type, they shall both use
6623 the same choice of struct, union, or enum.
6625 A type specifier of the form
6626 <pre>
6627 enum identifier
6628 </pre>
6629 without an enumerator list shall only appear after the type it specifies is complete.
6632 All declarations of structure, union, or enumerated types that have the same scope and
6633 use the same tag declare the same type. Irrespective of whether there is a tag or what
6634 other declarations of the type are in the same translation unit, the type is incomplete<sup><a href="#note129"><b>129)</b></a></sup>
6635 until immediately after the closing brace of the list defining the content, and complete
6636 thereafter.
6638 Two declarations of structure, union, or enumerated types which are in different scopes or
6639 use different tags declare distinct types. Each declaration of a structure, union, or
6640 enumerated type which does not include a tag declares a distinct type.
6642 A type specifier of the form
6647 <!--page 136 -->
6648 <pre>
6650 </pre>
6651 or
6652 <pre>
6654 </pre>
6655 or
6656 <pre>
6658 </pre>
6659 declares a structure, union, or enumerated type. The list defines the structure content,
6660 union content, or enumeration content. If an identifier is provided,<sup><a href="#note130"><b>130)</b></a></sup> the type specifier
6661 also declares the identifier to be the tag of that type.
6663 A declaration of the form
6664 <pre>
6665 struct-or-union identifier ;
6666 </pre>
6667 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>
6669 If a type specifier of the form
6670 <pre>
6671 struct-or-union identifier
6672 </pre>
6673 occurs other than as part of one of the above forms, and no other declaration of the
6674 identifier as a tag is visible, then it declares an incomplete structure or union type, and
6677 If a type specifier of the form
6678 <pre>
6679 struct-or-union identifier
6680 </pre>
6681 or
6682 <pre>
6683 enum identifier
6684 </pre>
6685 occurs other than as part of one of the above forms, and a declaration of the identifier as a
6686 tag is visible, then it specifies the same type as that other declaration, and does not
6687 redeclare the tag.
6689 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
6690 <pre>
6691 struct tnode {
6692 int count;
6693 struct tnode *left, *right;
6694 };
6695 </pre>
6696 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
6697 declaration has been given, the declaration
6702 <!--page 137 -->
6703 <pre>
6704 struct tnode s, *sp;
6705 </pre>
6706 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
6707 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
6708 which sp points; the expression s.right->count designates the count member of the right struct
6709 tnode pointed to from s.
6711 The following alternative formulation uses the typedef mechanism:
6712 <pre>
6713 typedef struct tnode TNODE;
6714 struct tnode {
6715 int count;
6716 TNODE *left, *right;
6717 };
6718 TNODE s, *sp;
6719 </pre>
6722 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
6723 structures, the declarations
6724 <pre>
6725 struct s1 { struct s2 *s2p; /* ... */ }; // D1
6726 struct s2 { struct s1 *s1p; /* ... */ }; // D2
6727 </pre>
6728 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
6729 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
6730 D2. To eliminate this context sensitivity, the declaration
6731 <pre>
6732 struct s2;
6733 </pre>
6734 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
6735 completes the specification of the new type.
6737 <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>).
6740 <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
6741 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
6742 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
6743 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
6744 </small>
6745 <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
6746 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
6747 can make use of that typedef name to declare objects having the specified structure, union, or
6748 enumerated type.
6749 </small>
6750 <p><small><a name="note131" href="#note131">131)</a> A similar construction with enum does not exist.
6751 </small>
6757 <pre>
6758 atomic-type-specifier:
6759 _Atomic ( type-name )
6760 </pre>
6763 Atomic type specifiers shall not be used if the implementation does not support atomic
6766 The type name in an atomic type specifier shall not refer to an array type, a function type,
6767 an atomic type, or a qualified type.
6770 The properties associated with atomic types are meaningful only for expressions that are
6771 lvalues. If the _Atomic keyword is immediately followed by a left parenthesis, it is
6772 interpreted as a type specifier (with a type name), not as a type qualifier.
6773 <!--page 138 -->
6779 <pre>
6780 type-qualifier:
6781 const
6782 restrict
6783 volatile
6784 _Atomic
6785 </pre>
6788 Types other than pointer types whose referenced type is an object type shall not be
6789 restrict-qualified.
6791 The type modified by the _Atomic qualifier shall not be an array type or a function
6792 type.
6795 The properties associated with qualified types are meaningful only for expressions that
6798 If the same qualifier appears more than once in the same specifier-qualifier-list, either
6799 directly or via one or more typedefs, the behavior is the same as if it appeared only
6800 once. If other qualifiers appear along with the _Atomic qualifier in a specifier-qualifier-
6801 list, the resulting type is the so-qualified atomic type.
6803 If an attempt is made to modify an object defined with a const-qualified type through use
6804 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
6805 made to refer to an object defined with a volatile-qualified type through use of an lvalue
6806 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note133"><b>133)</b></a></sup>
6808 An object that has volatile-qualified type may be modified in ways unknown to the
6809 implementation or have other unknown side effects. Therefore any expression referring
6810 to such an object shall be evaluated strictly according to the rules of the abstract machine,
6811 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
6812 object shall agree with that prescribed by the abstract machine, except as modified by the
6817 <!--page 139 -->
6818 unknown factors mentioned previously.<sup><a href="#note134"><b>134)</b></a></sup> What constitutes an access to an object that
6819 has volatile-qualified type is implementation-defined.
6821 An object that is accessed through a restrict-qualified pointer has a special association
6822 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
6823 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note135"><b>135)</b></a></sup> The intended
6824 use of the restrict qualifier (like the register storage class) is to promote
6825 optimization, and deleting all instances of the qualifier from all preprocessing translation
6826 units composing a conforming program does not change its meaning (i.e., observable
6827 behavior).
6829 If the specification of an array type includes any type qualifiers, the element type is so-
6830 qualified, not the array type. If the specification of a function type includes any type
6833 For two qualified types to be compatible, both shall have the identically qualified version
6834 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
6835 does not affect the specified type.
6837 EXAMPLE 1 An object declared
6838 <pre>
6839 extern const volatile int real_time_clock;
6840 </pre>
6841 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
6844 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
6845 modify an aggregate type:
6846 <pre>
6847 const struct s { int mem; } cs = { 1 };
6848 struct s ncs; // the object ncs is modifiable
6851 int *pi;
6852 const int *pci;
6853 ncs = cs; // valid
6854 cs = ncs; // violates modifiable lvalue constraint for =
6855 pi = &ncs.mem; // valid
6856 pi = &cs.mem; // violates type constraints for =
6857 pci = &cs.mem; // valid
6859 </pre>
6863 <!--page 140 -->
6865 EXAMPLE 3 The declaration
6866 <pre>
6867 _Atomic volatile int *p;
6868 </pre>
6869 specifies that p has the type ''pointer to volatile atomic int'', a pointer to a volatile-qualified atomic type.
6873 <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
6874 storage. Moreover, the implementation need not allocate storage for such an object if its address is
6875 never used.
6876 </small>
6877 <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
6878 never actually defined as objects in the program (such as an object at a memory-mapped input/output
6879 address).
6880 </small>
6881 <p><small><a name="note134" href="#note134">134)</a> A volatile declaration may be used to describe an object corresponding to a memory-mapped
6882 input/output port or an object accessed by an asynchronously interrupting function. Actions on
6883 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
6884 permitted by the rules for evaluating expressions.
6885 </small>
6886 <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
6887 association between the allocated object and the pointer.
6888 </small>
6889 <p><small><a name="note136" href="#note136">136)</a> Both of these can occur through the use of typedefs.
6890 </small>
6895 Let D be a declaration of an ordinary identifier that provides a means of designating an
6896 object P as a restrict-qualified pointer to type T.
6898 If D appears inside a block and does not have storage class extern, let B denote the
6899 block. If D appears in the list of parameter declarations of a function definition, let B
6900 denote the associated block. Otherwise, let B denote the block of main (or the block of
6901 whatever function is called at program startup in a freestanding environment).
6903 In what follows, a pointer expression E is said to be based on object P if (at some
6904 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
6905 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>
6906 Note that ''based'' is defined only for expressions with pointer types.
6908 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
6909 access the value of the object X that it designates, and X is also modified (by any means),
6910 then the following requirements apply: T shall not be const-qualified. Every other lvalue
6911 used to access the value of X shall also have its address based on P. Every access that
6912 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
6913 is assigned the value of a pointer expression E that is based on another restricted pointer
6914 object P2, associated with block B2, then either the execution of B2 shall begin before
6915 the execution of B, or the execution of B2 shall end prior to the assignment. If these
6916 requirements are not met, then the behavior is undefined.
6918 Here an execution of B means that portion of the execution of the program that would
6919 correspond to the lifetime of an object with scalar type and automatic storage duration
6920 associated with B.
6922 A translator is free to ignore any or all aliasing implications of uses of restrict.
6924 EXAMPLE 1 The file scope declarations
6925 <pre>
6926 int * restrict a;
6927 int * restrict b;
6928 extern int c[];
6929 </pre>
6930 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
6931 program, then it is never accessed using either of the other two.
6934 <!--page 141 -->
6936 EXAMPLE 2 The function parameter declarations in the following example
6937 <pre>
6938 void f(int n, int * restrict p, int * restrict q)
6939 {
6941 *p++ = *q++;
6942 }
6943 </pre>
6944 assert that, during each execution of the function, if an object is accessed through one of the pointer
6945 parameters, then it is not also accessed through the other.
6947 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
6948 analysis of function f without examining any of the calls of f in the program. The cost is that the
6949 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
6950 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
6951 both p and q.
6952 <pre>
6953 void g(void)
6954 {
6955 extern int d[100];
6958 }
6959 </pre>
6962 EXAMPLE 3 The function parameter declarations
6963 <pre>
6964 void h(int n, int * restrict p, int * restrict q, int * restrict r)
6965 {
6966 int i;
6968 p[i] = q[i] + r[i];
6969 }
6970 </pre>
6971 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
6972 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
6973 modified within function h.
6976 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
6977 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
6978 between restricted pointers declared in nested blocks have defined behavior.
6979 <!--page 142 -->
6980 <pre>
6981 {
6982 int * restrict p1;
6983 int * restrict q1;
6984 p1 = q1; // undefined behavior
6985 {
6986 int * restrict p2 = p1; // valid
6987 int * restrict q2 = q1; // valid
6988 p1 = q2; // undefined behavior
6989 p2 = q2; // undefined behavior
6990 }
6991 }
6992 </pre>
6994 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
6995 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
6996 example, this permits new_vector to return a vector.
6997 <pre>
6998 typedef struct { int n; float * restrict v; } vector;
6999 vector new_vector(int n)
7000 {
7001 vector t;
7002 t.n = n;
7003 t.v = malloc(n * sizeof (float));
7004 return t;
7005 }
7006 </pre>
7010 <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
7011 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
7012 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
7013 expressions *p and p[1] are not.
7014 </small>
7020 <pre>
7021 function-specifier:
7022 inline
7023 _Noreturn
7024 </pre>
7027 Function specifiers shall be used only in the declaration of an identifier for a function.
7029 An inline definition of a function with external linkage shall not contain a definition of a
7030 modifiable object with static or thread storage duration, and shall not contain a reference
7031 to an identifier with internal linkage.
7033 In a hosted environment, no function specifier(s) shall appear in a declaration of main.
7036 A function specifier may appear more than once; the behavior is the same as if it
7037 appeared only once.
7039 A function declared with an inline function specifier is an inline function. Making a *
7040 function an inline function suggests that calls to the function be as fast as possible.<sup><a href="#note138"><b>138)</b></a></sup>
7041 The extent to which such suggestions are effective is implementation-defined.<sup><a href="#note139"><b>139)</b></a></sup>
7046 <!--page 143 -->
7048 Any function with internal linkage can be an inline function. For a function with external
7049 linkage, the following restrictions apply: If a function is declared with an inline
7050 function specifier, then it shall also be defined in the same translation unit. If all of the
7051 file scope declarations for a function in a translation unit include the inline function
7052 specifier without extern, then the definition in that translation unit is an inline
7053 definition. An inline definition does not provide an external definition for the function,
7054 and does not forbid an external definition in another translation unit. An inline definition
7055 provides an alternative to an external definition, which a translator may use to implement
7056 any call to the function in the same translation unit. It is unspecified whether a call to the
7057 function uses the inline definition or the external definition.<sup><a href="#note140"><b>140)</b></a></sup>
7059 A function declared with a _Noreturn function specifier shall not return to its caller.
7062 The implementation should produce a diagnostic message for a function declared with a
7063 _Noreturn function specifier that appears to be capable of returning to its caller.
7065 EXAMPLE 1 The declaration of an inline function with external linkage can result in either an external
7066 definition, or a definition available for use only within the translation unit. A file scope declaration with
7067 extern creates an external definition. The following example shows an entire translation unit.
7068 <pre>
7069 inline double fahr(double t)
7070 {
7072 }
7073 inline double cels(double t)
7074 {
7076 }
7077 extern double fahr(double); // creates an external definition
7078 double convert(int is_fahr, double temp)
7079 {
7080 /* A translator may perform inline substitutions */
7081 return is_fahr ? cels(temp) : fahr(temp);
7082 }
7083 </pre>
7085 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
7086 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
7087 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
7088 definition are distinct and either may be used for the call.
7091 EXAMPLE 2
7096 <!--page 144 -->
7097 <pre>
7098 _Noreturn void f () {
7099 abort(); // ok
7100 }
7103 }
7104 </pre>
7109 <p><small><a name="note138" href="#note138">138)</a> By using, for example, an alternative to the usual function call mechanism, such as ''inline
7110 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
7111 Therefore, for example, the expansion of a macro used within the body of the function uses the
7112 definition it had at the point the function body appears, and not where the function is called; and
7113 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
7114 single address, regardless of the number of inline definitions that occur in addition to the external
7115 definition.
7116 </small>
7117 <p><small><a name="note139" href="#note139">139)</a> For example, an implementation might never perform inline substitution, or might only perform inline
7118 substitutions to calls in the scope of an inline declaration.
7119 </small>
7120 <p><small><a name="note140" href="#note140">140)</a> Since an inline definition is distinct from the corresponding external definition and from any other
7121 corresponding inline definitions in other translation units, all corresponding objects with static storage
7122 duration are also distinct in each of the definitions.
7123 </small>
7129 <pre>
7130 alignment-specifier:
7131 _Alignas ( type-name )
7132 _Alignas ( constant-expression )
7133 </pre>
7136 An alignment attribute shall not be specified in a declaration of a typedef, or a bit-field, or
7137 a function, or a parameter, or an object declared with the register storage-class
7138 specifier.
7140 The constant expression shall be an integer constant expression. It shall evaluate to a
7141 valid fundamental alignment, or to a valid extended alignment supported by the
7142 implementation in the context in which it appears, or to zero.
7144 The combined effect of all alignment attributes in a declaration shall not specify an
7145 alignment that is less strict than the alignment that would otherwise be required for the
7146 type of the object or member being declared.
7149 The first form is equivalent to _Alignas(alignof(type-name)).
7151 The alignment requirement of the declared object or member is taken to be the specified
7152 alignment. An alignment specification of zero has no effect.<sup><a href="#note141"><b>141)</b></a></sup> When multiple
7153 alignment specifiers occur in a declaration, the effective alignment requirement is the
7154 strictest specified alignment.
7156 If the definition of an object has an alignment specifier, any other declaration of that
7157 object shall either specify equivalent alignment or have no alignment specifier. If the
7158 definition of an object does not have an alignment specifier, any other declaration of that
7159 object shall also have no alignment specifier. If declarations of an object in different
7160 translation units have different alignment specifiers, the behavior is undefined.
7164 <!--page 145 -->
7167 <p><small><a name="note141" href="#note141">141)</a> An alignment specification of zero also does not affect other alignment specifications in the same
7168 declaration.
7169 </small>
7175 <pre>
7176 declarator:
7178 direct-declarator:
7179 identifier
7180 ( declarator )
7183 direct-declarator [ type-qualifier-list static assignment-expression ]
7185 direct-declarator ( parameter-type-list )
7187 pointer:
7190 type-qualifier-list:
7191 type-qualifier
7192 type-qualifier-list type-qualifier
7193 parameter-type-list:
7194 parameter-list
7195 parameter-list , ...
7196 parameter-list:
7197 parameter-declaration
7198 parameter-list , parameter-declaration
7199 parameter-declaration:
7200 declaration-specifiers declarator
7202 identifier-list:
7203 identifier
7204 identifier-list , identifier
7205 </pre>
7208 Each declarator declares one identifier, and asserts that when an operand of the same
7209 form as the declarator appears in an expression, it designates a function or object with the
7210 scope, storage duration, and type indicated by the declaration specifiers.
7212 A full declarator is a declarator that is not part of another declarator. The end of a full
7213 declarator is a sequence point. If, in the nested sequence of declarators in a full
7214 <!--page 146 -->
7215 declarator, there is a declarator specifying a variable length array type, the type specified
7216 by the full declarator is said to be variably modified. Furthermore, any type derived by
7217 declarator type derivation from a variably modified type is itself variably modified.
7219 In the following subclauses, consider a declaration
7220 <pre>
7221 T D1
7222 </pre>
7223 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
7224 a declarator that contains an identifier ident. The type specified for the identifier ident in
7225 the various forms of declarator is described inductively using this notation.
7227 If, in the declaration ''T D1'', D1 has the form
7228 <pre>
7229 identifier
7230 </pre>
7231 then the type specified for ident is T .
7233 If, in the declaration ''T D1'', D1 has the form
7234 <pre>
7235 ( D )
7236 </pre>
7237 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
7238 parentheses is identical to the unparenthesized declarator, but the binding of complicated
7239 declarators may be altered by parentheses.
7242 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of pointer, array, and
7243 function declarators that modify an arithmetic, structure, union, or void type, either
7244 directly or via one or more typedefs.
7245 <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>).
7251 If, in the declaration ''T D1'', D1 has the form
7252 <pre>
7254 </pre>
7255 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7256 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
7257 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
7259 For two pointer types to be compatible, both shall be identically qualified and both shall
7260 be pointers to compatible types.
7262 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
7263 to a constant value'' and a ''constant pointer to a variable value''.
7264 <!--page 147 -->
7265 <pre>
7266 const int *ptr_to_constant;
7267 int *const constant_ptr;
7268 </pre>
7269 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
7270 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
7271 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
7272 same location.
7274 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
7275 type ''pointer to int''.
7276 <pre>
7277 typedef int *int_ptr;
7278 const int_ptr constant_ptr;
7279 </pre>
7280 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
7287 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
7288 an expression or *. If they delimit an expression (which specifies the size of an array), the
7289 expression shall have an integer type. If the expression is a constant expression, it shall
7290 have a value greater than zero. The element type shall not be an incomplete or function
7291 type. The optional type qualifiers and the keyword static shall appear only in a
7292 declaration of a function parameter with an array type, and then only in the outermost
7293 array type derivation.
7295 If an identifier is declared as having a variably modified type, it shall be an ordinary
7296 identifier (as defined in <a href="#6.2.3">6.2.3</a>), have no linkage, and have either block scope or function
7297 prototype scope. If an identifier is declared to be an object with static or thread storage
7298 duration, it shall not have a variable length array type.
7301 If, in the declaration ''T D1'', D1 has one of the forms:
7302 <pre>
7305 D[ type-qualifier-list static assignment-expression ]
7307 </pre>
7308 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7309 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note142"><b>142)</b></a></sup>
7310 (See <a href="#6.7.6.3">6.7.6.3</a> for the meaning of the optional type qualifiers and the keyword static.)
7312 If the size is not present, the array type is an incomplete type. If the size is * instead of
7313 being an expression, the array type is a variable length array type of unspecified size,
7314 which can only be used in declarations or type names with function prototype scope;<sup><a href="#note143"><b>143)</b></a></sup>
7316 <!--page 148 -->
7317 such arrays are nonetheless complete types. If the size is an integer constant expression
7318 and the element type has a known constant size, the array type is not a variable length
7319 array type; otherwise, the array type is a variable length array type. (Variable length
7320 arrays are a conditional feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.)
7322 If the size is an expression that is not an integer constant expression: if it occurs in a
7323 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
7324 each time it is evaluated it shall have a value greater than zero. The size of each instance
7325 of a variable length array type does not change during its lifetime. Where a size
7326 expression is part of the operand of a sizeof operator and changing the value of the
7327 size expression would not affect the result of the operator, it is unspecified whether or not
7328 the size expression is evaluated.
7330 For two array types to be compatible, both shall have compatible element types, and if
7331 both size specifiers are present, and are integer constant expressions, then both size
7332 specifiers shall have the same constant value. If the two array types are used in a context
7333 which requires them to be compatible, it is undefined behavior if the two size specifiers
7334 evaluate to unequal values.
7336 EXAMPLE 1
7337 <pre>
7339 </pre>
7340 declares an array of float numbers and an array of pointers to float numbers.
7343 EXAMPLE 2 Note the distinction between the declarations
7344 <pre>
7345 extern int *x;
7346 extern int y[];
7347 </pre>
7348 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
7349 (an incomplete type), the storage for which is defined elsewhere.
7352 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
7353 <pre>
7354 extern int n;
7355 extern int m;
7356 void fcompat(void)
7357 {
7358 int a[n][6][m];
7360 int c[n][n][6][m];
7361 int (*r)[n][n][n+1];
7363 r = c; // compatible, but defined behavior only if
7365 }
7366 </pre>
7371 <!--page 149 -->
7373 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
7374 function prototype scope. Array objects declared with the _Thread_local, static, or extern
7375 storage-class specifier cannot have a variable length array (VLA) type. However, an object declared with
7376 the static storage-class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all
7377 identifiers declared with a VM type have to be ordinary identifiers and cannot, therefore, be members of
7378 structures or unions.
7379 <pre>
7380 extern int n;
7381 int A[n]; // invalid: file scope VLA
7382 extern int (*p2)[n]; // invalid: file scope VM
7383 int B[100]; // valid: file scope but not VM
7384 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
7385 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
7386 {
7387 typedef int VLA[m][m]; // valid: block scope typedef VLA
7388 struct tag {
7389 int (*y)[n]; // invalid: y not ordinary identifier
7390 int z[n]; // invalid: z not ordinary identifier
7391 };
7392 int D[m]; // valid: auto VLA
7393 static int E[m]; // invalid: static block scope VLA
7394 extern int F[m]; // invalid: F has linkage and is VLA
7395 int (*s)[m]; // valid: auto pointer to VLA
7396 extern int (*r)[m]; // invalid: r has linkage and points to VLA
7397 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
7398 }
7399 </pre>
7401 <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>),
7405 <p><small><a name="note142" href="#note142">142)</a> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
7406 </small>
7407 <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>).
7408 </small>
7411 <h5><a name="6.7.6.3" href="#6.7.6.3">6.7.6.3 Function declarators (including prototypes)</a></h5>
7414 A function declarator shall not specify a return type that is a function type or an array
7415 type.
7417 The only storage-class specifier that shall occur in a parameter declaration is register.
7419 An identifier list in a function declarator that is not part of a definition of that function
7420 shall be empty.
7422 After adjustment, the parameters in a parameter type list in a function declarator that is
7423 part of a definition of that function shall not have incomplete type.
7426 If, in the declaration ''T D1'', D1 has the form
7427 <!--page 150 -->
7428 <pre>
7429 D( parameter-type-list )
7430 </pre>
7431 or
7432 <pre>
7434 </pre>
7435 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7436 T '', then the type specified for ident is ''derived-declarator-type-list function returning
7437 T ''.
7439 A parameter type list specifies the types of, and may declare identifiers for, the
7440 parameters of the function.
7442 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
7443 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
7444 array type derivation. If the keyword static also appears within the [ and ] of the
7445 array type derivation, then for each call to the function, the value of the corresponding
7446 actual argument shall provide access to the first element of an array with at least as many
7447 elements as specified by the size expression.
7449 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
7452 If the list terminates with an ellipsis (, ...), no information about the number or types
7455 The special case of an unnamed parameter of type void as the only item in the list
7456 specifies that the function has no parameters.
7458 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
7459 parameter name, it shall be taken as a typedef name.
7461 If the function declarator is not part of a definition of that function, parameters may have
7462 incomplete type and may use the [*] notation in their sequences of declarator specifiers
7463 to specify variable length array types.
7465 The storage-class specifier in the declaration specifiers for a parameter declaration, if
7466 present, is ignored unless the declared parameter is one of the members of the parameter
7467 type list for a function definition.
7469 An identifier list declares only the identifiers of the parameters of the function. An empty
7470 list in a function declarator that is part of a definition of that function specifies that the
7471 function has no parameters. The empty list in a function declarator that is not part of a
7472 definition of that function specifies that no information about the number or types of the
7477 <!--page 151 -->
7479 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note146"><b>146)</b></a></sup>
7480 Moreover, the parameter type lists, if both are present, shall agree in the number of
7481 parameters and in use of the ellipsis terminator; corresponding parameters shall have
7482 compatible types. If one type has a parameter type list and the other type is specified by a
7483 function declarator that is not part of a function definition and that contains an empty
7484 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
7485 parameter shall be compatible with the type that results from the application of the
7486 default argument promotions. If one type has a parameter type list and the other type is
7487 specified by a function definition that contains a (possibly empty) identifier list, both shall
7488 agree in the number of parameters, and the type of each prototype parameter shall be
7489 compatible with the type that results from the application of the default argument
7490 promotions to the type of the corresponding identifier. (In the determination of type
7491 compatibility and of a composite type, each parameter declared with function or array
7492 type is taken as having the adjusted type and each parameter declared with qualified type
7493 is taken as having the unqualified version of its declared type.)
7495 EXAMPLE 1 The declaration
7496 <pre>
7497 int f(void), *fip(), (*pfi)();
7498 </pre>
7499 declares a function f with no parameters returning an int, a function fip with no parameter specification
7500 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
7501 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
7502 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
7503 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
7504 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
7505 designator, which is then used to call the function; it returns an int.
7507 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
7508 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
7509 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
7510 the identifier of the pointer pfi has block scope and no linkage.
7513 EXAMPLE 2 The declaration
7514 <pre>
7515 int (*apfi[3])(int *x, int *y);
7516 </pre>
7517 declares an array apfi of three pointers to functions returning int. Each of these functions has two
7518 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
7519 go out of scope at the end of the declaration of apfi.
7522 EXAMPLE 3 The declaration
7523 <pre>
7524 int (*fpfi(int (*)(long), int))(int, ...);
7525 </pre>
7526 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
7527 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
7528 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
7531 <!--page 152 -->
7532 additional arguments of any type.
7535 EXAMPLE 4 The following prototype has a variably modified parameter.
7536 <pre>
7537 void addscalar(int n, int m,
7538 double a[n][n*m+300], double x);
7539 int main()
7540 {
7543 return 0;
7544 }
7545 void addscalar(int n, int m,
7546 double a[n][n*m+300], double x)
7547 {
7550 // a is a pointer to a VLA with n*m+300 elements
7551 a[i][j] += x;
7552 }
7553 </pre>
7556 EXAMPLE 5 The following are all compatible function prototype declarators.
7557 <pre>
7558 double maximum(int n, int m, double a[n][m]);
7559 double maximum(int n, int m, double a[*][*]);
7560 double maximum(int n, int m, double a[ ][*]);
7561 double maximum(int n, int m, double a[ ][m]);
7562 </pre>
7563 as are:
7564 <pre>
7565 void f(double (* restrict a)[5]);
7566 void f(double a[restrict][5]);
7569 </pre>
7570 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
7571 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
7573 <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>).
7574 <!--page 153 -->
7577 <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
7578 correspond to the ellipsis.
7579 </small>
7580 <p><small><a name="note145" href="#note145">145)</a> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
7581 </small>
7582 <p><small><a name="note146" href="#note146">146)</a> If both function types are ''old style'', parameter types are not compared.
7583 </small>
7589 <pre>
7590 type-name:
7592 abstract-declarator:
7593 pointer
7595 direct-abstract-declarator:
7596 ( abstract-declarator )
7600 assignment-expression ]
7602 assignment-expression ]
7605 </pre>
7608 In several contexts, it is necessary to specify a type. This is accomplished using a type
7609 name, which is syntactically a declaration for a function or an object of that type that
7612 EXAMPLE The constructions
7613 <pre>
7614 (a) int
7615 (b) int *
7616 (c) int *[3]
7617 (d) int (*)[3]
7618 (e) int (*)[*]
7619 (f) int *()
7620 (g) int (*)(void)
7621 (h) int (*const [])(unsigned int, ...)
7622 </pre>
7623 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
7624 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
7625 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
7626 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
7627 parameter that has type unsigned int and an unspecified number of other parameters, returning an
7628 int.
7633 <!--page 154 -->
7636 <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
7637 parameter specification'', rather than redundant parentheses around the omitted identifier.
7638 </small>
7644 <pre>
7645 typedef-name:
7646 identifier
7647 </pre>
7650 If a typedef name specifies a variably modified type then it shall have block scope.
7653 In a declaration whose storage-class specifier is typedef, each declarator defines an
7654 identifier to be a typedef name that denotes the type specified for the identifier in the way
7655 described in <a href="#6.7.6">6.7.6</a>. Any array size expressions associated with variable length array
7656 declarators are evaluated each time the declaration of the typedef name is reached in the
7657 order of execution. A typedef declaration does not introduce a new type, only a
7658 synonym for the type so specified. That is, in the following declarations:
7659 <pre>
7660 typedef T type_ident;
7661 type_ident D;
7662 </pre>
7663 type_ident is defined as a typedef name with the type specified by the declaration
7664 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
7665 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
7666 typedef name shares the same name space as other identifiers declared in ordinary
7667 declarators.
7669 EXAMPLE 1 After
7670 <pre>
7671 typedef int MILES, KLICKSP();
7672 typedef struct { double hi, lo; } range;
7673 </pre>
7674 the constructions
7675 <pre>
7676 MILES distance;
7677 extern KLICKSP *metricp;
7678 range x;
7679 range z, *zp;
7680 </pre>
7681 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
7682 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
7683 such a structure. The object distance has a type compatible with any other int object.
7686 EXAMPLE 2 After the declarations
7687 <pre>
7688 typedef struct s1 { int x; } t1, *tp1;
7689 typedef struct s2 { int x; } t2, *tp2;
7690 </pre>
7691 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
7692 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
7693 <!--page 155 -->
7695 EXAMPLE 3 The following obscure constructions
7696 <pre>
7697 typedef signed int t;
7698 typedef int plain;
7699 struct tag {
7700 unsigned t:4;
7701 const t:5;
7702 plain r:5;
7703 };
7704 </pre>
7705 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
7706 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
7707 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
7708 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
7709 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
7710 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
7711 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
7712 in an inner scope by
7713 <pre>
7714 t f(t (t));
7715 long t;
7716 </pre>
7717 then a function f is declared with type ''function returning signed int with one unnamed parameter
7718 with type pointer to function returning signed int with one unnamed parameter with type signed
7719 int'', and an identifier t with type long int.
7722 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
7723 following declarations of the signal function specify exactly the same type, the first without making use
7724 of any typedef names.
7725 <pre>
7726 typedef void fv(int), (*pfv)(int);
7727 void (*signal(int, void (*)(int)))(int);
7728 fv *signal(int, fv *);
7729 pfv signal(int, pfv);
7730 </pre>
7733 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
7734 time the typedef name is defined, not each time it is used:
7735 <!--page 156 -->
7736 <pre>
7737 void copyt(int n)
7738 {
7739 typedef int B[n]; // B is n ints, n evaluated now
7740 n += 1;
7741 B a; // a is n ints, n without += 1
7742 int b[n]; // a and b are different sizes
7744 a[i-1] = b[i];
7745 }
7746 </pre>
7752 <pre>
7753 initializer:
7754 assignment-expression
7755 { initializer-list }
7756 { initializer-list , }
7757 initializer-list:
7760 designation:
7761 designator-list =
7762 designator-list:
7763 designator
7764 designator-list designator
7765 designator:
7766 [ constant-expression ]
7767 . identifier
7768 </pre>
7771 No initializer shall attempt to provide a value for an object not contained within the entity
7772 being initialized.
7774 The type of the entity to be initialized shall be an array of unknown size or a complete
7775 object type that is not a variable length array type.
7777 All the expressions in an initializer for an object that has static or thread storage duration
7778 shall be constant expressions or string literals.
7780 If the declaration of an identifier has block scope, and the identifier has external or
7781 internal linkage, the declaration shall have no initializer for the identifier.
7783 If a designator has the form
7784 <pre>
7785 [ constant-expression ]
7786 </pre>
7787 then the current object (defined below) shall have array type and the expression shall be
7788 an integer constant expression. If the array is of unknown size, any nonnegative value is
7789 valid.
7791 If a designator has the form
7792 <pre>
7793 . identifier
7794 </pre>
7795 then the current object (defined below) shall have structure or union type and the
7796 identifier shall be the name of a member of that type.
7797 <!--page 157 -->
7800 An initializer specifies the initial value stored in an object.
7802 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
7803 members of objects of structure and union type do not participate in initialization.
7804 Unnamed members of structure objects have indeterminate value even after initialization.
7806 If an object that has automatic storage duration is not initialized explicitly, its value is
7807 indeterminate. If an object that has static or thread storage duration is not initialized
7808 explicitly, then:
7809 <ul>
7810 <li> if it has pointer type, it is initialized to a null pointer;
7811 <li> if it has arithmetic type, it is initialized to (positive or unsigned) zero;
7812 <li> if it is an aggregate, every member is initialized (recursively) according to these rules,
7813 and any padding is initialized to zero bits;
7814 <li> if it is a union, the first named member is initialized (recursively) according to these
7815 rules, and any padding is initialized to zero bits;
7816 </ul>
7818 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
7819 initial value of the object is that of the expression (after conversion); the same type
7820 constraints and conversions as for simple assignment apply, taking the type of the scalar
7821 to be the unqualified version of its declared type.
7823 The rest of this subclause deals with initializers for objects that have aggregate or union
7824 type.
7826 The initializer for a structure or union object that has automatic storage duration shall be
7827 either an initializer list as described below, or a single expression that has compatible
7828 structure or union type. In the latter case, the initial value of the object, including
7829 unnamed members, is that of the expression.
7831 An array of character type may be initialized by a character string literal or UTF-8 string
7832 literal, optionally enclosed in braces. Successive bytes of the string literal (including the
7833 terminating null character if there is room or if the array is of unknown size) initialize the
7834 elements of the array.
7836 An array with element type compatible with a qualified or unqualified version of
7837 wchar_t may be initialized by a wide string literal, optionally enclosed in braces.
7838 Successive wide characters of the wide string literal (including the terminating null wide
7839 character if there is room or if the array is of unknown size) initialize the elements of the
7840 array.
7842 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
7843 enclosed list of initializers for the elements or named members.
7844 <!--page 158 -->
7846 Each brace-enclosed initializer list has an associated current object. When no
7847 designations are present, subobjects of the current object are initialized in order according
7848 to the type of the current object: array elements in increasing subscript order, structure
7849 members in declaration order, and the first named member of a union.<sup><a href="#note148"><b>148)</b></a></sup> In contrast, a
7850 designation causes the following initializer to begin initialization of the subobject
7851 described by the designator. Initialization then continues forward in order, beginning
7852 with the next subobject after that described by the designator.<sup><a href="#note149"><b>149)</b></a></sup>
7854 Each designator list begins its description with the current object associated with the
7855 closest surrounding brace pair. Each item in the designator list (in order) specifies a
7856 particular member of its current object and changes the current object for the next
7857 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
7858 designator list is the subobject to be initialized by the following initializer.
7860 The initialization shall occur in initializer list order, each initializer provided for a
7861 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note151"><b>151)</b></a></sup>
7862 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
7863 objects that have static storage duration.
7865 If the aggregate or union contains elements or members that are aggregates or unions,
7866 these rules apply recursively to the subaggregates or contained unions. If the initializer of
7867 a subaggregate or contained union begins with a left brace, the initializers enclosed by
7868 that brace and its matching right brace initialize the elements or members of the
7869 subaggregate or the contained union. Otherwise, only enough initializers from the list are
7870 taken to account for the elements or members of the subaggregate or the first member of
7871 the contained union; any remaining initializers are left to initialize the next element or
7872 member of the aggregate of which the current subaggregate or contained union is a part.
7874 If there are fewer initializers in a brace-enclosed list than there are elements or members
7875 of an aggregate, or fewer characters in a string literal used to initialize an array of known
7876 size than there are elements in the array, the remainder of the aggregate shall be
7877 initialized implicitly the same as objects that have static storage duration.
7881 <!--page 159 -->
7883 If an array of unknown size is initialized, its size is determined by the largest indexed
7884 element with an explicit initializer. The array type is completed at the end of its
7885 initializer list.
7887 The evaluations of the initialization list expressions are indeterminately sequenced with
7888 respect to one another and thus the order in which any side effects occur is
7891 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
7892 <pre>
7895 </pre>
7899 EXAMPLE 2 The declaration
7900 <pre>
7902 </pre>
7903 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
7904 and there are three initializers.
7907 EXAMPLE 3 The declaration
7908 <pre>
7913 };
7914 </pre>
7915 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
7917 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
7918 been achieved by
7919 <pre>
7922 };
7923 </pre>
7924 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
7928 EXAMPLE 4 The declaration
7929 <pre>
7932 };
7933 </pre>
7934 initializes the first column of z as specified and initializes the rest with zeros.
7937 EXAMPLE 5 The declaration
7938 <pre>
7940 </pre>
7941 is a definition with an inconsistently bracketed initialization. It defines an array with two element
7945 <!--page 160 -->
7949 EXAMPLE 6 The declaration
7950 <pre>
7952 { 1 },
7955 };
7956 </pre>
7957 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
7959 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
7960 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
7961 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
7962 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
7963 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
7964 diagnostic message would have been issued. The same initialization result could have been achieved by:
7965 <pre>
7970 };
7971 </pre>
7972 or by:
7973 <pre>
7975 {
7976 { 1 },
7977 },
7978 {
7980 },
7981 {
7983 { 6 },
7984 }
7985 };
7986 </pre>
7987 in a fully bracketed form.
7989 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
7990 cause confusion.
7993 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
7994 declaration
7995 <pre>
7996 typedef int A[]; // OK - declared with block scope
7997 </pre>
7998 the declaration
7999 <pre>
8001 </pre>
8002 is identical to
8003 <pre>
8005 </pre>
8006 due to the rules for incomplete types.
8007 <!--page 161 -->
8009 EXAMPLE 8 The declaration
8010 <pre>
8012 </pre>
8013 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
8014 This declaration is identical to
8015 <pre>
8016 char s[] = { 'a', 'b', 'c', '\0' },
8017 t[] = { 'a', 'b', 'c' };
8018 </pre>
8019 The contents of the arrays are modifiable. On the other hand, the declaration
8020 <pre>
8021 char *p = "abc";
8022 </pre>
8023 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
8024 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
8025 modify the contents of the array, the behavior is undefined.
8028 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
8029 designators:
8030 <pre>
8031 enum { member_one, member_two };
8032 const char *nm[] = {
8033 [member_two] = "member two",
8034 [member_one] = "member one",
8035 };
8036 </pre>
8039 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
8040 <pre>
8042 </pre>
8045 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
8046 might be misunderstood:
8047 <pre>
8048 struct { int a[3], b; } w[] =
8050 </pre>
8053 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
8054 <pre>
8055 int a[MAX] = {
8057 };
8058 </pre>
8060 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
8061 than ten, some of the values provided by the first five initializers will be overridden by the second five.
8064 EXAMPLE 13 Any member of a union can be initialized:
8065 <pre>
8066 union { /* ... */ } u = { .any_member = 42 };
8067 </pre>
8069 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>).
8070 <!--page 162 -->
8073 <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
8074 subobjects are initialized as usual, but the subaggregate or contained union does not become the
8075 current object: current objects are associated only with brace-enclosed initializer lists.
8076 </small>
8077 <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
8078 the next subobject of an object containing the union.
8079 </small>
8080 <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
8081 the surrounding brace pair. Note, too, that each separate designator list is independent.
8082 </small>
8083 <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
8084 not be evaluated at all.
8085 </small>
8086 <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.
8087 </small>
8093 <pre>
8094 static_assert-declaration:
8095 _Static_assert ( constant-expression , string-literal ) ;
8096 </pre>
8099 The constant expression shall compare unequal to 0.
8102 The constant expression shall be an integer constant expression. If the value of the
8103 constant expression compares unequal to 0, the declaration has no effect. Otherwise, the
8104 constraint is violated and the implementation shall produce a diagnostic message that
8105 includes the text of the string literal, except that characters not in the basic source
8106 character set are not required to appear in the message.
8108 <!--page 163 -->
8114 <pre>
8115 statement:
8116 labeled-statement
8117 compound-statement
8118 expression-statement
8119 selection-statement
8120 iteration-statement
8121 jump-statement
8122 </pre>
8125 A statement specifies an action to be performed. Except as indicated, statements are
8126 executed in sequence.
8128 A block allows a set of declarations and statements to be grouped into one syntactic unit.
8129 The initializers of objects that have automatic storage duration, and the variable length
8130 array declarators of ordinary identifiers with block scope, are evaluated and the values are
8131 stored in the objects (including storing an indeterminate value in objects without an
8132 initializer) each time the declaration is reached in the order of execution, as if it were a
8133 statement, and within each declaration in the order that declarators appear.
8135 A full expression is an expression that is not part of another expression or of a declarator.
8136 Each of the following is a full expression: an initializer that is not part of a compound
8137 literal; the expression in an expression statement; the controlling expression of a selection
8138 statement (if or switch); the controlling expression of a while or do statement; each
8139 of the (optional) expressions of a for statement; the (optional) expression in a return
8140 statement. There is a sequence point between the evaluation of a full expression and the
8141 evaluation of the next full expression to be evaluated.
8142 <p><b> Forward references</b>: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
8143 (<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>).
8149 <pre>
8150 labeled-statement:
8151 identifier : statement
8152 case constant-expression : statement
8153 default : statement
8154 </pre>
8157 A case or default label shall appear only in a switch statement. Further
8158 constraints on such labels are discussed under the switch statement.
8159 <!--page 164 -->
8161 Label names shall be unique within a function.
8164 Any statement may be preceded by a prefix that declares an identifier as a label name.
8165 Labels in themselves do not alter the flow of control, which continues unimpeded across
8166 them.
8167 <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>).
8173 <pre>
8174 compound-statement:
8176 block-item-list:
8177 block-item
8178 block-item-list block-item
8179 block-item:
8180 declaration
8181 statement
8182 </pre>
8185 A compound statement is a block.
8191 <pre>
8192 expression-statement:
8194 </pre>
8197 The expression in an expression statement is evaluated as a void expression for its side
8200 A null statement (consisting of just a semicolon) performs no operations.
8202 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
8203 discarding of its value may be made explicit by converting the expression to a void expression by means of
8204 a cast:
8205 <pre>
8206 int p(int);
8207 /* ... */
8208 (void)p(0);
8209 </pre>
8213 <!--page 165 -->
8215 EXAMPLE 2 In the program fragment
8216 <pre>
8217 char *s;
8218 /* ... */
8219 while (*s++ != '\0')
8220 ;
8221 </pre>
8222 a null statement is used to supply an empty loop body to the iteration statement.
8225 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
8226 statement.
8227 <pre>
8228 while (loop1) {
8229 /* ... */
8230 while (loop2) {
8231 /* ... */
8232 if (want_out)
8233 goto end_loop1;
8234 /* ... */
8235 }
8236 /* ... */
8237 end_loop1: ;
8238 }
8239 </pre>
8244 <p><small><a name="note153" href="#note153">153)</a> Such as assignments, and function calls which have side effects.
8245 </small>
8251 <pre>
8252 selection-statement:
8253 if ( expression ) statement
8254 if ( expression ) statement else statement
8255 switch ( expression ) statement
8256 </pre>
8259 A selection statement selects among a set of statements depending on the value of a
8260 controlling expression.
8262 A selection statement is a block whose scope is a strict subset of the scope of its
8263 enclosing block. Each associated substatement is also a block whose scope is a strict
8264 subset of the scope of the selection statement.
8270 The controlling expression of an if statement shall have scalar type.
8273 In both forms, the first substatement is executed if the expression compares unequal to 0.
8274 In the else form, the second substatement is executed if the expression compares equal
8275 <!--page 166 -->
8276 to 0. If the first substatement is reached via a label, the second substatement is not
8277 executed.
8279 An else is associated with the lexically nearest preceding if that is allowed by the
8280 syntax.
8286 The controlling expression of a switch statement shall have integer type.
8288 If a switch statement has an associated case or default label within the scope of an
8289 identifier with a variably modified type, the entire switch statement shall be within the
8292 The expression of each case label shall be an integer constant expression and no two of
8293 the case constant expressions in the same switch statement shall have the same value
8294 after conversion. There may be at most one default label in a switch statement.
8295 (Any enclosed switch statement may have a default label or case constant
8296 expressions with values that duplicate case constant expressions in the enclosing
8297 switch statement.)
8300 A switch statement causes control to jump to, into, or past the statement that is the
8301 switch body, depending on the value of a controlling expression, and on the presence of a
8302 default label and the values of any case labels on or in the switch body. A case or
8303 default label is accessible only within the closest enclosing switch statement.
8305 The integer promotions are performed on the controlling expression. The constant
8306 expression in each case label is converted to the promoted type of the controlling
8307 expression. If a converted value matches that of the promoted controlling expression,
8308 control jumps to the statement following the matched case label. Otherwise, if there is
8309 a default label, control jumps to the labeled statement. If no converted case constant
8310 expression matches and there is no default label, no part of the switch body is
8311 executed.
8314 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
8315 switch statement.
8320 <!--page 167 -->
8322 EXAMPLE In the artificial program fragment
8323 <pre>
8324 switch (expr)
8325 {
8326 int i = 4;
8327 f(i);
8328 case 0:
8329 i = 17;
8330 /* falls through into default code */
8331 default:
8332 printf("%d\n", i);
8333 }
8334 </pre>
8335 the object whose identifier is i exists with automatic storage duration (within the block) but is never
8336 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
8337 access an indeterminate value. Similarly, the call to the function f cannot be reached.
8341 <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
8342 default label associated with the switch that is in the block containing the declaration.
8343 </small>
8349 <pre>
8350 iteration-statement:
8351 while ( expression ) statement
8352 do statement while ( expression ) ;
8353 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
8355 </pre>
8358 The controlling expression of an iteration statement shall have scalar type.
8360 The declaration part of a for statement shall only declare identifiers for objects having
8361 storage class auto or register.
8364 An iteration statement causes a statement called the loop body to be executed repeatedly
8365 until the controlling expression compares equal to 0. The repetition occurs regardless of
8366 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note155"><b>155)</b></a></sup>
8368 An iteration statement is a block whose scope is a strict subset of the scope of its
8369 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
8370 of the iteration statement.
8372 An iteration statement whose controlling expression is not a constant expression,<sup><a href="#note156"><b>156)</b></a></sup> that
8373 performs no input/output operations, does not access volatile objects, and performs no
8374 synchronization or atomic operations in its body, controlling expression, or (in the case of
8376 <!--page 168 -->
8377 a for statement) its expression-3, may be assumed by the implementation to
8381 <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
8382 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
8383 </small>
8384 <p><small><a name="note156" href="#note156">156)</a> An omitted controlling expression is replaced by a nonzero constant, which is a constant expression.
8385 </small>
8386 <p><small><a name="note157" href="#note157">157)</a> This is intended to allow compiler transformations such as removal of empty loops even when
8387 termination cannot be proven.
8388 </small>
8393 The evaluation of the controlling expression takes place before each execution of the loop
8394 body.
8399 The evaluation of the controlling expression takes place after each execution of the loop
8400 body.
8405 The statement
8406 <pre>
8408 </pre>
8409 behaves as follows: The expression expression-2 is the controlling expression that is
8410 evaluated before each execution of the loop body. The expression expression-3 is
8411 evaluated as a void expression after each execution of the loop body. If clause-1 is a
8412 declaration, the scope of any identifiers it declares is the remainder of the declaration and
8413 the entire loop, including the other two expressions; it is reached in the order of execution
8414 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
8415 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note158"><b>158)</b></a></sup>
8418 nonzero constant.
8421 <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
8422 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
8423 such that execution of the loop continues until the expression compares equal to 0; and expression-3
8424 specifies an operation (such as incrementing) that is performed after each iteration.
8425 </small>
8431 <pre>
8432 jump-statement:
8433 goto identifier ;
8434 continue ;
8435 break ;
8437 </pre>
8442 <!--page 169 -->
8445 A jump statement causes an unconditional jump to another place.
8451 The identifier in a goto statement shall name a label located somewhere in the enclosing
8452 function. A goto statement shall not jump from outside the scope of an identifier having
8453 a variably modified type to inside the scope of that identifier.
8456 A goto statement causes an unconditional jump to the statement prefixed by the named
8457 label in the enclosing function.
8459 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
8460 following outline presents one possible approach to a problem based on these three assumptions:
8461 <ol>
8462 <li> The general initialization code accesses objects only visible to the current function.
8463 <li> The general initialization code is too large to warrant duplication.
8464 <li> The code to determine the next operation is at the head of the loop. (To allow it to be reached by
8465 continue statements, for example.)
8466 <!--page 170 -->
8467 <pre>
8468 /* ... */
8469 goto first_time;
8470 for (;;) {
8471 // determine next operation
8472 /* ... */
8473 if (need to reinitialize) {
8474 // reinitialize-only code
8475 /* ... */
8476 first_time:
8477 // general initialization code
8478 /* ... */
8479 continue;
8480 }
8481 // handle other operations
8482 /* ... */
8483 }
8484 </pre>
8485 </ol>
8487 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
8488 modified types. A jump within the scope, however, is permitted.
8489 <pre>
8490 goto lab3; // invalid: going INTO scope of VLA.
8491 {
8492 double a[n];
8494 lab3:
8496 goto lab4; // valid: going WITHIN scope of VLA.
8498 lab4:
8500 }
8501 goto lab4; // invalid: going INTO scope of VLA.
8502 </pre>
8509 A continue statement shall appear only in or as a loop body.
8512 A continue statement causes a jump to the loop-continuation portion of the smallest
8513 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
8514 of the statements
8515 while (/* ... */) { do { for (/* ... */) {
8516 <pre>
8517 /* ... */ /* ... */ /* ... */
8518 continue; continue; continue;
8519 /* ... */ /* ... */ /* ... */
8520 </pre>
8521 contin: ; contin: ; contin: ;
8522 } } while (/* ... */); }
8523 unless the continue statement shown is in an enclosed iteration statement (in which
8524 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note159"><b>159)</b></a></sup>
8527 <p><small><a name="note159" href="#note159">159)</a> Following the contin: label is a null statement.
8528 </small>
8534 A break statement shall appear only in or as a switch body or loop body.
8537 A break statement terminates execution of the smallest enclosing switch or iteration
8538 statement.
8542 <!--page 171 -->
8548 A return statement with an expression shall not appear in a function whose return type
8549 is void. A return statement without an expression shall only appear in a function
8550 whose return type is void.
8553 A return statement terminates execution of the current function and returns control to
8554 its caller. A function may have any number of return statements.
8556 If a return statement with an expression is executed, the value of the expression is
8557 returned to the caller as the value of the function call expression. If the expression has a
8558 type different from the return type of the function in which it appears, the value is
8559 converted as if by assignment to an object having the return type of the function.<sup><a href="#note160"><b>160)</b></a></sup>
8561 EXAMPLE In:
8562 <pre>
8563 struct s { double i; } f(void);
8564 union {
8565 struct {
8566 int f1;
8567 struct s f2;
8568 } u1;
8569 struct {
8570 struct s f3;
8571 int f4;
8572 } u2;
8573 } g;
8574 struct s f(void)
8575 {
8576 return g.u1.f2;
8577 }
8578 /* ... */
8579 g.u2.f3 = f();
8580 </pre>
8581 there is no undefined behavior, although there would be if the assignment were done directly (without using
8582 a function call to fetch the value).
8587 <!--page 172 -->
8590 <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
8591 apply to the case of function return. The representation of floating-point values may have wider range
8592 or precision than implied by the type; a cast may be used to remove this extra range and precision.
8593 </small>
8599 <pre>
8600 translation-unit:
8601 external-declaration
8602 translation-unit external-declaration
8603 external-declaration:
8604 function-definition
8605 declaration
8606 </pre>
8609 The storage-class specifiers auto and register shall not appear in the declaration
8610 specifiers in an external declaration.
8612 There shall be no more than one external definition for each identifier declared with
8613 internal linkage in a translation unit. Moreover, if an identifier declared with internal
8614 linkage is used in an expression (other than as a part of the operand of a sizeof
8615 operator whose result is an integer constant), there shall be exactly one external definition
8616 for the identifier in the translation unit.
8619 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,
8620 which consists of a sequence of external declarations. These are described as ''external''
8621 because they appear outside any function (and hence have file scope). As discussed in
8622 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
8623 by the identifier is a definition.
8625 An external definition is an external declaration that is also a definition of a function
8626 (other than an inline definition) or an object. If an identifier declared with external
8627 linkage is used in an expression (other than as part of the operand of a sizeof operator
8628 whose result is an integer constant), somewhere in the entire program there shall be
8629 exactly one external definition for the identifier; otherwise, there shall be no more than
8635 <!--page 173 -->
8638 <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
8639 external definition for it.
8640 </small>
8646 <pre>
8647 function-definition:
8649 declaration-list:
8650 declaration
8651 declaration-list declaration
8652 </pre>
8655 The identifier declared in a function definition (which is the name of the function) shall
8656 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note162"><b>162)</b></a></sup>
8658 The return type of a function shall be void or a complete object type other than array
8659 type.
8661 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
8662 static.
8664 If the declarator includes a parameter type list, the declaration of each parameter shall
8665 include an identifier, except for the special case of a parameter list consisting of a single
8666 parameter of type void, in which case there shall not be an identifier. No declaration list
8667 shall follow.
8669 If the declarator includes an identifier list, each declaration in the declaration list shall
8670 have at least one declarator, those declarators shall declare only identifiers from the
8671 identifier list, and every identifier in the identifier list shall be declared. An identifier
8672 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
8673 declaration list shall contain no storage-class specifier other than register and no
8674 initializations.
8678 <!--page 174 -->
8681 The declarator in a function definition specifies the name of the function being defined
8682 and the identifiers of its parameters. If the declarator includes a parameter type list, the
8683 list also specifies the types of all the parameters; such a declarator also serves as a
8684 function prototype for later calls to the same function in the same translation unit. If the
8685 declarator includes an identifier list,<sup><a href="#note163"><b>163)</b></a></sup> the types of the parameters shall be declared in a
8686 following declaration list. In either case, the type of each parameter is adjusted as
8687 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
8688 type.
8690 If a function that accepts a variable number of arguments is defined without a parameter
8691 type list that ends with the ellipsis notation, the behavior is undefined.
8693 Each parameter has automatic storage duration; its identifier is an lvalue.<sup><a href="#note164"><b>164)</b></a></sup> The layout
8694 of the storage for parameters is unspecified.
8696 On entry to the function, the size expressions of each variably modified parameter are
8697 evaluated and the value of each argument expression is converted to the type of the
8698 corresponding parameter as if by assignment. (Array expressions and function
8699 designators as arguments were converted to pointers before the call.)
8701 After all parameters have been assigned, the compound statement that constitutes the
8702 body of the function definition is executed.
8704 If the } that terminates a function is reached, and the value of the function call is used by
8705 the caller, the behavior is undefined.
8707 EXAMPLE 1 In the following:
8708 <pre>
8709 extern int max(int a, int b)
8710 {
8711 return a > b ? a : b;
8712 }
8713 </pre>
8714 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
8715 function declarator; and
8716 <pre>
8717 { return a > b ? a : b; }
8718 </pre>
8719 is the function body. The following similar definition uses the identifier-list form for the parameter
8720 declarations:
8725 <!--page 175 -->
8726 <pre>
8727 extern int max(a, b)
8728 int a, b;
8729 {
8730 return a > b ? a : b;
8731 }
8732 </pre>
8733 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
8734 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
8735 to the function, whereas the second form does not.
8738 EXAMPLE 2 To pass one function to another, one might say
8739 <pre>
8740 int f(void);
8741 /* ... */
8742 g(f);
8743 </pre>
8744 Then the definition of g might read
8745 <pre>
8746 void g(int (*funcp)(void))
8747 {
8748 /* ... */
8749 (*funcp)(); /* or funcp(); ... */
8750 }
8751 </pre>
8752 or, equivalently,
8753 <pre>
8754 void g(int func(void))
8755 {
8756 /* ... */
8757 func(); /* or (*func)(); ... */
8758 }
8759 </pre>
8763 <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:
8765 <pre>
8766 typedef int F(void); // type F is ''function with no parameters
8767 // returning int''
8768 F f, g; // f and g both have type compatible with F
8769 F f { /* ... */ } // WRONG: syntax/constraint error
8770 F g() { /* ... */ } // WRONG: declares that g returns a function
8771 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
8772 int g() { /* ... */ } // RIGHT: g has type compatible with F
8773 F *e(void) { /* ... */ } // e returns a pointer to a function
8774 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
8775 int (*fp)(void); // fp points to a function that has type F
8776 F *Fp; // Fp points to a function that has type F
8777 </pre>
8778 </small>
8779 <p><small><a name="note163" href="#note163">163)</a> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
8780 </small>
8781 <p><small><a name="note164" href="#note164">164)</a> A parameter identifier cannot be redeclared in the function body except in an enclosed block.
8782 </small>
8788 If the declaration of an identifier for an object has file scope and an initializer, the
8789 declaration is an external definition for the identifier.
8791 A declaration of an identifier for an object that has file scope without an initializer, and
8792 without a storage-class specifier or with the storage-class specifier static, constitutes a
8793 tentative definition. If a translation unit contains one or more tentative definitions for an
8794 identifier, and the translation unit contains no external definition for that identifier, then
8795 the behavior is exactly as if the translation unit contains a file scope declaration of that
8796 identifier, with the composite type as of the end of the translation unit, with an initializer
8797 equal to 0.
8799 If the declaration of an identifier for an object is a tentative definition and has internal
8800 linkage, the declared type shall not be an incomplete type.
8801 <!--page 176 -->
8803 EXAMPLE 1
8804 <pre>
8805 int i1 = 1; // definition, external linkage
8806 static int i2 = 2; // definition, internal linkage
8807 extern int i3 = 3; // definition, external linkage
8808 int i4; // tentative definition, external linkage
8809 static int i5; // tentative definition, internal linkage
8810 int i1; // valid tentative definition, refers to previous
8812 int i3; // valid tentative definition, refers to previous
8813 int i4; // valid tentative definition, refers to previous
8815 extern int i1; // refers to previous, whose linkage is external
8816 extern int i2; // refers to previous, whose linkage is internal
8817 extern int i3; // refers to previous, whose linkage is external
8818 extern int i4; // refers to previous, whose linkage is external
8819 extern int i5; // refers to previous, whose linkage is internal
8820 </pre>
8823 EXAMPLE 2 If at the end of the translation unit containing
8824 <pre>
8825 int i[];
8826 </pre>
8827 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
8828 zero on program startup.
8829 <!--page 177 -->
8835 <!--page 178 -->
8836 <pre>
8837 preprocessing-file:
8839 group:
8840 group-part
8841 group group-part
8842 group-part:
8843 if-section
8844 control-line
8845 text-line
8846 # non-directive
8847 if-section:
8849 if-group:
8853 elif-groups:
8854 elif-group
8855 elif-groups elif-group
8856 elif-group:
8858 else-group:
8860 endif-line:
8861 # endif new-line
8862 control-line:
8863 # include pp-tokens new-line
8864 # define identifier replacement-list new-line
8866 replacement-list new-line
8867 # define identifier lparen ... ) replacement-list new-line
8868 # define identifier lparen identifier-list , ... )
8869 replacement-list new-line
8870 # undef identifier new-line
8871 # line pp-tokens new-line
8874 # new-line
8875 text-line:
8877 non-directive:
8878 pp-tokens new-line
8879 lparen:
8880 a ( character not immediately preceded by white-space
8881 replacement-list:
8883 pp-tokens:
8884 preprocessing-token
8885 pp-tokens preprocessing-token
8886 new-line:
8887 the new-line character
8888 </pre>
8891 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
8892 following constraints: The first token in the sequence is a # preprocessing token that (at
8893 the start of translation phase 4) is either the first character in the source file (optionally
8894 after white space containing no new-line characters) or that follows white space
8895 containing at least one new-line character. The last token in the sequence is the first new-
8896 line character that follows the first token in the sequence.<sup><a href="#note165"><b>165)</b></a></sup> A new-line character ends
8897 the preprocessing directive even if it occurs within what would otherwise be an
8899 <!--page 179 -->
8900 invocation of a function-like macro.
8902 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
8903 with any of the directive names appearing in the syntax.
8905 When in a group that is skipped (<a href="#6.10.1">6.10.1</a>), the directive syntax is relaxed to allow any
8906 sequence of preprocessing tokens to occur between the directive name and the following
8907 new-line character.
8910 The only white-space characters that shall appear between preprocessing tokens within a
8911 preprocessing directive (from just after the introducing # preprocessing token through
8912 just before the terminating new-line character) are space and horizontal-tab (including
8913 spaces that have replaced comments or possibly other white-space characters in
8914 translation phase 3).
8917 The implementation can process and skip sections of source files conditionally, include
8918 other source files, and replace macros. These capabilities are called preprocessing,
8919 because conceptually they occur before translation of the resulting translation unit.
8921 The preprocessing tokens within a preprocessing directive are not subject to macro
8922 expansion unless otherwise stated.
8924 EXAMPLE In:
8925 <pre>
8926 #define EMPTY
8928 </pre>
8929 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
8930 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
8931 replaced.
8935 <p><small><a name="note165" href="#note165">165)</a> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
8936 significance, as all white space is equivalent except in certain situations during preprocessing (see the
8937 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
8938 </small>
8944 The expression that controls conditional inclusion shall be an integer constant expression
8945 except that: identifiers (including those lexically identical to keywords) are interpreted as *
8946 described below;<sup><a href="#note166"><b>166)</b></a></sup> and it may contain unary operator expressions of the form
8947 <pre>
8948 defined identifier
8949 </pre>
8950 or
8951 <pre>
8952 defined ( identifier )
8953 </pre>
8954 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
8957 <!--page 180 -->
8958 predefined or if it has been the subject of a #define preprocessing directive without an
8959 intervening #undef directive with the same subject identifier), 0 if it is not.
8961 Each preprocessing token that remains (in the list of preprocessing tokens that will
8962 become the controlling expression) after all macro replacements have occurred shall be in
8966 Preprocessing directives of the forms
8967 <pre>
8970 </pre>
8971 check whether the controlling constant expression evaluates to nonzero.
8973 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
8974 the controlling constant expression are replaced (except for those macro names modified
8975 by the defined unary operator), just as in normal text. If the token defined is
8976 generated as a result of this replacement process or use of the defined unary operator
8977 does not match one of the two specified forms prior to macro replacement, the behavior is
8978 undefined. After all replacements due to macro expansion and the defined unary
8979 operator have been performed, all remaining identifiers (including those lexically
8980 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
8981 token is converted into a token. The resulting tokens compose the controlling constant
8982 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
8983 token conversion and evaluation, all signed integer types and all unsigned integer types
8984 act as if they have the same representation as, respectively, the types intmax_t and
8985 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
8986 character constants, which may involve converting escape sequences into execution
8987 character set members. Whether the numeric value for these character constants matches
8988 the value obtained when an identical character constant occurs in an expression (other
8989 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note168"><b>168)</b></a></sup> Also, whether a
8990 single-character character constant may have a negative value is implementation-defined.
8995 <!--page 181 -->
8997 Preprocessing directives of the forms
8998 <pre>
9001 </pre>
9002 check whether the identifier is or is not currently defined as a macro name. Their
9003 conditions are equivalent to #if defined identifier and #if !defined identifier
9004 respectively.
9006 Each directive's condition is checked in order. If it evaluates to false (zero), the group
9007 that it controls is skipped: directives are processed only through the name that determines
9008 the directive in order to keep track of the level of nested conditionals; the rest of the
9009 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
9010 group. Only the first group whose control condition evaluates to true (nonzero) is
9011 processed. If none of the conditions evaluates to true, and there is a #else directive, the
9012 group controlled by the #else is processed; lacking a #else directive, all the groups
9014 <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
9018 <p><small><a name="note166" href="#note166">166)</a> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
9019 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
9020 </small>
9021 <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
9022 0x8000 is signed and positive within a #if expression even though it would be unsigned in
9023 translation phase 7.
9024 </small>
9025 <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
9026 evaluate to the same value in these two contexts.
9027 #if 'z' - 'a' == 25
9028 if ('z' - 'a' == 25)
9029 </small>
9030 <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
9031 before the terminating new-line character. However, comments may appear anywhere in a source file,
9032 including within a preprocessing directive.
9033 </small>
9039 A #include directive shall identify a header or source file that can be processed by the
9040 implementation.
9043 A preprocessing directive of the form
9044 <pre>
9046 </pre>
9047 searches a sequence of implementation-defined places for a header identified uniquely by
9048 the specified sequence between the < and > delimiters, and causes the replacement of that
9049 directive by the entire contents of the header. How the places are specified or the header
9050 identified is implementation-defined.
9052 A preprocessing directive of the form
9053 <pre>
9054 # include "q-char-sequence" new-line
9055 </pre>
9056 causes the replacement of that directive by the entire contents of the source file identified
9057 by the specified sequence between the " delimiters. The named source file is searched
9060 <!--page 182 -->
9061 for in an implementation-defined manner. If this search is not supported, or if the search
9062 fails, the directive is reprocessed as if it read
9063 <pre>
9064 # include <h-char-sequence> new-line
9065 </pre>
9066 with the identical contained sequence (including > characters, if any) from the original
9067 directive.
9068 <p><!--para 4 -->
9069 A preprocessing directive of the form
9070 <pre>
9071 # include pp-tokens new-line
9072 </pre>
9073 (that does not match one of the two previous forms) is permitted. The preprocessing
9074 tokens after include in the directive are processed just as in normal text. (Each
9075 identifier currently defined as a macro name is replaced by its replacement list of
9076 preprocessing tokens.) The directive resulting after all replacements shall match one of
9077 the two previous forms.<sup><a href="#note170"><b>170)</b></a></sup> The method by which a sequence of preprocessing tokens
9078 between a < and a > preprocessing token pair or a pair of " characters is combined into a
9079 single header name preprocessing token is implementation-defined.
9081 The implementation shall provide unique mappings for sequences consisting of one or
9082 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
9083 first character shall not be a digit. The implementation may ignore distinctions of
9084 alphabetical case and restrict the mapping to eight significant characters before the
9085 period.
9087 A #include preprocessing directive may appear in a source file that has been read
9088 because of a #include directive in another file, up to an implementation-defined
9091 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
9092 <pre>
9094 #include "myprog.h"
9095 </pre>
9100 <!--page 183 -->
9102 EXAMPLE 2 This illustrates macro-replaced #include directives:
9103 <pre>
9104 #if VERSION == 1
9105 #define INCFILE "vers1.h"
9106 #elif VERSION == 2
9107 #define INCFILE "vers2.h" // and so on
9108 #else
9109 #define INCFILE "versN.h"
9110 #endif
9111 #include INCFILE
9112 </pre>
9117 <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
9118 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.
9119 </small>
9125 Two replacement lists are identical if and only if the preprocessing tokens in both have
9126 the same number, ordering, spelling, and white-space separation, where all white-space
9127 separations are considered identical.
9129 An identifier currently defined as an object-like macro shall not be redefined by another
9130 #define preprocessing directive unless the second definition is an object-like macro
9131 definition and the two replacement lists are identical. Likewise, an identifier currently
9132 defined as a function-like macro shall not be redefined by another #define
9133 preprocessing directive unless the second definition is a function-like macro definition
9134 that has the same number and spelling of parameters, and the two replacement lists are
9135 identical.
9137 There shall be white-space between the identifier and the replacement list in the definition
9138 of an object-like macro.
9140 If the identifier-list in the macro definition does not end with an ellipsis, the number of
9141 arguments (including those arguments consisting of no preprocessing tokens) in an
9142 invocation of a function-like macro shall equal the number of parameters in the macro
9143 definition. Otherwise, there shall be more arguments in the invocation than there are
9144 parameters in the macro definition (excluding the ...). There shall exist a )
9145 preprocessing token that terminates the invocation.
9147 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
9148 macro that uses the ellipsis notation in the parameters.
9150 A parameter identifier in a function-like macro shall be uniquely declared within its
9151 scope.
9154 The identifier immediately following the define is called the macro name. There is one
9155 name space for macro names. Any white-space characters preceding or following the
9156 replacement list of preprocessing tokens are not considered part of the replacement list
9157 <!--page 184 -->
9158 for either form of macro.
9160 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
9161 a preprocessing directive could begin, the identifier is not subject to macro replacement.
9163 A preprocessing directive of the form
9164 <pre>
9165 # define identifier replacement-list new-line
9166 </pre>
9167 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note171"><b>171)</b></a></sup>
9168 to be replaced by the replacement list of preprocessing tokens that constitute the
9169 remainder of the directive. The replacement list is then rescanned for more macro names
9170 as specified below.
9172 A preprocessing directive of the form
9173 <pre>
9175 # define identifier lparen ... ) replacement-list new-line
9176 # define identifier lparen identifier-list , ... ) replacement-list new-line
9177 </pre>
9178 defines a function-like macro with parameters, whose use is similar syntactically to a
9179 function call. The parameters are specified by the optional list of identifiers, whose scope
9180 extends from their declaration in the identifier list until the new-line character that
9181 terminates the #define preprocessing directive. Each subsequent instance of the
9182 function-like macro name followed by a ( as the next preprocessing token introduces the
9183 sequence of preprocessing tokens that is replaced by the replacement list in the definition
9184 (an invocation of the macro). The replaced sequence of preprocessing tokens is
9185 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
9186 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
9187 tokens making up an invocation of a function-like macro, new-line is considered a normal
9188 white-space character.
9190 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
9191 forms the list of arguments for the function-like macro. The individual arguments within
9192 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
9193 between matching inner parentheses do not separate arguments. If there are sequences of
9194 preprocessing tokens within the list of arguments that would otherwise act as
9195 preprocessing directives,<sup><a href="#note172"><b>172)</b></a></sup> the behavior is undefined.
9197 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
9198 including any separating comma preprocessing tokens, are merged to form a single item:
9201 <!--page 185 -->
9202 the variable arguments. The number of arguments so combined is such that, following
9203 merger, the number of arguments is one more than the number of parameters in the macro
9204 definition (excluding the ...).
9207 <p><small><a name="note171" href="#note171">171)</a> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
9208 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
9209 are never scanned for macro names or parameters.
9210 </small>
9211 <p><small><a name="note172" href="#note172">172)</a> Despite the name, a non-directive is a preprocessing directive.
9212 </small>
9217 After the arguments for the invocation of a function-like macro have been identified,
9218 argument substitution takes place. A parameter in the replacement list, unless preceded
9219 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
9220 replaced by the corresponding argument after all macros contained therein have been
9221 expanded. Before being substituted, each argument's preprocessing tokens are
9222 completely macro replaced as if they formed the rest of the preprocessing file; no other
9223 preprocessing tokens are available.
9225 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
9226 were a parameter, and the variable arguments shall form the preprocessing tokens used to
9227 replace it.
9233 Each # preprocessing token in the replacement list for a function-like macro shall be
9234 followed by a parameter as the next preprocessing token in the replacement list.
9237 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
9238 token, both are replaced by a single character string literal preprocessing token that
9239 contains the spelling of the preprocessing token sequence for the corresponding
9240 argument. Each occurrence of white space between the argument's preprocessing tokens
9241 becomes a single space character in the character string literal. White space before the
9242 first preprocessing token and after the last preprocessing token composing the argument
9243 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
9244 is retained in the character string literal, except for special handling for producing the
9245 spelling of string literals and character constants: a \ character is inserted before each "
9246 and \ character of a character constant or string literal (including the delimiting "
9247 characters), except that it is implementation-defined whether a \ character is inserted
9248 before the \ character beginning a universal character name. If the replacement that
9249 results is not a valid character string literal, the behavior is undefined. The character
9250 string literal corresponding to an empty argument is "". The order of evaluation of # and
9251 ## operators is unspecified.
9252 <!--page 186 -->
9258 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
9259 list for either form of macro definition.
9262 If, in the replacement list of a function-like macro, a parameter is immediately preceded
9263 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
9264 argument's preprocessing token sequence; however, if an argument consists of no
9265 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
9268 For both object-like and function-like macro invocations, before the replacement list is
9269 reexamined for more macro names to replace, each instance of a ## preprocessing token
9270 in the replacement list (not from an argument) is deleted and the preceding preprocessing
9271 token is concatenated with the following preprocessing token. Placemarker
9272 preprocessing tokens are handled specially: concatenation of two placemarkers results in
9273 a single placemarker preprocessing token, and concatenation of a placemarker with a
9274 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
9275 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
9276 token is available for further macro replacement. The order of evaluation of ## operators
9277 is unspecified.
9279 EXAMPLE In the following fragment:
9280 <pre>
9281 #define hash_hash # ## #
9282 #define mkstr(a) # a
9283 #define in_between(a) mkstr(a)
9284 #define join(c, d) in_between(c hash_hash d)
9285 char p[] = join(x, y); // equivalent to
9286 // char p[] = "x ## y";
9287 </pre>
9288 The expansion produces, at various stages:
9289 <pre>
9290 join(x, y)
9291 in_between(x hash_hash y)
9292 in_between(x ## y)
9293 mkstr(x ## y)
9294 "x ## y"
9295 </pre>
9296 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
9297 this new token is not the ## operator.
9300 <!--page 187 -->
9303 <p><small><a name="note173" href="#note173">173)</a> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
9304 exist only within translation phase 4.
9305 </small>
9310 After all parameters in the replacement list have been substituted and # and ##
9311 processing has taken place, all placemarker preprocessing tokens are removed. The
9312 resulting preprocessing token sequence is then rescanned, along with all subsequent
9313 preprocessing tokens of the source file, for more macro names to replace.
9315 If the name of the macro being replaced is found during this scan of the replacement list
9316 (not including the rest of the source file's preprocessing tokens), it is not replaced.
9317 Furthermore, if any nested replacements encounter the name of the macro being replaced,
9318 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
9319 available for further replacement even if they are later (re)examined in contexts in which
9320 that macro name preprocessing token would otherwise have been replaced.
9322 The resulting completely macro-replaced preprocessing token sequence is not processed
9323 as a preprocessing directive even if it resembles one, but all pragma unary operator
9329 A macro definition lasts (independent of block structure) until a corresponding #undef
9330 directive is encountered or (if none is encountered) until the end of the preprocessing
9331 translation unit. Macro definitions have no significance after translation phase 4.
9333 A preprocessing directive of the form
9334 <pre>
9335 # undef identifier new-line
9336 </pre>
9337 causes the specified identifier no longer to be defined as a macro name. It is ignored if
9338 the specified identifier is not currently defined as a macro name.
9340 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
9341 <pre>
9342 #define TABSIZE 100
9343 int table[TABSIZE];
9344 </pre>
9347 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
9348 It has the advantages of working for any compatible types of the arguments and of generating in-line code
9349 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
9350 arguments a second time (including side effects) and generating more code than a function if invoked
9351 several times. It also cannot have its address taken, as it has none.
9352 <pre>
9353 #define max(a, b) ((a) > (b) ? (a) : (b))
9354 </pre>
9355 The parentheses ensure that the arguments and the resulting expression are bound properly.
9356 <!--page 188 -->
9358 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
9359 <pre>
9360 #define x 3
9361 #define f(a) f(x * (a))
9362 #undef x
9363 #define x 2
9364 #define g f
9365 #define z z[0]
9366 #define h g(~
9367 #define m(a) a(w)
9369 #define t(a) a
9370 #define p() int
9371 #define q(x) x
9372 #define r(x,y) x ## y
9373 #define str(x) # x
9376 (f)^m(m);
9379 </pre>
9380 results in
9381 <pre>
9386 </pre>
9389 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
9390 sequence
9391 <pre>
9392 #define str(s) # s
9393 #define xstr(s) str(s)
9395 x ## s, x ## t)
9396 #define INCFILE(n) vers ## n
9397 #define glue(a, b) a ## b
9398 #define xglue(a, b) glue(a, b)
9399 #define HIGHLOW "hello"
9400 #define LOW LOW ", world"
9403 == 0) str(: @\n), s);
9404 #include xstr(INCFILE(2).h)
9405 glue(HIGH, LOW);
9406 xglue(HIGH, LOW)
9407 </pre>
9408 results in
9409 <!--page 189 -->
9410 <pre>
9412 fputs(
9414 s);
9415 #include "vers2.h" (after macro replacement, before file access)
9416 "hello";
9418 </pre>
9419 or, after concatenation of the character string literals,
9420 <pre>
9421 printf("x1= %d, x2= %s", x1, x2);
9422 fputs(
9424 s);
9425 #include "vers2.h" (after macro replacement, before file access)
9426 "hello";
9427 "hello, world"
9428 </pre>
9429 Space around the # and ## tokens in the macro definition is optional.
9432 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
9433 <pre>
9434 #define t(x,y,z) x ## y ## z
9437 </pre>
9438 results in
9439 <pre>
9442 </pre>
9445 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
9446 <pre>
9449 #define FUNC_LIKE(a) ( a )
9450 #define FUNC_LIKE( a )( /* note the white space */ \
9451 a /* other stuff on this line
9452 */ )
9453 </pre>
9454 But the following redefinitions are invalid:
9455 <pre>
9456 #define OBJ_LIKE (0) // different token sequence
9458 #define FUNC_LIKE(b) ( a ) // different parameter usage
9459 #define FUNC_LIKE(b) ( b ) // different parameter spelling
9460 </pre>
9463 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
9464 <!--page 190 -->
9465 <pre>
9466 #define debug(...) fprintf(stderr, __VA_ARGS__)
9467 #define showlist(...) puts(#__VA_ARGS__)
9468 #define report(test, ...) ((test)?puts(#test):\
9469 printf(__VA_ARGS__))
9470 debug("Flag");
9471 debug("X = %d\n", x);
9472 showlist(The first, second, and third items.);
9474 </pre>
9475 results in
9476 <pre>
9477 fprintf(stderr, "Flag" );
9478 fprintf(stderr, "X = %d\n", x );
9479 puts( "The first, second, and third items." );
9481 printf("x is %d but y is %d", x, y));
9482 </pre>
9489 The string literal of a #line directive, if present, shall be a character string literal.
9492 The line number of the current source line is one greater than the number of new-line
9493 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
9494 file to the current token.
9496 A preprocessing directive of the form
9497 <pre>
9498 # line digit-sequence new-line
9499 </pre>
9500 causes the implementation to behave as if the following sequence of source lines begins
9501 with a source line that has a line number as specified by the digit sequence (interpreted as
9502 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
9503 2147483647.
9505 A preprocessing directive of the form
9506 <pre>
9507 # line digit-sequence "s-char-sequence<sub>opt</sub>" new-line
9508 </pre>
9509 sets the presumed line number similarly and changes the presumed name of the source
9510 file to be the contents of the character string literal.
9512 A preprocessing directive of the form
9513 <pre>
9514 # line pp-tokens new-line
9515 </pre>
9516 (that does not match one of the two previous forms) is permitted. The preprocessing
9517 tokens after line on the directive are processed just as in normal text (each identifier
9518 currently defined as a macro name is replaced by its replacement list of preprocessing
9519 tokens). The directive resulting after all replacements shall match one of the two
9520 previous forms and is then processed as appropriate.
9521 <!--page 191 -->
9527 A preprocessing directive of the form
9528 <pre>
9530 </pre>
9531 causes the implementation to produce a diagnostic message that includes the specified
9532 sequence of preprocessing tokens.
9538 A preprocessing directive of the form
9539 <pre>
9541 </pre>
9542 where the preprocessing token STDC does not immediately follow pragma in the
9543 directive (prior to any macro replacement)<sup><a href="#note174"><b>174)</b></a></sup> causes the implementation to behave in an
9544 implementation-defined manner. The behavior might cause translation to fail or cause the
9545 translator or the resulting program to behave in a non-conforming manner. Any such
9546 pragma that is not recognized by the implementation is ignored.
9548 If the preprocessing token STDC does immediately follow pragma in the directive (prior
9549 to any macro replacement), then no macro replacement is performed on the directive, and
9550 the directive shall have one of the following forms<sup><a href="#note175"><b>175)</b></a></sup> whose meanings are described
9551 elsewhere:
9552 <pre>
9553 #pragma STDC FP_CONTRACT on-off-switch
9554 #pragma STDC FENV_ACCESS on-off-switch
9555 #pragma STDC CX_LIMITED_RANGE on-off-switch
9556 on-off-switch: one of
9557 ON OFF DEFAULT
9558 </pre>
9559 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
9565 <!--page 192 -->
9568 <p><small><a name="note174" href="#note174">174)</a> An implementation is not required to perform macro replacement in pragmas, but it is permitted
9569 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
9570 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
9571 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
9572 but is not required to.
9573 </small>
9574 <p><small><a name="note175" href="#note175">175)</a> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
9575 </small>
9581 A preprocessing directive of the form
9582 <pre>
9583 # new-line
9584 </pre>
9585 has no effect.
9590 The values of the predefined macros listed in the following subclauses<sup><a href="#note176"><b>176)</b></a></sup> (except for
9591 __FILE__ and __LINE__) remain constant throughout the translation unit.
9593 None of these macro names, nor the identifier defined, shall be the subject of a
9594 #define or a #undef preprocessing directive. Any other predefined macro names
9595 shall begin with a leading underscore followed by an uppercase letter or a second
9596 underscore.
9598 The implementation shall not predefine the macro __cplusplus, nor shall it define it
9599 in any standard header.
9603 <p><small><a name="note176" href="#note176">176)</a> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
9604 </small>
9609 The following macro names shall be defined by the implementation:
9610 __DATE__ The date of translation of the preprocessing translation unit: a character
9611 <pre>
9612 string literal of the form "Mmm dd yyyy", where the names of the
9613 months are the same as those generated by the asctime function, and the
9614 first character of dd is a space character if the value is less than 10. If the
9615 date of translation is not available, an implementation-defined valid date
9616 shall be supplied.
9617 </pre>
9618 __FILE__ The presumed name of the current source file (a character string literal).<sup><a href="#note177"><b>177)</b></a></sup>
9619 __LINE__ The presumed line number (within the current source file) of the current
9620 <pre>
9622 </pre>
9623 __STDC__ The integer constant 1, intended to indicate a conforming implementation.
9624 __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
9625 <pre>
9626 implementation or the integer constant 0 if it is not.
9627 </pre>
9632 <!--page 193 -->
9634 __TIME__ The time of translation of the preprocessing translation unit: a character
9635 <pre>
9636 string literal of the form "hh:mm:ss" as in the time generated by the
9637 asctime function. If the time of translation is not available, an
9638 implementation-defined valid time shall be supplied.
9639 </pre>
9643 <p><small><a name="note177" href="#note177">177)</a> The presumed source file name and line number can be changed by the #line directive.
9644 </small>
9645 <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
9647 remain an integer constant of type long int that is increased with each revision of this International
9648 Standard.
9649 </small>
9654 The following macro names are conditionally defined by the implementation:
9655 __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
9656 <pre>
9657 199712L). If this symbol is defined, then every character in the Unicode
9658 required set, when stored in an object of type wchar_t, has the same
9659 value as the short identifier of that character. The Unicode required set
9660 consists of all the characters that are defined by ISO/IEC 10646, along with
9661 all amendments and technical corrigenda, as of the specified year and
9662 month. If some other encoding is used, the macro shall not be defined and
9663 the actual encoding used is implementation-defined.
9664 </pre>
9665 __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
9666 <pre>
9667 the encoding for wchar_t, a member of the basic character set need not
9668 have a code value equal to its value when used as the lone character in an
9669 integer character constant.
9670 </pre>
9671 __STDC_UTF_16__ The integer constant 1, intended to indicate that values of type
9672 <pre>
9673 char16_t are UTF-16 encoded. If some other encoding is used, the
9674 macro shall not be defined and the actual encoding used is implementation-
9675 defined.
9676 </pre>
9677 __STDC_UTF_32__ The integer constant 1, intended to indicate that values of type
9678 <pre>
9679 char32_t are UTF-32 encoded. If some other encoding is used, the
9680 macro shall not be defined and the actual encoding used is implementation-
9681 defined.
9682 </pre>
9683 <p><b> Forward references</b>: common definitions (<a href="#7.19">7.19</a>), unicode utilities (<a href="#7.27">7.27</a>).
9688 <!--page 194 -->
9693 The following macro names are conditionally defined by the implementation:
9694 __STDC_ANALYZABLE__ The integer constant 1, intended to indicate conformance to
9695 <pre>
9697 </pre>
9698 __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
9699 <pre>
9701 </pre>
9702 __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
9703 <pre>
9705 arithmetic).
9706 </pre>
9707 __STDC_LIB_EXT1__ The integer constant 201ymmL, intended to indicate support
9708 <pre>
9709 for the extensions defined in <a href="#K">annex K</a> (Bounds-checking interfaces).<sup><a href="#note179"><b>179)</b></a></sup>
9710 </pre>
9711 __STDC_NO_COMPLEX__ The integer constant 1, intended to indicate that the
9712 <pre>
9714 header.
9715 </pre>
9716 __STDC_NO_THREADS__ The integer constant 1, intended to indicate that the
9717 <pre>
9718 implementation does not support atomic types (including the _Atomic
9719 type qualifier and the <a href="#7.17"><stdatomic.h></a> header) or the <a href="#7.25"><threads.h></a>
9720 header.
9721 </pre>
9722 __STDC_NO_VLA__ The integer constant 1, intended to indicate that the
9723 <pre>
9724 implementation does not support variable length arrays or variably
9725 modified types.
9726 </pre>
9728 An implementation that defines __STDC_NO_COMPLEX__ shall not define
9729 __STDC_IEC_559_COMPLEX__.
9732 <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
9733 each revision of this International Standard.
9734 </small>
9740 A unary operator expression of the form:
9741 <pre>
9742 _Pragma ( string-literal )
9743 </pre>
9744 is processed as follows: The string literal is destringized by deleting the L prefix, if
9745 present, deleting the leading and trailing double-quotes, replacing each escape sequence
9746 \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
9747 resulting sequence of characters is processed through translation phase 3 to produce
9748 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
9751 <!--page 195 -->
9752 directive. The original four preprocessing tokens in the unary operator expression are
9753 removed.
9754 <p><!--para 2 -->
9755 EXAMPLE A directive of the form:
9756 <pre>
9758 </pre>
9759 can also be expressed as:
9760 <pre>
9762 </pre>
9763 The latter form is processed in the same way whether it appears literally as shown, or results from macro
9764 replacement, as in:
9765 <!--page 196 -->
9766 <pre>
9767 #define LISTING(x) PRAGMA(listing on #x)
9768 #define PRAGMA(x) _Pragma(#x)
9769 LISTING ( ..\listing.dir )
9770 </pre>
9777 <p><!--para 1 -->
9778 Future standardization may include additional floating-point types, including those with
9779 greater range, precision, or both than long double.
9783 <p><!--para 1 -->
9784 Declaring an identifier with internal linkage at file scope without the static storage-
9785 class specifier is an obsolescent feature.
9789 <p><!--para 1 -->
9790 Restriction of the significance of an external name to fewer than 255 characters
9791 (considering each universal character name or extended source character as a single
9792 character) is an obsolescent feature that is a concession to existing implementations.
9796 <p><!--para 1 -->
9797 Lowercase letters as escape sequences are reserved for future standardization. Other
9798 characters may be used in extensions.
9802 <p><!--para 1 -->
9803 The placement of a storage-class specifier other than at the beginning of the declaration
9804 specifiers in a declaration is an obsolescent feature.
9808 <p><!--para 1 -->
9809 The use of function declarators with empty parentheses (not prototype-format parameter
9810 type declarators) is an obsolescent feature.
9814 <p><!--para 1 -->
9815 The use of function definitions with separate parameter identifier and declaration lists
9816 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
9820 <p><!--para 1 -->
9821 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
9825 <p><!--para 1 -->
9826 Macro names beginning with __STDC_ are reserved for future standardization.
9827 <!--page 197 -->
9837 <p><!--para 1 -->
9838 A string is a contiguous sequence of characters terminated by and including the first null
9839 character. The term multibyte string is sometimes used instead to emphasize special
9840 processing given to multibyte characters contained in the string or to avoid confusion
9841 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
9842 character. The length of a string is the number of bytes preceding the null character and
9843 the value of a string is the sequence of the values of the contained characters, in order.
9844 <p><!--para 2 -->
9845 The decimal-point character is the character used by functions that convert floating-point
9846 numbers to or from character sequences to denote the beginning of the fractional part of
9847 such character sequences.<sup><a href="#note180"><b>180)</b></a></sup> It is represented in the text and examples by a period, but
9848 may be changed by the setlocale function.
9849 <p><!--para 3 -->
9850 A null wide character is a wide character with code value zero.
9851 <p><!--para 4 -->
9852 A wide string is a contiguous sequence of wide characters terminated by and including
9853 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
9854 addressed) wide character. The length of a wide string is the number of wide characters
9855 preceding the null wide character and the value of a wide string is the sequence of code
9856 values of the contained wide characters, in order.
9857 <p><!--para 5 -->
9858 A shift sequence is a contiguous sequence of bytes within a multibyte string that
9859 (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
9860 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
9862 <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>).
9867 <!--page 198 -->
9869 <p><b>Footnotes</b>
9870 <p><small><a name="note180" href="#note180">180)</a> The functions that make use of the decimal-point character are the numeric conversion functions
9871 (<a href="#7.22.1">7.22.1</a>, <a href="#7.28.4.1">7.28.4.1</a>) and the formatted input/output functions (<a href="#7.21.6">7.21.6</a>, <a href="#7.28.2">7.28.2</a>).
9872 </small>
9873 <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
9874 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
9875 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
9876 implementation's choice.
9877 </small>
9881 <p><!--para 1 -->
9882 Each library function is declared, with a type that includes a prototype, in a header,<sup><a href="#note182"><b>182)</b></a></sup>
9883 whose contents are made available by the #include preprocessing directive. The
9884 header declares a set of related functions, plus any necessary types and additional macros
9885 needed to facilitate their use. Declarations of types described in this clause shall not
9886 include type qualifiers, unless explicitly stated otherwise.
9887 <p><!--para 2 -->
9889 <pre>
9890 <a href="#7.2"><assert.h></a> <a href="#7.9"><iso646.h></a> <a href="#7.16"><stdarg.h></a> <a href="#7.23"><string.h></a>
9891 <a href="#7.3"><complex.h></a> <a href="#7.10"><limits.h></a> <a href="#7.17"><stdatomic.h></a> <a href="#7.24"><tgmath.h></a>
9892 <a href="#7.4"><ctype.h></a> <a href="#7.11"><locale.h></a> <a href="#7.18"><stdbool.h></a> <a href="#7.25"><threads.h></a>
9893 <a href="#7.5"><errno.h></a> <a href="#7.12"><math.h></a> <a href="#7.19"><stddef.h></a> <a href="#7.26"><time.h></a>
9894 <a href="#7.6"><fenv.h></a> <a href="#7.13"><setjmp.h></a> <a href="#7.20"><stdint.h></a> <a href="#7.27"><uchar.h></a>
9895 <a href="#7.7"><float.h></a> <a href="#7.14"><signal.h></a> <a href="#7.21"><stdio.h></a> <a href="#7.28"><wchar.h></a>
9896 <a href="#7.8"><inttypes.h></a> <a href="#7.15"><stdalign.h></a> <a href="#7.22"><stdlib.h></a> <a href="#7.29"><wctype.h></a>
9897 </pre>
9898 <p><!--para 3 -->
9899 If a file with the same name as one of the above < and > delimited sequences, not
9900 provided as part of the implementation, is placed in any of the standard places that are
9901 searched for included source files, the behavior is undefined.
9902 <p><!--para 4 -->
9903 Standard headers may be included in any order; each may be included more than once in
9904 a given scope, with no effect different from being included only once, except that the
9905 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
9906 used, a header shall be included outside of any external declaration or definition, and it
9907 shall first be included before the first reference to any of the functions or objects it
9908 declares, or to any of the types or macros it defines. However, if an identifier is declared
9909 or defined in more than one header, the second and subsequent associated headers may be
9910 included after the initial reference to the identifier. The program shall not have any
9911 macros with names lexically identical to keywords currently defined prior to the
9912 inclusion.
9913 <p><!--para 5 -->
9914 Any definition of an object-like macro described in this clause shall expand to code that is
9915 fully protected by parentheses where necessary, so that it groups in an arbitrary
9916 expression as if it were a single identifier.
9917 <p><!--para 6 -->
9918 Any declaration of a library function shall have external linkage.
9923 <!--page 199 -->
9924 <p><!--para 7 -->
9928 <p><b>Footnotes</b>
9929 <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
9930 necessarily valid source file names.
9931 </small>
9932 <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="#7.25"><threads.h></a> are conditional features that
9934 </small>
9938 <p><!--para 1 -->
9939 Each header declares or defines all identifiers listed in its associated subclause, and
9940 optionally declares or defines identifiers listed in its associated future library directions
9941 subclause and identifiers which are always reserved either for any use or for use as file
9942 scope identifiers.
9943 <ul>
9944 <li> All identifiers that begin with an underscore and either an uppercase letter or another
9945 underscore are always reserved for any use.
9946 <li> All identifiers that begin with an underscore are always reserved for use as identifiers
9947 with file scope in both the ordinary and tag name spaces.
9948 <li> Each macro name in any of the following subclauses (including the future library
9949 directions) is reserved for use as specified if any of its associated headers is included;
9951 <li> All identifiers with external linkage in any of the following subclauses (including the
9952 future library directions) and errno are always reserved for use as identifiers with
9954 <li> Each identifier with file scope listed in any of the following subclauses (including the
9955 future library directions) is reserved for use as a macro name and as an identifier with
9956 file scope in the same name space if any of its associated headers is included.
9957 </ul>
9958 <p><!--para 2 -->
9959 No other identifiers are reserved. If the program declares or defines an identifier in a
9960 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
9961 identifier as a macro name, the behavior is undefined.
9962 <p><!--para 3 -->
9963 If the program removes (with #undef) any macro definition of an identifier in the first
9964 group listed above, the behavior is undefined.
9969 <!--page 200 -->
9971 <p><b>Footnotes</b>
9972 <p><small><a name="note184" href="#note184">184)</a> The list of reserved identifiers with external linkage includes math_errhandling, setjmp,
9973 va_copy, and va_end.
9974 </small>
9978 <p><!--para 1 -->
9979 Each of the following statements applies unless explicitly stated otherwise in the detailed
9980 descriptions that follow: If an argument to a function has an invalid value (such as a value
9981 outside the domain of the function, or a pointer outside the address space of the program,
9982 or a null pointer, or a pointer to non-modifiable storage when the corresponding
9983 parameter is not const-qualified) or a type (after promotion) not expected by a function
9984 with variable number of arguments, the behavior is undefined. If a function argument is
9985 described as being an array, the pointer actually passed to the function shall have a value
9986 such that all address computations and accesses to objects (that would be valid if the
9987 pointer did point to the first element of such an array) are in fact valid. Any function
9988 declared in a header may be additionally implemented as a function-like macro defined in
9989 the header, so if a library function is declared explicitly when its header is included, one
9990 of the techniques shown below can be used to ensure the declaration is not affected by
9991 such a macro. Any macro definition of a function can be suppressed locally by enclosing
9992 the name of the function in parentheses, because the name is then not followed by the left
9993 parenthesis that indicates expansion of a macro function name. For the same syntactic
9994 reason, it is permitted to take the address of a library function even if it is also defined as
9995 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
9996 actual function is referred to. Any invocation of a library function that is implemented as
9997 a macro shall expand to code that evaluates each of its arguments exactly once, fully
9998 protected by parentheses where necessary, so it is generally safe to use arbitrary
9999 expressions as arguments.<sup><a href="#note186"><b>186)</b></a></sup> Likewise, those function-like macros described in the
10000 following subclauses may be invoked in an expression anywhere a function with a
10001 compatible return type could be called.<sup><a href="#note187"><b>187)</b></a></sup> All object-like macros listed as expanding to
10004 <!--page 201 -->
10005 integer constant expressions shall additionally be suitable for use in #if preprocessing
10006 directives.
10007 <p><!--para 2 -->
10008 Provided that a library function can be declared without reference to any type defined in a
10009 header, it is also permissible to declare the function and use it without including its
10010 associated header.
10011 <p><!--para 3 -->
10012 There is a sequence point immediately before a library function returns.
10013 <p><!--para 4 -->
10014 The functions in the standard library are not guaranteed to be reentrant and may modify
10016 <p><!--para 5 -->
10017 Unless explicitly stated otherwise in the detailed descriptions that follow, library
10018 functions shall prevent data races as follows: A library function shall not directly or
10019 indirectly access objects accessible by threads other than the current thread unless the
10020 objects are accessed directly or indirectly via the function's arguments. A library
10021 function shall not directly or indirectly modify objects accessible by threads other than
10022 the current thread unless the objects are accessed directly or indirectly via the function's
10023 non-const arguments.<sup><a href="#note189"><b>189)</b></a></sup> Implementations may share their own internal objects between
10024 threads if the objects are not visible to users and are protected against data races.
10025 <p><!--para 6 -->
10026 Unless otherwise specified, library functions shall perform all operations solely within the
10027 current thread if those operations have effects that are visible to users.<sup><a href="#note190"><b>190)</b></a></sup>
10028 <p><!--para 7 -->
10029 EXAMPLE The function atoi may be used in any of several ways:
10030 <ul>
10031 <li> by use of its associated header (possibly generating a macro expansion)
10032 <pre>
10034 const char *str;
10035 /* ... */
10036 i = atoi(str);
10037 </pre>
10038 <li> by use of its associated header (assuredly generating a true function reference)
10043 <!--page 202 -->
10044 <pre>
10046 #undef atoi
10047 const char *str;
10048 /* ... */
10049 i = atoi(str);
10050 </pre>
10051 or
10052 <pre>
10054 const char *str;
10055 /* ... */
10056 i = (atoi)(str);
10057 </pre>
10058 <li> by explicit declaration
10059 <!--page 203 -->
10060 <pre>
10061 extern int atoi(const char *);
10062 const char *str;
10063 /* ... */
10064 i = atoi(str);
10065 </pre>
10066 </ul>
10068 <p><b>Footnotes</b>
10069 <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
10070 also provides a macro for that function.
10071 </small>
10072 <p><small><a name="note186" href="#note186">186)</a> Such macros might not contain the sequence points that the corresponding function calls do.
10073 </small>
10074 <p><small><a name="note187" href="#note187">187)</a> Because external identifiers and some macro names beginning with an underscore are reserved,
10075 implementations may provide special semantics for such names. For example, the identifier
10076 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
10077 appropriate header could specify
10079 <pre>
10080 #define abs(x) _BUILTIN_abs(x)
10081 </pre>
10082 for a compiler whose code generator will accept it.
10083 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
10084 function may write
10086 <pre>
10087 #undef abs
10088 </pre>
10089 whether the implementation's header provides a macro implementation of abs or a built-in
10090 implementation. The prototype for the function, which precedes and is hidden by any macro
10091 definition, is thereby revealed also.
10092 </small>
10093 <p><small><a name="note188" href="#note188">188)</a> Thus, a signal handler cannot, in general, call standard library functions.
10094 </small>
10095 <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
10096 purposes without synchronization because it could cause a data race even in programs that do not
10097 explicitly share objects between threads.
10098 </small>
10099 <p><small><a name="note190" href="#note190">190)</a> This allows implementations to parallelize operations if there are no visible side effects.
10100 </small>
10104 <p><!--para 1 -->
10105 The header <a href="#7.2"><assert.h></a> defines the assert and static_assert macros and
10106 refers to another macro,
10107 <pre>
10108 NDEBUG
10109 </pre>
10110 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
10111 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
10112 simply as
10113 <pre>
10114 #define assert(ignore) ((void)0)
10115 </pre>
10116 The assert macro is redefined according to the current state of NDEBUG each time that
10118 <p><!--para 2 -->
10119 The assert macro shall be implemented as a macro, not as an actual function. If the
10120 macro definition is suppressed in order to access an actual function, the behavior is
10121 undefined.
10122 <p><!--para 3 -->
10123 The macro
10124 <pre>
10125 static_assert
10126 </pre>
10127 expands to _Static_assert.
10134 <p><b>Synopsis</b>
10135 <p><!--para 1 -->
10136 <pre>
10138 void assert(scalar expression);
10139 </pre>
10140 <p><b>Description</b>
10141 <p><!--para 2 -->
10142 The assert macro puts diagnostic tests into programs; it expands to a void expression.
10143 When it is executed, if expression (which shall have a scalar type) is false (that is,
10144 compares equal to 0), the assert macro writes information about the particular call that
10145 failed (including the text of the argument, the name of the source file, the source line
10146 number, and the name of the enclosing function -- the latter are respectively the values of
10147 the preprocessing macros __FILE__ and __LINE__ and of the identifier
10148 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note191"><b>191)</b></a></sup> It
10149 then calls the abort function.
10153 <!--page 204 -->
10154 <p><b>Returns</b>
10155 <p><!--para 3 -->
10156 The assert macro returns no value.
10158 <!--page 205 -->
10160 <p><b>Footnotes</b>
10161 <p><small><a name="note191" href="#note191">191)</a> The message written might be of the form:
10162 Assertion failed: expression, function abc, file xyz, line nnn.
10163 </small>
10170 <p><!--para 1 -->
10171 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
10173 <p><!--para 2 -->
10174 Implementations that define the macro __STDC_NO_COMPLEX__ need not provide
10175 this header nor support any of its facilities.
10176 <p><!--para 3 -->
10177 Each synopsis specifies a family of functions consisting of a principal function with one
10178 or more double complex parameters and a double complex or double return
10179 value; and other functions with the same name but with f and l suffixes which are
10180 corresponding functions with float and long double parameters and return values.
10181 <p><!--para 4 -->
10182 The macro
10183 <pre>
10184 complex
10185 </pre>
10186 expands to _Complex; the macro
10187 <pre>
10188 _Complex_I
10189 </pre>
10190 expands to a constant expression of type const float _Complex, with the value of
10192 <p><!--para 5 -->
10193 The macros
10194 <pre>
10195 imaginary
10196 </pre>
10197 and
10198 <pre>
10199 _Imaginary_I
10200 </pre>
10201 are defined if and only if the implementation supports imaginary types;<sup><a href="#note194"><b>194)</b></a></sup> if defined,
10202 they expand to _Imaginary and a constant expression of type const float
10203 _Imaginary with the value of the imaginary unit.
10204 <p><!--para 6 -->
10205 The macro
10206 <pre>
10207 I
10208 </pre>
10209 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
10210 defined, I shall expand to _Complex_I.
10211 <p><!--para 7 -->
10212 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
10213 redefine the macros complex, imaginary, and I.
10215 <!--page 206 -->
10216 <p><b> Forward references</b>: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
10218 <p><b>Footnotes</b>
10219 <p><small><a name="note192" href="#note192">192)</a> See ''future library directions'' (<a href="#7.30.1">7.30.1</a>).
10220 </small>
10221 <p><small><a name="note193" href="#note193">193)</a> The imaginary unit is a number i such that i 2 = -1.
10222 </small>
10223 <p><small><a name="note194" href="#note194">194)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
10224 </small>
10228 <p><!--para 1 -->
10229 Values are interpreted as radians, not degrees. An implementation may set errno but is
10230 not required to.
10234 <p><!--para 1 -->
10235 Some of the functions below have branch cuts, across which the function is
10236 discontinuous. For implementations with a signed zero (including all IEC 60559
10237 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
10238 one side of a cut from another so the function is continuous (except for format
10239 limitations) as the cut is approached from either side. For example, for the square root
10240 function, which has a branch cut along the negative real axis, the top of the cut, with
10241 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
10242 imaginary part -0, maps to the negative imaginary axis.
10243 <p><!--para 2 -->
10244 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
10245 sides of branch cuts. These implementations shall map a cut so the function is continuous
10246 as the cut is approached coming around the finite endpoint of the cut in a counter
10247 clockwise direction. (Branch cuts for the functions specified here have just one finite
10248 endpoint.) For example, for the square root function, coming counter clockwise around
10249 the finite endpoint of the cut along the negative real axis approaches the cut from above,
10250 so the cut maps to the positive imaginary axis.
10254 <p><b>Synopsis</b>
10255 <p><!--para 1 -->
10256 <pre>
10258 #pragma STDC CX_LIMITED_RANGE on-off-switch
10259 </pre>
10260 <p><b>Description</b>
10261 <p><!--para 2 -->
10262 The usual mathematical formulas for complex multiply, divide, and absolute value are
10263 problematic because of their treatment of infinities and because of undue overflow and
10264 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
10265 implementation that (where the state is ''on'') the usual mathematical formulas are
10266 acceptable.<sup><a href="#note195"><b>195)</b></a></sup> The pragma can occur either outside external declarations or preceding all
10267 explicit declarations and statements inside a compound statement. When outside external
10268 declarations, the pragma takes effect from its occurrence until another
10269 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
10270 When inside a compound statement, the pragma takes effect from its occurrence until
10271 another CX_LIMITED_RANGE pragma is encountered (including within a nested
10272 compound statement), or until the end of the compound statement; at the end of a
10273 compound statement the state for the pragma is restored to its condition just before the
10274 <!--page 207 -->
10275 compound statement. If this pragma is used in any other context, the behavior is
10276 undefined. The default state for the pragma is ''off''.
10278 <p><b>Footnotes</b>
10279 <p><small><a name="note195" href="#note195">195)</a> The purpose of the pragma is to allow the implementation to use the formulas:
10281 <pre>
10282 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
10283 (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
10284 | x + iy | = (sqrt) x 2 + y 2
10285 -----
10286 </pre>
10287 where the programmer can determine they are safe.
10288 </small>
10295 <p><b>Synopsis</b>
10296 <p><!--para 1 -->
10297 <pre>
10299 double complex cacos(double complex z);
10300 float complex cacosf(float complex z);
10301 long double complex cacosl(long double complex z);
10302 </pre>
10303 <p><b>Description</b>
10304 <p><!--para 2 -->
10305 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
10306 interval [-1, +1] along the real axis.
10307 <p><b>Returns</b>
10308 <p><!--para 3 -->
10309 The cacos functions return the complex arc cosine value, in the range of a strip
10310 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
10311 real axis.
10315 <p><b>Synopsis</b>
10316 <p><!--para 1 -->
10317 <pre>
10319 double complex casin(double complex z);
10320 float complex casinf(float complex z);
10321 long double complex casinl(long double complex z);
10322 </pre>
10323 <p><b>Description</b>
10324 <p><!--para 2 -->
10325 The casin functions compute the complex arc sine of z, with branch cuts outside the
10326 interval [-1, +1] along the real axis.
10327 <p><b>Returns</b>
10328 <p><!--para 3 -->
10329 The casin functions return the complex arc sine value, in the range of a strip
10330 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
10332 <!--page 208 -->
10333 along the real axis.
10337 <p><b>Synopsis</b>
10338 <p><!--para 1 -->
10339 <pre>
10341 double complex catan(double complex z);
10342 float complex catanf(float complex z);
10343 long double complex catanl(long double complex z);
10344 </pre>
10345 <p><b>Description</b>
10346 <p><!--para 2 -->
10347 The catan functions compute the complex arc tangent of z, with branch cuts outside the
10348 interval [-i, +i] along the imaginary axis.
10349 <p><b>Returns</b>
10350 <p><!--para 3 -->
10351 The catan functions return the complex arc tangent value, in the range of a strip
10352 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
10353 along the real axis.
10357 <p><b>Synopsis</b>
10358 <p><!--para 1 -->
10359 <pre>
10361 double complex ccos(double complex z);
10362 float complex ccosf(float complex z);
10363 long double complex ccosl(long double complex z);
10364 </pre>
10365 <p><b>Description</b>
10366 <p><!--para 2 -->
10367 The ccos functions compute the complex cosine of z.
10368 <p><b>Returns</b>
10369 <p><!--para 3 -->
10370 The ccos functions return the complex cosine value.
10374 <p><b>Synopsis</b>
10375 <p><!--para 1 -->
10376 <pre>
10378 double complex csin(double complex z);
10379 float complex csinf(float complex z);
10380 long double complex csinl(long double complex z);
10381 </pre>
10382 <p><b>Description</b>
10383 <p><!--para 2 -->
10384 The csin functions compute the complex sine of z.
10385 <!--page 209 -->
10386 <p><b>Returns</b>
10387 <p><!--para 3 -->
10388 The csin functions return the complex sine value.
10392 <p><b>Synopsis</b>
10393 <p><!--para 1 -->
10394 <pre>
10396 double complex ctan(double complex z);
10397 float complex ctanf(float complex z);
10398 long double complex ctanl(long double complex z);
10399 </pre>
10400 <p><b>Description</b>
10401 <p><!--para 2 -->
10402 The ctan functions compute the complex tangent of z.
10403 <p><b>Returns</b>
10404 <p><!--para 3 -->
10405 The ctan functions return the complex tangent value.
10412 <p><b>Synopsis</b>
10413 <p><!--para 1 -->
10414 <pre>
10416 double complex cacosh(double complex z);
10417 float complex cacoshf(float complex z);
10418 long double complex cacoshl(long double complex z);
10419 </pre>
10420 <p><b>Description</b>
10421 <p><!--para 2 -->
10422 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
10423 cut at values less than 1 along the real axis.
10424 <p><b>Returns</b>
10425 <p><!--para 3 -->
10426 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
10427 half-strip of nonnegative values along the real axis and in the interval [-ipi , +ipi ] along the
10428 imaginary axis.
10432 <p><b>Synopsis</b>
10433 <p><!--para 1 -->
10434 <!--page 210 -->
10435 <pre>
10437 double complex casinh(double complex z);
10438 float complex casinhf(float complex z);
10439 long double complex casinhl(long double complex z);
10440 </pre>
10441 <p><b>Description</b>
10442 <p><!--para 2 -->
10443 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
10444 outside the interval [-i, +i] along the imaginary axis.
10445 <p><b>Returns</b>
10446 <p><!--para 3 -->
10447 The casinh functions return the complex arc hyperbolic sine value, in the range of a
10448 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
10449 along the imaginary axis.
10453 <p><b>Synopsis</b>
10454 <p><!--para 1 -->
10455 <pre>
10457 double complex catanh(double complex z);
10458 float complex catanhf(float complex z);
10459 long double complex catanhl(long double complex z);
10460 </pre>
10461 <p><b>Description</b>
10462 <p><!--para 2 -->
10463 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
10464 cuts outside the interval [-1, +1] along the real axis.
10465 <p><b>Returns</b>
10466 <p><!--para 3 -->
10467 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
10468 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
10469 along the imaginary axis.
10473 <p><b>Synopsis</b>
10474 <p><!--para 1 -->
10475 <pre>
10477 double complex ccosh(double complex z);
10478 float complex ccoshf(float complex z);
10479 long double complex ccoshl(long double complex z);
10480 </pre>
10481 <p><b>Description</b>
10482 <p><!--para 2 -->
10483 The ccosh functions compute the complex hyperbolic cosine of z.
10484 <p><b>Returns</b>
10485 <p><!--para 3 -->
10486 The ccosh functions return the complex hyperbolic cosine value.
10487 <!--page 211 -->
10491 <p><b>Synopsis</b>
10492 <p><!--para 1 -->
10493 <pre>
10495 double complex csinh(double complex z);
10496 float complex csinhf(float complex z);
10497 long double complex csinhl(long double complex z);
10498 </pre>
10499 <p><b>Description</b>
10500 <p><!--para 2 -->
10501 The csinh functions compute the complex hyperbolic sine of z.
10502 <p><b>Returns</b>
10503 <p><!--para 3 -->
10504 The csinh functions return the complex hyperbolic sine value.
10508 <p><b>Synopsis</b>
10509 <p><!--para 1 -->
10510 <pre>
10512 double complex ctanh(double complex z);
10513 float complex ctanhf(float complex z);
10514 long double complex ctanhl(long double complex z);
10515 </pre>
10516 <p><b>Description</b>
10517 <p><!--para 2 -->
10518 The ctanh functions compute the complex hyperbolic tangent of z.
10519 <p><b>Returns</b>
10520 <p><!--para 3 -->
10521 The ctanh functions return the complex hyperbolic tangent value.
10528 <p><b>Synopsis</b>
10529 <p><!--para 1 -->
10530 <pre>
10532 double complex cexp(double complex z);
10533 float complex cexpf(float complex z);
10534 long double complex cexpl(long double complex z);
10535 </pre>
10536 <p><b>Description</b>
10537 <p><!--para 2 -->
10538 The cexp functions compute the complex base-e exponential of z.
10539 <p><b>Returns</b>
10540 <p><!--para 3 -->
10541 The cexp functions return the complex base-e exponential value.
10542 <!--page 212 -->
10546 <p><b>Synopsis</b>
10547 <p><!--para 1 -->
10548 <pre>
10550 double complex clog(double complex z);
10551 float complex clogf(float complex z);
10552 long double complex clogl(long double complex z);
10553 </pre>
10554 <p><b>Description</b>
10555 <p><!--para 2 -->
10556 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
10557 cut along the negative real axis.
10558 <p><b>Returns</b>
10559 <p><!--para 3 -->
10560 The clog functions return the complex natural logarithm value, in the range of a strip
10561 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
10562 imaginary axis.
10569 <p><b>Synopsis</b>
10570 <p><!--para 1 -->
10571 <pre>
10573 double cabs(double complex z);
10574 float cabsf(float complex z);
10575 long double cabsl(long double complex z);
10576 </pre>
10577 <p><b>Description</b>
10578 <p><!--para 2 -->
10579 The cabs functions compute the complex absolute value (also called norm, modulus, or
10580 magnitude) of z.
10581 <p><b>Returns</b>
10582 <p><!--para 3 -->
10583 The cabs functions return the complex absolute value.
10587 <p><b>Synopsis</b>
10588 <p><!--para 1 -->
10589 <!--page 213 -->
10590 <pre>
10592 double complex cpow(double complex x, double complex y);
10593 float complex cpowf(float complex x, float complex y);
10594 long double complex cpowl(long double complex x,
10595 long double complex y);
10596 </pre>
10597 <p><b>Description</b>
10598 <p><!--para 2 -->
10599 The cpow functions compute the complex power function xy , with a branch cut for the
10600 first parameter along the negative real axis.
10601 <p><b>Returns</b>
10602 <p><!--para 3 -->
10603 The cpow functions return the complex power function value.
10607 <p><b>Synopsis</b>
10608 <p><!--para 1 -->
10609 <pre>
10611 double complex csqrt(double complex z);
10612 float complex csqrtf(float complex z);
10613 long double complex csqrtl(long double complex z);
10614 </pre>
10615 <p><b>Description</b>
10616 <p><!--para 2 -->
10617 The csqrt functions compute the complex square root of z, with a branch cut along the
10618 negative real axis.
10619 <p><b>Returns</b>
10620 <p><!--para 3 -->
10621 The csqrt functions return the complex square root value, in the range of the right half-
10622 plane (including the imaginary axis).
10629 <p><b>Synopsis</b>
10630 <p><!--para 1 -->
10631 <pre>
10633 double carg(double complex z);
10634 float cargf(float complex z);
10635 long double cargl(long double complex z);
10636 </pre>
10637 <p><b>Description</b>
10638 <p><!--para 2 -->
10639 The carg functions compute the argument (also called phase angle) of z, with a branch
10640 cut along the negative real axis.
10641 <p><b>Returns</b>
10642 <p><!--para 3 -->
10643 The carg functions return the value of the argument in the interval [-pi , +pi ].
10644 <!--page 214 -->
10648 <p><b>Synopsis</b>
10649 <p><!--para 1 -->
10650 <pre>
10652 double cimag(double complex z);
10653 float cimagf(float complex z);
10654 long double cimagl(long double complex z);
10655 </pre>
10656 <p><b>Description</b>
10657 <p><!--para 2 -->
10658 The cimag functions compute the imaginary part of z.<sup><a href="#note196"><b>196)</b></a></sup>
10659 <p><b>Returns</b>
10660 <p><!--para 3 -->
10661 The cimag functions return the imaginary part value (as a real).
10663 <p><b>Footnotes</b>
10664 <p><small><a name="note196" href="#note196">196)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
10665 </small>
10669 <p><b>Synopsis</b>
10670 <p><!--para 1 -->
10671 <pre>
10673 double complex CMPLX(double x, double y);
10674 float complex CMPLXF(float x, float y);
10675 long double complex CMPLXL(long double x, long double y);
10676 </pre>
10677 <p><b>Description</b>
10678 <p><!--para 2 -->
10679 The CMPLX macros expand to an expression of the specified complex type, with the real
10680 part having the (converted) value of x and the imaginary part having the (converted)
10681 value of y.
10682 <p><b>Recommended practice</b>
10683 <p><!--para 3 -->
10684 The resulting expression should be suitable for use as an initializer for an object with
10685 static or thread storage duration, provided both arguments are likewise suitable.
10686 <p><b>Returns</b>
10687 <p><!--para 4 -->
10688 The CMPLX macros return the complex value x + i y.
10689 <p><!--para 5 -->
10690 NOTE These macros act as if the implementation supported imaginary types and the definitions were:
10691 <pre>
10692 #define CMPLX(x, y) ((double complex)((double)(x) + \
10693 _Imaginary_I * (double)(y)))
10694 #define CMPLXF(x, y) ((float complex)((float)(x) + \
10695 _Imaginary_I * (float)(y)))
10696 #define CMPLXL(x, y) ((long double complex)((long double)(x) + \
10697 _Imaginary_I * (long double)(y)))
10698 </pre>
10703 <!--page 215 -->
10707 <p><b>Synopsis</b>
10708 <p><!--para 1 -->
10709 <pre>
10711 double complex conj(double complex z);
10712 float complex conjf(float complex z);
10713 long double complex conjl(long double complex z);
10714 </pre>
10715 <p><b>Description</b>
10716 <p><!--para 2 -->
10717 The conj functions compute the complex conjugate of z, by reversing the sign of its
10718 imaginary part.
10719 <p><b>Returns</b>
10720 <p><!--para 3 -->
10721 The conj functions return the complex conjugate value.
10725 <p><b>Synopsis</b>
10726 <p><!--para 1 -->
10727 <pre>
10729 double complex cproj(double complex z);
10730 float complex cprojf(float complex z);
10731 long double complex cprojl(long double complex z);
10732 </pre>
10733 <p><b>Description</b>
10734 <p><!--para 2 -->
10735 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
10736 z except that all complex infinities (even those with one infinite part and one NaN part)
10737 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
10738 equivalent to
10739 <pre>
10740 INFINITY + I * copysign(0.0, cimag(z))
10741 </pre>
10742 <p><b>Returns</b>
10743 <p><!--para 3 -->
10744 The cproj functions return the value of the projection onto the Riemann sphere.
10748 <p><b>Synopsis</b>
10749 <p><!--para 1 -->
10750 <pre>
10752 double creal(double complex z);
10753 float crealf(float complex z);
10754 long double creall(long double complex z);
10755 </pre>
10756 <p><b>Description</b>
10757 <p><!--para 2 -->
10759 <!--page 216 -->
10760 <p><b>Returns</b>
10761 <p><!--para 3 -->
10762 The creal functions return the real part value.
10767 <!--page 217 -->
10769 <p><b>Footnotes</b>
10770 <p><small><a name="note197" href="#note197">197)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
10771 </small>
10775 <p><!--para 1 -->
10776 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
10777 characters.<sup><a href="#note198"><b>198)</b></a></sup> In all cases the argument is an int, the value of which shall be
10778 representable as an unsigned char or shall equal the value of the macro EOF. If the
10779 argument has any other value, the behavior is undefined.
10780 <p><!--para 2 -->
10781 The behavior of these functions is affected by the current locale. Those functions that
10783 <p><!--para 3 -->
10784 The term printing character refers to a member of a locale-specific set of characters, each
10785 of which occupies one printing position on a display device; the term control character
10786 refers to a member of a locale-specific set of characters that are not printing
10787 characters.<sup><a href="#note199"><b>199)</b></a></sup> All letters and digits are printing characters.
10788 <p><b> Forward references</b>: EOF (<a href="#7.21.1">7.21.1</a>), localization (<a href="#7.11">7.11</a>).
10790 <p><b>Footnotes</b>
10791 <p><small><a name="note198" href="#note198">198)</a> See ''future library directions'' (<a href="#7.30.2">7.30.2</a>).
10792 </small>
10793 <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
10794 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
10795 values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
10796 </small>
10800 <p><!--para 1 -->
10801 The functions in this subclause return nonzero (true) if and only if the value of the
10802 argument c conforms to that in the description of the function.
10806 <p><b>Synopsis</b>
10807 <p><!--para 1 -->
10808 <pre>
10810 int isalnum(int c);
10811 </pre>
10812 <p><b>Description</b>
10813 <p><!--para 2 -->
10814 The isalnum function tests for any character for which isalpha or isdigit is true.
10818 <p><b>Synopsis</b>
10819 <p><!--para 1 -->
10820 <pre>
10822 int isalpha(int c);
10823 </pre>
10824 <p><b>Description</b>
10825 <p><!--para 2 -->
10826 The isalpha function tests for any character for which isupper or islower is true,
10827 or any character that is one of a locale-specific set of alphabetic characters for which
10831 <!--page 218 -->
10832 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note200"><b>200)</b></a></sup> In the "C" locale,
10833 isalpha returns true only for the characters for which isupper or islower is true.
10835 <p><b>Footnotes</b>
10836 <p><small><a name="note200" href="#note200">200)</a> The functions islower and isupper test true or false separately for each of these additional
10837 characters; all four combinations are possible.
10838 </small>
10842 <p><b>Synopsis</b>
10843 <p><!--para 1 -->
10844 <pre>
10846 int isblank(int c);
10847 </pre>
10848 <p><b>Description</b>
10849 <p><!--para 2 -->
10850 The isblank function tests for any character that is a standard blank character or is one
10851 of a locale-specific set of characters for which isspace is true and that is used to
10852 separate words within a line of text. The standard blank characters are the following:
10854 for the standard blank characters.
10858 <p><b>Synopsis</b>
10859 <p><!--para 1 -->
10860 <pre>
10862 int iscntrl(int c);
10863 </pre>
10864 <p><b>Description</b>
10865 <p><!--para 2 -->
10866 The iscntrl function tests for any control character.
10870 <p><b>Synopsis</b>
10871 <p><!--para 1 -->
10872 <pre>
10874 int isdigit(int c);
10875 </pre>
10876 <p><b>Description</b>
10877 <p><!--para 2 -->
10878 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
10882 <p><b>Synopsis</b>
10883 <p><!--para 1 -->
10884 <pre>
10886 int isgraph(int c);
10887 </pre>
10892 <!--page 219 -->
10893 <p><b>Description</b>
10894 <p><!--para 2 -->
10895 The isgraph function tests for any printing character except space (' ').
10899 <p><b>Synopsis</b>
10900 <p><!--para 1 -->
10901 <pre>
10903 int islower(int c);
10904 </pre>
10905 <p><b>Description</b>
10906 <p><!--para 2 -->
10907 The islower function tests for any character that is a lowercase letter or is one of a
10908 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
10914 <p><b>Synopsis</b>
10915 <p><!--para 1 -->
10916 <pre>
10918 int isprint(int c);
10919 </pre>
10920 <p><b>Description</b>
10921 <p><!--para 2 -->
10922 The isprint function tests for any printing character including space (' ').
10926 <p><b>Synopsis</b>
10927 <p><!--para 1 -->
10928 <pre>
10930 int ispunct(int c);
10931 </pre>
10932 <p><b>Description</b>
10933 <p><!--para 2 -->
10934 The ispunct function tests for any printing character that is one of a locale-specific set
10936 locale, ispunct returns true for every printing character for which neither isspace
10937 nor isalnum is true.
10941 <p><b>Synopsis</b>
10942 <p><!--para 1 -->
10943 <pre>
10945 int isspace(int c);
10946 </pre>
10947 <p><b>Description</b>
10948 <p><!--para 2 -->
10949 The isspace function tests for any character that is a standard white-space character or
10950 is one of a locale-specific set of characters for which isalnum is false. The standard
10951 <!--page 220 -->
10952 white-space characters are the following: space (' '), form feed ('\f'), new-line
10953 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
10958 <p><b>Synopsis</b>
10959 <p><!--para 1 -->
10960 <pre>
10962 int isupper(int c);
10963 </pre>
10964 <p><b>Description</b>
10965 <p><!--para 2 -->
10966 The isupper function tests for any character that is an uppercase letter or is one of a
10967 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
10973 <p><b>Synopsis</b>
10974 <p><!--para 1 -->
10975 <pre>
10977 int isxdigit(int c);
10978 </pre>
10979 <p><b>Description</b>
10980 <p><!--para 2 -->
10981 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
10988 <p><b>Synopsis</b>
10989 <p><!--para 1 -->
10990 <pre>
10992 int tolower(int c);
10993 </pre>
10994 <p><b>Description</b>
10995 <p><!--para 2 -->
10996 The tolower function converts an uppercase letter to a corresponding lowercase letter.
10997 <p><b>Returns</b>
10998 <p><!--para 3 -->
10999 If the argument is a character for which isupper is true and there are one or more
11000 corresponding characters, as specified by the current locale, for which islower is true,
11001 the tolower function returns one of the corresponding characters (always the same one
11002 for any given locale); otherwise, the argument is returned unchanged.
11003 <!--page 221 -->
11007 <p><b>Synopsis</b>
11008 <p><!--para 1 -->
11009 <pre>
11011 int toupper(int c);
11012 </pre>
11013 <p><b>Description</b>
11014 <p><!--para 2 -->
11015 The toupper function converts a lowercase letter to a corresponding uppercase letter.
11016 <p><b>Returns</b>
11017 <p><!--para 3 -->
11018 If the argument is a character for which islower is true and there are one or more
11019 corresponding characters, as specified by the current locale, for which isupper is true,
11020 the toupper function returns one of the corresponding characters (always the same one
11021 for any given locale); otherwise, the argument is returned unchanged.
11022 <!--page 222 -->
11026 <p><!--para 1 -->
11027 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
11028 conditions.
11029 <p><!--para 2 -->
11030 The macros are
11031 <pre>
11032 EDOM
11033 EILSEQ
11034 ERANGE
11035 </pre>
11036 which expand to integer constant expressions with type int, distinct positive values, and
11037 which are suitable for use in #if preprocessing directives; and
11038 <pre>
11039 errno
11040 </pre>
11041 which expands to a modifiable lvalue<sup><a href="#note201"><b>201)</b></a></sup> that has type int and thread local storage
11042 duration, the value of which is set to a positive error number by several library functions.
11043 If a macro definition is suppressed in order to access an actual object, or a program
11044 defines an identifier with the name errno, the behavior is undefined.
11045 <p><!--para 3 -->
11046 The value of errno in the initial thread is zero at program startup (the initial value of
11047 errno in other threads is an indeterminate value), but is never set to zero by any library
11048 function.<sup><a href="#note202"><b>202)</b></a></sup> The value of errno may be set to nonzero by a library function call
11049 whether or not there is an error, provided the use of errno is not documented in the
11050 description of the function in this International Standard.
11051 <p><!--para 4 -->
11052 Additional macro definitions, beginning with E and a digit or E and an uppercase
11053 letter,<sup><a href="#note203"><b>203)</b></a></sup> may also be specified by the implementation.
11058 <!--page 223 -->
11060 <p><b>Footnotes</b>
11061 <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
11062 resulting from a function call (for example, *errno()).
11063 </small>
11064 <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,
11065 then inspect it before a subsequent library function call. Of course, a library function can save the
11066 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
11067 value is still zero just before the return.
11068 </small>
11069 <p><small><a name="note203" href="#note203">203)</a> See ''future library directions'' (<a href="#7.30.3">7.30.3</a>).
11070 </small>
11074 <p><!--para 1 -->
11075 The header <a href="#7.6"><fenv.h></a> defines several macros, and declares types and functions that
11076 provide access to the floating-point environment. The floating-point environment refers
11077 collectively to any floating-point status flags and control modes supported by the
11078 implementation.<sup><a href="#note204"><b>204)</b></a></sup> A floating-point status flag is a system variable whose value is set
11079 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
11080 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note205"><b>205)</b></a></sup> A floating-
11081 point control mode is a system variable whose value may be set by the user to affect the
11082 subsequent behavior of floating-point arithmetic.
11083 <p><!--para 2 -->
11084 The floating-point environment has thread storage duration. The initial state for a
11085 thread's floating-point environment is the current state of the floating-point environment
11086 of the thread that creates it at the time of creation.
11087 <p><!--para 3 -->
11088 Certain programming conventions support the intended model of use for the floating-
11090 <ul>
11091 <li> a function call does not alter its caller's floating-point control modes, clear its caller's
11092 floating-point status flags, nor depend on the state of its caller's floating-point status
11093 flags unless the function is so documented;
11094 <li> a function call is assumed to require default floating-point control modes, unless its
11095 documentation promises otherwise;
11096 <li> a function call is assumed to have the potential for raising floating-point exceptions,
11097 unless its documentation promises otherwise.
11098 </ul>
11099 <p><!--para 4 -->
11100 The type
11101 <pre>
11102 fenv_t
11103 </pre>
11104 represents the entire floating-point environment.
11105 <p><!--para 5 -->
11106 The type
11107 <pre>
11108 fexcept_t
11109 </pre>
11110 represents the floating-point status flags collectively, including any status the
11111 implementation associates with the flags.
11114 <!--page 224 -->
11115 <p><!--para 6 -->
11116 Each of the macros
11117 <pre>
11118 FE_DIVBYZERO
11119 FE_INEXACT
11120 FE_INVALID
11121 FE_OVERFLOW
11122 FE_UNDERFLOW
11123 </pre>
11124 is defined if and only if the implementation supports the floating-point exception by
11125 means of the functions in 7.6.2.<sup><a href="#note207"><b>207)</b></a></sup> Additional implementation-defined floating-point
11126 exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
11127 be specified by the implementation. The defined macros expand to integer constant
11128 expressions with values such that bitwise ORs of all combinations of the macros result in
11129 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
11131 <p><!--para 7 -->
11132 The macro
11133 <pre>
11134 FE_ALL_EXCEPT
11135 </pre>
11136 is simply the bitwise OR of all floating-point exception macros defined by the
11137 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
11138 <p><!--para 8 -->
11139 Each of the macros
11140 <pre>
11141 FE_DOWNWARD
11142 FE_TONEAREST
11143 FE_TOWARDZERO
11144 FE_UPWARD
11145 </pre>
11146 is defined if and only if the implementation supports getting and setting the represented
11147 rounding direction by means of the fegetround and fesetround functions.
11148 Additional implementation-defined rounding directions, with macro definitions beginning
11149 with FE_ and an uppercase letter, may also be specified by the implementation. The
11150 defined macros expand to integer constant expressions whose values are distinct
11152 <p><!--para 9 -->
11153 The macro
11157 <!--page 225 -->
11158 <pre>
11159 FE_DFL_ENV
11160 </pre>
11161 represents the default floating-point environment -- the one installed at program startup
11162 <ul>
11163 <li> and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
11164 </ul>
11166 <p><!--para 10 -->
11167 Additional implementation-defined environments, with macro definitions beginning with
11168 FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
11169 also be specified by the implementation.
11171 <p><b>Footnotes</b>
11172 <p><small><a name="note204" href="#note204">204)</a> This header is designed to support the floating-point exception status flags and directed-rounding
11173 control modes required by IEC 60559, and other similar floating-point state information. It is also
11174 designed to facilitate code portability among all systems.
11175 </small>
11176 <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.
11177 </small>
11178 <p><small><a name="note206" href="#note206">206)</a> With these conventions, a programmer can safely assume default floating-point control modes (or be
11179 unaware of them). The responsibilities associated with accessing the floating-point environment fall
11180 on the programmer or program that does so explicitly.
11181 </small>
11182 <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
11183 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
11184 necessary for all the functions to succeed all the time.
11185 </small>
11186 <p><small><a name="note208" href="#note208">208)</a> The macros should be distinct powers of two.
11187 </small>
11188 <p><small><a name="note209" href="#note209">209)</a> Even though the rounding direction macros may expand to constants corresponding to the values of
11189 FLT_ROUNDS, they are not required to do so.
11190 </small>
11194 <p><b>Synopsis</b>
11195 <p><!--para 1 -->
11196 <pre>
11198 #pragma STDC FENV_ACCESS on-off-switch
11199 </pre>
11200 <p><b>Description</b>
11201 <p><!--para 2 -->
11202 The FENV_ACCESS pragma provides a means to inform the implementation when a
11203 program might access the floating-point environment to test floating-point status flags or
11204 run under non-default floating-point control modes.<sup><a href="#note210"><b>210)</b></a></sup> The pragma shall occur either
11205 outside external declarations or preceding all explicit declarations and statements inside a
11206 compound statement. When outside external declarations, the pragma takes effect from
11207 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
11208 the translation unit. When inside a compound statement, the pragma takes effect from its
11209 occurrence until another FENV_ACCESS pragma is encountered (including within a
11210 nested compound statement), or until the end of the compound statement; at the end of a
11211 compound statement the state for the pragma is restored to its condition just before the
11212 compound statement. If this pragma is used in any other context, the behavior is
11213 undefined. If part of a program tests floating-point status flags, sets floating-point control
11214 modes, or runs under non-default mode settings, but was translated with the state for the
11215 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
11216 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
11217 the program translated with FENV_ACCESS ''off'' to a part translated with
11218 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
11219 floating-point control modes have their default settings.)
11224 <!--page 226 -->
11225 <p><!--para 3 -->
11226 EXAMPLE
11227 <pre>
11229 void f(double x)
11230 {
11231 #pragma STDC FENV_ACCESS ON
11232 void g(double);
11233 void h(double);
11234 /* ... */
11235 g(x + 1);
11236 h(x + 1);
11237 /* ... */
11238 }
11239 </pre>
11240 <p><!--para 4 -->
11241 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
11242 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
11243 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note211"><b>211)</b></a></sup>
11246 <p><b>Footnotes</b>
11247 <p><small><a name="note210" href="#note210">210)</a> The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
11248 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
11249 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
11250 modes are in effect and the flags are not tested.
11251 </small>
11252 <p><small><a name="note211" href="#note211">211)</a> The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
11253 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
11254 ''off'', just one evaluation of x + 1 would suffice.
11255 </small>
11259 <p><!--para 1 -->
11260 The following functions provide access to the floating-point status flags.<sup><a href="#note212"><b>212)</b></a></sup> The int
11261 input argument for the functions represents a subset of floating-point exceptions, and can
11262 be zero or the bitwise OR of one or more floating-point exception macros, for example
11263 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
11264 functions is undefined.
11266 <p><b>Footnotes</b>
11267 <p><small><a name="note212" href="#note212">212)</a> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
11268 abstraction of flags that are either set or clear. An implementation may endow floating-point status
11269 flags with more information -- for example, the address of the code which first raised the floating-
11270 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
11271 content of flags.
11272 </small>
11276 <p><b>Synopsis</b>
11277 <p><!--para 1 -->
11278 <pre>
11280 int feclearexcept(int excepts);
11281 </pre>
11282 <p><b>Description</b>
11283 <p><!--para 2 -->
11284 The feclearexcept function attempts to clear the supported floating-point exceptions
11285 represented by its argument.
11286 <p><b>Returns</b>
11287 <p><!--para 3 -->
11288 The feclearexcept function returns zero if the excepts argument is zero or if all
11289 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
11292 <!--page 227 -->
11296 <p><b>Synopsis</b>
11297 <p><!--para 1 -->
11298 <pre>
11300 int fegetexceptflag(fexcept_t *flagp,
11301 int excepts);
11302 </pre>
11303 <p><b>Description</b>
11304 <p><!--para 2 -->
11305 The fegetexceptflag function attempts to store an implementation-defined
11306 representation of the states of the floating-point status flags indicated by the argument
11307 excepts in the object pointed to by the argument flagp.
11308 <p><b>Returns</b>
11309 <p><!--para 3 -->
11310 The fegetexceptflag function returns zero if the representation was successfully
11311 stored. Otherwise, it returns a nonzero value.
11315 <p><b>Synopsis</b>
11316 <p><!--para 1 -->
11317 <pre>
11319 int feraiseexcept(int excepts);
11320 </pre>
11321 <p><b>Description</b>
11322 <p><!--para 2 -->
11323 The feraiseexcept function attempts to raise the supported floating-point exceptions
11324 represented by its argument.<sup><a href="#note213"><b>213)</b></a></sup> The order in which these floating-point exceptions are
11325 raised is unspecified, except as stated in <a href="#F.8.6">F.8.6</a>. Whether the feraiseexcept function
11326 additionally raises the ''inexact'' floating-point exception whenever it raises the
11327 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
11328 <p><b>Returns</b>
11329 <p><!--para 3 -->
11330 The feraiseexcept function returns zero if the excepts argument is zero or if all
11331 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
11336 <!--page 228 -->
11338 <p><b>Footnotes</b>
11339 <p><small><a name="note213" href="#note213">213)</a> The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
11340 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
11342 </small>
11346 <p><b>Synopsis</b>
11347 <p><!--para 1 -->
11348 <pre>
11350 int fesetexceptflag(const fexcept_t *flagp,
11351 int excepts);
11352 </pre>
11353 <p><b>Description</b>
11354 <p><!--para 2 -->
11355 The fesetexceptflag function attempts to set the floating-point status flags
11356 indicated by the argument excepts to the states stored in the object pointed to by
11357 flagp. The value of *flagp shall have been set by a previous call to
11358 fegetexceptflag whose second argument represented at least those floating-point
11359 exceptions represented by the argument excepts. This function does not raise floating-
11360 point exceptions, but only sets the state of the flags.
11361 <p><b>Returns</b>
11362 <p><!--para 3 -->
11363 The fesetexceptflag function returns zero if the excepts argument is zero or if
11364 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
11365 a nonzero value.
11369 <p><b>Synopsis</b>
11370 <p><!--para 1 -->
11371 <pre>
11373 int fetestexcept(int excepts);
11374 </pre>
11375 <p><b>Description</b>
11376 <p><!--para 2 -->
11377 The fetestexcept function determines which of a specified subset of the floating-
11378 point exception flags are currently set. The excepts argument specifies the floating-
11380 <p><b>Returns</b>
11381 <p><!--para 3 -->
11382 The fetestexcept function returns the value of the bitwise OR of the floating-point
11383 exception macros corresponding to the currently set floating-point exceptions included in
11384 excepts.
11385 <p><!--para 4 -->
11386 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
11391 <!--page 229 -->
11392 <pre>
11394 /* ... */
11395 {
11396 #pragma STDC FENV_ACCESS ON
11397 int set_excepts;
11398 feclearexcept(FE_INVALID | FE_OVERFLOW);
11399 // maybe raise exceptions
11400 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
11401 if (set_excepts & FE_INVALID) f();
11402 if (set_excepts & FE_OVERFLOW) g();
11403 /* ... */
11404 }
11405 </pre>
11408 <p><b>Footnotes</b>
11409 <p><small><a name="note214" href="#note214">214)</a> This mechanism allows testing several floating-point exceptions with just one function call.
11410 </small>
11414 <p><!--para 1 -->
11415 The fegetround and fesetround functions provide control of rounding direction
11416 modes.
11420 <p><b>Synopsis</b>
11421 <p><!--para 1 -->
11422 <pre>
11424 int fegetround(void);
11425 </pre>
11426 <p><b>Description</b>
11427 <p><!--para 2 -->
11428 The fegetround function gets the current rounding direction.
11429 <p><b>Returns</b>
11430 <p><!--para 3 -->
11431 The fegetround function returns the value of the rounding direction macro
11432 representing the current rounding direction or a negative value if there is no such
11433 rounding direction macro or the current rounding direction is not determinable.
11437 <p><b>Synopsis</b>
11438 <p><!--para 1 -->
11439 <pre>
11441 int fesetround(int round);
11442 </pre>
11443 <p><b>Description</b>
11444 <p><!--para 2 -->
11445 The fesetround function establishes the rounding direction represented by its
11446 argument round. If the argument is not equal to the value of a rounding direction macro,
11447 the rounding direction is not changed.
11448 <p><b>Returns</b>
11449 <p><!--para 3 -->
11450 The fesetround function returns zero if and only if the requested rounding direction
11451 was established.
11452 <!--page 230 -->
11453 <p><!--para 4 -->
11454 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
11455 rounding direction fails.
11456 <pre>
11459 void f(int round_dir)
11460 {
11461 #pragma STDC FENV_ACCESS ON
11462 int save_round;
11463 int setround_ok;
11464 save_round = fegetround();
11465 setround_ok = fesetround(round_dir);
11466 assert(setround_ok == 0);
11467 /* ... */
11468 fesetround(save_round);
11469 /* ... */
11470 }
11471 </pre>
11476 <p><!--para 1 -->
11477 The functions in this section manage the floating-point environment -- status flags and
11478 control modes -- as one entity.
11482 <p><b>Synopsis</b>
11483 <p><!--para 1 -->
11484 <pre>
11486 int fegetenv(fenv_t *envp);
11487 </pre>
11488 <p><b>Description</b>
11489 <p><!--para 2 -->
11490 The fegetenv function attempts to store the current floating-point environment in the
11491 object pointed to by envp.
11492 <p><b>Returns</b>
11493 <p><!--para 3 -->
11494 The fegetenv function returns zero if the environment was successfully stored.
11495 Otherwise, it returns a nonzero value.
11499 <p><b>Synopsis</b>
11500 <p><!--para 1 -->
11501 <pre>
11503 int feholdexcept(fenv_t *envp);
11504 </pre>
11505 <p><b>Description</b>
11506 <p><!--para 2 -->
11507 The feholdexcept function saves the current floating-point environment in the object
11508 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
11509 (continue on floating-point exceptions) mode, if available, for all floating-point
11511 <!--page 231 -->
11512 <p><b>Returns</b>
11513 <p><!--para 3 -->
11514 The feholdexcept function returns zero if and only if non-stop floating-point
11515 exception handling was successfully installed.
11517 <p><b>Footnotes</b>
11518 <p><small><a name="note215" href="#note215">215)</a> IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
11519 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
11520 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
11521 function to write routines that hide spurious floating-point exceptions from their callers.
11522 </small>
11526 <p><b>Synopsis</b>
11527 <p><!--para 1 -->
11528 <pre>
11530 int fesetenv(const fenv_t *envp);
11531 </pre>
11532 <p><b>Description</b>
11533 <p><!--para 2 -->
11534 The fesetenv function attempts to establish the floating-point environment represented
11535 by the object pointed to by envp. The argument envp shall point to an object set by a
11536 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
11537 Note that fesetenv merely installs the state of the floating-point status flags
11538 represented through its argument, and does not raise these floating-point exceptions.
11539 <p><b>Returns</b>
11540 <p><!--para 3 -->
11541 The fesetenv function returns zero if the environment was successfully established.
11542 Otherwise, it returns a nonzero value.
11546 <p><b>Synopsis</b>
11547 <p><!--para 1 -->
11548 <pre>
11550 int feupdateenv(const fenv_t *envp);
11551 </pre>
11552 <p><b>Description</b>
11553 <p><!--para 2 -->
11554 The feupdateenv function attempts to save the currently raised floating-point
11555 exceptions in its automatic storage, install the floating-point environment represented by
11556 the object pointed to by envp, and then raise the saved floating-point exceptions. The
11557 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
11558 or equal a floating-point environment macro.
11559 <p><b>Returns</b>
11560 <p><!--para 3 -->
11561 The feupdateenv function returns zero if all the actions were successfully carried out.
11562 Otherwise, it returns a nonzero value.
11567 <!--page 232 -->
11568 <p><!--para 4 -->
11569 EXAMPLE Hide spurious underflow floating-point exceptions:
11570 <!--page 233 -->
11571 <pre>
11573 double f(double x)
11574 {
11575 #pragma STDC FENV_ACCESS ON
11576 double result;
11577 fenv_t save_env;
11578 if (feholdexcept(&save_env))
11579 return /* indication of an environmental problem */;
11580 // compute result
11581 if (/* test spurious underflow */)
11582 if (feclearexcept(FE_UNDERFLOW))
11583 return /* indication of an environmental problem */;
11584 if (feupdateenv(&save_env))
11585 return /* indication of an environmental problem */;
11586 return result;
11587 }
11588 </pre>
11592 <p><!--para 1 -->
11593 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
11594 parameters of the standard floating-point types.
11595 <p><!--para 2 -->
11596 The macros, their meanings, and the constraints (or restrictions) on their values are listed
11598 <!--page 234 -->
11601 <h3><a name="7.8" href="#7.8">7.8 Format conversion of integer types <inttypes.h></a></h3>
11602 <p><!--para 1 -->
11603 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.20"><stdint.h></a> and extends it with
11604 additional facilities provided by hosted implementations.
11605 <p><!--para 2 -->
11606 It declares functions for manipulating greatest-width integers and converting numeric
11607 character strings to greatest-width integers, and it declares the type
11608 <pre>
11609 imaxdiv_t
11610 </pre>
11611 which is a structure type that is the type of the value returned by the imaxdiv function.
11612 For each type declared in <a href="#7.20"><stdint.h></a>, it defines corresponding macros for conversion
11613 specifiers for use with the formatted input/output functions.<sup><a href="#note216"><b>216)</b></a></sup>
11614 <p><b> Forward references</b>: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>), formatted input/output
11615 functions (<a href="#7.21.6">7.21.6</a>), formatted wide character input/output functions (<a href="#7.28.2">7.28.2</a>).
11617 <p><b>Footnotes</b>
11618 <p><small><a name="note216" href="#note216">216)</a> See ''future library directions'' (<a href="#7.30.4">7.30.4</a>).
11619 </small>
11623 <p><!--para 1 -->
11624 Each of the following object-like macros expands to a character string literal containing a *
11625 conversion specifier, possibly modified by a length modifier, suitable for use within the
11626 format argument of a formatted input/output function when converting the corresponding
11627 integer type. These macro names have the general form of PRI (character string literals
11628 for the fprintf and fwprintf family) or SCN (character string literals for the
11629 fscanf and fwscanf family),<sup><a href="#note217"><b>217)</b></a></sup> followed by the conversion specifier, followed by a
11630 name corresponding to a similar type name in <a href="#7.20.1">7.20.1</a>. In these names, N represents the
11631 width of the type as described in <a href="#7.20.1">7.20.1</a>. For example, PRIdFAST32 can be used in a
11632 format string to print the value of an integer of type int_fast32_t.
11633 <p><!--para 2 -->
11634 The fprintf macros for signed integers are:
11635 <pre>
11636 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
11637 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
11638 </pre>
11639 <p><!--para 3 -->
11640 The fprintf macros for unsigned integers are:
11641 <pre>
11642 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
11643 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
11644 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
11645 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
11646 </pre>
11647 <p><!--para 4 -->
11648 The fscanf macros for signed integers are:
11652 <!--page 235 -->
11653 <pre>
11654 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
11655 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
11656 </pre>
11657 <p><!--para 5 -->
11658 The fscanf macros for unsigned integers are:
11659 <pre>
11660 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
11661 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
11662 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
11663 </pre>
11664 <p><!--para 6 -->
11665 For each type that the implementation provides in <a href="#7.20"><stdint.h></a>, the corresponding
11666 fprintf macros shall be defined and the corresponding fscanf macros shall be
11667 defined unless the implementation does not have a suitable fscanf length modifier for
11668 the type.
11669 <p><!--para 7 -->
11670 EXAMPLE
11671 <pre>
11674 int main(void)
11675 {
11676 uintmax_t i = UINTMAX_MAX; // this type always exists
11679 return 0;
11680 }
11681 </pre>
11684 <p><b>Footnotes</b>
11685 <p><small><a name="note217" href="#note217">217)</a> Separate macros are given for use with fprintf and fscanf functions because, in the general case,
11686 different format specifiers may be required for fprintf and fscanf, even when the type is the
11687 same.
11688 </small>
11695 <p><b>Synopsis</b>
11696 <p><!--para 1 -->
11697 <pre>
11699 intmax_t imaxabs(intmax_t j);
11700 </pre>
11701 <p><b>Description</b>
11702 <p><!--para 2 -->
11703 The imaxabs function computes the absolute value of an integer j. If the result cannot
11705 <p><b>Returns</b>
11706 <p><!--para 3 -->
11707 The imaxabs function returns the absolute value.
11712 <!--page 236 -->
11714 <p><b>Footnotes</b>
11715 <p><small><a name="note218" href="#note218">218)</a> The absolute value of the most negative number cannot be represented in two's complement.
11716 </small>
11720 <p><b>Synopsis</b>
11721 <p><!--para 1 -->
11722 <pre>
11724 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
11725 </pre>
11726 <p><b>Description</b>
11727 <p><!--para 2 -->
11728 The imaxdiv function computes numer / denom and numer % denom in a single
11729 operation.
11730 <p><b>Returns</b>
11731 <p><!--para 3 -->
11732 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
11733 quotient and the remainder. The structure shall contain (in either order) the members
11734 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
11735 either part of the result cannot be represented, the behavior is undefined.
11739 <p><b>Synopsis</b>
11740 <p><!--para 1 -->
11741 <pre>
11743 intmax_t strtoimax(const char * restrict nptr,
11744 char ** restrict endptr, int base);
11745 uintmax_t strtoumax(const char * restrict nptr,
11746 char ** restrict endptr, int base);
11747 </pre>
11748 <p><b>Description</b>
11749 <p><!--para 2 -->
11750 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
11751 strtoul, and strtoull functions, except that the initial portion of the string is
11752 converted to intmax_t and uintmax_t representation, respectively.
11753 <p><b>Returns</b>
11754 <p><!--para 3 -->
11755 The strtoimax and strtoumax functions return the converted value, if any. If no
11756 conversion could be performed, zero is returned. If the correct value is outside the range
11757 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
11758 (according to the return type and sign of the value, if any), and the value of the macro
11759 ERANGE is stored in errno.
11760 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
11762 <!--page 237 -->
11766 <p><b>Synopsis</b>
11767 <p><!--para 1 -->
11768 <pre>
11771 intmax_t wcstoimax(const wchar_t * restrict nptr,
11772 wchar_t ** restrict endptr, int base);
11773 uintmax_t wcstoumax(const wchar_t * restrict nptr,
11774 wchar_t ** restrict endptr, int base);
11775 </pre>
11776 <p><b>Description</b>
11777 <p><!--para 2 -->
11778 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
11779 wcstoul, and wcstoull functions except that the initial portion of the wide string is
11780 converted to intmax_t and uintmax_t representation, respectively.
11781 <p><b>Returns</b>
11782 <p><!--para 3 -->
11783 The wcstoimax function returns the converted value, if any. If no conversion could be
11784 performed, zero is returned. If the correct value is outside the range of representable
11785 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
11786 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
11787 errno.
11788 <p><b> Forward references</b>: the wcstol, wcstoll, wcstoul, and wcstoull functions
11790 <!--page 238 -->
11794 <p><!--para 1 -->
11795 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
11796 to the corresponding tokens (on the right):
11797 <!--page 239 -->
11798 <pre>
11799 and &&
11800 and_eq &=
11801 bitand &
11802 bitor |
11803 compl ~
11804 not !
11805 not_eq !=
11806 or ||
11807 or_eq |=
11808 xor ^
11809 xor_eq ^=
11810 </pre>
11814 <p><!--para 1 -->
11815 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
11816 parameters of the standard integer types.
11817 <p><!--para 2 -->
11818 The macros, their meanings, and the constraints (or restrictions) on their values are listed
11820 <!--page 240 -->
11824 <p><!--para 1 -->
11825 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
11826 <p><!--para 2 -->
11827 The type is
11828 <pre>
11829 struct lconv
11830 </pre>
11831 which contains members related to the formatting of numeric values. The structure shall
11832 contain at least the following members, in any order. The semantics of the members and
11833 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
11834 the values specified in the comments.
11835 <!--page 241 -->
11836 <pre>
11846 char frac_digits; // CHAR_MAX
11847 char p_cs_precedes; // CHAR_MAX
11848 char n_cs_precedes; // CHAR_MAX
11849 char p_sep_by_space; // CHAR_MAX
11850 char n_sep_by_space; // CHAR_MAX
11851 char p_sign_posn; // CHAR_MAX
11852 char n_sign_posn; // CHAR_MAX
11854 char int_frac_digits; // CHAR_MAX
11855 char int_p_cs_precedes; // CHAR_MAX
11856 char int_n_cs_precedes; // CHAR_MAX
11857 char int_p_sep_by_space; // CHAR_MAX
11858 char int_n_sep_by_space; // CHAR_MAX
11859 char int_p_sign_posn; // CHAR_MAX
11860 char int_n_sign_posn; // CHAR_MAX
11861 </pre>
11862 <p><!--para 3 -->
11864 <pre>
11865 LC_ALL
11866 LC_COLLATE
11867 LC_CTYPE
11868 LC_MONETARY
11869 LC_NUMERIC
11870 LC_TIME
11871 </pre>
11872 which expand to integer constant expressions with distinct values, suitable for use as the
11873 first argument to the setlocale function.<sup><a href="#note219"><b>219)</b></a></sup> Additional macro definitions, beginning
11874 with the characters LC_ and an uppercase letter,<sup><a href="#note220"><b>220)</b></a></sup> may also be specified by the
11875 implementation.
11877 <p><b>Footnotes</b>
11878 <p><small><a name="note219" href="#note219">219)</a> ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
11879 </small>
11880 <p><small><a name="note220" href="#note220">220)</a> See ''future library directions'' (<a href="#7.30.5">7.30.5</a>).
11881 </small>
11888 <p><b>Synopsis</b>
11889 <p><!--para 1 -->
11890 <pre>
11892 char *setlocale(int category, const char *locale);
11893 </pre>
11894 <p><b>Description</b>
11895 <p><!--para 2 -->
11896 The setlocale function selects the appropriate portion of the program's locale as
11897 specified by the category and locale arguments. The setlocale function may be
11898 used to change or query the program's entire current locale or portions thereof. The value
11899 LC_ALL for category names the program's entire locale; the other values for
11900 category name only a portion of the program's locale. LC_COLLATE affects the
11901 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
11902 the character handling functions<sup><a href="#note221"><b>221)</b></a></sup> and the multibyte and wide character functions.
11903 LC_MONETARY affects the monetary formatting information returned by the
11904 localeconv function. LC_NUMERIC affects the decimal-point character for the
11905 formatted input/output functions and the string conversion functions, as well as the
11906 nonmonetary formatting information returned by the localeconv function. LC_TIME
11907 affects the behavior of the strftime and wcsftime functions.
11908 <p><!--para 3 -->
11911 implementation-defined strings may be passed as the second argument to setlocale.
11913 <!--page 242 -->
11914 <p><!--para 4 -->
11915 At program startup, the equivalent of
11916 <pre>
11918 </pre>
11919 is executed.
11920 <p><!--para 5 -->
11921 A call to the setlocale function may introduce a data race with other calls to the
11922 setlocale function or with calls to functions that are affected by the current locale.
11923 The implementation shall behave as if no library function calls the setlocale function.
11924 <p><b>Returns</b>
11925 <p><!--para 6 -->
11926 If a pointer to a string is given for locale and the selection can be honored, the
11927 setlocale function returns a pointer to the string associated with the specified
11928 category for the new locale. If the selection cannot be honored, the setlocale
11929 function returns a null pointer and the program's locale is not changed.
11930 <p><!--para 7 -->
11931 A null pointer for locale causes the setlocale function to return a pointer to the
11932 string associated with the category for the program's current locale; the program's
11934 <p><!--para 8 -->
11935 The pointer to string returned by the setlocale function is such that a subsequent call
11936 with that string value and its associated category will restore that part of the program's
11937 locale. The string pointed to shall not be modified by the program, but may be
11938 overwritten by a subsequent call to the setlocale function.
11939 <p><b> Forward references</b>: formatted input/output functions (<a href="#7.21.6">7.21.6</a>), multibyte/wide
11940 character conversion functions (<a href="#7.22.7">7.22.7</a>), multibyte/wide string conversion functions
11941 (<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="#7.23.4.3">7.23.4.3</a>), the
11942 strftime function (<a href="#7.26.3.5">7.26.3.5</a>), the strxfrm function (<a href="#7.23.4.5">7.23.4.5</a>).
11944 <p><b>Footnotes</b>
11945 <p><small><a name="note221" href="#note221">221)</a> The only functions in <a href="#7.4">7.4</a> whose behavior is not affected by the current locale are isdigit and
11946 isxdigit.
11947 </small>
11948 <p><small><a name="note222" href="#note222">222)</a> The implementation shall arrange to encode in a string the various categories due to a heterogeneous
11949 locale when category has the value LC_ALL.
11950 </small>
11957 <p><b>Synopsis</b>
11958 <p><!--para 1 -->
11959 <pre>
11961 struct lconv *localeconv(void);
11962 </pre>
11963 <p><b>Description</b>
11964 <p><!--para 2 -->
11965 The localeconv function sets the components of an object with type struct lconv
11966 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
11967 according to the rules of the current locale.
11971 <!--page 243 -->
11972 <p><!--para 3 -->
11973 The members of the structure with type char * are pointers to strings, any of which
11975 the current locale or is of zero length. Apart from grouping and mon_grouping, the
11976 strings shall start and end in the initial shift state. The members with type char are
11977 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
11978 available in the current locale. The members include the following:
11979 char *decimal_point
11980 <pre>
11981 The decimal-point character used to format nonmonetary quantities.
11982 </pre>
11983 char *thousands_sep
11984 <pre>
11985 The character used to separate groups of digits before the decimal-point
11986 character in formatted nonmonetary quantities.
11987 </pre>
11988 char *grouping
11989 <pre>
11990 A string whose elements indicate the size of each group of digits in
11991 formatted nonmonetary quantities.
11992 </pre>
11993 char *mon_decimal_point
11994 <pre>
11995 The decimal-point used to format monetary quantities.
11996 </pre>
11997 char *mon_thousands_sep
11998 <pre>
11999 The separator for groups of digits before the decimal-point in formatted
12000 monetary quantities.
12001 </pre>
12002 char *mon_grouping
12003 <pre>
12004 A string whose elements indicate the size of each group of digits in
12005 formatted monetary quantities.
12006 </pre>
12007 char *positive_sign
12008 <pre>
12009 The string used to indicate a nonnegative-valued formatted monetary
12010 quantity.
12011 </pre>
12012 char *negative_sign
12013 <pre>
12014 The string used to indicate a negative-valued formatted monetary quantity.
12015 </pre>
12016 char *currency_symbol
12017 <pre>
12018 The local currency symbol applicable to the current locale.
12019 </pre>
12020 char frac_digits
12021 <pre>
12022 The number of fractional digits (those after the decimal-point) to be
12023 displayed in a locally formatted monetary quantity.
12024 </pre>
12025 char p_cs_precedes
12026 <!--page 244 -->
12027 <pre>
12028 Set to 1 or 0 if the currency_symbol respectively precedes or
12029 succeeds the value for a nonnegative locally formatted monetary quantity.
12030 </pre>
12031 char n_cs_precedes
12032 <pre>
12033 Set to 1 or 0 if the currency_symbol respectively precedes or
12034 succeeds the value for a negative locally formatted monetary quantity.
12035 </pre>
12036 char p_sep_by_space
12037 <pre>
12038 Set to a value indicating the separation of the currency_symbol, the
12039 sign string, and the value for a nonnegative locally formatted monetary
12040 quantity.
12041 </pre>
12042 char n_sep_by_space
12043 <pre>
12044 Set to a value indicating the separation of the currency_symbol, the
12045 sign string, and the value for a negative locally formatted monetary
12046 quantity.
12047 </pre>
12048 char p_sign_posn
12049 <pre>
12050 Set to a value indicating the positioning of the positive_sign for a
12051 nonnegative locally formatted monetary quantity.
12052 </pre>
12053 char n_sign_posn
12054 <pre>
12055 Set to a value indicating the positioning of the negative_sign for a
12056 negative locally formatted monetary quantity.
12057 </pre>
12058 char *int_curr_symbol
12059 <pre>
12060 The international currency symbol applicable to the current locale. The
12061 first three characters contain the alphabetic international currency symbol
12062 in accordance with those specified in ISO 4217. The fourth character
12063 (immediately preceding the null character) is the character used to separate
12064 the international currency symbol from the monetary quantity.
12065 </pre>
12066 char int_frac_digits
12067 <pre>
12068 The number of fractional digits (those after the decimal-point) to be
12069 displayed in an internationally formatted monetary quantity.
12070 </pre>
12071 char int_p_cs_precedes
12072 <pre>
12073 Set to 1 or 0 if the int_curr_symbol respectively precedes or
12074 succeeds the value for a nonnegative internationally formatted monetary
12075 quantity.
12076 </pre>
12077 char int_n_cs_precedes
12078 <pre>
12079 Set to 1 or 0 if the int_curr_symbol respectively precedes or
12080 succeeds the value for a negative internationally formatted monetary
12081 quantity.
12082 </pre>
12083 char int_p_sep_by_space
12084 <!--page 245 -->
12085 <pre>
12086 Set to a value indicating the separation of the int_curr_symbol, the
12087 sign string, and the value for a nonnegative internationally formatted
12088 monetary quantity.
12089 </pre>
12090 char int_n_sep_by_space
12091 <pre>
12092 Set to a value indicating the separation of the int_curr_symbol, the
12093 sign string, and the value for a negative internationally formatted monetary
12094 quantity.
12095 </pre>
12096 char int_p_sign_posn
12097 <pre>
12098 Set to a value indicating the positioning of the positive_sign for a
12099 nonnegative internationally formatted monetary quantity.
12100 </pre>
12101 char int_n_sign_posn
12102 <pre>
12103 Set to a value indicating the positioning of the negative_sign for a
12104 negative internationally formatted monetary quantity.
12105 </pre>
12106 <p><!--para 4 -->
12107 The elements of grouping and mon_grouping are interpreted according to the
12108 following:
12109 CHAR_MAX No further grouping is to be performed.
12110 0 The previous element is to be repeatedly used for the remainder of the
12111 <pre>
12112 digits.
12113 </pre>
12114 other The integer value is the number of digits that compose the current group.
12115 <pre>
12116 The next element is examined to determine the size of the next group of
12117 digits before the current group.
12118 </pre>
12119 <p><!--para 5 -->
12120 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
12121 and int_n_sep_by_space are interpreted according to the following:
12122 0 No space separates the currency symbol and value.
12123 1 If the currency symbol and sign string are adjacent, a space separates them from the
12124 <pre>
12125 value; otherwise, a space separates the currency symbol from the value.
12126 </pre>
12127 2 If the currency symbol and sign string are adjacent, a space separates them;
12128 <pre>
12129 otherwise, a space separates the sign string from the value.
12130 </pre>
12131 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
12132 int_curr_symbol is used instead of a space.
12133 <p><!--para 6 -->
12134 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
12135 int_n_sign_posn are interpreted according to the following:
12136 0 Parentheses surround the quantity and currency symbol.
12137 1 The sign string precedes the quantity and currency symbol.
12138 2 The sign string succeeds the quantity and currency symbol.
12139 3 The sign string immediately precedes the currency symbol.
12140 4 The sign string immediately succeeds the currency symbol.
12141 <!--page 246 -->
12142 <p><!--para 7 -->
12143 The implementation shall behave as if no library function calls the localeconv
12144 function.
12145 <p><b>Returns</b>
12146 <p><!--para 8 -->
12147 The localeconv function returns a pointer to the filled-in object. The structure
12148 pointed to by the return value shall not be modified by the program, but may be
12149 overwritten by a subsequent call to the localeconv function. In addition, calls to the
12150 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
12151 overwrite the contents of the structure.
12152 <p><!--para 9 -->
12153 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
12154 monetary quantities.
12155 <pre>
12156 Local format International format
12157 </pre>
12159 Country Positive Negative Positive Negative
12161 Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
12162 Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
12163 Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
12164 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
12165 <p><!--para 10 -->
12166 For these four countries, the respective values for the monetary members of the structure returned by
12167 localeconv could be:
12168 <pre>
12169 Country1 Country2 Country3 Country4
12170 </pre>
12178 frac_digits 2 0 2 2
12179 p_cs_precedes 0 1 1 1
12180 n_cs_precedes 0 1 1 1
12181 p_sep_by_space 1 0 1 0
12182 n_sep_by_space 1 0 2 0
12183 p_sign_posn 1 1 1 1
12184 n_sign_posn 1 1 4 2
12186 int_frac_digits 2 0 2 2
12187 int_p_cs_precedes 1 1 1 1
12188 int_n_cs_precedes 1 1 1 1
12189 int_p_sep_by_space 1 1 1 1
12190 int_n_sep_by_space 2 1 2 1
12191 int_p_sign_posn 1 1 1 1
12192 int_n_sign_posn 4 1 4 2
12193 <!--page 247 -->
12194 <p><!--para 11 -->
12195 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
12196 affect the formatted value.
12197 <pre>
12198 p_sep_by_space
12199 </pre>
12201 p_cs_precedes p_sign_posn 0 1 2
12203 <pre>
12209 </pre>
12211 <!--page 248 -->
12212 <pre>
12218 </pre>
12222 <p><!--para 1 -->
12223 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
12224 several macros. Most synopses specify a family of functions consisting of a principal
12225 function with one or more double parameters, a double return value, or both; and
12226 other functions with the same name but with f and l suffixes, which are corresponding
12227 functions with float and long double parameters, return values, or both.<sup><a href="#note223"><b>223)</b></a></sup>
12228 Integer arithmetic functions and conversion functions are discussed later.
12229 <p><!--para 2 -->
12230 The types
12231 <pre>
12232 float_t
12233 double_t
12234 </pre>
12235 are floating types at least as wide as float and double, respectively, and such that
12236 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
12237 float_t and double_t are float and double, respectively; if
12238 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
12239 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
12241 <p><!--para 3 -->
12242 The macro
12243 <pre>
12244 HUGE_VAL
12245 </pre>
12246 expands to a positive double constant expression, not necessarily representable as a
12247 float. The macros
12248 <pre>
12249 HUGE_VALF
12250 HUGE_VALL
12251 </pre>
12252 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note225"><b>225)</b></a></sup>
12253 <p><!--para 4 -->
12254 The macro
12255 <pre>
12256 INFINITY
12257 </pre>
12258 expands to a constant expression of type float representing positive or unsigned
12259 infinity, if available; else to a positive constant of type float that overflows at
12263 <!--page 249 -->
12265 <p><!--para 5 -->
12266 The macro
12267 <pre>
12268 NAN
12269 </pre>
12270 is defined if and only if the implementation supports quiet NaNs for the float type. It
12271 expands to a constant expression of type float representing a quiet NaN.
12272 <p><!--para 6 -->
12273 The number classification macros
12274 <pre>
12275 FP_INFINITE
12276 FP_NAN
12277 FP_NORMAL
12278 FP_SUBNORMAL
12279 FP_ZERO
12280 </pre>
12281 represent the mutually exclusive kinds of floating-point values. They expand to integer
12282 constant expressions with distinct values. Additional implementation-defined floating-
12283 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
12284 may also be specified by the implementation.
12285 <p><!--para 7 -->
12286 The macro
12287 <pre>
12288 FP_FAST_FMA
12289 </pre>
12290 is optionally defined. If defined, it indicates that the fma function generally executes
12291 about as fast as, or faster than, a multiply and an add of double operands.<sup><a href="#note227"><b>227)</b></a></sup> The
12292 macros
12293 <pre>
12294 FP_FAST_FMAF
12295 FP_FAST_FMAL
12296 </pre>
12297 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
12298 these macros expand to the integer constant 1.
12299 <p><!--para 8 -->
12300 The macros
12301 <pre>
12302 FP_ILOGB0
12303 FP_ILOGBNAN
12304 </pre>
12305 expand to integer constant expressions whose values are returned by ilogb(x) if x is
12306 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
12307 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
12310 <!--page 250 -->
12311 <p><!--para 9 -->
12312 The macros
12313 <pre>
12314 MATH_ERRNO
12315 MATH_ERREXCEPT
12316 </pre>
12317 expand to the integer constants 1 and 2, respectively; the macro
12318 <pre>
12319 math_errhandling
12320 </pre>
12321 expands to an expression that has type int and the value MATH_ERRNO,
12322 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
12323 constant for the duration of the program. It is unspecified whether
12324 math_errhandling is a macro or an identifier with external linkage. If a macro
12325 definition is suppressed or a program defines an identifier with the name
12326 math_errhandling, the behavior is undefined. If the expression
12327 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
12328 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
12331 <p><b>Footnotes</b>
12332 <p><small><a name="note223" href="#note223">223)</a> Particularly on systems with wide expression evaluation, a <a href="#7.12"><math.h></a> function might pass arguments
12333 and return values in wider format than the synopsis prototype indicates.
12334 </small>
12335 <p><small><a name="note224" href="#note224">224)</a> The types float_t and double_t are intended to be the implementation's most efficient types at
12336 least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
12337 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
12338 </small>
12339 <p><small><a name="note225" href="#note225">225)</a> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
12340 supports infinities.
12341 </small>
12342 <p><small><a name="note226" href="#note226">226)</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.
12343 </small>
12344 <p><small><a name="note227" href="#note227">227)</a> Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
12345 directly with a hardware multiply-add instruction. Software implementations are expected to be
12346 substantially slower.
12347 </small>
12351 <p><!--para 1 -->
12352 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
12353 values of its input arguments, except where stated otherwise. Each function shall execute
12354 as if it were a single operation without raising SIGFPE and without generating any of the
12355 floating-point exceptions ''invalid'', ''divide-by-zero'', or ''overflow'' except to reflect
12356 the result of the function.
12357 <p><!--para 2 -->
12358 For all functions, a domain error occurs if an input argument is outside the domain over
12359 which the mathematical function is defined. The description of each function lists any
12360 required domain errors; an implementation may define additional domain errors, provided
12361 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note228"><b>228)</b></a></sup> On a
12362 domain error, the function returns an implementation-defined value; if the integer
12363 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
12364 errno acquires the value EDOM; if the integer expression math_errhandling &
12365 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
12366 <p><!--para 3 -->
12367 Similarly, a pole error (also known as a singularity or infinitary) occurs if the
12368 mathematical function has an exact infinite result as the finite input argument(s) are
12369 approached in the limit (for example, log(0.0)). The description of each function lists
12370 any required pole errors; an implementation may define additional pole errors, provided
12371 that such errors are consistent with the mathematical definition of the function. On a pole
12372 error, the function returns an implementation-defined value; if the integer expression
12375 <!--page 251 -->
12376 math_errhandling & MATH_ERRNO is nonzero, the integer expression errno
12377 acquires the value ERANGE; if the integer expression math_errhandling &
12378 MATH_ERREXCEPT is nonzero, the ''divide-by-zero'' floating-point exception is raised.
12379 <p><!--para 4 -->
12380 Likewise, a range error occurs if the mathematical result of the function cannot be
12381 represented in an object of the specified type, due to extreme magnitude.
12382 <p><!--para 5 -->
12383 A floating result overflows if the magnitude of the mathematical result is finite but so
12384 large that the mathematical result cannot be represented without extraordinary roundoff
12385 error in an object of the specified type. If a floating result overflows and default rounding
12386 is in effect, then the function returns the value of the macro HUGE_VAL, HUGE_VALF, or *
12387 HUGE_VALL according to the return type, with the same sign as the correct value of the
12388 function; if the integer expression math_errhandling & MATH_ERRNO is nonzero,
12389 the integer expression errno acquires the value ERANGE; if the integer expression
12390 math_errhandling & MATH_ERREXCEPT is nonzero, the ''overflow'' floating-
12391 point exception is raised.
12392 <p><!--para 6 -->
12393 The result underflows if the magnitude of the mathematical result is so small that the
12394 mathematical result cannot be represented, without extraordinary roundoff error, in an
12395 object of the specified type.<sup><a href="#note229"><b>229)</b></a></sup> If the result underflows, the function returns an
12396 implementation-defined value whose magnitude is no greater than the smallest
12397 normalized positive number in the specified type; if the integer expression
12398 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
12399 value ERANGE is implementation-defined; if the integer expression
12400 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
12401 floating-point exception is raised is implementation-defined.
12402 <p><!--para 7 -->
12403 If a domain, pole, or range error occurs and the integer expression
12404 math_errhandling & MATH_ERRNO is zero,<sup><a href="#note230"><b>230)</b></a></sup> then errno shall either be set to
12405 the value corresponding to the error or left unmodified. If no such error occurs, errno
12406 shall be left unmodified regardless of the setting of math_errhandling.
12411 <!--page 252 -->
12413 <p><b>Footnotes</b>
12414 <p><small><a name="note228" href="#note228">228)</a> In an implementation that supports infinities, this allows an infinity as an argument to be a domain
12415 error if the mathematical domain of the function does not include the infinity.
12416 </small>
12417 <p><small><a name="note229" href="#note229">229)</a> The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
12418 also ''flush-to-zero'' underflow.
12419 </small>
12420 <p><small><a name="note230" href="#note230">230)</a> Math errors are being indicated by the floating-point exception flags rather than by errno.
12421 </small>
12425 <p><b>Synopsis</b>
12426 <p><!--para 1 -->
12427 <pre>
12429 #pragma STDC FP_CONTRACT on-off-switch
12430 </pre>
12431 <p><b>Description</b>
12432 <p><!--para 2 -->
12433 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
12434 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
12435 either outside external declarations or preceding all explicit declarations and statements
12436 inside a compound statement. When outside external declarations, the pragma takes
12437 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
12438 the end of the translation unit. When inside a compound statement, the pragma takes
12439 effect from its occurrence until another FP_CONTRACT pragma is encountered
12440 (including within a nested compound statement), or until the end of the compound
12441 statement; at the end of a compound statement the state for the pragma is restored to its
12442 condition just before the compound statement. If this pragma is used in any other
12443 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
12444 implementation-defined.
12448 <p><!--para 1 -->
12449 In the synopses in this subclause, real-floating indicates that the argument shall be an
12450 expression of real floating type.
12454 <p><b>Synopsis</b>
12455 <p><!--para 1 -->
12456 <pre>
12458 int fpclassify(real-floating x);
12459 </pre>
12460 <p><b>Description</b>
12461 <p><!--para 2 -->
12462 The fpclassify macro classifies its argument value as NaN, infinite, normal,
12463 subnormal, zero, or into another implementation-defined category. First, an argument
12464 represented in a format wider than its semantic type is converted to its semantic type.
12465 Then classification is based on the type of the argument.<sup><a href="#note231"><b>231)</b></a></sup>
12466 <p><b>Returns</b>
12467 <p><!--para 3 -->
12468 The fpclassify macro returns the value of the number classification macro
12469 appropriate to the value of its argument. *
12472 <!--page 253 -->
12474 <p><b>Footnotes</b>
12475 <p><small><a name="note231" href="#note231">231)</a> Since an expression can be evaluated with more range and precision than its type has, it is important to
12476 know the type that classification is based on. For example, a normal long double value might
12477 become subnormal when converted to double, and zero when converted to float.
12478 </small>
12482 <p><b>Synopsis</b>
12483 <p><!--para 1 -->
12484 <pre>
12486 int isfinite(real-floating x);
12487 </pre>
12488 <p><b>Description</b>
12489 <p><!--para 2 -->
12490 The isfinite macro determines whether its argument has a finite value (zero,
12491 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
12492 format wider than its semantic type is converted to its semantic type. Then determination
12493 is based on the type of the argument.
12494 <p><b>Returns</b>
12495 <p><!--para 3 -->
12496 The isfinite macro returns a nonzero value if and only if its argument has a finite
12497 value.
12501 <p><b>Synopsis</b>
12502 <p><!--para 1 -->
12503 <pre>
12505 int isinf(real-floating x);
12506 </pre>
12507 <p><b>Description</b>
12508 <p><!--para 2 -->
12509 The isinf macro determines whether its argument value is an infinity (positive or
12510 negative). First, an argument represented in a format wider than its semantic type is
12511 converted to its semantic type. Then determination is based on the type of the argument.
12512 <p><b>Returns</b>
12513 <p><!--para 3 -->
12514 The isinf macro returns a nonzero value if and only if its argument has an infinite
12515 value.
12519 <p><b>Synopsis</b>
12520 <p><!--para 1 -->
12521 <pre>
12523 int isnan(real-floating x);
12524 </pre>
12525 <p><b>Description</b>
12526 <p><!--para 2 -->
12527 The isnan macro determines whether its argument value is a NaN. First, an argument
12528 represented in a format wider than its semantic type is converted to its semantic type.
12529 Then determination is based on the type of the argument.<sup><a href="#note232"><b>232)</b></a></sup>
12532 <!--page 254 -->
12533 <p><b>Returns</b>
12534 <p><!--para 3 -->
12535 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
12537 <p><b>Footnotes</b>
12538 <p><small><a name="note232" href="#note232">232)</a> For the isnan macro, the type for determination does not matter unless the implementation supports
12539 NaNs in the evaluation type but not in the semantic type.
12540 </small>
12544 <p><b>Synopsis</b>
12545 <p><!--para 1 -->
12546 <pre>
12548 int isnormal(real-floating x);
12549 </pre>
12550 <p><b>Description</b>
12551 <p><!--para 2 -->
12552 The isnormal macro determines whether its argument value is normal (neither zero,
12553 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
12554 semantic type is converted to its semantic type. Then determination is based on the type
12555 of the argument.
12556 <p><b>Returns</b>
12557 <p><!--para 3 -->
12558 The isnormal macro returns a nonzero value if and only if its argument has a normal
12559 value.
12563 <p><b>Synopsis</b>
12564 <p><!--para 1 -->
12565 <pre>
12567 int signbit(real-floating x);
12568 </pre>
12569 <p><b>Description</b>
12570 <p><!--para 2 -->
12571 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note233"><b>233)</b></a></sup>
12572 <p><b>Returns</b>
12573 <p><!--para 3 -->
12574 The signbit macro returns a nonzero value if and only if the sign of its argument value
12575 is negative.
12580 <!--page 255 -->
12582 <p><b>Footnotes</b>
12583 <p><small><a name="note233" href="#note233">233)</a> The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
12584 unsigned, it is treated as positive.
12585 </small>
12592 <p><b>Synopsis</b>
12593 <p><!--para 1 -->
12594 <pre>
12596 double acos(double x);
12597 float acosf(float x);
12598 long double acosl(long double x);
12599 </pre>
12600 <p><b>Description</b>
12601 <p><!--para 2 -->
12602 The acos functions compute the principal value of the arc cosine of x. A domain error
12603 occurs for arguments not in the interval [-1, +1].
12604 <p><b>Returns</b>
12605 <p><!--para 3 -->
12606 The acos functions return arccos x in the interval [0, pi ] radians.
12610 <p><b>Synopsis</b>
12611 <p><!--para 1 -->
12612 <pre>
12614 double asin(double x);
12615 float asinf(float x);
12616 long double asinl(long double x);
12617 </pre>
12618 <p><b>Description</b>
12619 <p><!--para 2 -->
12620 The asin functions compute the principal value of the arc sine of x. A domain error
12621 occurs for arguments not in the interval [-1, +1].
12622 <p><b>Returns</b>
12623 <p><!--para 3 -->
12624 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
12628 <p><b>Synopsis</b>
12629 <p><!--para 1 -->
12630 <pre>
12632 double atan(double x);
12633 float atanf(float x);
12634 long double atanl(long double x);
12635 </pre>
12636 <p><b>Description</b>
12637 <p><!--para 2 -->
12638 The atan functions compute the principal value of the arc tangent of x.
12639 <!--page 256 -->
12640 <p><b>Returns</b>
12641 <p><!--para 3 -->
12642 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
12646 <p><b>Synopsis</b>
12647 <p><!--para 1 -->
12648 <pre>
12650 double atan2(double y, double x);
12651 float atan2f(float y, float x);
12652 long double atan2l(long double y, long double x);
12653 </pre>
12654 <p><b>Description</b>
12655 <p><!--para 2 -->
12656 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
12657 arguments to determine the quadrant of the return value. A domain error may occur if
12658 both arguments are zero.
12659 <p><b>Returns</b>
12660 <p><!--para 3 -->
12661 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
12665 <p><b>Synopsis</b>
12666 <p><!--para 1 -->
12667 <pre>
12669 double cos(double x);
12670 float cosf(float x);
12671 long double cosl(long double x);
12672 </pre>
12673 <p><b>Description</b>
12674 <p><!--para 2 -->
12675 The cos functions compute the cosine of x (measured in radians).
12676 <p><b>Returns</b>
12677 <p><!--para 3 -->
12678 The cos functions return cos x.
12682 <p><b>Synopsis</b>
12683 <p><!--para 1 -->
12684 <pre>
12686 double sin(double x);
12687 float sinf(float x);
12688 long double sinl(long double x);
12689 </pre>
12690 <p><b>Description</b>
12691 <p><!--para 2 -->
12692 The sin functions compute the sine of x (measured in radians).
12693 <!--page 257 -->
12694 <p><b>Returns</b>
12695 <p><!--para 3 -->
12696 The sin functions return sin x.
12700 <p><b>Synopsis</b>
12701 <p><!--para 1 -->
12702 <pre>
12704 double tan(double x);
12705 float tanf(float x);
12706 long double tanl(long double x);
12707 </pre>
12708 <p><b>Description</b>
12709 <p><!--para 2 -->
12710 The tan functions return the tangent of x (measured in radians).
12711 <p><b>Returns</b>
12712 <p><!--para 3 -->
12713 The tan functions return tan x.
12720 <p><b>Synopsis</b>
12721 <p><!--para 1 -->
12722 <pre>
12724 double acosh(double x);
12725 float acoshf(float x);
12726 long double acoshl(long double x);
12727 </pre>
12728 <p><b>Description</b>
12729 <p><!--para 2 -->
12730 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
12731 error occurs for arguments less than 1.
12732 <p><b>Returns</b>
12733 <p><!--para 3 -->
12734 The acosh functions return arcosh x in the interval [0, +(inf)].
12738 <p><b>Synopsis</b>
12739 <p><!--para 1 -->
12740 <pre>
12742 double asinh(double x);
12743 float asinhf(float x);
12744 long double asinhl(long double x);
12745 </pre>
12746 <p><b>Description</b>
12747 <p><!--para 2 -->
12748 The asinh functions compute the arc hyperbolic sine of x.
12749 <!--page 258 -->
12750 <p><b>Returns</b>
12751 <p><!--para 3 -->
12752 The asinh functions return arsinh x.
12756 <p><b>Synopsis</b>
12757 <p><!--para 1 -->
12758 <pre>
12760 double atanh(double x);
12761 float atanhf(float x);
12762 long double atanhl(long double x);
12763 </pre>
12764 <p><b>Description</b>
12765 <p><!--para 2 -->
12766 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
12767 for arguments not in the interval [-1, +1]. A pole error may occur if the argument equals
12768 -1 or +1.
12769 <p><b>Returns</b>
12770 <p><!--para 3 -->
12771 The atanh functions return artanh x.
12775 <p><b>Synopsis</b>
12776 <p><!--para 1 -->
12777 <pre>
12779 double cosh(double x);
12780 float coshf(float x);
12781 long double coshl(long double x);
12782 </pre>
12783 <p><b>Description</b>
12784 <p><!--para 2 -->
12785 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
12786 magnitude of x is too large.
12787 <p><b>Returns</b>
12788 <p><!--para 3 -->
12789 The cosh functions return cosh x.
12793 <p><b>Synopsis</b>
12794 <p><!--para 1 -->
12795 <pre>
12797 double sinh(double x);
12798 float sinhf(float x);
12799 long double sinhl(long double x);
12800 </pre>
12801 <p><b>Description</b>
12802 <p><!--para 2 -->
12803 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
12804 magnitude of x is too large.
12805 <!--page 259 -->
12806 <p><b>Returns</b>
12807 <p><!--para 3 -->
12808 The sinh functions return sinh x.
12812 <p><b>Synopsis</b>
12813 <p><!--para 1 -->
12814 <pre>
12816 double tanh(double x);
12817 float tanhf(float x);
12818 long double tanhl(long double x);
12819 </pre>
12820 <p><b>Description</b>
12821 <p><!--para 2 -->
12822 The tanh functions compute the hyperbolic tangent of x.
12823 <p><b>Returns</b>
12824 <p><!--para 3 -->
12825 The tanh functions return tanh x.
12832 <p><b>Synopsis</b>
12833 <p><!--para 1 -->
12834 <pre>
12836 double exp(double x);
12837 float expf(float x);
12838 long double expl(long double x);
12839 </pre>
12840 <p><b>Description</b>
12841 <p><!--para 2 -->
12842 The exp functions compute the base-e exponential of x. A range error occurs if the
12843 magnitude of x is too large.
12844 <p><b>Returns</b>
12845 <p><!--para 3 -->
12846 The exp functions return ex .
12850 <p><b>Synopsis</b>
12851 <p><!--para 1 -->
12852 <pre>
12854 double exp2(double x);
12855 float exp2f(float x);
12856 long double exp2l(long double x);
12857 </pre>
12858 <p><b>Description</b>
12859 <p><!--para 2 -->
12860 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
12861 magnitude of x is too large.
12862 <!--page 260 -->
12863 <p><b>Returns</b>
12864 <p><!--para 3 -->
12865 The exp2 functions return 2x .
12869 <p><b>Synopsis</b>
12870 <p><!--para 1 -->
12871 <pre>
12873 double expm1(double x);
12874 float expm1f(float x);
12875 long double expm1l(long double x);
12876 </pre>
12877 <p><b>Description</b>
12878 <p><!--para 2 -->
12879 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
12881 <p><b>Returns</b>
12882 <p><!--para 3 -->
12883 The expm1 functions return ex - 1.
12885 <p><b>Footnotes</b>
12886 <p><small><a name="note234" href="#note234">234)</a> For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
12887 </small>
12891 <p><b>Synopsis</b>
12892 <p><!--para 1 -->
12893 <pre>
12895 double frexp(double value, int *exp);
12896 float frexpf(float value, int *exp);
12897 long double frexpl(long double value, int *exp);
12898 </pre>
12899 <p><b>Description</b>
12900 <p><!--para 2 -->
12901 The frexp functions break a floating-point number into a normalized fraction and an
12902 integral power of 2. They store the integer in the int object pointed to by exp.
12903 <p><b>Returns</b>
12904 <p><!--para 3 -->
12905 If value is not a floating-point number or if the integral power of 2 is outside the range
12906 of int, the results are unspecified. Otherwise, the frexp functions return the value x,
12907 such that x has a magnitude in the interval [1/2, 1) or zero, and value equals x x 2*exp .
12908 If value is zero, both parts of the result are zero.
12913 <!--page 261 -->
12917 <p><b>Synopsis</b>
12918 <p><!--para 1 -->
12919 <pre>
12921 int ilogb(double x);
12922 int ilogbf(float x);
12923 int ilogbl(long double x);
12924 </pre>
12925 <p><b>Description</b>
12926 <p><!--para 2 -->
12927 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
12928 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
12929 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
12930 the corresponding logb function and casting the returned value to type int. A domain
12931 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
12932 the range of the return type, the numeric result is unspecified.
12933 <p><b>Returns</b>
12934 <p><!--para 3 -->
12935 The ilogb functions return the exponent of x as a signed int value.
12940 <p><b>Synopsis</b>
12941 <p><!--para 1 -->
12942 <pre>
12944 double ldexp(double x, int exp);
12945 float ldexpf(float x, int exp);
12946 long double ldexpl(long double x, int exp);
12947 </pre>
12948 <p><b>Description</b>
12949 <p><!--para 2 -->
12950 The ldexp functions multiply a floating-point number by an integral power of 2. A
12951 range error may occur.
12952 <p><b>Returns</b>
12953 <p><!--para 3 -->
12954 The ldexp functions return x x 2exp .
12958 <p><b>Synopsis</b>
12959 <p><!--para 1 -->
12960 <!--page 262 -->
12961 <pre>
12963 double log(double x);
12964 float logf(float x);
12965 long double logl(long double x);
12966 </pre>
12967 <p><b>Description</b>
12968 <p><!--para 2 -->
12969 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
12970 the argument is negative. A pole error may occur if the argument is zero.
12971 <p><b>Returns</b>
12972 <p><!--para 3 -->
12973 The log functions return loge x.
12977 <p><b>Synopsis</b>
12978 <p><!--para 1 -->
12979 <pre>
12981 double log10(double x);
12982 float log10f(float x);
12983 long double log10l(long double x);
12984 </pre>
12985 <p><b>Description</b>
12986 <p><!--para 2 -->
12987 The log10 functions compute the base-10 (common) logarithm of x. A domain error
12988 occurs if the argument is negative. A pole error may occur if the argument is zero.
12989 <p><b>Returns</b>
12990 <p><!--para 3 -->
12991 The log10 functions return log10 x.
12995 <p><b>Synopsis</b>
12996 <p><!--para 1 -->
12997 <pre>
12999 double log1p(double x);
13000 float log1pf(float x);
13001 long double log1pl(long double x);
13002 </pre>
13003 <p><b>Description</b>
13004 <p><!--para 2 -->
13005 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note235"><b>235)</b></a></sup>
13006 A domain error occurs if the argument is less than -1. A pole error may occur if the
13007 argument equals -1.
13008 <p><b>Returns</b>
13009 <p><!--para 3 -->
13010 The log1p functions return loge (1 + x).
13015 <!--page 263 -->
13017 <p><b>Footnotes</b>
13018 <p><small><a name="note235" href="#note235">235)</a> For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
13019 </small>
13023 <p><b>Synopsis</b>
13024 <p><!--para 1 -->
13025 <pre>
13027 double log2(double x);
13028 float log2f(float x);
13029 long double log2l(long double x);
13030 </pre>
13031 <p><b>Description</b>
13032 <p><!--para 2 -->
13033 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
13034 argument is less than zero. A pole error may occur if the argument is zero.
13035 <p><b>Returns</b>
13036 <p><!--para 3 -->
13037 The log2 functions return log2 x.
13041 <p><b>Synopsis</b>
13042 <p><!--para 1 -->
13043 <pre>
13045 double logb(double x);
13046 float logbf(float x);
13047 long double logbl(long double x);
13048 </pre>
13049 <p><b>Description</b>
13050 <p><!--para 2 -->
13051 The logb functions extract the exponent of x, as a signed integer value in floating-point
13052 format. If x is subnormal it is treated as though it were normalized; thus, for positive
13053 finite x,
13054 <pre>
13055 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX
13056 </pre>
13057 A domain error or pole error may occur if the argument is zero.
13058 <p><b>Returns</b>
13059 <p><!--para 3 -->
13060 The logb functions return the signed exponent of x.
13064 <p><b>Synopsis</b>
13065 <p><!--para 1 -->
13066 <pre>
13068 double modf(double value, double *iptr);
13069 float modff(float value, float *iptr);
13070 long double modfl(long double value, long double *iptr);
13071 </pre>
13072 <p><b>Description</b>
13073 <p><!--para 2 -->
13074 The modf functions break the argument value into integral and fractional parts, each of
13075 which has the same type and sign as the argument. They store the integral part (in
13076 <!--page 264 -->
13077 floating-point format) in the object pointed to by iptr.
13078 <p><b>Returns</b>
13079 <p><!--para 3 -->
13080 The modf functions return the signed fractional part of value.
13084 <p><b>Synopsis</b>
13085 <p><!--para 1 -->
13086 <pre>
13088 double scalbn(double x, int n);
13089 float scalbnf(float x, int n);
13090 long double scalbnl(long double x, int n);
13091 double scalbln(double x, long int n);
13092 float scalblnf(float x, long int n);
13093 long double scalblnl(long double x, long int n);
13094 </pre>
13095 <p><b>Description</b>
13096 <p><!--para 2 -->
13097 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
13098 normally by computing FLT_RADIXn explicitly. A range error may occur.
13099 <p><b>Returns</b>
13100 <p><!--para 3 -->
13101 The scalbn and scalbln functions return x x FLT_RADIXn .
13108 <p><b>Synopsis</b>
13109 <p><!--para 1 -->
13110 <pre>
13112 double cbrt(double x);
13113 float cbrtf(float x);
13114 long double cbrtl(long double x);
13115 </pre>
13116 <p><b>Description</b>
13117 <p><!--para 2 -->
13118 The cbrt functions compute the real cube root of x.
13119 <p><b>Returns</b>
13120 <p><!--para 3 -->
13121 The cbrt functions return x1/3 .
13122 <!--page 265 -->
13126 <p><b>Synopsis</b>
13127 <p><!--para 1 -->
13128 <pre>
13130 double fabs(double x);
13131 float fabsf(float x);
13132 long double fabsl(long double x);
13133 </pre>
13134 <p><b>Description</b>
13135 <p><!--para 2 -->
13136 The fabs functions compute the absolute value of a floating-point number x.
13137 <p><b>Returns</b>
13138 <p><!--para 3 -->
13139 The fabs functions return | x |.
13143 <p><b>Synopsis</b>
13144 <p><!--para 1 -->
13145 <pre>
13147 double hypot(double x, double y);
13148 float hypotf(float x, float y);
13149 long double hypotl(long double x, long double y);
13150 </pre>
13151 <p><b>Description</b>
13152 <p><!--para 2 -->
13153 The hypot functions compute the square root of the sum of the squares of x and y,
13154 without undue overflow or underflow. A range error may occur.
13155 <p><!--para 3 -->
13156 <p><b>Returns</b>
13157 <p><!--para 4 -->
13158 The hypot functions return (sqrt)x2 + y2 .
13159 <pre>
13160 -
13161 -----
13162 </pre>
13166 <p><b>Synopsis</b>
13167 <p><!--para 1 -->
13168 <pre>
13170 double pow(double x, double y);
13171 float powf(float x, float y);
13172 long double powl(long double x, long double y);
13173 </pre>
13174 <p><b>Description</b>
13175 <p><!--para 2 -->
13176 The pow functions compute x raised to the power y. A domain error occurs if x is finite
13177 and negative and y is finite and not an integer value. A range error may occur. A domain
13178 error may occur if x is zero and y is zero. A domain error or pole error may occur if x is
13179 zero and y is less than zero.
13180 <!--page 266 -->
13181 <p><b>Returns</b>
13182 <p><!--para 3 -->
13183 The pow functions return xy .
13187 <p><b>Synopsis</b>
13188 <p><!--para 1 -->
13189 <pre>
13191 double sqrt(double x);
13192 float sqrtf(float x);
13193 long double sqrtl(long double x);
13194 </pre>
13195 <p><b>Description</b>
13196 <p><!--para 2 -->
13197 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
13198 the argument is less than zero.
13199 <p><b>Returns</b>
13200 <p><!--para 3 -->
13201 The sqrt functions return (sqrt)x.
13202 <pre>
13203 -
13204 -
13205 </pre>
13212 <p><b>Synopsis</b>
13213 <p><!--para 1 -->
13214 <pre>
13216 double erf(double x);
13217 float erff(float x);
13218 long double erfl(long double x);
13219 </pre>
13220 <p><b>Description</b>
13221 <p><!--para 2 -->
13222 The erf functions compute the error function of x.
13223 <p><b>Returns</b>
13224 <p><!--para 3 -->
13225 <pre>
13226 2 x
13227 (integral) e-t dt.
13228 2
13229 </pre>
13230 The erf functions return erf x =
13231 <pre>
13232 (sqrt)pi
13233 -
13234 - 0
13235 </pre>
13240 <p><b>Synopsis</b>
13241 <p><!--para 1 -->
13242 <pre>
13244 double erfc(double x);
13245 float erfcf(float x);
13246 long double erfcl(long double x);
13247 </pre>
13248 <p><b>Description</b>
13249 <p><!--para 2 -->
13250 The erfc functions compute the complementary error function of x. A range error
13251 occurs if x is too large.
13252 <!--page 267 -->
13253 <p><b>Returns</b>
13254 <p><!--para 3 -->
13255 <pre>
13256 2 (inf)
13257 (integral) e-t dt.
13258 2
13259 </pre>
13260 The erfc functions return erfc x = 1 - erf x =
13261 <pre>
13262 (sqrt)pi
13263 -
13264 - x
13265 </pre>
13270 <p><b>Synopsis</b>
13271 <p><!--para 1 -->
13272 <pre>
13274 double lgamma(double x);
13275 float lgammaf(float x);
13276 long double lgammal(long double x);
13277 </pre>
13278 <p><b>Description</b>
13279 <p><!--para 2 -->
13280 The lgamma functions compute the natural logarithm of the absolute value of gamma of
13281 x. A range error occurs if x is too large. A pole error may occur if x is a negative integer
13282 or zero.
13283 <p><b>Returns</b>
13284 <p><!--para 3 -->
13285 The lgamma functions return loge | (Gamma)(x) |.
13289 <p><b>Synopsis</b>
13290 <p><!--para 1 -->
13291 <pre>
13293 double tgamma(double x);
13294 float tgammaf(float x);
13295 long double tgammal(long double x);
13296 </pre>
13297 <p><b>Description</b>
13298 <p><!--para 2 -->
13299 The tgamma functions compute the gamma function of x. A domain error or pole error
13300 may occur if x is a negative integer or zero. A range error occurs if the magnitude of x is
13301 too large and may occur if the magnitude of x is too small.
13302 <p><b>Returns</b>
13303 <p><!--para 3 -->
13304 The tgamma functions return (Gamma)(x).
13305 <!--page 268 -->
13312 <p><b>Synopsis</b>
13313 <p><!--para 1 -->
13314 <pre>
13316 double ceil(double x);
13317 float ceilf(float x);
13318 long double ceill(long double x);
13319 </pre>
13320 <p><b>Description</b>
13321 <p><!--para 2 -->
13322 The ceil functions compute the smallest integer value not less than x.
13323 <p><b>Returns</b>
13324 <p><!--para 3 -->
13325 The ceil functions return [^x^], expressed as a floating-point number.
13329 <p><b>Synopsis</b>
13330 <p><!--para 1 -->
13331 <pre>
13333 double floor(double x);
13334 float floorf(float x);
13335 long double floorl(long double x);
13336 </pre>
13337 <p><b>Description</b>
13338 <p><!--para 2 -->
13339 The floor functions compute the largest integer value not greater than x.
13340 <p><b>Returns</b>
13341 <p><!--para 3 -->
13342 The floor functions return [_x_], expressed as a floating-point number.
13346 <p><b>Synopsis</b>
13347 <p><!--para 1 -->
13348 <pre>
13350 double nearbyint(double x);
13351 float nearbyintf(float x);
13352 long double nearbyintl(long double x);
13353 </pre>
13354 <p><b>Description</b>
13355 <p><!--para 2 -->
13356 The nearbyint functions round their argument to an integer value in floating-point
13357 format, using the current rounding direction and without raising the ''inexact'' floating-
13358 point exception.
13359 <!--page 269 -->
13360 <p><b>Returns</b>
13361 <p><!--para 3 -->
13362 The nearbyint functions return the rounded integer value.
13366 <p><b>Synopsis</b>
13367 <p><!--para 1 -->
13368 <pre>
13370 double rint(double x);
13371 float rintf(float x);
13372 long double rintl(long double x);
13373 </pre>
13374 <p><b>Description</b>
13375 <p><!--para 2 -->
13376 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
13377 rint functions may raise the ''inexact'' floating-point exception if the result differs in
13378 value from the argument.
13379 <p><b>Returns</b>
13380 <p><!--para 3 -->
13381 The rint functions return the rounded integer value.
13385 <p><b>Synopsis</b>
13386 <p><!--para 1 -->
13387 <pre>
13389 long int lrint(double x);
13390 long int lrintf(float x);
13391 long int lrintl(long double x);
13392 long long int llrint(double x);
13393 long long int llrintf(float x);
13394 long long int llrintl(long double x);
13395 </pre>
13396 <p><b>Description</b>
13397 <p><!--para 2 -->
13398 The lrint and llrint functions round their argument to the nearest integer value,
13399 rounding according to the current rounding direction. If the rounded value is outside the
13400 range of the return type, the numeric result is unspecified and a domain error or range
13401 error may occur.
13402 <p><b>Returns</b>
13403 <p><!--para 3 -->
13404 The lrint and llrint functions return the rounded integer value.
13405 <!--page 270 -->
13409 <p><b>Synopsis</b>
13410 <p><!--para 1 -->
13411 <pre>
13413 double round(double x);
13414 float roundf(float x);
13415 long double roundl(long double x);
13416 </pre>
13417 <p><b>Description</b>
13418 <p><!--para 2 -->
13419 The round functions round their argument to the nearest integer value in floating-point
13420 format, rounding halfway cases away from zero, regardless of the current rounding
13421 direction.
13422 <p><b>Returns</b>
13423 <p><!--para 3 -->
13424 The round functions return the rounded integer value.
13428 <p><b>Synopsis</b>
13429 <p><!--para 1 -->
13430 <pre>
13432 long int lround(double x);
13433 long int lroundf(float x);
13434 long int lroundl(long double x);
13435 long long int llround(double x);
13436 long long int llroundf(float x);
13437 long long int llroundl(long double x);
13438 </pre>
13439 <p><b>Description</b>
13440 <p><!--para 2 -->
13441 The lround and llround functions round their argument to the nearest integer value,
13442 rounding halfway cases away from zero, regardless of the current rounding direction. If
13443 the rounded value is outside the range of the return type, the numeric result is unspecified
13444 and a domain error or range error may occur.
13445 <p><b>Returns</b>
13446 <p><!--para 3 -->
13447 The lround and llround functions return the rounded integer value.
13451 <p><b>Synopsis</b>
13452 <p><!--para 1 -->
13453 <!--page 271 -->
13454 <pre>
13456 double trunc(double x);
13457 float truncf(float x);
13458 long double truncl(long double x);
13459 </pre>
13460 <p><b>Description</b>
13461 <p><!--para 2 -->
13462 The trunc functions round their argument to the integer value, in floating format,
13463 nearest to but no larger in magnitude than the argument.
13464 <p><b>Returns</b>
13465 <p><!--para 3 -->
13466 The trunc functions return the truncated integer value.
13473 <p><b>Synopsis</b>
13474 <p><!--para 1 -->
13475 <pre>
13477 double fmod(double x, double y);
13478 float fmodf(float x, float y);
13479 long double fmodl(long double x, long double y);
13480 </pre>
13481 <p><b>Description</b>
13482 <p><!--para 2 -->
13483 The fmod functions compute the floating-point remainder of x/y.
13484 <p><b>Returns</b>
13485 <p><!--para 3 -->
13486 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
13487 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
13488 whether a domain error occurs or the fmod functions return zero is implementation-
13489 defined.
13493 <p><b>Synopsis</b>
13494 <p><!--para 1 -->
13495 <pre>
13497 double remainder(double x, double y);
13498 float remainderf(float x, float y);
13499 long double remainderl(long double x, long double y);
13500 </pre>
13501 <p><b>Description</b>
13502 <p><!--para 2 -->
13503 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note236"><b>236)</b></a></sup>
13508 <!--page 272 -->
13509 <p><b>Returns</b>
13510 <p><!--para 3 -->
13511 The remainder functions return x REM y. If y is zero, whether a domain error occurs
13512 or the functions return zero is implementation defined.
13514 <p><b>Footnotes</b>
13515 <p><small><a name="note236" href="#note236">236)</a> ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
13516 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
13517 | n - x/y | = 1/2, then n is even. If r = 0, its sign shall be that of x.'' This definition is applicable for *
13518 all implementations.
13519 </small>
13523 <p><b>Synopsis</b>
13524 <p><!--para 1 -->
13525 <pre>
13527 double remquo(double x, double y, int *quo);
13528 float remquof(float x, float y, int *quo);
13529 long double remquol(long double x, long double y,
13530 int *quo);
13531 </pre>
13532 <p><b>Description</b>
13533 <p><!--para 2 -->
13534 The remquo functions compute the same remainder as the remainder functions. In
13535 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
13536 magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
13537 n is an implementation-defined integer greater than or equal to 3.
13538 <p><b>Returns</b>
13539 <p><!--para 3 -->
13540 The remquo functions return x REM y. If y is zero, the value stored in the object
13541 pointed to by quo is unspecified and whether a domain error occurs or the functions
13542 return zero is implementation defined.
13549 <p><b>Synopsis</b>
13550 <p><!--para 1 -->
13551 <pre>
13553 double copysign(double x, double y);
13554 float copysignf(float x, float y);
13555 long double copysignl(long double x, long double y);
13556 </pre>
13557 <p><b>Description</b>
13558 <p><!--para 2 -->
13559 The copysign functions produce a value with the magnitude of x and the sign of y.
13560 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
13561 represent a signed zero but do not treat negative zero consistently in arithmetic
13562 operations, the copysign functions regard the sign of zero as positive.
13563 <p><b>Returns</b>
13564 <p><!--para 3 -->
13565 The copysign functions return a value with the magnitude of x and the sign of y.
13566 <!--page 273 -->
13570 <p><b>Synopsis</b>
13571 <p><!--para 1 -->
13572 <pre>
13574 double nan(const char *tagp);
13575 float nanf(const char *tagp);
13576 long double nanl(const char *tagp);
13577 </pre>
13578 <p><b>Description</b>
13579 <p><!--para 2 -->
13584 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
13585 and strtold.
13586 <p><b>Returns</b>
13587 <p><!--para 3 -->
13588 The nan functions return a quiet NaN, if available, with content indicated through tagp.
13589 If the implementation does not support quiet NaNs, the functions return zero.
13590 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
13594 <p><b>Synopsis</b>
13595 <p><!--para 1 -->
13596 <pre>
13598 double nextafter(double x, double y);
13599 float nextafterf(float x, float y);
13600 long double nextafterl(long double x, long double y);
13601 </pre>
13602 <p><b>Description</b>
13603 <p><!--para 2 -->
13604 The nextafter functions determine the next representable value, in the type of the
13605 function, after x in the direction of y, where x and y are first converted to the type of the
13606 function.<sup><a href="#note237"><b>237)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
13607 if the magnitude of x is the largest finite value representable in the type and the result is
13608 infinite or not representable in the type.
13609 <p><b>Returns</b>
13610 <p><!--para 3 -->
13611 The nextafter functions return the next representable value in the specified format
13612 after x in the direction of y.
13615 <!--page 274 -->
13617 <p><b>Footnotes</b>
13618 <p><small><a name="note237" href="#note237">237)</a> The argument values are converted to the type of the function, even by a macro implementation of the
13619 function.
13620 </small>
13624 <p><b>Synopsis</b>
13625 <p><!--para 1 -->
13626 <pre>
13628 double nexttoward(double x, long double y);
13629 float nexttowardf(float x, long double y);
13630 long double nexttowardl(long double x, long double y);
13631 </pre>
13632 <p><b>Description</b>
13633 <p><!--para 2 -->
13634 The nexttoward functions are equivalent to the nextafter functions except that the
13635 second parameter has type long double and the functions return y converted to the
13638 <p><b>Footnotes</b>
13639 <p><small><a name="note238" href="#note238">238)</a> The result of the nexttoward functions is determined in the type of the function, without loss of
13640 range or precision in a floating second argument.
13641 </small>
13644 <h4><a name="7.12.12" href="#7.12.12">7.12.12 Maximum, minimum, and positive difference functions</a></h4>
13648 <p><b>Synopsis</b>
13649 <p><!--para 1 -->
13650 <pre>
13652 double fdim(double x, double y);
13653 float fdimf(float x, float y);
13654 long double fdiml(long double x, long double y);
13655 </pre>
13656 <p><b>Description</b>
13657 <p><!--para 2 -->
13658 The fdim functions determine the positive difference between their arguments:
13659 <pre>
13660 {x - y if x > y
13661 {
13662 {+0 if x <= y
13663 </pre>
13664 A range error may occur.
13665 <p><b>Returns</b>
13666 <p><!--para 3 -->
13667 The fdim functions return the positive difference value.
13671 <p><b>Synopsis</b>
13672 <p><!--para 1 -->
13673 <pre>
13675 double fmax(double x, double y);
13676 float fmaxf(float x, float y);
13677 long double fmaxl(long double x, long double y);
13678 </pre>
13682 <!--page 275 -->
13683 <p><b>Description</b>
13684 <p><!--para 2 -->
13685 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note239"><b>239)</b></a></sup>
13686 <p><b>Returns</b>
13687 <p><!--para 3 -->
13688 The fmax functions return the maximum numeric value of their arguments.
13690 <p><b>Footnotes</b>
13691 <p><small><a name="note239" href="#note239">239)</a> NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
13693 </small>
13697 <p><b>Synopsis</b>
13698 <p><!--para 1 -->
13699 <pre>
13701 double fmin(double x, double y);
13702 float fminf(float x, float y);
13703 long double fminl(long double x, long double y);
13704 </pre>
13705 <p><b>Description</b>
13706 <p><!--para 2 -->
13707 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note240"><b>240)</b></a></sup>
13708 <p><b>Returns</b>
13709 <p><!--para 3 -->
13710 The fmin functions return the minimum numeric value of their arguments.
13712 <p><b>Footnotes</b>
13713 <p><small><a name="note240" href="#note240">240)</a> The fmin functions are analogous to the fmax functions in their treatment of NaNs.
13714 </small>
13721 <p><b>Synopsis</b>
13722 <p><!--para 1 -->
13723 <pre>
13725 double fma(double x, double y, double z);
13726 float fmaf(float x, float y, float z);
13727 long double fmal(long double x, long double y,
13728 long double z);
13729 </pre>
13730 <p><b>Description</b>
13731 <p><!--para 2 -->
13732 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
13733 the value (as if) to infinite precision and round once to the result format, according to the
13734 current rounding mode. A range error may occur.
13735 <p><b>Returns</b>
13736 <p><!--para 3 -->
13737 The fma functions return (x x y) + z, rounded as one ternary operation.
13742 <!--page 276 -->
13746 <p><!--para 1 -->
13747 The relational and equality operators support the usual mathematical relationships
13748 between numeric values. For any ordered pair of numeric values exactly one of the
13749 relationships -- less, greater, and equal -- is true. Relational operators may raise the
13750 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
13751 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note241"><b>241)</b></a></sup> The following
13752 subclauses provide macros that are quiet (non floating-point exception raising) versions
13753 of the relational operators, and other comparison macros that facilitate writing efficient
13754 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
13755 the synopses in this subclause, real-floating indicates that the argument shall be an
13756 expression of real floating type<sup><a href="#note242"><b>242)</b></a></sup> (both arguments need not have the same type).<sup><a href="#note243"><b>243)</b></a></sup>
13758 <p><b>Footnotes</b>
13759 <p><small><a name="note241" href="#note241">241)</a> IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
13760 the operands compare unordered, as an error indicator for programs written without consideration of
13761 NaNs; the result in these cases is false.
13762 </small>
13763 <p><small><a name="note242" href="#note242">242)</a> If any argument is of integer type, or any other type that is not a real floating type, the behavior is
13764 undefined.
13765 </small>
13766 <p><small><a name="note243" href="#note243">243)</a> Whether an argument represented in a format wider than its semantic type is converted to the semantic
13767 type is unspecified.
13768 </small>
13772 <p><b>Synopsis</b>
13773 <p><!--para 1 -->
13774 <pre>
13776 int isgreater(real-floating x, real-floating y);
13777 </pre>
13778 <p><b>Description</b>
13779 <p><!--para 2 -->
13780 The isgreater macro determines whether its first argument is greater than its second
13781 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
13782 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
13783 exception when x and y are unordered.
13784 <p><b>Returns</b>
13785 <p><!--para 3 -->
13786 The isgreater macro returns the value of (x) > (y).
13790 <p><b>Synopsis</b>
13791 <p><!--para 1 -->
13792 <pre>
13794 int isgreaterequal(real-floating x, real-floating y);
13795 </pre>
13800 <!--page 277 -->
13801 <p><b>Description</b>
13802 <p><!--para 2 -->
13803 The isgreaterequal macro determines whether its first argument is greater than or
13804 equal to its second argument. The value of isgreaterequal(x, y) is always equal
13805 to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
13806 not raise the ''invalid'' floating-point exception when x and y are unordered.
13807 <p><b>Returns</b>
13808 <p><!--para 3 -->
13809 The isgreaterequal macro returns the value of (x) >= (y).
13813 <p><b>Synopsis</b>
13814 <p><!--para 1 -->
13815 <pre>
13817 int isless(real-floating x, real-floating y);
13818 </pre>
13819 <p><b>Description</b>
13820 <p><!--para 2 -->
13821 The isless macro determines whether its first argument is less than its second
13822 argument. The value of isless(x, y) is always equal to (x) < (y); however,
13823 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
13824 exception when x and y are unordered.
13825 <p><b>Returns</b>
13826 <p><!--para 3 -->
13827 The isless macro returns the value of (x) < (y).
13831 <p><b>Synopsis</b>
13832 <p><!--para 1 -->
13833 <pre>
13835 int islessequal(real-floating x, real-floating y);
13836 </pre>
13837 <p><b>Description</b>
13838 <p><!--para 2 -->
13839 The islessequal macro determines whether its first argument is less than or equal to
13840 its second argument. The value of islessequal(x, y) is always equal to
13841 (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
13842 the ''invalid'' floating-point exception when x and y are unordered.
13843 <p><b>Returns</b>
13844 <p><!--para 3 -->
13845 The islessequal macro returns the value of (x) <= (y).
13846 <!--page 278 -->
13850 <p><b>Synopsis</b>
13851 <p><!--para 1 -->
13852 <pre>
13854 int islessgreater(real-floating x, real-floating y);
13855 </pre>
13856 <p><b>Description</b>
13857 <p><!--para 2 -->
13858 The islessgreater macro determines whether its first argument is less than or
13859 greater than its second argument. The islessgreater(x, y) macro is similar to
13860 (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
13861 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
13862 and y twice).
13863 <p><b>Returns</b>
13864 <p><!--para 3 -->
13865 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
13869 <p><b>Synopsis</b>
13870 <p><!--para 1 -->
13871 <pre>
13873 int isunordered(real-floating x, real-floating y);
13874 </pre>
13875 <p><b>Description</b>
13876 <p><!--para 2 -->
13877 The isunordered macro determines whether its arguments are unordered.
13878 <p><b>Returns</b>
13879 <p><!--para 3 -->
13880 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
13881 <!--page 279 -->
13885 <p><!--para 1 -->
13886 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
13887 one type, for bypassing the normal function call and return discipline.<sup><a href="#note244"><b>244)</b></a></sup>
13888 <p><!--para 2 -->
13889 The type declared is
13890 <pre>
13891 jmp_buf
13892 </pre>
13893 which is an array type suitable for holding the information needed to restore a calling
13894 environment. The environment of a call to the setjmp macro consists of information
13895 sufficient for a call to the longjmp function to return execution to the correct block and
13896 invocation of that block, were it called recursively. It does not include the state of the
13897 floating-point status flags, of open files, or of any other component of the abstract
13898 machine.
13899 <p><!--para 3 -->
13900 It is unspecified whether setjmp is a macro or an identifier declared with external
13901 linkage. If a macro definition is suppressed in order to access an actual function, or a
13902 program defines an external identifier with the name setjmp, the behavior is undefined.
13904 <p><b>Footnotes</b>
13905 <p><small><a name="note244" href="#note244">244)</a> These functions are useful for dealing with unusual conditions encountered in a low-level function of
13906 a program.
13907 </small>
13914 <p><b>Synopsis</b>
13915 <p><!--para 1 -->
13916 <pre>
13918 int setjmp(jmp_buf env);
13919 </pre>
13920 <p><b>Description</b>
13921 <p><!--para 2 -->
13922 The setjmp macro saves its calling environment in its jmp_buf argument for later use
13923 by the longjmp function.
13924 <p><b>Returns</b>
13925 <p><!--para 3 -->
13926 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
13927 return is from a call to the longjmp function, the setjmp macro returns a nonzero
13928 value.
13929 <p><b>Environmental limits</b>
13930 <p><!--para 4 -->
13931 An invocation of the setjmp macro shall appear only in one of the following contexts:
13932 <ul>
13933 <li> the entire controlling expression of a selection or iteration statement;
13934 <li> one operand of a relational or equality operator with the other operand an integer
13935 constant expression, with the resulting expression being the entire controlling
13938 <!--page 280 -->
13939 expression of a selection or iteration statement;
13940 <li> the operand of a unary ! operator with the resulting expression being the entire
13941 controlling expression of a selection or iteration statement; or
13942 <li> the entire expression of an expression statement (possibly cast to void).
13943 </ul>
13944 <p><!--para 5 -->
13945 If the invocation appears in any other context, the behavior is undefined.
13952 <p><b>Synopsis</b>
13953 <p><!--para 1 -->
13954 <pre>
13956 _Noreturn void longjmp(jmp_buf env, int val);
13957 </pre>
13958 <p><b>Description</b>
13959 <p><!--para 2 -->
13960 The longjmp function restores the environment saved by the most recent invocation of
13961 the setjmp macro in the same invocation of the program with the corresponding
13962 jmp_buf argument. If there has been no such invocation, or if the function containing
13963 the invocation of the setjmp macro has terminated execution<sup><a href="#note245"><b>245)</b></a></sup> in the interim, or if the
13964 invocation of the setjmp macro was within the scope of an identifier with variably
13965 modified type and execution has left that scope in the interim, the behavior is undefined.
13966 <p><!--para 3 -->
13967 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note246"><b>246)</b></a></sup>
13968 have state, as of the time the longjmp function was called, except that the values of
13969 objects of automatic storage duration that are local to the function containing the
13970 invocation of the corresponding setjmp macro that do not have volatile-qualified type
13971 and have been changed between the setjmp invocation and longjmp call are
13972 indeterminate.
13973 <p><b>Returns</b>
13974 <p><!--para 4 -->
13975 After longjmp is completed, program execution continues as if the corresponding
13976 invocation of the setjmp macro had just returned the value specified by val. The
13977 longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
13978 the setjmp macro returns the value 1.
13979 <p><!--para 5 -->
13980 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
13981 might cause memory associated with a variable length array object to be squandered.
13986 <!--page 281 -->
13987 <!--page 282 -->
13988 <pre>
13990 jmp_buf buf;
13991 void g(int n);
13992 void h(int n);
13993 int n = 6;
13994 void f(void)
13995 {
13996 int x[n]; // valid: f is not terminated
13997 setjmp(buf);
13998 g(n);
13999 }
14000 void g(int n)
14001 {
14002 int a[n]; // a may remain allocated
14003 h(n);
14004 }
14005 void h(int n)
14006 {
14007 int b[n]; // b may remain allocated
14008 longjmp(buf, 2); // might cause memory loss
14009 }
14010 </pre>
14012 <p><b>Footnotes</b>
14013 <p><small><a name="note245" href="#note245">245)</a> For example, by executing a return statement or because another longjmp call has caused a
14014 transfer to a setjmp invocation in a function earlier in the set of nested calls.
14015 </small>
14016 <p><small><a name="note246" href="#note246">246)</a> This includes, but is not limited to, the floating-point status flags and the state of open files.
14017 </small>
14021 <p><!--para 1 -->
14022 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
14023 for handling various signals (conditions that may be reported during program execution).
14024 <p><!--para 2 -->
14025 The type defined is
14026 <pre>
14027 sig_atomic_t
14028 </pre>
14029 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
14030 an atomic entity, even in the presence of asynchronous interrupts.
14031 <p><!--para 3 -->
14032 The macros defined are
14033 <pre>
14034 SIG_DFL
14035 SIG_ERR
14036 SIG_IGN
14037 </pre>
14038 which expand to constant expressions with distinct values that have type compatible with
14039 the second argument to, and the return value of, the signal function, and whose values
14040 compare unequal to the address of any declarable function; and the following, which
14041 expand to positive integer constant expressions with type int and distinct values that are
14042 the signal numbers, each corresponding to the specified condition:
14043 <pre>
14044 SIGABRT abnormal termination, such as is initiated by the abort function
14045 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
14046 resulting in overflow
14047 SIGILL detection of an invalid function image, such as an invalid instruction
14048 SIGINT receipt of an interactive attention signal
14049 SIGSEGV an invalid access to storage
14050 SIGTERM a termination request sent to the program
14051 </pre>
14052 <p><!--para 4 -->
14053 An implementation need not generate any of these signals, except as a result of explicit
14054 calls to the raise function. Additional signals and pointers to undeclarable functions,
14055 with macro definitions beginning, respectively, with the letters SIG and an uppercase
14056 letter or with SIG_ and an uppercase letter,<sup><a href="#note247"><b>247)</b></a></sup> may also be specified by the
14057 implementation. The complete set of signals, their semantics, and their default handling
14058 is implementation-defined; all signal numbers shall be positive.
14063 <!--page 283 -->
14065 <p><b>Footnotes</b>
14066 <p><small><a name="note247" href="#note247">247)</a> See ''future library directions'' (<a href="#7.30.6">7.30.6</a>). The names of the signal numbers reflect the following terms
14067 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
14068 and termination.
14069 </small>
14076 <p><b>Synopsis</b>
14077 <p><!--para 1 -->
14078 <pre>
14080 void (*signal(int sig, void (*func)(int)))(int);
14081 </pre>
14082 <p><b>Description</b>
14083 <p><!--para 2 -->
14084 The signal function chooses one of three ways in which receipt of the signal number
14085 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
14086 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
14087 Otherwise, func shall point to a function to be called when that signal occurs. An
14088 invocation of such a function because of a signal, or (recursively) of any further functions
14089 called by that invocation (other than functions in the standard library),<sup><a href="#note248"><b>248)</b></a></sup> is called a
14090 signal handler.
14091 <p><!--para 3 -->
14092 When a signal occurs and func points to a function, it is implementation-defined
14093 whether the equivalent of signal(sig, SIG_DFL); is executed or the
14094 implementation prevents some implementation-defined set of signals (at least including
14095 sig) from occurring until the current signal handling has completed; in the case of
14096 SIGILL, the implementation may alternatively define that no action is taken. Then the
14097 equivalent of (*func)(sig); is executed. If and when the function returns, if the
14098 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
14099 value corresponding to a computational exception, the behavior is undefined; otherwise
14100 the program will resume execution at the point it was interrupted.
14101 <p><!--para 4 -->
14102 If the signal occurs as the result of calling the abort or raise function, the signal
14103 handler shall not call the raise function.
14104 <p><!--para 5 -->
14105 If the signal occurs other than as the result of calling the abort or raise function, the
14106 behavior is undefined if the signal handler refers to any object with static or thread
14107 storage duration that is not a lock-free atomic object other than by assigning a value to an
14108 object declared as volatile sig_atomic_t, or the signal handler calls any function
14109 in the standard library other than the abort function, the _Exit function, the
14110 quick_exit function, or the signal function with the first argument equal to the
14111 signal number corresponding to the signal that caused the invocation of the handler.
14112 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
14116 <!--page 284 -->
14117 <p><!--para 6 -->
14118 At program startup, the equivalent of
14119 <pre>
14120 signal(sig, SIG_IGN);
14121 </pre>
14122 may be executed for some signals selected in an implementation-defined manner; the
14123 equivalent of
14124 <pre>
14125 signal(sig, SIG_DFL);
14126 </pre>
14127 is executed for all other signals defined by the implementation.
14128 <p><!--para 7 -->
14129 The implementation shall behave as if no library function calls the signal function.
14130 <p><b>Returns</b>
14131 <p><!--para 8 -->
14132 If the request can be honored, the signal function returns the value of func for the
14133 most recent successful call to signal for the specified signal sig. Otherwise, a value of
14134 SIG_ERR is returned and a positive value is stored in errno.
14135 <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
14136 _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>).
14138 <p><b>Footnotes</b>
14139 <p><small><a name="note248" href="#note248">248)</a> This includes functions called indirectly via standard library functions (e.g., a SIGABRT handler
14140 called via the abort function).
14141 </small>
14142 <p><small><a name="note249" href="#note249">249)</a> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
14143 </small>
14150 <p><b>Synopsis</b>
14151 <p><!--para 1 -->
14152 <pre>
14154 int raise(int sig);
14155 </pre>
14156 <p><b>Description</b>
14157 <p><!--para 2 -->
14158 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
14159 signal handler is called, the raise function shall not return until after the signal handler
14160 does.
14161 <p><b>Returns</b>
14162 <p><!--para 3 -->
14163 The raise function returns zero if successful, nonzero if unsuccessful.
14164 <!--page 285 -->
14168 <p><!--para 1 -->
14170 <p><!--para 2 -->
14171 The macro
14172 <pre>
14173 alignas
14174 </pre>
14175 expands to _Alignas.
14176 <p><!--para 3 -->
14177 The remaining macro is suitable for use in #if preprocessing directives. It is
14178 <pre>
14179 __alignas_is_defined
14180 </pre>
14181 which expands to the integer constant 1.
14182 <!--page 286 -->
14186 <p><!--para 1 -->
14187 The header <a href="#7.16"><stdarg.h></a> declares a type and defines four macros, for advancing
14188 through a list of arguments whose number and types are not known to the called function
14189 when it is translated.
14190 <p><!--para 2 -->
14191 A function may be called with a variable number of arguments of varying types. As
14192 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
14193 parameter plays a special role in the access mechanism, and will be designated parmN in
14194 this description.
14195 <p><!--para 3 -->
14196 The type declared is
14197 <pre>
14198 va_list
14199 </pre>
14200 which is a complete object type suitable for holding information needed by the macros
14201 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
14202 desired, the called function shall declare an object (generally referred to as ap in this
14203 subclause) having type va_list. The object ap may be passed as an argument to
14204 another function; if that function invokes the va_arg macro with parameter ap, the
14205 value of ap in the calling function is indeterminate and shall be passed to the va_end
14208 <p><b>Footnotes</b>
14209 <p><small><a name="note250" href="#note250">250)</a> It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
14210 case the original function may make further use of the original list after the other function returns.
14211 </small>
14215 <p><!--para 1 -->
14216 The va_start and va_arg macros described in this subclause shall be implemented
14217 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
14218 identifiers declared with external linkage. If a macro definition is suppressed in order to
14219 access an actual function, or a program defines an external identifier with the same name,
14220 the behavior is undefined. Each invocation of the va_start and va_copy macros
14221 shall be matched by a corresponding invocation of the va_end macro in the same
14222 function.
14226 <p><b>Synopsis</b>
14227 <p><!--para 1 -->
14228 <pre>
14230 type va_arg(va_list ap, type);
14231 </pre>
14232 <p><b>Description</b>
14233 <p><!--para 2 -->
14234 The va_arg macro expands to an expression that has the specified type and the value of
14235 the next argument in the call. The parameter ap shall have been initialized by the
14236 va_start or va_copy macro (without an intervening invocation of the va_end
14238 <!--page 287 -->
14239 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
14240 values of successive arguments are returned in turn. The parameter type shall be a type
14241 name specified such that the type of a pointer to an object that has the specified type can
14242 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
14243 type is not compatible with the type of the actual next argument (as promoted according
14244 to the default argument promotions), the behavior is undefined, except for the following
14245 cases:
14246 <ul>
14247 <li> one type is a signed integer type, the other type is the corresponding unsigned integer
14248 type, and the value is representable in both types;
14249 <li> one type is pointer to void and the other is a pointer to a character type.
14250 </ul>
14251 <p><b>Returns</b>
14252 <p><!--para 3 -->
14253 The first invocation of the va_arg macro after that of the va_start macro returns the
14254 value of the argument after that specified by parmN . Successive invocations return the
14255 values of the remaining arguments in succession.
14259 <p><b>Synopsis</b>
14260 <p><!--para 1 -->
14261 <pre>
14263 void va_copy(va_list dest, va_list src);
14264 </pre>
14265 <p><b>Description</b>
14266 <p><!--para 2 -->
14267 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
14268 been applied to dest followed by the same sequence of uses of the va_arg macro as
14269 had previously been used to reach the present state of src. Neither the va_copy nor
14270 va_start macro shall be invoked to reinitialize dest without an intervening
14271 invocation of the va_end macro for the same dest.
14272 <p><b>Returns</b>
14273 <p><!--para 3 -->
14274 The va_copy macro returns no value.
14278 <p><b>Synopsis</b>
14279 <p><!--para 1 -->
14280 <pre>
14282 void va_end(va_list ap);
14283 </pre>
14284 <p><b>Description</b>
14285 <p><!--para 2 -->
14286 The va_end macro facilitates a normal return from the function whose variable
14287 argument list was referred to by the expansion of the va_start macro, or the function
14288 containing the expansion of the va_copy macro, that initialized the va_list ap. The
14289 va_end macro may modify ap so that it is no longer usable (without being reinitialized
14290 <!--page 288 -->
14291 by the va_start or va_copy macro). If there is no corresponding invocation of the
14292 va_start or va_copy macro, or if the va_end macro is not invoked before the
14293 return, the behavior is undefined.
14294 <p><b>Returns</b>
14295 <p><!--para 3 -->
14296 The va_end macro returns no value.
14300 <p><b>Synopsis</b>
14301 <p><!--para 1 -->
14302 <pre>
14304 void va_start(va_list ap, parmN);
14305 </pre>
14306 <p><b>Description</b>
14307 <p><!--para 2 -->
14308 The va_start macro shall be invoked before any access to the unnamed arguments.
14309 <p><!--para 3 -->
14310 The va_start macro initializes ap for subsequent use by the va_arg and va_end
14311 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
14312 without an intervening invocation of the va_end macro for the same ap.
14313 <p><!--para 4 -->
14314 The parameter parmN is the identifier of the rightmost parameter in the variable
14315 parameter list in the function definition (the one just before the , ...). If the parameter
14316 parmN is declared with the register storage class, with a function or array type, or
14317 with a type that is not compatible with the type that results after application of the default
14318 argument promotions, the behavior is undefined.
14319 <p><b>Returns</b>
14320 <p><!--para 5 -->
14321 The va_start macro returns no value.
14322 <p><!--para 6 -->
14323 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
14324 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
14325 pointers is specified by the first argument to f1.
14326 <!--page 289 -->
14327 <pre>
14329 #define MAXARGS 31
14330 void f1(int n_ptrs, ...)
14331 {
14332 va_list ap;
14333 char *array[MAXARGS];
14334 int ptr_no = 0;
14335 if (n_ptrs > MAXARGS)
14336 n_ptrs = MAXARGS;
14337 va_start(ap, n_ptrs);
14338 while (ptr_no < n_ptrs)
14339 array[ptr_no++] = va_arg(ap, char *);
14340 va_end(ap);
14341 f2(n_ptrs, array);
14342 }
14343 </pre>
14344 Each call to f1 is required to have visible the definition of the function or a declaration such as
14345 <pre>
14346 void f1(int, ...);
14347 </pre>
14349 <p><!--para 7 -->
14350 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
14351 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
14352 is gathered again and passed to function f4.
14353 <!--page 290 -->
14354 <pre>
14356 #define MAXARGS 31
14357 void f3(int n_ptrs, int f4_after, ...)
14358 {
14359 va_list ap, ap_save;
14360 char *array[MAXARGS];
14361 int ptr_no = 0;
14362 if (n_ptrs > MAXARGS)
14363 n_ptrs = MAXARGS;
14364 va_start(ap, f4_after);
14365 while (ptr_no < n_ptrs) {
14366 array[ptr_no++] = va_arg(ap, char *);
14367 if (ptr_no == f4_after)
14368 va_copy(ap_save, ap);
14369 }
14370 va_end(ap);
14371 f2(n_ptrs, array);
14372 // Now process the saved copy.
14373 n_ptrs -= f4_after;
14374 ptr_no = 0;
14375 while (ptr_no < n_ptrs)
14376 array[ptr_no++] = va_arg(ap_save, char *);
14377 va_end(ap_save);
14378 f4(n_ptrs, array);
14379 }
14380 </pre>
14387 <p><!--para 1 -->
14388 The header <a href="#7.17"><stdatomic.h></a> defines several macros and declares several types and
14389 functions for performing atomic operations on data shared between threads.
14390 <p><!--para 2 -->
14391 Implementations that define the macro __STDC_NO_THREADS__ need not provide
14392 this header nor support any of its facilities.
14393 <p><!--para 3 -->
14394 The macros defined are the atomic lock-free macros
14395 <pre>
14396 ATOMIC_CHAR_LOCK_FREE
14397 ATOMIC_CHAR16_T_LOCK_FREE
14398 ATOMIC_CHAR32_T_LOCK_FREE
14399 ATOMIC_WCHAR_T_LOCK_FREE
14400 ATOMIC_SHORT_LOCK_FREE
14401 ATOMIC_INT_LOCK_FREE
14402 ATOMIC_LONG_LOCK_FREE
14403 ATOMIC_LLONG_LOCK_FREE
14404 ATOMIC_ADDRESS_LOCK_FREE
14405 </pre>
14406 which indicate the lock-free property of the corresponding atomic types (both signed and
14407 unsigned); and
14408 <pre>
14409 ATOMIC_FLAG_INIT
14410 </pre>
14411 which expands to an initializer for an object of type atomic_flag.
14412 <p><!--para 4 -->
14413 The types include
14414 <pre>
14415 memory_order
14416 </pre>
14417 which is an enumerated type whose enumerators identify memory ordering constraints;
14418 <pre>
14419 atomic_flag
14420 </pre>
14421 which is a structure type representing a lock-free, primitive atomic flag;
14422 <pre>
14423 atomic_bool
14424 </pre>
14425 which is a structure type representing the atomic analog of the type _Bool;
14426 <pre>
14427 atomic_address
14428 </pre>
14429 which is a structure type representing the atomic analog of a pointer type; and several
14430 atomic analogs of integer types.
14431 <p><!--para 5 -->
14432 In the following operation definitions:
14433 <ul>
14434 <li> An A refers to one of the atomic types.
14435 <!--page 291 -->
14436 <li> A C refers to its corresponding non-atomic type. The atomic_address atomic
14437 type corresponds to the void * non-atomic type.
14438 <li> An M refers to the type of the other argument for arithmetic operations. For atomic
14439 integer types, M is C. For atomic address types, M is ptrdiff_t.
14440 <li> The functions not ending in _explicit have the same semantics as the
14441 corresponding _explicit function with memory_order_seq_cst for the
14442 memory_order argument.
14443 </ul>
14444 <p><!--para 6 -->
14445 NOTE Many operations are volatile-qualified. The ''volatile as device register'' semantics have not
14446 changed in the standard. This qualification means that volatility is preserved when applying these
14447 operations to volatile objects.
14455 <p><b>Synopsis</b>
14456 <p><!--para 1 -->
14457 <pre>
14459 #define ATOMIC_VAR_INIT(C value)
14460 </pre>
14461 <p><b>Description</b>
14462 <p><!--para 2 -->
14463 The ATOMIC_VAR_INIT macro expands to a token sequence suitable for initializing an
14464 atomic object of a type that is initialization-compatible with value. An atomic object
14465 with automatic storage duration that is not explicitly initialized using
14466 ATOMIC_VAR_INIT is initially in an indeterminate state; however, the default (zero)
14467 initialization for objects with static or thread-local storage duration is guaranteed to
14468 produce a valid state.
14469 <p><!--para 3 -->
14470 Concurrent access to the variable being initialized, even via an atomic operation,
14471 constitutes a data race.
14472 <p><!--para 4 -->
14473 EXAMPLE
14474 <pre>
14475 atomic_int guide = ATOMIC_VAR_INIT(42);
14476 </pre>
14481 <p><b>Synopsis</b>
14482 <p><!--para 1 -->
14483 <pre>
14485 void atomic_init(volatile A *obj, C value);
14486 </pre>
14487 <p><b>Description</b>
14488 <p><!--para 2 -->
14489 The atomic_init generic function initializes the atomic object pointed to by obj to
14490 the value value, while also initializing any additional state that the implementation
14491 might need to carry for the atomic object.
14492 <!--page 292 -->
14493 <p><!--para 3 -->
14494 Although this function initializes an atomic object, it does not avoid data races;
14495 concurrent access to the variable being initialized, even via an atomic operation,
14496 constitutes a data race.
14497 <p><b>Returns</b>
14498 <p><!--para 4 -->
14499 The atomic_init generic function returns no value.
14500 <p><!--para 5 -->
14501 EXAMPLE
14502 <pre>
14503 atomic_int guide;
14504 atomic_init(&guide, 42);
14505 </pre>
14510 <p><!--para 1 -->
14511 The enumerated type memory_order specifies the detailed regular (non-atomic)
14512 memory synchronization operations as defined in <a href="#5.1.2.4">5.1.2.4</a> and may provide for operation
14513 ordering. Its enumeration constants are as follows:
14514 <pre>
14515 memory_order_relaxed
14516 memory_order_consume
14517 memory_order_acquire
14518 memory_order_release
14519 memory_order_acq_rel
14520 memory_order_seq_cst
14521 </pre>
14522 <p><!--para 2 -->
14523 For memory_order_relaxed, no operation orders memory.
14524 <p><!--para 3 -->
14525 For memory_order_release, memory_order_acq_rel, and
14526 memory_order_seq_cst, a store operation performs a release operation on the
14527 affected memory location.
14528 <p><!--para 4 -->
14529 For memory_order_acquire, memory_order_acq_rel, and
14530 memory_order_seq_cst, a load operation performs an acquire operation on the
14531 affected memory location.
14532 <p><!--para 5 -->
14533 For memory_order_consume, a load operation performs a consume operation on the
14534 affected memory location.
14535 <p><!--para 6 -->
14536 For memory_order_seq_cst, there shall be a single total order S on all operations,
14537 consistent with the ''happens before'' order and modification orders for all affected
14538 locations, such that each memory_order_seq_cst operation that loads a value
14539 observes either the last preceding modification according to this order S, or the result of
14540 an operation that is not memory_order_seq_cst.
14541 <p><!--para 7 -->
14542 NOTE 1 Although it is not explicitly required that S include lock operations, it can always be extended to
14543 an order that does include lock and unlock operations, since the ordering between those is already included
14544 in the ''happens before'' ordering.
14546 <p><!--para 8 -->
14547 NOTE 2 Atomic operations specifying memory_order_relaxed are relaxed only with respect to
14548 memory ordering. Implementations must still guarantee that any given atomic access to a particular atomic
14549 <!--page 293 -->
14550 object be indivisible with respect to all other atomic accesses to that object.
14552 <p><!--para 9 -->
14553 For an atomic operation B that reads the value of an atomic object M, if there is a
14554 memory_order_seq_cst fence X sequenced before B, then B observes either the
14555 last memory_order_seq_cst modification of M preceding X in the total order S or
14556 a later modification of M in its modification order.
14557 <p><!--para 10 -->
14558 For atomic operations A and B on an atomic object M, where A modifies M and B takes
14559 its value, if there is a memory_order_seq_cst fence X such that A is sequenced
14560 before X and B follows X in S, then B observes either the effects of A or a later
14561 modification of M in its modification order.
14562 <p><!--para 11 -->
14563 For atomic operations A and B on an atomic object M, where A modifies M and B takes
14564 its value, if there are memory_order_seq_cst fences X and Y such that A is
14565 sequenced before X, Y is sequenced before B, and X precedes Y in S, then B observes
14566 either the effects of A or a later modification of M in its modification order.
14567 <p><!--para 12 -->
14568 Atomic read-modify-write operations shall always read the last value (in the modification
14569 order) stored before the write associated with the read-modify-write operation.
14570 <p><!--para 13 -->
14571 An atomic store shall only store a value that has been computed from constants and
14572 program input values by a finite sequence of program evaluations, such that each
14573 evaluation observes the values of variables as computed by the last prior assignment in
14574 the sequence.<sup><a href="#note251"><b>251)</b></a></sup> The ordering of evaluations in this sequence shall be such that
14575 <ul>
14576 <li> If an evaluation B observes a value computed by A in a different thread, then B does
14577 not happen before A.
14578 <li> If an evaluation A is included in the sequence, then all evaluations that assign to the
14579 same variable and happen before A are also included.
14580 </ul>
14581 <p><!--para 14 -->
14582 NOTE 3 The second requirement disallows ''out-of-thin-air'', or ''speculative'' stores of atomics when
14583 relaxed atomics are used. Since unordered operations are involved, evaluations may appear in this
14584 sequence out of thread order. For example, with x and y initially zero,
14585 <pre>
14586 // Thread 1:
14587 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14588 atomic_store_explicit(&x, r1, memory_order_relaxed);
14589 </pre>
14591 <pre>
14592 // Thread 2:
14593 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14594 atomic_store_explicit(&y, 42, memory_order_relaxed);
14595 </pre>
14596 is allowed to produce r1 == 42 && r2 == 42. The sequence of evaluations justifying this consists of:
14601 <!--page 294 -->
14602 <pre>
14603 atomic_store_explicit(&y, 42, memory_order_relaxed);
14604 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14605 atomic_store_explicit(&x, r1, memory_order_relaxed);
14606 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14607 </pre>
14608 On the other hand,
14609 <pre>
14610 // Thread 1:
14611 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14612 atomic_store_explicit(&x, r1, memory_order_relaxed);
14613 </pre>
14615 <pre>
14616 // Thread 2:
14617 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14618 atomic_store_explicit(&y, r2, memory_order_relaxed);
14619 </pre>
14620 is not allowed to produce r1 == 42 && r2 = 42, since there is no sequence of evaluations that results
14621 in the computation of 42. In the absence of ''relaxed'' operations and read-modify-write operations with
14622 weaker than memory_order_acq_rel ordering, the second requirement has no impact.
14624 <p><b>Recommended practice</b>
14625 <p><!--para 15 -->
14626 The requirements do not forbid r1 == 42 && r2 == 42 in the following example,
14627 with x and y initially zero:
14628 <pre>
14629 // Thread 1:
14630 r1 = atomic_load_explicit(&x, memory_order_relaxed);
14631 if (r1 == 42)
14632 atomic_store_explicit(&y, r1, memory_order_relaxed);
14633 </pre>
14635 <pre>
14636 // Thread 2:
14637 r2 = atomic_load_explicit(&y, memory_order_relaxed);
14638 if (r2 == 42)
14639 atomic_store_explicit(&x, 42, memory_order_relaxed);
14640 </pre>
14641 However, this is not useful behavior, and implementations should not allow it.
14642 <p><!--para 16 -->
14643 Implementations should make atomic stores visible to atomic loads within a reasonable
14644 amount of time.
14646 <p><b>Footnotes</b>
14647 <p><small><a name="note251" href="#note251">251)</a> Among other implications, atomic variables shall not decay.
14648 </small>
14652 <p><b>Synopsis</b>
14653 <p><!--para 1 -->
14654 <pre>
14656 type kill_dependency(type y);
14657 </pre>
14658 <p><b>Description</b>
14659 <p><!--para 2 -->
14660 The kill_dependency macro terminates a dependency chain; the argument does not
14661 carry a dependency to the return value.
14662 <!--page 295 -->
14663 <p><b>Returns</b>
14664 <p><!--para 3 -->
14665 The kill_dependency macro returns the value of y.
14669 <p><!--para 1 -->
14670 This subclause introduces synchronization primitives called fences. Fences can have
14671 acquire semantics, release semantics, or both. A fence with acquire semantics is called
14672 an acquire fence; a fence with release semantics is called a release fence.
14673 <p><!--para 2 -->
14674 A release fence A synchronizes with an acquire fence B if there exist atomic operations
14675 X and Y , both operating on some atomic object M, such that A is sequenced before X, X
14676 modifies M, Y is sequenced before B, and Y reads the value written by X or a value
14677 written by any side effect in the hypothetical release sequence X would head if it were a
14678 release operation.
14679 <p><!--para 3 -->
14680 A release fence A synchronizes with an atomic operation B that performs an acquire
14681 operation on an atomic object M if there exists an atomic operation X such that A is
14682 sequenced before X, X modifies M, and B reads the value written by X or a value written
14683 by any side effect in the hypothetical release sequence X would head if it were a release
14684 operation.
14685 <p><!--para 4 -->
14686 An atomic operation A that is a release operation on an atomic object M synchronizes
14687 with an acquire fence B if there exists some atomic operation X on M such that X is
14688 sequenced before B and reads the value written by A or a value written by any side effect
14689 in the release sequence headed by A.
14693 <p><b>Synopsis</b>
14694 <p><!--para 1 -->
14695 <pre>
14697 void atomic_thread_fence(memory_order order);
14698 </pre>
14699 <p><b>Description</b>
14700 <p><!--para 2 -->
14701 Depending on the value of order, this operation:
14702 <ul>
14703 <li> has no effects, if order == memory_order_relaxed;
14704 <li> is an acquire fence, if order == memory_order_acquire or order ==
14705 memory_order_consume;
14706 <li> is a release fence, if order == memory_order_release;
14707 <li> is both an acquire fence and a release fence, if order ==
14708 memory_order_acq_rel;
14709 <li> is a sequentially consistent acquire and release fence, if order ==
14710 memory_order_seq_cst.
14711 <!--page 296 -->
14712 </ul>
14713 <p><b>Returns</b>
14714 <p><!--para 3 -->
14715 The atomic_thread_fence function returns no value.
14719 <p><b>Synopsis</b>
14720 <p><!--para 1 -->
14721 <pre>
14723 void atomic_signal_fence(memory_order order);
14724 </pre>
14725 <p><b>Description</b>
14726 <p><!--para 2 -->
14727 Equivalent to atomic_thread_fence(order), except that ''synchronizes with''
14728 relationships are established only between a thread and a signal handler executed in the
14729 same thread.
14730 <p><!--para 3 -->
14731 NOTE 1 The atomic_signal_fence function can be used to specify the order in which actions
14732 performed by the thread become visible to the signal handler.
14734 <p><!--para 4 -->
14735 NOTE 2 Compiler optimizations and reorderings of loads and stores are inhibited in the same way as with
14736 atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would
14737 have inserted are not emitted.
14739 <p><b>Returns</b>
14740 <p><!--para 5 -->
14741 The atomic_signal_fence function returns no value.
14745 <p><!--para 1 -->
14746 The atomic lock-free macros indicate the lock-free property of integer and address atomic
14747 types. A value of 0 indicates that the type is never lock-free; a value of 1 indicates that
14748 the type is sometimes lock-free; a value of 2 indicates that the type is always lock-free.
14749 <p><!--para 2 -->
14750 NOTE Operations that are lock-free should also be address-free. That is, atomic operations on the same
14751 memory location via two different addresses will communicate atomically. The implementation should not
14752 depend on any per-process state. This restriction enables communication via memory mapped into a
14753 process more than once and memory shared between two processes.
14757 <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>
14758 <p><b>Synopsis</b>
14759 <p><!--para 1 -->
14760 <pre>
14762 _Bool atomic_is_lock_free(atomic_type const volatile *obj);
14763 </pre>
14764 <p><b>Description</b>
14765 <p><!--para 2 -->
14766 The atomic_is_lock_free generic function indicates whether or not the object
14767 pointed to by obj is lock-free. atomic_type can be any atomic type.
14768 <p><b>Returns</b>
14769 <p><!--para 3 -->
14770 The atomic_is_lock_free generic function returns nonzero (true) if and only if the
14771 object's operations are lock-free. The result of a lock-free query on one object cannot be
14772 <!--page 297 -->
14773 inferred from the result of a lock-free query on another object.
14777 <p><!--para 1 -->
14778 For each line in the following table, the atomic type name is declared as the
14779 corresponding direct type.
14780 <!--page 298 -->
14781 <pre>
14782 Atomic type name Direct type
14783 atomic_char _Atomic char
14784 atomic_schar _Atomic signed char
14785 atomic_uchar _Atomic unsigned char
14786 atomic_short _Atomic short
14787 atomic_ushort _Atomic unsigned short
14788 atomic_int _Atomic int
14789 atomic_uint _Atomic unsigned int
14790 atomic_long _Atomic long
14791 atomic_ulong _Atomic unsigned long
14792 atomic_llong _Atomic long long
14793 atomic_ullong _Atomic unsigned long long
14794 atomic_char16_t _Atomic char16_t
14795 atomic_char32_t _Atomic char32_t
14796 atomic_wchar_t _Atomic wchar_t
14797 atomic_int_least8_t _Atomic int_least8_t
14798 atomic_uint_least8_t _Atomic uint_least8_t
14799 atomic_int_least16_t _Atomic int_least16_t
14800 atomic_uint_least16_t _Atomic uint_least16_t
14801 atomic_int_least32_t _Atomic int_least32_t
14802 atomic_uint_least32_t _Atomic uint_least32_t
14803 atomic_int_least64_t _Atomic int_least64_t
14804 atomic_uint_least64_t _Atomic uint_least64_t
14805 atomic_int_fast8_t _Atomic int_fast8_t
14806 atomic_uint_fast8_t _Atomic uint_fast8_t
14807 atomic_int_fast16_t _Atomic int_fast16_t
14808 atomic_uint_fast16_t _Atomic uint_fast16_t
14809 atomic_int_fast32_t _Atomic int_fast32_t
14810 atomic_uint_fast32_t _Atomic uint_fast32_t
14811 atomic_int_fast64_t _Atomic int_fast64_t
14812 atomic_uint_fast64_t _Atomic uint_fast64_t
14813 atomic_intptr_t _Atomic intptr_t
14814 atomic_uintptr_t _Atomic uintptr_t
14815 atomic_size_t _Atomic size_t
14816 atomic_ptrdiff_t _Atomic ptrdiff_t
14817 atomic_intmax_t _Atomic intmax_t
14818 atomic_uintmax_t _Atomic uintmax_t
14819 </pre>
14820 <p><!--para 2 -->
14822 <p><!--para 3 -->
14823 The atomic_bool type provides an atomic boolean.
14824 <!--page 299 -->
14825 <p><!--para 4 -->
14826 The atomic_address type provides atomic void * operations. The unit of
14827 addition/subtraction shall be one byte.
14828 <p><!--para 5 -->
14829 NOTE The representation of atomic integer and address types need not have the same size as their
14830 corresponding regular types. They should have the same size whenever possible, as it eases effort required
14831 to port existing code.
14836 <p><!--para 1 -->
14837 There are only a few kinds of operations on atomic types, though there are many
14838 instances of those kinds. This subclause specifies each general kind.
14842 <p><b>Synopsis</b>
14843 <p><!--para 1 -->
14844 <pre>
14846 void atomic_store(volatile A *object, C desired);
14847 void atomic_store_explicit(volatile A *object,
14848 C desired, memory_order order);
14849 </pre>
14850 <p><b>Description</b>
14851 <p><!--para 2 -->
14852 The order argument shall not be memory_order_acquire,
14853 memory_order_consume, nor memory_order_acq_rel. Atomically replace the
14854 value pointed to by object with the value of desired. Memory is affected according
14855 to the value of order.
14856 <p><b>Returns</b>
14857 <p><!--para 3 -->
14858 The atomic_store generic functions return no value.
14862 <p><b>Synopsis</b>
14863 <p><!--para 1 -->
14864 <pre>
14866 C atomic_load(volatile A *object);
14867 C atomic_load_explicit(volatile A *object,
14868 memory_order order);
14869 </pre>
14870 <p><b>Description</b>
14871 <p><!--para 2 -->
14872 The order argument shall not be memory_order_release nor
14873 memory_order_acq_rel. Memory is affected according to the value of order.
14874 <p><b>Returns</b>
14875 Atomically returns the value pointed to by object.
14876 <!--page 300 -->
14879 <h5><a name="7.17.7.3" href="#7.17.7.3">7.17.7.3 The atomic_exchange generic functions</a></h5>
14880 <p><b>Synopsis</b>
14881 <p><!--para 1 -->
14882 <pre>
14884 C atomic_exchange(volatile A *object, C desired);
14885 C atomic_exchange_explicit(volatile A *object,
14886 C desired, memory_order order);
14887 </pre>
14888 <p><b>Description</b>
14889 <p><!--para 2 -->
14890 Atomically replace the value pointed to by object with desired. Memory is affected
14891 according to the value of order. These operations are read-modify-write operations
14893 <p><b>Returns</b>
14894 <p><!--para 3 -->
14895 Atomically returns the value pointed to by object immediately before the effects.
14898 <h5><a name="7.17.7.4" href="#7.17.7.4">7.17.7.4 The atomic_compare_exchange generic functions</a></h5>
14899 <p><b>Synopsis</b>
14900 <p><!--para 1 -->
14901 <pre>
14903 _Bool atomic_compare_exchange_strong(volatile A *object,
14904 C *expected, C desired);
14905 _Bool atomic_compare_exchange_strong_explicit(
14906 volatile A *object, C *expected, C desired,
14907 memory_order success, memory_order failure);
14908 _Bool atomic_compare_exchange_weak(volatile A *object,
14909 C *expected, C desired);
14910 _Bool atomic_compare_exchange_weak_explicit(
14911 volatile A *object, C *expected, C desired,
14912 memory_order success, memory_order failure);
14913 </pre>
14914 <p><b>Description</b>
14915 <p><!--para 2 -->
14916 The failure argument shall not be memory_order_release nor
14917 memory_order_acq_rel. The failure argument shall be no stronger than the
14918 success argument. Atomically, compares the value pointed to by object for equality
14919 with that in expected, and if true, replaces the value pointed to by object with
14920 desired, and if false, updates the value in expected with the value pointed to by
14921 object. Further, if the comparison is true, memory is affected according to the value of
14922 success, and if the comparison is false, memory is affected according to the value of
14923 failure. These operations are atomic read-modify-write operations (<a href="#5.1.2.4">5.1.2.4</a>).
14924 <p><!--para 3 -->
14925 NOTE 1 The effect of the compare-and-exchange operations is
14926 <!--page 301 -->
14927 <pre>
14928 if (*object == *expected)
14929 *object = desired;
14930 else
14931 *expected = *object;
14932 </pre>
14934 <p><!--para 4 -->
14935 The weak compare-and-exchange operations may fail spuriously, that is, return zero
14936 while leaving the value pointed to by expected unchanged.
14937 <p><!--para 5 -->
14938 NOTE 2 This spurious failure enables implementation of compare-and-exchange on a broader class of
14939 machines, e.g. load-locked store-conditional machines.
14941 <p><!--para 6 -->
14942 EXAMPLE A consequence of spurious failure is that nearly all uses of weak compare-and-exchange will
14943 be in a loop.
14944 <pre>
14945 exp = atomic_load(&cur);
14946 do {
14947 des = function(exp);
14948 } while (!atomic_compare_exchange_weak(&cur, &exp, des));
14949 </pre>
14950 When a compare-and-exchange is in a loop, the weak version will yield better performance on some
14951 platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the
14952 strong one is preferable.
14954 <p><b>Returns</b>
14955 <p><!--para 7 -->
14956 The result of the comparison.
14959 <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>
14960 <p><!--para 1 -->
14961 The following operations perform arithmetic and bitwise computations. All of these
14962 operations are applicable to an object of any atomic integer type. Only addition and
14963 subtraction are applicable to atomic_address. None of these operations is applicable
14964 to atomic_bool. The key, operator, and computation correspondence is:
14965 key op computation
14966 add + addition
14967 sub - subtraction
14968 or | bitwise inclusive or
14969 xor ^ bitwise exclusive or
14970 and & bitwise and
14971 <p><b>Synopsis</b>
14972 <p><!--para 2 -->
14973 <pre>
14975 C atomic_fetch_key(volatile A *object, M operand);
14976 C atomic_fetch_key_explicit(volatile A *object,
14977 M operand, memory_order order);
14978 </pre>
14979 <p><b>Description</b>
14980 <p><!--para 3 -->
14981 Atomically replaces the value pointed to by object with the result of the computation
14982 applied to the value pointed to by object and the given operand. Memory is affected
14983 according to the value of order. These operations are atomic read-modify-write
14984 <!--page 302 -->
14985 operations (<a href="#5.1.2.4">5.1.2.4</a>). For signed integer types, arithmetic is defined to use two's
14986 complement representation with silent wrap-around on overflow; there are no undefined
14987 results. For address types, the result may be an undefined address, but the operations
14988 otherwise have no undefined behavior.
14989 <p><b>Returns</b>
14990 <p><!--para 4 -->
14991 Atomically, the value pointed to by object immediately before the effects.
14992 <p><!--para 5 -->
14993 NOTE The operation of the atomic_fetch and modify generic functions are nearly equivalent to the
14994 operation of the corresponding op= compound assignment operators. The only differences are that the
14995 compound assignment operators are not guaranteed to operate atomically, and the value yielded by a
14996 compound assignment operator is the updated value of the object, whereas the value returned by the
14997 atomic_fetch and modify generic functions is the previous value of the atomic object.
15002 <p><!--para 1 -->
15003 The atomic_flag type provides the classic test-and-set functionality. It has two
15004 states, set and clear.
15005 <p><!--para 2 -->
15006 Operations on an object of type atomic_flag shall be lock free.
15007 <p><!--para 3 -->
15008 NOTE Hence the operations should also be address-free. No other type requires lock-free operations, so
15009 the atomic_flag type is the minimum hardware-implemented type needed to conform to this
15010 International standard. The remaining types can be emulated with atomic_flag, though with less than
15011 ideal properties.
15013 <p><!--para 4 -->
15014 The macro ATOMIC_FLAG_INIT may be used to initialize an atomic_flag to the
15015 clear state. An atomic_flag that is not explicitly initialized with
15016 ATOMIC_FLAG_INIT is initially in an indeterminate state.
15017 <p><!--para 5 -->
15018 EXAMPLE
15019 <pre>
15020 atomic_flag guard = ATOMIC_FLAG_INIT;
15021 </pre>
15025 <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>
15026 <p><b>Synopsis</b>
15027 <p><!--para 1 -->
15028 <pre>
15030 bool atomic_flag_test_and_set(
15031 volatile atomic_flag *object);
15032 bool atomic_flag_test_and_set_explicit(
15033 volatile atomic_flag *object, memory_order order);
15034 </pre>
15035 <p><b>Description</b>
15036 <p><!--para 2 -->
15037 Atomically sets the value pointed to by object to true. Memory is affected according
15038 to the value of order. These operations are atomic read-modify-write operations
15040 <!--page 303 -->
15041 <p><b>Returns</b>
15042 <p><!--para 3 -->
15043 Atomically, the value of the object immediately before the effects.
15047 <p><b>Synopsis</b>
15048 <p><!--para 1 -->
15049 <pre>
15051 void atomic_flag_clear(volatile atomic_flag *object);
15052 void atomic_flag_clear_explicit(
15053 volatile atomic_flag *object, memory_order order);
15054 </pre>
15055 <p><b>Description</b>
15056 <p><!--para 2 -->
15057 The order argument shall not be memory_order_acquire nor
15058 memory_order_acq_rel. Atomically sets the value pointed to by object to false.
15059 Memory is affected according to the value of order.
15060 <p><b>Returns</b>
15061 <p><!--para 3 -->
15062 The atomic_flag_clear functions return no value.
15063 <!--page 304 -->
15067 <p><!--para 1 -->
15069 <p><!--para 2 -->
15070 The macro
15071 <pre>
15072 bool
15073 </pre>
15074 expands to _Bool.
15075 <p><!--para 3 -->
15076 The remaining three macros are suitable for use in #if preprocessing directives. They
15077 are
15078 <pre>
15079 true
15080 </pre>
15081 which expands to the integer constant 1,
15082 <pre>
15083 false
15084 </pre>
15085 which expands to the integer constant 0, and
15086 <pre>
15087 __bool_true_false_are_defined
15088 </pre>
15089 which expands to the integer constant 1.
15090 <p><!--para 4 -->
15091 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
15097 <!--page 305 -->
15099 <p><b>Footnotes</b>
15100 <p><small><a name="note252" href="#note252">252)</a> See ''future library directions'' (<a href="#7.30.7">7.30.7</a>).
15101 </small>
15105 <p><!--para 1 -->
15106 The header <a href="#7.19"><stddef.h></a> defines the following macros and declares the following types.
15107 Some are also defined in other headers, as noted in their respective subclauses.
15108 <p><!--para 2 -->
15109 The types are
15110 <pre>
15111 ptrdiff_t
15112 </pre>
15113 which is the signed integer type of the result of subtracting two pointers;
15114 <pre>
15115 size_t
15116 </pre>
15117 which is the unsigned integer type of the result of the sizeof operator;
15118 <pre>
15119 max_align_t
15120 </pre>
15121 which is an object type whose alignment is as great as is supported by the implementation
15122 in all contexts; and
15123 <pre>
15124 wchar_t
15125 </pre>
15126 which is an integer type whose range of values can represent distinct codes for all
15127 members of the largest extended character set specified among the supported locales; the
15128 null character shall have the code value zero. Each member of the basic character set
15129 shall have a code value equal to its value when used as the lone character in an integer
15130 character constant if an implementation does not define
15131 __STDC_MB_MIGHT_NEQ_WC__.
15132 <p><!--para 3 -->
15133 The macros are
15134 <pre>
15135 NULL
15136 </pre>
15137 which expands to an implementation-defined null pointer constant; and
15138 <pre>
15139 offsetof(type, member-designator)
15140 </pre>
15141 which expands to an integer constant expression that has type size_t, the value of
15142 which is the offset in bytes, to the structure member (designated by member-designator),
15143 from the beginning of its structure (designated by type). The type and member designator
15144 shall be such that given
15145 <pre>
15146 static type t;
15147 </pre>
15148 then the expression &(t.member-designator) evaluates to an address constant. (If the
15149 specified member is a bit-field, the behavior is undefined.)
15150 <p><b>Recommended practice</b>
15151 <p><!--para 4 -->
15152 The types used for size_t and ptrdiff_t should not have an integer conversion rank
15153 greater than that of signed long int unless the implementation supports objects
15154 large enough to make this necessary.
15155 <!--page 306 -->
15157 <!--page 307 -->
15161 <p><!--para 1 -->
15162 The header <a href="#7.20"><stdint.h></a> declares sets of integer types having specified widths, and
15163 defines corresponding sets of macros.<sup><a href="#note253"><b>253)</b></a></sup> It also defines macros that specify limits of
15164 integer types corresponding to types defined in other standard headers.
15165 <p><!--para 2 -->
15166 Types are defined in the following categories:
15167 <ul>
15168 <li> integer types having certain exact widths;
15169 <li> integer types having at least certain specified widths;
15170 <li> fastest integer types having at least certain specified widths;
15171 <li> integer types wide enough to hold pointers to objects;
15172 <li> integer types having greatest width.
15173 </ul>
15174 (Some of these types may denote the same type.)
15175 <p><!--para 3 -->
15176 Corresponding macros specify limits of the declared types and construct suitable
15177 constants.
15178 <p><!--para 4 -->
15179 For each type described herein that the implementation provides,<sup><a href="#note254"><b>254)</b></a></sup> <a href="#7.20"><stdint.h></a> shall
15180 declare that typedef name and define the associated macros. Conversely, for each type
15181 described herein that the implementation does not provide, <a href="#7.20"><stdint.h></a> shall not
15182 declare that typedef name nor shall it define the associated macros. An implementation
15183 shall provide those types described as ''required'', but need not provide any of the others
15184 (described as ''optional'').
15186 <p><b>Footnotes</b>
15187 <p><small><a name="note253" href="#note253">253)</a> See ''future library directions'' (<a href="#7.30.8">7.30.8</a>).
15188 </small>
15189 <p><small><a name="note254" href="#note254">254)</a> Some of these types may denote implementation-defined extended integer types.
15190 </small>
15194 <p><!--para 1 -->
15195 When typedef names differing only in the absence or presence of the initial u are defined,
15196 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
15197 implementation providing one of these corresponding types shall also provide the other.
15198 <p><!--para 2 -->
15199 In the following descriptions, the symbol N represents an unsigned decimal integer with
15200 no leading zeros (e.g., 8 or 24, but not 04 or 048).
15205 <!--page 308 -->
15209 <p><!--para 1 -->
15210 The typedef name intN_t designates a signed integer type with width N , no padding
15211 bits, and a two's complement representation. Thus, int8_t denotes such a signed
15212 integer type with a width of exactly 8 bits.
15213 <p><!--para 2 -->
15214 The typedef name uintN_t designates an unsigned integer type with width N and no
15215 padding bits. Thus, uint24_t denotes such an unsigned integer type with a width of
15216 exactly 24 bits.
15217 <p><!--para 3 -->
15218 These types are optional. However, if an implementation provides integer types with
15219 widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
15220 two's complement representation, it shall define the corresponding typedef names.
15224 <p><!--para 1 -->
15225 The typedef name int_leastN_t designates a signed integer type with a width of at
15226 least N , such that no signed integer type with lesser size has at least the specified width.
15227 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
15228 <p><!--para 2 -->
15229 The typedef name uint_leastN_t designates an unsigned integer type with a width
15230 of at least N , such that no unsigned integer type with lesser size has at least the specified
15231 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
15232 least 16 bits.
15233 <p><!--para 3 -->
15234 The following types are required:
15235 <pre>
15236 int_least8_t uint_least8_t
15237 int_least16_t uint_least16_t
15238 int_least32_t uint_least32_t
15239 int_least64_t uint_least64_t
15240 </pre>
15241 All other types of this form are optional.
15245 <p><!--para 1 -->
15246 Each of the following types designates an integer type that is usually fastest<sup><a href="#note255"><b>255)</b></a></sup> to operate
15247 with among all integer types that have at least the specified width.
15248 <p><!--para 2 -->
15249 The typedef name int_fastN_t designates the fastest signed integer type with a width
15250 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
15251 type with a width of at least N .
15256 <!--page 309 -->
15257 <p><!--para 3 -->
15258 The following types are required:
15259 <pre>
15260 int_fast8_t uint_fast8_t
15261 int_fast16_t uint_fast16_t
15262 int_fast32_t uint_fast32_t
15263 int_fast64_t uint_fast64_t
15264 </pre>
15265 All other types of this form are optional.
15267 <p><b>Footnotes</b>
15268 <p><small><a name="note255" href="#note255">255)</a> The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
15269 grounds for choosing one type over another, it will simply pick some integer type satisfying the
15270 signedness and width requirements.
15271 </small>
15274 <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>
15275 <p><!--para 1 -->
15276 The following type designates a signed integer type with the property that any valid
15277 pointer to void can be converted to this type, then converted back to pointer to void,
15278 and the result will compare equal to the original pointer:
15279 <pre>
15280 intptr_t
15281 </pre>
15282 The following type designates an unsigned integer type with the property that any valid
15283 pointer to void can be converted to this type, then converted back to pointer to void,
15284 and the result will compare equal to the original pointer:
15285 <pre>
15286 uintptr_t
15287 </pre>
15288 These types are optional.
15292 <p><!--para 1 -->
15293 The following type designates a signed integer type capable of representing any value of
15294 any signed integer type:
15295 <pre>
15296 intmax_t
15297 </pre>
15298 The following type designates an unsigned integer type capable of representing any value
15299 of any unsigned integer type:
15300 <pre>
15301 uintmax_t
15302 </pre>
15303 These types are required.
15307 <p><!--para 1 -->
15308 The following object-like macros specify the minimum and maximum limits of the types *
15309 declared in <a href="#7.20"><stdint.h></a>. Each macro name corresponds to a similar type name in
15311 <p><!--para 2 -->
15312 Each instance of any defined macro shall be replaced by a constant expression suitable
15313 for use in #if preprocessing directives, and this expression shall have the same type as
15314 would an expression that is an object of the corresponding type converted according to
15315 the integer promotions. Its implementation-defined value shall be equal to or greater in
15316 magnitude (absolute value) than the corresponding value given below, with the same sign,
15317 except where stated to be exactly the given value.
15318 <!--page 310 -->
15322 <p><!--para 1 -->
15323 <ul>
15324 <li> minimum values of exact-width signed integer types
15325 <pre>
15326 INTN_MIN exactly -(2 N -1 )
15327 </pre>
15328 <li> maximum values of exact-width signed integer types
15329 <pre>
15330 INTN_MAX exactly 2 N -1 - 1
15331 </pre>
15332 <li> maximum values of exact-width unsigned integer types
15333 UINTN_MAX exactly 2 N - 1
15334 </ul>
15337 <h5><a name="7.20.2.2" href="#7.20.2.2">7.20.2.2 Limits of minimum-width integer types</a></h5>
15338 <p><!--para 1 -->
15339 <ul>
15340 <li> minimum values of minimum-width signed integer types
15341 <pre>
15342 INT_LEASTN_MIN -(2 N -1 - 1)
15343 </pre>
15344 <li> maximum values of minimum-width signed integer types
15345 <pre>
15346 INT_LEASTN_MAX 2 N -1 - 1
15347 </pre>
15348 <li> maximum values of minimum-width unsigned integer types
15349 UINT_LEASTN_MAX 2N - 1
15350 </ul>
15353 <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>
15354 <p><!--para 1 -->
15355 <ul>
15356 <li> minimum values of fastest minimum-width signed integer types
15357 <pre>
15358 INT_FASTN_MIN -(2 N -1 - 1)
15359 </pre>
15360 <li> maximum values of fastest minimum-width signed integer types
15361 INT_FASTN_MAX 2 N -1 - 1
15362 <li> maximum values of fastest minimum-width unsigned integer types
15363 UINT_FASTN_MAX 2N - 1
15364 </ul>
15367 <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>
15368 <p><!--para 1 -->
15369 <ul>
15370 <li> minimum value of pointer-holding signed integer type
15371 <pre>
15372 INTPTR_MIN -(215 - 1)
15373 </pre>
15374 <li> maximum value of pointer-holding signed integer type
15375 INTPTR_MAX 215 - 1
15376 <li> maximum value of pointer-holding unsigned integer type
15377 UINTPTR_MAX 216 - 1
15378 <!--page 311 -->
15379 </ul>
15382 <h5><a name="7.20.2.5" href="#7.20.2.5">7.20.2.5 Limits of greatest-width integer types</a></h5>
15383 <p><!--para 1 -->
15384 <ul>
15385 <li> minimum value of greatest-width signed integer type
15386 INTMAX_MIN -(263 - 1)
15387 <li> maximum value of greatest-width signed integer type
15388 INTMAX_MAX 263 - 1
15389 <li> maximum value of greatest-width unsigned integer type
15390 UINTMAX_MAX 264 - 1
15391 </ul>
15395 <p><!--para 1 -->
15396 The following object-like macros specify the minimum and maximum limits of integer *
15397 types corresponding to types defined in other standard headers.
15398 <p><!--para 2 -->
15399 Each instance of these macros shall be replaced by a constant expression suitable for use
15400 in #if preprocessing directives, and this expression shall have the same type as would an
15401 expression that is an object of the corresponding type converted according to the integer
15402 promotions. Its implementation-defined value shall be equal to or greater in magnitude
15403 (absolute value) than the corresponding value given below, with the same sign. An
15404 implementation shall define only the macros corresponding to those typedef names it
15406 <ul>
15407 <li> limits of ptrdiff_t
15408 PTRDIFF_MIN -65535
15409 PTRDIFF_MAX +65535
15410 <li> limits of sig_atomic_t
15411 SIG_ATOMIC_MIN see below
15412 SIG_ATOMIC_MAX see below
15413 <li> limit of size_t
15414 SIZE_MAX 65535
15415 <li> limits of wchar_t
15416 WCHAR_MIN see below
15417 WCHAR_MAX see below
15418 <li> limits of wint_t
15423 <!--page 312 -->
15424 WINT_MIN see below
15425 WINT_MAX see below
15426 </ul>
15427 <p><!--para 3 -->
15428 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
15429 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
15430 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
15431 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
15432 SIG_ATOMIC_MAX shall be no less than 255.
15433 <p><!--para 4 -->
15434 If wchar_t (see <a href="#7.19">7.19</a>) is defined as a signed integer type, the value of WCHAR_MIN
15435 shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
15436 otherwise, wchar_t is defined as an unsigned integer type, and the value of
15437 WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.<sup><a href="#note257"><b>257)</b></a></sup>
15438 <p><!--para 5 -->
15439 If wint_t (see <a href="#7.28">7.28</a>) is defined as a signed integer type, the value of WINT_MIN shall
15440 be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
15441 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
15442 shall be 0 and the value of WINT_MAX shall be no less than 65535.
15444 <p><b>Footnotes</b>
15445 <p><small><a name="note256" href="#note256">256)</a> A freestanding implementation need not provide all of these types.
15446 </small>
15447 <p><small><a name="note257" href="#note257">257)</a> The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
15448 character set.
15449 </small>
15453 <p><!--para 1 -->
15454 The following function-like macros expand to integer constants suitable for initializing *
15455 objects that have integer types corresponding to types defined in <a href="#7.20"><stdint.h></a>. Each
15456 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>.
15457 <p><!--para 2 -->
15458 The argument in any instance of these macros shall be an unsuffixed integer constant (as
15459 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.
15460 <p><!--para 3 -->
15461 Each invocation of one of these macros shall expand to an integer constant expression
15462 suitable for use in #if preprocessing directives. The type of the expression shall have
15463 the same type as would an expression of the corresponding type converted according to
15464 the integer promotions. The value of the expression shall be that of the argument.
15467 <h5><a name="7.20.4.1" href="#7.20.4.1">7.20.4.1 Macros for minimum-width integer constants</a></h5>
15468 <p><!--para 1 -->
15469 The macro INTN_C(value) shall expand to an integer constant expression
15470 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
15471 to an integer constant expression corresponding to the type uint_leastN_t. For
15472 example, if uint_least64_t is a name for the type unsigned long long int,
15473 then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
15478 <!--page 313 -->
15481 <h5><a name="7.20.4.2" href="#7.20.4.2">7.20.4.2 Macros for greatest-width integer constants</a></h5>
15482 <p><!--para 1 -->
15483 The following macro expands to an integer constant expression having the value specified
15484 by its argument and the type intmax_t:
15485 <pre>
15486 INTMAX_C(value)
15487 </pre>
15488 The following macro expands to an integer constant expression having the value specified
15489 by its argument and the type uintmax_t:
15490 <!--page 314 -->
15491 <pre>
15492 UINTMAX_C(value)
15493 </pre>
15500 <p><!--para 1 -->
15501 The header <a href="#7.21"><stdio.h></a> defines several macros, and declares three types and many
15502 functions for performing input and output.
15503 <p><!--para 2 -->
15505 <pre>
15506 FILE
15507 </pre>
15508 which is an object type capable of recording all the information needed to control a
15509 stream, including its file position indicator, a pointer to its associated buffer (if any), an
15510 error indicator that records whether a read/write error has occurred, and an end-of-file
15511 indicator that records whether the end of the file has been reached; and
15512 <pre>
15513 fpos_t
15514 </pre>
15515 which is a complete object type other than an array type capable of recording all the
15516 information needed to specify uniquely every position within a file.
15517 <p><!--para 3 -->
15519 <pre>
15520 _IOFBF
15521 _IOLBF
15522 _IONBF
15523 </pre>
15524 which expand to integer constant expressions with distinct values, suitable for use as the
15525 third argument to the setvbuf function;
15526 <pre>
15527 BUFSIZ
15528 </pre>
15529 which expands to an integer constant expression that is the size of the buffer used by the
15530 setbuf function;
15531 <pre>
15532 EOF
15533 </pre>
15534 which expands to an integer constant expression, with type int and a negative value, that
15535 is returned by several functions to indicate end-of-file, that is, no more input from a
15536 stream;
15537 <pre>
15538 FOPEN_MAX
15539 </pre>
15540 which expands to an integer constant expression that is the minimum number of files that
15541 the implementation guarantees can be open simultaneously;
15542 <pre>
15543 FILENAME_MAX
15544 </pre>
15545 which expands to an integer constant expression that is the size needed for an array of
15546 char large enough to hold the longest file name string that the implementation
15547 <!--page 315 -->
15549 <pre>
15550 L_tmpnam
15551 </pre>
15552 which expands to an integer constant expression that is the size needed for an array of
15553 char large enough to hold a temporary file name string generated by the tmpnam
15554 function;
15555 <pre>
15556 SEEK_CUR
15557 SEEK_END
15558 SEEK_SET
15559 </pre>
15560 which expand to integer constant expressions with distinct values, suitable for use as the
15561 third argument to the fseek function;
15562 <pre>
15563 TMP_MAX
15564 </pre>
15565 which expands to an integer constant expression that is the minimum number of unique
15566 file names that can be generated by the tmpnam function;
15567 <pre>
15568 stderr
15569 stdin
15570 stdout
15571 </pre>
15572 which are expressions of type ''pointer to FILE'' that point to the FILE objects
15573 associated, respectively, with the standard error, input, and output streams.
15574 <p><!--para 4 -->
15575 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide character input
15576 and output. The wide character input/output functions described in that subclause
15577 provide operations analogous to most of those described here, except that the
15578 fundamental units internal to the program are wide characters. The external
15579 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
15581 <p><!--para 5 -->
15582 The input/output functions are given the following collective terms:
15583 <ul>
15584 <li> The wide character input functions -- those functions described in <a href="#7.28">7.28</a> that perform
15585 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
15586 fwscanf, wscanf, vfwscanf, and vwscanf.
15587 <li> The wide character output functions -- those functions described in <a href="#7.28">7.28</a> that perform
15588 output from wide characters and wide strings: fputwc, fputws, putwc,
15589 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
15592 <!--page 316 -->
15593 <li> The wide character input/output functions -- the union of the ungetwc function, the
15594 wide character input functions, and the wide character output functions.
15595 <li> The byte input/output functions -- those functions described in this subclause that
15596 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
15597 fscanf, fwrite, getc, getchar, printf, putc, putchar, puts, scanf, *
15598 ungetc, vfprintf, vfscanf, vprintf, and vscanf.
15599 </ul>
15600 <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
15601 tmpnam function (<a href="#7.21.4.4">7.21.4.4</a>), <a href="#7.28"><wchar.h></a> (<a href="#7.28">7.28</a>).
15603 <p><b>Footnotes</b>
15604 <p><small><a name="note258" href="#note258">258)</a> If the implementation imposes no practical limit on the length of file name strings, the value of
15605 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
15606 string. Of course, file name string contents are subject to other system-specific constraints; therefore
15607 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
15608 </small>
15612 <p><!--para 1 -->
15613 Input and output, whether to or from physical devices such as terminals and tape drives,
15614 or whether to or from files supported on structured storage devices, are mapped into
15615 logical data streams, whose properties are more uniform than their various inputs and
15616 outputs. Two forms of mapping are supported, for text streams and for binary
15618 <p><!--para 2 -->
15619 A text stream is an ordered sequence of characters composed into lines, each line
15620 consisting of zero or more characters plus a terminating new-line character. Whether the
15621 last line requires a terminating new-line character is implementation-defined. Characters
15622 may have to be added, altered, or deleted on input and output to conform to differing
15623 conventions for representing text in the host environment. Thus, there need not be a one-
15624 to-one correspondence between the characters in a stream and those in the external
15625 representation. Data read in from a text stream will necessarily compare equal to the data
15626 that were earlier written out to that stream only if: the data consist only of printing
15627 characters and the control characters horizontal tab and new-line; no new-line character is
15628 immediately preceded by space characters; and the last character is a new-line character.
15629 Whether space characters that are written out immediately before a new-line character
15630 appear when read in is implementation-defined.
15631 <p><!--para 3 -->
15632 A binary stream is an ordered sequence of characters that can transparently record
15633 internal data. Data read in from a binary stream shall compare equal to the data that were
15634 earlier written out to that stream, under the same implementation. Such a stream may,
15635 however, have an implementation-defined number of null characters appended to the end
15636 of the stream.
15637 <p><!--para 4 -->
15638 Each stream has an orientation. After a stream is associated with an external file, but
15639 before any operations are performed on it, the stream is without orientation. Once a wide
15640 character input/output function has been applied to a stream without orientation, the
15643 <!--page 317 -->
15644 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
15645 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
15646 Only a call to the freopen function or the fwide function can otherwise alter the
15647 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note260"><b>260)</b></a></sup>
15648 <p><!--para 5 -->
15649 Byte input/output functions shall not be applied to a wide-oriented stream and wide
15650 character input/output functions shall not be applied to a byte-oriented stream. The
15651 remaining stream operations do not affect, and are not affected by, a stream's orientation,
15652 except for the following additional restrictions:
15653 <ul>
15654 <li> Binary wide-oriented streams have the file-positioning restrictions ascribed to both
15655 text and binary streams.
15656 <li> For wide-oriented streams, after a successful call to a file-positioning function that
15657 leaves the file position indicator prior to the end-of-file, a wide character output
15658 function can overwrite a partial multibyte character; any file contents beyond the
15659 byte(s) written are henceforth indeterminate.
15660 </ul>
15661 <p><!--para 6 -->
15662 Each wide-oriented stream has an associated mbstate_t object that stores the current
15663 parse state of the stream. A successful call to fgetpos stores a representation of the
15664 value of this mbstate_t object as part of the value of the fpos_t object. A later
15665 successful call to fsetpos using the same stored fpos_t value restores the value of
15666 the associated mbstate_t object as well as the position within the controlled stream.
15667 <p><b>Environmental limits</b>
15668 <p><!--para 7 -->
15669 An implementation shall support text files with lines containing at least 254 characters,
15670 including the terminating new-line character. The value of the macro BUFSIZ shall be at
15671 least 256.
15672 <p><b> Forward references</b>: the freopen function (<a href="#7.21.5.4">7.21.5.4</a>), the fwide function (<a href="#7.28.3.5">7.28.3.5</a>),
15673 mbstate_t (<a href="#7.29.1">7.29.1</a>), the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>), the fsetpos function
15679 <!--page 318 -->
15681 <p><b>Footnotes</b>
15682 <p><small><a name="note259" href="#note259">259)</a> An implementation need not distinguish between text streams and binary streams. In such an
15683 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
15684 line.
15685 </small>
15686 <p><small><a name="note260" href="#note260">260)</a> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
15687 </small>
15691 <p><!--para 1 -->
15692 A stream is associated with an external file (which may be a physical device) by opening
15693 a file, which may involve creating a new file. Creating an existing file causes its former
15694 contents to be discarded, if necessary. If a file can support positioning requests (such as a
15695 disk file, as opposed to a terminal), then a file position indicator associated with the
15696 stream is positioned at the start (character number zero) of the file, unless the file is
15697 opened with append mode in which case it is implementation-defined whether the file
15698 position indicator is initially positioned at the beginning or the end of the file. The file
15699 position indicator is maintained by subsequent reads, writes, and positioning requests, to
15700 facilitate an orderly progression through the file.
15701 <p><!--para 2 -->
15702 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
15703 stream causes the associated file to be truncated beyond that point is implementation-
15704 defined.
15705 <p><!--para 3 -->
15706 When a stream is unbuffered, characters are intended to appear from the source or at the
15707 destination as soon as possible. Otherwise characters may be accumulated and
15708 transmitted to or from the host environment as a block. When a stream is fully buffered,
15709 characters are intended to be transmitted to or from the host environment as a block when
15710 a buffer is filled. When a stream is line buffered, characters are intended to be
15711 transmitted to or from the host environment as a block when a new-line character is
15712 encountered. Furthermore, characters are intended to be transmitted as a block to the host
15713 environment when a buffer is filled, when input is requested on an unbuffered stream, or
15714 when input is requested on a line buffered stream that requires the transmission of
15715 characters from the host environment. Support for these characteristics is
15716 implementation-defined, and may be affected via the setbuf and setvbuf functions.
15717 <p><!--para 4 -->
15718 A file may be disassociated from a controlling stream by closing the file. Output streams
15719 are flushed (any unwritten buffer contents are transmitted to the host environment) before
15720 the stream is disassociated from the file. The value of a pointer to a FILE object is
15721 indeterminate after the associated file is closed (including the standard text streams).
15722 Whether a file of zero length (on which no characters have been written by an output
15723 stream) actually exists is implementation-defined.
15724 <p><!--para 5 -->
15725 The file may be subsequently reopened, by the same or another program execution, and
15726 its contents reclaimed or modified (if it can be repositioned at its start). If the main
15727 function returns to its original caller, or if the exit function is called, all open files are
15728 closed (hence all output streams are flushed) before program termination. Other paths to
15729 program termination, such as calling the abort function, need not close all files
15730 properly.
15731 <p><!--para 6 -->
15732 The address of the FILE object used to control a stream may be significant; a copy of a
15733 FILE object need not serve in place of the original.
15734 <!--page 319 -->
15735 <p><!--para 7 -->
15736 At program startup, three text streams are predefined and need not be opened explicitly
15737 <ul>
15738 <li> standard input (for reading conventional input), standard output (for writing
15739 </ul>
15740 conventional output), and standard error (for writing diagnostic output). As initially
15741 opened, the standard error stream is not fully buffered; the standard input and standard
15742 output streams are fully buffered if and only if the stream can be determined not to refer
15743 to an interactive device.
15744 <p><!--para 8 -->
15745 Functions that open additional (nontemporary) files require a file name, which is a string.
15746 The rules for composing valid file names are implementation-defined. Whether the same
15747 file can be simultaneously open multiple times is also implementation-defined.
15748 <p><!--para 9 -->
15749 Although both text and binary wide-oriented streams are conceptually sequences of wide
15750 characters, the external file associated with a wide-oriented stream is a sequence of
15751 multibyte characters, generalized as follows:
15752 <ul>
15753 <li> Multibyte encodings within files may contain embedded null bytes (unlike multibyte
15754 encodings valid for use internal to the program).
15755 <li> A file need not begin nor end in the initial shift state.<sup><a href="#note261"><b>261)</b></a></sup>
15756 </ul>
15757 <p><!--para 10 -->
15758 Moreover, the encodings used for multibyte characters may differ among files. Both the
15759 nature and choice of such encodings are implementation-defined.
15760 <p><!--para 11 -->
15761 The wide character input functions read multibyte characters from the stream and convert
15762 them to wide characters as if they were read by successive calls to the fgetwc function.
15763 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
15764 described by the stream's own mbstate_t object. The byte input functions read
15765 characters from the stream as if by successive calls to the fgetc function.
15766 <p><!--para 12 -->
15767 The wide character output functions convert wide characters to multibyte characters and
15768 write them to the stream as if they were written by successive calls to the fputwc
15769 function. Each conversion occurs as if by a call to the wcrtomb function, with the
15770 conversion state described by the stream's own mbstate_t object. The byte output
15771 functions write characters to the stream as if by successive calls to the fputc function.
15772 <p><!--para 13 -->
15773 In some cases, some of the byte input/output functions also perform conversions between
15774 multibyte characters and wide characters. These conversions also occur as if by calls to
15775 the mbrtowc and wcrtomb functions.
15776 <p><!--para 14 -->
15777 An encoding error occurs if the character sequence presented to the underlying
15778 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
15779 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
15782 <!--page 320 -->
15783 multibyte character. The wide character input/output functions and the byte input/output
15784 functions store the value of the macro EILSEQ in errno if and only if an encoding error
15785 occurs.
15786 <p><b>Environmental limits</b>
15787 <p><!--para 15 -->
15788 The value of FOPEN_MAX shall be at least eight, including the three standard text
15789 streams.
15790 <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
15791 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
15792 (<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="#7.28.3.1">7.28.3.1</a>), the
15793 fputwc function (<a href="#7.28.3.3">7.28.3.3</a>), conversion state (<a href="#7.28.6">7.28.6</a>), the mbrtowc function
15794 (<a href="#7.28.6.3.2">7.28.6.3.2</a>), the wcrtomb function (<a href="#7.28.6.3.3">7.28.6.3.3</a>).
15796 <p><b>Footnotes</b>
15797 <p><small><a name="note261" href="#note261">261)</a> Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
15798 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
15799 with state-dependent encoding that does not assuredly end in the initial shift state.
15800 </small>
15807 <p><b>Synopsis</b>
15808 <p><!--para 1 -->
15809 <pre>
15811 int remove(const char *filename);
15812 </pre>
15813 <p><b>Description</b>
15814 <p><!--para 2 -->
15815 The remove function causes the file whose name is the string pointed to by filename
15816 to be no longer accessible by that name. A subsequent attempt to open that file using that
15817 name will fail, unless it is created anew. If the file is open, the behavior of the remove
15818 function is implementation-defined.
15819 <p><b>Returns</b>
15820 <p><!--para 3 -->
15821 The remove function returns zero if the operation succeeds, nonzero if it fails.
15825 <p><b>Synopsis</b>
15826 <p><!--para 1 -->
15827 <pre>
15829 int rename(const char *old, const char *new);
15830 </pre>
15831 <p><b>Description</b>
15832 <p><!--para 2 -->
15833 The rename function causes the file whose name is the string pointed to by old to be
15834 henceforth known by the name given by the string pointed to by new. The file named
15835 old is no longer accessible by that name. If a file named by the string pointed to by new
15836 exists prior to the call to the rename function, the behavior is implementation-defined.
15837 <!--page 321 -->
15838 <p><b>Returns</b>
15839 <p><!--para 3 -->
15840 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note262"><b>262)</b></a></sup> in
15841 which case if the file existed previously it is still known by its original name.
15843 <p><b>Footnotes</b>
15844 <p><small><a name="note262" href="#note262">262)</a> Among the reasons the implementation may cause the rename function to fail are that the file is open
15845 or that it is necessary to copy its contents to effectuate its renaming.
15846 </small>
15850 <p><b>Synopsis</b>
15851 <p><!--para 1 -->
15852 <pre>
15854 FILE *tmpfile(void);
15855 </pre>
15856 <p><b>Description</b>
15857 <p><!--para 2 -->
15858 The tmpfile function creates a temporary binary file that is different from any other
15859 existing file and that will automatically be removed when it is closed or at program
15860 termination. If the program terminates abnormally, whether an open temporary file is
15862 <p><b>Recommended practice</b>
15863 <p><!--para 3 -->
15864 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
15865 program (this limit may be shared with tmpnam) and there should be no limit on the
15866 number simultaneously open other than this limit and any limit on the number of open
15867 files (FOPEN_MAX).
15868 <p><b>Returns</b>
15869 <p><!--para 4 -->
15870 The tmpfile function returns a pointer to the stream of the file that it created. If the file
15871 cannot be created, the tmpfile function returns a null pointer.
15876 <p><b>Synopsis</b>
15877 <p><!--para 1 -->
15878 <pre>
15880 char *tmpnam(char *s);
15881 </pre>
15882 <p><b>Description</b>
15883 <p><!--para 2 -->
15884 The tmpnam function generates a string that is a valid file name and that is not the same
15885 as the name of an existing file.<sup><a href="#note263"><b>263)</b></a></sup> The function is potentially capable of generating at
15888 <!--page 322 -->
15889 least TMP_MAX different strings, but any or all of them may already be in use by existing
15890 files and thus not be suitable return values.
15891 <p><!--para 3 -->
15892 The tmpnam function generates a different string each time it is called.
15893 <p><!--para 4 -->
15894 Calls to the tmpnam function with a null pointer argument may introduce data races with
15895 each other. The implementation shall behave as if no library function calls the tmpnam
15896 function.
15897 <p><b>Returns</b>
15898 <p><!--para 5 -->
15899 If no suitable string can be generated, the tmpnam function returns a null pointer.
15900 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
15901 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
15902 function may modify the same object). If the argument is not a null pointer, it is assumed
15903 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
15904 in that array and returns the argument as its value.
15905 <p><b>Environmental limits</b>
15906 <p><!--para 6 -->
15907 The value of the macro TMP_MAX shall be at least 25.
15909 <p><b>Footnotes</b>
15910 <p><small><a name="note263" href="#note263">263)</a> Files created using strings generated by the tmpnam function are temporary only in the sense that
15911 their names should not collide with those generated by conventional naming rules for the
15912 implementation. It is still necessary to use the remove function to remove such files when their use
15913 is ended, and before program termination.
15914 </small>
15921 <p><b>Synopsis</b>
15922 <p><!--para 1 -->
15923 <pre>
15925 int fclose(FILE *stream);
15926 </pre>
15927 <p><b>Description</b>
15928 <p><!--para 2 -->
15929 A successful call to the fclose function causes the stream pointed to by stream to be
15930 flushed and the associated file to be closed. Any unwritten buffered data for the stream
15931 are delivered to the host environment to be written to the file; any unread buffered data
15932 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
15933 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
15934 (and deallocated if it was automatically allocated).
15935 <p><b>Returns</b>
15936 <p><!--para 3 -->
15937 The fclose function returns zero if the stream was successfully closed, or EOF if any
15938 errors were detected.
15939 <!--page 323 -->
15943 <p><b>Synopsis</b>
15944 <p><!--para 1 -->
15945 <pre>
15947 int fflush(FILE *stream);
15948 </pre>
15949 <p><b>Description</b>
15950 <p><!--para 2 -->
15951 If stream points to an output stream or an update stream in which the most recent
15952 operation was not input, the fflush function causes any unwritten data for that stream
15953 to be delivered to the host environment to be written to the file; otherwise, the behavior is
15954 undefined.
15955 <p><!--para 3 -->
15956 If stream is a null pointer, the fflush function performs this flushing action on all
15957 streams for which the behavior is defined above.
15958 <p><b>Returns</b>
15959 <p><!--para 4 -->
15960 The fflush function sets the error indicator for the stream and returns EOF if a write
15961 error occurs, otherwise it returns zero.
15966 <p><b>Synopsis</b>
15967 <p><!--para 1 -->
15968 <pre>
15970 FILE *fopen(const char * restrict filename,
15971 const char * restrict mode);
15972 </pre>
15973 <p><b>Description</b>
15974 <p><!--para 2 -->
15975 The fopen function opens the file whose name is the string pointed to by filename,
15976 and associates a stream with it.
15977 <p><!--para 3 -->
15978 The argument mode points to a string. If the string is one of the following, the file is
15979 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note264"><b>264)</b></a></sup>
15980 r open text file for reading
15981 w truncate to zero length or create text file for writing
15982 wx create text file for writing
15983 a append; open or create text file for writing at end-of-file
15984 rb open binary file for reading
15985 wb truncate to zero length or create binary file for writing
15988 <!--page 324 -->
15989 wbx create binary file for writing
15990 ab append; open or create binary file for writing at end-of-file
15991 r+ open text file for update (reading and writing)
15992 w+ truncate to zero length or create text file for update
15993 w+x create text file for update
15994 a+ append; open or create text file for update, writing at end-of-file
15995 r+b or rb+ open binary file for update (reading and writing)
15996 w+b or wb+ truncate to zero length or create binary file for update
15997 w+bx or wb+x create binary file for update
15998 a+b or ab+ append; open or create binary file for update, writing at end-of-file
15999 <p><!--para 4 -->
16000 Opening a file with read mode ('r' as the first character in the mode argument) fails if
16001 the file does not exist or cannot be read.
16002 <p><!--para 5 -->
16003 Opening a file with exclusive mode ('x' as the last character in the mode argument)
16004 fails if the file already exists or cannot be created. Otherwise, the file is created with
16005 exclusive (also known as non-shared) access to the extent that the underlying system
16006 supports exclusive access.
16007 <p><!--para 6 -->
16008 Opening a file with append mode ('a' as the first character in the mode argument)
16009 causes all subsequent writes to the file to be forced to the then current end-of-file,
16010 regardless of intervening calls to the fseek function. In some implementations, opening
16011 a binary file with append mode ('b' as the second or third character in the above list of
16012 mode argument values) may initially position the file position indicator for the stream
16013 beyond the last data written, because of null character padding.
16014 <p><!--para 7 -->
16015 When a file is opened with update mode ('+' as the second or third character in the
16016 above list of mode argument values), both input and output may be performed on the
16017 associated stream. However, output shall not be directly followed by input without an
16018 intervening call to the fflush function or to a file positioning function (fseek,
16019 fsetpos, or rewind), and input shall not be directly followed by output without an
16020 intervening call to a file positioning function, unless the input operation encounters end-
16021 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
16022 binary stream in some implementations.
16023 <p><!--para 8 -->
16024 When opened, a stream is fully buffered if and only if it can be determined not to refer to
16025 an interactive device. The error and end-of-file indicators for the stream are cleared.
16026 <p><b>Returns</b>
16027 <p><!--para 9 -->
16028 The fopen function returns a pointer to the object controlling the stream. If the open
16029 operation fails, fopen returns a null pointer.
16031 <!--page 325 -->
16033 <p><b>Footnotes</b>
16034 <p><small><a name="note264" href="#note264">264)</a> If the string begins with one of the above sequences, the implementation might choose to ignore the
16035 remaining characters, or it might use them to select different kinds of a file (some of which might not
16037 </small>
16041 <p><b>Synopsis</b>
16042 <p><!--para 1 -->
16043 <pre>
16045 FILE *freopen(const char * restrict filename,
16046 const char * restrict mode,
16047 FILE * restrict stream);
16048 </pre>
16049 <p><b>Description</b>
16050 <p><!--para 2 -->
16051 The freopen function opens the file whose name is the string pointed to by filename
16052 and associates the stream pointed to by stream with it. The mode argument is used just
16054 <p><!--para 3 -->
16055 If filename is a null pointer, the freopen function attempts to change the mode of
16056 the stream to that specified by mode, as if the name of the file currently associated with
16057 the stream had been used. It is implementation-defined which changes of mode are
16058 permitted (if any), and under what circumstances.
16059 <p><!--para 4 -->
16060 The freopen function first attempts to close any file that is associated with the specified
16061 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
16062 stream are cleared.
16063 <p><b>Returns</b>
16064 <p><!--para 5 -->
16065 The freopen function returns a null pointer if the open operation fails. Otherwise,
16066 freopen returns the value of stream.
16068 <p><b>Footnotes</b>
16069 <p><small><a name="note265" href="#note265">265)</a> The primary use of the freopen function is to change the file associated with a standard text stream
16070 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
16071 returned by the fopen function may be assigned.
16072 </small>
16076 <p><b>Synopsis</b>
16077 <p><!--para 1 -->
16078 <pre>
16080 void setbuf(FILE * restrict stream,
16081 char * restrict buf);
16082 </pre>
16083 <p><b>Description</b>
16084 <p><!--para 2 -->
16085 Except that it returns no value, the setbuf function is equivalent to the setvbuf
16086 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
16087 is a null pointer), with the value _IONBF for mode.
16092 <!--page 326 -->
16093 <p><b>Returns</b>
16094 <p><!--para 3 -->
16095 The setbuf function returns no value.
16100 <p><b>Synopsis</b>
16101 <p><!--para 1 -->
16102 <pre>
16104 int setvbuf(FILE * restrict stream,
16105 char * restrict buf,
16106 int mode, size_t size);
16107 </pre>
16108 <p><b>Description</b>
16109 <p><!--para 2 -->
16110 The setvbuf function may be used only after the stream pointed to by stream has
16111 been associated with an open file and before any other operation (other than an
16112 unsuccessful call to setvbuf) is performed on the stream. The argument mode
16113 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
16114 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
16115 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
16116 used instead of a buffer allocated by the setvbuf function<sup><a href="#note266"><b>266)</b></a></sup> and the argument size
16117 specifies the size of the array; otherwise, size may determine the size of a buffer
16118 allocated by the setvbuf function. The contents of the array at any time are
16119 indeterminate.
16120 <p><b>Returns</b>
16121 <p><!--para 3 -->
16122 The setvbuf function returns zero on success, or nonzero if an invalid value is given
16123 for mode or if the request cannot be honored.
16128 <!--page 327 -->
16130 <p><b>Footnotes</b>
16131 <p><small><a name="note266" href="#note266">266)</a> The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
16132 before a buffer that has automatic storage duration is deallocated upon block exit.
16133 </small>
16137 <p><!--para 1 -->
16138 The formatted input/output functions shall behave as if there is a sequence point after the
16141 <p><b>Footnotes</b>
16142 <p><small><a name="note267" href="#note267">267)</a> The fprintf functions perform writes to memory for the %n specifier.
16143 </small>
16147 <p><b>Synopsis</b>
16148 <p><!--para 1 -->
16149 <pre>
16151 int fprintf(FILE * restrict stream,
16152 const char * restrict format, ...);
16153 </pre>
16154 <p><b>Description</b>
16155 <p><!--para 2 -->
16156 The fprintf function writes output to the stream pointed to by stream, under control
16157 of the string pointed to by format that specifies how subsequent arguments are
16158 converted for output. If there are insufficient arguments for the format, the behavior is
16159 undefined. If the format is exhausted while arguments remain, the excess arguments are
16160 evaluated (as always) but are otherwise ignored. The fprintf function returns when
16161 the end of the format string is encountered.
16162 <p><!--para 3 -->
16163 The format shall be a multibyte character sequence, beginning and ending in its initial
16164 shift state. The format is composed of zero or more directives: ordinary multibyte
16165 characters (not %), which are copied unchanged to the output stream; and conversion
16166 specifications, each of which results in fetching zero or more subsequent arguments,
16167 converting them, if applicable, according to the corresponding conversion specifier, and
16168 then writing the result to the output stream.
16169 <p><!--para 4 -->
16170 Each conversion specification is introduced by the character %. After the %, the following
16171 appear in sequence:
16172 <ul>
16173 <li> Zero or more flags (in any order) that modify the meaning of the conversion
16174 specification.
16175 <li> An optional minimum field width. If the converted value has fewer characters than the
16176 field width, it is padded with spaces (by default) on the left (or right, if the left
16177 adjustment flag, described later, has been given) to the field width. The field width
16178 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note268"><b>268)</b></a></sup>
16179 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
16180 o, u, x, and X conversions, the number of digits to appear after the decimal-point
16181 character for a, A, e, E, f, and F conversions, the maximum number of significant
16182 digits for the g and G conversions, or the maximum number of bytes to be written for
16185 <!--page 328 -->
16186 s conversions. The precision takes the form of a period (.) followed either by an
16187 asterisk * (described later) or by an optional decimal integer; if only the period is
16188 specified, the precision is taken as zero. If a precision appears with any other
16189 conversion specifier, the behavior is undefined.
16190 <li> An optional length modifier that specifies the size of the argument.
16191 <li> A conversion specifier character that specifies the type of conversion to be applied.
16192 </ul>
16193 <p><!--para 5 -->
16194 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
16195 this case, an int argument supplies the field width or precision. The arguments
16196 specifying field width, or precision, or both, shall appear (in that order) before the
16197 argument (if any) to be converted. A negative field width argument is taken as a - flag
16198 followed by a positive field width. A negative precision argument is taken as if the
16199 precision were omitted.
16200 <p><!--para 6 -->
16201 The flag characters and their meanings are:
16202 - The result of the conversion is left-justified within the field. (It is right-justified if
16203 <pre>
16204 this flag is not specified.)
16205 </pre>
16206 + The result of a signed conversion always begins with a plus or minus sign. (It
16207 <pre>
16208 begins with a sign only when a negative value is converted if this flag is not
16210 </pre>
16211 space If the first character of a signed conversion is not a sign, or if a signed conversion
16212 <pre>
16213 results in no characters, a space is prefixed to the result. If the space and + flags
16214 both appear, the space flag is ignored.
16215 </pre>
16216 # The result is converted to an ''alternative form''. For o conversion, it increases
16217 <pre>
16218 the precision, if and only if necessary, to force the first digit of the result to be a
16219 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
16220 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
16221 and G conversions, the result of converting a floating-point number always
16222 contains a decimal-point character, even if no digits follow it. (Normally, a
16223 decimal-point character appears in the result of these conversions only if a digit
16224 follows it.) For g and G conversions, trailing zeros are not removed from the
16225 result. For other conversions, the behavior is undefined.
16226 </pre>
16227 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
16228 <pre>
16229 (following any indication of sign or base) are used to pad to the field width rather
16230 than performing space padding, except when converting an infinity or NaN. If the
16231 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
16232 </pre>
16235 <!--page 329 -->
16236 <pre>
16237 conversions, if a precision is specified, the 0 flag is ignored. For other
16238 conversions, the behavior is undefined.
16239 </pre>
16240 <p><!--para 7 -->
16241 The length modifiers and their meanings are:
16242 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16243 <pre>
16244 signed char or unsigned char argument (the argument will have
16245 been promoted according to the integer promotions, but its value shall be
16246 converted to signed char or unsigned char before printing); or that
16247 a following n conversion specifier applies to a pointer to a signed char
16248 argument.
16249 </pre>
16250 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16251 <pre>
16252 short int or unsigned short int argument (the argument will
16253 have been promoted according to the integer promotions, but its value shall
16254 be converted to short int or unsigned short int before printing);
16255 or that a following n conversion specifier applies to a pointer to a short
16256 int argument.
16257 </pre>
16258 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16259 <pre>
16260 long int or unsigned long int argument; that a following n
16261 conversion specifier applies to a pointer to a long int argument; that a
16262 following c conversion specifier applies to a wint_t argument; that a
16263 following s conversion specifier applies to a pointer to a wchar_t
16264 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
16265 specifier.
16266 </pre>
16267 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16268 <pre>
16269 long long int or unsigned long long int argument; or that a
16270 following n conversion specifier applies to a pointer to a long long int
16271 argument.
16272 </pre>
16273 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
16274 <pre>
16275 an intmax_t or uintmax_t argument; or that a following n conversion
16276 specifier applies to a pointer to an intmax_t argument.
16277 </pre>
16278 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16279 <pre>
16280 size_t or the corresponding signed integer type argument; or that a
16281 following n conversion specifier applies to a pointer to a signed integer type
16282 corresponding to size_t argument.
16283 </pre>
16284 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16285 <!--page 330 -->
16286 <pre>
16287 ptrdiff_t or the corresponding unsigned integer type argument; or that a
16288 following n conversion specifier applies to a pointer to a ptrdiff_t
16289 argument.
16290 </pre>
16291 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16292 <pre>
16293 applies to a long double argument.
16294 </pre>
16295 If a length modifier appears with any conversion specifier other than as specified above,
16296 the behavior is undefined.
16297 <p><!--para 8 -->
16298 The conversion specifiers and their meanings are:
16299 d,i The int argument is converted to signed decimal in the style [-]dddd. The
16300 <pre>
16301 precision specifies the minimum number of digits to appear; if the value
16302 being converted can be represented in fewer digits, it is expanded with
16303 leading zeros. The default precision is 1. The result of converting a zero
16304 value with a precision of zero is no characters.
16305 </pre>
16306 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
16307 <pre>
16308 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
16309 letters abcdef are used for x conversion and the letters ABCDEF for X
16310 conversion. The precision specifies the minimum number of digits to appear;
16311 if the value being converted can be represented in fewer digits, it is expanded
16312 with leading zeros. The default precision is 1. The result of converting a
16313 zero value with a precision of zero is no characters.
16314 </pre>
16315 f,F A double argument representing a floating-point number is converted to
16316 <pre>
16317 decimal notation in the style [-]ddd.ddd, where the number of digits after
16318 the decimal-point character is equal to the precision specification. If the
16319 precision is missing, it is taken as 6; if the precision is zero and the # flag is
16320 not specified, no decimal-point character appears. If a decimal-point
16321 character appears, at least one digit appears before it. The value is rounded to
16322 the appropriate number of digits.
16323 A double argument representing an infinity is converted in one of the styles
16324 [-]inf or [-]infinity -- which style is implementation-defined. A
16325 double argument representing a NaN is converted in one of the styles
16326 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
16327 any n-char-sequence, is implementation-defined. The F conversion specifier
16328 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
16330 </pre>
16331 e,E A double argument representing a floating-point number is converted in the
16332 <pre>
16333 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
16334 argument is nonzero) before the decimal-point character and the number of
16335 digits after it is equal to the precision; if the precision is missing, it is taken as
16336 </pre>
16339 <!--page 331 -->
16340 <pre>
16341 6; if the precision is zero and the # flag is not specified, no decimal-point
16342 character appears. The value is rounded to the appropriate number of digits.
16343 The E conversion specifier produces a number with E instead of e
16344 introducing the exponent. The exponent always contains at least two digits,
16345 and only as many more digits as necessary to represent the exponent. If the
16346 value is zero, the exponent is zero.
16347 A double argument representing an infinity or NaN is converted in the style
16348 of an f or F conversion specifier.
16349 </pre>
16350 g,G A double argument representing a floating-point number is converted in
16351 <pre>
16352 style f or e (or in style F or E in the case of a G conversion specifier),
16353 depending on the value converted and the precision. Let P equal the
16354 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
16355 Then, if a conversion with style E would have an exponent of X:
16356 -- if P > X >= -4, the conversion is with style f (or F) and precision
16357 P - (X + 1).
16358 -- otherwise, the conversion is with style e (or E) and precision P - 1.
16359 Finally, unless the # flag is used, any trailing zeros are removed from the
16360 fractional portion of the result and the decimal-point character is removed if
16361 there is no fractional portion remaining.
16362 A double argument representing an infinity or NaN is converted in the style
16363 of an f or F conversion specifier.
16364 </pre>
16365 a,A A double argument representing a floating-point number is converted in the
16366 <pre>
16367 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
16368 nonzero if the argument is a normalized floating-point number and is
16369 otherwise unspecified) before the decimal-point character<sup><a href="#note271"><b>271)</b></a></sup> and the number
16370 of hexadecimal digits after it is equal to the precision; if the precision is
16371 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
16372 an exact representation of the value; if the precision is missing and
16373 FLT_RADIX is not a power of 2, then the precision is sufficient to
16374 </pre>
16379 <!--page 332 -->
16380 <pre>
16381 distinguish<sup><a href="#note272"><b>272)</b></a></sup> values of type double, except that trailing zeros may be
16382 omitted; if the precision is zero and the # flag is not specified, no decimal-
16383 point character appears. The letters abcdef are used for a conversion and
16384 the letters ABCDEF for A conversion. The A conversion specifier produces a
16385 number with X and P instead of x and p. The exponent always contains at
16386 least one digit, and only as many more digits as necessary to represent the
16387 decimal exponent of 2. If the value is zero, the exponent is zero.
16388 A double argument representing an infinity or NaN is converted in the style
16389 of an f or F conversion specifier.
16390 </pre>
16391 c If no l length modifier is present, the int argument is converted to an
16392 <pre>
16393 unsigned char, and the resulting character is written.
16394 If an l length modifier is present, the wint_t argument is converted as if by
16395 an ls conversion specification with no precision and an argument that points
16396 to the initial element of a two-element array of wchar_t, the first element
16397 containing the wint_t argument to the lc conversion specification and the
16398 second a null wide character.
16399 </pre>
16400 s If no l length modifier is present, the argument shall be a pointer to the initial
16401 <pre>
16402 element of an array of character type.<sup><a href="#note273"><b>273)</b></a></sup> Characters from the array are
16403 written up to (but not including) the terminating null character. If the
16404 precision is specified, no more than that many bytes are written. If the
16405 precision is not specified or is greater than the size of the array, the array shall
16406 contain a null character.
16407 If an l length modifier is present, the argument shall be a pointer to the initial
16408 element of an array of wchar_t type. Wide characters from the array are
16409 converted to multibyte characters (each as if by a call to the wcrtomb
16410 function, with the conversion state described by an mbstate_t object
16411 initialized to zero before the first wide character is converted) up to and
16412 including a terminating null wide character. The resulting multibyte
16413 characters are written up to (but not including) the terminating null character
16414 (byte). If no precision is specified, the array shall contain a null wide
16415 character. If a precision is specified, no more than that many bytes are
16416 written (including shift sequences, if any), and the array shall contain a null
16417 wide character if, to equal the multibyte character sequence length given by
16418 </pre>
16420 <!--page 333 -->
16421 <pre>
16422 the precision, the function would need to access a wide character one past the
16423 end of the array. In no case is a partial multibyte character written.<sup><a href="#note274"><b>274)</b></a></sup>
16424 </pre>
16425 p The argument shall be a pointer to void. The value of the pointer is
16426 <pre>
16427 converted to a sequence of printing characters, in an implementation-defined
16428 manner.
16429 </pre>
16430 n The argument shall be a pointer to signed integer into which is written the
16431 <pre>
16432 number of characters written to the output stream so far by this call to
16433 fprintf. No argument is converted, but one is consumed. If the conversion
16434 specification includes any flags, a field width, or a precision, the behavior is
16435 undefined.
16436 </pre>
16437 % A % character is written. No argument is converted. The complete
16438 <pre>
16439 conversion specification shall be %%.
16440 </pre>
16441 <p><!--para 9 -->
16442 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note275"><b>275)</b></a></sup> If any argument is
16443 not the correct type for the corresponding conversion specification, the behavior is
16444 undefined.
16445 <p><!--para 10 -->
16446 In no case does a nonexistent or small field width cause truncation of a field; if the result
16447 of a conversion is wider than the field width, the field is expanded to contain the
16448 conversion result.
16449 <p><!--para 11 -->
16450 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
16451 to a hexadecimal floating number with the given precision.
16452 <p><b>Recommended practice</b>
16453 <p><!--para 12 -->
16454 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
16455 representable in the given precision, the result should be one of the two adjacent numbers
16456 in hexadecimal floating style with the given precision, with the extra stipulation that the
16457 error should have a correct sign for the current rounding direction.
16458 <p><!--para 13 -->
16459 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
16460 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note276"><b>276)</b></a></sup> If the number of
16461 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
16462 representable with DECIMAL_DIG digits, then the result should be an exact
16463 representation with trailing zeros. Otherwise, the source value is bounded by two
16464 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
16467 <!--page 334 -->
16468 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
16469 the error should have a correct sign for the current rounding direction.
16470 <p><b>Returns</b>
16471 <p><!--para 14 -->
16472 The fprintf function returns the number of characters transmitted, or a negative value
16473 if an output or encoding error occurred.
16474 <p><b>Environmental limits</b>
16475 <p><!--para 15 -->
16476 The number of characters that can be produced by any single conversion shall be at least
16477 4095.
16478 <p><!--para 16 -->
16479 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
16480 places:
16481 <pre>
16484 /* ... */
16485 char *weekday, *month; // pointers to strings
16486 int day, hour, min;
16488 weekday, month, day, hour, min);
16490 </pre>
16492 <p><!--para 17 -->
16493 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
16494 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
16495 the first of which is denoted here by a and the second by an uppercase letter.
16496 <p><!--para 18 -->
16497 Given the following wide string with length seven,
16498 <pre>
16500 </pre>
16501 the seven calls
16502 <pre>
16510 </pre>
16511 will print the following seven lines:
16512 <pre>
16513 |1234567890123|
16514 | X Yabc Z W|
16515 | X Yabc Z |
16516 | X Yabc Z|
16517 | X Yabc Z W|
16518 | abc Z W|
16519 | Z|
16520 </pre>
16522 <p><b> Forward references</b>: conversion state (<a href="#7.28.6">7.28.6</a>), the wcrtomb function (<a href="#7.28.6.3.3">7.28.6.3.3</a>).
16523 <!--page 335 -->
16525 <p><b>Footnotes</b>
16526 <p><small><a name="note268" href="#note268">268)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
16527 </small>
16528 <p><small><a name="note269" href="#note269">269)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
16529 include a minus sign.
16530 </small>
16531 <p><small><a name="note270" href="#note270">270)</a> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
16532 the # and 0 flag characters have no effect.
16533 </small>
16534 <p><small><a name="note271" href="#note271">271)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
16535 that subsequent digits align to nibble (4-bit) boundaries.
16536 </small>
16537 <p><small><a name="note272" href="#note272">272)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
16538 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
16539 might suffice depending on the implementation's scheme for determining the digit to the left of the
16540 decimal-point character.
16541 </small>
16542 <p><small><a name="note273" href="#note273">273)</a> No special provisions are made for multibyte characters.
16543 </small>
16544 <p><small><a name="note274" href="#note274">274)</a> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
16545 </small>
16546 <p><small><a name="note275" href="#note275">275)</a> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
16547 </small>
16548 <p><small><a name="note276" href="#note276">276)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
16549 given format specifier. The number of significant digits is determined by the format specifier, and in
16550 the case of fixed-point conversion by the source value as well.
16551 </small>
16555 <p><b>Synopsis</b>
16556 <p><!--para 1 -->
16557 <pre>
16559 int fscanf(FILE * restrict stream,
16560 const char * restrict format, ...);
16561 </pre>
16562 <p><b>Description</b>
16563 <p><!--para 2 -->
16564 The fscanf function reads input from the stream pointed to by stream, under control
16565 of the string pointed to by format that specifies the admissible input sequences and how
16566 they are to be converted for assignment, using subsequent arguments as pointers to the
16567 objects to receive the converted input. If there are insufficient arguments for the format,
16568 the behavior is undefined. If the format is exhausted while arguments remain, the excess
16569 arguments are evaluated (as always) but are otherwise ignored.
16570 <p><!--para 3 -->
16571 The format shall be a multibyte character sequence, beginning and ending in its initial
16572 shift state. The format is composed of zero or more directives: one or more white-space
16573 characters, an ordinary multibyte character (neither % nor a white-space character), or a
16574 conversion specification. Each conversion specification is introduced by the character %.
16575 After the %, the following appear in sequence:
16576 <ul>
16577 <li> An optional assignment-suppressing character *.
16578 <li> An optional decimal integer greater than zero that specifies the maximum field width
16579 (in characters).
16580 <li> An optional length modifier that specifies the size of the receiving object.
16581 <li> A conversion specifier character that specifies the type of conversion to be applied.
16582 </ul>
16583 <p><!--para 4 -->
16584 The fscanf function executes each directive of the format in turn. When all directives
16585 have been executed, or if a directive fails (as detailed below), the function returns.
16586 Failures are described as input failures (due to the occurrence of an encoding error or the
16587 unavailability of input characters), or matching failures (due to inappropriate input).
16588 <p><!--para 5 -->
16589 A directive composed of white-space character(s) is executed by reading input up to the
16590 first non-white-space character (which remains unread), or until no more characters can
16591 be read.
16592 <p><!--para 6 -->
16593 A directive that is an ordinary multibyte character is executed by reading the next
16594 characters of the stream. If any of those characters differ from the ones composing the
16595 directive, the directive fails and the differing and subsequent characters remain unread.
16596 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
16597 read, the directive fails.
16598 <p><!--para 7 -->
16599 A directive that is a conversion specification defines a set of matching input sequences, as
16600 described below for each specifier. A conversion specification is executed in the
16601 <!--page 336 -->
16602 following steps:
16603 <p><!--para 8 -->
16604 Input white-space characters (as specified by the isspace function) are skipped, unless
16605 the specification includes a [, c, or n specifier.<sup><a href="#note277"><b>277)</b></a></sup>
16606 <p><!--para 9 -->
16607 An input item is read from the stream, unless the specification includes an n specifier. An
16608 input item is defined as the longest sequence of input characters which does not exceed
16609 any specified field width and which is, or is a prefix of, a matching input sequence.<sup><a href="#note278"><b>278)</b></a></sup>
16610 The first character, if any, after the input item remains unread. If the length of the input
16611 item is zero, the execution of the directive fails; this condition is a matching failure unless
16612 end-of-file, an encoding error, or a read error prevented input from the stream, in which
16613 case it is an input failure.
16614 <p><!--para 10 -->
16615 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
16616 count of input characters) is converted to a type appropriate to the conversion specifier. If
16617 the input item is not a matching sequence, the execution of the directive fails: this
16618 condition is a matching failure. Unless assignment suppression was indicated by a *, the
16619 result of the conversion is placed in the object pointed to by the first argument following
16620 the format argument that has not already received a conversion result. If this object
16621 does not have an appropriate type, or if the result of the conversion cannot be represented
16622 in the object, the behavior is undefined.
16623 <p><!--para 11 -->
16624 The length modifiers and their meanings are:
16625 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16626 <pre>
16627 to an argument with type pointer to signed char or unsigned char.
16628 </pre>
16629 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16630 <pre>
16631 to an argument with type pointer to short int or unsigned short
16632 int.
16633 </pre>
16634 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16635 <pre>
16636 to an argument with type pointer to long int or unsigned long
16637 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
16638 an argument with type pointer to double; or that a following c, s, or [
16639 conversion specifier applies to an argument with type pointer to wchar_t.
16640 </pre>
16641 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16642 <pre>
16643 to an argument with type pointer to long long int or unsigned
16644 long long int.
16645 </pre>
16649 <!--page 337 -->
16650 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16651 <pre>
16652 to an argument with type pointer to intmax_t or uintmax_t.
16653 </pre>
16654 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16655 <pre>
16656 to an argument with type pointer to size_t or the corresponding signed
16657 integer type.
16658 </pre>
16659 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16660 <pre>
16661 to an argument with type pointer to ptrdiff_t or the corresponding
16662 unsigned integer type.
16663 </pre>
16664 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16665 <pre>
16666 applies to an argument with type pointer to long double.
16667 </pre>
16668 If a length modifier appears with any conversion specifier other than as specified above,
16669 the behavior is undefined.
16670 <p><!--para 12 -->
16671 The conversion specifiers and their meanings are:
16672 d Matches an optionally signed decimal integer, whose format is the same as
16673 <pre>
16674 expected for the subject sequence of the strtol function with the value 10
16675 for the base argument. The corresponding argument shall be a pointer to
16676 signed integer.
16677 </pre>
16678 i Matches an optionally signed integer, whose format is the same as expected
16679 <pre>
16680 for the subject sequence of the strtol function with the value 0 for the
16681 base argument. The corresponding argument shall be a pointer to signed
16682 integer.
16683 </pre>
16684 o Matches an optionally signed octal integer, whose format is the same as
16685 <pre>
16686 expected for the subject sequence of the strtoul function with the value 8
16687 for the base argument. The corresponding argument shall be a pointer to
16688 unsigned integer.
16689 </pre>
16690 u Matches an optionally signed decimal integer, whose format is the same as
16691 <pre>
16692 expected for the subject sequence of the strtoul function with the value 10
16693 for the base argument. The corresponding argument shall be a pointer to
16694 unsigned integer.
16695 </pre>
16696 x Matches an optionally signed hexadecimal integer, whose format is the same
16697 <pre>
16698 as expected for the subject sequence of the strtoul function with the value
16699 16 for the base argument. The corresponding argument shall be a pointer to
16700 unsigned integer.
16701 </pre>
16702 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
16703 <!--page 338 -->
16704 <pre>
16705 format is the same as expected for the subject sequence of the strtod
16706 function. The corresponding argument shall be a pointer to floating.
16707 </pre>
16708 c Matches a sequence of characters of exactly the number specified by the field
16709 <pre>
16710 width (1 if no field width is present in the directive).<sup><a href="#note279"><b>279)</b></a></sup>
16711 If no l length modifier is present, the corresponding argument shall be a
16712 pointer to the initial element of a character array large enough to accept the
16713 sequence. No null character is added.
16714 If an l length modifier is present, the input shall be a sequence of multibyte
16715 characters that begins in the initial shift state. Each multibyte character in the
16716 sequence is converted to a wide character as if by a call to the mbrtowc
16717 function, with the conversion state described by an mbstate_t object
16718 initialized to zero before the first multibyte character is converted. The
16719 corresponding argument shall be a pointer to the initial element of an array of
16720 wchar_t large enough to accept the resulting sequence of wide characters.
16721 No null wide character is added.
16722 </pre>
16723 s Matches a sequence of non-white-space characters.<sup><a href="#note279"><b>279)</b></a></sup>
16724 <pre>
16725 If no l length modifier is present, the corresponding argument shall be a
16726 pointer to the initial element of a character array large enough to accept the
16727 sequence and a terminating null character, which will be added automatically.
16728 If an l length modifier is present, the input shall be a sequence of multibyte
16729 characters that begins in the initial shift state. Each multibyte character is
16730 converted to a wide character as if by a call to the mbrtowc function, with
16731 the conversion state described by an mbstate_t object initialized to zero
16732 before the first multibyte character is converted. The corresponding argument
16733 shall be a pointer to the initial element of an array of wchar_t large enough
16734 to accept the sequence and the terminating null wide character, which will be
16735 added automatically.
16736 </pre>
16737 [ Matches a nonempty sequence of characters from a set of expected characters
16738 <pre>
16740 If no l length modifier is present, the corresponding argument shall be a
16741 pointer to the initial element of a character array large enough to accept the
16742 sequence and a terminating null character, which will be added automatically.
16743 If an l length modifier is present, the input shall be a sequence of multibyte
16744 characters that begins in the initial shift state. Each multibyte character is
16745 converted to a wide character as if by a call to the mbrtowc function, with
16746 the conversion state described by an mbstate_t object initialized to zero
16747 </pre>
16749 <!--page 339 -->
16750 <pre>
16751 before the first multibyte character is converted. The corresponding argument
16752 shall be a pointer to the initial element of an array of wchar_t large enough
16753 to accept the sequence and the terminating null wide character, which will be
16754 added automatically.
16755 The conversion specifier includes all subsequent characters in the format
16756 string, up to and including the matching right bracket (]). The characters
16757 between the brackets (the scanlist) compose the scanset, unless the character
16758 after the left bracket is a circumflex (^), in which case the scanset contains all
16759 characters that do not appear in the scanlist between the circumflex and the
16760 right bracket. If the conversion specifier begins with [] or [^], the right
16761 bracket character is in the scanlist and the next following right bracket
16762 character is the matching right bracket that ends the specification; otherwise
16763 the first following right bracket character is the one that ends the
16764 specification. If a - character is in the scanlist and is not the first, nor the
16765 second where the first character is a ^, nor the last character, the behavior is
16766 implementation-defined.
16767 </pre>
16768 p Matches an implementation-defined set of sequences, which should be the
16769 <pre>
16770 same as the set of sequences that may be produced by the %p conversion of
16771 the fprintf function. The corresponding argument shall be a pointer to a
16772 pointer to void. The input item is converted to a pointer value in an
16773 implementation-defined manner. If the input item is a value converted earlier
16774 during the same program execution, the pointer that results shall compare
16775 equal to that value; otherwise the behavior of the %p conversion is undefined.
16776 </pre>
16777 n No input is consumed. The corresponding argument shall be a pointer to
16778 <pre>
16779 signed integer into which is to be written the number of characters read from
16780 the input stream so far by this call to the fscanf function. Execution of a
16781 %n directive does not increment the assignment count returned at the
16782 completion of execution of the fscanf function. No argument is converted,
16783 but one is consumed. If the conversion specification includes an assignment-
16784 suppressing character or a field width, the behavior is undefined.
16785 </pre>
16786 % Matches a single % character; no conversion or assignment occurs. The
16787 <pre>
16788 complete conversion specification shall be %%.
16789 </pre>
16790 <p><!--para 13 -->
16791 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note280"><b>280)</b></a></sup>
16792 <p><!--para 14 -->
16793 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
16794 respectively, a, e, f, g, and x.
16798 <!--page 340 -->
16799 <p><!--para 15 -->
16800 Trailing white space (including new-line characters) is left unread unless matched by a
16801 directive. The success of literal matches and suppressed assignments is not directly
16802 determinable other than via the %n directive.
16803 <p><b>Returns</b>
16804 <p><!--para 16 -->
16805 The fscanf function returns the value of the macro EOF if an input failure occurs
16806 before the first conversion (if any) has completed. Otherwise, the function returns the
16807 number of input items assigned, which can be fewer than provided for, or even zero, in
16808 the event of an early matching failure.
16809 <p><!--para 17 -->
16810 EXAMPLE 1 The call:
16811 <pre>
16813 /* ... */
16814 int n, i; float x; char name[50];
16816 </pre>
16817 with the input line:
16818 <pre>
16819 25 54.32E-1 thompson
16820 </pre>
16821 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
16822 thompson\0.
16824 <p><!--para 18 -->
16825 EXAMPLE 2 The call:
16826 <pre>
16828 /* ... */
16829 int i; float x; char name[50];
16831 </pre>
16832 with input:
16833 <pre>
16834 56789 0123 56a72
16835 </pre>
16836 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
16837 sequence 56\0. The next character read from the input stream will be a.
16839 <p><!--para 19 -->
16840 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
16841 <pre>
16843 /* ... */
16844 int count; float quant; char units[21], item[21];
16845 do {
16848 } while (!feof(stdin) && !ferror(stdin));
16849 </pre>
16850 <p><!--para 20 -->
16851 If the stdin stream contains the following lines:
16852 <!--page 341 -->
16853 <pre>
16854 2 quarts of oil
16855 -12.8degrees Celsius
16856 lots of luck
16857 10.0LBS of
16858 dirt
16859 100ergs of energy
16860 </pre>
16861 the execution of the above example will be analogous to the following assignments:
16862 <pre>
16864 count = 3;
16869 count = 3;
16871 count = EOF;
16872 </pre>
16874 <p><!--para 21 -->
16875 EXAMPLE 4 In:
16876 <pre>
16878 /* ... */
16879 int d1, d2, n1, n2, i;
16881 </pre>
16882 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
16883 of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
16885 <p><!--para 22 -->
16886 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
16887 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
16888 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
16889 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
16890 entry into the alternate shift state.
16891 <p><!--para 23 -->
16892 After the call:
16893 <pre>
16895 /* ... */
16896 char str[50];
16898 </pre>
16899 with the input line:
16900 <pre>
16901 a(uparrow) X Y(downarrow) bc
16902 </pre>
16903 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
16904 characters, in the more general case) appears to be a single-byte white-space character.
16905 <p><!--para 24 -->
16906 In contrast, after the call:
16907 <pre>
16910 /* ... */
16911 wchar_t wstr[50];
16913 </pre>
16914 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
16915 terminating null wide character.
16916 <p><!--para 25 -->
16917 However, the call:
16918 <!--page 342 -->
16919 <pre>
16922 /* ... */
16923 wchar_t wstr[50];
16925 </pre>
16926 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
16927 string.
16928 <p><!--para 26 -->
16929 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
16930 character Y, after the call:
16931 <pre>
16934 /* ... */
16935 wchar_t wstr[50];
16937 </pre>
16938 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
16939 multibyte character.
16941 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>), the
16942 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.22.1.4">7.22.1.4</a>), conversion state
16945 <p><b>Footnotes</b>
16946 <p><small><a name="note277" href="#note277">277)</a> These white-space characters are not counted against a specified field width.
16947 </small>
16948 <p><small><a name="note278" href="#note278">278)</a> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
16949 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
16950 </small>
16951 <p><small><a name="note279" href="#note279">279)</a> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
16952 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
16953 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
16954 </small>
16955 <p><small><a name="note280" href="#note280">280)</a> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
16956 </small>
16960 <p><b>Synopsis</b>
16961 <p><!--para 1 -->
16962 <pre>
16964 int printf(const char * restrict format, ...);
16965 </pre>
16966 <p><b>Description</b>
16967 <p><!--para 2 -->
16968 The printf function is equivalent to fprintf with the argument stdout interposed
16969 before the arguments to printf.
16970 <p><b>Returns</b>
16971 <p><!--para 3 -->
16972 The printf function returns the number of characters transmitted, or a negative value if
16973 an output or encoding error occurred.
16977 <p><b>Synopsis</b>
16978 <p><!--para 1 -->
16979 <pre>
16981 int scanf(const char * restrict format, ...);
16982 </pre>
16983 <p><b>Description</b>
16984 <p><!--para 2 -->
16985 The scanf function is equivalent to fscanf with the argument stdin interposed
16986 before the arguments to scanf.
16987 <!--page 343 -->
16988 <p><b>Returns</b>
16989 <p><!--para 3 -->
16990 The scanf function returns the value of the macro EOF if an input failure occurs before
16991 the first conversion (if any) has completed. Otherwise, the scanf function returns the
16992 number of input items assigned, which can be fewer than provided for, or even zero, in
16993 the event of an early matching failure.
16997 <p><b>Synopsis</b>
16998 <p><!--para 1 -->
16999 <pre>
17001 int snprintf(char * restrict s, size_t n,
17002 const char * restrict format, ...);
17003 </pre>
17004 <p><b>Description</b>
17005 <p><!--para 2 -->
17006 The snprintf function is equivalent to fprintf, except that the output is written into
17007 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
17008 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
17009 discarded rather than being written to the array, and a null character is written at the end
17010 of the characters actually written into the array. If copying takes place between objects
17011 that overlap, the behavior is undefined.
17012 <p><b>Returns</b>
17013 <p><!--para 3 -->
17014 The snprintf function returns the number of characters that would have been written
17015 had n been sufficiently large, not counting the terminating null character, or a negative
17016 value if an encoding error occurred. Thus, the null-terminated output has been
17017 completely written if and only if the returned value is nonnegative and less than n.
17021 <p><b>Synopsis</b>
17022 <p><!--para 1 -->
17023 <pre>
17025 int sprintf(char * restrict s,
17026 const char * restrict format, ...);
17027 </pre>
17028 <p><b>Description</b>
17029 <p><!--para 2 -->
17030 The sprintf function is equivalent to fprintf, except that the output is written into
17031 an array (specified by the argument s) rather than to a stream. A null character is written
17032 at the end of the characters written; it is not counted as part of the returned value. If
17033 copying takes place between objects that overlap, the behavior is undefined.
17034 <p><b>Returns</b>
17035 <p><!--para 3 -->
17036 The sprintf function returns the number of characters written in the array, not
17037 counting the terminating null character, or a negative value if an encoding error occurred.
17038 <!--page 344 -->
17042 <p><b>Synopsis</b>
17043 <p><!--para 1 -->
17044 <pre>
17046 int sscanf(const char * restrict s,
17047 const char * restrict format, ...);
17048 </pre>
17049 <p><b>Description</b>
17050 <p><!--para 2 -->
17051 The sscanf function is equivalent to fscanf, except that input is obtained from a
17052 string (specified by the argument s) rather than from a stream. Reaching the end of the
17053 string is equivalent to encountering end-of-file for the fscanf function. If copying
17054 takes place between objects that overlap, the behavior is undefined.
17055 <p><b>Returns</b>
17056 <p><!--para 3 -->
17057 The sscanf function returns the value of the macro EOF if an input failure occurs
17058 before the first conversion (if any) has completed. Otherwise, the sscanf function
17059 returns the number of input items assigned, which can be fewer than provided for, or even
17060 zero, in the event of an early matching failure.
17064 <p><b>Synopsis</b>
17065 <p><!--para 1 -->
17066 <pre>
17069 int vfprintf(FILE * restrict stream,
17070 const char * restrict format,
17071 va_list arg);
17072 </pre>
17073 <p><b>Description</b>
17074 <p><!--para 2 -->
17075 The vfprintf function is equivalent to fprintf, with the variable argument list
17076 replaced by arg, which shall have been initialized by the va_start macro (and
17077 possibly subsequent va_arg calls). The vfprintf function does not invoke the
17079 <p><b>Returns</b>
17080 <p><!--para 3 -->
17081 The vfprintf function returns the number of characters transmitted, or a negative
17082 value if an output or encoding error occurred.
17083 <p><!--para 4 -->
17084 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
17089 <!--page 345 -->
17090 <pre>
17093 void error(char *function_name, char *format, ...)
17094 {
17095 va_list args;
17096 va_start(args, format);
17097 // print out name of function causing error
17099 // print out remainder of message
17100 vfprintf(stderr, format, args);
17101 va_end(args);
17102 }
17103 </pre>
17106 <p><b>Footnotes</b>
17107 <p><small><a name="note281" href="#note281">281)</a> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
17108 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
17109 </small>
17113 <p><b>Synopsis</b>
17114 <p><!--para 1 -->
17115 <pre>
17118 int vfscanf(FILE * restrict stream,
17119 const char * restrict format,
17120 va_list arg);
17121 </pre>
17122 <p><b>Description</b>
17123 <p><!--para 2 -->
17124 The vfscanf function is equivalent to fscanf, with the variable argument list
17125 replaced by arg, which shall have been initialized by the va_start macro (and
17126 possibly subsequent va_arg calls). The vfscanf function does not invoke the
17128 <p><b>Returns</b>
17129 <p><!--para 3 -->
17130 The vfscanf function returns the value of the macro EOF if an input failure occurs
17131 before the first conversion (if any) has completed. Otherwise, the vfscanf function
17132 returns the number of input items assigned, which can be fewer than provided for, or even
17133 zero, in the event of an early matching failure.
17137 <p><b>Synopsis</b>
17138 <p><!--para 1 -->
17139 <pre>
17142 int vprintf(const char * restrict format,
17143 va_list arg);
17144 </pre>
17145 <p><b>Description</b>
17146 <p><!--para 2 -->
17147 The vprintf function is equivalent to printf, with the variable argument list
17148 replaced by arg, which shall have been initialized by the va_start macro (and
17149 <!--page 346 -->
17150 possibly subsequent va_arg calls). The vprintf function does not invoke the
17152 <p><b>Returns</b>
17153 <p><!--para 3 -->
17154 The vprintf function returns the number of characters transmitted, or a negative value
17155 if an output or encoding error occurred.
17159 <p><b>Synopsis</b>
17160 <p><!--para 1 -->
17161 <pre>
17164 int vscanf(const char * restrict format,
17165 va_list arg);
17166 </pre>
17167 <p><b>Description</b>
17168 <p><!--para 2 -->
17169 The vscanf function is equivalent to scanf, with the variable argument list replaced
17170 by arg, which shall have been initialized by the va_start macro (and possibly
17171 subsequent va_arg calls). The vscanf function does not invoke the va_end
17173 <p><b>Returns</b>
17174 <p><!--para 3 -->
17175 The vscanf function returns the value of the macro EOF if an input failure occurs
17176 before the first conversion (if any) has completed. Otherwise, the vscanf function
17177 returns the number of input items assigned, which can be fewer than provided for, or even
17178 zero, in the event of an early matching failure.
17182 <p><b>Synopsis</b>
17183 <p><!--para 1 -->
17184 <pre>
17187 int vsnprintf(char * restrict s, size_t n,
17188 const char * restrict format,
17189 va_list arg);
17190 </pre>
17191 <p><b>Description</b>
17192 <p><!--para 2 -->
17193 The vsnprintf function is equivalent to snprintf, with the variable argument list
17194 replaced by arg, which shall have been initialized by the va_start macro (and
17195 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
17196 va_end macro.<sup><a href="#note281"><b>281)</b></a></sup> If copying takes place between objects that overlap, the behavior is
17197 undefined.
17198 <!--page 347 -->
17199 <p><b>Returns</b>
17200 <p><!--para 3 -->
17201 The vsnprintf function returns the number of characters that would have been written
17202 had n been sufficiently large, not counting the terminating null character, or a negative
17203 value if an encoding error occurred. Thus, the null-terminated output has been
17204 completely written if and only if the returned value is nonnegative and less than n.
17208 <p><b>Synopsis</b>
17209 <p><!--para 1 -->
17210 <pre>
17213 int vsprintf(char * restrict s,
17214 const char * restrict format,
17215 va_list arg);
17216 </pre>
17217 <p><b>Description</b>
17218 <p><!--para 2 -->
17219 The vsprintf function is equivalent to sprintf, with the variable argument list
17220 replaced by arg, which shall have been initialized by the va_start macro (and
17221 possibly subsequent va_arg calls). The vsprintf function does not invoke the
17222 va_end macro.<sup><a href="#note281"><b>281)</b></a></sup> If copying takes place between objects that overlap, the behavior is
17223 undefined.
17224 <p><b>Returns</b>
17225 <p><!--para 3 -->
17226 The vsprintf function returns the number of characters written in the array, not
17227 counting the terminating null character, or a negative value if an encoding error occurred.
17231 <p><b>Synopsis</b>
17232 <p><!--para 1 -->
17233 <pre>
17236 int vsscanf(const char * restrict s,
17237 const char * restrict format,
17238 va_list arg);
17239 </pre>
17240 <p><b>Description</b>
17241 <p><!--para 2 -->
17242 The vsscanf function is equivalent to sscanf, with the variable argument list
17243 replaced by arg, which shall have been initialized by the va_start macro (and
17244 possibly subsequent va_arg calls). The vsscanf function does not invoke the
17246 <p><b>Returns</b>
17247 <p><!--para 3 -->
17248 The vsscanf function returns the value of the macro EOF if an input failure occurs
17249 before the first conversion (if any) has completed. Otherwise, the vsscanf function
17250 <!--page 348 -->
17251 returns the number of input items assigned, which can be fewer than provided for, or even
17252 zero, in the event of an early matching failure.
17259 <p><b>Synopsis</b>
17260 <p><!--para 1 -->
17261 <pre>
17263 int fgetc(FILE *stream);
17264 </pre>
17265 <p><b>Description</b>
17266 <p><!--para 2 -->
17267 If the end-of-file indicator for the input stream pointed to by stream is not set and a
17268 next character is present, the fgetc function obtains that character as an unsigned
17269 char converted to an int and advances the associated file position indicator for the
17270 stream (if defined).
17271 <p><b>Returns</b>
17272 <p><!--para 3 -->
17273 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
17274 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
17275 fgetc function returns the next character from the input stream pointed to by stream.
17276 If a read error occurs, the error indicator for the stream is set and the fgetc function
17279 <p><b>Footnotes</b>
17280 <p><small><a name="note282" href="#note282">282)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
17281 </small>
17285 <p><b>Synopsis</b>
17286 <p><!--para 1 -->
17287 <pre>
17289 char *fgets(char * restrict s, int n,
17290 FILE * restrict stream);
17291 </pre>
17292 <p><b>Description</b>
17293 <p><!--para 2 -->
17294 The fgets function reads at most one less than the number of characters specified by n
17295 from the stream pointed to by stream into the array pointed to by s. No additional
17296 characters are read after a new-line character (which is retained) or after end-of-file. A
17297 null character is written immediately after the last character read into the array.
17298 <p><b>Returns</b>
17299 <p><!--para 3 -->
17300 The fgets function returns s if successful. If end-of-file is encountered and no
17301 characters have been read into the array, the contents of the array remain unchanged and a
17302 null pointer is returned. If a read error occurs during the operation, the array contents are
17303 indeterminate and a null pointer is returned.
17305 <!--page 349 -->
17309 <p><b>Synopsis</b>
17310 <p><!--para 1 -->
17311 <pre>
17313 int fputc(int c, FILE *stream);
17314 </pre>
17315 <p><b>Description</b>
17316 <p><!--para 2 -->
17317 The fputc function writes the character specified by c (converted to an unsigned
17318 char) to the output stream pointed to by stream, at the position indicated by the
17319 associated file position indicator for the stream (if defined), and advances the indicator
17320 appropriately. If the file cannot support positioning requests, or if the stream was opened
17321 with append mode, the character is appended to the output stream.
17322 <p><b>Returns</b>
17323 <p><!--para 3 -->
17324 The fputc function returns the character written. If a write error occurs, the error
17325 indicator for the stream is set and fputc returns EOF.
17329 <p><b>Synopsis</b>
17330 <p><!--para 1 -->
17331 <pre>
17333 int fputs(const char * restrict s,
17334 FILE * restrict stream);
17335 </pre>
17336 <p><b>Description</b>
17337 <p><!--para 2 -->
17338 The fputs function writes the string pointed to by s to the stream pointed to by
17339 stream. The terminating null character is not written.
17340 <p><b>Returns</b>
17341 <p><!--para 3 -->
17342 The fputs function returns EOF if a write error occurs; otherwise it returns a
17343 nonnegative value.
17347 <p><b>Synopsis</b>
17348 <p><!--para 1 -->
17349 <pre>
17351 int getc(FILE *stream);
17352 </pre>
17353 <p><b>Description</b>
17354 <p><!--para 2 -->
17355 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
17356 may evaluate stream more than once, so the argument should never be an expression
17357 with side effects.
17358 <!--page 350 -->
17359 <p><b>Returns</b>
17360 <p><!--para 3 -->
17361 The getc function returns the next character from the input stream pointed to by
17362 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
17363 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
17364 getc returns EOF.
17368 <p><b>Synopsis</b>
17369 <p><!--para 1 -->
17370 <pre>
17372 int getchar(void);
17373 </pre>
17374 <p><b>Description</b>
17375 <p><!--para 2 -->
17376 The getchar function is equivalent to getc with the argument stdin.
17377 <p><b>Returns</b>
17378 <p><!--para 3 -->
17379 The getchar function returns the next character from the input stream pointed to by
17380 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
17381 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
17382 getchar returns EOF. *
17386 <p><b>Synopsis</b>
17387 <p><!--para 1 -->
17388 <pre>
17390 int putc(int c, FILE *stream);
17391 </pre>
17392 <p><b>Description</b>
17393 <p><!--para 2 -->
17394 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
17395 may evaluate stream more than once, so that argument should never be an expression
17396 with side effects.
17397 <p><b>Returns</b>
17398 <p><!--para 3 -->
17399 The putc function returns the character written. If a write error occurs, the error
17400 indicator for the stream is set and putc returns EOF.
17404 <p><b>Synopsis</b>
17405 <p><!--para 1 -->
17406 <pre>
17408 int putchar(int c);
17409 </pre>
17410 <p><b>Description</b>
17411 <p><!--para 2 -->
17412 The putchar function is equivalent to putc with the second argument stdout.
17413 <!--page 351 -->
17414 <p><b>Returns</b>
17415 <p><!--para 3 -->
17416 The putchar function returns the character written. If a write error occurs, the error
17417 indicator for the stream is set and putchar returns EOF.
17421 <p><b>Synopsis</b>
17422 <p><!--para 1 -->
17423 <pre>
17425 int puts(const char *s);
17426 </pre>
17427 <p><b>Description</b>
17428 <p><!--para 2 -->
17429 The puts function writes the string pointed to by s to the stream pointed to by stdout,
17430 and appends a new-line character to the output. The terminating null character is not
17431 written.
17432 <p><b>Returns</b>
17433 <p><!--para 3 -->
17434 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
17435 value.
17439 <p><b>Synopsis</b>
17440 <p><!--para 1 -->
17441 <pre>
17443 int ungetc(int c, FILE *stream);
17444 </pre>
17445 <p><b>Description</b>
17446 <p><!--para 2 -->
17447 The ungetc function pushes the character specified by c (converted to an unsigned
17448 char) back onto the input stream pointed to by stream. Pushed-back characters will be
17449 returned by subsequent reads on that stream in the reverse order of their pushing. A
17450 successful intervening call (with the stream pointed to by stream) to a file positioning
17451 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
17452 stream. The external storage corresponding to the stream is unchanged.
17453 <p><!--para 3 -->
17454 One character of pushback is guaranteed. If the ungetc function is called too many
17455 times on the same stream without an intervening read or file positioning operation on that
17456 stream, the operation may fail.
17457 <p><!--para 4 -->
17458 If the value of c equals that of the macro EOF, the operation fails and the input stream is
17459 unchanged.
17460 <p><!--para 5 -->
17461 A successful call to the ungetc function clears the end-of-file indicator for the stream.
17462 The value of the file position indicator for the stream after reading or discarding all
17463 pushed-back characters shall be the same as it was before the characters were pushed
17464 back. For a text stream, the value of its file position indicator after a successful call to the
17465 ungetc function is unspecified until all pushed-back characters are read or discarded.
17466 <!--page 352 -->
17467 For a binary stream, its file position indicator is decremented by each successful call to
17468 the ungetc function; if its value was zero before a call, it is indeterminate after the
17470 <p><b>Returns</b>
17471 <p><!--para 6 -->
17472 The ungetc function returns the character pushed back after conversion, or EOF if the
17473 operation fails.
17476 <p><b>Footnotes</b>
17477 <p><small><a name="note283" href="#note283">283)</a> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
17478 </small>
17485 <p><b>Synopsis</b>
17486 <p><!--para 1 -->
17487 <pre>
17489 size_t fread(void * restrict ptr,
17490 size_t size, size_t nmemb,
17491 FILE * restrict stream);
17492 </pre>
17493 <p><b>Description</b>
17494 <p><!--para 2 -->
17495 The fread function reads, into the array pointed to by ptr, up to nmemb elements
17496 whose size is specified by size, from the stream pointed to by stream. For each
17497 object, size calls are made to the fgetc function and the results stored, in the order
17498 read, in an array of unsigned char exactly overlaying the object. The file position
17499 indicator for the stream (if defined) is advanced by the number of characters successfully
17500 read. If an error occurs, the resulting value of the file position indicator for the stream is
17501 indeterminate. If a partial element is read, its value is indeterminate.
17502 <p><b>Returns</b>
17503 <p><!--para 3 -->
17504 The fread function returns the number of elements successfully read, which may be
17505 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
17506 fread returns zero and the contents of the array and the state of the stream remain
17507 unchanged.
17512 <!--page 353 -->
17516 <p><b>Synopsis</b>
17517 <p><!--para 1 -->
17518 <pre>
17520 size_t fwrite(const void * restrict ptr,
17521 size_t size, size_t nmemb,
17522 FILE * restrict stream);
17523 </pre>
17524 <p><b>Description</b>
17525 <p><!--para 2 -->
17526 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
17527 whose size is specified by size, to the stream pointed to by stream. For each object,
17528 size calls are made to the fputc function, taking the values (in order) from an array of
17529 unsigned char exactly overlaying the object. The file position indicator for the
17530 stream (if defined) is advanced by the number of characters successfully written. If an
17531 error occurs, the resulting value of the file position indicator for the stream is
17532 indeterminate.
17533 <p><b>Returns</b>
17534 <p><!--para 3 -->
17535 The fwrite function returns the number of elements successfully written, which will be
17536 less than nmemb only if a write error is encountered. If size or nmemb is zero,
17537 fwrite returns zero and the state of the stream remains unchanged.
17544 <p><b>Synopsis</b>
17545 <p><!--para 1 -->
17546 <pre>
17548 int fgetpos(FILE * restrict stream,
17549 fpos_t * restrict pos);
17550 </pre>
17551 <p><b>Description</b>
17552 <p><!--para 2 -->
17553 The fgetpos function stores the current values of the parse state (if any) and file
17554 position indicator for the stream pointed to by stream in the object pointed to by pos.
17555 The values stored contain unspecified information usable by the fsetpos function for
17556 repositioning the stream to its position at the time of the call to the fgetpos function.
17557 <p><b>Returns</b>
17558 <p><!--para 3 -->
17559 If successful, the fgetpos function returns zero; on failure, the fgetpos function
17560 returns nonzero and stores an implementation-defined positive value in errno.
17562 <!--page 354 -->
17566 <p><b>Synopsis</b>
17567 <p><!--para 1 -->
17568 <pre>
17570 int fseek(FILE *stream, long int offset, int whence);
17571 </pre>
17572 <p><b>Description</b>
17573 <p><!--para 2 -->
17574 The fseek function sets the file position indicator for the stream pointed to by stream.
17575 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
17576 <p><!--para 3 -->
17577 For a binary stream, the new position, measured in characters from the beginning of the
17578 file, is obtained by adding offset to the position specified by whence. The specified
17579 position is the beginning of the file if whence is SEEK_SET, the current value of the file
17580 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
17581 meaningfully support fseek calls with a whence value of SEEK_END.
17582 <p><!--para 4 -->
17583 For a text stream, either offset shall be zero, or offset shall be a value returned by
17584 an earlier successful call to the ftell function on a stream associated with the same file
17585 and whence shall be SEEK_SET.
17586 <p><!--para 5 -->
17587 After determining the new position, a successful call to the fseek function undoes any
17588 effects of the ungetc function on the stream, clears the end-of-file indicator for the
17589 stream, and then establishes the new position. After a successful fseek call, the next
17590 operation on an update stream may be either input or output.
17591 <p><b>Returns</b>
17592 <p><!--para 6 -->
17593 The fseek function returns nonzero only for a request that cannot be satisfied.
17598 <p><b>Synopsis</b>
17599 <p><!--para 1 -->
17600 <pre>
17602 int fsetpos(FILE *stream, const fpos_t *pos);
17603 </pre>
17604 <p><b>Description</b>
17605 <p><!--para 2 -->
17606 The fsetpos function sets the mbstate_t object (if any) and file position indicator
17607 for the stream pointed to by stream according to the value of the object pointed to by
17608 pos, which shall be a value obtained from an earlier successful call to the fgetpos
17609 function on a stream associated with the same file. If a read or write error occurs, the
17610 error indicator for the stream is set and fsetpos fails.
17611 <p><!--para 3 -->
17612 A successful call to the fsetpos function undoes any effects of the ungetc function
17613 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
17614 parse state and position. After a successful fsetpos call, the next operation on an
17615 <!--page 355 -->
17616 update stream may be either input or output.
17617 <p><b>Returns</b>
17618 <p><!--para 4 -->
17619 If successful, the fsetpos function returns zero; on failure, the fsetpos function
17620 returns nonzero and stores an implementation-defined positive value in errno.
17624 <p><b>Synopsis</b>
17625 <p><!--para 1 -->
17626 <pre>
17628 long int ftell(FILE *stream);
17629 </pre>
17630 <p><b>Description</b>
17631 <p><!--para 2 -->
17632 The ftell function obtains the current value of the file position indicator for the stream
17633 pointed to by stream. For a binary stream, the value is the number of characters from
17634 the beginning of the file. For a text stream, its file position indicator contains unspecified
17635 information, usable by the fseek function for returning the file position indicator for the
17636 stream to its position at the time of the ftell call; the difference between two such
17637 return values is not necessarily a meaningful measure of the number of characters written
17638 or read.
17639 <p><b>Returns</b>
17640 <p><!--para 3 -->
17641 If successful, the ftell function returns the current value of the file position indicator
17642 for the stream. On failure, the ftell function returns -1L and stores an
17643 implementation-defined positive value in errno.
17647 <p><b>Synopsis</b>
17648 <p><!--para 1 -->
17649 <pre>
17651 void rewind(FILE *stream);
17652 </pre>
17653 <p><b>Description</b>
17654 <p><!--para 2 -->
17655 The rewind function sets the file position indicator for the stream pointed to by
17656 stream to the beginning of the file. It is equivalent to
17657 <pre>
17658 (void)fseek(stream, 0L, SEEK_SET)
17659 </pre>
17660 except that the error indicator for the stream is also cleared.
17661 <p><b>Returns</b>
17662 <p><!--para 3 -->
17663 The rewind function returns no value.
17664 <!--page 356 -->
17671 <p><b>Synopsis</b>
17672 <p><!--para 1 -->
17673 <pre>
17675 void clearerr(FILE *stream);
17676 </pre>
17677 <p><b>Description</b>
17678 <p><!--para 2 -->
17679 The clearerr function clears the end-of-file and error indicators for the stream pointed
17680 to by stream.
17681 <p><b>Returns</b>
17682 <p><!--para 3 -->
17683 The clearerr function returns no value.
17687 <p><b>Synopsis</b>
17688 <p><!--para 1 -->
17689 <pre>
17691 int feof(FILE *stream);
17692 </pre>
17693 <p><b>Description</b>
17694 <p><!--para 2 -->
17695 The feof function tests the end-of-file indicator for the stream pointed to by stream.
17696 <p><b>Returns</b>
17697 <p><!--para 3 -->
17698 The feof function returns nonzero if and only if the end-of-file indicator is set for
17699 stream.
17703 <p><b>Synopsis</b>
17704 <p><!--para 1 -->
17705 <pre>
17707 int ferror(FILE *stream);
17708 </pre>
17709 <p><b>Description</b>
17710 <p><!--para 2 -->
17711 The ferror function tests the error indicator for the stream pointed to by stream.
17712 <p><b>Returns</b>
17713 <p><!--para 3 -->
17714 The ferror function returns nonzero if and only if the error indicator is set for
17715 stream.
17716 <!--page 357 -->
17720 <p><b>Synopsis</b>
17721 <p><!--para 1 -->
17722 <pre>
17724 void perror(const char *s);
17725 </pre>
17726 <p><b>Description</b>
17727 <p><!--para 2 -->
17728 The perror function maps the error number in the integer expression errno to an
17729 error message. It writes a sequence of characters to the standard error stream thus: first
17730 (if s is not a null pointer and the character pointed to by s is not the null character), the
17731 string pointed to by s followed by a colon (:) and a space; then an appropriate error
17732 message string followed by a new-line character. The contents of the error message
17733 strings are the same as those returned by the strerror function with argument errno.
17734 <p><b>Returns</b>
17735 <p><!--para 3 -->
17736 The perror function returns no value.
17738 <!--page 358 -->
17742 <p><!--para 1 -->
17743 The header <a href="#7.22"><stdlib.h></a> declares five types and several functions of general utility, and
17745 <p><!--para 2 -->
17747 <pre>
17748 div_t
17749 </pre>
17750 which is a structure type that is the type of the value returned by the div function,
17751 <pre>
17752 ldiv_t
17753 </pre>
17754 which is a structure type that is the type of the value returned by the ldiv function, and
17755 <pre>
17756 lldiv_t
17757 </pre>
17758 which is a structure type that is the type of the value returned by the lldiv function.
17759 <p><!--para 3 -->
17761 <pre>
17762 EXIT_FAILURE
17763 </pre>
17764 and
17765 <pre>
17766 EXIT_SUCCESS
17767 </pre>
17768 which expand to integer constant expressions that can be used as the argument to the
17769 exit function to return unsuccessful or successful termination status, respectively, to the
17770 host environment;
17771 <pre>
17772 RAND_MAX
17773 </pre>
17774 which expands to an integer constant expression that is the maximum value returned by
17775 the rand function; and
17776 <pre>
17777 MB_CUR_MAX
17778 </pre>
17779 which expands to a positive integer expression with type size_t that is the maximum
17780 number of bytes in a multibyte character for the extended character set specified by the
17781 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
17786 <!--page 359 -->
17788 <p><b>Footnotes</b>
17789 <p><small><a name="note284" href="#note284">284)</a> See ''future library directions'' (<a href="#7.30.10">7.30.10</a>).
17790 </small>
17794 <p><!--para 1 -->
17795 The functions atof, atoi, atol, and atoll need not affect the value of the integer
17796 expression errno on an error. If the value of the result cannot be represented, the
17797 behavior is undefined.
17801 <p><b>Synopsis</b>
17802 <p><!--para 1 -->
17803 <pre>
17805 double atof(const char *nptr);
17806 </pre>
17807 <p><b>Description</b>
17808 <p><!--para 2 -->
17809 The atof function converts the initial portion of the string pointed to by nptr to
17810 double representation. Except for the behavior on error, it is equivalent to
17811 <pre>
17812 strtod(nptr, (char **)NULL)
17813 </pre>
17814 <p><b>Returns</b>
17815 <p><!--para 3 -->
17816 The atof function returns the converted value.
17817 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
17821 <p><b>Synopsis</b>
17822 <p><!--para 1 -->
17823 <pre>
17825 int atoi(const char *nptr);
17826 long int atol(const char *nptr);
17827 long long int atoll(const char *nptr);
17828 </pre>
17829 <p><b>Description</b>
17830 <p><!--para 2 -->
17831 The atoi, atol, and atoll functions convert the initial portion of the string pointed
17832 to by nptr to int, long int, and long long int representation, respectively.
17833 Except for the behavior on error, they are equivalent to
17834 <pre>
17835 atoi: (int)strtol(nptr, (char **)NULL, 10)
17836 atol: strtol(nptr, (char **)NULL, 10)
17837 atoll: strtoll(nptr, (char **)NULL, 10)
17838 </pre>
17839 <p><b>Returns</b>
17840 <p><!--para 3 -->
17841 The atoi, atol, and atoll functions return the converted value.
17842 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
17844 <!--page 360 -->
17847 <h5><a name="7.22.1.3" href="#7.22.1.3">7.22.1.3 The strtod, strtof, and strtold functions</a></h5>
17848 <p><b>Synopsis</b>
17849 <p><!--para 1 -->
17850 <pre>
17852 double strtod(const char * restrict nptr,
17853 char ** restrict endptr);
17854 float strtof(const char * restrict nptr,
17855 char ** restrict endptr);
17856 long double strtold(const char * restrict nptr,
17857 char ** restrict endptr);
17858 </pre>
17859 <p><b>Description</b>
17860 <p><!--para 2 -->
17861 The strtod, strtof, and strtold functions convert the initial portion of the string
17862 pointed to by nptr to double, float, and long double representation,
17863 respectively. First, they decompose the input string into three parts: an initial, possibly
17864 empty, sequence of white-space characters (as specified by the isspace function), a
17865 subject sequence resembling a floating-point constant or representing an infinity or NaN;
17866 and a final string of one or more unrecognized characters, including the terminating null
17867 character of the input string. Then, they attempt to convert the subject sequence to a
17868 floating-point number, and return the result.
17869 <p><!--para 3 -->
17870 The expected form of the subject sequence is an optional plus or minus sign, then one of
17871 the following:
17872 <ul>
17873 <li> a nonempty sequence of decimal digits optionally containing a decimal-point
17875 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
17876 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
17877 <li> INF or INFINITY, ignoring case
17878 <li> NAN or NAN(n-char-sequence<sub>opt</sub>), ignoring case in the NAN part, where:
17879 <pre>
17880 n-char-sequence:
17881 digit
17882 nondigit
17883 n-char-sequence digit
17884 n-char-sequence nondigit
17885 </pre>
17886 </ul>
17887 The subject sequence is defined as the longest initial subsequence of the input string,
17888 starting with the first non-white-space character, that is of the expected form. The subject
17889 sequence contains no characters if the input string is not of the expected form.
17890 <p><!--para 4 -->
17891 If the subject sequence has the expected form for a floating-point number, the sequence of
17892 characters starting with the first digit or the decimal-point character (whichever occurs
17893 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
17894 <!--page 361 -->
17895 decimal-point character is used in place of a period, and that if neither an exponent part
17896 nor a decimal-point character appears in a decimal floating point number, or if a binary
17897 exponent part does not appear in a hexadecimal floating point number, an exponent part
17898 of the appropriate type with value zero is assumed to follow the last digit in the string. If
17899 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note285"><b>285)</b></a></sup>
17900 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
17901 the return type, else like a floating constant that is too large for the range of the return
17902 type. A character sequence NAN or NAN(n-char-sequence<sub>opt</sub>), is interpreted as a quiet
17903 NaN, if supported in the return type, else like a subject sequence part that does not have
17904 the expected form; the meaning of the n-char sequences is implementation-defined.<sup><a href="#note286"><b>286)</b></a></sup> A
17905 pointer to the final string is stored in the object pointed to by endptr, provided that
17906 endptr is not a null pointer.
17907 <p><!--para 5 -->
17908 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
17909 value resulting from the conversion is correctly rounded.
17910 <p><!--para 6 -->
17912 accepted.
17913 <p><!--para 7 -->
17914 If the subject sequence is empty or does not have the expected form, no conversion is
17915 performed; the value of nptr is stored in the object pointed to by endptr, provided
17916 that endptr is not a null pointer.
17917 <p><b>Recommended practice</b>
17918 <p><!--para 8 -->
17919 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
17920 the result is not exactly representable, the result should be one of the two numbers in the
17921 appropriate internal format that are adjacent to the hexadecimal floating source value,
17922 with the extra stipulation that the error should have a correct sign for the current rounding
17923 direction.
17924 <p><!--para 9 -->
17925 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
17926 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
17927 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
17928 consider the two bounding, adjacent decimal strings L and U, both having
17929 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
17930 The result should be one of the (equal or adjacent) values that would be obtained by
17931 correctly rounding L and U according to the current rounding direction, with the extra
17933 <!--page 362 -->
17934 stipulation that the error with respect to D should have a correct sign for the current
17936 <p><b>Returns</b>
17937 <p><!--para 10 -->
17938 The functions return the converted value, if any. If no conversion could be performed,
17939 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
17940 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
17941 return type and sign of the value), and the value of the macro ERANGE is stored in
17942 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
17943 no greater than the smallest normalized positive number in the return type; whether
17944 errno acquires the value ERANGE is implementation-defined.
17946 <p><b>Footnotes</b>
17947 <p><small><a name="note285" href="#note285">285)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
17948 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
17949 methods may yield different results if rounding is toward positive or negative infinity. In either case,
17950 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
17951 </small>
17952 <p><small><a name="note286" href="#note286">286)</a> An implementation may use the n-char sequence to determine extra information to be represented in
17953 the NaN's significand.
17954 </small>
17955 <p><small><a name="note287" href="#note287">287)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
17956 to the same internal floating value, but if not will round to adjacent values.
17957 </small>
17960 <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>
17961 <p><b>Synopsis</b>
17962 <p><!--para 1 -->
17963 <pre>
17965 long int strtol(
17966 const char * restrict nptr,
17967 char ** restrict endptr,
17968 int base);
17969 long long int strtoll(
17970 const char * restrict nptr,
17971 char ** restrict endptr,
17972 int base);
17973 unsigned long int strtoul(
17974 const char * restrict nptr,
17975 char ** restrict endptr,
17976 int base);
17977 unsigned long long int strtoull(
17978 const char * restrict nptr,
17979 char ** restrict endptr,
17980 int base);
17981 </pre>
17982 <p><b>Description</b>
17983 <p><!--para 2 -->
17984 The strtol, strtoll, strtoul, and strtoull functions convert the initial
17985 portion of the string pointed to by nptr to long int, long long int, unsigned
17986 long int, and unsigned long long int representation, respectively. First,
17987 they decompose the input string into three parts: an initial, possibly empty, sequence of
17988 white-space characters (as specified by the isspace function), a subject sequence
17991 <!--page 363 -->
17992 resembling an integer represented in some radix determined by the value of base, and a
17993 final string of one or more unrecognized characters, including the terminating null
17994 character of the input string. Then, they attempt to convert the subject sequence to an
17995 integer, and return the result.
17996 <p><!--para 3 -->
17997 If the value of base is zero, the expected form of the subject sequence is that of an
17998 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
17999 not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
18000 expected form of the subject sequence is a sequence of letters and digits representing an
18001 integer with the radix specified by base, optionally preceded by a plus or minus sign,
18002 but not including an integer suffix. The letters from a (or A) through z (or Z) are
18003 ascribed the values 10 through 35; only letters and digits whose ascribed values are less
18004 than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
18005 optionally precede the sequence of letters and digits, following the sign if present.
18006 <p><!--para 4 -->
18007 The subject sequence is defined as the longest initial subsequence of the input string,
18008 starting with the first non-white-space character, that is of the expected form. The subject
18009 sequence contains no characters if the input string is empty or consists entirely of white
18010 space, or if the first non-white-space character is other than a sign or a permissible letter
18011 or digit.
18012 <p><!--para 5 -->
18013 If the subject sequence has the expected form and the value of base is zero, the sequence
18014 of characters starting with the first digit is interpreted as an integer constant according to
18015 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
18016 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
18017 as given above. If the subject sequence begins with a minus sign, the value resulting from
18018 the conversion is negated (in the return type). A pointer to the final string is stored in the
18019 object pointed to by endptr, provided that endptr is not a null pointer.
18020 <p><!--para 6 -->
18022 accepted.
18023 <p><!--para 7 -->
18024 If the subject sequence is empty or does not have the expected form, no conversion is
18025 performed; the value of nptr is stored in the object pointed to by endptr, provided
18026 that endptr is not a null pointer.
18027 <p><b>Returns</b>
18028 <p><!--para 8 -->
18029 The strtol, strtoll, strtoul, and strtoull functions return the converted
18030 value, if any. If no conversion could be performed, zero is returned. If the correct value
18031 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
18032 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
18033 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
18034 <!--page 364 -->
18037 <h4><a name="7.22.2" href="#7.22.2">7.22.2 Pseudo-random sequence generation functions</a></h4>
18041 <p><b>Synopsis</b>
18042 <p><!--para 1 -->
18043 <pre>
18045 int rand(void);
18046 </pre>
18047 <p><b>Description</b>
18048 <p><!--para 2 -->
18049 The rand function computes a sequence of pseudo-random integers in the range 0 to
18051 <p><!--para 3 -->
18052 The rand function is not required to avoid data races. The implementation shall behave
18053 as if no library function calls the rand function.
18054 <p><b>Returns</b>
18055 <p><!--para 4 -->
18056 The rand function returns a pseudo-random integer.
18057 <p><b>Environmental limits</b>
18058 <p><!--para 5 -->
18059 The value of the RAND_MAX macro shall be at least 32767.
18061 <p><b>Footnotes</b>
18062 <p><small><a name="note288" href="#note288">288)</a> There are no guarantees as to the quality of the random sequence produced and some implementations
18063 are known to produce sequences with distressingly non-random low-order bits. Applications with
18064 particular requirements should use a generator that is known to be sufficient for their needs.
18065 </small>
18069 <p><b>Synopsis</b>
18070 <p><!--para 1 -->
18071 <pre>
18073 void srand(unsigned int seed);
18074 </pre>
18075 <p><b>Description</b>
18076 <p><!--para 2 -->
18077 The srand function uses the argument as a seed for a new sequence of pseudo-random
18078 numbers to be returned by subsequent calls to rand. If srand is then called with the
18079 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
18080 called before any calls to srand have been made, the same sequence shall be generated
18081 as when srand is first called with a seed value of 1.
18082 <p><!--para 3 -->
18083 The implementation shall behave as if no library function calls the srand function.
18084 <p><b>Returns</b>
18085 <p><!--para 4 -->
18086 The srand function returns no value.
18091 <!--page 365 -->
18092 <p><!--para 5 -->
18093 EXAMPLE The following functions define a portable implementation of rand and srand.
18094 <pre>
18095 static unsigned long int next = 1;
18096 int rand(void) // RAND_MAX assumed to be 32767
18097 {
18098 next = next * 1103515245 + 12345;
18099 return (unsigned int)(next/65536) % 32768;
18100 }
18101 void srand(unsigned int seed)
18102 {
18103 next = seed;
18104 }
18105 </pre>
18110 <p><!--para 1 -->
18111 The order and contiguity of storage allocated by successive calls to the
18112 aligned_alloc, calloc, malloc, and realloc functions is unspecified. The
18113 pointer returned if the allocation succeeds is suitably aligned so that it may be assigned to
18114 a pointer to any type of object with a fundamental alignment requirement and then used
18115 to access such an object or an array of such objects in the space allocated (until the space
18116 is explicitly deallocated). The lifetime of an allocated object extends from the allocation
18117 until the deallocation. Each such allocation shall yield a pointer to an object disjoint from
18118 any other object. The pointer returned points to the start (lowest byte address) of the
18119 allocated space. If the space cannot be allocated, a null pointer is returned. If the size of
18120 the space requested is zero, the behavior is implementation-defined: either a null pointer
18121 is returned, or the behavior is as if the size were some nonzero value, except that the
18122 returned pointer shall not be used to access an object.
18126 <p><b>Synopsis</b>
18127 <p><!--para 1 -->
18128 <pre>
18130 void *aligned_alloc(size_t alignment, size_t size);
18131 </pre>
18132 <p><b>Description</b>
18133 <p><!--para 2 -->
18134 The aligned_alloc function allocates space for an object whose alignment is
18135 specified by alignment, whose size is specified by size, and whose value is
18136 indeterminate. The value of alignment shall be a valid alignment supported by the
18137 implementation and the value of size shall be an integral multiple of alignment.
18138 <p><b>Returns</b>
18139 <p><!--para 3 -->
18140 The aligned_alloc function returns either a null pointer or a pointer to the allocated
18141 space.
18142 <!--page 366 -->
18146 <p><b>Synopsis</b>
18147 <p><!--para 1 -->
18148 <pre>
18150 void *calloc(size_t nmemb, size_t size);
18151 </pre>
18152 <p><b>Description</b>
18153 <p><!--para 2 -->
18154 The calloc function allocates space for an array of nmemb objects, each of whose size
18155 is size. The space is initialized to all bits zero.<sup><a href="#note289"><b>289)</b></a></sup>
18156 <p><b>Returns</b>
18157 <p><!--para 3 -->
18158 The calloc function returns either a null pointer or a pointer to the allocated space.
18160 <p><b>Footnotes</b>
18161 <p><small><a name="note289" href="#note289">289)</a> Note that this need not be the same as the representation of floating-point zero or a null pointer
18162 constant.
18163 </small>
18167 <p><b>Synopsis</b>
18168 <p><!--para 1 -->
18169 <pre>
18171 void free(void *ptr);
18172 </pre>
18173 <p><b>Description</b>
18174 <p><!--para 2 -->
18175 The free function causes the space pointed to by ptr to be deallocated, that is, made
18176 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
18177 the argument does not match a pointer earlier returned by a memory management
18178 function, or if the space has been deallocated by a call to free or realloc, the
18179 behavior is undefined.
18180 <p><b>Returns</b>
18181 <p><!--para 3 -->
18182 The free function returns no value.
18186 <p><b>Synopsis</b>
18187 <p><!--para 1 -->
18188 <pre>
18190 void *malloc(size_t size);
18191 </pre>
18192 <p><b>Description</b>
18193 <p><!--para 2 -->
18194 The malloc function allocates space for an object whose size is specified by size and
18195 whose value is indeterminate.
18200 <!--page 367 -->
18201 <p><b>Returns</b>
18202 <p><!--para 3 -->
18203 The malloc function returns either a null pointer or a pointer to the allocated space.
18207 <p><b>Synopsis</b>
18208 <p><!--para 1 -->
18209 <pre>
18211 void *realloc(void *ptr, size_t size);
18212 </pre>
18213 <p><b>Description</b>
18214 <p><!--para 2 -->
18215 The realloc function deallocates the old object pointed to by ptr and returns a
18216 pointer to a new object that has the size specified by size. The contents of the new
18217 object shall be the same as that of the old object prior to deallocation, up to the lesser of
18218 the new and old sizes. Any bytes in the new object beyond the size of the old object have
18219 indeterminate values.
18220 <p><!--para 3 -->
18221 If ptr is a null pointer, the realloc function behaves like the malloc function for the
18222 specified size. Otherwise, if ptr does not match a pointer earlier returned by a memory
18223 management function, or if the space has been deallocated by a call to the free or
18224 realloc function, the behavior is undefined. If memory for the new object cannot be
18225 allocated, the old object is not deallocated and its value is unchanged.
18226 <p><b>Returns</b>
18227 <p><!--para 4 -->
18228 The realloc function returns a pointer to the new object (which may have the same
18229 value as a pointer to the old object), or a null pointer if the new object could not be
18230 allocated.
18237 <p><b>Synopsis</b>
18238 <p><!--para 1 -->
18239 <pre>
18241 _Noreturn void abort(void);
18242 </pre>
18243 <p><b>Description</b>
18244 <p><!--para 2 -->
18245 The abort function causes abnormal program termination to occur, unless the signal
18246 SIGABRT is being caught and the signal handler does not return. Whether open streams
18247 with unwritten buffered data are flushed, open streams are closed, or temporary files are
18248 removed is implementation-defined. An implementation-defined form of the status
18249 unsuccessful termination is returned to the host environment by means of the function
18250 call raise(SIGABRT).
18251 <!--page 368 -->
18252 <p><b>Returns</b>
18253 <p><!--para 3 -->
18254 The abort function does not return to its caller.
18258 <p><b>Synopsis</b>
18259 <p><!--para 1 -->
18260 <pre>
18262 int atexit(void (*func)(void));
18263 </pre>
18264 <p><b>Description</b>
18265 <p><!--para 2 -->
18266 The atexit function registers the function pointed to by func, to be called without
18268 <p><b>Environmental limits</b>
18269 <p><!--para 3 -->
18270 The implementation shall support the registration of at least 32 functions.
18271 <p><b>Returns</b>
18272 <p><!--para 4 -->
18273 The atexit function returns zero if the registration succeeds, nonzero if it fails.
18274 <p><b> Forward references</b>: the at_quick_exit function (<a href="#7.22.4.3">7.22.4.3</a>), the exit function
18277 <p><b>Footnotes</b>
18278 <p><small><a name="note290" href="#note290">290)</a> The atexit function registrations are distinct from the at_quick_exit registrations, so
18279 applications may need to call both registration functions with the same argument.
18280 </small>
18284 <p><b>Synopsis</b>
18285 <p><!--para 1 -->
18286 <pre>
18288 int at_quick_exit(void (*func)(void));
18289 </pre>
18290 <p><b>Description</b>
18291 <p><!--para 2 -->
18292 The at_quick_exit function registers the function pointed to by func, to be called
18294 <p><b>Environmental limits</b>
18295 <p><!--para 3 -->
18296 The implementation shall support the registration of at least 32 functions.
18297 <p><b>Returns</b>
18298 <p><!--para 4 -->
18299 The at_quick_exit function returns zero if the registration succeeds, nonzero if it
18300 fails.
18304 <!--page 369 -->
18306 <p><b>Footnotes</b>
18307 <p><small><a name="note291" href="#note291">291)</a> The at_quick_exit function registrations are distinct from the atexit registrations, so
18308 applications may need to call both registration functions with the same argument.
18309 </small>
18313 <p><b>Synopsis</b>
18314 <p><!--para 1 -->
18315 <pre>
18317 _Noreturn void exit(int status);
18318 </pre>
18319 <p><b>Description</b>
18320 <p><!--para 2 -->
18321 The exit function causes normal program termination to occur. No functions registered
18322 by the at_quick_exit function are called. If a program calls the exit function
18323 more than once, or calls the quick_exit function in addition to the exit function, the
18324 behavior is undefined.
18325 <p><!--para 3 -->
18326 First, all functions registered by the atexit function are called, in the reverse order of
18327 their registration,<sup><a href="#note292"><b>292)</b></a></sup> except that a function is called after any previously registered
18328 functions that had already been called at the time it was registered. If, during the call to
18329 any such function, a call to the longjmp function is made that would terminate the call
18330 to the registered function, the behavior is undefined.
18331 <p><!--para 4 -->
18332 Next, all open streams with unwritten buffered data are flushed, all open streams are
18333 closed, and all files created by the tmpfile function are removed.
18334 <p><!--para 5 -->
18335 Finally, control is returned to the host environment. If the value of status is zero or
18336 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
18337 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
18338 of the status unsuccessful termination is returned. Otherwise the status returned is
18339 implementation-defined.
18340 <p><b>Returns</b>
18341 <p><!--para 6 -->
18342 The exit function cannot return to its caller.
18344 <p><b>Footnotes</b>
18345 <p><small><a name="note292" href="#note292">292)</a> Each function is called as many times as it was registered, and in the correct order with respect to
18346 other registered functions.
18347 </small>
18351 <p><b>Synopsis</b>
18352 <p><!--para 1 -->
18353 <pre>
18355 _Noreturn void _Exit(int status);
18356 </pre>
18357 <p><b>Description</b>
18358 <p><!--para 2 -->
18359 The _Exit function causes normal program termination to occur and control to be
18360 returned to the host environment. No functions registered by the atexit function, the
18361 at_quick_exit function, or signal handlers registered by the signal function are
18362 called. The status returned to the host environment is determined in the same way as for
18365 <!--page 370 -->
18366 the exit function (<a href="#7.22.4.4">7.22.4.4</a>). Whether open streams with unwritten buffered data are
18367 flushed, open streams are closed, or temporary files are removed is implementation-
18368 defined.
18369 <p><b>Returns</b>
18370 <p><!--para 3 -->
18371 The _Exit function cannot return to its caller.
18375 <p><b>Synopsis</b>
18376 <p><!--para 1 -->
18377 <pre>
18379 char *getenv(const char *name);
18380 </pre>
18381 <p><b>Description</b>
18382 <p><!--para 2 -->
18383 The getenv function searches an environment list, provided by the host environment,
18384 for a string that matches the string pointed to by name. The set of environment names
18385 and the method for altering the environment list are implementation-defined. The
18386 getenv function need not avoid data races with other threads of execution that modify
18388 <p><!--para 3 -->
18389 The implementation shall behave as if no library function calls the getenv function.
18390 <p><b>Returns</b>
18391 <p><!--para 4 -->
18392 The getenv function returns a pointer to a string associated with the matched list
18393 member. The string pointed to shall not be modified by the program, but may be
18394 overwritten by a subsequent call to the getenv function. If the specified name cannot
18395 be found, a null pointer is returned.
18397 <p><b>Footnotes</b>
18398 <p><small><a name="note293" href="#note293">293)</a> Many implementations provide non-standard functions that modify the environment list.
18399 </small>
18403 <p><b>Synopsis</b>
18404 <p><!--para 1 -->
18405 <pre>
18407 _Noreturn void quick_exit(int status);
18408 </pre>
18409 <p><b>Description</b>
18410 <p><!--para 2 -->
18411 The quick_exit function causes normal program termination to occur. No functions
18412 registered by the atexit function or signal handlers registered by the signal function
18413 are called. If a program calls the quick_exit function more than once, or calls the
18414 exit function in addition to the quick_exit function, the behavior is undefined.
18415 <p><!--para 3 -->
18416 The quick_exit function first calls all functions registered by the at_quick_exit
18417 function, in the reverse order of their registration,<sup><a href="#note294"><b>294)</b></a></sup> except that a function is called after
18420 <!--page 371 -->
18421 any previously registered functions that had already been called at the time it was
18422 registered. If, during the call to any such function, a call to the longjmp function is
18423 made that would terminate the call to the registered function, the behavior is undefined.
18424 <p><!--para 4 -->
18425 Then control is returned to the host environment by means of the function call
18426 _Exit(status).
18427 <p><b>Returns</b>
18428 <p><!--para 5 -->
18429 The quick_exit function cannot return to its caller.
18431 <p><b>Footnotes</b>
18432 <p><small><a name="note294" href="#note294">294)</a> Each function is called as many times as it was registered, and in the correct order with respect to
18433 other registered functions.
18434 </small>
18438 <p><b>Synopsis</b>
18439 <p><!--para 1 -->
18440 <pre>
18442 int system(const char *string);
18443 </pre>
18444 <p><b>Description</b>
18445 <p><!--para 2 -->
18446 If string is a null pointer, the system function determines whether the host
18447 environment has a command processor. If string is not a null pointer, the system
18448 function passes the string pointed to by string to that command processor to be
18449 executed in a manner which the implementation shall document; this might then cause the
18450 program calling system to behave in a non-conforming manner or to terminate.
18451 <p><b>Returns</b>
18452 <p><!--para 3 -->
18453 If the argument is a null pointer, the system function returns nonzero only if a
18454 command processor is available. If the argument is not a null pointer, and the system
18455 function does return, it returns an implementation-defined value.
18459 <p><!--para 1 -->
18460 These utilities make use of a comparison function to search or sort arrays of unspecified
18461 type. Where an argument declared as size_t nmemb specifies the length of the array
18462 for a function, nmemb can have the value zero on a call to that function; the comparison
18463 function is not called, a search finds no matching element, and sorting performs no
18464 rearrangement. Pointer arguments on such a call shall still have valid values, as described
18466 <p><!--para 2 -->
18467 The implementation shall ensure that the second argument of the comparison function
18468 (when called from bsearch), or both arguments (when called from qsort), are
18469 pointers to elements of the array.<sup><a href="#note295"><b>295)</b></a></sup> The first argument when called from bsearch
18470 shall equal key.
18474 <!--page 372 -->
18475 <p><!--para 3 -->
18476 The comparison function shall not alter the contents of the array. The implementation
18477 may reorder elements of the array between calls to the comparison function, but shall not
18478 alter the contents of any individual element.
18479 <p><!--para 4 -->
18480 When the same objects (consisting of size bytes, irrespective of their current positions
18481 in the array) are passed more than once to the comparison function, the results shall be
18482 consistent with one another. That is, for qsort they shall define a total ordering on the
18483 array, and for bsearch the same object shall always compare the same way with the
18484 key.
18485 <p><!--para 5 -->
18486 A sequence point occurs immediately before and immediately after each call to the
18487 comparison function, and also between any call to the comparison function and any
18488 movement of the objects passed as arguments to that call.
18490 <p><b>Footnotes</b>
18491 <p><small><a name="note295" href="#note295">295)</a> That is, if the value passed is p, then the following expressions are always nonzero:
18493 <pre>
18494 ((char *)p - (char *)base) % size == 0
18495 (char *)p >= (char *)base
18496 (char *)p < (char *)base + nmemb * size
18497 </pre>
18499 </small>
18503 <p><b>Synopsis</b>
18504 <p><!--para 1 -->
18505 <pre>
18507 void *bsearch(const void *key, const void *base,
18508 size_t nmemb, size_t size,
18509 int (*compar)(const void *, const void *));
18510 </pre>
18511 <p><b>Description</b>
18512 <p><!--para 2 -->
18513 The bsearch function searches an array of nmemb objects, the initial element of which
18514 is pointed to by base, for an element that matches the object pointed to by key. The
18515 size of each element of the array is specified by size.
18516 <p><!--para 3 -->
18517 The comparison function pointed to by compar is called with two arguments that point
18518 to the key object and to an array element, in that order. The function shall return an
18519 integer less than, equal to, or greater than zero if the key object is considered,
18520 respectively, to be less than, to match, or to be greater than the array element. The array
18521 shall consist of: all the elements that compare less than, all the elements that compare
18522 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note296"><b>296)</b></a></sup>
18523 <p><b>Returns</b>
18524 <p><!--para 4 -->
18525 The bsearch function returns a pointer to a matching element of the array, or a null
18526 pointer if no match is found. If two elements compare as equal, which element is
18529 <!--page 373 -->
18530 matched is unspecified.
18532 <p><b>Footnotes</b>
18533 <p><small><a name="note296" href="#note296">296)</a> In practice, the entire array is sorted according to the comparison function.
18534 </small>
18538 <p><b>Synopsis</b>
18539 <p><!--para 1 -->
18540 <pre>
18542 void qsort(void *base, size_t nmemb, size_t size,
18543 int (*compar)(const void *, const void *));
18544 </pre>
18545 <p><b>Description</b>
18546 <p><!--para 2 -->
18547 The qsort function sorts an array of nmemb objects, the initial element of which is
18548 pointed to by base. The size of each object is specified by size.
18549 <p><!--para 3 -->
18550 The contents of the array are sorted into ascending order according to a comparison
18551 function pointed to by compar, which is called with two arguments that point to the
18552 objects being compared. The function shall return an integer less than, equal to, or
18553 greater than zero if the first argument is considered to be respectively less than, equal to,
18554 or greater than the second.
18555 <p><!--para 4 -->
18556 If two elements compare as equal, their order in the resulting sorted array is unspecified.
18557 <p><b>Returns</b>
18558 <p><!--para 5 -->
18559 The qsort function returns no value.
18566 <p><b>Synopsis</b>
18567 <p><!--para 1 -->
18568 <pre>
18570 int abs(int j);
18571 long int labs(long int j);
18572 long long int llabs(long long int j);
18573 </pre>
18574 <p><b>Description</b>
18575 <p><!--para 2 -->
18576 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
18577 result cannot be represented, the behavior is undefined.<sup><a href="#note297"><b>297)</b></a></sup>
18578 <p><b>Returns</b>
18579 <p><!--para 3 -->
18580 The abs, labs, and llabs, functions return the absolute value.
18585 <!--page 374 -->
18587 <p><b>Footnotes</b>
18588 <p><small><a name="note297" href="#note297">297)</a> The absolute value of the most negative number cannot be represented in two's complement.
18589 </small>
18593 <p><b>Synopsis</b>
18594 <p><!--para 1 -->
18595 <pre>
18597 div_t div(int numer, int denom);
18598 ldiv_t ldiv(long int numer, long int denom);
18599 lldiv_t lldiv(long long int numer, long long int denom);
18600 </pre>
18601 <p><b>Description</b>
18602 <p><!--para 2 -->
18603 The div, ldiv, and lldiv, functions compute numer / denom and numer %
18604 denom in a single operation.
18605 <p><b>Returns</b>
18606 <p><!--para 3 -->
18607 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
18608 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
18609 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
18610 each of which has the same type as the arguments numer and denom. If either part of
18611 the result cannot be represented, the behavior is undefined.
18614 <h4><a name="7.22.7" href="#7.22.7">7.22.7 Multibyte/wide character conversion functions</a></h4>
18615 <p><!--para 1 -->
18616 The behavior of the multibyte character functions is affected by the LC_CTYPE category
18617 of the current locale. For a state-dependent encoding, each function is placed into its
18618 initial conversion state at program startup and can be returned to that state by a call for
18619 which its character pointer argument, s, is a null pointer. Subsequent calls with s as
18620 other than a null pointer cause the internal conversion state of the function to be altered as
18621 necessary. A call with s as a null pointer causes these functions to return a nonzero value
18622 if encodings have state dependency, and zero otherwise.<sup><a href="#note298"><b>298)</b></a></sup> Changing the LC_CTYPE
18623 category causes the conversion state of these functions to be indeterminate.
18625 <p><b>Footnotes</b>
18626 <p><small><a name="note298" href="#note298">298)</a> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
18627 character codes, but are grouped with an adjacent multibyte character.
18628 </small>
18632 <p><b>Synopsis</b>
18633 <p><!--para 1 -->
18634 <pre>
18636 int mblen(const char *s, size_t n);
18637 </pre>
18638 <p><b>Description</b>
18639 <p><!--para 2 -->
18640 If s is not a null pointer, the mblen function determines the number of bytes contained
18641 in the multibyte character pointed to by s. Except that the conversion state of the
18642 mbtowc function is not affected, it is equivalent to
18646 <!--page 375 -->
18647 <pre>
18648 mbtowc((wchar_t *)0, (const char *)0, 0);
18649 mbtowc((wchar_t *)0, s, n);
18650 </pre>
18651 <p><!--para 3 -->
18652 The implementation shall behave as if no library function calls the mblen function.
18653 <p><b>Returns</b>
18654 <p><!--para 4 -->
18655 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
18656 character encodings, respectively, do or do not have state-dependent encodings. If s is
18657 not a null pointer, the mblen function either returns 0 (if s points to the null character),
18658 or returns the number of bytes that are contained in the multibyte character (if the next n
18659 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
18660 multibyte character).
18665 <p><b>Synopsis</b>
18666 <p><!--para 1 -->
18667 <pre>
18669 int mbtowc(wchar_t * restrict pwc,
18670 const char * restrict s,
18671 size_t n);
18672 </pre>
18673 <p><b>Description</b>
18674 <p><!--para 2 -->
18675 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
18676 the byte pointed to by s to determine the number of bytes needed to complete the next
18677 multibyte character (including any shift sequences). If the function determines that the
18678 next multibyte character is complete and valid, it determines the value of the
18679 corresponding wide character and then, if pwc is not a null pointer, stores that value in
18680 the object pointed to by pwc. If the corresponding wide character is the null wide
18681 character, the function is left in the initial conversion state.
18682 <p><!--para 3 -->
18683 The implementation shall behave as if no library function calls the mbtowc function.
18684 <p><b>Returns</b>
18685 <p><!--para 4 -->
18686 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
18687 character encodings, respectively, do or do not have state-dependent encodings. If s is
18688 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
18689 or returns the number of bytes that are contained in the converted multibyte character (if
18690 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
18691 form a valid multibyte character).
18692 <p><!--para 5 -->
18693 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
18694 macro.
18695 <!--page 376 -->
18699 <p><b>Synopsis</b>
18700 <p><!--para 1 -->
18701 <pre>
18703 int wctomb(char *s, wchar_t wc);
18704 </pre>
18705 <p><b>Description</b>
18706 <p><!--para 2 -->
18707 The wctomb function determines the number of bytes needed to represent the multibyte
18708 character corresponding to the wide character given by wc (including any shift
18709 sequences), and stores the multibyte character representation in the array whose first
18710 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
18711 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
18712 sequence needed to restore the initial shift state, and the function is left in the initial
18713 conversion state.
18714 <p><!--para 3 -->
18715 The implementation shall behave as if no library function calls the wctomb function.
18716 <p><b>Returns</b>
18717 <p><!--para 4 -->
18718 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
18719 character encodings, respectively, do or do not have state-dependent encodings. If s is
18720 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
18721 to a valid multibyte character, or returns the number of bytes that are contained in the
18722 multibyte character corresponding to the value of wc.
18723 <p><!--para 5 -->
18724 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
18727 <h4><a name="7.22.8" href="#7.22.8">7.22.8 Multibyte/wide string conversion functions</a></h4>
18728 <p><!--para 1 -->
18729 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
18730 the current locale.
18734 <p><b>Synopsis</b>
18735 <p><!--para 1 -->
18736 <pre>
18738 size_t mbstowcs(wchar_t * restrict pwcs,
18739 const char * restrict s,
18740 size_t n);
18741 </pre>
18742 <p><b>Description</b>
18743 <p><!--para 2 -->
18744 The mbstowcs function converts a sequence of multibyte characters that begins in the
18745 initial shift state from the array pointed to by s into a sequence of corresponding wide
18746 characters and stores not more than n wide characters into the array pointed to by pwcs.
18747 No multibyte characters that follow a null character (which is converted into a null wide
18748 character) will be examined or converted. Each multibyte character is converted as if by
18749 a call to the mbtowc function, except that the conversion state of the mbtowc function is
18750 <!--page 377 -->
18751 not affected.
18752 <p><!--para 3 -->
18753 No more than n elements will be modified in the array pointed to by pwcs. If copying
18754 takes place between objects that overlap, the behavior is undefined.
18755 <p><b>Returns</b>
18756 <p><!--para 4 -->
18757 If an invalid multibyte character is encountered, the mbstowcs function returns
18758 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
18759 elements modified, not including a terminating null wide character, if any.<sup><a href="#note299"><b>299)</b></a></sup>
18761 <p><b>Footnotes</b>
18762 <p><small><a name="note299" href="#note299">299)</a> The array will not be null-terminated if the value returned is n.
18763 </small>
18767 <p><b>Synopsis</b>
18768 <p><!--para 1 -->
18769 <pre>
18771 size_t wcstombs(char * restrict s,
18772 const wchar_t * restrict pwcs,
18773 size_t n);
18774 </pre>
18775 <p><b>Description</b>
18776 <p><!--para 2 -->
18777 The wcstombs function converts a sequence of wide characters from the array pointed
18778 to by pwcs into a sequence of corresponding multibyte characters that begins in the
18779 initial shift state, and stores these multibyte characters into the array pointed to by s,
18780 stopping if a multibyte character would exceed the limit of n total bytes or if a null
18781 character is stored. Each wide character is converted as if by a call to the wctomb
18782 function, except that the conversion state of the wctomb function is not affected.
18783 <p><!--para 3 -->
18784 No more than n bytes will be modified in the array pointed to by s. If copying takes place
18785 between objects that overlap, the behavior is undefined.
18786 <p><b>Returns</b>
18787 <p><!--para 4 -->
18788 If a wide character is encountered that does not correspond to a valid multibyte character,
18789 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
18790 returns the number of bytes modified, not including a terminating null character, if
18796 <!--page 378 -->
18803 <p><!--para 1 -->
18804 The header <a href="#7.23"><string.h></a> declares one type and several functions, and defines one
18805 macro useful for manipulating arrays of character type and other objects treated as arrays
18806 of character type.<sup><a href="#note300"><b>300)</b></a></sup> The type is size_t and the macro is NULL (both described in
18807 <a href="#7.19">7.19</a>). Various methods are used for determining the lengths of the arrays, but in all cases
18808 a char * or void * argument points to the initial (lowest addressed) character of the
18809 array. If an array is accessed beyond the end of an object, the behavior is undefined.
18810 <p><!--para 2 -->
18811 Where an argument declared as size_t n specifies the length of the array for a
18812 function, n can have the value zero on a call to that function. Unless explicitly stated
18813 otherwise in the description of a particular function in this subclause, pointer arguments
18814 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
18815 function that locates a character finds no occurrence, a function that compares two
18816 character sequences returns zero, and a function that copies characters copies zero
18817 characters.
18818 <p><!--para 3 -->
18819 For all functions in this subclause, each character shall be interpreted as if it had the type
18820 unsigned char (and therefore every possible object representation is valid and has a
18821 different value).
18823 <p><b>Footnotes</b>
18824 <p><small><a name="note300" href="#note300">300)</a> See ''future library directions'' (<a href="#7.30.11">7.30.11</a>).
18825 </small>
18832 <p><b>Synopsis</b>
18833 <p><!--para 1 -->
18834 <pre>
18836 void *memcpy(void * restrict s1,
18837 const void * restrict s2,
18838 size_t n);
18839 </pre>
18840 <p><b>Description</b>
18841 <p><!--para 2 -->
18842 The memcpy function copies n characters from the object pointed to by s2 into the
18843 object pointed to by s1. If copying takes place between objects that overlap, the behavior
18844 is undefined.
18845 <p><b>Returns</b>
18846 <p><!--para 3 -->
18847 The memcpy function returns the value of s1.
18852 <!--page 379 -->
18856 <p><b>Synopsis</b>
18857 <p><!--para 1 -->
18858 <pre>
18860 void *memmove(void *s1, const void *s2, size_t n);
18861 </pre>
18862 <p><b>Description</b>
18863 <p><!--para 2 -->
18864 The memmove function copies n characters from the object pointed to by s2 into the
18865 object pointed to by s1. Copying takes place as if the n characters from the object
18866 pointed to by s2 are first copied into a temporary array of n characters that does not
18867 overlap the objects pointed to by s1 and s2, and then the n characters from the
18868 temporary array are copied into the object pointed to by s1.
18869 <p><b>Returns</b>
18870 <p><!--para 3 -->
18871 The memmove function returns the value of s1.
18875 <p><b>Synopsis</b>
18876 <p><!--para 1 -->
18877 <pre>
18879 char *strcpy(char * restrict s1,
18880 const char * restrict s2);
18881 </pre>
18882 <p><b>Description</b>
18883 <p><!--para 2 -->
18884 The strcpy function copies the string pointed to by s2 (including the terminating null
18885 character) into the array pointed to by s1. If copying takes place between objects that
18886 overlap, the behavior is undefined.
18887 <p><b>Returns</b>
18888 <p><!--para 3 -->
18889 The strcpy function returns the value of s1.
18893 <p><b>Synopsis</b>
18894 <p><!--para 1 -->
18895 <pre>
18897 char *strncpy(char * restrict s1,
18898 const char * restrict s2,
18899 size_t n);
18900 </pre>
18901 <p><b>Description</b>
18902 <p><!--para 2 -->
18903 The strncpy function copies not more than n characters (characters that follow a null
18904 character are not copied) from the array pointed to by s2 to the array pointed to by
18905 <!--page 380 -->
18906 s1.<sup><a href="#note301"><b>301)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
18907 <p><!--para 3 -->
18908 If the array pointed to by s2 is a string that is shorter than n characters, null characters
18909 are appended to the copy in the array pointed to by s1, until n characters in all have been
18910 written.
18911 <p><b>Returns</b>
18912 <p><!--para 4 -->
18913 The strncpy function returns the value of s1.
18915 <p><b>Footnotes</b>
18916 <p><small><a name="note301" href="#note301">301)</a> Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
18917 not be null-terminated.
18918 </small>
18925 <p><b>Synopsis</b>
18926 <p><!--para 1 -->
18927 <pre>
18929 char *strcat(char * restrict s1,
18930 const char * restrict s2);
18931 </pre>
18932 <p><b>Description</b>
18933 <p><!--para 2 -->
18934 The strcat function appends a copy of the string pointed to by s2 (including the
18935 terminating null character) to the end of the string pointed to by s1. The initial character
18936 of s2 overwrites the null character at the end of s1. If copying takes place between
18937 objects that overlap, the behavior is undefined.
18938 <p><b>Returns</b>
18939 <p><!--para 3 -->
18940 The strcat function returns the value of s1.
18944 <p><b>Synopsis</b>
18945 <p><!--para 1 -->
18946 <pre>
18948 char *strncat(char * restrict s1,
18949 const char * restrict s2,
18950 size_t n);
18951 </pre>
18952 <p><b>Description</b>
18953 <p><!--para 2 -->
18954 The strncat function appends not more than n characters (a null character and
18955 characters that follow it are not appended) from the array pointed to by s2 to the end of
18956 the string pointed to by s1. The initial character of s2 overwrites the null character at the
18957 end of s1. A terminating null character is always appended to the result.<sup><a href="#note302"><b>302)</b></a></sup> If copying
18959 <!--page 381 -->
18960 takes place between objects that overlap, the behavior is undefined.
18961 <p><b>Returns</b>
18962 <p><!--para 3 -->
18963 The strncat function returns the value of s1.
18966 <p><b>Footnotes</b>
18967 <p><small><a name="note302" href="#note302">302)</a> Thus, the maximum number of characters that can end up in the array pointed to by s1 is
18968 strlen(s1)+n+1.
18969 </small>
18973 <p><!--para 1 -->
18974 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
18975 and strncmp is determined by the sign of the difference between the values of the first
18976 pair of characters (both interpreted as unsigned char) that differ in the objects being
18977 compared.
18981 <p><b>Synopsis</b>
18982 <p><!--para 1 -->
18983 <pre>
18985 int memcmp(const void *s1, const void *s2, size_t n);
18986 </pre>
18987 <p><b>Description</b>
18988 <p><!--para 2 -->
18989 The memcmp function compares the first n characters of the object pointed to by s1 to
18990 the first n characters of the object pointed to by s2.<sup><a href="#note303"><b>303)</b></a></sup>
18991 <p><b>Returns</b>
18992 <p><!--para 3 -->
18993 The memcmp function returns an integer greater than, equal to, or less than zero,
18994 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
18995 pointed to by s2.
18997 <p><b>Footnotes</b>
18998 <p><small><a name="note303" href="#note303">303)</a> The contents of ''holes'' used as padding for purposes of alignment within structure objects are
18999 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
19000 comparison.
19001 </small>
19005 <p><b>Synopsis</b>
19006 <p><!--para 1 -->
19007 <pre>
19009 int strcmp(const char *s1, const char *s2);
19010 </pre>
19011 <p><b>Description</b>
19012 <p><!--para 2 -->
19013 The strcmp function compares the string pointed to by s1 to the string pointed to by
19014 s2.
19015 <p><b>Returns</b>
19016 <p><!--para 3 -->
19017 The strcmp function returns an integer greater than, equal to, or less than zero,
19018 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
19020 <!--page 382 -->
19021 pointed to by s2.
19025 <p><b>Synopsis</b>
19026 <p><!--para 1 -->
19027 <pre>
19029 int strcoll(const char *s1, const char *s2);
19030 </pre>
19031 <p><b>Description</b>
19032 <p><!--para 2 -->
19033 The strcoll function compares the string pointed to by s1 to the string pointed to by
19034 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
19035 <p><b>Returns</b>
19036 <p><!--para 3 -->
19037 The strcoll function returns an integer greater than, equal to, or less than zero,
19038 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
19039 pointed to by s2 when both are interpreted as appropriate to the current locale.
19043 <p><b>Synopsis</b>
19044 <p><!--para 1 -->
19045 <pre>
19047 int strncmp(const char *s1, const char *s2, size_t n);
19048 </pre>
19049 <p><b>Description</b>
19050 <p><!--para 2 -->
19051 The strncmp function compares not more than n characters (characters that follow a
19052 null character are not compared) from the array pointed to by s1 to the array pointed to
19053 by s2.
19054 <p><b>Returns</b>
19055 <p><!--para 3 -->
19056 The strncmp function returns an integer greater than, equal to, or less than zero,
19057 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
19058 to, or less than the possibly null-terminated array pointed to by s2.
19062 <p><b>Synopsis</b>
19063 <p><!--para 1 -->
19064 <pre>
19066 size_t strxfrm(char * restrict s1,
19067 const char * restrict s2,
19068 size_t n);
19069 </pre>
19070 <p><b>Description</b>
19071 <p><!--para 2 -->
19072 The strxfrm function transforms the string pointed to by s2 and places the resulting
19073 string into the array pointed to by s1. The transformation is such that if the strcmp
19074 function is applied to two transformed strings, it returns a value greater than, equal to, or
19075 <!--page 383 -->
19076 less than zero, corresponding to the result of the strcoll function applied to the same
19077 two original strings. No more than n characters are placed into the resulting array
19078 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
19079 be a null pointer. If copying takes place between objects that overlap, the behavior is
19080 undefined.
19081 <p><b>Returns</b>
19082 <p><!--para 3 -->
19083 The strxfrm function returns the length of the transformed string (not including the
19084 terminating null character). If the value returned is n or more, the contents of the array
19085 pointed to by s1 are indeterminate.
19086 <p><!--para 4 -->
19087 EXAMPLE The value of the following expression is the size of the array needed to hold the
19088 transformation of the string pointed to by s.
19089 <pre>
19090 1 + strxfrm(NULL, s, 0)
19091 </pre>
19099 <p><b>Synopsis</b>
19100 <p><!--para 1 -->
19101 <pre>
19103 void *memchr(const void *s, int c, size_t n);
19104 </pre>
19105 <p><b>Description</b>
19106 <p><!--para 2 -->
19107 The memchr function locates the first occurrence of c (converted to an unsigned
19108 char) in the initial n characters (each interpreted as unsigned char) of the object
19109 pointed to by s. The implementation shall behave as if it reads the characters sequentially
19110 and stops as soon as a matching character is found.
19111 <p><b>Returns</b>
19112 <p><!--para 3 -->
19113 The memchr function returns a pointer to the located character, or a null pointer if the
19114 character does not occur in the object.
19118 <p><b>Synopsis</b>
19119 <p><!--para 1 -->
19120 <pre>
19122 char *strchr(const char *s, int c);
19123 </pre>
19124 <p><b>Description</b>
19125 <p><!--para 2 -->
19126 The strchr function locates the first occurrence of c (converted to a char) in the
19127 string pointed to by s. The terminating null character is considered to be part of the
19128 string.
19129 <!--page 384 -->
19130 <p><b>Returns</b>
19131 <p><!--para 3 -->
19132 The strchr function returns a pointer to the located character, or a null pointer if the
19133 character does not occur in the string.
19137 <p><b>Synopsis</b>
19138 <p><!--para 1 -->
19139 <pre>
19141 size_t strcspn(const char *s1, const char *s2);
19142 </pre>
19143 <p><b>Description</b>
19144 <p><!--para 2 -->
19145 The strcspn function computes the length of the maximum initial segment of the string
19146 pointed to by s1 which consists entirely of characters not from the string pointed to by
19147 s2.
19148 <p><b>Returns</b>
19149 <p><!--para 3 -->
19150 The strcspn function returns the length of the segment.
19154 <p><b>Synopsis</b>
19155 <p><!--para 1 -->
19156 <pre>
19158 char *strpbrk(const char *s1, const char *s2);
19159 </pre>
19160 <p><b>Description</b>
19161 <p><!--para 2 -->
19162 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
19163 character from the string pointed to by s2.
19164 <p><b>Returns</b>
19165 <p><!--para 3 -->
19166 The strpbrk function returns a pointer to the character, or a null pointer if no character
19167 from s2 occurs in s1.
19171 <p><b>Synopsis</b>
19172 <p><!--para 1 -->
19173 <pre>
19175 char *strrchr(const char *s, int c);
19176 </pre>
19177 <p><b>Description</b>
19178 <p><!--para 2 -->
19179 The strrchr function locates the last occurrence of c (converted to a char) in the
19180 string pointed to by s. The terminating null character is considered to be part of the
19181 string.
19182 <!--page 385 -->
19183 <p><b>Returns</b>
19184 <p><!--para 3 -->
19185 The strrchr function returns a pointer to the character, or a null pointer if c does not
19186 occur in the string.
19190 <p><b>Synopsis</b>
19191 <p><!--para 1 -->
19192 <pre>
19194 size_t strspn(const char *s1, const char *s2);
19195 </pre>
19196 <p><b>Description</b>
19197 <p><!--para 2 -->
19198 The strspn function computes the length of the maximum initial segment of the string
19199 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
19200 <p><b>Returns</b>
19201 <p><!--para 3 -->
19202 The strspn function returns the length of the segment.
19206 <p><b>Synopsis</b>
19207 <p><!--para 1 -->
19208 <pre>
19210 char *strstr(const char *s1, const char *s2);
19211 </pre>
19212 <p><b>Description</b>
19213 <p><!--para 2 -->
19214 The strstr function locates the first occurrence in the string pointed to by s1 of the
19215 sequence of characters (excluding the terminating null character) in the string pointed to
19216 by s2.
19217 <p><b>Returns</b>
19218 <p><!--para 3 -->
19219 The strstr function returns a pointer to the located string, or a null pointer if the string
19220 is not found. If s2 points to a string with zero length, the function returns s1.
19224 <p><b>Synopsis</b>
19225 <p><!--para 1 -->
19226 <pre>
19228 char *strtok(char * restrict s1,
19229 const char * restrict s2);
19230 </pre>
19231 <p><b>Description</b>
19232 <p><!--para 2 -->
19233 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
19234 sequence of tokens, each of which is delimited by a character from the string pointed to
19235 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
19236 sequence have a null first argument. The separator string pointed to by s2 may be
19237 different from call to call.
19238 <!--page 386 -->
19239 <p><!--para 3 -->
19240 The first call in the sequence searches the string pointed to by s1 for the first character
19241 that is not contained in the current separator string pointed to by s2. If no such character
19242 is found, then there are no tokens in the string pointed to by s1 and the strtok function
19243 returns a null pointer. If such a character is found, it is the start of the first token.
19244 <p><!--para 4 -->
19245 The strtok function then searches from there for a character that is contained in the
19246 current separator string. If no such character is found, the current token extends to the
19247 end of the string pointed to by s1, and subsequent searches for a token will return a null
19248 pointer. If such a character is found, it is overwritten by a null character, which
19249 terminates the current token. The strtok function saves a pointer to the following
19250 character, from which the next search for a token will start.
19251 <p><!--para 5 -->
19252 Each subsequent call, with a null pointer as the value of the first argument, starts
19253 searching from the saved pointer and behaves as described above.
19254 <p><!--para 6 -->
19255 The strtok function is not required to avoid data races. The implementation shall
19256 behave as if no library function calls the strtok function.
19257 <p><b>Returns</b>
19258 <p><!--para 7 -->
19259 The strtok function returns a pointer to the first character of a token, or a null pointer
19260 if there is no token.
19261 <p><!--para 8 -->
19262 EXAMPLE
19263 <pre>
19266 char *t;
19271 </pre>
19279 <p><b>Synopsis</b>
19280 <p><!--para 1 -->
19281 <pre>
19283 void *memset(void *s, int c, size_t n);
19284 </pre>
19285 <p><b>Description</b>
19286 <p><!--para 2 -->
19287 The memset function copies the value of c (converted to an unsigned char) into
19288 each of the first n characters of the object pointed to by s.
19289 <p><b>Returns</b>
19290 <p><!--para 3 -->
19291 The memset function returns the value of s.
19292 <!--page 387 -->
19296 <p><b>Synopsis</b>
19297 <p><!--para 1 -->
19298 <pre>
19300 char *strerror(int errnum);
19301 </pre>
19302 <p><b>Description</b>
19303 <p><!--para 2 -->
19304 The strerror function maps the number in errnum to a message string. Typically,
19305 the values for errnum come from errno, but strerror shall map any value of type
19306 int to a message.
19307 <p><!--para 3 -->
19308 The strerror function is not required to avoid data races. The implementation shall
19309 behave as if no library function calls the strerror function.
19310 <p><b>Returns</b>
19311 <p><!--para 4 -->
19312 The strerror function returns a pointer to the string, the contents of which are locale-
19313 specific. The array pointed to shall not be modified by the program, but may be
19314 overwritten by a subsequent call to the strerror function.
19318 <p><b>Synopsis</b>
19319 <p><!--para 1 -->
19320 <pre>
19322 size_t strlen(const char *s);
19323 </pre>
19324 <p><b>Description</b>
19325 <p><!--para 2 -->
19326 The strlen function computes the length of the string pointed to by s.
19327 <p><b>Returns</b>
19328 <p><!--para 3 -->
19329 The strlen function returns the number of characters that precede the terminating null
19330 character.
19331 <!--page 388 -->
19335 <p><!--para 1 -->
19336 The header <a href="#7.24"><tgmath.h></a> includes the headers <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> and
19337 defines several type-generic macros.
19338 <p><!--para 2 -->
19339 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
19340 double) suffix, several have one or more parameters whose corresponding real type is
19341 double. For each such function, except modf, there is a corresponding type-generic
19342 macro.<sup><a href="#note304"><b>304)</b></a></sup> The parameters whose corresponding real type is double in the function
19343 synopsis are generic parameters. Use of the macro invokes a function whose
19344 corresponding real type and type domain are determined by the arguments for the generic
19346 <p><!--para 3 -->
19347 Use of the macro invokes a function whose generic parameters have the corresponding
19348 real type determined as follows:
19349 <ul>
19350 <li> First, if any argument for generic parameters has type long double, the type
19351 determined is long double.
19352 <li> Otherwise, if any argument for generic parameters has type double or is of integer
19353 type, the type determined is double.
19354 <li> Otherwise, the type determined is float.
19355 </ul>
19356 <p><!--para 4 -->
19357 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
19358 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
19359 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
19360 corresponding type-generic macro for fabs and cabs is fabs.
19365 <!--page 389 -->
19366 <pre>
19368 function function macro
19369 acos cacos acos
19370 asin casin asin
19371 atan catan atan
19372 acosh cacosh acosh
19373 asinh casinh asinh
19374 atanh catanh atanh
19375 cos ccos cos
19376 sin csin sin
19377 tan ctan tan
19378 cosh ccosh cosh
19379 sinh csinh sinh
19380 tanh ctanh tanh
19381 exp cexp exp
19382 log clog log
19383 pow cpow pow
19384 sqrt csqrt sqrt
19385 fabs cabs fabs
19386 </pre>
19387 If at least one argument for a generic parameter is complex, then use of the macro invokes
19388 a complex function; otherwise, use of the macro invokes a real function.
19389 <p><!--para 5 -->
19390 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
19391 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
19392 name as the function. These type-generic macros are:
19393 <pre>
19394 atan2 fma llround remainder
19395 cbrt fmax log10 remquo
19396 ceil fmin log1p rint
19397 copysign fmod log2 round
19398 erf frexp logb scalbn
19399 erfc hypot lrint scalbln
19400 exp2 ilogb lround tgamma
19401 expm1 ldexp nearbyint trunc
19402 fdim lgamma nextafter
19403 floor llrint nexttoward
19404 </pre>
19405 If all arguments for generic parameters are real, then use of the macro invokes a real
19406 function; otherwise, use of the macro results in undefined behavior.
19407 <!--page 390 -->
19408 <p><!--para 6 -->
19409 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
19410 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
19411 function. These type-generic macros are:
19412 <pre>
19413 carg conj creal
19414 cimag cproj
19415 </pre>
19416 Use of the macro with any real or complex argument invokes a complex function.
19417 <p><!--para 7 -->
19418 EXAMPLE With the declarations
19419 <pre>
19421 int n;
19422 float f;
19423 double d;
19424 long double ld;
19425 float complex fc;
19426 double complex dc;
19427 long double complex ldc;
19428 </pre>
19429 functions invoked by use of type-generic macros are shown in the following table:
19430 <!--page 391 -->
19431 <pre>
19432 macro use invokes
19433 exp(n) exp(n), the function
19434 acosh(f) acoshf(f)
19435 sin(d) sin(d), the function
19436 atan(ld) atanl(ld)
19437 log(fc) clogf(fc)
19438 sqrt(dc) csqrt(dc)
19439 pow(ldc, f) cpowl(ldc, f)
19440 remainder(n, n) remainder(n, n), the function
19441 nextafter(d, f) nextafter(d, f), the function
19442 nexttoward(f, ld) nexttowardf(f, ld)
19443 copysign(n, ld) copysignl(n, ld)
19444 ceil(fc) undefined behavior
19445 rint(dc) undefined behavior
19446 fmax(ldc, ld) undefined behavior
19447 carg(n) carg(n), the function
19448 cproj(f) cprojf(f)
19449 creal(d) creal(d), the function
19450 cimag(ld) cimagl(ld)
19451 fabs(fc) cabsf(fc)
19452 carg(dc) carg(dc), the function
19453 cproj(ldc) cprojl(ldc)
19454 </pre>
19456 <p><b>Footnotes</b>
19457 <p><small><a name="note304" href="#note304">304)</a> Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
19458 make available the corresponding ordinary function.
19459 </small>
19460 <p><small><a name="note305" href="#note305">305)</a> If the type of the argument is not compatible with the type of the parameter for the selected function,
19461 the behavior is undefined.
19462 </small>
19469 <p><!--para 1 -->
19470 The header <a href="#7.25"><threads.h></a> defines macros, and declares types, enumeration constants,
19471 and functions that support multiple threads of execution.
19472 <p><!--para 2 -->
19473 Implementations that define the macro __STDC_NO_THREADS__ need not provide
19474 this header nor support any of its facilities.
19475 <p><!--para 3 -->
19476 The macros are
19477 <pre>
19478 ONCE_FLAG_INIT
19479 </pre>
19480 which expands to a value that can be used to initialize an object of type once_flag;
19481 and
19482 <pre>
19483 TSS_DTOR_ITERATIONS
19484 </pre>
19485 which expands to an integer constant expression representing the maximum number of
19486 times that destructors will be called when a thread terminates.
19487 <p><!--para 4 -->
19488 The types are
19489 <pre>
19490 cnd_t
19491 </pre>
19492 which is a complete object type that holds an identifier for a condition variable;
19493 <pre>
19494 thrd_t
19495 </pre>
19496 which is a complete object type that holds an identifier for a thread;
19497 <pre>
19498 tss_t
19499 </pre>
19500 which is a complete object type that holds an identifier for a thread-specific storage
19501 pointer;
19502 <pre>
19503 mtx_t
19504 </pre>
19505 which is a complete object type that holds an identifier for a mutex;
19506 <pre>
19507 tss_dtor_t
19508 </pre>
19509 which is the function pointer type void (*)(void*), used for a destructor for a
19510 thread-specific storage pointer;
19511 <pre>
19512 thrd_start_t
19513 </pre>
19514 which is the function pointer type int (*)(void*) that is passed to thrd_create
19515 to create a new thread;
19516 <pre>
19517 once_flag
19518 </pre>
19519 which is a complete object type that holds a flag for use by call_once; and
19520 <!--page 392 -->
19521 <pre>
19522 xtime
19523 </pre>
19524 which is a structure type that holds a time specified in seconds and nanoseconds. The
19525 structure shall contain at least the following members, in any order.
19526 <pre>
19527 time_t sec;
19528 long nsec;
19529 </pre>
19530 <p><!--para 5 -->
19531 The enumeration constants are
19532 <pre>
19533 mtx_plain
19534 </pre>
19535 which is passed to mtx_init to create a mutex object that supports neither timeout nor
19536 test and return;
19537 <pre>
19538 mtx_recursive
19539 </pre>
19540 which is passed to mtx_init to create a mutex object that supports recursive locking;
19541 <pre>
19542 mtx_timed
19543 </pre>
19544 which is passed to mtx_init to create a mutex object that supports timeout;
19545 <pre>
19546 mtx_try
19547 </pre>
19548 which is passed to mtx_init to create a mutex object that supports test and return;
19549 <pre>
19550 thrd_timeout
19551 </pre>
19552 which is returned by a timed wait function to indicate that the time specified in the call
19553 was reached without acquiring the requested resource;
19554 <pre>
19555 thrd_success
19556 </pre>
19557 which is returned by a function to indicate that the requested operation succeeded;
19558 <pre>
19559 thrd_busy
19560 </pre>
19561 which is returned by a function to indicate that the requested operation failed because a
19562 resource requested by a test and return function is already in use;
19563 <pre>
19564 thrd_error
19565 </pre>
19566 which is returned by a function to indicate that the requested operation failed; and
19567 <pre>
19568 thrd_nomem
19569 </pre>
19570 which is returned by a function to indicate that the requested operation failed because it
19571 was unable to allocate memory.
19572 <!--page 393 -->
19579 <p><b>Synopsis</b>
19580 <p><!--para 1 -->
19581 <pre>
19583 void call_once(once_flag *flag, void (*func)(void));
19584 </pre>
19585 <p><b>Description</b>
19586 <p><!--para 2 -->
19587 The call_once function uses the once_flag pointed to by flag to ensure that
19588 func is called exactly once, the first time the call_once function is called with that
19589 value of flag. Completion of an effective call to the call_once function synchronizes
19590 with all subsequent calls to the call_once function with the same value of flag.
19591 <p><b>Returns</b>
19592 <p><!--para 3 -->
19593 The call_once function returns no value.
19600 <p><b>Synopsis</b>
19601 <p><!--para 1 -->
19602 <pre>
19604 int cnd_broadcast(cnd_t *cond);
19605 </pre>
19606 <p><b>Description</b>
19607 <p><!--para 2 -->
19608 The cnd_broadcast function unblocks all of the threads that are blocked on the
19609 condition variable pointed to by cond at the time of the call. If no threads are blocked
19610 on the condition variable pointed to by cond at the time of the call, the function does
19611 nothing.
19612 <p><b>Returns</b>
19613 <p><!--para 3 -->
19614 The cnd_broadcast function returns thrd_success on success, or thrd_error
19615 if the request could not be honored.
19619 <p><b>Synopsis</b>
19620 <p><!--para 1 -->
19621 <pre>
19623 void cnd_destroy(cnd_t *cond);
19624 </pre>
19625 <p><b>Description</b>
19626 <p><!--para 2 -->
19627 The cnd_destroy function releases all resources used by the condition variable
19628 pointed to by cond. The cnd_destroy function requires that no threads be blocked
19629 waiting for the condition variable pointed to by cond.
19630 <!--page 394 -->
19631 <p><b>Returns</b>
19632 <p><!--para 3 -->
19633 The cnd_destroy function returns no value.
19637 <p><b>Synopsis</b>
19638 <p><!--para 1 -->
19639 <pre>
19641 int cnd_init(cnd_t *cond);
19642 </pre>
19643 <p><b>Description</b>
19644 <p><!--para 2 -->
19645 The cnd_init function creates a condition variable. If it succeeds it sets the variable
19646 pointed to by cond to a value that uniquely identifies the newly created condition
19647 variable. A thread that calls cnd_wait on a newly created condition variable will
19648 block.
19649 <p><b>Returns</b>
19650 <p><!--para 3 -->
19651 The cnd_init function returns thrd_success on success, or thrd_nomem if no
19652 memory could be allocated for the newly created condition, or thrd_error if the
19653 request could not be honored.
19657 <p><b>Synopsis</b>
19658 <p><!--para 1 -->
19659 <pre>
19661 int cnd_signal(cnd_t *cond);
19662 </pre>
19663 <p><b>Description</b>
19664 <p><!--para 2 -->
19665 The cnd_signal function unblocks one of the threads that are blocked on the
19666 condition variable pointed to by cond at the time of the call. If no threads are blocked
19667 on the condition variable at the time of the call, the function does nothing and return
19668 success.
19669 <p><b>Returns</b>
19670 <p><!--para 3 -->
19671 The cnd_signal function returns thrd_success on success or thrd_error if
19672 the request could not be honored.
19676 <p><b>Synopsis</b>
19677 <p><!--para 1 -->
19678 <!--page 395 -->
19679 <pre>
19681 int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
19682 const xtime *xt);
19683 </pre>
19684 <p><b>Description</b>
19685 <p><!--para 2 -->
19686 The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and
19687 endeavors to block until the condition variable pointed to by cond is signaled by a call to
19688 cnd_signal or to cnd_broadcast, or until after the time specified by the xtime
19689 object pointed to by xt. When the calling thread becomes unblocked it locks the variable
19690 pointed to by mtx before it returns. The cnd_timedwait function requires that the
19691 mutex pointed to by mtx be locked by the calling thread.
19692 <p><b>Returns</b>
19693 <p><!--para 3 -->
19694 The cnd_timedwait function returns thrd_success upon success, or
19695 thrd_timeout if the time specified in the call was reached without acquiring the
19696 requested resource, or thrd_error if the request could not be honored.
19700 <p><b>Synopsis</b>
19701 <p><!--para 1 -->
19702 <pre>
19704 int cnd_wait(cnd_t *cond, mtx_t *mtx);
19705 </pre>
19706 <p><b>Description</b>
19707 <p><!--para 2 -->
19708 The cnd_wait function atomically unlocks the mutex pointed to by mtx and endeavors
19709 to block until the condition variable pointed to by cond is signaled by a call to
19710 cnd_signal or to cnd_broadcast. When the calling thread becomes unblocked it
19711 locks the mutex pointed to by mtx before it returns. If the mutex pointed to by mtx is
19712 not locked by the calling thread, the cnd_wait function will act as if the abort
19713 function is called.
19714 <p><b>Returns</b>
19715 <p><!--para 3 -->
19716 The cnd_wait function returns thrd_success on success or thrd_error if the
19717 request could not be honored.
19724 <p><b>Synopsis</b>
19725 <p><!--para 1 -->
19726 <pre>
19728 void mtx_destroy(mtx_t *mtx);
19729 </pre>
19730 <p><b>Description</b>
19731 <p><!--para 2 -->
19732 The mtx_destroy function releases any resources used by the mutex pointed to by
19733 mtx. No threads can be blocked waiting for the mutex pointed to by mtx.
19734 <!--page 396 -->
19735 <p><b>Returns</b>
19736 <p><!--para 3 -->
19737 The mtx_destroy function returns no value.
19741 <p><b>Synopsis</b>
19742 <p><!--para 1 -->
19743 <pre>
19745 int mtx_init(mtx_t *mtx, int type);
19746 </pre>
19747 <p><b>Description</b>
19748 <p><!--para 2 -->
19749 The mtx_init function creates a mutex object with properties indicated by type,
19750 which must have one of the six values:
19751 mtx_plain for a simple non-recursive mutex,
19752 mtx_timed for a non-recursive mutex that supports timeout,
19753 mtx_try for a non-recursive mutex that supports test and return,
19754 mtx_plain | mtx_recursive for a simple recursive mutex,
19755 mtx_timed | mtx_recursive for a recursive mutex that supports timeout, or
19756 mtx_try | mtx_recursive for a recursive mutex that supports test and return.
19757 <p><!--para 3 -->
19758 If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that
19759 uniquely identifies the newly created mutex.
19760 <p><b>Returns</b>
19761 <p><!--para 4 -->
19762 The mtx_init function returns thrd_success on success, or thrd_error if the
19763 request could not be honored.
19767 <p><b>Synopsis</b>
19768 <p><!--para 1 -->
19769 <pre>
19771 int mtx_lock(mtx_t *mtx);
19772 </pre>
19773 <p><b>Description</b>
19774 <p><!--para 2 -->
19775 The mtx_lock function blocks until it locks the mutex pointed to by mtx. If the mutex
19776 is non-recursive, it shall not be locked by the calling thread. Prior calls to mtx_unlock
19777 on the same mutex shall synchronize with this operation.
19778 <p><b>Returns</b>
19779 <p><!--para 3 -->
19780 The mtx_lock function returns thrd_success on success, or thrd_busy if the
19781 resource requested is already in use, or thrd_error if the request could not be
19782 honored.
19783 <!--page 397 -->
19787 <p><b>Synopsis</b>
19788 <p><!--para 1 -->
19789 <pre>
19791 int mtx_timedlock(mtx_t *mtx, const xtime *xt);
19792 </pre>
19793 <p><b>Description</b>
19794 <p><!--para 2 -->
19795 The mtx_timedlock function endeavors to block until it locks the mutex pointed to by
19796 mtx or until the time specified by the xtime object xt has passed. The specified mutex
19797 shall support timeout. If the operation succeeds, prior calls to mtx_unlock on the same
19798 mutex shall synchronize with this operation.
19799 <p><b>Returns</b>
19800 <p><!--para 3 -->
19801 The mtx_timedlock function returns thrd_success on success, or thrd_busy
19802 if the resource requested is already in use, or thrd_timeout if the time specified was
19803 reached without acquiring the requested resource, or thrd_error if the request could
19804 not be honored.
19808 <p><b>Synopsis</b>
19809 <p><!--para 1 -->
19810 <pre>
19812 int mtx_trylock(mtx_t *mtx);
19813 </pre>
19814 <p><b>Description</b>
19815 <p><!--para 2 -->
19816 The mtx_trylock function endeavors to lock the mutex pointed to by mtx. The
19817 specified mutex shall support either test and return or timeout. If the mutex is already
19818 locked, the function returns without blocking. If the operation succeeds, prior calls to
19819 mtx_unlock on the same mutex shall synchronize with this operation.
19820 <p><b>Returns</b>
19821 <p><!--para 3 -->
19822 The mtx_trylock function returns thrd_success on success, or thrd_busy if
19823 the resource requested is already in use, or thrd_error if the request could not be
19824 honored.
19828 <p><b>Synopsis</b>
19829 <p><!--para 1 -->
19830 <pre>
19832 int mtx_unlock(mtx_t *mtx);
19833 </pre>
19834 <p><b>Description</b>
19835 <p><!--para 2 -->
19836 The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to
19837 by mtx shall be locked by the calling thread.
19838 <!--page 398 -->
19839 <p><b>Returns</b>
19840 <p><!--para 3 -->
19841 The mtx_unlock function returns thrd_success on success or thrd_error if
19842 the request could not be honored.
19849 <p><b>Synopsis</b>
19850 <p><!--para 1 -->
19851 <pre>
19853 int thrd_create(thrd_t *thr, thrd_start_t func,
19854 void *arg);
19855 </pre>
19856 <p><b>Description</b>
19857 <p><!--para 2 -->
19858 The thrd_create function creates a new thread executing func(arg). If the
19859 thrd_create function succeeds, it sets the object pointed to by thr to the identifier of
19860 the newly created thread. (A thread's identifier may be reused for a different thread once
19861 the original thread has exited and either been detached or joined to another thread.) The
19862 completion of the thrd_create function synchronizes with the beginning of the
19863 execution of the new thread.
19864 <p><b>Returns</b>
19865 <p><!--para 3 -->
19866 The thrd_create function returns thrd_success on success, or thrd_nomem if
19867 no memory could be allocated for the thread requested, or thrd_error if the request
19868 could not be honored.
19872 <p><b>Synopsis</b>
19873 <p><!--para 1 -->
19874 <pre>
19876 thrd_t thrd_current(void);
19877 </pre>
19878 <p><b>Description</b>
19879 <p><!--para 2 -->
19880 The thrd_current function identifies the thread that called it.
19881 <p><b>Returns</b>
19882 <p><!--para 3 -->
19883 The thrd_current function returns the identifier of the thread that called it.
19887 <p><b>Synopsis</b>
19888 <p><!--para 1 -->
19889 <!--page 399 -->
19890 <pre>
19892 int thrd_detach(thrd_t thr);
19893 </pre>
19894 <p><b>Description</b>
19895 <p><!--para 2 -->
19896 The thrd_detach function tells the operating system to dispose of any resources
19897 allocated to the thread identified by thr when that thread terminates. The thread
19898 identified by thr shall not have been previously detached or joined with another thread.
19899 <p><b>Returns</b>
19900 <p><!--para 3 -->
19901 The thrd_detach function returns thrd_success on success or thrd_error if
19902 the request could not be honored.
19906 <p><b>Synopsis</b>
19907 <p><!--para 1 -->
19908 <pre>
19910 int thrd_equal(thrd_t thr0, thrd_t thr1);
19911 </pre>
19912 <p><b>Description</b>
19913 <p><!--para 2 -->
19914 The thrd_equal function will determine whether the thread identified by thr0 refers
19915 to the thread identified by thr1.
19916 <p><b>Returns</b>
19917 <p><!--para 3 -->
19918 The thrd_equal function returns zero if the thread thr0 and the thread thr1 refer to
19919 different threads. Otherwise the thrd_equal function returns a nonzero value.
19923 <p><b>Synopsis</b>
19924 <p><!--para 1 -->
19925 <pre>
19927 void thrd_exit(int res);
19928 </pre>
19929 <p><b>Description</b>
19930 <p><!--para 2 -->
19931 The thrd_exit function terminates execution of the calling thread and sets its result
19932 code to res.
19933 <p><b>Returns</b>
19934 <p><!--para 3 -->
19935 The thrd_exit function returns no value.
19939 <p><b>Synopsis</b>
19940 <p><!--para 1 -->
19941 <pre>
19943 int thrd_join(thrd_t thr, int *res);
19944 </pre>
19945 <p><b>Description</b>
19946 <p><!--para 2 -->
19947 The thrd_join function joins the thread identified by thr with the current thread by
19948 blocking until the other thread has terminated. If the parameter res is not a null pointer,
19949 <!--page 400 -->
19950 it stores the thread's result code in the integer pointed to by res. The termination of the
19951 other thread synchronizes with the completion of the thrd_join function. The thread
19952 identified by thr shall not have been previously detached or joined with another thread.
19953 <p><b>Returns</b>
19954 <p><!--para 3 -->
19955 The thrd_join function returns thrd_success on success or thrd_error if the
19956 request could not be honored.
19960 <p><b>Synopsis</b>
19961 <p><!--para 1 -->
19962 <pre>
19964 void thrd_sleep(const xtime *xt);
19965 </pre>
19966 <p><b>Description</b>
19967 <p><!--para 2 -->
19968 The thrd_sleep function suspends execution of the calling thread until after the time
19969 specified by the xtime object pointed to by xt.
19970 <p><b>Returns</b>
19971 <p><!--para 3 -->
19972 The thrd_sleep function returns no value.
19976 <p><b>Synopsis</b>
19977 <p><!--para 1 -->
19978 <pre>
19980 void thrd_yield(void);
19981 </pre>
19982 <p><b>Description</b>
19983 <p><!--para 2 -->
19984 The thrd_yield function endeavors to permit other threads to run, even if the current
19985 thread would ordinarily continue to run.
19986 <p><b>Returns</b>
19987 <p><!--para 3 -->
19988 The thrd_yield function returns no value.
19995 <p><b>Synopsis</b>
19996 <p><!--para 1 -->
19997 <pre>
19999 int tss_create(tss_t *key, tss_dtor_t dtor);
20000 </pre>
20001 <p><b>Description</b>
20002 <p><!--para 2 -->
20003 The tss_create function creates a thread-specific storage pointer with destructor
20004 dtor, which may be null.
20005 <!--page 401 -->
20006 <p><b>Returns</b>
20007 <p><!--para 3 -->
20008 If the tss_create function is successful, it sets the thread-specific storage pointed to
20009 by key to a value that uniquely identifies the newly created pointer and returns
20010 thrd_success; otherwise, thrd_error is returned and the thread-specific storage
20011 pointed to by key is set to an undefined value.
20015 <p><b>Synopsis</b>
20016 <p><!--para 1 -->
20017 <pre>
20019 void tss_delete(tss_t key);
20020 </pre>
20021 <p><b>Description</b>
20022 <p><!--para 2 -->
20023 The tss_delete function releases any resources used by the thread-specific storage
20024 identified by key.
20025 <p><b>Returns</b>
20026 <p><!--para 3 -->
20027 The tss_delete function returns no value.
20031 <p><b>Synopsis</b>
20032 <p><!--para 1 -->
20033 <pre>
20035 void *tss_get(tss_t key);
20036 </pre>
20037 <p><b>Description</b>
20038 <p><!--para 2 -->
20039 The tss_get function returns the value for the current thread held in the thread-specific
20040 storage identified by key.
20041 <p><b>Returns</b>
20042 <p><!--para 3 -->
20043 The tss_get function returns the value for the current thread if successful, or zero if
20044 unsuccessful.
20048 <p><b>Synopsis</b>
20049 <p><!--para 1 -->
20050 <pre>
20052 int tss_set(tss_t key, void *val);
20053 </pre>
20054 <p><b>Description</b>
20055 <p><!--para 2 -->
20056 The tss_set function sets the value for the current thread held in the thread-specific
20057 storage identified by key to val.
20058 <!--page 402 -->
20059 <p><b>Returns</b>
20060 <p><!--para 3 -->
20061 The tss_set function returns thrd_success on success or thrd_error if the
20062 request could not be honored.
20069 <p><b>Synopsis</b>
20070 <p><!--para 1 -->
20071 <pre>
20073 int xtime_get(xtime *xt, int base);
20074 </pre>
20075 <p><b>Description</b>
20076 <p><!--para 2 -->
20077 The xtime_get function sets the xtime object pointed to by xt to hold the current
20078 time based on the time base base.
20079 <p><b>Returns</b>
20080 <p><!--para 3 -->
20081 If the xtime_get function is successful it returns the nonzero value base, which must
20087 <!--page 403 -->
20089 <p><b>Footnotes</b>
20090 <p><small><a name="note306" href="#note306">306)</a> Although an xtime object describes times with nanosecond resolution, the actual resolution in an
20091 xtime object is system dependent.
20092 </small>
20099 <p><!--para 1 -->
20100 The header <a href="#7.26"><time.h></a> defines two macros, and declares several types and functions for
20101 manipulating time. Many functions deal with a calendar time that represents the current
20102 date (according to the Gregorian calendar) and time. Some functions deal with local
20103 time, which is the calendar time expressed for some specific time zone, and with Daylight
20104 Saving Time, which is a temporary change in the algorithm for determining local time.
20105 The local time zone and Daylight Saving Time are implementation-defined.
20106 <p><!--para 2 -->
20108 <pre>
20109 CLOCKS_PER_SEC
20110 </pre>
20111 which expands to an expression with type clock_t (described below) that is the
20112 number per second of the value returned by the clock function.
20113 <p><!--para 3 -->
20115 <pre>
20116 clock_t
20117 </pre>
20118 and
20119 <pre>
20120 time_t
20121 </pre>
20122 which are arithmetic types capable of representing times; and
20123 <pre>
20124 struct tm
20125 </pre>
20126 which holds the components of a calendar time, called the broken-down time.
20127 <p><!--para 4 -->
20128 The range and precision of times representable in clock_t and time_t are
20129 implementation-defined. The tm structure shall contain at least the following members,
20130 in any order. The semantics of the members and their normal ranges are expressed in the
20132 <pre>
20133 int tm_sec; // seconds after the minute -- [0, 60]
20134 int tm_min; // minutes after the hour -- [0, 59]
20135 int tm_hour; // hours since midnight -- [0, 23]
20136 int tm_mday; // day of the month -- [1, 31]
20137 int tm_mon; // months since January -- [0, 11]
20138 int tm_year; // years since 1900
20139 int tm_wday; // days since Sunday -- [0, 6]
20140 int tm_yday; // days since January 1 -- [0, 365]
20141 int tm_isdst; // Daylight Saving Time flag
20142 </pre>
20146 <!--page 404 -->
20147 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
20148 Saving Time is not in effect, and negative if the information is not available.
20150 <p><b>Footnotes</b>
20151 <p><small><a name="note307" href="#note307">307)</a> The range [0, 60] for tm_sec allows for a positive leap second.
20152 </small>
20159 <p><b>Synopsis</b>
20160 <p><!--para 1 -->
20161 <pre>
20163 clock_t clock(void);
20164 </pre>
20165 <p><b>Description</b>
20166 <p><!--para 2 -->
20167 The clock function determines the processor time used.
20168 <p><b>Returns</b>
20169 <p><!--para 3 -->
20170 The clock function returns the implementation's best approximation to the processor
20171 time used by the program since the beginning of an implementation-defined era related
20172 only to the program invocation. To determine the time in seconds, the value returned by
20173 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
20174 the processor time used is not available or its value cannot be represented, the function
20177 <p><b>Footnotes</b>
20178 <p><small><a name="note308" href="#note308">308)</a> In order to measure the time spent in a program, the clock function should be called at the start of
20179 the program and its return value subtracted from the value returned by subsequent calls.
20180 </small>
20184 <p><b>Synopsis</b>
20185 <p><!--para 1 -->
20186 <pre>
20188 double difftime(time_t time1, time_t time0);
20189 </pre>
20190 <p><b>Description</b>
20191 <p><!--para 2 -->
20192 The difftime function computes the difference between two calendar times: time1 -
20193 time0.
20194 <p><b>Returns</b>
20195 <p><!--para 3 -->
20196 The difftime function returns the difference expressed in seconds as a double.
20201 <!--page 405 -->
20205 <p><b>Synopsis</b>
20206 <p><!--para 1 -->
20207 <pre>
20209 time_t mktime(struct tm *timeptr);
20210 </pre>
20211 <p><b>Description</b>
20212 <p><!--para 2 -->
20213 The mktime function converts the broken-down time, expressed as local time, in the
20214 structure pointed to by timeptr into a calendar time value with the same encoding as
20215 that of the values returned by the time function. The original values of the tm_wday
20216 and tm_yday components of the structure are ignored, and the original values of the
20217 other components are not restricted to the ranges indicated above.<sup><a href="#note309"><b>309)</b></a></sup> On successful
20218 completion, the values of the tm_wday and tm_yday components of the structure are
20219 set appropriately, and the other components are set to represent the specified calendar
20220 time, but with their values forced to the ranges indicated above; the final value of
20221 tm_mday is not set until tm_mon and tm_year are determined.
20222 <p><b>Returns</b>
20223 <p><!--para 3 -->
20224 The mktime function returns the specified calendar time encoded as a value of type
20225 time_t. If the calendar time cannot be represented, the function returns the value
20226 (time_t)(-1).
20227 <p><!--para 4 -->
20228 EXAMPLE What day of the week is July 4, 2001?
20229 <pre>
20232 static const char *const wday[] = {
20235 };
20236 struct tm time_str;
20237 /* ... */
20238 </pre>
20243 <!--page 406 -->
20244 <pre>
20245 time_str.tm_year = 2001 - 1900;
20246 time_str.tm_mon = 7 - 1;
20247 time_str.tm_mday = 4;
20248 time_str.tm_hour = 0;
20249 time_str.tm_min = 0;
20250 time_str.tm_sec = 1;
20251 time_str.tm_isdst = -1;
20252 if (mktime(&time_str) == (time_t)(-1))
20253 time_str.tm_wday = 7;
20255 </pre>
20258 <p><b>Footnotes</b>
20259 <p><small><a name="note309" href="#note309">309)</a> Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
20260 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
20261 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
20262 </small>
20266 <p><b>Synopsis</b>
20267 <p><!--para 1 -->
20268 <pre>
20270 time_t time(time_t *timer);
20271 </pre>
20272 <p><b>Description</b>
20273 <p><!--para 2 -->
20274 The time function determines the current calendar time. The encoding of the value is
20275 unspecified.
20276 <p><b>Returns</b>
20277 <p><!--para 3 -->
20278 The time function returns the implementation's best approximation to the current
20279 calendar time. The value (time_t)(-1) is returned if the calendar time is not
20280 available. If timer is not a null pointer, the return value is also assigned to the object it
20281 points to.
20285 <p><!--para 1 -->
20286 Except for the strftime function, these functions each return a pointer to one of two
20287 types of static objects: a broken-down time structure or an array of char. Execution of
20288 any of the functions that return a pointer to one of these object types may overwrite the
20289 information in any object of the same type pointed to by the value returned from any
20290 previous call to any of them and the functions are not required to avoid data races. The
20291 implementation shall behave as if no other library functions call these functions.
20295 <p><b>Synopsis</b>
20296 <p><!--para 1 -->
20297 <pre>
20299 char *asctime(const struct tm *timeptr);
20300 </pre>
20301 <p><b>Description</b>
20302 <p><!--para 2 -->
20303 The asctime function converts the broken-down time in the structure pointed to by
20304 timeptr into a string in the form
20305 <!--page 407 -->
20306 <pre>
20307 Sun Sep 16 01:03:52 1973\n\0
20308 </pre>
20309 using the equivalent of the following algorithm.
20310 char *asctime(const struct tm *timeptr)
20311 {
20312 <pre>
20313 static const char wday_name[7][3] = {
20315 };
20316 static const char mon_name[12][3] = {
20319 };
20320 static char result[26];
20322 wday_name[timeptr->tm_wday],
20323 mon_name[timeptr->tm_mon],
20324 timeptr->tm_mday, timeptr->tm_hour,
20325 timeptr->tm_min, timeptr->tm_sec,
20326 1900 + timeptr->tm_year);
20327 return result;
20328 </pre>
20329 }
20330 <p><!--para 3 -->
20331 If any of the fields of the broken-down time contain values that are outside their normal
20332 ranges,<sup><a href="#note310"><b>310)</b></a></sup> the behavior of the asctime function is undefined. Likewise, if the
20333 calculated year exceeds four digits or is less than the year 1000, the behavior is
20334 undefined.
20335 <p><b>Returns</b>
20336 <p><!--para 4 -->
20337 The asctime function returns a pointer to the string.
20339 <p><b>Footnotes</b>
20341 </small>
20345 <p><b>Synopsis</b>
20346 <p><!--para 1 -->
20347 <pre>
20349 char *ctime(const time_t *timer);
20350 </pre>
20351 <p><b>Description</b>
20352 <p><!--para 2 -->
20353 The ctime function converts the calendar time pointed to by timer to local time in the
20354 form of a string. It is equivalent to
20355 <pre>
20356 asctime(localtime(timer))
20357 </pre>
20361 <!--page 408 -->
20362 <p><b>Returns</b>
20363 <p><!--para 3 -->
20364 The ctime function returns the pointer returned by the asctime function with that
20365 broken-down time as argument.
20370 <p><b>Synopsis</b>
20371 <p><!--para 1 -->
20372 <pre>
20374 struct tm *gmtime(const time_t *timer);
20375 </pre>
20376 <p><b>Description</b>
20377 <p><!--para 2 -->
20378 The gmtime function converts the calendar time pointed to by timer into a broken-
20379 down time, expressed as UTC.
20380 <p><b>Returns</b>
20381 <p><!--para 3 -->
20382 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
20383 specified time cannot be converted to UTC.
20387 <p><b>Synopsis</b>
20388 <p><!--para 1 -->
20389 <pre>
20391 struct tm *localtime(const time_t *timer);
20392 </pre>
20393 <p><b>Description</b>
20394 <p><!--para 2 -->
20395 The localtime function converts the calendar time pointed to by timer into a
20396 broken-down time, expressed as local time.
20397 <p><b>Returns</b>
20398 <p><!--para 3 -->
20399 The localtime function returns a pointer to the broken-down time, or a null pointer if
20400 the specified time cannot be converted to local time.
20404 <p><b>Synopsis</b>
20405 <p><!--para 1 -->
20406 <!--page 409 -->
20407 <pre>
20409 size_t strftime(char * restrict s,
20410 size_t maxsize,
20411 const char * restrict format,
20412 const struct tm * restrict timeptr);
20413 </pre>
20414 <p><b>Description</b>
20415 <p><!--para 2 -->
20416 The strftime function places characters into the array pointed to by s as controlled by
20417 the string pointed to by format. The format shall be a multibyte character sequence,
20418 beginning and ending in its initial shift state. The format string consists of zero or
20419 more conversion specifiers and ordinary multibyte characters. A conversion specifier
20420 consists of a % character, possibly followed by an E or O modifier character (described
20421 below), followed by a character that determines the behavior of the conversion specifier.
20422 All ordinary multibyte characters (including the terminating null character) are copied
20423 unchanged into the array. If copying takes place between objects that overlap, the
20424 behavior is undefined. No more than maxsize characters are placed into the array.
20425 <p><!--para 3 -->
20426 Each conversion specifier is replaced by appropriate characters as described in the
20427 following list. The appropriate characters are determined using the LC_TIME category
20428 of the current locale and by the values of zero or more members of the broken-down time
20429 structure pointed to by timeptr, as specified in brackets in the description. If any of
20430 the specified values is outside the normal range, the characters stored are unspecified.
20431 %a is replaced by the locale's abbreviated weekday name. [tm_wday]
20432 %A is replaced by the locale's full weekday name. [tm_wday]
20433 %b is replaced by the locale's abbreviated month name. [tm_mon]
20434 %B is replaced by the locale's full month name. [tm_mon]
20435 %c is replaced by the locale's appropriate date and time representation. [all specified
20436 <pre>
20438 </pre>
20439 %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
20440 <pre>
20441 number (00-99). [tm_year]
20442 </pre>
20443 %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
20444 %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
20445 %e is replaced by the day of the month as a decimal number (1-31); a single digit is
20446 <pre>
20447 preceded by a space. [tm_mday]
20448 </pre>
20449 %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
20450 <pre>
20451 tm_mday]
20452 </pre>
20453 %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
20454 <pre>
20455 number (00-99). [tm_year, tm_wday, tm_yday]
20456 </pre>
20457 %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
20458 <pre>
20459 [tm_year, tm_wday, tm_yday]
20460 </pre>
20461 %h is equivalent to ''%b''. [tm_mon]
20462 %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
20463 %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
20464 %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
20465 %m is replaced by the month as a decimal number (01-12). [tm_mon]
20466 %M is replaced by the minute as a decimal number (00-59). [tm_min]
20467 %n is replaced by a new-line character.
20468 <!--page 410 -->
20469 %p is replaced by the locale's equivalent of the AM/PM designations associated with a
20470 <pre>
20471 12-hour clock. [tm_hour]
20472 </pre>
20473 %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
20474 %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
20475 %S is replaced by the second as a decimal number (00-60). [tm_sec]
20476 %t is replaced by a horizontal-tab character.
20477 %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
20478 <pre>
20479 tm_sec]
20480 </pre>
20481 %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
20482 <pre>
20483 is 1. [tm_wday]
20484 </pre>
20485 %U is replaced by the week number of the year (the first Sunday as the first day of week
20486 <pre>
20487 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
20488 </pre>
20489 %V is replaced by the ISO 8601 week number (see below) as a decimal number
20490 <pre>
20491 (01-53). [tm_year, tm_wday, tm_yday]
20492 </pre>
20493 %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
20494 <pre>
20495 [tm_wday]
20496 </pre>
20497 %W is replaced by the week number of the year (the first Monday as the first day of
20498 <pre>
20499 week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
20500 </pre>
20501 %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.26.1">7.26.1</a>]
20502 %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.26.1">7.26.1</a>]
20503 %y is replaced by the last 2 digits of the year as a decimal number (00-99).
20504 <pre>
20505 [tm_year]
20506 </pre>
20507 %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
20508 %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
20509 <pre>
20510 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
20511 zone is determinable. [tm_isdst]
20512 </pre>
20513 %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
20514 <pre>
20515 time zone is determinable. [tm_isdst]
20516 </pre>
20517 %% is replaced by %.
20518 <p><!--para 4 -->
20519 Some conversion specifiers can be modified by the inclusion of an E or O modifier
20520 character to indicate an alternative format or specification. If the alternative format or
20521 specification does not exist for the current locale, the modifier is ignored.
20522 %Ec is replaced by the locale's alternative date and time representation.
20523 %EC is replaced by the name of the base year (period) in the locale's alternative
20524 <pre>
20525 representation.
20526 </pre>
20527 %Ex is replaced by the locale's alternative date representation.
20528 %EX is replaced by the locale's alternative time representation.
20529 %Ey is replaced by the offset from %EC (year only) in the locale's alternative
20530 <pre>
20531 representation.
20532 </pre>
20533 %EY is replaced by the locale's full alternative year representation.
20534 <!--page 411 -->
20535 %Od is replaced by the day of the month, using the locale's alternative numeric symbols
20536 <pre>
20537 (filled as needed with leading zeros, or with leading spaces if there is no alternative
20538 symbol for zero).
20539 </pre>
20540 %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
20541 <pre>
20542 (filled as needed with leading spaces).
20543 </pre>
20544 %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
20545 <pre>
20546 symbols.
20547 </pre>
20548 %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
20549 <pre>
20550 symbols.
20551 </pre>
20552 %Om is replaced by the month, using the locale's alternative numeric symbols.
20553 %OM is replaced by the minutes, using the locale's alternative numeric symbols.
20554 %OS is replaced by the seconds, using the locale's alternative numeric symbols.
20555 %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
20556 <pre>
20557 representation, where Monday is 1.
20558 </pre>
20559 %OU is replaced by the week number, using the locale's alternative numeric symbols.
20560 %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
20561 <pre>
20562 symbols.
20563 </pre>
20564 %Ow is replaced by the weekday as a number, using the locale's alternative numeric
20565 <pre>
20566 symbols.
20567 </pre>
20568 %OW is replaced by the week number of the year, using the locale's alternative numeric
20569 <pre>
20570 symbols.
20571 </pre>
20572 %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
20573 <pre>
20574 symbols.
20575 </pre>
20576 <p><!--para 5 -->
20577 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
20578 weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
20579 which is also the week that includes the first Thursday of the year, and is also the first
20580 week that contains at least four days in the year. If the first Monday of January is the
20581 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
20582 for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
20583 December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
20584 the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
20585 %V is replaced by 01.
20586 <p><!--para 6 -->
20587 If a conversion specifier is not one of the above, the behavior is undefined.
20588 <p><!--para 7 -->
20590 following specifiers are:
20591 %a the first three characters of %A.
20592 %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
20593 %b the first three characters of %B.
20594 %B one of ''January'', ''February'', ... , ''December''.
20595 %c equivalent to ''%a %b %e %T %Y''.
20596 <!--page 412 -->
20597 %p one of ''AM'' or ''PM''.
20598 %r equivalent to ''%I:%M:%S %p''.
20599 %x equivalent to ''%m/%d/%y''.
20600 %X equivalent to %T.
20601 %Z implementation-defined.
20602 <p><b>Returns</b>
20603 <p><!--para 8 -->
20604 If the total number of resulting characters including the terminating null character is not
20605 more than maxsize, the strftime function returns the number of characters placed
20606 into the array pointed to by s not including the terminating null character. Otherwise,
20607 zero is returned and the contents of the array are indeterminate.
20608 <!--page 413 -->
20612 <p><!--para 1 -->
20613 The header <a href="#7.27"><uchar.h></a> declares types and functions for manipulating Unicode
20614 characters.
20615 <p><!--para 2 -->
20616 The types declared are mbstate_t (described in <a href="#7.29.1">7.29.1</a>) and size_t (described in
20618 <pre>
20619 char16_t
20620 </pre>
20621 which is an unsigned integer type used for 16-bit characters and is the same type as
20623 <pre>
20624 char32_t
20625 </pre>
20626 which is an unsigned integer type used for 32-bit characters and is the same type as
20630 <h4><a name="7.27.1" href="#7.27.1">7.27.1 Restartable multibyte/wide character conversion functions</a></h4>
20631 <p><!--para 1 -->
20632 These functions have a parameter, ps, of type pointer to mbstate_t that points to an
20633 object that can completely describe the current conversion state of the associated
20634 multibyte character sequence, which the functions alter as necessary. If ps is a null
20635 pointer, each function uses its own internal mbstate_t object instead, which is
20636 initialized at program startup to the initial conversion state; the functions are not required
20637 to avoid data races in this case. The implementation behaves as if no library function
20638 calls these functions with a null pointer for ps.
20642 <p><b>Synopsis</b>
20643 <p><!--para 1 -->
20644 <pre>
20646 size_t mbrtoc16(char16_t * restrict pc16,
20647 const char * restrict s, size_t n,
20648 mbstate_t * restrict ps);
20649 </pre>
20650 <p><b>Description</b>
20651 <p><!--para 2 -->
20652 If s is a null pointer, the mbrtoc16 function is equivalent to the call:
20653 <pre>
20655 </pre>
20656 In this case, the values of the parameters pc16 and n are ignored.
20657 <p><!--para 3 -->
20658 If s is not a null pointer, the mbrtoc16 function inspects at most n bytes beginning with
20659 the byte pointed to by s to determine the number of bytes needed to complete the next
20660 multibyte character (including any shift sequences). If the function determines that the
20661 next multibyte character is complete and valid, it determines the values of the
20662 corresponding wide characters and then, if pc16 is not a null pointer, stores the value of
20663 the first (or only) such character in the object pointed to by pc16. Subsequent calls will
20664 <!--page 414 -->
20665 store successive wide characters without consuming any additional input until all the
20666 characters have been stored. If the corresponding wide character is the null wide
20667 character, the resulting state described is the initial conversion state.
20668 <p><b>Returns</b>
20669 <p><!--para 4 -->
20670 The mbrtoc16 function returns the first of the following that applies (given the current
20671 conversion state):
20672 0 if the next n or fewer bytes complete the multibyte character that
20673 <pre>
20674 corresponds to the null wide character (which is the value stored).
20675 </pre>
20676 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
20677 <pre>
20678 character (which is the value stored); the value returned is the number
20679 of bytes that complete the multibyte character.
20680 </pre>
20681 (size_t)(-3) if the next character resulting from a previous call has been stored (no
20682 <pre>
20683 bytes from the input have been consumed by this call).
20684 </pre>
20685 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
20686 <pre>
20687 multibyte character, and all n bytes have been processed (no value is
20689 </pre>
20690 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
20691 <pre>
20692 do not contribute to a complete and valid multibyte character (no
20693 value is stored); the value of the macro EILSEQ is stored in errno,
20694 and the conversion state is unspecified.
20695 </pre>
20697 <p><b>Footnotes</b>
20698 <p><small><a name="note311" href="#note311">311)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
20699 sequence of redundant shift sequences (for implementations with state-dependent encodings).
20700 </small>
20704 <p><b>Synopsis</b>
20705 <p><!--para 1 -->
20706 <pre>
20708 size_t c16rtomb(char * restrict s, char16_t c16,
20709 mbstate_t * restrict ps);
20710 </pre>
20711 <p><b>Description</b>
20712 <p><!--para 2 -->
20713 If s is a null pointer, the c16rtomb function is equivalent to the call
20714 <pre>
20715 c16rtomb(buf, L'\0', ps)
20716 </pre>
20717 where buf is an internal buffer.
20718 <p><!--para 3 -->
20719 If s is not a null pointer, the c16rtomb function determines the number of bytes needed
20720 to represent the multibyte character that corresponds to the wide character given by c16
20721 (including any shift sequences), and stores the multibyte character representation in the
20724 <!--page 415 -->
20725 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
20726 c16 is a null wide character, a null byte is stored, preceded by any shift sequence needed
20727 to restore the initial shift state; the resulting state described is the initial conversion state.
20728 <p><b>Returns</b>
20729 <p><!--para 4 -->
20730 The c16rtomb function returns the number of bytes stored in the array object (including
20731 any shift sequences). When c16 is not a valid wide character, an encoding error occurs:
20732 the function stores the value of the macro EILSEQ in errno and returns
20733 (size_t)(-1); the conversion state is unspecified.
20737 <p><b>Synopsis</b>
20738 <p><!--para 1 -->
20739 <pre>
20741 size_t mbrtoc32(char32_t * restrict pc32,
20742 const char * restrict s, size_t n,
20743 mbstate_t * restrict ps);
20744 </pre>
20745 <p><b>Description</b>
20746 <p><!--para 2 -->
20747 If s is a null pointer, the mbrtoc32 function is equivalent to the call:
20748 <pre>
20750 </pre>
20751 In this case, the values of the parameters pc32 and n are ignored.
20752 <p><!--para 3 -->
20753 If s is not a null pointer, the mbrtoc32 function inspects at most n bytes beginning with
20754 the byte pointed to by s to determine the number of bytes needed to complete the next
20755 multibyte character (including any shift sequences). If the function determines that the
20756 next multibyte character is complete and valid, it determines the values of the
20757 corresponding wide characters and then, if pc32 is not a null pointer, stores the value of
20758 the first (or only) such character in the object pointed to by pc32. Subsequent calls will
20759 store successive wide characters without consuming any additional input until all the
20760 characters have been stored. If the corresponding wide character is the null wide
20761 character, the resulting state described is the initial conversion state.
20762 <p><b>Returns</b>
20763 <p><!--para 4 -->
20764 The mbrtoc32 function returns the first of the following that applies (given the current
20765 conversion state):
20766 0 if the next n or fewer bytes complete the multibyte character that
20767 <pre>
20768 corresponds to the null wide character (which is the value stored).
20769 </pre>
20770 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
20771 <!--page 416 -->
20772 <pre>
20773 character (which is the value stored); the value returned is the number
20774 of bytes that complete the multibyte character.
20775 </pre>
20776 (size_t)(-3) if the next character resulting from a previous call has been stored (no
20777 <pre>
20778 bytes from the input have been consumed by this call).
20779 </pre>
20780 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
20781 <pre>
20782 multibyte character, and all n bytes have been processed (no value is
20784 </pre>
20785 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
20786 <pre>
20787 do not contribute to a complete and valid multibyte character (no
20788 value is stored); the value of the macro EILSEQ is stored in errno,
20789 and the conversion state is unspecified.
20790 </pre>
20792 <p><b>Footnotes</b>
20793 <p><small><a name="note312" href="#note312">312)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
20794 sequence of redundant shift sequences (for implementations with state-dependent encodings).
20795 </small>
20799 <p><b>Synopsis</b>
20800 <p><!--para 1 -->
20801 <pre>
20803 size_t c32rtomb(char * restrict s, char32_t c32,
20804 mbstate_t * restrict ps);
20805 </pre>
20806 <p><b>Description</b>
20807 <p><!--para 2 -->
20808 If s is a null pointer, the c32rtomb function is equivalent to the call
20809 <pre>
20810 c32rtomb(buf, L'\0', ps)
20811 </pre>
20812 where buf is an internal buffer.
20813 <p><!--para 3 -->
20814 If s is not a null pointer, the c32rtomb function determines the number of bytes needed
20815 to represent the multibyte character that corresponds to the wide character given by c32
20816 (including any shift sequences), and stores the multibyte character representation in the
20817 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
20818 c32 is a null wide character, a null byte is stored, preceded by any shift sequence needed
20819 to restore the initial shift state; the resulting state described is the initial conversion state.
20820 <p><b>Returns</b>
20821 <p><!--para 4 -->
20822 The c32rtomb function returns the number of bytes stored in the array object (including
20823 any shift sequences). When c32 is not a valid wide character, an encoding error occurs:
20824 the function stores the value of the macro EILSEQ in errno and returns
20825 (size_t)(-1); the conversion state is unspecified.
20830 <!--page 417 -->
20833 <h3><a name="7.28" href="#7.28">7.28 Extended multibyte and wide character utilities <wchar.h></a></h3>
20837 <p><!--para 1 -->
20838 The header <a href="#7.28"><wchar.h></a> defines four macros, and declares four data types, one tag, and
20840 <p><!--para 2 -->
20842 <pre>
20843 mbstate_t
20844 </pre>
20845 which is a complete object type other than an array type that can hold the conversion state
20846 information necessary to convert between sequences of multibyte characters and wide
20847 characters;
20848 <pre>
20849 wint_t
20850 </pre>
20851 which is an integer type unchanged by default argument promotions that can hold any
20852 value corresponding to members of the extended character set, as well as at least one
20853 value that does not correspond to any member of the extended character set (see WEOF
20855 <pre>
20856 struct tm
20857 </pre>
20858 which is declared as an incomplete structure type (the contents are described in <a href="#7.26.1">7.26.1</a>).
20859 <p><!--para 3 -->
20862 <pre>
20863 WEOF
20864 </pre>
20865 which expands to a constant expression of type wint_t whose value does not
20866 correspond to any member of the extended character set.<sup><a href="#note315"><b>315)</b></a></sup> It is accepted (and returned)
20867 by several functions in this subclause to indicate end-of-file, that is, no more input from a
20868 stream. It is also used as a wide character value that does not correspond to any member
20869 of the extended character set.
20870 <p><!--para 4 -->
20871 The functions declared are grouped as follows:
20872 <ul>
20873 <li> Functions that perform input and output of wide characters, or multibyte characters,
20874 or both;
20875 <li> Functions that provide wide string numeric conversion;
20876 <li> Functions that perform general wide string manipulation;
20879 <!--page 418 -->
20880 <li> Functions for wide string date and time conversion; and
20881 <li> Functions that provide extended capabilities for conversion between multibyte and
20882 wide character sequences.
20883 </ul>
20884 <p><!--para 5 -->
20885 Unless explicitly stated otherwise, if the execution of a function described in this
20886 subclause causes copying to take place between objects that overlap, the behavior is
20887 undefined.
20889 <p><b>Footnotes</b>
20890 <p><small><a name="note313" href="#note313">313)</a> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
20891 </small>
20892 <p><small><a name="note314" href="#note314">314)</a> wchar_t and wint_t can be the same integer type.
20893 </small>
20894 <p><small><a name="note315" href="#note315">315)</a> The value of the macro WEOF may differ from that of EOF and need not be negative.
20895 </small>
20898 <h4><a name="7.28.2" href="#7.28.2">7.28.2 Formatted wide character input/output functions</a></h4>
20899 <p><!--para 1 -->
20900 The formatted wide character input/output functions shall behave as if there is a sequence
20901 point after the actions associated with each specifier.<sup><a href="#note316"><b>316)</b></a></sup>
20903 <p><b>Footnotes</b>
20904 <p><small><a name="note316" href="#note316">316)</a> The fwprintf functions perform writes to memory for the %n specifier.
20905 </small>
20909 <p><b>Synopsis</b>
20910 <p><!--para 1 -->
20911 <pre>
20914 int fwprintf(FILE * restrict stream,
20915 const wchar_t * restrict format, ...);
20916 </pre>
20917 <p><b>Description</b>
20918 <p><!--para 2 -->
20919 The fwprintf function writes output to the stream pointed to by stream, under
20920 control of the wide string pointed to by format that specifies how subsequent arguments
20921 are converted for output. If there are insufficient arguments for the format, the behavior
20922 is undefined. If the format is exhausted while arguments remain, the excess arguments
20923 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
20924 when the end of the format string is encountered.
20925 <p><!--para 3 -->
20926 The format is composed of zero or more directives: ordinary wide characters (not %),
20927 which are copied unchanged to the output stream; and conversion specifications, each of
20928 which results in fetching zero or more subsequent arguments, converting them, if
20929 applicable, according to the corresponding conversion specifier, and then writing the
20930 result to the output stream.
20931 <p><!--para 4 -->
20932 Each conversion specification is introduced by the wide character %. After the %, the
20933 following appear in sequence:
20934 <ul>
20935 <li> Zero or more flags (in any order) that modify the meaning of the conversion
20936 specification.
20937 <li> An optional minimum field width. If the converted value has fewer wide characters
20938 than the field width, it is padded with spaces (by default) on the left (or right, if the
20941 <!--page 419 -->
20942 left adjustment flag, described later, has been given) to the field width. The field
20943 width takes the form of an asterisk * (described later) or a nonnegative decimal
20945 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
20946 o, u, x, and X conversions, the number of digits to appear after the decimal-point
20947 wide character for a, A, e, E, f, and F conversions, the maximum number of
20948 significant digits for the g and G conversions, or the maximum number of wide
20949 characters to be written for s conversions. The precision takes the form of a period
20950 (.) followed either by an asterisk * (described later) or by an optional decimal
20951 integer; if only the period is specified, the precision is taken as zero. If a precision
20952 appears with any other conversion specifier, the behavior is undefined.
20953 <li> An optional length modifier that specifies the size of the argument.
20954 <li> A conversion specifier wide character that specifies the type of conversion to be
20955 applied.
20956 </ul>
20957 <p><!--para 5 -->
20958 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
20959 this case, an int argument supplies the field width or precision. The arguments
20960 specifying field width, or precision, or both, shall appear (in that order) before the
20961 argument (if any) to be converted. A negative field width argument is taken as a - flag
20962 followed by a positive field width. A negative precision argument is taken as if the
20963 precision were omitted.
20964 <p><!--para 6 -->
20965 The flag wide characters and their meanings are:
20966 - The result of the conversion is left-justified within the field. (It is right-justified if
20967 <pre>
20968 this flag is not specified.)
20969 </pre>
20970 + The result of a signed conversion always begins with a plus or minus sign. (It
20971 <pre>
20972 begins with a sign only when a negative value is converted if this flag is not
20974 </pre>
20975 space If the first wide character of a signed conversion is not a sign, or if a signed
20976 <pre>
20977 conversion results in no wide characters, a space is prefixed to the result. If the
20978 space and + flags both appear, the space flag is ignored.
20979 </pre>
20980 # The result is converted to an ''alternative form''. For o conversion, it increases
20981 <pre>
20982 the precision, if and only if necessary, to force the first digit of the result to be a
20983 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
20984 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
20985 </pre>
20988 <!--page 420 -->
20989 <pre>
20990 and G conversions, the result of converting a floating-point number always
20991 contains a decimal-point wide character, even if no digits follow it. (Normally, a
20992 decimal-point wide character appears in the result of these conversions only if a
20993 digit follows it.) For g and G conversions, trailing zeros are not removed from the
20994 result. For other conversions, the behavior is undefined.
20995 </pre>
20996 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
20997 <pre>
20998 (following any indication of sign or base) are used to pad to the field width rather
20999 than performing space padding, except when converting an infinity or NaN. If the
21000 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
21001 conversions, if a precision is specified, the 0 flag is ignored. For other
21002 conversions, the behavior is undefined.
21003 </pre>
21004 <p><!--para 7 -->
21005 The length modifiers and their meanings are:
21006 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21007 <pre>
21008 signed char or unsigned char argument (the argument will have
21009 been promoted according to the integer promotions, but its value shall be
21010 converted to signed char or unsigned char before printing); or that
21011 a following n conversion specifier applies to a pointer to a signed char
21012 argument.
21013 </pre>
21014 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21015 <pre>
21016 short int or unsigned short int argument (the argument will
21017 have been promoted according to the integer promotions, but its value shall
21018 be converted to short int or unsigned short int before printing);
21019 or that a following n conversion specifier applies to a pointer to a short
21020 int argument.
21021 </pre>
21022 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21023 <pre>
21024 long int or unsigned long int argument; that a following n
21025 conversion specifier applies to a pointer to a long int argument; that a
21026 following c conversion specifier applies to a wint_t argument; that a
21027 following s conversion specifier applies to a pointer to a wchar_t
21028 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
21029 specifier.
21030 </pre>
21031 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21032 <pre>
21033 long long int or unsigned long long int argument; or that a
21034 following n conversion specifier applies to a pointer to a long long int
21035 argument.
21036 </pre>
21037 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
21038 <!--page 421 -->
21039 <pre>
21040 an intmax_t or uintmax_t argument; or that a following n conversion
21041 specifier applies to a pointer to an intmax_t argument.
21042 </pre>
21043 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21044 <pre>
21045 size_t or the corresponding signed integer type argument; or that a
21046 following n conversion specifier applies to a pointer to a signed integer type
21047 corresponding to size_t argument.
21048 </pre>
21049 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
21050 <pre>
21051 ptrdiff_t or the corresponding unsigned integer type argument; or that a
21052 following n conversion specifier applies to a pointer to a ptrdiff_t
21053 argument.
21054 </pre>
21055 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
21056 <pre>
21057 applies to a long double argument.
21058 </pre>
21059 If a length modifier appears with any conversion specifier other than as specified above,
21060 the behavior is undefined.
21061 <p><!--para 8 -->
21062 The conversion specifiers and their meanings are:
21063 d,i The int argument is converted to signed decimal in the style [-]dddd. The
21064 <pre>
21065 precision specifies the minimum number of digits to appear; if the value
21066 being converted can be represented in fewer digits, it is expanded with
21067 leading zeros. The default precision is 1. The result of converting a zero
21068 value with a precision of zero is no wide characters.
21069 </pre>
21070 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
21071 <pre>
21072 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
21073 letters abcdef are used for x conversion and the letters ABCDEF for X
21074 conversion. The precision specifies the minimum number of digits to appear;
21075 if the value being converted can be represented in fewer digits, it is expanded
21076 with leading zeros. The default precision is 1. The result of converting a
21077 zero value with a precision of zero is no wide characters.
21078 </pre>
21079 f,F A double argument representing a floating-point number is converted to
21080 <!--page 422 -->
21081 <pre>
21082 decimal notation in the style [-]ddd.ddd, where the number of digits after
21083 the decimal-point wide character is equal to the precision specification. If the
21084 precision is missing, it is taken as 6; if the precision is zero and the # flag is
21085 not specified, no decimal-point wide character appears. If a decimal-point
21086 wide character appears, at least one digit appears before it. The value is
21087 rounded to the appropriate number of digits.
21088 A double argument representing an infinity is converted in one of the styles
21089 [-]inf or [-]infinity -- which style is implementation-defined. A
21090 double argument representing a NaN is converted in one of the styles
21091 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
21092 any n-wchar-sequence, is implementation-defined. The F conversion
21093 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
21095 </pre>
21096 e,E A double argument representing a floating-point number is converted in the
21097 <pre>
21098 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
21099 argument is nonzero) before the decimal-point wide character and the number
21100 of digits after it is equal to the precision; if the precision is missing, it is taken
21101 as 6; if the precision is zero and the # flag is not specified, no decimal-point
21102 wide character appears. The value is rounded to the appropriate number of
21103 digits. The E conversion specifier produces a number with E instead of e
21104 introducing the exponent. The exponent always contains at least two digits,
21105 and only as many more digits as necessary to represent the exponent. If the
21106 value is zero, the exponent is zero.
21107 A double argument representing an infinity or NaN is converted in the style
21108 of an f or F conversion specifier.
21109 </pre>
21110 g,G A double argument representing a floating-point number is converted in
21111 <pre>
21112 style f or e (or in style F or E in the case of a G conversion specifier),
21113 depending on the value converted and the precision. Let P equal the
21114 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
21115 Then, if a conversion with style E would have an exponent of X:
21116 -- if P > X >= -4, the conversion is with style f (or F) and precision
21117 P - (X + 1).
21118 -- otherwise, the conversion is with style e (or E) and precision P - 1.
21119 Finally, unless the # flag is used, any trailing zeros are removed from the
21120 fractional portion of the result and the decimal-point wide character is
21121 removed if there is no fractional portion remaining.
21122 A double argument representing an infinity or NaN is converted in the style
21123 of an f or F conversion specifier.
21124 </pre>
21125 a,A A double argument representing a floating-point number is converted in the
21126 <pre>
21127 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
21128 nonzero if the argument is a normalized floating-point number and is
21129 otherwise unspecified) before the decimal-point wide character<sup><a href="#note320"><b>320)</b></a></sup> and the
21130 number of hexadecimal digits after it is equal to the precision; if the precision
21131 is missing and FLT_RADIX is a power of 2, then the precision is sufficient
21132 </pre>
21135 <!--page 423 -->
21136 <pre>
21137 for an exact representation of the value; if the precision is missing and
21138 FLT_RADIX is not a power of 2, then the precision is sufficient to
21139 distinguish<sup><a href="#note321"><b>321)</b></a></sup> values of type double, except that trailing zeros may be
21140 omitted; if the precision is zero and the # flag is not specified, no decimal-
21141 point wide character appears. The letters abcdef are used for a conversion
21142 and the letters ABCDEF for A conversion. The A conversion specifier
21143 produces a number with X and P instead of x and p. The exponent always
21144 contains at least one digit, and only as many more digits as necessary to
21145 represent the decimal exponent of 2. If the value is zero, the exponent is
21146 zero.
21147 A double argument representing an infinity or NaN is converted in the style
21148 of an f or F conversion specifier.
21149 </pre>
21150 c If no l length modifier is present, the int argument is converted to a wide
21151 <pre>
21152 character as if by calling btowc and the resulting wide character is written.
21153 If an l length modifier is present, the wint_t argument is converted to
21154 wchar_t and written.
21155 </pre>
21156 s If no l length modifier is present, the argument shall be a pointer to the initial
21157 <pre>
21158 element of a character array containing a multibyte character sequence
21159 beginning in the initial shift state. Characters from the array are converted as
21160 if by repeated calls to the mbrtowc function, with the conversion state
21161 described by an mbstate_t object initialized to zero before the first
21162 multibyte character is converted, and written up to (but not including) the
21163 terminating null wide character. If the precision is specified, no more than
21164 that many wide characters are written. If the precision is not specified or is
21165 greater than the size of the converted array, the converted array shall contain a
21166 null wide character.
21167 If an l length modifier is present, the argument shall be a pointer to the initial
21168 element of an array of wchar_t type. Wide characters from the array are
21169 written up to (but not including) a terminating null wide character. If the
21170 precision is specified, no more than that many wide characters are written. If
21171 the precision is not specified or is greater than the size of the array, the array
21172 shall contain a null wide character.
21173 </pre>
21174 p The argument shall be a pointer to void. The value of the pointer is
21175 <pre>
21176 converted to a sequence of printing wide characters, in an implementation-
21177 </pre>
21179 <!--page 424 -->
21180 <pre>
21181 defined manner.
21182 </pre>
21183 n The argument shall be a pointer to signed integer into which is written the
21184 <pre>
21185 number of wide characters written to the output stream so far by this call to
21186 fwprintf. No argument is converted, but one is consumed. If the
21187 conversion specification includes any flags, a field width, or a precision, the
21188 behavior is undefined.
21189 </pre>
21190 % A % wide character is written. No argument is converted. The complete
21191 <pre>
21192 conversion specification shall be %%.
21193 </pre>
21194 <p><!--para 9 -->
21195 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note322"><b>322)</b></a></sup> If any argument is
21196 not the correct type for the corresponding conversion specification, the behavior is
21197 undefined.
21198 <p><!--para 10 -->
21199 In no case does a nonexistent or small field width cause truncation of a field; if the result
21200 of a conversion is wider than the field width, the field is expanded to contain the
21201 conversion result.
21202 <p><!--para 11 -->
21203 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
21204 to a hexadecimal floating number with the given precision.
21205 <p><b>Recommended practice</b>
21206 <p><!--para 12 -->
21207 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
21208 representable in the given precision, the result should be one of the two adjacent numbers
21209 in hexadecimal floating style with the given precision, with the extra stipulation that the
21210 error should have a correct sign for the current rounding direction.
21211 <p><!--para 13 -->
21212 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
21213 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note323"><b>323)</b></a></sup> If the number of
21214 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
21215 representable with DECIMAL_DIG digits, then the result should be an exact
21216 representation with trailing zeros. Otherwise, the source value is bounded by two
21217 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
21218 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
21219 the error should have a correct sign for the current rounding direction.
21220 <p><b>Returns</b>
21221 <p><!--para 14 -->
21222 The fwprintf function returns the number of wide characters transmitted, or a negative
21223 value if an output or encoding error occurred.
21225 <!--page 425 -->
21226 <p><b>Environmental limits</b>
21227 <p><!--para 15 -->
21228 The number of wide characters that can be produced by any single conversion shall be at
21229 least 4095.
21230 <p><!--para 16 -->
21231 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
21232 places:
21233 <pre>
21237 /* ... */
21238 wchar_t *weekday, *month; // pointers to wide strings
21239 int day, hour, min;
21241 weekday, month, day, hour, min);
21243 </pre>
21245 <p><b> Forward references</b>: the btowc function (<a href="#7.28.6.1.1">7.28.6.1.1</a>), the mbrtowc function
21248 <p><b>Footnotes</b>
21249 <p><small><a name="note317" href="#note317">317)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
21250 </small>
21251 <p><small><a name="note318" href="#note318">318)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
21252 include a minus sign.
21253 </small>
21254 <p><small><a name="note319" href="#note319">319)</a> When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
21255 meaning; the # and 0 flag wide characters have no effect.
21256 </small>
21257 <p><small><a name="note320" href="#note320">320)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
21258 character so that subsequent digits align to nibble (4-bit) boundaries.
21259 </small>
21260 <p><small><a name="note321" href="#note321">321)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
21261 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
21262 might suffice depending on the implementation's scheme for determining the digit to the left of the
21263 decimal-point wide character.
21264 </small>
21265 <p><small><a name="note322" href="#note322">322)</a> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
21266 </small>
21267 <p><small><a name="note323" href="#note323">323)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
21268 given format specifier. The number of significant digits is determined by the format specifier, and in
21269 the case of fixed-point conversion by the source value as well.
21270 </small>
21274 <p><b>Synopsis</b>
21275 <p><!--para 1 -->
21276 <pre>
21279 int fwscanf(FILE * restrict stream,
21280 const wchar_t * restrict format, ...);
21281 </pre>
21282 <p><b>Description</b>
21283 <p><!--para 2 -->
21284 The fwscanf function reads input from the stream pointed to by stream, under
21285 control of the wide string pointed to by format that specifies the admissible input
21286 sequences and how they are to be converted for assignment, using subsequent arguments
21287 as pointers to the objects to receive the converted input. If there are insufficient
21288 arguments for the format, the behavior is undefined. If the format is exhausted while
21289 arguments remain, the excess arguments are evaluated (as always) but are otherwise
21290 ignored.
21291 <p><!--para 3 -->
21292 The format is composed of zero or more directives: one or more white-space wide
21293 characters, an ordinary wide character (neither % nor a white-space wide character), or a
21294 conversion specification. Each conversion specification is introduced by the wide
21295 character %. After the %, the following appear in sequence:
21296 <ul>
21297 <li> An optional assignment-suppressing wide character *.
21298 <li> An optional decimal integer greater than zero that specifies the maximum field width
21299 (in wide characters).
21300 <!--page 426 -->
21301 <li> An optional length modifier that specifies the size of the receiving object.
21302 <li> A conversion specifier wide character that specifies the type of conversion to be
21303 applied.
21304 </ul>
21305 <p><!--para 4 -->
21306 The fwscanf function executes each directive of the format in turn. When all directives
21307 have been executed, or if a directive fails (as detailed below), the function returns.
21308 Failures are described as input failures (due to the occurrence of an encoding error or the
21309 unavailability of input characters), or matching failures (due to inappropriate input).
21310 <p><!--para 5 -->
21311 A directive composed of white-space wide character(s) is executed by reading input up to
21312 the first non-white-space wide character (which remains unread), or until no more wide
21313 characters can be read.
21314 <p><!--para 6 -->
21315 A directive that is an ordinary wide character is executed by reading the next wide
21316 character of the stream. If that wide character differs from the directive, the directive
21317 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
21318 of-file, an encoding error, or a read error prevents a wide character from being read, the
21319 directive fails.
21320 <p><!--para 7 -->
21321 A directive that is a conversion specification defines a set of matching input sequences, as
21322 described below for each specifier. A conversion specification is executed in the
21323 following steps:
21324 <p><!--para 8 -->
21325 Input white-space wide characters (as specified by the iswspace function) are skipped,
21326 unless the specification includes a [, c, or n specifier.<sup><a href="#note324"><b>324)</b></a></sup>
21327 <p><!--para 9 -->
21328 An input item is read from the stream, unless the specification includes an n specifier. An
21329 input item is defined as the longest sequence of input wide characters which does not
21330 exceed any specified field width and which is, or is a prefix of, a matching input
21331 sequence.<sup><a href="#note325"><b>325)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
21332 length of the input item is zero, the execution of the directive fails; this condition is a
21333 matching failure unless end-of-file, an encoding error, or a read error prevented input
21334 from the stream, in which case it is an input failure.
21335 <p><!--para 10 -->
21336 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
21337 count of input wide characters) is converted to a type appropriate to the conversion
21338 specifier. If the input item is not a matching sequence, the execution of the directive fails:
21339 this condition is a matching failure. Unless assignment suppression was indicated by a *,
21340 the result of the conversion is placed in the object pointed to by the first argument
21341 following the format argument that has not already received a conversion result. If this
21344 <!--page 427 -->
21345 object does not have an appropriate type, or if the result of the conversion cannot be
21346 represented in the object, the behavior is undefined.
21347 <p><!--para 11 -->
21348 The length modifiers and their meanings are:
21349 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21350 <pre>
21351 to an argument with type pointer to signed char or unsigned char.
21352 </pre>
21353 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21354 <pre>
21355 to an argument with type pointer to short int or unsigned short
21356 int.
21357 </pre>
21358 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21359 <pre>
21360 to an argument with type pointer to long int or unsigned long
21361 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
21362 an argument with type pointer to double; or that a following c, s, or [
21363 conversion specifier applies to an argument with type pointer to wchar_t.
21364 </pre>
21365 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21366 <pre>
21367 to an argument with type pointer to long long int or unsigned
21368 long long int.
21369 </pre>
21370 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21371 <pre>
21372 to an argument with type pointer to intmax_t or uintmax_t.
21373 </pre>
21374 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21375 <pre>
21376 to an argument with type pointer to size_t or the corresponding signed
21377 integer type.
21378 </pre>
21379 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
21380 <pre>
21381 to an argument with type pointer to ptrdiff_t or the corresponding
21382 unsigned integer type.
21383 </pre>
21384 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
21385 <pre>
21386 applies to an argument with type pointer to long double.
21387 </pre>
21388 If a length modifier appears with any conversion specifier other than as specified above,
21389 the behavior is undefined.
21390 <p><!--para 12 -->
21391 The conversion specifiers and their meanings are:
21392 d Matches an optionally signed decimal integer, whose format is the same as
21393 <pre>
21394 expected for the subject sequence of the wcstol function with the value 10
21395 for the base argument. The corresponding argument shall be a pointer to
21396 signed integer.
21397 </pre>
21398 i Matches an optionally signed integer, whose format is the same as expected
21399 <!--page 428 -->
21400 <pre>
21401 for the subject sequence of the wcstol function with the value 0 for the
21402 base argument. The corresponding argument shall be a pointer to signed
21403 integer.
21404 </pre>
21405 o Matches an optionally signed octal integer, whose format is the same as
21406 <pre>
21407 expected for the subject sequence of the wcstoul function with the value 8
21408 for the base argument. The corresponding argument shall be a pointer to
21409 unsigned integer.
21410 </pre>
21411 u Matches an optionally signed decimal integer, whose format is the same as
21412 <pre>
21413 expected for the subject sequence of the wcstoul function with the value 10
21414 for the base argument. The corresponding argument shall be a pointer to
21415 unsigned integer.
21416 </pre>
21417 x Matches an optionally signed hexadecimal integer, whose format is the same
21418 <pre>
21419 as expected for the subject sequence of the wcstoul function with the value
21420 16 for the base argument. The corresponding argument shall be a pointer to
21421 unsigned integer.
21422 </pre>
21423 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
21424 <pre>
21425 format is the same as expected for the subject sequence of the wcstod
21426 function. The corresponding argument shall be a pointer to floating.
21427 </pre>
21428 c Matches a sequence of wide characters of exactly the number specified by the
21429 <pre>
21430 field width (1 if no field width is present in the directive).
21431 If no l length modifier is present, characters from the input field are
21432 converted as if by repeated calls to the wcrtomb function, with the
21433 conversion state described by an mbstate_t object initialized to zero
21434 before the first wide character is converted. The corresponding argument
21435 shall be a pointer to the initial element of a character array large enough to
21436 accept the sequence. No null character is added.
21437 If an l length modifier is present, the corresponding argument shall be a
21438 pointer to the initial element of an array of wchar_t large enough to accept
21439 the sequence. No null wide character is added.
21440 </pre>
21441 s Matches a sequence of non-white-space wide characters.
21442 <!--page 429 -->
21443 <pre>
21444 If no l length modifier is present, characters from the input field are
21445 converted as if by repeated calls to the wcrtomb function, with the
21446 conversion state described by an mbstate_t object initialized to zero
21447 before the first wide character is converted. The corresponding argument
21448 shall be a pointer to the initial element of a character array large enough to
21449 accept the sequence and a terminating null character, which will be added
21450 automatically.
21451 If an l length modifier is present, the corresponding argument shall be a
21452 pointer to the initial element of an array of wchar_t large enough to accept
21453 the sequence and the terminating null wide character, which will be added
21454 automatically.
21455 </pre>
21456 [ Matches a nonempty sequence of wide characters from a set of expected
21457 <pre>
21458 characters (the scanset).
21459 If no l length modifier is present, characters from the input field are
21460 converted as if by repeated calls to the wcrtomb function, with the
21461 conversion state described by an mbstate_t object initialized to zero
21462 before the first wide character is converted. The corresponding argument
21463 shall be a pointer to the initial element of a character array large enough to
21464 accept the sequence and a terminating null character, which will be added
21465 automatically.
21466 If an l length modifier is present, the corresponding argument shall be a
21467 pointer to the initial element of an array of wchar_t large enough to accept
21468 the sequence and the terminating null wide character, which will be added
21469 automatically.
21470 The conversion specifier includes all subsequent wide characters in the
21471 format string, up to and including the matching right bracket (]). The wide
21472 characters between the brackets (the scanlist) compose the scanset, unless the
21473 wide character after the left bracket is a circumflex (^), in which case the
21474 scanset contains all wide characters that do not appear in the scanlist between
21475 the circumflex and the right bracket. If the conversion specifier begins with
21476 [] or [^], the right bracket wide character is in the scanlist and the next
21477 following right bracket wide character is the matching right bracket that ends
21478 the specification; otherwise the first following right bracket wide character is
21479 the one that ends the specification. If a - wide character is in the scanlist and
21480 is not the first, nor the second where the first wide character is a ^, nor the
21481 last character, the behavior is implementation-defined.
21482 </pre>
21483 p Matches an implementation-defined set of sequences, which should be the
21484 <pre>
21485 same as the set of sequences that may be produced by the %p conversion of
21486 the fwprintf function. The corresponding argument shall be a pointer to a
21487 pointer to void. The input item is converted to a pointer value in an
21488 implementation-defined manner. If the input item is a value converted earlier
21489 during the same program execution, the pointer that results shall compare
21490 equal to that value; otherwise the behavior of the %p conversion is undefined.
21491 </pre>
21492 n No input is consumed. The corresponding argument shall be a pointer to
21493 <!--page 430 -->
21494 <pre>
21495 signed integer into which is to be written the number of wide characters read
21496 from the input stream so far by this call to the fwscanf function. Execution
21497 of a %n directive does not increment the assignment count returned at the
21498 completion of execution of the fwscanf function. No argument is
21499 converted, but one is consumed. If the conversion specification includes an
21500 assignment-suppressing wide character or a field width, the behavior is
21501 undefined.
21502 </pre>
21503 % Matches a single % wide character; no conversion or assignment occurs. The
21504 <pre>
21505 complete conversion specification shall be %%.
21506 </pre>
21507 <p><!--para 13 -->
21508 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note326"><b>326)</b></a></sup>
21509 <p><!--para 14 -->
21510 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
21511 respectively, a, e, f, g, and x.
21512 <p><!--para 15 -->
21513 Trailing white space (including new-line wide characters) is left unread unless matched
21514 by a directive. The success of literal matches and suppressed assignments is not directly
21515 determinable other than via the %n directive.
21516 <p><b>Returns</b>
21517 <p><!--para 16 -->
21518 The fwscanf function returns the value of the macro EOF if an input failure occurs
21519 before the first conversion (if any) has completed. Otherwise, the function returns the
21520 number of input items assigned, which can be fewer than provided for, or even zero, in
21521 the event of an early matching failure.
21522 <p><!--para 17 -->
21523 EXAMPLE 1 The call:
21524 <pre>
21527 /* ... */
21528 int n, i; float x; wchar_t name[50];
21530 </pre>
21531 with the input line:
21532 <pre>
21533 25 54.32E-1 thompson
21534 </pre>
21535 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
21536 thompson\0.
21538 <p><!--para 18 -->
21539 EXAMPLE 2 The call:
21540 <pre>
21543 /* ... */
21544 int i; float x; double y;
21546 </pre>
21547 with input:
21548 <pre>
21549 56789 0123 56a72
21550 </pre>
21551 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
21552 56.0. The next wide character read from the input stream will be a.
21555 <!--page 431 -->
21556 <p><b> Forward references</b>: the wcstod, wcstof, and wcstold functions (<a href="#7.28.4.1.1">7.28.4.1.1</a>), the
21557 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.28.4.1.2">7.28.4.1.2</a>), the wcrtomb
21560 <p><b>Footnotes</b>
21561 <p><small><a name="note324" href="#note324">324)</a> These white-space wide characters are not counted against a specified field width.
21562 </small>
21563 <p><small><a name="note325" href="#note325">325)</a> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
21564 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
21565 </small>
21566 <p><small><a name="note326" href="#note326">326)</a> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
21567 </small>
21571 <p><b>Synopsis</b>
21572 <p><!--para 1 -->
21573 <pre>
21575 int swprintf(wchar_t * restrict s,
21576 size_t n,
21577 const wchar_t * restrict format, ...);
21578 </pre>
21579 <p><b>Description</b>
21580 <p><!--para 2 -->
21581 The swprintf function is equivalent to fwprintf, except that the argument s
21582 specifies an array of wide characters into which the generated output is to be written,
21583 rather than written to a stream. No more than n wide characters are written, including a
21584 terminating null wide character, which is always added (unless n is zero).
21585 <p><b>Returns</b>
21586 <p><!--para 3 -->
21587 The swprintf function returns the number of wide characters written in the array, not
21588 counting the terminating null wide character, or a negative value if an encoding error
21589 occurred or if n or more wide characters were requested to be written.
21593 <p><b>Synopsis</b>
21594 <p><!--para 1 -->
21595 <pre>
21597 int swscanf(const wchar_t * restrict s,
21598 const wchar_t * restrict format, ...);
21599 </pre>
21600 <p><b>Description</b>
21601 <p><!--para 2 -->
21602 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
21603 wide string from which the input is to be obtained, rather than from a stream. Reaching
21604 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
21605 function.
21606 <p><b>Returns</b>
21607 <p><!--para 3 -->
21608 The swscanf function returns the value of the macro EOF if an input failure occurs
21609 before the first conversion (if any) has completed. Otherwise, the swscanf function
21610 returns the number of input items assigned, which can be fewer than provided for, or even
21611 zero, in the event of an early matching failure.
21612 <!--page 432 -->
21616 <p><b>Synopsis</b>
21617 <p><!--para 1 -->
21618 <pre>
21622 int vfwprintf(FILE * restrict stream,
21623 const wchar_t * restrict format,
21624 va_list arg);
21625 </pre>
21626 <p><b>Description</b>
21627 <p><!--para 2 -->
21628 The vfwprintf function is equivalent to fwprintf, with the variable argument list
21629 replaced by arg, which shall have been initialized by the va_start macro (and
21630 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
21632 <p><b>Returns</b>
21633 <p><!--para 3 -->
21634 The vfwprintf function returns the number of wide characters transmitted, or a
21635 negative value if an output or encoding error occurred.
21636 <p><!--para 4 -->
21637 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
21638 routine.
21639 <pre>
21643 void error(char *function_name, wchar_t *format, ...)
21644 {
21645 va_list args;
21646 va_start(args, format);
21647 // print out name of function causing error
21649 // print out remainder of message
21650 vfwprintf(stderr, format, args);
21651 va_end(args);
21652 }
21653 </pre>
21658 <!--page 433 -->
21660 <p><b>Footnotes</b>
21661 <p><small><a name="note327" href="#note327">327)</a> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
21662 invoke the va_arg macro, the value of arg after the return is indeterminate.
21663 </small>
21667 <p><b>Synopsis</b>
21668 <p><!--para 1 -->
21669 <pre>
21673 int vfwscanf(FILE * restrict stream,
21674 const wchar_t * restrict format,
21675 va_list arg);
21676 </pre>
21677 <p><b>Description</b>
21678 <p><!--para 2 -->
21679 The vfwscanf function is equivalent to fwscanf, with the variable argument list
21680 replaced by arg, which shall have been initialized by the va_start macro (and
21681 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
21683 <p><b>Returns</b>
21684 <p><!--para 3 -->
21685 The vfwscanf function returns the value of the macro EOF if an input failure occurs
21686 before the first conversion (if any) has completed. Otherwise, the vfwscanf function
21687 returns the number of input items assigned, which can be fewer than provided for, or even
21688 zero, in the event of an early matching failure.
21692 <p><b>Synopsis</b>
21693 <p><!--para 1 -->
21694 <pre>
21697 int vswprintf(wchar_t * restrict s,
21698 size_t n,
21699 const wchar_t * restrict format,
21700 va_list arg);
21701 </pre>
21702 <p><b>Description</b>
21703 <p><!--para 2 -->
21704 The vswprintf function is equivalent to swprintf, with the variable argument list
21705 replaced by arg, which shall have been initialized by the va_start macro (and
21706 possibly subsequent va_arg calls). The vswprintf function does not invoke the
21708 <p><b>Returns</b>
21709 <p><!--para 3 -->
21710 The vswprintf function returns the number of wide characters written in the array, not
21711 counting the terminating null wide character, or a negative value if an encoding error
21712 occurred or if n or more wide characters were requested to be generated.
21713 <!--page 434 -->
21717 <p><b>Synopsis</b>
21718 <p><!--para 1 -->
21719 <pre>
21722 int vswscanf(const wchar_t * restrict s,
21723 const wchar_t * restrict format,
21724 va_list arg);
21725 </pre>
21726 <p><b>Description</b>
21727 <p><!--para 2 -->
21728 The vswscanf function is equivalent to swscanf, with the variable argument list
21729 replaced by arg, which shall have been initialized by the va_start macro (and
21730 possibly subsequent va_arg calls). The vswscanf function does not invoke the
21732 <p><b>Returns</b>
21733 <p><!--para 3 -->
21734 The vswscanf function returns the value of the macro EOF if an input failure occurs
21735 before the first conversion (if any) has completed. Otherwise, the vswscanf function
21736 returns the number of input items assigned, which can be fewer than provided for, or even
21737 zero, in the event of an early matching failure.
21741 <p><b>Synopsis</b>
21742 <p><!--para 1 -->
21743 <pre>
21746 int vwprintf(const wchar_t * restrict format,
21747 va_list arg);
21748 </pre>
21749 <p><b>Description</b>
21750 <p><!--para 2 -->
21751 The vwprintf function is equivalent to wprintf, with the variable argument list
21752 replaced by arg, which shall have been initialized by the va_start macro (and
21753 possibly subsequent va_arg calls). The vwprintf function does not invoke the
21755 <p><b>Returns</b>
21756 <p><!--para 3 -->
21757 The vwprintf function returns the number of wide characters transmitted, or a negative
21758 value if an output or encoding error occurred.
21759 <!--page 435 -->
21763 <p><b>Synopsis</b>
21764 <p><!--para 1 -->
21765 <pre>
21768 int vwscanf(const wchar_t * restrict format,
21769 va_list arg);
21770 </pre>
21771 <p><b>Description</b>
21772 <p><!--para 2 -->
21773 The vwscanf function is equivalent to wscanf, with the variable argument list
21774 replaced by arg, which shall have been initialized by the va_start macro (and
21775 possibly subsequent va_arg calls). The vwscanf function does not invoke the
21777 <p><b>Returns</b>
21778 <p><!--para 3 -->
21779 The vwscanf function returns the value of the macro EOF if an input failure occurs
21780 before the first conversion (if any) has completed. Otherwise, the vwscanf function
21781 returns the number of input items assigned, which can be fewer than provided for, or even
21782 zero, in the event of an early matching failure.
21786 <p><b>Synopsis</b>
21787 <p><!--para 1 -->
21788 <pre>
21790 int wprintf(const wchar_t * restrict format, ...);
21791 </pre>
21792 <p><b>Description</b>
21793 <p><!--para 2 -->
21794 The wprintf function is equivalent to fwprintf with the argument stdout
21795 interposed before the arguments to wprintf.
21796 <p><b>Returns</b>
21797 <p><!--para 3 -->
21798 The wprintf function returns the number of wide characters transmitted, or a negative
21799 value if an output or encoding error occurred.
21803 <p><b>Synopsis</b>
21804 <p><!--para 1 -->
21805 <pre>
21807 int wscanf(const wchar_t * restrict format, ...);
21808 </pre>
21809 <p><b>Description</b>
21810 <p><!--para 2 -->
21811 The wscanf function is equivalent to fwscanf with the argument stdin interposed
21812 before the arguments to wscanf.
21813 <!--page 436 -->
21814 <p><b>Returns</b>
21815 <p><!--para 3 -->
21816 The wscanf function returns the value of the macro EOF if an input failure occurs
21817 before the first conversion (if any) has completed. Otherwise, the wscanf function
21818 returns the number of input items assigned, which can be fewer than provided for, or even
21819 zero, in the event of an early matching failure.
21826 <p><b>Synopsis</b>
21827 <p><!--para 1 -->
21828 <pre>
21831 wint_t fgetwc(FILE *stream);
21832 </pre>
21833 <p><b>Description</b>
21834 <p><!--para 2 -->
21835 If the end-of-file indicator for the input stream pointed to by stream is not set and a
21836 next wide character is present, the fgetwc function obtains that wide character as a
21837 wchar_t converted to a wint_t and advances the associated file position indicator for
21838 the stream (if defined).
21839 <p><b>Returns</b>
21840 <p><!--para 3 -->
21841 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
21842 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
21843 the fgetwc function returns the next wide character from the input stream pointed to by
21844 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
21845 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
21846 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note328"><b>328)</b></a></sup>
21848 <p><b>Footnotes</b>
21849 <p><small><a name="note328" href="#note328">328)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
21850 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
21851 </small>
21855 <p><b>Synopsis</b>
21856 <p><!--para 1 -->
21857 <pre>
21860 wchar_t *fgetws(wchar_t * restrict s,
21861 int n, FILE * restrict stream);
21862 </pre>
21863 <p><b>Description</b>
21864 <p><!--para 2 -->
21865 The fgetws function reads at most one less than the number of wide characters
21866 specified by n from the stream pointed to by stream into the array pointed to by s. No
21869 <!--page 437 -->
21870 additional wide characters are read after a new-line wide character (which is retained) or
21871 after end-of-file. A null wide character is written immediately after the last wide
21872 character read into the array.
21873 <p><b>Returns</b>
21874 <p><!--para 3 -->
21875 The fgetws function returns s if successful. If end-of-file is encountered and no
21876 characters have been read into the array, the contents of the array remain unchanged and a
21877 null pointer is returned. If a read or encoding error occurs during the operation, the array
21878 contents are indeterminate and a null pointer is returned.
21882 <p><b>Synopsis</b>
21883 <p><!--para 1 -->
21884 <pre>
21887 wint_t fputwc(wchar_t c, FILE *stream);
21888 </pre>
21889 <p><b>Description</b>
21890 <p><!--para 2 -->
21891 The fputwc function writes the wide character specified by c to the output stream
21892 pointed to by stream, at the position indicated by the associated file position indicator
21893 for the stream (if defined), and advances the indicator appropriately. If the file cannot
21894 support positioning requests, or if the stream was opened with append mode, the
21895 character is appended to the output stream.
21896 <p><b>Returns</b>
21897 <p><!--para 3 -->
21898 The fputwc function returns the wide character written. If a write error occurs, the
21899 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
21900 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
21904 <p><b>Synopsis</b>
21905 <p><!--para 1 -->
21906 <pre>
21909 int fputws(const wchar_t * restrict s,
21910 FILE * restrict stream);
21911 </pre>
21912 <p><b>Description</b>
21913 <p><!--para 2 -->
21914 The fputws function writes the wide string pointed to by s to the stream pointed to by
21915 stream. The terminating null wide character is not written.
21916 <p><b>Returns</b>
21917 <p><!--para 3 -->
21918 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
21919 returns a nonnegative value.
21920 <!--page 438 -->
21924 <p><b>Synopsis</b>
21925 <p><!--para 1 -->
21926 <pre>
21929 int fwide(FILE *stream, int mode);
21930 </pre>
21931 <p><b>Description</b>
21932 <p><!--para 2 -->
21933 The fwide function determines the orientation of the stream pointed to by stream. If
21934 mode is greater than zero, the function first attempts to make the stream wide oriented. If
21935 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note329"><b>329)</b></a></sup>
21936 Otherwise, mode is zero and the function does not alter the orientation of the stream.
21937 <p><b>Returns</b>
21938 <p><!--para 3 -->
21939 The fwide function returns a value greater than zero if, after the call, the stream has
21940 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
21941 stream has no orientation.
21943 <p><b>Footnotes</b>
21944 <p><small><a name="note329" href="#note329">329)</a> If the orientation of the stream has already been determined, fwide does not change it.
21945 </small>
21949 <p><b>Synopsis</b>
21950 <p><!--para 1 -->
21951 <pre>
21954 wint_t getwc(FILE *stream);
21955 </pre>
21956 <p><b>Description</b>
21957 <p><!--para 2 -->
21958 The getwc function is equivalent to fgetwc, except that if it is implemented as a
21959 macro, it may evaluate stream more than once, so the argument should never be an
21960 expression with side effects.
21961 <p><b>Returns</b>
21962 <p><!--para 3 -->
21963 The getwc function returns the next wide character from the input stream pointed to by
21964 stream, or WEOF.
21968 <p><b>Synopsis</b>
21969 <p><!--para 1 -->
21970 <pre>
21972 wint_t getwchar(void);
21973 </pre>
21978 <!--page 439 -->
21979 <p><b>Description</b>
21980 <p><!--para 2 -->
21981 The getwchar function is equivalent to getwc with the argument stdin.
21982 <p><b>Returns</b>
21983 <p><!--para 3 -->
21984 The getwchar function returns the next wide character from the input stream pointed to
21985 by stdin, or WEOF.
21989 <p><b>Synopsis</b>
21990 <p><!--para 1 -->
21991 <pre>
21994 wint_t putwc(wchar_t c, FILE *stream);
21995 </pre>
21996 <p><b>Description</b>
21997 <p><!--para 2 -->
21998 The putwc function is equivalent to fputwc, except that if it is implemented as a
21999 macro, it may evaluate stream more than once, so that argument should never be an
22000 expression with side effects.
22001 <p><b>Returns</b>
22002 <p><!--para 3 -->
22003 The putwc function returns the wide character written, or WEOF.
22007 <p><b>Synopsis</b>
22008 <p><!--para 1 -->
22009 <pre>
22011 wint_t putwchar(wchar_t c);
22012 </pre>
22013 <p><b>Description</b>
22014 <p><!--para 2 -->
22015 The putwchar function is equivalent to putwc with the second argument stdout.
22016 <p><b>Returns</b>
22017 <p><!--para 3 -->
22018 The putwchar function returns the character written, or WEOF.
22022 <p><b>Synopsis</b>
22023 <p><!--para 1 -->
22024 <pre>
22027 wint_t ungetwc(wint_t c, FILE *stream);
22028 </pre>
22029 <p><b>Description</b>
22030 <p><!--para 2 -->
22031 The ungetwc function pushes the wide character specified by c back onto the input
22032 stream pointed to by stream. Pushed-back wide characters will be returned by
22033 subsequent reads on that stream in the reverse order of their pushing. A successful
22034 <!--page 440 -->
22035 intervening call (with the stream pointed to by stream) to a file positioning function
22036 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
22037 stream. The external storage corresponding to the stream is unchanged.
22038 <p><!--para 3 -->
22039 One wide character of pushback is guaranteed, even if the call to the ungetwc function
22040 follows just after a call to a formatted wide character input function fwscanf,
22041 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
22042 on the same stream without an intervening read or file positioning operation on that
22043 stream, the operation may fail.
22044 <p><!--para 4 -->
22045 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
22046 unchanged.
22047 <p><!--para 5 -->
22048 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
22049 The value of the file position indicator for the stream after reading or discarding all
22050 pushed-back wide characters is the same as it was before the wide characters were pushed
22051 back. For a text or binary stream, the value of its file position indicator after a successful
22052 call to the ungetwc function is unspecified until all pushed-back wide characters are
22053 read or discarded.
22054 <p><b>Returns</b>
22055 <p><!--para 6 -->
22056 The ungetwc function returns the wide character pushed back, or WEOF if the operation
22057 fails.
22061 <p><!--para 1 -->
22062 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide string
22063 manipulation. Various methods are used for determining the lengths of the arrays, but in
22064 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
22065 array. If an array is accessed beyond the end of an object, the behavior is undefined.
22066 <p><!--para 2 -->
22067 Where an argument declared as size_t n determines the length of the array for a
22068 function, n can have the value zero on a call to that function. Unless explicitly stated
22069 otherwise in the description of a particular function in this subclause, pointer arguments
22070 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
22071 function that locates a wide character finds no occurrence, a function that compares two
22072 wide character sequences returns zero, and a function that copies wide characters copies
22073 zero wide characters.
22074 <!--page 441 -->
22077 <h5><a name="7.28.4.1" href="#7.28.4.1">7.28.4.1 Wide string numeric conversion functions</a></h5>
22080 <h5><a name="7.28.4.1.1" href="#7.28.4.1.1">7.28.4.1.1 The wcstod, wcstof, and wcstold functions</a></h5>
22081 <p><b>Synopsis</b>
22082 <p><!--para 1 -->
22083 <pre>
22085 double wcstod(const wchar_t * restrict nptr,
22086 wchar_t ** restrict endptr);
22087 float wcstof(const wchar_t * restrict nptr,
22088 wchar_t ** restrict endptr);
22089 long double wcstold(const wchar_t * restrict nptr,
22090 wchar_t ** restrict endptr);
22091 </pre>
22092 <p><b>Description</b>
22093 <p><!--para 2 -->
22094 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
22095 string pointed to by nptr to double, float, and long double representation,
22096 respectively. First, they decompose the input string into three parts: an initial, possibly
22097 empty, sequence of white-space wide characters (as specified by the iswspace
22098 function), a subject sequence resembling a floating-point constant or representing an
22099 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
22100 including the terminating null wide character of the input wide string. Then, they attempt
22101 to convert the subject sequence to a floating-point number, and return the result.
22102 <p><!--para 3 -->
22103 The expected form of the subject sequence is an optional plus or minus sign, then one of
22104 the following:
22105 <ul>
22106 <li> a nonempty sequence of decimal digits optionally containing a decimal-point wide
22107 character, then an optional exponent part as defined for the corresponding single-byte
22109 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
22110 decimal-point wide character, then an optional binary exponent part as defined in
22112 <li> INF or INFINITY, or any other wide string equivalent except for case
22113 <li> NAN or NAN(n-wchar-sequence<sub>opt</sub>), or any other wide string equivalent except for
22114 case in the NAN part, where:
22115 <pre>
22116 n-wchar-sequence:
22117 digit
22118 nondigit
22119 n-wchar-sequence digit
22120 n-wchar-sequence nondigit
22121 </pre>
22122 </ul>
22123 The subject sequence is defined as the longest initial subsequence of the input wide
22124 string, starting with the first non-white-space wide character, that is of the expected form.
22125 <!--page 442 -->
22126 The subject sequence contains no wide characters if the input wide string is not of the
22127 expected form.
22128 <p><!--para 4 -->
22129 If the subject sequence has the expected form for a floating-point number, the sequence of
22130 wide characters starting with the first digit or the decimal-point wide character
22131 (whichever occurs first) is interpreted as a floating constant according to the rules of
22132 <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
22133 if neither an exponent part nor a decimal-point wide character appears in a decimal
22134 floating point number, or if a binary exponent part does not appear in a hexadecimal
22135 floating point number, an exponent part of the appropriate type with value zero is
22136 assumed to follow the last digit in the string. If the subject sequence begins with a minus
22137 sign, the sequence is interpreted as negated.<sup><a href="#note330"><b>330)</b></a></sup> A wide character sequence INF or
22138 INFINITY is interpreted as an infinity, if representable in the return type, else like a
22139 floating constant that is too large for the range of the return type. A wide character
22140 sequence NAN or NAN(n-wchar-sequence<sub>opt</sub>) is interpreted as a quiet NaN, if supported
22141 in the return type, else like a subject sequence part that does not have the expected form;
22142 the meaning of the n-wchar sequences is implementation-defined.<sup><a href="#note331"><b>331)</b></a></sup> A pointer to the
22143 final wide string is stored in the object pointed to by endptr, provided that endptr is
22144 not a null pointer.
22145 <p><!--para 5 -->
22146 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
22147 value resulting from the conversion is correctly rounded.
22148 <p><!--para 6 -->
22150 accepted.
22151 <p><!--para 7 -->
22152 If the subject sequence is empty or does not have the expected form, no conversion is
22153 performed; the value of nptr is stored in the object pointed to by endptr, provided
22154 that endptr is not a null pointer.
22155 <p><b>Recommended practice</b>
22156 <p><!--para 8 -->
22157 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
22158 the result is not exactly representable, the result should be one of the two numbers in the
22159 appropriate internal format that are adjacent to the hexadecimal floating source value,
22160 with the extra stipulation that the error should have a correct sign for the current rounding
22161 direction.
22165 <!--page 443 -->
22166 <p><!--para 9 -->
22167 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
22168 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
22169 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
22170 consider the two bounding, adjacent decimal strings L and U, both having
22171 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
22172 The result should be one of the (equal or adjacent) values that would be obtained by
22173 correctly rounding L and U according to the current rounding direction, with the extra
22174 stipulation that the error with respect to D should have a correct sign for the current
22176 <p><b>Returns</b>
22177 <p><!--para 10 -->
22178 The functions return the converted value, if any. If no conversion could be performed,
22179 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
22180 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
22181 return type and sign of the value), and the value of the macro ERANGE is stored in
22182 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
22183 no greater than the smallest normalized positive number in the return type; whether
22184 errno acquires the value ERANGE is implementation-defined.
22189 <!--page 444 -->
22191 <p><b>Footnotes</b>
22192 <p><small><a name="note330" href="#note330">330)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
22193 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
22194 methods may yield different results if rounding is toward positive or negative infinity. In either case,
22195 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
22196 </small>
22197 <p><small><a name="note331" href="#note331">331)</a> An implementation may use the n-wchar sequence to determine extra information to be represented in
22198 the NaN's significand.
22199 </small>
22200 <p><small><a name="note332" href="#note332">332)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
22201 to the same internal floating value, but if not will round to adjacent values.
22202 </small>
22205 <h5><a name="7.28.4.1.2" href="#7.28.4.1.2">7.28.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions</a></h5>
22206 <p><b>Synopsis</b>
22207 <p><!--para 1 -->
22208 <pre>
22210 long int wcstol(
22211 const wchar_t * restrict nptr,
22212 wchar_t ** restrict endptr,
22213 int base);
22214 long long int wcstoll(
22215 const wchar_t * restrict nptr,
22216 wchar_t ** restrict endptr,
22217 int base);
22218 unsigned long int wcstoul(
22219 const wchar_t * restrict nptr,
22220 wchar_t ** restrict endptr,
22221 int base);
22222 unsigned long long int wcstoull(
22223 const wchar_t * restrict nptr,
22224 wchar_t ** restrict endptr,
22225 int base);
22226 </pre>
22227 <p><b>Description</b>
22228 <p><!--para 2 -->
22229 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
22230 portion of the wide string pointed to by nptr to long int, long long int,
22231 unsigned long int, and unsigned long long int representation,
22232 respectively. First, they decompose the input string into three parts: an initial, possibly
22233 empty, sequence of white-space wide characters (as specified by the iswspace
22234 function), a subject sequence resembling an integer represented in some radix determined
22235 by the value of base, and a final wide string of one or more unrecognized wide
22236 characters, including the terminating null wide character of the input wide string. Then,
22237 they attempt to convert the subject sequence to an integer, and return the result.
22238 <p><!--para 3 -->
22239 If the value of base is zero, the expected form of the subject sequence is that of an
22240 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
22241 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
22242 value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
22243 is a sequence of letters and digits representing an integer with the radix specified by
22244 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
22245 The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
22246 letters and digits whose ascribed values are less than that of base are permitted. If the
22247 value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
22248 of letters and digits, following the sign if present.
22249 <!--page 445 -->
22250 <p><!--para 4 -->
22251 The subject sequence is defined as the longest initial subsequence of the input wide
22252 string, starting with the first non-white-space wide character, that is of the expected form.
22253 The subject sequence contains no wide characters if the input wide string is empty or
22254 consists entirely of white space, or if the first non-white-space wide character is other
22255 than a sign or a permissible letter or digit.
22256 <p><!--para 5 -->
22257 If the subject sequence has the expected form and the value of base is zero, the sequence
22258 of wide characters starting with the first digit is interpreted as an integer constant
22259 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
22260 value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
22261 letter its value as given above. If the subject sequence begins with a minus sign, the value
22262 resulting from the conversion is negated (in the return type). A pointer to the final wide
22263 string is stored in the object pointed to by endptr, provided that endptr is not a null
22264 pointer.
22265 <p><!--para 6 -->
22267 accepted.
22268 <p><!--para 7 -->
22269 If the subject sequence is empty or does not have the expected form, no conversion is
22270 performed; the value of nptr is stored in the object pointed to by endptr, provided
22271 that endptr is not a null pointer.
22272 <p><b>Returns</b>
22273 <p><!--para 8 -->
22274 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
22275 value, if any. If no conversion could be performed, zero is returned. If the correct value
22276 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
22277 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
22278 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
22285 <p><b>Synopsis</b>
22286 <p><!--para 1 -->
22287 <pre>
22289 wchar_t *wcscpy(wchar_t * restrict s1,
22290 const wchar_t * restrict s2);
22291 </pre>
22292 <p><b>Description</b>
22293 <p><!--para 2 -->
22294 The wcscpy function copies the wide string pointed to by s2 (including the terminating
22295 null wide character) into the array pointed to by s1.
22296 <p><b>Returns</b>
22297 <p><!--para 3 -->
22298 The wcscpy function returns the value of s1.
22299 <!--page 446 -->
22303 <p><b>Synopsis</b>
22304 <p><!--para 1 -->
22305 <pre>
22307 wchar_t *wcsncpy(wchar_t * restrict s1,
22308 const wchar_t * restrict s2,
22309 size_t n);
22310 </pre>
22311 <p><b>Description</b>
22312 <p><!--para 2 -->
22313 The wcsncpy function copies not more than n wide characters (those that follow a null
22314 wide character are not copied) from the array pointed to by s2 to the array pointed to by
22316 <p><!--para 3 -->
22317 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
22318 wide characters are appended to the copy in the array pointed to by s1, until n wide
22319 characters in all have been written.
22320 <p><b>Returns</b>
22321 <p><!--para 4 -->
22322 The wcsncpy function returns the value of s1.
22324 <p><b>Footnotes</b>
22325 <p><small><a name="note333" href="#note333">333)</a> Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
22326 result will not be null-terminated.
22327 </small>
22331 <p><b>Synopsis</b>
22332 <p><!--para 1 -->
22333 <pre>
22335 wchar_t *wmemcpy(wchar_t * restrict s1,
22336 const wchar_t * restrict s2,
22337 size_t n);
22338 </pre>
22339 <p><b>Description</b>
22340 <p><!--para 2 -->
22341 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
22342 object pointed to by s1.
22343 <p><b>Returns</b>
22344 <p><!--para 3 -->
22345 The wmemcpy function returns the value of s1.
22350 <!--page 447 -->
22354 <p><b>Synopsis</b>
22355 <p><!--para 1 -->
22356 <pre>
22358 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
22359 size_t n);
22360 </pre>
22361 <p><b>Description</b>
22362 <p><!--para 2 -->
22363 The wmemmove function copies n wide characters from the object pointed to by s2 to
22364 the object pointed to by s1. Copying takes place as if the n wide characters from the
22365 object pointed to by s2 are first copied into a temporary array of n wide characters that
22366 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
22367 the temporary array are copied into the object pointed to by s1.
22368 <p><b>Returns</b>
22369 <p><!--para 3 -->
22370 The wmemmove function returns the value of s1.
22377 <p><b>Synopsis</b>
22378 <p><!--para 1 -->
22379 <pre>
22381 wchar_t *wcscat(wchar_t * restrict s1,
22382 const wchar_t * restrict s2);
22383 </pre>
22384 <p><b>Description</b>
22385 <p><!--para 2 -->
22386 The wcscat function appends a copy of the wide string pointed to by s2 (including the
22387 terminating null wide character) to the end of the wide string pointed to by s1. The initial
22388 wide character of s2 overwrites the null wide character at the end of s1.
22389 <p><b>Returns</b>
22390 <p><!--para 3 -->
22391 The wcscat function returns the value of s1.
22395 <p><b>Synopsis</b>
22396 <p><!--para 1 -->
22397 <pre>
22399 wchar_t *wcsncat(wchar_t * restrict s1,
22400 const wchar_t * restrict s2,
22401 size_t n);
22402 </pre>
22403 <p><b>Description</b>
22404 <p><!--para 2 -->
22405 The wcsncat function appends not more than n wide characters (a null wide character
22406 and those that follow it are not appended) from the array pointed to by s2 to the end of
22407 <!--page 448 -->
22408 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
22409 wide character at the end of s1. A terminating null wide character is always appended to
22411 <p><b>Returns</b>
22412 <p><!--para 3 -->
22413 The wcsncat function returns the value of s1.
22415 <p><b>Footnotes</b>
22416 <p><small><a name="note334" href="#note334">334)</a> Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
22417 wcslen(s1)+n+1.
22418 </small>
22422 <p><!--para 1 -->
22423 Unless explicitly stated otherwise, the functions described in this subclause order two
22424 wide characters the same way as two integers of the underlying integer type designated
22425 by wchar_t.
22429 <p><b>Synopsis</b>
22430 <p><!--para 1 -->
22431 <pre>
22433 int wcscmp(const wchar_t *s1, const wchar_t *s2);
22434 </pre>
22435 <p><b>Description</b>
22436 <p><!--para 2 -->
22437 The wcscmp function compares the wide string pointed to by s1 to the wide string
22438 pointed to by s2.
22439 <p><b>Returns</b>
22440 <p><!--para 3 -->
22441 The wcscmp function returns an integer greater than, equal to, or less than zero,
22442 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
22443 wide string pointed to by s2.
22447 <p><b>Synopsis</b>
22448 <p><!--para 1 -->
22449 <pre>
22451 int wcscoll(const wchar_t *s1, const wchar_t *s2);
22452 </pre>
22453 <p><b>Description</b>
22454 <p><!--para 2 -->
22455 The wcscoll function compares the wide string pointed to by s1 to the wide string
22456 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
22457 current locale.
22458 <p><b>Returns</b>
22459 <p><!--para 3 -->
22460 The wcscoll function returns an integer greater than, equal to, or less than zero,
22461 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
22464 <!--page 449 -->
22465 wide string pointed to by s2 when both are interpreted as appropriate to the current
22466 locale.
22470 <p><b>Synopsis</b>
22471 <p><!--para 1 -->
22472 <pre>
22474 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
22475 size_t n);
22476 </pre>
22477 <p><b>Description</b>
22478 <p><!--para 2 -->
22479 The wcsncmp function compares not more than n wide characters (those that follow a
22480 null wide character are not compared) from the array pointed to by s1 to the array
22481 pointed to by s2.
22482 <p><b>Returns</b>
22483 <p><!--para 3 -->
22484 The wcsncmp function returns an integer greater than, equal to, or less than zero,
22485 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
22486 to, or less than the possibly null-terminated array pointed to by s2.
22490 <p><b>Synopsis</b>
22491 <p><!--para 1 -->
22492 <pre>
22494 size_t wcsxfrm(wchar_t * restrict s1,
22495 const wchar_t * restrict s2,
22496 size_t n);
22497 </pre>
22498 <p><b>Description</b>
22499 <p><!--para 2 -->
22500 The wcsxfrm function transforms the wide string pointed to by s2 and places the
22501 resulting wide string into the array pointed to by s1. The transformation is such that if
22502 the wcscmp function is applied to two transformed wide strings, it returns a value greater
22503 than, equal to, or less than zero, corresponding to the result of the wcscoll function
22504 applied to the same two original wide strings. No more than n wide characters are placed
22505 into the resulting array pointed to by s1, including the terminating null wide character. If
22506 n is zero, s1 is permitted to be a null pointer.
22507 <p><b>Returns</b>
22508 <p><!--para 3 -->
22509 The wcsxfrm function returns the length of the transformed wide string (not including
22510 the terminating null wide character). If the value returned is n or greater, the contents of
22511 the array pointed to by s1 are indeterminate.
22512 <p><!--para 4 -->
22513 EXAMPLE The value of the following expression is the length of the array needed to hold the
22514 transformation of the wide string pointed to by s:
22515 <!--page 450 -->
22516 <pre>
22517 1 + wcsxfrm(NULL, s, 0)
22518 </pre>
22523 <p><b>Synopsis</b>
22524 <p><!--para 1 -->
22525 <pre>
22527 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
22528 size_t n);
22529 </pre>
22530 <p><b>Description</b>
22531 <p><!--para 2 -->
22532 The wmemcmp function compares the first n wide characters of the object pointed to by
22533 s1 to the first n wide characters of the object pointed to by s2.
22534 <p><b>Returns</b>
22535 <p><!--para 3 -->
22536 The wmemcmp function returns an integer greater than, equal to, or less than zero,
22537 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
22538 pointed to by s2.
22545 <p><b>Synopsis</b>
22546 <p><!--para 1 -->
22547 <pre>
22549 wchar_t *wcschr(const wchar_t *s, wchar_t c);
22550 </pre>
22551 <p><b>Description</b>
22552 <p><!--para 2 -->
22553 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
22554 The terminating null wide character is considered to be part of the wide string.
22555 <p><b>Returns</b>
22556 <p><!--para 3 -->
22557 The wcschr function returns a pointer to the located wide character, or a null pointer if
22558 the wide character does not occur in the wide string.
22562 <p><b>Synopsis</b>
22563 <p><!--para 1 -->
22564 <pre>
22566 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
22567 </pre>
22568 <p><b>Description</b>
22569 <p><!--para 2 -->
22570 The wcscspn function computes the length of the maximum initial segment of the wide
22571 string pointed to by s1 which consists entirely of wide characters not from the wide
22572 string pointed to by s2.
22573 <!--page 451 -->
22574 <p><b>Returns</b>
22575 <p><!--para 3 -->
22576 The wcscspn function returns the length of the segment.
22580 <p><b>Synopsis</b>
22581 <p><!--para 1 -->
22582 <pre>
22584 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
22585 </pre>
22586 <p><b>Description</b>
22587 <p><!--para 2 -->
22588 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
22589 any wide character from the wide string pointed to by s2.
22590 <p><b>Returns</b>
22591 <p><!--para 3 -->
22592 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
22593 no wide character from s2 occurs in s1.
22597 <p><b>Synopsis</b>
22598 <p><!--para 1 -->
22599 <pre>
22601 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
22602 </pre>
22603 <p><b>Description</b>
22604 <p><!--para 2 -->
22605 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
22606 s. The terminating null wide character is considered to be part of the wide string.
22607 <p><b>Returns</b>
22608 <p><!--para 3 -->
22609 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
22610 not occur in the wide string.
22614 <p><b>Synopsis</b>
22615 <p><!--para 1 -->
22616 <pre>
22618 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
22619 </pre>
22620 <p><b>Description</b>
22621 <p><!--para 2 -->
22622 The wcsspn function computes the length of the maximum initial segment of the wide
22623 string pointed to by s1 which consists entirely of wide characters from the wide string
22624 pointed to by s2.
22625 <p><b>Returns</b>
22626 <p><!--para 3 -->
22627 The wcsspn function returns the length of the segment.
22628 <!--page 452 -->
22632 <p><b>Synopsis</b>
22633 <p><!--para 1 -->
22634 <pre>
22636 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
22637 </pre>
22638 <p><b>Description</b>
22639 <p><!--para 2 -->
22640 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
22641 the sequence of wide characters (excluding the terminating null wide character) in the
22642 wide string pointed to by s2.
22643 <p><b>Returns</b>
22644 <p><!--para 3 -->
22645 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
22646 wide string is not found. If s2 points to a wide string with zero length, the function
22647 returns s1.
22651 <p><b>Synopsis</b>
22652 <p><!--para 1 -->
22653 <pre>
22655 wchar_t *wcstok(wchar_t * restrict s1,
22656 const wchar_t * restrict s2,
22657 wchar_t ** restrict ptr);
22658 </pre>
22659 <p><b>Description</b>
22660 <p><!--para 2 -->
22661 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
22662 a sequence of tokens, each of which is delimited by a wide character from the wide string
22663 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
22664 which the wcstok function stores information necessary for it to continue scanning the
22665 same wide string.
22666 <p><!--para 3 -->
22667 The first call in a sequence has a non-null first argument and stores an initial value in the
22668 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
22669 the object pointed to by ptr is required to have the value stored by the previous call in
22670 the sequence, which is then updated. The separator wide string pointed to by s2 may be
22671 different from call to call.
22672 <p><!--para 4 -->
22673 The first call in the sequence searches the wide string pointed to by s1 for the first wide
22674 character that is not contained in the current separator wide string pointed to by s2. If no
22675 such wide character is found, then there are no tokens in the wide string pointed to by s1
22676 and the wcstok function returns a null pointer. If such a wide character is found, it is
22677 the start of the first token.
22678 <p><!--para 5 -->
22679 The wcstok function then searches from there for a wide character that is contained in
22680 the current separator wide string. If no such wide character is found, the current token
22681 <!--page 453 -->
22682 extends to the end of the wide string pointed to by s1, and subsequent searches in the
22683 same wide string for a token return a null pointer. If such a wide character is found, it is
22684 overwritten by a null wide character, which terminates the current token.
22685 <p><!--para 6 -->
22686 In all cases, the wcstok function stores sufficient information in the pointer pointed to
22687 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
22688 value for ptr, shall start searching just past the element overwritten by a null wide
22689 character (if any).
22690 <p><b>Returns</b>
22691 <p><!--para 7 -->
22692 The wcstok function returns a pointer to the first wide character of a token, or a null
22693 pointer if there is no token.
22694 <p><!--para 8 -->
22695 EXAMPLE
22696 <pre>
22700 wchar_t *t, *ptr1, *ptr2;
22706 </pre>
22711 <p><b>Synopsis</b>
22712 <p><!--para 1 -->
22713 <pre>
22715 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
22716 size_t n);
22717 </pre>
22718 <p><b>Description</b>
22719 <p><!--para 2 -->
22720 The wmemchr function locates the first occurrence of c in the initial n wide characters of
22721 the object pointed to by s.
22722 <p><b>Returns</b>
22723 <p><!--para 3 -->
22724 The wmemchr function returns a pointer to the located wide character, or a null pointer if
22725 the wide character does not occur in the object.
22726 <!--page 454 -->
22733 <p><b>Synopsis</b>
22734 <p><!--para 1 -->
22735 <pre>
22737 size_t wcslen(const wchar_t *s);
22738 </pre>
22739 <p><b>Description</b>
22740 <p><!--para 2 -->
22741 The wcslen function computes the length of the wide string pointed to by s.
22742 <p><b>Returns</b>
22743 <p><!--para 3 -->
22744 The wcslen function returns the number of wide characters that precede the terminating
22745 null wide character.
22749 <p><b>Synopsis</b>
22750 <p><!--para 1 -->
22751 <pre>
22753 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
22754 </pre>
22755 <p><b>Description</b>
22756 <p><!--para 2 -->
22757 The wmemset function copies the value of c into each of the first n wide characters of
22758 the object pointed to by s.
22759 <p><b>Returns</b>
22760 <p><!--para 3 -->
22761 The wmemset function returns the value of s.
22768 <p><b>Synopsis</b>
22769 <p><!--para 1 -->
22770 <pre>
22773 size_t wcsftime(wchar_t * restrict s,
22774 size_t maxsize,
22775 const wchar_t * restrict format,
22776 const struct tm * restrict timeptr);
22777 </pre>
22778 <p><b>Description</b>
22779 <p><!--para 2 -->
22780 The wcsftime function is equivalent to the strftime function, except that:
22781 <ul>
22782 <li> The argument s points to the initial element of an array of wide characters into which
22783 the generated output is to be placed.
22784 <!--page 455 -->
22785 <li> The argument maxsize indicates the limiting number of wide characters.
22786 <li> The argument format is a wide string and the conversion specifiers are replaced by
22787 corresponding sequences of wide characters.
22788 <li> The return value indicates the number of wide characters.
22789 </ul>
22790 <p><b>Returns</b>
22791 <p><!--para 3 -->
22792 If the total number of resulting wide characters including the terminating null wide
22793 character is not more than maxsize, the wcsftime function returns the number of
22794 wide characters placed into the array pointed to by s not including the terminating null
22795 wide character. Otherwise, zero is returned and the contents of the array are
22796 indeterminate.
22799 <h4><a name="7.28.6" href="#7.28.6">7.28.6 Extended multibyte/wide character conversion utilities</a></h4>
22800 <p><!--para 1 -->
22801 The header <a href="#7.28"><wchar.h></a> declares an extended set of functions useful for conversion
22802 between multibyte characters and wide characters.
22803 <p><!--para 2 -->
22804 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.28.6.3">7.28.6.3</a> and
22805 <a href="#7.28.6.4">7.28.6.4</a> -- take as a last argument a pointer to an object of type mbstate_t that is used
22806 to describe the current conversion state from a particular multibyte character sequence to
22807 a wide character sequence (or the reverse) under the rules of a particular setting for the
22808 LC_CTYPE category of the current locale.
22809 <p><!--para 3 -->
22810 The initial conversion state corresponds, for a conversion in either direction, to the
22811 beginning of a new multibyte character in the initial shift state. A zero-valued
22812 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
22813 valued mbstate_t object can be used to initiate conversion involving any multibyte
22814 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
22815 been altered by any of the functions described in this subclause, and is then used with a
22816 different multibyte character sequence, or in the other conversion direction, or with a
22817 different LC_CTYPE category setting than on earlier function calls, the behavior is
22819 <p><!--para 4 -->
22820 On entry, each function takes the described conversion state (either internal or pointed to
22821 by an argument) as current. The conversion state described by the referenced object is
22822 altered as needed to track the shift state, and the position within a multibyte character, for
22823 the associated multibyte character sequence.
22828 <!--page 456 -->
22830 <p><b>Footnotes</b>
22831 <p><small><a name="note335" href="#note335">335)</a> Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
22832 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
22833 character string.
22834 </small>
22837 <h5><a name="7.28.6.1" href="#7.28.6.1">7.28.6.1 Single-byte/wide character conversion functions</a></h5>
22841 <p><b>Synopsis</b>
22842 <p><!--para 1 -->
22843 <pre>
22845 wint_t btowc(int c);
22846 </pre>
22847 <p><b>Description</b>
22848 <p><!--para 2 -->
22849 The btowc function determines whether c constitutes a valid single-byte character in the
22850 initial shift state.
22851 <p><b>Returns</b>
22852 <p><!--para 3 -->
22853 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
22854 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
22855 returns the wide character representation of that character.
22859 <p><b>Synopsis</b>
22860 <p><!--para 1 -->
22861 <pre>
22863 int wctob(wint_t c);
22864 </pre>
22865 <p><b>Description</b>
22866 <p><!--para 2 -->
22867 The wctob function determines whether c corresponds to a member of the extended
22868 character set whose multibyte character representation is a single byte when in the initial
22869 shift state.
22870 <p><b>Returns</b>
22871 <p><!--para 3 -->
22872 The wctob function returns EOF if c does not correspond to a multibyte character with
22873 length one in the initial shift state. Otherwise, it returns the single-byte representation of
22874 that character as an unsigned char converted to an int.
22881 <p><b>Synopsis</b>
22882 <p><!--para 1 -->
22883 <pre>
22885 int mbsinit(const mbstate_t *ps);
22886 </pre>
22887 <p><b>Description</b>
22888 <p><!--para 2 -->
22889 If ps is not a null pointer, the mbsinit function determines whether the referenced
22890 mbstate_t object describes an initial conversion state.
22891 <!--page 457 -->
22892 <p><b>Returns</b>
22893 <p><!--para 3 -->
22894 The mbsinit function returns nonzero if ps is a null pointer or if the referenced object
22895 describes an initial conversion state; otherwise, it returns zero.
22898 <h5><a name="7.28.6.3" href="#7.28.6.3">7.28.6.3 Restartable multibyte/wide character conversion functions</a></h5>
22899 <p><!--para 1 -->
22900 These functions differ from the corresponding multibyte character functions of <a href="#7.22.7">7.22.7</a>
22901 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
22902 pointer to mbstate_t that points to an object that can completely describe the current
22903 conversion state of the associated multibyte character sequence. If ps is a null pointer,
22904 each function uses its own internal mbstate_t object instead, which is initialized at
22905 program startup to the initial conversion state; the functions are not required to avoid data
22906 races in this case. The implementation behaves as if no library function calls these
22907 functions with a null pointer for ps.
22908 <p><!--para 2 -->
22909 Also unlike their corresponding functions, the return value does not represent whether the
22910 encoding is state-dependent.
22914 <p><b>Synopsis</b>
22915 <p><!--para 1 -->
22916 <pre>
22918 size_t mbrlen(const char * restrict s,
22919 size_t n,
22920 mbstate_t * restrict ps);
22921 </pre>
22922 <p><b>Description</b>
22923 <p><!--para 2 -->
22924 The mbrlen function is equivalent to the call:
22925 <pre>
22926 mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)
22927 </pre>
22928 where internal is the mbstate_t object for the mbrlen function, except that the
22929 expression designated by ps is evaluated only once.
22930 <p><b>Returns</b>
22931 <p><!--para 3 -->
22932 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
22933 or (size_t)(-1).
22935 <!--page 458 -->
22939 <p><b>Synopsis</b>
22940 <p><!--para 1 -->
22941 <pre>
22943 size_t mbrtowc(wchar_t * restrict pwc,
22944 const char * restrict s,
22945 size_t n,
22946 mbstate_t * restrict ps);
22947 </pre>
22948 <p><b>Description</b>
22949 <p><!--para 2 -->
22950 If s is a null pointer, the mbrtowc function is equivalent to the call:
22951 <pre>
22953 </pre>
22954 In this case, the values of the parameters pwc and n are ignored.
22955 <p><!--para 3 -->
22956 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
22957 the byte pointed to by s to determine the number of bytes needed to complete the next
22958 multibyte character (including any shift sequences). If the function determines that the
22959 next multibyte character is complete and valid, it determines the value of the
22960 corresponding wide character and then, if pwc is not a null pointer, stores that value in
22961 the object pointed to by pwc. If the corresponding wide character is the null wide
22962 character, the resulting state described is the initial conversion state.
22963 <p><b>Returns</b>
22964 <p><!--para 4 -->
22965 The mbrtowc function returns the first of the following that applies (given the current
22966 conversion state):
22967 0 if the next n or fewer bytes complete the multibyte character that
22968 <pre>
22969 corresponds to the null wide character (which is the value stored).
22970 </pre>
22971 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
22972 <pre>
22973 character (which is the value stored); the value returned is the number
22974 of bytes that complete the multibyte character.
22975 </pre>
22976 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
22977 <pre>
22978 multibyte character, and all n bytes have been processed (no value is
22980 </pre>
22981 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
22982 <pre>
22983 do not contribute to a complete and valid multibyte character (no
22984 value is stored); the value of the macro EILSEQ is stored in errno,
22985 and the conversion state is unspecified.
22986 </pre>
22988 <!--page 459 -->
22990 <p><b>Footnotes</b>
22991 <p><small><a name="note336" href="#note336">336)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
22992 sequence of redundant shift sequences (for implementations with state-dependent encodings).
22993 </small>
22997 <p><b>Synopsis</b>
22998 <p><!--para 1 -->
22999 <pre>
23001 size_t wcrtomb(char * restrict s,
23002 wchar_t wc,
23003 mbstate_t * restrict ps);
23004 </pre>
23005 <p><b>Description</b>
23006 <p><!--para 2 -->
23007 If s is a null pointer, the wcrtomb function is equivalent to the call
23008 <pre>
23009 wcrtomb(buf, L'\0', ps)
23010 </pre>
23011 where buf is an internal buffer.
23012 <p><!--para 3 -->
23013 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
23014 to represent the multibyte character that corresponds to the wide character given by wc
23015 (including any shift sequences), and stores the multibyte character representation in the
23016 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
23017 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
23018 to restore the initial shift state; the resulting state described is the initial conversion state.
23019 <p><b>Returns</b>
23020 <p><!--para 4 -->
23021 The wcrtomb function returns the number of bytes stored in the array object (including
23022 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
23023 the function stores the value of the macro EILSEQ in errno and returns
23024 (size_t)(-1); the conversion state is unspecified.
23027 <h5><a name="7.28.6.4" href="#7.28.6.4">7.28.6.4 Restartable multibyte/wide string conversion functions</a></h5>
23028 <p><!--para 1 -->
23029 These functions differ from the corresponding multibyte string functions of <a href="#7.22.8">7.22.8</a>
23030 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
23031 mbstate_t that points to an object that can completely describe the current conversion
23032 state of the associated multibyte character sequence. If ps is a null pointer, each function
23033 uses its own internal mbstate_t object instead, which is initialized at program startup
23034 to the initial conversion state; the functions are not required to avoid data races in this
23035 case. The implementation behaves as if no library function calls these functions with a
23036 null pointer for ps.
23037 <p><!--para 2 -->
23038 Also unlike their corresponding functions, the conversion source parameter, src, has a
23039 pointer-to-pointer type. When the function is storing the results of conversions (that is,
23040 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
23041 to reflect the amount of the source processed by that invocation.
23042 <!--page 460 -->
23046 <p><b>Synopsis</b>
23047 <p><!--para 1 -->
23048 <pre>
23050 size_t mbsrtowcs(wchar_t * restrict dst,
23051 const char ** restrict src,
23052 size_t len,
23053 mbstate_t * restrict ps);
23054 </pre>
23055 <p><b>Description</b>
23056 <p><!--para 2 -->
23057 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
23058 conversion state described by the object pointed to by ps, from the array indirectly
23059 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
23060 pointer, the converted characters are stored into the array pointed to by dst. Conversion
23061 continues up to and including a terminating null character, which is also stored.
23062 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
23063 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
23064 characters have been stored into the array pointed to by dst.<sup><a href="#note337"><b>337)</b></a></sup> Each conversion takes
23065 place as if by a call to the mbrtowc function.
23066 <p><!--para 3 -->
23067 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
23068 pointer (if conversion stopped due to reaching a terminating null character) or the address
23069 just past the last multibyte character converted (if any). If conversion stopped due to
23070 reaching a terminating null character and if dst is not a null pointer, the resulting state
23071 described is the initial conversion state.
23072 <p><b>Returns</b>
23073 <p><!--para 4 -->
23074 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
23075 character, an encoding error occurs: the mbsrtowcs function stores the value of the
23076 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
23077 unspecified. Otherwise, it returns the number of multibyte characters successfully
23078 converted, not including the terminating null character (if any).
23083 <!--page 461 -->
23085 <p><b>Footnotes</b>
23086 <p><small><a name="note337" href="#note337">337)</a> Thus, the value of len is ignored if dst is a null pointer.
23087 </small>
23091 <p><b>Synopsis</b>
23092 <p><!--para 1 -->
23093 <pre>
23095 size_t wcsrtombs(char * restrict dst,
23096 const wchar_t ** restrict src,
23097 size_t len,
23098 mbstate_t * restrict ps);
23099 </pre>
23100 <p><b>Description</b>
23101 <p><!--para 2 -->
23102 The wcsrtombs function converts a sequence of wide characters from the array
23103 indirectly pointed to by src into a sequence of corresponding multibyte characters that
23104 begins in the conversion state described by the object pointed to by ps. If dst is not a
23105 null pointer, the converted characters are then stored into the array pointed to by dst.
23106 Conversion continues up to and including a terminating null wide character, which is also
23107 stored. Conversion stops earlier in two cases: when a wide character is reached that does
23108 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
23109 next multibyte character would exceed the limit of len total bytes to be stored into the
23110 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
23112 <p><!--para 3 -->
23113 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
23114 pointer (if conversion stopped due to reaching a terminating null wide character) or the
23115 address just past the last wide character converted (if any). If conversion stopped due to
23116 reaching a terminating null wide character, the resulting state described is the initial
23117 conversion state.
23118 <p><b>Returns</b>
23119 <p><!--para 4 -->
23120 If conversion stops because a wide character is reached that does not correspond to a
23121 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
23122 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
23123 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
23124 character sequence, not including the terminating null character (if any).
23129 <!--page 462 -->
23131 <p><b>Footnotes</b>
23132 <p><small><a name="note338" href="#note338">338)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
23133 include those necessary to reach the initial shift state immediately before the null byte.
23134 </small>
23137 <h3><a name="7.29" href="#7.29">7.29 Wide character classification and mapping utilities <wctype.h></a></h3>
23141 <p><!--para 1 -->
23142 The header <a href="#7.29"><wctype.h></a> defines one macro, and declares three data types and many
23144 <p><!--para 2 -->
23145 The types declared are
23146 <pre>
23147 wint_t
23148 </pre>
23150 <pre>
23151 wctrans_t
23152 </pre>
23153 which is a scalar type that can hold values which represent locale-specific character
23154 mappings; and
23155 <pre>
23156 wctype_t
23157 </pre>
23158 which is a scalar type that can hold values which represent locale-specific character
23159 classifications.
23160 <p><!--para 3 -->
23162 <p><!--para 4 -->
23163 The functions declared are grouped as follows:
23164 <ul>
23165 <li> Functions that provide wide character classification;
23166 <li> Extensible functions that provide wide character classification;
23167 <li> Functions that provide wide character case mapping;
23168 <li> Extensible functions that provide wide character mapping.
23169 </ul>
23170 <p><!--para 5 -->
23171 For all functions described in this subclause that accept an argument of type wint_t, the
23172 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
23173 this argument has any other value, the behavior is undefined.
23174 <p><!--para 6 -->
23175 The behavior of these functions is affected by the LC_CTYPE category of the current
23176 locale.
23181 <!--page 463 -->
23183 <p><b>Footnotes</b>
23184 <p><small><a name="note339" href="#note339">339)</a> See ''future library directions'' (<a href="#7.30.13">7.30.13</a>).
23185 </small>
23189 <p><!--para 1 -->
23190 The header <a href="#7.29"><wctype.h></a> declares several functions useful for classifying wide
23191 characters.
23192 <p><!--para 2 -->
23193 The term printing wide character refers to a member of a locale-specific set of wide
23194 characters, each of which occupies at least one printing position on a display device. The
23195 term control wide character refers to a member of a locale-specific set of wide characters
23196 that are not printing wide characters.
23199 <h5><a name="7.29.2.1" href="#7.29.2.1">7.29.2.1 Wide character classification functions</a></h5>
23200 <p><!--para 1 -->
23201 The functions in this subclause return nonzero (true) if and only if the value of the
23202 argument wc conforms to that in the description of the function.
23203 <p><!--para 2 -->
23204 Each of the following functions returns true for each wide character that corresponds (as
23205 if by a call to the wctob function) to a single-byte character for which the corresponding
23206 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
23207 iswpunct functions may differ with respect to wide characters other than L' ' that are
23211 <p><b>Footnotes</b>
23212 <p><small><a name="note340" href="#note340">340)</a> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
23213 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
23214 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
23215 && iswspace(wc) is true, but not both.
23216 </small>
23220 <p><b>Synopsis</b>
23221 <p><!--para 1 -->
23222 <pre>
23224 int iswalnum(wint_t wc);
23225 </pre>
23226 <p><b>Description</b>
23227 <p><!--para 2 -->
23228 The iswalnum function tests for any wide character for which iswalpha or
23229 iswdigit is true.
23233 <p><b>Synopsis</b>
23234 <p><!--para 1 -->
23235 <pre>
23237 int iswalpha(wint_t wc);
23238 </pre>
23239 <p><b>Description</b>
23240 <p><!--para 2 -->
23241 The iswalpha function tests for any wide character for which iswupper or
23242 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
23244 <!--page 464 -->
23245 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
23248 <p><b>Footnotes</b>
23249 <p><small><a name="note341" href="#note341">341)</a> The functions iswlower and iswupper test true or false separately for each of these additional
23250 wide characters; all four combinations are possible.
23251 </small>
23255 <p><b>Synopsis</b>
23256 <p><!--para 1 -->
23257 <pre>
23259 int iswblank(wint_t wc);
23260 </pre>
23261 <p><b>Description</b>
23262 <p><!--para 2 -->
23263 The iswblank function tests for any wide character that is a standard blank wide
23264 character or is one of a locale-specific set of wide characters for which iswspace is true
23265 and that is used to separate words within a line of text. The standard blank wide
23267 locale, iswblank returns true only for the standard blank characters.
23271 <p><b>Synopsis</b>
23272 <p><!--para 1 -->
23273 <pre>
23275 int iswcntrl(wint_t wc);
23276 </pre>
23277 <p><b>Description</b>
23278 <p><!--para 2 -->
23279 The iswcntrl function tests for any control wide character.
23283 <p><b>Synopsis</b>
23284 <p><!--para 1 -->
23285 <pre>
23287 int iswdigit(wint_t wc);
23288 </pre>
23289 <p><b>Description</b>
23290 <p><!--para 2 -->
23291 The iswdigit function tests for any wide character that corresponds to a decimal-digit
23296 <p><b>Synopsis</b>
23297 <p><!--para 1 -->
23298 <pre>
23300 int iswgraph(wint_t wc);
23301 </pre>
23306 <!--page 465 -->
23307 <p><b>Description</b>
23308 <p><!--para 2 -->
23309 The iswgraph function tests for any wide character for which iswprint is true and
23312 <p><b>Footnotes</b>
23313 <p><small><a name="note342" href="#note342">342)</a> Note that the behavior of the iswgraph and iswpunct functions may differ from their
23314 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
23315 characters other than ' '.
23316 </small>
23320 <p><b>Synopsis</b>
23321 <p><!--para 1 -->
23322 <pre>
23324 int iswlower(wint_t wc);
23325 </pre>
23326 <p><b>Description</b>
23327 <p><!--para 2 -->
23328 The iswlower function tests for any wide character that corresponds to a lowercase
23329 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
23330 iswdigit, iswpunct, or iswspace is true.
23334 <p><b>Synopsis</b>
23335 <p><!--para 1 -->
23336 <pre>
23338 int iswprint(wint_t wc);
23339 </pre>
23340 <p><b>Description</b>
23341 <p><!--para 2 -->
23342 The iswprint function tests for any printing wide character.
23346 <p><b>Synopsis</b>
23347 <p><!--para 1 -->
23348 <pre>
23350 int iswpunct(wint_t wc);
23351 </pre>
23352 <p><b>Description</b>
23353 <p><!--para 2 -->
23354 The iswpunct function tests for any printing wide character that is one of a locale-
23355 specific set of punctuation wide characters for which neither iswspace nor iswalnum
23360 <p><b>Synopsis</b>
23361 <p><!--para 1 -->
23362 <pre>
23364 int iswspace(wint_t wc);
23365 </pre>
23369 <!--page 466 -->
23370 <p><b>Description</b>
23371 <p><!--para 2 -->
23372 The iswspace function tests for any wide character that corresponds to a locale-specific
23373 set of white-space wide characters for which none of iswalnum, iswgraph, or
23374 iswpunct is true.
23378 <p><b>Synopsis</b>
23379 <p><!--para 1 -->
23380 <pre>
23382 int iswupper(wint_t wc);
23383 </pre>
23384 <p><b>Description</b>
23385 <p><!--para 2 -->
23386 The iswupper function tests for any wide character that corresponds to an uppercase
23387 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
23388 iswdigit, iswpunct, or iswspace is true.
23392 <p><b>Synopsis</b>
23393 <p><!--para 1 -->
23394 <pre>
23396 int iswxdigit(wint_t wc);
23397 </pre>
23398 <p><b>Description</b>
23399 <p><!--para 2 -->
23400 The iswxdigit function tests for any wide character that corresponds to a
23404 <h5><a name="7.29.2.2" href="#7.29.2.2">7.29.2.2 Extensible wide character classification functions</a></h5>
23405 <p><!--para 1 -->
23406 The functions wctype and iswctype provide extensible wide character classification
23407 as well as testing equivalent to that performed by the functions described in the previous
23412 <p><b>Synopsis</b>
23413 <p><!--para 1 -->
23414 <pre>
23416 int iswctype(wint_t wc, wctype_t desc);
23417 </pre>
23418 <p><b>Description</b>
23419 <p><!--para 2 -->
23420 The iswctype function determines whether the wide character wc has the property
23421 described by desc. The current setting of the LC_CTYPE category shall be the same as
23422 during the call to wctype that returned the value desc.
23423 <p><!--para 3 -->
23424 Each of the following expressions has a truth-value equivalent to the call to the wide
23425 character classification function (<a href="#7.29.2.1">7.29.2.1</a>) in the comment that follows the expression:
23426 <!--page 467 -->
23427 <pre>
23440 </pre>
23441 <p><b>Returns</b>
23442 <p><!--para 4 -->
23443 The iswctype function returns nonzero (true) if and only if the value of the wide
23444 character wc has the property described by desc. If desc is zero, the iswctype
23445 function returns zero (false).
23450 <p><b>Synopsis</b>
23451 <p><!--para 1 -->
23452 <pre>
23454 wctype_t wctype(const char *property);
23455 </pre>
23456 <p><b>Description</b>
23457 <p><!--para 2 -->
23458 The wctype function constructs a value with type wctype_t that describes a class of
23459 wide characters identified by the string argument property.
23460 <p><!--para 3 -->
23461 The strings listed in the description of the iswctype function shall be valid in all
23462 locales as property arguments to the wctype function.
23463 <p><b>Returns</b>
23464 <p><!--para 4 -->
23465 If property identifies a valid class of wide characters according to the LC_CTYPE
23466 category of the current locale, the wctype function returns a nonzero value that is valid
23467 as the second argument to the iswctype function; otherwise, it returns zero.
23468 <!--page 468 -->
23472 <p><!--para 1 -->
23473 The header <a href="#7.29"><wctype.h></a> declares several functions useful for mapping wide characters.
23476 <h5><a name="7.29.3.1" href="#7.29.3.1">7.29.3.1 Wide character case mapping functions</a></h5>
23480 <p><b>Synopsis</b>
23481 <p><!--para 1 -->
23482 <pre>
23484 wint_t towlower(wint_t wc);
23485 </pre>
23486 <p><b>Description</b>
23487 <p><!--para 2 -->
23488 The towlower function converts an uppercase letter to a corresponding lowercase letter.
23489 <p><b>Returns</b>
23490 <p><!--para 3 -->
23491 If the argument is a wide character for which iswupper is true and there are one or
23492 more corresponding wide characters, as specified by the current locale, for which
23493 iswlower is true, the towlower function returns one of the corresponding wide
23494 characters (always the same one for any given locale); otherwise, the argument is
23495 returned unchanged.
23499 <p><b>Synopsis</b>
23500 <p><!--para 1 -->
23501 <pre>
23503 wint_t towupper(wint_t wc);
23504 </pre>
23505 <p><b>Description</b>
23506 <p><!--para 2 -->
23507 The towupper function converts a lowercase letter to a corresponding uppercase letter.
23508 <p><b>Returns</b>
23509 <p><!--para 3 -->
23510 If the argument is a wide character for which iswlower is true and there are one or
23511 more corresponding wide characters, as specified by the current locale, for which
23512 iswupper is true, the towupper function returns one of the corresponding wide
23513 characters (always the same one for any given locale); otherwise, the argument is
23514 returned unchanged.
23517 <h5><a name="7.29.3.2" href="#7.29.3.2">7.29.3.2 Extensible wide character case mapping functions</a></h5>
23518 <p><!--para 1 -->
23519 The functions wctrans and towctrans provide extensible wide character mapping as
23520 well as case mapping equivalent to that performed by the functions described in the
23522 <!--page 469 -->
23526 <p><b>Synopsis</b>
23527 <p><!--para 1 -->
23528 <pre>
23530 wint_t towctrans(wint_t wc, wctrans_t desc);
23531 </pre>
23532 <p><b>Description</b>
23533 <p><!--para 2 -->
23534 The towctrans function maps the wide character wc using the mapping described by
23535 desc. The current setting of the LC_CTYPE category shall be the same as during the call
23536 to wctrans that returned the value desc.
23537 <p><!--para 3 -->
23538 Each of the following expressions behaves the same as the call to the wide character case
23539 mapping function (<a href="#7.29.3.1">7.29.3.1</a>) in the comment that follows the expression:
23540 <pre>
23543 </pre>
23544 <p><b>Returns</b>
23545 <p><!--para 4 -->
23546 The towctrans function returns the mapped value of wc using the mapping described
23547 by desc. If desc is zero, the towctrans function returns the value of wc.
23551 <p><b>Synopsis</b>
23552 <p><!--para 1 -->
23553 <pre>
23555 wctrans_t wctrans(const char *property);
23556 </pre>
23557 <p><b>Description</b>
23558 <p><!--para 2 -->
23559 The wctrans function constructs a value with type wctrans_t that describes a
23560 mapping between wide characters identified by the string argument property.
23561 <p><!--para 3 -->
23562 The strings listed in the description of the towctrans function shall be valid in all
23563 locales as property arguments to the wctrans function.
23564 <p><b>Returns</b>
23565 <p><!--para 4 -->
23566 If property identifies a valid mapping of wide characters according to the LC_CTYPE
23567 category of the current locale, the wctrans function returns a nonzero value that is valid
23568 as the second argument to the towctrans function; otherwise, it returns zero.
23569 <!--page 470 -->
23573 <p><!--para 1 -->
23574 The following names are grouped under individual headers for convenience. All external
23575 names described below are reserved no matter what headers are included by the program.
23579 <p><!--para 1 -->
23580 The function names
23581 <pre>
23582 cerf cexpm1 clog2
23583 cerfc clog10 clgamma
23584 cexp2 clog1p ctgamma
23585 </pre>
23586 and the same names suffixed with f or l may be added to the declarations in the
23591 <p><!--para 1 -->
23592 Function names that begin with either is or to, and a lowercase letter may be added to
23597 <p><!--para 1 -->
23598 Macros that begin with E and a digit or E and an uppercase letter may be added to the
23602 <h4><a name="7.30.4" href="#7.30.4">7.30.4 Format conversion of integer types <inttypes.h></a></h4>
23603 <p><!--para 1 -->
23604 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
23609 <p><!--para 1 -->
23610 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
23615 <p><!--para 1 -->
23616 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
23621 <p><!--para 1 -->
23622 The ability to undefine and perhaps then redefine the macros bool, true, and false is
23623 an obsolescent feature.
23627 <p><!--para 1 -->
23628 Typedef names beginning with int or uint and ending with _t may be added to the
23629 types defined in the <a href="#7.20"><stdint.h></a> header. Macro names beginning with INT or UINT
23630 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
23632 <!--page 471 -->
23636 <p><!--para 1 -->
23637 Lowercase letters may be added to the conversion specifiers and length modifiers in
23638 fprintf and fscanf. Other characters may be used in extensions.
23639 <p><!--para 2 -->
23640 The use of ungetc on a binary stream where the file position indicator is zero prior to *
23641 the call is an obsolescent feature.
23645 <p><!--para 1 -->
23646 Function names that begin with str and a lowercase letter may be added to the
23651 <p><!--para 1 -->
23652 Function names that begin with str, mem, or wcs and a lowercase letter may be added
23656 <h4><a name="7.30.12" href="#7.30.12">7.30.12 Extended multibyte and wide character utilities <wchar.h></a></h4>
23657 <p><!--para 1 -->
23658 Function names that begin with wcs and a lowercase letter may be added to the
23660 <p><!--para 2 -->
23661 Lowercase letters may be added to the conversion specifiers and length modifiers in
23662 fwprintf and fwscanf. Other characters may be used in extensions.
23665 <h4><a name="7.30.13" href="#7.30.13">7.30.13 Wide character classification and mapping utilities</a></h4>
23667 <p><!--para 1 -->
23668 Function names that begin with is or to and a lowercase letter may be added to the
23670 <!--page 472 -->
23674 <pre>
23675 (informative)
23676 Language syntax summary
23677 </pre>
23678 <p><!--para 1 -->
23688 <pre>
23689 keyword
23690 identifier
23691 constant
23692 string-literal
23693 punctuator
23694 </pre>
23696 <!--page 473 -->
23697 <pre>
23698 header-name
23699 identifier
23700 pp-number
23701 character-constant
23702 string-literal
23703 punctuator
23704 each non-white-space character that cannot be one of the above
23705 </pre>
23710 <pre>
23711 alignof goto union
23712 auto if unsigned
23713 break inline void
23714 case int volatile
23715 char long while
23716 const register _Alignas
23717 continue restrict _Atomic
23718 default return _Bool
23719 do short _Complex
23720 double signed _Generic
23721 else sizeof _Imaginary
23722 enum static _Noreturn
23723 extern struct _Static_assert
23724 float switch _Thread_local
23725 for typedef
23726 </pre>
23731 <pre>
23732 identifier-nondigit
23733 identifier identifier-nondigit
23734 identifier digit
23735 </pre>
23737 <pre>
23738 nondigit
23739 universal-character-name
23740 other implementation-defined characters
23741 </pre>
23743 <pre>
23744 _ a b c d e f g h i j k l m
23745 n o p q r s t u v w x y z
23746 A B C D E F G H I J K L M
23747 N O P Q R S T U V W X Y Z
23748 </pre>
23750 <!--page 474 -->
23751 <pre>
23752 0 1 2 3 4 5 6 7 8 9
23753 </pre>
23758 <pre>
23759 \u hex-quad
23760 \U hex-quad hex-quad
23761 </pre>
23763 <pre>
23764 hexadecimal-digit hexadecimal-digit
23765 hexadecimal-digit hexadecimal-digit
23766 </pre>
23771 <pre>
23772 integer-constant
23773 floating-constant
23774 enumeration-constant
23775 character-constant
23776 </pre>
23778 <pre>
23779 decimal-constant integer-suffix<sub>opt</sub>
23780 octal-constant integer-suffix<sub>opt</sub>
23781 hexadecimal-constant integer-suffix<sub>opt</sub>
23782 </pre>
23784 <pre>
23785 nonzero-digit
23786 decimal-constant digit
23787 </pre>
23789 <pre>
23790 0
23791 octal-constant octal-digit
23792 </pre>
23794 <pre>
23795 hexadecimal-prefix hexadecimal-digit
23796 hexadecimal-constant hexadecimal-digit
23797 </pre>
23799 <pre>
23800 0x 0X
23801 </pre>
23803 <pre>
23804 1 2 3 4 5 6 7 8 9
23805 </pre>
23807 <!--page 475 -->
23808 <pre>
23809 0 1 2 3 4 5 6 7
23810 </pre>
23812 <pre>
23813 0 1 2 3 4 5 6 7 8 9
23814 a b c d e f
23815 A B C D E F
23816 </pre>
23818 <pre>
23819 unsigned-suffix long-suffix<sub>opt</sub>
23820 unsigned-suffix long-long-suffix
23821 long-suffix unsigned-suffix<sub>opt</sub>
23822 long-long-suffix unsigned-suffix<sub>opt</sub>
23823 </pre>
23825 <pre>
23826 u U
23827 </pre>
23829 <pre>
23830 l L
23831 </pre>
23833 <pre>
23834 ll LL
23835 </pre>
23837 <pre>
23838 decimal-floating-constant
23839 hexadecimal-floating-constant
23840 </pre>
23842 <pre>
23843 fractional-constant exponent-part<sub>opt</sub> floating-suffix<sub>opt</sub>
23844 digit-sequence exponent-part floating-suffix<sub>opt</sub>
23845 </pre>
23847 <pre>
23848 hexadecimal-prefix hexadecimal-fractional-constant
23849 binary-exponent-part floating-suffix<sub>opt</sub>
23850 hexadecimal-prefix hexadecimal-digit-sequence
23851 binary-exponent-part floating-suffix<sub>opt</sub>
23852 </pre>
23854 <pre>
23855 digit-sequence<sub>opt</sub> . digit-sequence
23856 digit-sequence .
23857 </pre>
23859 <pre>
23860 e sign<sub>opt</sub> digit-sequence
23861 E sign<sub>opt</sub> digit-sequence
23862 </pre>
23864 <!--page 476 -->
23865 <pre>
23866 + -
23867 </pre>
23869 <pre>
23870 digit
23871 digit-sequence digit
23872 </pre>
23874 <pre>
23875 hexadecimal-digit-sequence<sub>opt</sub> .
23876 hexadecimal-digit-sequence
23877 hexadecimal-digit-sequence .
23878 </pre>
23880 <pre>
23881 p sign<sub>opt</sub> digit-sequence
23882 P sign<sub>opt</sub> digit-sequence
23883 </pre>
23885 <pre>
23886 hexadecimal-digit
23887 hexadecimal-digit-sequence hexadecimal-digit
23888 </pre>
23890 <pre>
23891 f l F L
23892 </pre>
23894 <pre>
23895 identifier
23896 </pre>
23898 <pre>
23899 ' c-char-sequence '
23900 L' c-char-sequence '
23901 u' c-char-sequence '
23902 U' c-char-sequence '
23903 </pre>
23905 <pre>
23906 c-char
23907 c-char-sequence c-char
23908 </pre>
23910 <pre>
23911 any member of the source character set except
23912 the single-quote ', backslash \, or new-line character
23913 escape-sequence
23914 </pre>
23916 <!--page 477 -->
23917 <pre>
23918 simple-escape-sequence
23919 octal-escape-sequence
23920 hexadecimal-escape-sequence
23921 universal-character-name
23922 </pre>
23924 <pre>
23925 \' \" \? \\
23926 \a \b \f \n \r \t \v
23927 </pre>
23929 <pre>
23930 \ octal-digit
23931 \ octal-digit octal-digit
23932 \ octal-digit octal-digit octal-digit
23933 </pre>
23935 <pre>
23936 \x hexadecimal-digit
23937 hexadecimal-escape-sequence hexadecimal-digit
23938 </pre>
23943 <pre>
23945 </pre>
23947 <pre>
23948 u8
23949 u
23950 U
23951 L
23952 </pre>
23954 <pre>
23955 s-char
23956 s-char-sequence s-char
23957 </pre>
23959 <pre>
23960 any member of the source character set except
23961 the double-quote ", backslash \, or new-line character
23962 escape-sequence
23963 </pre>
23968 <!--page 478 -->
23969 <pre>
23970 [ ] ( ) { } . ->
23971 ++ -- & * + - ~ !
23972 / % << >> < > <= >= == != ^ | && ||
23973 ? : ; ...
23974 = *= /= %= += -= <<= >>= &= ^= |=
23975 , # ##
23976 <: :> <% %> %: %:%:
23977 </pre>
23982 <pre>
23983 < h-char-sequence >
23985 </pre>
23987 <pre>
23988 h-char
23989 h-char-sequence h-char
23990 </pre>
23992 <pre>
23993 any member of the source character set except
23994 the new-line character and >
23995 </pre>
23997 <pre>
23998 q-char
23999 q-char-sequence q-char
24000 </pre>
24002 <pre>
24003 any member of the source character set except
24004 the new-line character and "
24005 </pre>
24010 <!--page 479 -->
24011 <pre>
24012 digit
24013 . digit
24014 pp-number digit
24015 pp-number identifier-nondigit
24016 pp-number e sign
24017 pp-number E sign
24018 pp-number p sign
24019 pp-number P sign
24020 pp-number .
24021 </pre>
24029 <pre>
24030 identifier
24031 constant
24032 string-literal
24033 ( expression )
24034 generic-selection
24035 </pre>
24037 <pre>
24038 _Generic ( assignment-expression , generic-assoc-list )
24039 </pre>
24041 <pre>
24042 generic-association
24043 generic-assoc-list , generic-association
24044 </pre>
24046 <pre>
24047 type-name : assignment-expression
24048 default : assignment-expression
24049 </pre>
24051 <pre>
24052 primary-expression
24053 postfix-expression [ expression ]
24055 postfix-expression . identifier
24056 postfix-expression -> identifier
24057 postfix-expression ++
24058 postfix-expression --
24059 ( type-name ) { initializer-list }
24060 ( type-name ) { initializer-list , }
24061 </pre>
24063 <pre>
24064 assignment-expression
24065 argument-expression-list , assignment-expression
24066 </pre>
24068 <!--page 480 -->
24069 <pre>
24070 postfix-expression
24071 ++ unary-expression
24072 -- unary-expression
24073 unary-operator cast-expression
24074 sizeof unary-expression
24075 sizeof ( type-name )
24076 alignof ( type-name )
24077 </pre>
24079 <pre>
24080 & * + - ~ !
24081 </pre>
24083 <pre>
24084 unary-expression
24085 ( type-name ) cast-expression
24086 </pre>
24088 <pre>
24089 cast-expression
24090 multiplicative-expression * cast-expression
24091 multiplicative-expression / cast-expression
24092 multiplicative-expression % cast-expression
24093 </pre>
24095 <pre>
24096 multiplicative-expression
24097 additive-expression + multiplicative-expression
24098 additive-expression - multiplicative-expression
24099 </pre>
24101 <pre>
24102 additive-expression
24103 shift-expression << additive-expression
24104 shift-expression >> additive-expression
24105 </pre>
24107 <pre>
24108 shift-expression
24109 relational-expression < shift-expression
24110 relational-expression > shift-expression
24111 relational-expression <= shift-expression
24112 relational-expression >= shift-expression
24113 </pre>
24115 <pre>
24116 relational-expression
24117 equality-expression == relational-expression
24118 equality-expression != relational-expression
24119 </pre>
24121 <pre>
24122 equality-expression
24123 AND-expression & equality-expression
24124 </pre>
24126 <!--page 481 -->
24127 <pre>
24128 AND-expression
24129 exclusive-OR-expression ^ AND-expression
24130 </pre>
24132 <pre>
24133 exclusive-OR-expression
24134 inclusive-OR-expression | exclusive-OR-expression
24135 </pre>
24137 <pre>
24138 inclusive-OR-expression
24139 logical-AND-expression && inclusive-OR-expression
24140 </pre>
24142 <pre>
24143 logical-AND-expression
24144 logical-OR-expression || logical-AND-expression
24145 </pre>
24147 <pre>
24148 logical-OR-expression
24149 logical-OR-expression ? expression : conditional-expression
24150 </pre>
24152 <pre>
24153 conditional-expression
24154 unary-expression assignment-operator assignment-expression
24155 </pre>
24157 <pre>
24159 </pre>
24161 <pre>
24162 assignment-expression
24163 expression , assignment-expression
24164 </pre>
24166 <pre>
24167 conditional-expression
24168 </pre>
24173 <pre>
24175 static_assert-declaration
24176 </pre>
24178 <pre>
24184 </pre>
24186 <!--page 482 -->
24187 <pre>
24188 init-declarator
24189 init-declarator-list , init-declarator
24190 </pre>
24192 <pre>
24193 declarator
24194 declarator = initializer
24195 </pre>
24197 <pre>
24198 typedef
24199 extern
24200 static
24201 _Thread_local
24202 auto
24203 register
24204 </pre>
24206 <pre>
24207 void
24208 char
24209 short
24210 int
24211 long
24212 float
24213 double
24214 signed
24215 unsigned
24216 _Bool
24217 _Complex
24218 atomic-type-specifier
24219 struct-or-union-specifier
24220 enum-specifier
24221 typedef-name
24222 </pre>
24224 <pre>
24226 struct-or-union identifier
24227 </pre>
24229 <pre>
24230 struct
24231 union
24232 </pre>
24234 <pre>
24235 struct-declaration
24236 struct-declaration-list struct-declaration
24237 </pre>
24239 <!--page 483 -->
24240 <pre>
24242 static_assert-declaration
24243 </pre>
24245 <pre>
24248 </pre>
24250 <pre>
24251 struct-declarator
24252 struct-declarator-list , struct-declarator
24253 </pre>
24255 <pre>
24256 declarator
24258 </pre>
24260 <pre>
24263 enum identifier
24264 </pre>
24266 <pre>
24267 enumerator
24268 enumerator-list , enumerator
24269 </pre>
24271 <pre>
24272 enumeration-constant
24273 enumeration-constant = constant-expression
24274 </pre>
24276 <pre>
24277 _Atomic ( type-name )
24278 </pre>
24280 <pre>
24281 const
24282 restrict
24283 volatile
24284 _Atomic
24285 </pre>
24287 <pre>
24288 inline
24289 _Noreturn
24290 </pre>
24292 <pre>
24293 _Alignas ( type-name )
24294 _Alignas ( constant-expression )
24295 </pre>
24297 <!--page 484 -->
24298 <pre>
24300 </pre>
24302 <pre>
24303 identifier
24304 ( declarator )
24307 direct-declarator [ type-qualifier-list static assignment-expression ]
24309 direct-declarator ( parameter-type-list )
24311 </pre>
24313 <pre>
24316 </pre>
24318 <pre>
24319 type-qualifier
24320 type-qualifier-list type-qualifier
24321 </pre>
24323 <pre>
24324 parameter-list
24325 parameter-list , ...
24326 </pre>
24328 <pre>
24329 parameter-declaration
24330 parameter-list , parameter-declaration
24331 </pre>
24333 <pre>
24334 declaration-specifiers declarator
24336 </pre>
24338 <pre>
24339 identifier
24340 identifier-list , identifier
24341 </pre>
24343 <pre>
24345 </pre>
24347 <!--page 485 -->
24348 <pre>
24349 pointer
24351 </pre>
24353 <pre>
24354 ( abstract-declarator )
24358 assignment-expression ]
24360 assignment-expression ]
24363 </pre>
24365 <pre>
24366 identifier
24367 </pre>
24369 <pre>
24370 assignment-expression
24371 { initializer-list }
24372 { initializer-list , }
24373 </pre>
24375 <pre>
24378 </pre>
24380 <pre>
24381 designator-list =
24382 </pre>
24384 <pre>
24385 designator
24386 designator-list designator
24387 </pre>
24389 <pre>
24390 [ constant-expression ]
24391 . identifier
24392 </pre>
24394 <!--page 486 -->
24395 <pre>
24396 _Static_assert ( constant-expression , string-literal ) ;
24397 </pre>
24402 <pre>
24403 labeled-statement
24404 compound-statement
24405 expression-statement
24406 selection-statement
24407 iteration-statement
24408 jump-statement
24409 </pre>
24411 <pre>
24412 identifier : statement
24413 case constant-expression : statement
24414 default : statement
24415 </pre>
24417 <pre>
24419 </pre>
24421 <pre>
24422 block-item
24423 block-item-list block-item
24424 </pre>
24426 <pre>
24427 declaration
24428 statement
24429 </pre>
24431 <pre>
24433 </pre>
24435 <pre>
24436 if ( expression ) statement
24437 if ( expression ) statement else statement
24438 switch ( expression ) statement
24439 </pre>
24441 <pre>
24442 while ( expression ) statement
24443 do statement while ( expression ) ;
24444 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
24446 </pre>
24448 <!--page 487 -->
24449 <pre>
24450 goto identifier ;
24451 continue ;
24452 break ;
24454 </pre>
24459 <pre>
24460 external-declaration
24461 translation-unit external-declaration
24462 </pre>
24464 <pre>
24465 function-definition
24466 declaration
24467 </pre>
24469 <pre>
24471 </pre>
24473 <pre>
24474 declaration
24475 declaration-list declaration
24476 </pre>
24481 <pre>
24483 </pre>
24485 <pre>
24486 group-part
24487 group group-part
24488 </pre>
24490 <pre>
24491 if-section
24492 control-line
24493 text-line
24494 # non-directive
24495 </pre>
24497 <pre>
24499 </pre>
24501 <pre>
24505 </pre>
24507 <pre>
24508 elif-group
24509 elif-groups elif-group
24510 </pre>
24512 <!--page 488 -->
24513 <pre>
24515 </pre>
24517 <pre>
24519 </pre>
24521 <pre>
24522 # endif new-line
24523 </pre>
24525 <pre>
24526 # include pp-tokens new-line
24527 # define identifier replacement-list new-line
24529 replacement-list new-line
24530 # define identifier lparen ... ) replacement-list new-line
24531 # define identifier lparen identifier-list , ... )
24532 replacement-list new-line
24533 # undef identifier new-line
24534 # line pp-tokens new-line
24537 # new-line
24538 </pre>
24540 <pre>
24542 </pre>
24544 <pre>
24545 pp-tokens new-line
24546 </pre>
24548 <pre>
24549 a ( character not immediately preceded by white-space
24550 </pre>
24552 <pre>
24554 </pre>
24556 <pre>
24557 preprocessing-token
24558 pp-tokens preprocessing-token
24559 </pre>
24561 <!--page 489 -->
24562 <pre>
24563 the new-line character
24564 </pre>
24568 <pre>
24569 (informative)
24570 Library summary
24571 </pre>
24575 <pre>
24576 NDEBUG
24577 static_assert
24578 void assert(scalar expression);
24579 </pre>
24583 <!--page 490 -->
24584 <!--page 491 -->
24585 <pre>
24586 __STDC_NO_COMPLEX__ imaginary
24587 complex _Imaginary_I
24588 _Complex_I I
24589 #pragma STDC CX_LIMITED_RANGE on-off-switch
24590 double complex cacos(double complex z);
24591 float complex cacosf(float complex z);
24592 long double complex cacosl(long double complex z);
24593 double complex casin(double complex z);
24594 float complex casinf(float complex z);
24595 long double complex casinl(long double complex z);
24596 double complex catan(double complex z);
24597 float complex catanf(float complex z);
24598 long double complex catanl(long double complex z);
24599 double complex ccos(double complex z);
24600 float complex ccosf(float complex z);
24601 long double complex ccosl(long double complex z);
24602 double complex csin(double complex z);
24603 float complex csinf(float complex z);
24604 long double complex csinl(long double complex z);
24605 double complex ctan(double complex z);
24606 float complex ctanf(float complex z);
24607 long double complex ctanl(long double complex z);
24608 double complex cacosh(double complex z);
24609 float complex cacoshf(float complex z);
24610 long double complex cacoshl(long double complex z);
24611 double complex casinh(double complex z);
24612 float complex casinhf(float complex z);
24613 long double complex casinhl(long double complex z);
24614 double complex catanh(double complex z);
24615 float complex catanhf(float complex z);
24616 long double complex catanhl(long double complex z);
24617 double complex ccosh(double complex z);
24618 float complex ccoshf(float complex z);
24619 long double complex ccoshl(long double complex z);
24620 double complex csinh(double complex z);
24621 float complex csinhf(float complex z);
24622 long double complex csinhl(long double complex z);
24623 double complex ctanh(double complex z);
24624 float complex ctanhf(float complex z);
24625 long double complex ctanhl(long double complex z);
24626 double complex cexp(double complex z);
24627 float complex cexpf(float complex z);
24628 long double complex cexpl(long double complex z);
24629 double complex clog(double complex z);
24630 float complex clogf(float complex z);
24631 long double complex clogl(long double complex z);
24632 double cabs(double complex z);
24633 float cabsf(float complex z);
24634 long double cabsl(long double complex z);
24635 double complex cpow(double complex x, double complex y);
24636 float complex cpowf(float complex x, float complex y);
24637 long double complex cpowl(long double complex x,
24638 long double complex y);
24639 double complex csqrt(double complex z);
24640 float complex csqrtf(float complex z);
24641 long double complex csqrtl(long double complex z);
24642 double carg(double complex z);
24643 float cargf(float complex z);
24644 long double cargl(long double complex z);
24645 double cimag(double complex z);
24646 float cimagf(float complex z);
24647 long double cimagl(long double complex z);
24648 double complex CMPLX(double x, double y);
24649 float complex CMPLXF(float x, float y);
24650 long double complex CMPLXL(long double x, long double y);
24651 double complex conj(double complex z);
24652 float complex conjf(float complex z);
24653 long double complex conjl(long double complex z);
24654 double complex cproj(double complex z);
24655 float complex cprojf(float complex z);
24656 long double complex cprojl(long double complex z);
24657 double creal(double complex z);
24658 float crealf(float complex z);
24659 long double creall(long double complex z);
24660 </pre>
24664 <pre>
24665 int isalnum(int c);
24666 int isalpha(int c);
24667 int isblank(int c);
24668 int iscntrl(int c);
24669 int isdigit(int c);
24670 int isgraph(int c);
24671 int islower(int c);
24672 int isprint(int c);
24673 int ispunct(int c);
24674 int isspace(int c);
24675 int isupper(int c);
24676 int isxdigit(int c);
24677 int tolower(int c);
24678 int toupper(int c);
24679 </pre>
24683 <pre>
24684 EDOM EILSEQ ERANGE errno
24685 __STDC_WANT_LIB_EXT1__
24686 errno_t
24687 </pre>
24691 <!--page 492 -->
24692 <pre>
24693 fenv_t FE_OVERFLOW FE_TOWARDZERO
24694 fexcept_t FE_UNDERFLOW FE_UPWARD
24695 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
24696 FE_INEXACT FE_DOWNWARD
24697 FE_INVALID FE_TONEAREST
24698 #pragma STDC FENV_ACCESS on-off-switch
24699 int feclearexcept(int excepts);
24700 int fegetexceptflag(fexcept_t *flagp, int excepts);
24701 int feraiseexcept(int excepts);
24702 int fesetexceptflag(const fexcept_t *flagp,
24703 int excepts);
24704 int fetestexcept(int excepts);
24705 int fegetround(void);
24706 int fesetround(int round);
24707 int fegetenv(fenv_t *envp);
24708 int feholdexcept(fenv_t *envp);
24709 int fesetenv(const fenv_t *envp);
24710 int feupdateenv(const fenv_t *envp);
24711 </pre>
24715 <pre>
24716 FLT_ROUNDS DBL_DIG FLT_MAX
24717 FLT_EVAL_METHOD LDBL_DIG DBL_MAX
24718 FLT_HAS_SUBNORM FLT_MIN_EXP LDBL_MAX
24719 DBL_HAS_SUBNORM DBL_MIN_EXP FLT_EPSILON
24720 LDBL_HAS_SUBNORM LDBL_MIN_EXP DBL_EPSILON
24721 FLT_RADIX FLT_MIN_10_EXP LDBL_EPSILON
24722 FLT_MANT_DIG DBL_MIN_10_EXP FLT_MIN
24723 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_MIN
24724 LDBL_MANT_DIG FLT_MAX_EXP LDBL_MIN
24725 FLT_DECIMAL_DIG DBL_MAX_EXP FLT_TRUE_MIN
24726 DBL_DECIMAL_DIG LDBL_MAX_EXP DBL_TRUE_MIN
24727 LDBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_TRUE_MIN
24728 DECIMAL_DIG DBL_MAX_10_EXP
24729 FLT_DIG LDBL_MAX_10_EXP
24730 </pre>
24733 <h3><a name="B.7" href="#B.7">B.7 Format conversion of integer types <inttypes.h></a></h3>
24734 <!--page 493 -->
24735 <pre>
24736 imaxdiv_t
24737 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
24738 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
24739 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
24740 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
24741 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
24742 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
24743 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
24744 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
24745 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
24746 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
24747 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
24748 intmax_t imaxabs(intmax_t j);
24749 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
24750 intmax_t strtoimax(const char * restrict nptr,
24751 char ** restrict endptr, int base);
24752 uintmax_t strtoumax(const char * restrict nptr,
24753 char ** restrict endptr, int base);
24754 intmax_t wcstoimax(const wchar_t * restrict nptr,
24755 wchar_t ** restrict endptr, int base);
24756 uintmax_t wcstoumax(const wchar_t * restrict nptr,
24757 wchar_t ** restrict endptr, int base);
24758 </pre>
24762 <pre>
24763 and bitor not_eq xor
24764 and_eq compl or xor_eq
24765 bitand not or_eq
24766 </pre>
24770 <pre>
24771 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
24772 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
24773 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
24774 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
24775 CHAR_MIN USHRT_MAX LONG_MAX
24776 </pre>
24780 <pre>
24781 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
24782 NULL LC_COLLATE LC_MONETARY LC_TIME
24783 char *setlocale(int category, const char *locale);
24784 struct lconv *localeconv(void);
24785 </pre>
24789 <!--page 494 -->
24790 <!--page 495 -->
24791 <!--page 496 -->
24792 <!--page 497 -->
24793 <!--page 498 -->
24794 <pre>
24795 float_t FP_INFINITE FP_FAST_FMAL
24796 double_t FP_NAN FP_ILOGB0
24797 HUGE_VAL FP_NORMAL FP_ILOGBNAN
24798 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
24799 HUGE_VALL FP_ZERO MATH_ERREXCEPT
24800 INFINITY FP_FAST_FMA math_errhandling
24801 NAN FP_FAST_FMAF
24802 #pragma STDC FP_CONTRACT on-off-switch
24803 int fpclassify(real-floating x);
24804 int isfinite(real-floating x);
24805 int isinf(real-floating x);
24806 int isnan(real-floating x);
24807 int isnormal(real-floating x);
24808 int signbit(real-floating x);
24809 double acos(double x);
24810 float acosf(float x);
24811 long double acosl(long double x);
24812 double asin(double x);
24813 float asinf(float x);
24814 long double asinl(long double x);
24815 double atan(double x);
24816 float atanf(float x);
24817 long double atanl(long double x);
24818 double atan2(double y, double x);
24819 float atan2f(float y, float x);
24820 long double atan2l(long double y, long double x);
24821 double cos(double x);
24822 float cosf(float x);
24823 long double cosl(long double x);
24824 double sin(double x);
24825 float sinf(float x);
24826 long double sinl(long double x);
24827 double tan(double x);
24828 float tanf(float x);
24829 long double tanl(long double x);
24830 double acosh(double x);
24831 float acoshf(float x);
24832 long double acoshl(long double x);
24833 double asinh(double x);
24834 float asinhf(float x);
24835 long double asinhl(long double x);
24836 double atanh(double x);
24837 float atanhf(float x);
24838 long double atanhl(long double x);
24839 double cosh(double x);
24840 float coshf(float x);
24841 long double coshl(long double x);
24842 double sinh(double x);
24843 float sinhf(float x);
24844 long double sinhl(long double x);
24845 double tanh(double x);
24846 float tanhf(float x);
24847 long double tanhl(long double x);
24848 double exp(double x);
24849 float expf(float x);
24850 long double expl(long double x);
24851 double exp2(double x);
24852 float exp2f(float x);
24853 long double exp2l(long double x);
24854 double expm1(double x);
24855 float expm1f(float x);
24856 long double expm1l(long double x);
24857 double frexp(double value, int *exp);
24858 float frexpf(float value, int *exp);
24859 long double frexpl(long double value, int *exp);
24860 int ilogb(double x);
24861 int ilogbf(float x);
24862 int ilogbl(long double x);
24863 double ldexp(double x, int exp);
24864 float ldexpf(float x, int exp);
24865 long double ldexpl(long double x, int exp);
24866 double log(double x);
24867 float logf(float x);
24868 long double logl(long double x);
24869 double log10(double x);
24870 float log10f(float x);
24871 long double log10l(long double x);
24872 double log1p(double x);
24873 float log1pf(float x);
24874 long double log1pl(long double x);
24875 double log2(double x);
24876 float log2f(float x);
24877 long double log2l(long double x);
24878 double logb(double x);
24879 float logbf(float x);
24880 long double logbl(long double x);
24881 double modf(double value, double *iptr);
24882 float modff(float value, float *iptr);
24883 long double modfl(long double value, long double *iptr);
24884 double scalbn(double x, int n);
24885 float scalbnf(float x, int n);
24886 long double scalbnl(long double x, int n);
24887 double scalbln(double x, long int n);
24888 float scalblnf(float x, long int n);
24889 long double scalblnl(long double x, long int n);
24890 double cbrt(double x);
24891 float cbrtf(float x);
24892 long double cbrtl(long double x);
24893 double fabs(double x);
24894 float fabsf(float x);
24895 long double fabsl(long double x);
24896 double hypot(double x, double y);
24897 float hypotf(float x, float y);
24898 long double hypotl(long double x, long double y);
24899 double pow(double x, double y);
24900 float powf(float x, float y);
24901 long double powl(long double x, long double y);
24902 double sqrt(double x);
24903 float sqrtf(float x);
24904 long double sqrtl(long double x);
24905 double erf(double x);
24906 float erff(float x);
24907 long double erfl(long double x);
24908 double erfc(double x);
24909 float erfcf(float x);
24910 long double erfcl(long double x);
24911 double lgamma(double x);
24912 float lgammaf(float x);
24913 long double lgammal(long double x);
24914 double tgamma(double x);
24915 float tgammaf(float x);
24916 long double tgammal(long double x);
24917 double ceil(double x);
24918 float ceilf(float x);
24919 long double ceill(long double x);
24920 double floor(double x);
24921 float floorf(float x);
24922 long double floorl(long double x);
24923 double nearbyint(double x);
24924 float nearbyintf(float x);
24925 long double nearbyintl(long double x);
24926 double rint(double x);
24927 float rintf(float x);
24928 long double rintl(long double x);
24929 long int lrint(double x);
24930 long int lrintf(float x);
24931 long int lrintl(long double x);
24932 long long int llrint(double x);
24933 long long int llrintf(float x);
24934 long long int llrintl(long double x);
24935 double round(double x);
24936 float roundf(float x);
24937 long double roundl(long double x);
24938 long int lround(double x);
24939 long int lroundf(float x);
24940 long int lroundl(long double x);
24941 long long int llround(double x);
24942 long long int llroundf(float x);
24943 long long int llroundl(long double x);
24944 double trunc(double x);
24945 float truncf(float x);
24946 long double truncl(long double x);
24947 double fmod(double x, double y);
24948 float fmodf(float x, float y);
24949 long double fmodl(long double x, long double y);
24950 double remainder(double x, double y);
24951 float remainderf(float x, float y);
24952 long double remainderl(long double x, long double y);
24953 double remquo(double x, double y, int *quo);
24954 float remquof(float x, float y, int *quo);
24955 long double remquol(long double x, long double y,
24956 int *quo);
24957 double copysign(double x, double y);
24958 float copysignf(float x, float y);
24959 long double copysignl(long double x, long double y);
24960 double nan(const char *tagp);
24961 float nanf(const char *tagp);
24962 long double nanl(const char *tagp);
24963 double nextafter(double x, double y);
24964 float nextafterf(float x, float y);
24965 long double nextafterl(long double x, long double y);
24966 double nexttoward(double x, long double y);
24967 float nexttowardf(float x, long double y);
24968 long double nexttowardl(long double x, long double y);
24969 double fdim(double x, double y);
24970 float fdimf(float x, float y);
24971 long double fdiml(long double x, long double y);
24972 double fmax(double x, double y);
24973 float fmaxf(float x, float y);
24974 long double fmaxl(long double x, long double y);
24975 double fmin(double x, double y);
24976 float fminf(float x, float y);
24977 long double fminl(long double x, long double y);
24978 double fma(double x, double y, double z);
24979 float fmaf(float x, float y, float z);
24980 long double fmal(long double x, long double y,
24981 long double z);
24982 int isgreater(real-floating x, real-floating y);
24983 int isgreaterequal(real-floating x, real-floating y);
24984 int isless(real-floating x, real-floating y);
24985 int islessequal(real-floating x, real-floating y);
24986 int islessgreater(real-floating x, real-floating y);
24987 int isunordered(real-floating x, real-floating y);
24988 </pre>
24992 <pre>
24993 jmp_buf
24994 int setjmp(jmp_buf env);
24995 _Noreturn void longjmp(jmp_buf env, int val);
24996 </pre>
25000 <!--page 499 -->
25001 <pre>
25002 sig_atomic_t SIG_IGN SIGILL SIGTERM
25003 SIG_DFL SIGABRT SIGINT
25004 SIG_ERR SIGFPE SIGSEGV
25005 void (*signal(int sig, void (*func)(int)))(int);
25006 int raise(int sig);
25007 </pre>
25011 <pre>
25012 alignas
25013 __alignas_is_defined
25014 </pre>
25018 <pre>
25019 va_list
25020 type va_arg(va_list ap, type);
25021 void va_copy(va_list dest, va_list src);
25022 void va_end(va_list ap);
25023 void va_start(va_list ap, parmN);
25024 </pre>
25028 <!--page 500 -->
25029 <!--page 501 -->
25030 <pre>
25031 ATOMIC_CHAR_LOCK_FREE atomic_uint
25032 ATOMIC_CHAR16_T_LOCK_FREE atomic_long
25033 ATOMIC_CHAR32_T_LOCK_FREE atomic_ulong
25034 ATOMIC_WCHAR_T_LOCK_FREE atomic_llong
25035 ATOMIC_SHORT_LOCK_FREE atomic_ullong
25036 ATOMIC_INT_LOCK_FREE atomic_char16_t
25037 ATOMIC_LONG_LOCK_FREE atomic_char32_t
25038 ATOMIC_LLONG_LOCK_FREE atomic_wchar_t
25039 ATOMIC_ADDRESS_LOCK_FREE atomic_int_least8_t
25040 ATOMIC_FLAG_INIT atomic_uint_least8_t
25041 memory_order atomic_int_least16_t
25042 atomic_flag atomic_uint_least16_t
25043 atomic_bool atomic_int_least32_t
25044 atomic_address atomic_uint_least32_t
25045 memory_order_relaxed atomic_int_least64_t
25046 memory_order_consume atomic_uint_least64_t
25047 memory_order_acquire atomic_int_fast8_t
25048 memory_order_release atomic_uint_fast8_t
25049 memory_order_acq_rel atomic_int_fast16_t
25050 memory_order_seq_cst atomic_uint_fast16_t
25051 atomic_char atomic_int_fast32_t
25052 atomic_schar atomic_uint_fast32_t
25053 atomic_uchar atomic_int_fast64_t
25054 atomic_short atomic_uint_fast64_t
25055 atomic_ushort atomic_intptr_t
25056 atomic_int atomic_uintptr_t
25057 atomic_size_t atomic_intmax_t
25058 atomic_ptrdiff_t atomic_uintmax_t
25059 #define ATOMIC_VAR_INIT(C value)
25060 void atomic_init(volatile A *obj, C value);
25061 type kill_dependency(type y);
25062 void atomic_thread_fence(memory_order order);
25063 void atomic_signal_fence(memory_order order);
25064 _Bool atomic_is_lock_free(atomic_type const volatile *obj);
25065 void atomic_store(volatile A *object, C desired);
25066 void atomic_store_explicit(volatile A *object,
25067 C desired, memory_order order);
25068 C atomic_load(volatile A *object);
25069 C atomic_load_explicit(volatile A *object,
25070 memory_order order);
25071 C atomic_exchange(volatile A *object, C desired);
25072 C atomic_exchange_explicit(volatile A *object,
25073 C desired, memory_order order);
25074 _Bool atomic_compare_exchange_strong(volatile A *object,
25075 C *expected, C desired);
25076 _Bool atomic_compare_exchange_strong_explicit(
25077 volatile A *object, C *expected, C desired,
25078 memory_order success, memory_order failure);
25079 _Bool atomic_compare_exchange_weak(volatile A *object,
25080 C *expected, C desired);
25081 _Bool atomic_compare_exchange_weak_explicit(
25082 volatile A *object, C *expected, C desired,
25083 memory_order success, memory_order failure);
25084 C atomic_fetch_key(volatile A *object, M operand);
25085 C atomic_fetch_key_explicit(volatile A *object,
25086 M operand, memory_order order);
25087 bool atomic_flag_test_and_set(
25088 volatile atomic_flag *object);
25089 bool atomic_flag_test_and_set_explicit(
25090 volatile atomic_flag *object, memory_order order);
25091 void atomic_flag_clear(volatile atomic_flag *object);
25092 void atomic_flag_clear_explicit(
25093 volatile atomic_flag *object, memory_order order);
25094 </pre>
25098 <pre>
25099 bool
25100 true
25101 false
25102 __bool_true_false_are_defined
25103 </pre>
25107 <pre>
25108 ptrdiff_t max_align_t NULL
25109 size_t wchar_t
25110 offsetof(type, member-designator)
25111 __STDC_WANT_LIB_EXT1__
25112 rsize_t
25113 </pre>
25117 <!--page 502 -->
25118 <pre>
25119 intN_t INT_LEASTN_MIN PTRDIFF_MAX
25120 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
25121 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
25122 uint_leastN_t INT_FASTN_MIN SIZE_MAX
25123 int_fastN_t INT_FASTN_MAX WCHAR_MIN
25124 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
25125 intptr_t INTPTR_MIN WINT_MIN
25126 uintptr_t INTPTR_MAX WINT_MAX
25127 intmax_t UINTPTR_MAX INTN_C(value)
25128 uintmax_t INTMAX_MIN UINTN_C(value)
25129 INTN_MIN INTMAX_MAX INTMAX_C(value)
25130 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
25131 UINTN_MAX PTRDIFF_MIN
25132 __STDC_WANT_LIB_EXT1__
25133 RSIZE_MAX
25134 </pre>
25138 <!--page 503 -->
25139 <!--page 504 -->
25140 <!--page 505 -->
25141 <pre>
25142 size_t _IOLBF FILENAME_MAX TMP_MAX
25143 FILE _IONBF L_tmpnam stderr
25144 fpos_t BUFSIZ SEEK_CUR stdin
25145 NULL EOF SEEK_END stdout
25146 _IOFBF FOPEN_MAX SEEK_SET
25147 int remove(const char *filename);
25148 int rename(const char *old, const char *new);
25149 FILE *tmpfile(void);
25150 char *tmpnam(char *s);
25151 int fclose(FILE *stream);
25152 int fflush(FILE *stream);
25153 FILE *fopen(const char * restrict filename,
25154 const char * restrict mode);
25155 FILE *freopen(const char * restrict filename,
25156 const char * restrict mode,
25157 FILE * restrict stream);
25158 void setbuf(FILE * restrict stream,
25159 char * restrict buf);
25160 int setvbuf(FILE * restrict stream,
25161 char * restrict buf,
25162 int mode, size_t size);
25163 int fprintf(FILE * restrict stream,
25164 const char * restrict format, ...);
25165 int fscanf(FILE * restrict stream,
25166 const char * restrict format, ...);
25167 int printf(const char * restrict format, ...);
25168 int scanf(const char * restrict format, ...);
25169 int snprintf(char * restrict s, size_t n,
25170 const char * restrict format, ...);
25171 int sprintf(char * restrict s,
25172 const char * restrict format, ...);
25173 int sscanf(const char * restrict s,
25174 const char * restrict format, ...);
25175 int vfprintf(FILE * restrict stream,
25176 const char * restrict format, va_list arg);
25177 int vfscanf(FILE * restrict stream,
25178 const char * restrict format, va_list arg);
25179 int vprintf(const char * restrict format, va_list arg);
25180 int vscanf(const char * restrict format, va_list arg);
25181 int vsnprintf(char * restrict s, size_t n,
25182 const char * restrict format, va_list arg);
25183 int vsprintf(char * restrict s,
25184 const char * restrict format, va_list arg);
25185 int vsscanf(const char * restrict s,
25186 const char * restrict format, va_list arg);
25187 int fgetc(FILE *stream);
25188 char *fgets(char * restrict s, int n,
25189 FILE * restrict stream);
25190 int fputc(int c, FILE *stream);
25191 int fputs(const char * restrict s,
25192 FILE * restrict stream);
25193 int getc(FILE *stream);
25194 int getchar(void);
25195 int putc(int c, FILE *stream); *
25196 int putchar(int c);
25197 int puts(const char *s);
25198 int ungetc(int c, FILE *stream);
25199 size_t fread(void * restrict ptr,
25200 size_t size, size_t nmemb,
25201 FILE * restrict stream);
25202 size_t fwrite(const void * restrict ptr,
25203 size_t size, size_t nmemb,
25204 FILE * restrict stream);
25205 int fgetpos(FILE * restrict stream,
25206 fpos_t * restrict pos);
25207 int fseek(FILE *stream, long int offset, int whence);
25208 int fsetpos(FILE *stream, const fpos_t *pos);
25209 long int ftell(FILE *stream);
25210 void rewind(FILE *stream);
25211 void clearerr(FILE *stream);
25212 int feof(FILE *stream);
25213 int ferror(FILE *stream);
25214 void perror(const char *s);
25215 __STDC_WANT_LIB_EXT1__
25216 L_tmpnam_s TMP_MAX_S errno_t rsize_t
25217 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
25218 errno_t tmpnam_s(char *s, rsize_t maxsize);
25219 errno_t fopen_s(FILE * restrict * restrict streamptr,
25220 const char * restrict filename,
25221 const char * restrict mode);
25222 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
25223 const char * restrict filename,
25224 const char * restrict mode,
25225 FILE * restrict stream);
25226 int fprintf_s(FILE * restrict stream,
25227 const char * restrict format, ...);
25228 int fscanf_s(FILE * restrict stream,
25229 const char * restrict format, ...);
25230 int printf_s(const char * restrict format, ...);
25231 int scanf_s(const char * restrict format, ...);
25232 int snprintf_s(char * restrict s, rsize_t n,
25233 const char * restrict format, ...);
25234 int sprintf_s(char * restrict s, rsize_t n,
25235 const char * restrict format, ...);
25236 int sscanf_s(const char * restrict s,
25237 const char * restrict format, ...);
25238 int vfprintf_s(FILE * restrict stream,
25239 const char * restrict format,
25240 va_list arg);
25241 int vfscanf_s(FILE * restrict stream,
25242 const char * restrict format,
25243 va_list arg);
25244 int vprintf_s(const char * restrict format,
25245 va_list arg);
25246 int vscanf_s(const char * restrict format,
25247 va_list arg);
25248 int vsnprintf_s(char * restrict s, rsize_t n,
25249 const char * restrict format,
25250 va_list arg);
25251 int vsprintf_s(char * restrict s, rsize_t n,
25252 const char * restrict format,
25253 va_list arg);
25254 int vsscanf_s(const char * restrict s,
25255 const char * restrict format,
25256 va_list arg);
25257 char *gets_s(char *s, rsize_t n);
25258 </pre>
25262 <!--page 506 -->
25263 <!--page 507 -->
25264 <pre>
25265 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
25266 wchar_t lldiv_t EXIT_SUCCESS
25267 div_t NULL RAND_MAX
25268 double atof(const char *nptr);
25269 int atoi(const char *nptr);
25270 long int atol(const char *nptr);
25271 long long int atoll(const char *nptr);
25272 double strtod(const char * restrict nptr,
25273 char ** restrict endptr);
25274 float strtof(const char * restrict nptr,
25275 char ** restrict endptr);
25276 long double strtold(const char * restrict nptr,
25277 char ** restrict endptr);
25278 long int strtol(const char * restrict nptr,
25279 char ** restrict endptr, int base);
25280 long long int strtoll(const char * restrict nptr,
25281 char ** restrict endptr, int base);
25282 unsigned long int strtoul(
25283 const char * restrict nptr,
25284 char ** restrict endptr, int base);
25285 unsigned long long int strtoull(
25286 const char * restrict nptr,
25287 char ** restrict endptr, int base);
25288 int rand(void);
25289 void srand(unsigned int seed);
25290 void *aligned_alloc(size_t alignment, size_t size);
25291 void *calloc(size_t nmemb, size_t size);
25292 void free(void *ptr);
25293 void *malloc(size_t size);
25294 void *realloc(void *ptr, size_t size);
25295 _Noreturn void abort(void);
25296 int atexit(void (*func)(void));
25297 int at_quick_exit(void (*func)(void));
25298 _Noreturn void exit(int status);
25299 _Noreturn void _Exit(int status);
25300 char *getenv(const char *name);
25301 _Noreturn void quick_exit(int status);
25302 int system(const char *string);
25303 void *bsearch(const void *key, const void *base,
25304 size_t nmemb, size_t size,
25305 int (*compar)(const void *, const void *));
25306 void qsort(void *base, size_t nmemb, size_t size,
25307 int (*compar)(const void *, const void *));
25308 int abs(int j);
25309 long int labs(long int j);
25310 long long int llabs(long long int j);
25311 div_t div(int numer, int denom);
25312 ldiv_t ldiv(long int numer, long int denom);
25313 lldiv_t lldiv(long long int numer,
25314 long long int denom);
25315 int mblen(const char *s, size_t n);
25316 int mbtowc(wchar_t * restrict pwc,
25317 const char * restrict s, size_t n);
25318 int wctomb(char *s, wchar_t wchar);
25319 size_t mbstowcs(wchar_t * restrict pwcs,
25320 const char * restrict s, size_t n);
25321 size_t wcstombs(char * restrict s,
25322 const wchar_t * restrict pwcs, size_t n);
25323 __STDC_WANT_LIB_EXT1__
25324 errno_t
25325 rsize_t
25326 constraint_handler_t
25327 constraint_handler_t set_constraint_handler_s(
25328 constraint_handler_t handler);
25329 void abort_handler_s(
25330 const char * restrict msg,
25331 void * restrict ptr,
25332 errno_t error);
25333 void ignore_handler_s(
25334 const char * restrict msg,
25335 void * restrict ptr,
25336 errno_t error);
25337 errno_t getenv_s(size_t * restrict len,
25338 char * restrict value, rsize_t maxsize,
25339 const char * restrict name);
25340 void *bsearch_s(const void *key, const void *base,
25341 rsize_t nmemb, rsize_t size,
25342 int (*compar)(const void *k, const void *y,
25343 void *context),
25344 void *context);
25345 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
25346 int (*compar)(const void *x, const void *y,
25347 void *context),
25348 void *context);
25349 errno_t wctomb_s(int * restrict status,
25350 char * restrict s,
25351 rsize_t smax,
25352 wchar_t wc);
25353 errno_t mbstowcs_s(size_t * restrict retval,
25354 wchar_t * restrict dst, rsize_t dstmax,
25355 const char * restrict src, rsize_t len);
25356 errno_t wcstombs_s(size_t * restrict retval,
25357 char * restrict dst, rsize_t dstmax,
25358 const wchar_t * restrict src, rsize_t len);
25359 </pre>
25363 <!--page 508 -->
25364 <!--page 509 -->
25365 <pre>
25366 size_t
25367 NULL
25368 void *memcpy(void * restrict s1,
25369 const void * restrict s2, size_t n);
25370 void *memmove(void *s1, const void *s2, size_t n);
25371 char *strcpy(char * restrict s1,
25372 const char * restrict s2);
25373 char *strncpy(char * restrict s1,
25374 const char * restrict s2, size_t n);
25375 char *strcat(char * restrict s1,
25376 const char * restrict s2);
25377 char *strncat(char * restrict s1,
25378 const char * restrict s2, size_t n);
25379 int memcmp(const void *s1, const void *s2, size_t n);
25380 int strcmp(const char *s1, const char *s2);
25381 int strcoll(const char *s1, const char *s2);
25382 int strncmp(const char *s1, const char *s2, size_t n);
25383 size_t strxfrm(char * restrict s1,
25384 const char * restrict s2, size_t n);
25385 void *memchr(const void *s, int c, size_t n);
25386 char *strchr(const char *s, int c);
25387 size_t strcspn(const char *s1, const char *s2);
25388 char *strpbrk(const char *s1, const char *s2);
25389 char *strrchr(const char *s, int c);
25390 size_t strspn(const char *s1, const char *s2);
25391 char *strstr(const char *s1, const char *s2);
25392 char *strtok(char * restrict s1,
25393 const char * restrict s2);
25394 void *memset(void *s, int c, size_t n);
25395 char *strerror(int errnum);
25396 size_t strlen(const char *s);
25397 __STDC_WANT_LIB_EXT1__
25398 errno_t
25399 rsize_t
25400 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
25401 const void * restrict s2, rsize_t n);
25402 errno_t memmove_s(void *s1, rsize_t s1max,
25403 const void *s2, rsize_t n);
25404 errno_t strcpy_s(char * restrict s1,
25405 rsize_t s1max,
25406 const char * restrict s2);
25407 errno_t strncpy_s(char * restrict s1,
25408 rsize_t s1max,
25409 const char * restrict s2,
25410 rsize_t n);
25411 errno_t strcat_s(char * restrict s1,
25412 rsize_t s1max,
25413 const char * restrict s2);
25414 errno_t strncat_s(char * restrict s1,
25415 rsize_t s1max,
25416 const char * restrict s2,
25417 rsize_t n);
25418 char *strtok_s(char * restrict s1,
25419 rsize_t * restrict s1max,
25420 const char * restrict s2,
25421 char ** restrict ptr);
25422 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
25423 errno_t strerror_s(char *s, rsize_t maxsize,
25424 errno_t errnum);
25425 size_t strerrorlen_s(errno_t errnum);
25426 size_t strnlen_s(const char *s, size_t maxsize);
25427 </pre>
25431 <pre>
25432 acos sqrt fmod nextafter
25433 asin fabs frexp nexttoward
25434 atan atan2 hypot remainder
25435 acosh cbrt ilogb remquo
25436 asinh ceil ldexp rint
25437 atanh copysign lgamma round
25438 cos erf llrint scalbn
25439 sin erfc llround scalbln
25440 tan exp2 log10 tgamma
25441 cosh expm1 log1p trunc
25442 sinh fdim log2 carg
25443 tanh floor logb cimag
25444 exp fma lrint conj
25445 log fmax lround cproj
25446 pow fmin nearbyint creal
25447 </pre>
25451 <!--page 510 -->
25452 <pre>
25453 ONCE_FLAG_INIT mtx_plain
25454 TSS_DTOR_ITERATIONS mtx_recursive
25455 cnd_t mtx_timed
25456 thrd_t mtx_try
25457 tss_t thrd_timeout
25458 mtx_t thrd_success
25459 tss_dtor_t thrd_busy
25460 thrd_start_t thrd_error
25461 once_flag thrd_nomem
25462 xtime
25463 void call_once(once_flag *flag, void (*func)(void));
25464 int cnd_broadcast(cnd_t *cond);
25465 void cnd_destroy(cnd_t *cond);
25466 int cnd_init(cnd_t *cond);
25467 int cnd_signal(cnd_t *cond);
25468 int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
25469 const xtime *xt);
25470 int cnd_wait(cnd_t *cond, mtx_t *mtx);
25471 void mtx_destroy(mtx_t *mtx);
25472 int mtx_init(mtx_t *mtx, int type);
25473 int mtx_lock(mtx_t *mtx);
25474 int mtx_timedlock(mtx_t *mtx, const xtime *xt);
25475 int mtx_trylock(mtx_t *mtx);
25476 int mtx_unlock(mtx_t *mtx);
25477 int thrd_create(thrd_t *thr, thrd_start_t func,
25478 void *arg);
25479 thrd_t thrd_current(void);
25480 int thrd_detach(thrd_t thr);
25481 int thrd_equal(thrd_t thr0, thrd_t thr1);
25482 void thrd_exit(int res);
25483 int thrd_join(thrd_t thr, int *res);
25484 void thrd_sleep(const xtime *xt);
25485 void thrd_yield(void);
25486 int tss_create(tss_t *key, tss_dtor_t dtor);
25487 void tss_delete(tss_t key);
25488 void *tss_get(tss_t key);
25489 int tss_set(tss_t key, void *val);
25490 int xtime_get(xtime *xt, int base);
25491 </pre>
25495 <!--page 511 -->
25496 <pre>
25497 NULL size_t time_t
25498 CLOCKS_PER_SEC clock_t struct tm
25499 clock_t clock(void);
25500 double difftime(time_t time1, time_t time0);
25501 time_t mktime(struct tm *timeptr);
25502 time_t time(time_t *timer);
25503 char *asctime(const struct tm *timeptr);
25504 char *ctime(const time_t *timer);
25505 struct tm *gmtime(const time_t *timer);
25506 struct tm *localtime(const time_t *timer);
25507 size_t strftime(char * restrict s,
25508 size_t maxsize,
25509 const char * restrict format,
25510 const struct tm * restrict timeptr);
25511 __STDC_WANT_LIB_EXT1__
25512 errno_t
25513 rsize_t
25514 errno_t asctime_s(char *s, rsize_t maxsize,
25515 const struct tm *timeptr);
25516 errno_t ctime_s(char *s, rsize_t maxsize,
25517 const time_t *timer);
25518 struct tm *gmtime_s(const time_t * restrict timer,
25519 struct tm * restrict result);
25520 struct tm *localtime_s(const time_t * restrict timer,
25521 struct tm * restrict result);
25522 </pre>
25526 <pre>
25527 mbstate_t size_t char16_t char32_t
25528 size_t mbrtoc16(char16_t * restrict pc16,
25529 const char * restrict s, size_t n,
25530 mbstate_t * restrict ps);
25531 size_t c16rtomb(char * restrict s, char16_t c16,
25532 mbstate_t * restrict ps);
25533 size_t mbrtoc32(char32_t * restrict pc32,
25534 const char * restrict s, size_t n,
25535 mbstate_t * restrict ps);
25536 size_t c32rtomb(char * restrict s, char32_t c32,
25537 mbstate_t * restrict ps);
25538 </pre>
25541 <h3><a name="B.27" href="#B.27">B.27 Extended multibyte/wide character utilities <wchar.h></a></h3>
25542 <!--page 512 -->
25543 <!--page 513 -->
25544 <!--page 514 -->
25545 <!--page 515 -->
25546 <!--page 516 -->
25547 <pre>
25548 wchar_t wint_t WCHAR_MAX
25549 size_t struct tm WCHAR_MIN
25550 mbstate_t NULL WEOF
25551 int fwprintf(FILE * restrict stream,
25552 const wchar_t * restrict format, ...);
25553 int fwscanf(FILE * restrict stream,
25554 const wchar_t * restrict format, ...);
25555 int swprintf(wchar_t * restrict s, size_t n,
25556 const wchar_t * restrict format, ...);
25557 int swscanf(const wchar_t * restrict s,
25558 const wchar_t * restrict format, ...);
25559 int vfwprintf(FILE * restrict stream,
25560 const wchar_t * restrict format, va_list arg);
25561 int vfwscanf(FILE * restrict stream,
25562 const wchar_t * restrict format, va_list arg);
25563 int vswprintf(wchar_t * restrict s, size_t n,
25564 const wchar_t * restrict format, va_list arg);
25565 int vswscanf(const wchar_t * restrict s,
25566 const wchar_t * restrict format, va_list arg);
25567 int vwprintf(const wchar_t * restrict format,
25568 va_list arg);
25569 int vwscanf(const wchar_t * restrict format,
25570 va_list arg);
25571 int wprintf(const wchar_t * restrict format, ...);
25572 int wscanf(const wchar_t * restrict format, ...);
25573 wint_t fgetwc(FILE *stream);
25574 wchar_t *fgetws(wchar_t * restrict s, int n,
25575 FILE * restrict stream);
25576 wint_t fputwc(wchar_t c, FILE *stream);
25577 int fputws(const wchar_t * restrict s,
25578 FILE * restrict stream);
25579 int fwide(FILE *stream, int mode);
25580 wint_t getwc(FILE *stream);
25581 wint_t getwchar(void);
25582 wint_t putwc(wchar_t c, FILE *stream);
25583 wint_t putwchar(wchar_t c);
25584 wint_t ungetwc(wint_t c, FILE *stream);
25585 double wcstod(const wchar_t * restrict nptr,
25586 wchar_t ** restrict endptr);
25587 float wcstof(const wchar_t * restrict nptr,
25588 wchar_t ** restrict endptr);
25589 long double wcstold(const wchar_t * restrict nptr,
25590 wchar_t ** restrict endptr);
25591 long int wcstol(const wchar_t * restrict nptr,
25592 wchar_t ** restrict endptr, int base);
25593 long long int wcstoll(const wchar_t * restrict nptr,
25594 wchar_t ** restrict endptr, int base);
25595 unsigned long int wcstoul(const wchar_t * restrict nptr,
25596 wchar_t ** restrict endptr, int base);
25597 unsigned long long int wcstoull(
25598 const wchar_t * restrict nptr,
25599 wchar_t ** restrict endptr, int base);
25600 wchar_t *wcscpy(wchar_t * restrict s1,
25601 const wchar_t * restrict s2);
25602 wchar_t *wcsncpy(wchar_t * restrict s1,
25603 const wchar_t * restrict s2, size_t n);
25604 wchar_t *wmemcpy(wchar_t * restrict s1,
25605 const wchar_t * restrict s2, size_t n);
25606 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
25607 size_t n);
25608 wchar_t *wcscat(wchar_t * restrict s1,
25609 const wchar_t * restrict s2);
25610 wchar_t *wcsncat(wchar_t * restrict s1,
25611 const wchar_t * restrict s2, size_t n);
25612 int wcscmp(const wchar_t *s1, const wchar_t *s2);
25613 int wcscoll(const wchar_t *s1, const wchar_t *s2);
25614 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
25615 size_t n);
25616 size_t wcsxfrm(wchar_t * restrict s1,
25617 const wchar_t * restrict s2, size_t n);
25618 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
25619 size_t n);
25620 wchar_t *wcschr(const wchar_t *s, wchar_t c);
25621 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
25622 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
25623 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
25624 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
25625 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
25626 wchar_t *wcstok(wchar_t * restrict s1,
25627 const wchar_t * restrict s2,
25628 wchar_t ** restrict ptr);
25629 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
25630 size_t wcslen(const wchar_t *s);
25631 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
25632 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
25633 const wchar_t * restrict format,
25634 const struct tm * restrict timeptr);
25635 wint_t btowc(int c);
25636 int wctob(wint_t c);
25637 int mbsinit(const mbstate_t *ps);
25638 size_t mbrlen(const char * restrict s, size_t n,
25639 mbstate_t * restrict ps);
25640 size_t mbrtowc(wchar_t * restrict pwc,
25641 const char * restrict s, size_t n,
25642 mbstate_t * restrict ps);
25643 size_t wcrtomb(char * restrict s, wchar_t wc,
25644 mbstate_t * restrict ps);
25645 size_t mbsrtowcs(wchar_t * restrict dst,
25646 const char ** restrict src, size_t len,
25647 mbstate_t * restrict ps);
25648 size_t wcsrtombs(char * restrict dst,
25649 const wchar_t ** restrict src, size_t len,
25650 mbstate_t * restrict ps);
25651 __STDC_WANT_LIB_EXT1__
25652 errno_t
25653 rsize_t
25654 int fwprintf_s(FILE * restrict stream,
25655 const wchar_t * restrict format, ...);
25656 int fwscanf_s(FILE * restrict stream,
25657 const wchar_t * restrict format, ...);
25658 int snwprintf_s(wchar_t * restrict s,
25659 rsize_t n,
25660 const wchar_t * restrict format, ...);
25661 int swprintf_s(wchar_t * restrict s, rsize_t n,
25662 const wchar_t * restrict format, ...);
25663 int swscanf_s(const wchar_t * restrict s,
25664 const wchar_t * restrict format, ...);
25665 int vfwprintf_s(FILE * restrict stream,
25666 const wchar_t * restrict format,
25667 va_list arg);
25668 int vfwscanf_s(FILE * restrict stream,
25669 const wchar_t * restrict format, va_list arg);
25670 int vsnwprintf_s(wchar_t * restrict s,
25671 rsize_t n,
25672 const wchar_t * restrict format,
25673 va_list arg);
25674 int vswprintf_s(wchar_t * restrict s,
25675 rsize_t n,
25676 const wchar_t * restrict format,
25677 va_list arg);
25678 int vswscanf_s(const wchar_t * restrict s,
25679 const wchar_t * restrict format,
25680 va_list arg);
25681 int vwprintf_s(const wchar_t * restrict format,
25682 va_list arg);
25683 int vwscanf_s(const wchar_t * restrict format,
25684 va_list arg);
25685 int wprintf_s(const wchar_t * restrict format, ...);
25686 int wscanf_s(const wchar_t * restrict format, ...);
25687 errno_t wcscpy_s(wchar_t * restrict s1,
25688 rsize_t s1max,
25689 const wchar_t * restrict s2);
25690 errno_t wcsncpy_s(wchar_t * restrict s1,
25691 rsize_t s1max,
25692 const wchar_t * restrict s2,
25693 rsize_t n);
25694 errno_t wmemcpy_s(wchar_t * restrict s1,
25695 rsize_t s1max,
25696 const wchar_t * restrict s2,
25697 rsize_t n);
25698 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
25699 const wchar_t *s2, rsize_t n);
25700 errno_t wcscat_s(wchar_t * restrict s1,
25701 rsize_t s1max,
25702 const wchar_t * restrict s2);
25703 errno_t wcsncat_s(wchar_t * restrict s1,
25704 rsize_t s1max,
25705 const wchar_t * restrict s2,
25706 rsize_t n);
25707 wchar_t *wcstok_s(wchar_t * restrict s1,
25708 rsize_t * restrict s1max,
25709 const wchar_t * restrict s2,
25710 wchar_t ** restrict ptr);
25711 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
25712 errno_t wcrtomb_s(size_t * restrict retval,
25713 char * restrict s, rsize_t smax,
25714 wchar_t wc, mbstate_t * restrict ps);
25715 errno_t mbsrtowcs_s(size_t * restrict retval,
25716 wchar_t * restrict dst, rsize_t dstmax,
25717 const char ** restrict src, rsize_t len,
25718 mbstate_t * restrict ps);
25719 errno_t wcsrtombs_s(size_t * restrict retval,
25720 char * restrict dst, rsize_t dstmax,
25721 const wchar_t ** restrict src, rsize_t len,
25722 mbstate_t * restrict ps);
25723 </pre>
25726 <h3><a name="B.28" href="#B.28">B.28 Wide character classification and mapping utilities <wctype.h></a></h3>
25727 <!--page 517 -->
25728 <pre>
25729 wint_t wctrans_t wctype_t WEOF
25730 int iswalnum(wint_t wc);
25731 int iswalpha(wint_t wc);
25732 int iswblank(wint_t wc);
25733 int iswcntrl(wint_t wc);
25734 int iswdigit(wint_t wc);
25735 int iswgraph(wint_t wc);
25736 int iswlower(wint_t wc);
25737 int iswprint(wint_t wc);
25738 int iswpunct(wint_t wc);
25739 int iswspace(wint_t wc);
25740 int iswupper(wint_t wc);
25741 int iswxdigit(wint_t wc);
25742 int iswctype(wint_t wc, wctype_t desc);
25743 wctype_t wctype(const char *property);
25744 wint_t towlower(wint_t wc);
25745 wint_t towupper(wint_t wc);
25746 wint_t towctrans(wint_t wc, wctrans_t desc);
25747 wctrans_t wctrans(const char *property);
25748 </pre>
25752 <pre>
25753 (informative)
25754 Sequence points
25755 </pre>
25758 <ul>
25759 <li> Between the evaluations of the function designator and actual arguments in a function
25761 <li> Between the evaluations of the first and second operands of the following operators:
25762 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>). *
25763 <li> Between the evaluations of the first operand of the conditional ? : operator and
25766 <li> Between the evaluation of a full expression and the next full expression to be
25767 evaluated. The following are full expressions: an initializer that is not part of a
25768 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
25769 controlling expression of a selection statement (if or switch) (<a href="#6.8.4">6.8.4</a>); the
25770 controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the (optional)
25771 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the (optional) expression in a return
25774 <li> After the actions associated with each formatted input/output function conversion
25776 <li> Immediately before and immediately after each call to a comparison function, and
25777 also between any call to a comparison function and any movement of the objects
25779 <!--page 518 -->
25780 </ul>
25784 <pre>
25785 (normative)
25786 Universal character names for identifiers
25787 </pre>
25789 This clause lists the hexadecimal code values that are valid in universal character names
25790 in identifiers.
25806 3040-D7FF
25808 F900-FD3D, FD40-FDCF, FDF0-FE44, FE47-FFFD
25812 B0000-BFFFD, C0000-CFFFD, D0000-DFFFD, E0000-EFFFD
25818 <!--page 519 -->
25822 <pre>
25823 (informative)
25824 Implementation limits
25825 </pre>
25827 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
25828 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
25829 with the same sign. The values shall all be constant expressions suitable for use in #if
25830 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
25831 <pre>
25832 #define CHAR_BIT 8
25833 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
25834 #define CHAR_MIN 0 or SCHAR_MIN
25835 #define INT_MAX +32767
25836 #define INT_MIN -32767
25837 #define LONG_MAX +2147483647
25838 #define LONG_MIN -2147483647
25839 #define LLONG_MAX +9223372036854775807
25840 #define LLONG_MIN -9223372036854775807
25841 #define MB_LEN_MAX 1
25842 #define SCHAR_MAX +127
25843 #define SCHAR_MIN -127
25844 #define SHRT_MAX +32767
25845 #define SHRT_MIN -32767
25846 #define UCHAR_MAX 255
25847 #define USHRT_MAX 65535
25848 #define UINT_MAX 65535
25849 #define ULONG_MAX 4294967295
25850 #define ULLONG_MAX 18446744073709551615
25851 </pre>
25853 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
25854 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
25855 directives; all floating values shall be constant expressions. The components are
25858 The values given in the following list shall be replaced by implementation-defined
25859 expressions:
25860 <pre>
25861 #define FLT_EVAL_METHOD
25862 #define FLT_ROUNDS
25863 </pre>
25865 The values given in the following list shall be replaced by implementation-defined
25866 constant expressions that are greater or equal in magnitude (absolute value) to those
25867 shown, with the same sign:
25868 <!--page 520 -->
25869 <pre>
25870 #define DLB_DECIMAL_DIG 10
25871 #define DBL_DIG 10
25872 #define DBL_MANT_DIG
25873 #define DBL_MAX_10_EXP +37
25874 #define DBL_MAX_EXP
25875 #define DBL_MIN_10_EXP -37
25876 #define DBL_MIN_EXP
25877 #define DECIMAL_DIG 10
25878 #define FLT_DECIMAL_DIG 6
25879 #define FLT_DIG 6
25880 #define FLT_MANT_DIG
25881 #define FLT_MAX_10_EXP +37
25882 #define FLT_MAX_EXP
25883 #define FLT_MIN_10_EXP -37
25884 #define FLT_MIN_EXP
25885 #define FLT_RADIX 2
25886 #define LDLB_DECIMAL_DIG 10
25887 #define LDBL_DIG 10
25888 #define LDBL_MANT_DIG
25889 #define LDBL_MAX_10_EXP +37
25890 #define LDBL_MAX_EXP
25891 #define LDBL_MIN_10_EXP -37
25892 #define LDBL_MIN_EXP
25893 </pre>
25895 The values given in the following list shall be replaced by implementation-defined
25896 constant expressions with values that are greater than or equal to those shown:
25897 <pre>
25898 #define DBL_MAX 1E+37
25899 #define FLT_MAX 1E+37
25900 #define LDBL_MAX 1E+37
25901 </pre>
25903 The values given in the following list shall be replaced by implementation-defined
25904 constant expressions with (positive) values that are less than or equal to those shown:
25905 <!--page 521 -->
25906 <pre>
25907 #define DBL_EPSILON 1E-9
25908 #define DBL_MIN 1E-37
25909 #define FLT_EPSILON 1E-5
25910 #define FLT_MIN 1E-37
25911 #define LDBL_EPSILON 1E-9
25912 #define LDBL_MIN 1E-37
25913 </pre>
25917 <pre>
25918 (normative)
25919 IEC 60559 floating-point arithmetic
25920 </pre>
25925 This annex specifies C language support for the IEC 60559 floating-point standard. The
25926 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
25931 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
25933 defines __STDC_IEC_559__ shall conform to the specifications in this annex.<sup><a href="#note343"><b>343)</b></a></sup>
25934 Where a binding between the C language and IEC 60559 is indicated, the
25935 IEC 60559-specified behavior is adopted by reference, unless stated otherwise. Since
25936 negative and positive infinity are representable in IEC 60559 formats, all real numbers lie
25937 within the range of representable values.
25940 <p><small><a name="note343" href="#note343">343)</a> Implementations that do not define __STDC_IEC_559__ are not required to conform to these
25941 specifications.
25942 </small>
25947 The C floating types match the IEC 60559 formats as follows:
25948 <ul>
25951 <li> The long double type matches an IEC 60559 extended format,<sup><a href="#note344"><b>344)</b></a></sup> else a
25953 </ul>
25954 Any non-IEC 60559 extended format used for the long double type shall have more
25955 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note345"><b>345)</b></a></sup>
25960 <!--page 522 -->
25963 The long double type should match an IEC 60559 extended format.
25966 <p><small><a name="note344" href="#note344">344)</a> ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
25968 </small>
25969 <p><small><a name="note345" href="#note345">345)</a> A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
25970 all double values.
25971 </small>
25976 This specification does not define the behavior of signaling NaNs.<sup><a href="#note346"><b>346)</b></a></sup> It generally uses
25977 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
25978 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
25981 <p><small><a name="note346" href="#note346">346)</a> Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
25982 sufficient for closure of the arithmetic.
25983 </small>
25988 C operators and functions provide IEC 60559 required and recommended facilities as
25989 listed below.
25990 <ul>
25992 divide operations.
25993 <li> The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
25994 <li> The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
25995 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
25996 with additional information.
25997 <li> The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
25998 floating-point number to an integer value (in the same precision). The nearbyint
25999 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
26000 Appendix to ANSI/IEEE 854.
26002 floating-point precisions.
26004 from integer to floating point.
26006 but always round toward zero.
26007 <li> The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
26008 conversions, which honor the directed rounding mode, from floating point to the
26009 long int and long long int integer formats. The lrint and llrint
26010 functions can be used to implement IEC 60559 conversions from floating to other
26011 integer formats.
26012 <li> The translation time conversion of floating constants and the strtod, strtof,
26013 strtold, fprintf, fscanf, and related library functions in <a href="#7.22"><stdlib.h></a>,
26016 <!--page 523 -->
26017 <a href="#7.21"><stdio.h></a>, and <a href="#7.28"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
26018 strtold function in <a href="#7.22"><stdlib.h></a> provides the conv function recommended in the
26019 Appendix to ANSI/IEEE 854.
26021 identifies a need for additional comparison predicates to facilitate writing code that
26022 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
26024 supplement the language operators to address this need. The islessgreater and
26025 isunordered macros provide respectively a quiet version of the <> predicate and
26026 the unordered predicate recommended in the Appendix to IEC 60559.
26027 <li> The feclearexcept, feraiseexcept, and fetestexcept functions in
26028 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
26029 exception status flags. The fegetexceptflag and fesetexceptflag
26030 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
26031 one time. These functions are used in conjunction with the type fexcept_t and the
26032 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
26034 <li> The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
26035 to select among the IEC 60559 directed rounding modes represented by the rounding
26038 IEC 60559 directed rounding modes.
26039 <li> The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
26040 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
26041 the IEC 60559 status flags and control modes.
26042 <li> The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
26043 recommended in the Appendix to IEC 60559.
26044 <li> The fabs functions in <a href="#7.12"><math.h></a> provide the abs function recommended in the
26045 Appendix to IEC 60559.
26046 <li> The unary minus (-) operator provides the unary minus (-) operation recommended
26047 in the Appendix to IEC 60559.
26048 <li> The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
26049 recommended in the Appendix to IEC 60559.
26050 <li> The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
26052 <li> The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
26053 function recommended in the Appendix to IEC 60559 (but with a minor change to
26054 <!--page 524 -->
26055 better handle signed zeros).
26056 <li> The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
26057 the Appendix to IEC 60559.
26058 <li> The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
26059 Appendix to IEC 60559.
26060 <li> The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
26061 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
26062 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
26063 function recommended in the Appendix to IEC 60559 (except that the classification
26065 </ul>
26070 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
26071 (even for NaN). Otherwise, if the floating value is infinite or NaN or if the integral part
26072 of the floating value exceeds the range of the integer type, then the ''invalid'' floating-
26073 point exception is raised and the resulting value is unspecified. Otherwise, the resulting
26074 value is determined by <a href="#6.3.1.4">6.3.1.4</a>. Conversion of an integral floating value that does not
26075 exceed the range of the integer type raises no floating-point exceptions; whether
26076 conversion of a non-integral floating value raises the ''inexact'' floating-point exception is
26080 <p><small><a name="note347" href="#note347">347)</a> ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
26081 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
26082 cases where it matters, library functions can be used to effect such conversions with or without raising
26083 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
26085 </small>
26090 Conversion from the widest supported IEC 60559 format to decimal with
26091 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note348"><b>348)</b></a></sup>
26093 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
26094 particular, conversion between any supported IEC 60559 format and decimal with
26095 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
26096 rounding mode), which assures that conversion from the widest supported IEC 60559
26097 format to decimal with DECIMAL_DIG digits and back is the identity function.
26101 <!--page 525 -->
26103 Functions such as strtod that convert character sequences to floating types honor the
26104 rounding direction. Hence, if the rounding direction might be upward or downward, the
26105 implementation cannot convert a minus-signed sequence by negating the converted
26106 unsigned sequence.
26109 <p><small><a name="note348" href="#note348">348)</a> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
26113 </small>
26117 If the return expression is evaluated in a floating-point format different from the return
26118 type, the expression is converted as if by assignment<sup><a href="#note349"><b>349)</b></a></sup> to the return type of the function
26119 and the resulting value is returned to the caller.
26122 <p><small><a name="note349" href="#note349">349)</a> Assignment removes any extra range and precision.
26123 </small>
26128 A contracted expression is correctly rounded (once) and treats infinities, NaNs, signed
26129 zeros, subnormals, and the rounding directions in a manner consistent with the basic
26130 arithmetic operations covered by IEC 60559.
26133 A contracted expression should raise floating-point exceptions in a manner generally
26134 consistent with the basic arithmetic operations. *
26139 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
26140 point exception status flags and directed-rounding control modes. It includes also
26141 IEC 60559 dynamic rounding precision and trap enablement modes, if the
26145 <p><small><a name="note350" href="#note350">350)</a> This specification does not require dynamic rounding precision nor trap enablement modes.
26146 </small>
26151 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
26152 status flags, and that rounding control modes can be set explicitly to affect result values of
26153 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
26154 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
26160 <!--page 526 -->
26163 <p><small><a name="note351" href="#note351">351)</a> If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
26164 point control modes will be the default ones and the floating-point status flags will not be tested,
26166 </small>
26171 During translation the IEC 60559 default modes are in effect:
26172 <ul>
26173 <li> The rounding direction mode is rounding to nearest.
26174 <li> The rounding precision mode (if supported) is set so that results are not shortened.
26175 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
26176 </ul>
26179 The implementation should produce a diagnostic message for each translation-time
26180 floating-point exception, other than ''inexact'';<sup><a href="#note352"><b>352)</b></a></sup> the implementation should then
26181 proceed with the translation of the program.
26184 <p><small><a name="note352" href="#note352">352)</a> As floating constants are converted to appropriate internal representations at translation time, their
26185 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
26186 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
26187 strtod, provide execution-time conversion of numeric strings.
26188 </small>
26193 At program startup the floating-point environment is initialized as prescribed by
26194 IEC 60559:
26195 <ul>
26196 <li> All floating-point exception status flags are cleared.
26197 <li> The rounding direction mode is rounding to nearest.
26198 <li> The dynamic rounding precision mode (if supported) is set so that results are not
26199 shortened.
26200 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
26201 </ul>
26206 An arithmetic constant expression of floating type, other than one in an initializer for an
26207 object that has static or thread storage duration, is evaluated (as if) during execution; thus,
26208 it is affected by any operative floating-point control modes and raises floating-point
26209 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
26212 EXAMPLE
26216 <!--page 527 -->
26217 <pre>
26219 #pragma STDC FENV_ACCESS ON
26220 void f(void)
26221 {
26226 /* ... */
26227 }
26228 </pre>
26230 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
26231 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
26232 execution time.
26236 <p><small><a name="note353" href="#note353">353)</a> Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like 1.0/3.0
26239 efficiency of translation-time evaluation through static initialization, such as
26241 <pre>
26243 </pre>
26244 </small>
26249 All computation for automatic initialization is done (as if) at execution time; thus, it is
26250 affected by any operative modes and raises floating-point exceptions as required by
26251 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
26252 for initialization of objects that have static or thread storage duration is done (as if) at
26253 translation time.
26255 EXAMPLE
26256 <pre>
26258 #pragma STDC FENV_ACCESS ON
26259 void f(void)
26260 {
26261 float u[] = { 1.1e75 }; // raises exceptions
26262 static float v = 1.1e75; // does not raise exceptions
26263 float w = 1.1e75; // raises exceptions
26264 double x = 1.1e75; // may raise exceptions
26265 float y = 1.1e75f; // may raise exceptions
26266 long double z = 1.1e75; // does not raise exceptions
26267 /* ... */
26268 }
26269 </pre>
26271 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
26272 done at translation time. The automatic initialization of u and w require an execution-time conversion to
26273 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
26274 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
26275 conversions is not to a narrower format, in which case no floating-point exception is raised.<sup><a href="#note354"><b>354)</b></a></sup> The
26276 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
26277 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
26281 <!--page 528 -->
26282 their internal representations occur at translation time in all cases.
26286 <p><small><a name="note354" href="#note354">354)</a> Use of float_t and double_t variables increases the likelihood of translation-time computation.
26287 For example, the automatic initialization
26289 <pre>
26290 double_t x = 1.1e75;
26291 </pre>
26292 could be done at translation time, regardless of the expression evaluation method.
26293 </small>
26298 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
26299 change floating-point status flags and control modes just as indicated by their
26300 specifications (including conformance to IEC 60559). They do not change flags or modes
26301 (so as to be detectable by the user) in any other cases.
26303 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
26304 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
26305 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
26306 before ''inexact''.
26311 This section identifies code transformations that might subvert IEC 60559-specified
26312 behavior, and others that do not.
26317 Floating-point arithmetic operations and external function calls may entail side effects
26318 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
26319 ''on''. The flags and modes in the floating-point environment may be regarded as global
26320 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
26321 flags.
26323 Concern about side effects may inhibit code motion and removal of seemingly useless
26324 code. For example, in
26325 <pre>
26327 #pragma STDC FENV_ACCESS ON
26328 void f(double x)
26329 {
26330 /* ... */
26332 /* ... */
26333 }
26334 </pre>
26335 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
26337 course these optimizations are valid if the implementation can rule out the nettlesome
26338 cases.)
26340 This specification does not require support for trap handlers that maintain information
26341 about the order or count of floating-point exceptions. Therefore, between function calls,
26342 floating-point exceptions need not be precise: the actual order and number of occurrences
26344 <!--page 529 -->
26345 the preceding loop could be treated as
26346 <pre>
26348 </pre>
26354 <pre>
26355 generally do not yield numerically equivalent expressions, if the
26356 constants are exact then such transformations can be made on
26357 IEC 60559 machines and others that round perfectly.
26358 </pre>
26360 <pre>
26362 </pre>
26364 <pre>
26365 infinite, or NaN.
26366 </pre>
26368 <pre>
26369 IEC 60559 machines, among others).
26370 </pre>
26372 <pre>
26373 is +0 but -(1 - 1) is -0 (in the default rounding direction).<sup><a href="#note356"><b>356)</b></a></sup>
26374 </pre>
26376 <pre>
26377 infinite.
26378 </pre>
26380 <pre>
26381 infinite, or -0.
26382 </pre>
26384 <pre>
26386 </pre>
26388 <pre>
26390 FENV_ACCESS pragma is ''off'', promising default rounding, then
26391 the implementation can replace x - 0 by x, even if x might be zero.
26392 </pre>
26394 <pre>
26396 downward).
26397 </pre>
26399 <!--page 530 -->
26402 <p><small><a name="note355" href="#note355">355)</a> Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
26403 other transformations that remove arithmetic operators.
26404 </small>
26405 <p><small><a name="note356" href="#note356">356)</a> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
26406 Examples include:
26408 <pre>
26410 </pre>
26411 and
26413 <pre>
26414 conj(csqrt(z)) is csqrt(conj(z)),
26415 </pre>
26416 for complex z.
26417 </small>
26422 x != x -> false The expression x != x is true if x is a NaN.
26423 x = x -> true The expression x = x is false if x is a NaN.
26424 x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically equal, these
26425 <pre>
26426 expressions are not equivalent because of side effects when x or y is a
26427 NaN and the state of the FENV_ACCESS pragma is ''on''. This
26428 transformation, which would be desirable if extra code were required
26429 to cause the ''invalid'' floating-point exception for unordered cases,
26430 could be performed provided the state of the FENV_ACCESS pragma
26431 is ''off''.
26432 </pre>
26433 The sense of relational operators shall be maintained. This includes handling unordered
26434 cases as expressed by the source code.
26436 EXAMPLE
26437 <pre>
26438 // calls g and raises ''invalid'' if a and b are unordered
26439 if (a < b)
26440 f();
26441 else
26442 g();
26443 </pre>
26444 is not equivalent to
26445 <pre>
26446 // calls f and raises ''invalid'' if a and b are unordered
26447 if (a >= b)
26448 g();
26449 else
26450 f();
26451 </pre>
26452 nor to
26453 <pre>
26454 // calls f without raising ''invalid'' if a and b are unordered
26455 if (isgreaterequal(a,b))
26456 g();
26457 else
26458 f();
26459 </pre>
26460 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
26461 <pre>
26462 // calls g without raising ''invalid'' if a and b are unordered
26463 if (isless(a,b))
26464 f();
26465 else
26466 g();
26467 </pre>
26468 but is equivalent to
26469 <!--page 531 -->
26470 <pre>
26471 if (!(a < b))
26472 g();
26473 else
26474 f();
26475 </pre>
26481 The implementation shall honor floating-point exceptions raised by execution-time
26482 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.8.4">F.8.4</a>
26483 and <a href="#F.8.5">F.8.5</a>.) An operation on constants that raises no floating-point exception can be
26484 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
26485 further check is required to assure that changing the rounding direction to downward does
26486 not alter the sign of the result,<sup><a href="#note357"><b>357)</b></a></sup> and implementations that support dynamic rounding
26487 precision modes shall assure further that the result of the operation raises no floating-
26488 point exception when converted to the semantic type of the operation.
26491 <p><small><a name="note357" href="#note357">357)</a> 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
26492 </small>
26497 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
26498 for IEC 60559 implementations.
26500 The Standard C macro HUGE_VAL and its float and long double analogs,
26501 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
26502 infinities.
26504 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
26505 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
26506 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
26507 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
26508 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
26510 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
26511 nonzero value.
26513 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
26514 subsequent subclauses of this annex.
26516 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
26517 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
26518 whose magnitude is too large.
26520 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
26524 <!--page 532 -->
26526 Whether or when library functions raise the ''inexact'' floating-point exception is
26527 unspecified, unless explicitly specified otherwise.
26529 Whether or when library functions raise an undeserved ''underflow'' floating-point
26530 exception is unspecified.<sup><a href="#note359"><b>359)</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
26531 not raise spurious floating-point exceptions (detectable by the user), other than the
26532 ''inexact'' floating-point exception.
26534 Whether the functions honor the rounding direction mode is implementation-defined,
26535 unless explicitly specified otherwise.
26537 Functions with a NaN argument return a NaN result and raise no floating-point exception,
26538 except where stated otherwise.
26540 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
26541 For families of functions, the specifications apply to all of the functions even though only
26542 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
26543 occurs in both an argument and the result, the result has the same sign as the argument.
26546 If a function with one or more NaN arguments returns a NaN result, the result should be
26547 the same as one of the NaN arguments (after possible type conversion), except perhaps
26548 for the sign.
26551 <p><small><a name="note358" href="#note358">358)</a> IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
26552 when the floating-point exception is raised.
26553 </small>
26554 <p><small><a name="note359" href="#note359">359)</a> It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
26555 avoiding them would be too costly.
26556 </small>
26564 <ul>
26566 <li> acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
26568 </ul>
26573 <ul>
26575 <li> asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
26581 <!--page 533 -->
26582 </ul>
26587 <ul>
26590 </ul>
26595 <ul>
26607 </ul>
26610 <p><small><a name="note360" href="#note360">360)</a> atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
26611 the ''divide-by-zero'' floating-point exception.
26612 </small>
26617 <ul>
26619 <li> cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
26620 </ul>
26625 <ul>
26627 <li> sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
26628 </ul>
26633 <ul>
26635 <li> tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
26640 <!--page 534 -->
26641 </ul>
26649 <ul>
26652 <li> acosh(+(inf)) returns +(inf).
26653 </ul>
26658 <ul>
26660 <li> asinh((+-)(inf)) returns (+-)(inf).
26661 </ul>
26666 <ul>
26668 <li> atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
26669 <li> atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
26671 </ul>
26676 <ul>
26678 <li> cosh((+-)(inf)) returns +(inf).
26679 </ul>
26684 <ul>
26686 <li> sinh((+-)(inf)) returns (+-)(inf).
26687 </ul>
26692 <ul>
26695 </ul>
26703 <ul>
26706 <li> exp(+(inf)) returns +(inf).
26707 <!--page 535 -->
26708 </ul>
26713 <ul>
26716 <li> exp2(+(inf)) returns +(inf).
26717 </ul>
26722 <ul>
26725 <li> expm1(+(inf)) returns +(inf).
26726 </ul>
26731 <ul>
26733 <li> frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
26734 pointed to by exp.
26735 <li> frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
26736 (and returns a NaN).
26737 </ul>
26739 frexp raises no floating-point exceptions.
26741 When the radix of the argument is a power of 2, the returned value is exact and is
26742 independent of the current rounding direction mode.
26744 On a binary system, the body of the frexp function might be
26745 <pre>
26746 {
26748 return scalbn(value, -(*exp));
26749 }
26750 </pre>
26755 When the correct result is representable in the range of the return type, the returned value
26756 is exact and is independent of the current rounding direction mode.
26758 If the correct result is outside the range of the return type, the numeric result is
26759 unspecified and the ''invalid'' floating-point exception is raised.
26760 <!--page 536 -->
26765 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
26770 <ul>
26774 <li> log(+(inf)) returns +(inf).
26775 </ul>
26780 <ul>
26784 <li> log10(+(inf)) returns +(inf).
26785 </ul>
26790 <ul>
26793 <li> log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
26795 <li> log1p(+(inf)) returns +(inf).
26796 </ul>
26801 <ul>
26805 <li> log2(+(inf)) returns +(inf).
26806 </ul>
26811 <ul>
26813 <li> logb((+-)(inf)) returns +(inf).
26814 </ul>
26816 The returned value is exact and is independent of the current rounding direction mode.
26817 <!--page 537 -->
26822 <ul>
26823 <li> modf((+-)x, iptr) returns a result with the same sign as x.
26824 <li> modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
26825 <li> modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
26826 NaN).
26827 </ul>
26829 The returned values are exact and are independent of the current rounding direction
26830 mode.
26832 modf behaves as though implemented by
26833 <pre>
26836 #pragma STDC FENV_ACCESS ON
26837 double modf(double value, double *iptr)
26838 {
26839 int save_round = fegetround();
26840 fesetround(FE_TOWARDZERO);
26841 *iptr = nearbyint(value);
26842 fesetround(save_round);
26843 return copysign(
26844 isinf(value) ? 0.0 :
26845 value - (*iptr), value);
26846 }
26847 </pre>
26852 <ul>
26855 <li> scalbn((+-)(inf), n) returns (+-)(inf).
26856 </ul>
26858 If the calculation does not overflow or underflow, the returned value is exact and
26859 independent of the current rounding direction mode.
26860 <!--page 538 -->
26868 <ul>
26870 <li> cbrt((+-)(inf)) returns (+-)(inf).
26871 </ul>
26876 <ul>
26878 <li> fabs((+-)(inf)) returns +(inf).
26879 </ul>
26881 The returned value is exact and is independent of the current rounding direction mode.
26886 <ul>
26887 <li> hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
26889 <li> hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
26890 </ul>
26895 <ul>
26896 <li> pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
26901 exception.
26907 <li> pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
26913 <!--page 539 -->
26920 </ul>
26925 sqrt is fully specified as a basic arithmetic operation in IEC 60559. The returned value
26926 is dependent on the current rounding direction mode.
26934 <ul>
26937 </ul>
26942 <ul>
26945 </ul>
26950 <ul>
26953 <li> lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
26954 x a negative integer or zero.
26955 <li> lgamma(-(inf)) returns +(inf).
26956 <li> lgamma(+(inf)) returns +(inf).
26957 </ul>
26962 <ul>
26963 <li> tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
26964 <li> tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
26965 negative integer.
26966 <li> tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
26967 <li> tgamma(+(inf)) returns +(inf).
26968 <!--page 540 -->
26969 </ul>
26977 <ul>
26979 <li> ceil((+-)(inf)) returns (+-)(inf).
26980 </ul>
26982 The returned value is independent of the current rounding direction mode.
26984 The double version of ceil behaves as though implemented by
26985 <pre>
26988 #pragma STDC FENV_ACCESS ON
26989 double ceil(double x)
26990 {
26991 double result;
26992 int save_round = fegetround();
26993 fesetround(FE_UPWARD);
26994 result = rint(x); // or nearbyint instead of rint
26995 fesetround(save_round);
26996 return result;
26997 }
26998 </pre>
27000 The ceil functions may, but are not required to, raise the ''inexact'' floating-point
27001 exception for finite non-integer arguments, as this implementation does.
27006 <ul>
27008 <li> floor((+-)(inf)) returns (+-)(inf).
27009 </ul>
27011 The returned value and is independent of the current rounding direction mode.
27013 See the sample implementation for ceil in <a href="#F.10.6.1">F.10.6.1</a>. The floor functions may, but are
27014 not required to, raise the ''inexact'' floating-point exception for finite non-integer
27015 arguments, as that implementation does.
27020 The nearbyint functions use IEC 60559 rounding according to the current rounding
27021 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
27022 value from the argument.
27023 <ul>
27025 <li> nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
27026 <!--page 541 -->
27027 </ul>
27032 The rint functions differ from the nearbyint functions only in that they do raise the
27033 ''inexact'' floating-point exception if the result differs in value from the argument.
27038 The lrint and llrint functions provide floating-to-integer conversion as prescribed
27039 by IEC 60559. They round according to the current rounding direction. If the rounded
27040 value is outside the range of the return type, the numeric result is unspecified and the
27041 ''invalid'' floating-point exception is raised. When they raise no other floating-point
27042 exception and the result differs from the argument, they raise the ''inexact'' floating-point
27043 exception.
27048 <ul>
27050 <li> round((+-)(inf)) returns (+-)(inf).
27051 </ul>
27053 The returned value is independent of the current rounding direction mode.
27055 The double version of round behaves as though implemented by
27056 <pre>
27059 #pragma STDC FENV_ACCESS ON
27060 double round(double x)
27061 {
27062 double result;
27063 fenv_t save_env;
27064 feholdexcept(&save_env);
27065 result = rint(x);
27066 if (fetestexcept(FE_INEXACT)) {
27067 fesetround(FE_TOWARDZERO);
27068 result = rint(copysign(0.5 + fabs(x), x));
27069 }
27070 feupdateenv(&save_env);
27071 return result;
27072 }
27073 </pre>
27074 The round functions may, but are not required to, raise the ''inexact'' floating-point
27075 exception for finite non-integer numeric arguments, as this implementation does.
27076 <!--page 542 -->
27081 The lround and llround functions differ from the lrint and llrint functions
27082 with the default rounding direction just in that the lround and llround functions
27083 round halfway cases away from zero and need not raise the ''inexact'' floating-point
27084 exception for non-integer arguments that round to within the range of the return type.
27089 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
27090 rounding direction). The returned value is exact.
27091 <ul>
27093 <li> trunc((+-)(inf)) returns (+-)(inf).
27094 </ul>
27096 The returned value is independent of the current rounding direction mode. The trunc
27097 functions may, but are not required to, raise the ''inexact'' floating-point exception for
27098 finite non-integer arguments.
27106 <ul>
27108 <li> fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
27109 infinite or y zero (and neither is a NaN).
27110 <li> fmod(x, (+-)(inf)) returns x for x not infinite.
27111 </ul>
27113 When subnormal results are supported, the returned value is exact and is independent of
27114 the current rounding direction mode.
27116 The double version of fmod behaves as though implemented by
27117 <!--page 543 -->
27118 <pre>
27121 #pragma STDC FENV_ACCESS ON
27122 double fmod(double x, double y)
27123 {
27124 double result;
27125 result = remainder(fabs(x), (y = fabs(y)));
27126 if (signbit(result)) result += y;
27127 return copysign(result, x);
27128 }
27129 </pre>
27134 The remainder functions are fully specified as a basic arithmetic operation in
27135 IEC 60559.
27137 When subnormal results are supported, the returned value is exact and is independent of
27138 the current rounding direction mode.
27143 The remquo functions follow the specifications for the remainder functions. They
27144 have no further specifications special to IEC 60559 implementations.
27146 When subnormal results are supported, the returned value is exact and is independent of
27147 the current rounding direction mode.
27155 copysign is specified in the Appendix to IEC 60559.
27157 The returned value is exact and is independent of the current rounding direction mode.
27162 All IEC 60559 implementations support quiet NaNs, in all floating formats.
27164 The returned value is exact and is independent of the current rounding direction mode.
27169 <ul>
27170 <li> nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
27171 for x finite and the function value infinite.
27172 <li> nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
27173 exceptions for the function value subnormal or zero and x != y.
27174 </ul>
27176 Even though underflow or overflow can occur, the returned value is independent of the
27177 current rounding direction mode.
27182 No additional requirements beyond those on nextafter.
27184 Even though underflow or overflow can occur, the returned value is independent of the
27185 current rounding direction mode.
27186 <!--page 544 -->
27189 <h4><a name="F.10.9" href="#F.10.9">F.10.9 Maximum, minimum, and positive difference functions</a></h4>
27194 No additional requirements.
27199 If just one argument is a NaN, the fmax functions return the other argument (if both
27200 arguments are NaNs, the functions return a NaN).
27202 The returned value is exact and is independent of the current rounding direction mode.
27205 <pre>
27206 { return (isgreaterequal(x, y) ||
27207 isnan(y)) ? x : y; }
27208 </pre>
27211 <p><small><a name="note361" href="#note361">361)</a> Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
27212 return +0; however, implementation in software might be impractical.
27213 </small>
27218 The fmin functions are analogous to the fmax functions (see <a href="#F.10.9.2">F.10.9.2</a>).
27220 The returned value is exact and is independent of the current rounding direction mode.
27228 <ul>
27229 <li> fma(x, y, z) computes xy + z, correctly rounded once.
27230 <li> fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
27231 exception if one of x and y is infinite, the other is zero, and z is a NaN.
27232 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
27233 one of x and y is infinite, the other is zero, and z is not a NaN.
27234 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
27235 times y is an exact infinity and z is also an infinity but with the opposite sign.
27240 <!--page 545 -->
27241 </ul>
27246 Relational operators and their corresponding comparison macros (<a href="#7.12.14">7.12.14</a>) produce
27247 equivalent result values, even if argument values are represented in wider formats. Thus,
27248 comparison macro arguments represented in formats wider than their semantic types are
27249 not converted to the semantic types, unless the wide evaluation method converts operands
27250 of relational operators to their semantic types. The standard wide evaluation methods
27251 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
27252 operands of relational operators to their semantic types.
27253 <!--page 546 -->
27257 <pre>
27258 (normative)
27259 IEC 60559-compatible complex arithmetic
27260 </pre>
27265 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
27266 IEC 60559 real floating-point arithmetic. An implementation that defines *
27267 __STDC_IEC_559_COMPLEX__ shall conform to the specifications in this annex.<sup><a href="#note362"><b>362)</b></a></sup>
27270 <p><small><a name="note362" href="#note362">362)</a> Implementations that do not define __STDC_IEC_559_COMPLEX__ are not required to conform
27271 to these specifications.
27272 </small>
27277 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
27278 used as a type specifier within declaration specifiers in the same way as _Complex is
27279 (thus, _Imaginary float is a valid type name).
27281 There are three imaginary types, designated as float _Imaginary, double
27282 _Imaginary, and long double _Imaginary. The imaginary types (along with
27283 the real floating and complex types) are floating types.
27285 For imaginary types, the corresponding real type is given by deleting the keyword
27286 _Imaginary from the type name.
27288 Each imaginary type has the same representation and alignment requirements as the
27289 corresponding real type. The value of an object of imaginary type is the value of the real
27290 representation times the imaginary unit.
27292 The imaginary type domain comprises the imaginary types.
27297 A complex or imaginary value with at least one infinite part is regarded as an infinity
27298 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
27299 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
27300 a zero if each of its parts is a zero.
27305 <!--page 547 -->
27313 Conversions among imaginary types follow rules analogous to those for real floating
27314 types.
27319 When a value of imaginary type is converted to a real type other than _Bool,<sup><a href="#note363"><b>363)</b></a></sup> the
27320 result is a positive zero.
27322 When a value of real type is converted to an imaginary type, the result is a positive
27323 imaginary zero.
27327 </small>
27332 When a value of imaginary type is converted to a complex type, the real part of the
27333 complex result value is a positive zero and the imaginary part of the complex result value
27334 is determined by the conversion rules for the corresponding real types.
27336 When a value of complex type is converted to an imaginary type, the real part of the
27337 complex value is discarded and the value of the imaginary part is converted according to
27338 the conversion rules for the corresponding real types.
27343 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
27344 operation with an imaginary operand.
27346 For most operand types, the value of the result of a binary operator with an imaginary or
27347 complex operand is completely determined, with reference to real arithmetic, by the usual
27348 mathematical formula. For some operand types, the usual mathematical formula is
27349 problematic because of its treatment of infinities and because of undue overflow or
27350 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
27351 not completely determined.
27356 <!--page 548 -->
27362 If one operand has real type and the other operand has imaginary type, then the result has
27363 imaginary type. If both operands have imaginary type, then the result has real type. (If
27364 either operand has complex type, then the result has complex type.)
27366 If the operands are not both complex, then the result and floating-point exception
27367 behavior of the * operator is defined by the usual mathematical formula:
27368 <pre>
27369 * u iv u + iv
27370 </pre>
27372 <pre>
27373 x xu i(xv) (xu) + i(xv)
27374 </pre>
27376 <pre>
27377 iy i(yu) -yv (-yv) + i(yu)
27378 </pre>
27380 <pre>
27381 x + iy (xu) + i(yu) (-yv) + i(xv)
27382 </pre>
27384 If the second operand is not complex, then the result and floating-point exception
27385 behavior of the / operator is defined by the usual mathematical formula:
27386 <pre>
27387 / u iv
27388 </pre>
27390 <pre>
27391 x x/u i(-x/v)
27392 </pre>
27394 <pre>
27395 iy i(y/u) y/v
27396 </pre>
27398 <pre>
27399 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)
27400 </pre>
27402 The * and / operators satisfy the following infinity properties for all real, imaginary, and
27404 <ul>
27405 <li> if one operand is an infinity and the other operand is a nonzero finite number or an
27406 infinity, then the result of the * operator is an infinity;
27407 <li> if the first operand is an infinity and the second operand is a finite number, then the
27408 result of the / operator is an infinity;
27409 <li> if the first operand is a finite number and the second operand is an infinity, then the
27410 result of the / operator is a zero;
27415 <!--page 549 -->
27416 <li> if the first operand is a nonzero finite number or an infinity and the second operand is
27417 a zero, then the result of the / operator is an infinity.
27418 </ul>
27420 If both operands of the * operator are complex or if the second operand of the / operator
27421 is complex, the operator raises floating-point exceptions if appropriate for the calculation
27422 of the parts of the result, and may raise spurious floating-point exceptions.
27424 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
27426 <!--page 550 -->
27427 <pre>
27430 /* Multiply z * w ... */
27431 double complex _Cmultd(double complex z, double complex w)
27432 {
27433 #pragma STDC FP_CONTRACT OFF
27434 double a, b, c, d, ac, bd, ad, bc, x, y;
27435 a = creal(z); b = cimag(z);
27436 c = creal(w); d = cimag(w);
27437 ac = a * c; bd = b * d;
27438 ad = a * d; bc = b * c;
27439 x = ac - bd; y = ad + bc;
27440 if (isnan(x) && isnan(y)) {
27441 /* Recover infinities that computed as NaN+iNaN ... */
27442 int recalc = 0;
27443 if ( isinf(a) || isinf(b) ) { // z is infinite
27447 if (isnan(c)) c = copysign(0.0, c);
27448 if (isnan(d)) d = copysign(0.0, d);
27449 recalc = 1;
27450 }
27451 if ( isinf(c) || isinf(d) ) { // w is infinite
27455 if (isnan(a)) a = copysign(0.0, a);
27456 if (isnan(b)) b = copysign(0.0, b);
27457 recalc = 1;
27458 }
27459 if (!recalc && (isinf(ac) || isinf(bd) ||
27460 isinf(ad) || isinf(bc))) {
27461 /* Recover infinities from overflow by changing NaNs to 0 ... */
27462 if (isnan(a)) a = copysign(0.0, a);
27463 if (isnan(b)) b = copysign(0.0, b);
27464 if (isnan(c)) c = copysign(0.0, c);
27465 if (isnan(d)) d = copysign(0.0, d);
27466 recalc = 1;
27467 }
27468 if (recalc) {
27469 x = INFINITY * ( a * c - b * d );
27470 y = INFINITY * ( a * d + b * c );
27471 }
27472 }
27473 return x + I * y;
27474 }
27475 </pre>
27477 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
27478 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
27481 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
27482 <!--page 551 -->
27483 <pre>
27486 /* Divide z / w ... */
27487 double complex _Cdivd(double complex z, double complex w)
27488 {
27489 #pragma STDC FP_CONTRACT OFF
27490 double a, b, c, d, logbw, denom, x, y;
27491 int ilogbw = 0;
27492 a = creal(z); b = cimag(z);
27493 c = creal(w); d = cimag(w);
27494 logbw = logb(fmax(fabs(c), fabs(d)));
27495 if (logbw == INFINITY) {
27496 ilogbw = (int)logbw;
27497 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
27498 }
27499 denom = c * c + d * d;
27500 x = scalbn((a * c + b * d) / denom, -ilogbw);
27501 y = scalbn((b * c - a * d) / denom, -ilogbw);
27502 /* Recover infinities and zeros that computed as NaN+iNaN; */
27503 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
27504 if (isnan(x) && isnan(y)) {
27506 (!isnan(a) || !isnan(b))) {
27507 x = copysign(INFINITY, c) * a;
27508 y = copysign(INFINITY, c) * b;
27509 }
27510 else if ((isinf(a) || isinf(b)) &&
27511 isfinite(c) && isfinite(d)) {
27514 x = INFINITY * ( a * c + b * d );
27515 y = INFINITY * ( b * c - a * d );
27516 }
27517 else if (isinf(logbw) &&
27518 isfinite(a) && isfinite(b)) {
27521 x = 0.0 * ( a * c + b * d );
27522 y = 0.0 * ( b * c - a * d );
27523 }
27524 }
27525 return x + I * y;
27526 }
27527 </pre>
27529 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
27530 for multiplication. In the spirit of the multiplication example above, this code does not defend against
27531 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
27532 with division, provides better roundoff characteristics.
27536 <p><small><a name="note364" href="#note364">364)</a> These properties are already implied for those cases covered in the tables, but are required for all cases
27537 (at least where the state for CX_LIMITED_RANGE is ''off'').
27538 </small>
27544 If both operands have imaginary type, then the result has imaginary type. (If one operand
27545 has real type and the other operand has imaginary type, or if either operand has complex
27546 type, then the result has complex type.)
27548 In all cases the result and floating-point exception behavior of a + or - operator is defined
27549 by the usual mathematical formula:
27550 <pre>
27551 + or - u iv u + iv
27552 </pre>
27554 <pre>
27555 x x(+-)u x (+-) iv (x (+-) u) (+-) iv
27556 </pre>
27558 <pre>
27559 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)
27560 </pre>
27562 <pre>
27563 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)
27564 </pre>
27569 The macros
27570 <pre>
27571 imaginary
27572 </pre>
27573 and
27574 <pre>
27575 _Imaginary_I
27576 </pre>
27577 are defined, respectively, as _Imaginary and a constant expression of type const
27578 float _Imaginary with the value of the imaginary unit. The macro
27579 <pre>
27580 I
27581 </pre>
27582 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
27583 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
27584 imaginary.
27586 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
27587 particularly suited to IEC 60559 implementations. For families of functions, the
27588 specifications apply to all of the functions even though only the principal function is
27589 <!--page 552 -->
27590 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
27591 and the result, the result has the same sign as the argument.
27593 The functions are continuous onto both sides of their branch cuts, taking into account the
27596 Since complex and imaginary values are composed of real values, each function may be
27597 regarded as computing real values from real values. Except as noted, the functions treat
27598 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
27599 manner consistent with the specifications for real functions in F.10.<sup><a href="#note365"><b>365)</b></a></sup>
27601 The functions cimag, conj, cproj, and creal are fully specified for all
27602 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
27603 point exceptions.
27605 Each of the functions cabs and carg is specified by a formula in terms of a real
27607 <pre>
27608 cabs(x + iy) = hypot(x, y)
27609 carg(x + iy) = atan2(y, x)
27610 </pre>
27612 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
27613 a formula in terms of other complex functions (whose special cases are specified below):
27614 <pre>
27615 casin(z) = -i casinh(iz)
27616 catan(z) = -i catanh(iz)
27617 ccos(z) = ccosh(iz)
27618 csin(z) = -i csinh(iz)
27619 ctan(z) = -i ctanh(iz)
27620 </pre>
27622 For the other functions, the following subclauses specify behavior for special cases,
27623 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
27624 families of functions, the specifications apply to all of the functions even though only the
27625 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
27626 specifications for the upper half-plane imply the specifications for the lower half-plane; if
27627 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
27628 specifications for the first quadrant imply the specifications for the other three quadrants.
27630 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
27635 <!--page 553 -->
27638 <p><small><a name="note365" href="#note365">365)</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
27639 other part is a NaN.
27640 </small>
27648 <ul>
27649 <li> cacos(conj(z)) = conj(cacos(z)).
27653 <li> cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27654 point exception, for nonzero finite x.
27655 <li> cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
27659 <li> cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
27660 result is unspecified).
27661 <li> cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27662 point exception, for finite y.
27663 <li> cacos(NaN + i (inf)) returns NaN - i (inf).
27664 <li> cacos(NaN + iNaN) returns NaN + iNaN.
27665 </ul>
27673 <ul>
27674 <li> cacosh(conj(z)) = conj(cacosh(z)).
27677 <li> cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
27678 floating-point exception, for finite x.
27679 <li> cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
27680 <li> cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
27683 <li> cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
27684 <!--page 554 -->
27685 <li> cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
27686 floating-point exception, for finite y.
27687 <li> cacosh(NaN + i (inf)) returns +(inf) + iNaN.
27688 <li> cacosh(NaN + iNaN) returns NaN + iNaN.
27689 </ul>
27694 <ul>
27695 <li> casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
27698 <li> casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
27699 floating-point exception, for finite x.
27700 <li> casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
27702 <li> casinh(+(inf) + iNaN) returns +(inf) + iNaN.
27703 <li> casinh(NaN + i0) returns NaN + i0.
27704 <li> casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
27705 floating-point exception, for finite nonzero y.
27706 <li> casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
27707 is unspecified).
27708 <li> casinh(NaN + iNaN) returns NaN + iNaN.
27709 </ul>
27714 <ul>
27715 <li> catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
27719 exception.
27721 <li> catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
27722 floating-point exception, for nonzero finite x.
27726 <!--page 555 -->
27727 <li> catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
27728 floating-point exception, for finite y.
27729 <li> catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
27730 unspecified).
27731 <li> catanh(NaN + iNaN) returns NaN + iNaN.
27732 </ul>
27737 <ul>
27738 <li> ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
27741 result is unspecified) and raises the ''invalid'' floating-point exception.
27743 result is unspecified).
27744 <li> ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
27745 exception, for finite nonzero x.
27746 <li> ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27747 point exception, for finite nonzero x.
27748 <li> ccosh(+(inf) + i0) returns +(inf) + i0.
27749 <li> ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
27750 <li> ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
27751 unspecified) and raises the ''invalid'' floating-point exception.
27752 <li> ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
27753 <li> ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
27754 result is unspecified).
27755 <li> ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27756 point exception, for all nonzero numbers y.
27757 <li> ccosh(NaN + iNaN) returns NaN + iNaN.
27758 </ul>
27763 <ul>
27764 <li> csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
27766 <li> csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
27767 unspecified) and raises the ''invalid'' floating-point exception.
27769 unspecified).
27770 <!--page 556 -->
27771 <li> csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
27772 exception, for positive finite x.
27773 <li> csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27774 point exception, for finite nonzero x.
27775 <li> csinh(+(inf) + i0) returns +(inf) + i0.
27776 <li> csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
27777 <li> csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
27778 unspecified) and raises the ''invalid'' floating-point exception.
27779 <li> csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
27780 is unspecified).
27781 <li> csinh(NaN + i0) returns NaN + i0.
27782 <li> csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27783 point exception, for all nonzero numbers y.
27784 <li> csinh(NaN + iNaN) returns NaN + iNaN.
27785 </ul>
27790 <ul>
27791 <li> ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
27793 <li> ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
27794 exception, for finite x.
27795 <li> ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27796 point exception, for finite x.
27798 <li> ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
27799 is unspecified).
27801 result is unspecified).
27802 <li> ctanh(NaN + i0) returns NaN + i0.
27803 <li> ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27804 point exception, for all nonzero numbers y.
27805 <li> ctanh(NaN + iNaN) returns NaN + iNaN.
27806 <!--page 557 -->
27807 </ul>
27815 <ul>
27816 <li> cexp(conj(z)) = conj(cexp(z)).
27818 <li> cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
27819 exception, for finite x.
27820 <li> cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27821 point exception, for finite x.
27822 <li> cexp(+(inf) + i0) returns +(inf) + i0.
27824 <li> cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
27825 <li> cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
27826 the result are unspecified).
27827 <li> cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
27828 exception (where the sign of the real part of the result is unspecified).
27829 <li> cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
27830 of the result are unspecified).
27831 <li> cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
27832 is unspecified).
27833 <li> cexp(NaN + i0) returns NaN + i0.
27834 <li> cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27835 point exception, for all nonzero numbers y.
27836 <li> cexp(NaN + iNaN) returns NaN + iNaN.
27837 </ul>
27842 <ul>
27843 <li> clog(conj(z)) = conj(clog(z)).
27845 exception.
27847 exception.
27849 <li> clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27850 point exception, for finite x.
27851 <!--page 558 -->
27852 <li> clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
27853 <li> clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
27856 <li> clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
27857 <li> clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27858 point exception, for finite y.
27859 <li> clog(NaN + i (inf)) returns +(inf) + iNaN.
27860 <li> clog(NaN + iNaN) returns NaN + iNaN.
27861 </ul>
27869 The cpow functions raise floating-point exceptions if appropriate for the calculation of
27870 the parts of the result, and may also raise spurious floating-point exceptions.<sup><a href="#note366"><b>366)</b></a></sup>
27873 <p><small><a name="note366" href="#note366">366)</a> This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
27874 implementations that treat special cases more carefully.
27875 </small>
27880 <ul>
27881 <li> csqrt(conj(z)) = conj(csqrt(z)).
27883 <li> csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
27884 <li> csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27885 point exception, for finite x.
27887 <li> csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
27888 <li> csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
27889 result is unspecified).
27890 <li> csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
27891 <li> csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27892 point exception, for finite y.
27893 <li> csqrt(NaN + iNaN) returns NaN + iNaN.
27898 <!--page 559 -->
27899 </ul>
27904 Type-generic macros that accept complex arguments also accept imaginary arguments. If
27905 an argument is imaginary, the macro expands to an expression whose type is real,
27906 imaginary, or complex, as appropriate for the particular function: if the argument is
27907 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
27908 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
27909 the types of the others are complex.
27911 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
27912 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
27913 functions:
27914 <!--page 560 -->
27915 <pre>
27916 cos(iy) = cosh(y)
27917 sin(iy) = i sinh(y)
27918 tan(iy) = i tanh(y)
27919 cosh(iy) = cos(y)
27920 sinh(iy) = i sin(y)
27921 tanh(iy) = i tan(y)
27922 asin(iy) = i asinh(y)
27923 atan(iy) = i atanh(y)
27924 asinh(iy) = i asin(y)
27925 atanh(iy) = i atan(y)
27926 </pre>
27930 <pre>
27931 (informative)
27932 Language independent arithmetic
27933 </pre>
27940 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
27945 The relevant C arithmetic types meet the requirements of LIA-1 types if an
27946 implementation adds notification of exceptional arithmetic operations and meets the 1
27947 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
27952 The LIA-1 data type Boolean is implemented by the C data type bool with values of
27958 The signed C integer types int, long int, long long int, and the corresponding
27959 unsigned types are compatible with LIA-1. If an implementation adds support for the
27960 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
27962 in that overflows or out-of-bounds results silently wrap. An implementation that defines
27963 signed integer types as also being modulo need not detect integer overflow, in which case,
27964 only integer divide-by-zero need be detected.
27966 The parameters for the integer data types can be accessed by the following:
27967 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
27968 <pre>
27969 ULLONG_MAX
27970 </pre>
27971 minint INT_MIN, LONG_MIN, LLONG_MIN
27973 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
27974 is always 0 for the unsigned types, and is not provided for those types.
27975 <!--page 561 -->
27980 The integer operations on integer types are the following:
27981 addI x + y
27982 subI x - y
27983 mulI x * y
27984 divI, divtI x / y
27985 remI, remtI x % y
27986 negI -x
27987 absI abs(x), labs(x), llabs(x)
27988 eqI x == y
27989 neqI x != y
27990 lssI x < y
27991 leqI x <= y
27992 gtrI x > y
27993 geqI x >= y
27994 where x and y are expressions of the same integer type.
27999 The C floating-point types float, double, and long double are compatible with
28001 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
28002 with LIA-1. An implementation that uses IEC 60559 floating-point formats and
28003 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
28004 conformant types.
28008 <p><!--para 1 -->
28009 The parameters for a floating point data type can be accessed by the following:
28010 r FLT_RADIX
28011 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
28012 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
28013 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
28014 <p><!--para 2 -->
28015 The derived constants for the floating point types are accessed by the following:
28016 <!--page 562 -->
28017 fmax FLT_MAX, DBL_MAX, LDBL_MAX
28018 fminN FLT_MIN, DBL_MIN, LDBL_MIN
28019 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
28020 rnd_style FLT_ROUNDS
28024 <p><!--para 1 -->
28025 The floating-point operations on floating-point types are the following:
28026 addF x + y
28027 subF x - y
28028 mulF x * y
28029 divF x / y
28030 negF -x
28031 absF fabsf(x), fabs(x), fabsl(x)
28032 exponentF 1.f+logbf(x), 1.0+logb(x), 1.L+logbl(x)
28033 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
28034 <pre>
28035 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)
28036 </pre>
28037 intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
28038 fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
28039 eqF x == y
28040 neqF x != y
28041 lssF x < y
28042 leqF x <= y
28043 gtrF x > y
28044 geqF x >= y
28045 where x and y are expressions of the same floating point type, n is of type int, and li
28046 is of type long int.
28050 <p><!--para 1 -->
28051 The C Standard requires all floating types to use the same radix and rounding style, so
28052 that only one identifier for each is provided to map to LIA-1.
28053 <p><!--para 2 -->
28054 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
28055 truncate FLT_ROUNDS == 0
28056 <!--page 563 -->
28057 nearest FLT_ROUNDS == 1
28058 other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
28059 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
28060 in all relevant LIA-1 operations, not just addition as in C.
28064 <p><!--para 1 -->
28065 The LIA-1 type conversions are the following type casts:
28066 cvtI' -> I (int)i, (long int)i, (long long int)i,
28067 <pre>
28068 (unsigned int)i, (unsigned long int)i,
28069 (unsigned long long int)i
28070 </pre>
28071 cvtF -> I (int)x, (long int)x, (long long int)x,
28072 <pre>
28073 (unsigned int)x, (unsigned long int)x,
28074 (unsigned long long int)x
28075 </pre>
28076 cvtI -> F (float)i, (double)i, (long double)i
28077 cvtF' -> F (float)x, (double)x, (long double)x
28078 <p><!--para 2 -->
28079 In the above conversions from floating to integer, the use of (cast)x can be replaced with
28080 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
28081 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
28082 conversion functions, lrint(), llrint(), lround(), and llround(), can be
28083 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
28084 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
28085 <p><!--para 3 -->
28086 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
28087 fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
28088 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
28089 to 65535.0 which can then be cast to unsigned short int. But, the
28090 remainder() function is not useful for doing silent wrapping to signed integer types,
28091 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
28092 range -32767.0 to +32768.0 which is not, in general, in the range of signed short
28093 int.
28094 <p><!--para 4 -->
28095 C's conversions (casts) from floating-point to floating-point can meet LIA-1
28096 requirements if an implementation uses round-to-nearest (IEC 60559 default).
28097 <p><!--para 5 -->
28098 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
28099 implementation uses round-to-nearest.
28100 <!--page 564 -->
28104 <p><!--para 1 -->
28105 Notification is the process by which a user or program is informed that an exceptional
28106 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
28107 allows an implementation to cause a notification to occur when any arithmetic operation
28108 returns an exceptional value as defined in LIA-1 clause 5.
28112 <p><!--para 1 -->
28113 LIA-1 requires at least the following two alternatives for handling of notifications:
28114 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
28115 resume.
28116 <p><!--para 2 -->
28117 An implementation need only support a given notification alternative for the entire
28118 program. An implementation may support the ability to switch between notification
28119 alternatives during execution, but is not required to do so. An implementation can
28120 provide separate selection for each kind of notification, but this is not required.
28121 <p><!--para 3 -->
28122 C allows an implementation to provide notification. C's SIGFPE (for traps) and
28123 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
28124 can provide LIA-1 notification.
28125 <p><!--para 4 -->
28126 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
28127 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
28128 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
28129 and-resume behavior with the same constraint.
28133 <p><!--para 1 -->
28135 <p><!--para 2 -->
28136 The following mapping is for floating-point types:
28137 undefined FE_INVALID, FE_DIVBYZERO
28138 floating_overflow FE_OVERFLOW
28139 underflow FE_UNDERFLOW
28140 <p><!--para 3 -->
28141 The floating-point indicator interrogation and manipulation operations are:
28142 set_indicators feraiseexcept(i)
28143 clear_indicators feclearexcept(i)
28144 test_indicators fetestexcept(i)
28145 current_indicators fetestexcept(FE_ALL_EXCEPT)
28146 where i is an expression of type int representing a subset of the LIA-1 indicators.
28147 <p><!--para 4 -->
28148 C allows an implementation to provide the following LIA-1 required behavior: at
28149 program termination if any indicator is set the implementation shall send an unambiguous
28150 <!--page 565 -->
28152 <p><!--para 5 -->
28153 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
28154 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
28155 point indicators.
28159 <p><!--para 1 -->
28160 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
28161 math library functions (which are not permitted to invoke a user's signal handler for
28162 SIGFPE). An implementation can provide an alternative of notification through
28163 termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
28164 <p><!--para 2 -->
28165 LIA-1 does not require that traps be precise.
28166 <p><!--para 3 -->
28167 C does require that SIGFPE be the signal corresponding to LIA-1 arithmetic exceptions,
28168 if there is any signal raised for them.
28169 <p><!--para 4 -->
28170 C supports signal handlers for SIGFPE and allows trapping of LIA-1 arithmetic
28171 exceptions. When LIA-1 arithmetic exceptions do trap, C's signal-handler mechanism
28172 allows trap-and-terminate (either default implementation behavior or user replacement for
28173 it) or trap-and-resume, at the programmer's option.
28174 <!--page 566 -->
28178 <pre>
28179 (informative)
28180 Common warnings
28181 </pre>
28182 <p><!--para 1 -->
28183 An implementation may generate warnings in many situations, none of which are
28184 specified as part of this International Standard. The following are a few of the more
28185 common situations.
28186 <p><!--para 2 -->
28187 <ul>
28188 <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>).
28189 <li> A block with initialization of an object that has automatic storage duration is jumped
28191 <li> An implicit narrowing conversion is encountered, such as the assignment of a long
28192 int or a double to an int, or a pointer to void to a pointer to any type other than
28194 <li> A hexadecimal floating constant cannot be represented exactly in its evaluation format
28196 <li> An integer character constant includes more than one character or a wide character
28199 <li> An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
28200 lvalue in one operand, and a side effect to, or an access to the value of, the identical
28202 <li> A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
28203 <li> The arguments in a function call do not agree in number and type with those of the
28206 <li> A value is given to an object of an enumerated type other than by assignment of an
28207 enumeration constant that is a member of that type, or an enumeration object that has
28208 the same type, or the value of a function that returns the same enumerated type
28213 <li> A constant expression is used as the controlling expression of a selection statement
28215 <!--page 567 -->
28216 <li> An incorrectly formed preprocessing group is encountered while skipping a
28219 <!--page 568 -->
28220 </ul>
28224 <pre>
28225 (informative)
28226 Portability issues
28227 </pre>
28228 <p><!--para 1 -->
28229 This annex collects some information about portability that appears in this International
28230 Standard.
28234 <p><!--para 1 -->
28235 The following are unspecified:
28236 <ul>
28238 <li> The termination status returned to the hosted environment if the return type of main
28240 <li> The behavior of the display device if a printing character is written when the active
28242 <li> The behavior of the display device if a backspace character is written when the active
28244 <li> The behavior of the display device if a horizontal tab character is written when the
28245 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
28246 <li> The behavior of the display device if a vertical tab character is written when the active
28247 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
28248 <li> How an extended source character that does not correspond to a universal character
28249 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
28251 <li> The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
28252 <li> The values of bytes that correspond to union members other than the one last stored
28254 <li> The representation used when storing a value in an object that has more than one
28256 <li> The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
28257 <li> Whether certain operators can generate negative zeros and whether a negative zero
28260 <li> The order in which subexpressions are evaluated and the order in which side effects
28261 take place, except as specified for the function-call (), &&, ||, ? :, and comma
28262 <!--page 569 -->
28264 <li> The order in which the function designator, arguments, and subexpressions within the
28266 <li> The order of side effects among compound literal initialization list expressions
28268 <li> The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
28269 <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>).
28270 <li> Whether a call to an inline function uses the inline definition or the external definition
28272 <li> Whether or not a size expression is evaluated when it is part of the operand of a
28273 sizeof operator and changing the value of the size expression would not affect the
28275 <li> The order in which any side effects occur among the initialization list expressions in
28278 <li> When a fully expanded macro replacement list contains a function-like macro name
28279 as its last preprocessing token and the next preprocessing token from the source file is
28280 a (, and the fully expanded replacement of that macro ends with the name of the first
28281 macro and the next preprocessing token from the source file is again a (, whether that
28283 <li> The order in which # and ## operations are evaluated during macro substitution
28285 <li> The state of the floating-point status flags when execution passes from a part of the *
28286 program translated with FENV_ACCESS ''off'' to a part translated with
28288 <li> The order in which feraiseexcept raises floating-point exceptions, except as
28290 <li> Whether math_errhandling is a macro or an identifier with external linkage
28292 <li> The results of the frexp functions when the specified value is not a floating-point
28294 <li> The numeric result of the ilogb functions when the correct value is outside the
28295 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>).
28296 <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>).
28297 <!--page 570 -->
28298 <li> The value stored by the remquo functions in the object pointed to by quo when y is
28300 <li> Whether a comparison macro argument that is represented in a format wider than its
28302 <li> Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
28303 <li> Whether va_copy and va_end are macros or identifiers with external linkage
28305 <li> The hexadecimal digit before the decimal point when a non-normalized floating-point
28306 number is printed with an a or A conversion specifier (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
28307 <li> The value of the file position indicator after a successful call to the ungetc function
28308 for a text stream, or the ungetwc function for any stream, until all pushed-back
28309 characters are read or discarded (<a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.28.3.10">7.28.3.10</a>).
28310 <li> The details of the value stored by the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>).
28311 <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>).
28312 <li> Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
28313 functions convert a minus-signed sequence to a negative number directly or by
28314 negating the value resulting from converting the corresponding unsigned sequence
28316 <li> The order and contiguity of storage allocated by successive calls to the calloc,
28318 <li> The amount of storage allocated by a successful call to the calloc, malloc, or
28320 <li> Which of two elements that compare as equal is matched by the bsearch function
28322 <li> The order of two elements that compare as equal in an array sorted by the qsort
28324 <li> The encoding of the calendar time returned by the time function (<a href="#7.26.2.4">7.26.2.4</a>).
28325 <li> The characters stored by the strftime or wcsftime function if any of the time
28326 values being converted is outside the normal range (<a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.5.1">7.28.5.1</a>).
28327 <li> The conversion state after an encoding error occurs (<a href="#7.28.6.3.2">7.28.6.3.2</a>, <a href="#7.28.6.3.3">7.28.6.3.3</a>, <a href="#7.28.6.4.1">7.28.6.4.1</a>,
28329 <li> The resulting value when the ''invalid'' floating-point exception is raised during
28331 <!--page 571 -->
28332 <li> Whether conversion of non-integer IEC 60559 floating values to integer raises the
28334 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
28336 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
28337 floating-point exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
28338 <li> The exponent value stored by frexp for a NaN or infinity (<a href="#F.10.3.4">F.10.3.4</a>).
28339 <li> The numeric result returned by the lrint, llrint, lround, and llround
28340 functions if the rounded value is outside the range of the return type (<a href="#F.10.6.5">F.10.6.5</a>,
28342 <li> The sign of one part of the complex result of several math functions for certain
28343 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>,
28344 <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>).
28345 </ul>
28349 <p><!--para 1 -->
28350 The behavior is undefined in the following circumstances:
28351 <ul>
28352 <li> A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
28353 (clause 4).
28354 <li> A nonempty source file does not end in a new-line character which is not immediately
28355 preceded by a backslash character or ends in a partial preprocessing token or
28357 <li> Token concatenation produces a character sequence matching the syntax of a
28359 <li> A program in a hosted environment does not define a function named main using one
28362 <li> A character not in the basic source character set is encountered in a source file, except
28363 in an identifier, a character constant, a string literal, a header name, a comment, or a
28365 <li> An identifier, comment, string literal, character constant, or header name contains an
28366 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>).
28367 <li> The same identifier has both internal and external linkage in the same translation unit
28370 <!--page 572 -->
28371 <li> The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
28372 <li> The value of an object with automatic storage duration is used while it is
28373 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>).
28374 <li> A trap representation is read by an lvalue expression that does not have character type
28376 <li> A trap representation is produced by a side effect that modifies any part of the object
28377 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
28378 <li> The operands to certain operators are such that they could produce a negative zero
28379 result, but the implementation does not support negative zeros (<a href="#6.2.6.2">6.2.6.2</a>).
28380 <li> Two declarations of the same object or function specify types that are not compatible
28382 <li> A program requires the formation of a composite type from a variable length array
28383 type whose size is specified by an expression that is not evaluated (<a href="#6.2.7">6.2.7</a>).
28384 <li> Conversion to or from an integer type produces a value outside the range that can be
28386 <li> Demotion of one real floating type to another produces a value outside the range that
28389 <li> A non-array lvalue with an incomplete type is used in a context that requires the value
28391 <li> An lvalue designating an object of automatic storage duration that could have been
28392 declared with the register storage class is used in a context that requires the value
28394 <li> An lvalue having array type is converted to a pointer to the initial element of the
28396 <li> An attempt is made to use the value of a void expression, or an implicit or explicit
28398 <li> Conversion of a pointer to an integer type produces a value outside the range that can
28400 <li> Conversion between two pointer types produces a result that is incorrectly aligned
28402 <li> A pointer is used to call a function whose type is not compatible with the referenced
28404 <!--page 573 -->
28405 <li> An unmatched ' or " character is encountered on a logical source line during
28409 <li> A universal character name in an identifier does not designate a character whose
28411 <li> The initial character of an identifier is a universal character name designating a digit
28413 <li> Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
28417 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
28419 <li> A side effect on a scalar object is unsequenced relative to either a different side effect
28420 on the same scalar object or a value computation using the value of the same scalar
28422 <li> An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
28423 <li> An object has its stored value accessed other than by an lvalue of an allowable type
28425 <li> For a call to a function without a function prototype in scope, the number of *
28427 <li> For call to a function without a function prototype in scope where the function is
28428 defined with a function prototype, either the prototype ends with an ellipsis or the
28429 types of the arguments after promotion are not compatible with the types of the
28431 <li> For a call to a function without a function prototype in scope where the function is not
28432 defined with a function prototype, the types of the arguments after promotion are not
28433 compatible with those of the parameters after promotion (with certain exceptions)
28435 <li> A function is defined with a type that is not compatible with the type (of the
28436 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
28438 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
28439 <!--page 574 -->
28440 <li> A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
28441 <li> The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
28442 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
28443 integer type produces a result that does not point into, or just beyond, the same array
28445 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
28446 integer type produces a result that points just beyond the array object and is used as
28448 <li> Pointers that do not point into, or just beyond, the same array object are subtracted
28450 <li> An array subscript is out of range, even if an object is apparently accessible with the
28453 <li> The result of subtracting two pointers is not representable in an object of type
28455 <li> An expression is shifted by a negative number or by an amount greater than or equal
28457 <li> An expression having signed promoted type is left-shifted and either the value of the
28458 expression is negative or the result of shifting would be not be representable in the
28460 <li> Pointers that do not point to the same aggregate or union (nor just beyond the same
28462 <li> An object is assigned to an inexactly overlapping object or to an exactly overlapping
28464 <li> An expression that is required to be an integer constant expression does not have an
28465 integer type; has operands that are not integer constants, enumeration constants,
28466 character constants, sizeof expressions whose results are integer constants, or
28467 immediately-cast floating constants; or contains casts (outside operands to sizeof
28468 operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
28469 <li> A constant expression in an initializer is not, or does not evaluate to, one of the
28470 following: an arithmetic constant expression, a null pointer constant, an address
28471 constant, or an address constant for a complete object type plus or minus an integer
28473 <li> An arithmetic constant expression does not have arithmetic type; has operands that
28474 are not integer constants, floating constants, enumeration constants, character
28475 constants, or sizeof expressions; or contains casts (outside operands to sizeof
28476 <!--page 575 -->
28477 operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
28479 address &, or indirection * operator or a pointer cast in creating an address constant
28481 <li> An identifier for an object is declared with no linkage and the type of the object is
28482 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
28483 <li> A function is declared at block scope with an explicit storage-class specifier other
28485 <li> A structure or union is defined as containing no named members, no anonymous
28487 <li> An attempt is made to access, or generate a pointer to just past, a flexible array
28488 member of a structure when the referenced object provides no elements for that array
28490 <li> When the complete type is needed, an incomplete structure or union type is not
28491 completed in the same scope by another declaration of the tag that defines the content
28493 <li> An attempt is made to modify an object defined with a const-qualified type through
28495 <li> An attempt is made to refer to an object defined with a volatile-qualified type through
28497 <li> The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>). *
28498 <li> Two qualified types that are required to be compatible do not have the identically
28500 <li> An object which has been modified is accessed through a restrict-qualified pointer to
28501 a const-qualified type, or through a restrict-qualified pointer and another pointer that
28503 <li> A restrict-qualified pointer is assigned a value based on another restricted pointer
28504 whose associated block neither began execution before the block associated with this
28506 <li> A function with external linkage is declared with an inline function specifier, but is
28508 <li> A function declared with a _Noreturn function specifier returns to its caller (<a href="#6.7.4">6.7.4</a>).
28509 <li> The definition of an object has an alignment specifier and another declaration of that
28511 <!--page 576 -->
28512 <li> Declarations of an object in different translation units have different alignment
28514 <li> Two pointer types that are required to be compatible are not identically qualified, or
28516 <li> The size expression in an array declaration is not a constant expression and evaluates
28518 <li> In a context requiring two array types to be compatible, they do not have compatible
28519 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.6.2">6.7.6.2</a>).
28520 <li> A declaration of an array parameter includes the keyword static within the [ and
28521 ] and the corresponding argument does not provide access to the first element of an
28523 <li> A storage-class specifier or type qualifier modifies the keyword void as a function
28525 <li> In a context requiring two function types to be compatible, they do not have
28526 compatible return types, or their parameters disagree in use of the ellipsis terminator
28527 or the number and type of parameters (after default argument promotion, when there
28528 is no parameter type list or when one type is specified by a function definition with an
28530 <li> The value of an unnamed member of a structure or union is used (<a href="#6.7.9">6.7.9</a>).
28531 <li> The initializer for a scalar is neither a single expression nor a single expression
28533 <li> The initializer for a structure or union object that has automatic storage duration is
28534 neither an initializer list nor a single expression that has compatible structure or union
28536 <li> The initializer for an aggregate or union, other than an array initialized by a string
28537 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.9">6.7.9</a>).
28538 <li> An identifier with external linkage is used, but in the program there does not exist
28539 exactly one external definition for the identifier, or the identifier is not used and there
28541 <li> A function definition includes an identifier list, but the types of the parameters are not
28543 <li> An adjusted parameter type in a function definition is not a complete object type
28545 <li> A function that accepts a variable number of arguments is defined without a
28547 <!--page 577 -->
28548 <li> The } that terminates a function is reached, and the value of the function call is used
28550 <li> An identifier for an object with internal linkage and an incomplete type is declared
28552 <li> The token defined is generated during the expansion of a #if or #elif
28553 preprocessing directive, or the use of the defined unary operator does not match
28555 <li> The #include preprocessing directive that results after expansion does not match
28557 <li> The character sequence in an #include preprocessing directive does not start with a
28559 <li> There are sequences of preprocessing tokens within the list of macro arguments that
28561 <li> The result of the preprocessing operator # is not a valid character string literal
28563 <li> The result of the preprocessing operator ## is not a valid preprocessing token
28565 <li> The #line preprocessing directive that results after expansion does not match one of
28566 the two well-defined forms, or its digit sequence specifies zero or a number greater
28568 <li> A non-STDC #pragma preprocessing directive that is documented as causing
28569 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
28570 <li> A #pragma STDC preprocessing directive does not match one of the well-defined
28572 <li> The name of a predefined macro, or the identifier defined, is the subject of a
28574 <li> An attempt is made to copy an object to an overlapping object by use of a library
28575 function, other than as explicitly allowed (e.g., memmove) (clause 7).
28576 <li> A file with the same name as one of the standard headers, not provided as part of the
28577 implementation, is placed in any of the standard places that are searched for included
28579 <li> A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
28580 <li> A function, object, type, or macro that is specified as being declared or defined by
28581 some standard header is used before any header that declares or defines it is included
28583 <!--page 578 -->
28584 <li> A standard header is included while a macro is defined with the same name as a
28586 <li> The program attempts to declare a library function itself, rather than via a standard
28588 <li> The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
28590 <li> The program removes the definition of a macro whose name begins with an
28592 <li> An argument to a library function has an invalid value or a type not expected by a
28594 <li> The pointer passed to a library function array parameter does not have a value such
28596 <li> The macro definition of assert is suppressed in order to access an actual function
28599 <li> The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
28600 any context other than outside all external declarations or preceding all explicit
28601 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>).
28602 <li> The value of an argument to a character handling function is neither equal to the value
28604 <li> A macro definition of errno is suppressed in order to access an actual object, or the
28606 <li> Part of the program tests floating-point status flags, sets floating-point control modes,
28607 or runs under non-default mode settings, but was translated with the state for the
28609 <li> The exception-mask argument for one of the functions that provide access to the
28610 floating-point status flags has a nonzero value not obtained by bitwise OR of the
28612 <li> The fesetexceptflag function is used to set floating-point status flags that were
28613 not specified in the call to the fegetexceptflag function that provided the value
28615 <li> The argument to fesetenv or feupdateenv is neither an object set by a call to
28616 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>).
28617 <li> The value of the result of an integer arithmetic or conversion function cannot be
28618 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>).
28619 <!--page 579 -->
28620 <li> The program modifies the string pointed to by the value returned by the setlocale
28622 <li> The program modifies the structure pointed to by the value returned by the
28624 <li> A macro definition of math_errhandling is suppressed or the program defines
28626 <li> An argument to a floating-point classification or comparison macro is not of real
28628 <li> A macro definition of setjmp is suppressed in order to access an actual function, or
28630 <li> An invocation of the setjmp macro occurs other than in an allowed context
28632 <li> The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
28633 <li> After a longjmp, there is an attempt to access the value of an object of automatic
28634 storage duration that does not have volatile-qualified type, local to the function
28635 containing the invocation of the corresponding setjmp macro, that was changed
28637 <li> The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
28638 <li> A signal handler returns when the signal corresponded to a computational exception
28640 <li> A signal occurs as the result of calling the abort or raise function, and the signal
28642 <li> A signal occurs other than as the result of calling the abort or raise function, and
28643 the signal handler refers to an object with static or thread storage duration that is not a
28644 lock-free atomic object other than by assigning a value to an object declared as
28645 volatile sig_atomic_t, or calls any function in the standard library other
28646 than the abort function, the _Exit function, the quick_exit function, or the
28648 <li> The value of errno is referred to after a signal occurred other than as the result of
28649 calling the abort or raise function and the corresponding signal handler obtained
28651 <li> A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
28652 <li> A function with a variable number of arguments attempts to access its varying
28653 arguments other than through a properly declared and initialized va_list object, or
28654 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>).
28655 <!--page 580 -->
28656 <li> The macro va_arg is invoked using the parameter ap that was passed to a function
28658 <li> A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
28659 order to access an actual function, or the program defines an external identifier with
28661 <li> The va_start or va_copy macro is invoked without a corresponding invocation
28662 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>,
28664 <li> The type parameter to the va_arg macro is not such that a pointer to an object of
28666 <li> The va_arg macro is invoked when there is no actual next argument, or with a
28667 specified type that is not compatible with the promoted type of the actual next
28669 <li> The va_copy or va_start macro is called to initialize a va_list that was
28670 previously initialized by either macro without an intervening invocation of the
28671 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>).
28672 <li> The parameter parmN of a va_start macro is declared with the register
28673 storage class, with a function or array type, or with a type that is not compatible with
28674 the type that results after application of the default argument promotions (<a href="#7.16.1.4">7.16.1.4</a>).
28675 <li> The member designator parameter of an offsetof macro is an invalid right
28676 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.19">7.19</a>).
28677 <li> The argument in an instance of one of the integer-constant macros is not a decimal,
28678 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
28680 <li> A byte input/output function is applied to a wide-oriented stream, or a wide character
28682 <li> Use is made of any portion of a file beyond the most recent wide character written to
28684 <li> The value of a pointer to a FILE object is used after the associated file is closed
28686 <li> The stream for the fflush function points to an input stream or to an update stream
28688 <li> The string pointed to by the mode argument in a call to the fopen function does not
28690 <li> An output operation on an update stream is followed by an input operation without an
28691 intervening call to the fflush function or a file positioning function, or an input
28692 <!--page 581 -->
28693 operation on an update stream is followed by an output operation with an intervening
28695 <li> An attempt is made to use the contents of the array that was supplied in a call to the
28697 <li> There are insufficient arguments for the format in a call to one of the formatted
28698 input/output functions, or an argument does not have an appropriate type (<a href="#7.21.6.1">7.21.6.1</a>,
28699 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>).
28700 <li> The format in a call to one of the formatted input/output functions or to the
28701 strftime or wcsftime function is not a valid multibyte character sequence that
28702 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="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>,
28704 <li> In a call to one of the formatted output functions, a precision appears with a
28705 conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
28706 <li> A conversion specification for a formatted output function uses an asterisk to denote
28707 an argument-supplied field width or precision, but the corresponding argument is not
28710 conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
28711 <li> A conversion specification for one of the formatted input/output functions uses a
28712 length modifier with a conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>,
28713 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>).
28714 <li> An s conversion specifier is encountered by one of the formatted output functions,
28715 and the argument is missing the null terminator (unless a precision is specified that
28716 does not require null termination) (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
28717 <li> An n conversion specification for one of the formatted input/output functions includes
28718 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.21.6.1">7.21.6.1</a>,
28719 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>).
28720 <li> A % conversion specifier is encountered by one of the formatted input/output
28721 functions, but the complete conversion specification is not exactly %% (<a href="#7.21.6.1">7.21.6.1</a>,
28722 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>).
28723 <li> An invalid conversion specification is found in the format for one of the formatted
28724 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>,
28725 <a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#7.28.5.1">7.28.5.1</a>).
28726 <li> The number of characters transmitted by a formatted output function is greater than
28727 INT_MAX (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.10">7.21.6.10</a>).
28728 <!--page 582 -->
28729 <li> The result of a conversion by one of the formatted input functions cannot be
28730 represented in the corresponding object, or the receiving object does not have an
28732 <li> A c, s, or [ conversion specifier is encountered by one of the formatted input
28733 functions, and the array pointed to by the corresponding argument is not large enough
28734 to accept the input sequence (and a null terminator if the conversion specifier is s or
28736 <li> A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
28737 formatted input functions, but the input is not a valid multibyte character sequence
28738 that begins in the initial shift state (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
28739 <li> The input item for a %p conversion by one of the formatted input functions is not a
28740 value converted earlier during the same program execution (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
28741 <li> The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
28742 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
28743 vwscanf function is called with an improperly initialized va_list argument, or
28744 the argument is used (other than in an invocation of va_end) after the function
28745 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>,
28746 <a href="#7.28.2.5">7.28.2.5</a>, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.7">7.28.2.7</a>, <a href="#7.28.2.8">7.28.2.8</a>, <a href="#7.28.2.9">7.28.2.9</a>, <a href="#7.28.2.10">7.28.2.10</a>).
28747 <li> The contents of the array supplied in a call to the fgets or fgetws function are
28748 used after a read error occurred (<a href="#7.21.7.2">7.21.7.2</a>, <a href="#7.28.3.2">7.28.3.2</a>).
28749 <li> The file position indicator for a binary stream is used after a call to the ungetc
28751 <li> The file position indicator for a stream is used after an error occurred during a call to
28752 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>).
28753 <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>).
28754 <li> The fseek function is called for a text stream with a nonzero offset and either the
28755 offset was not returned by a previous successful call to the ftell function on a
28756 stream associated with the same file or whence is not SEEK_SET (<a href="#7.21.9.2">7.21.9.2</a>).
28757 <li> The fsetpos function is called to set a position that was not returned by a previous
28758 successful call to the fgetpos function on a stream associated with the same file
28760 <li> A non-null pointer returned by a call to the calloc, malloc, or realloc function
28762 <li> The value of a pointer that refers to space deallocated by a call to the free or
28764 <!--page 583 -->
28765 <li> The alignment requested of the aligned_alloc function is not valid or not
28766 supported by the implementation, or the size requested is not an integral multiple of
28768 <li> The pointer argument to the free or realloc function does not match a pointer
28769 earlier returned by a memory management function, or the space has been deallocated
28770 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>).
28771 <li> The value of the object allocated by the malloc function is used (<a href="#7.22.3.4">7.22.3.4</a>).
28772 <li> The value of any bytes in a new object allocated by the realloc function beyond
28774 <li> The program calls the exit or quick_exit function more than once, or calls both
28776 <li> During the call to a function registered with the atexit or at_quick_exit
28777 function, a call is made to the longjmp function that would terminate the call to the
28779 <li> The string set up by the getenv or strerror function is modified by the program
28781 <li> A command is executed through the system function in a way that is documented as
28782 causing termination or some other form of undefined behavior (<a href="#7.22.4.8">7.22.4.8</a>).
28783 <li> A searching or sorting utility function is called with an invalid pointer argument, even
28785 <li> The comparison function called by a searching or sorting utility function alters the
28786 contents of the array being searched or sorted, or returns ordering values
28788 <li> The array being searched by the bsearch function does not have its elements in
28790 <li> The current conversion state is used by a multibyte/wide character conversion
28792 <li> A string or wide string utility function is instructed to access an array beyond the end
28794 <li> A string or wide string utility function is called with an invalid pointer argument, even
28796 <li> The contents of the destination array are used after a call to the strxfrm,
28797 strftime, wcsxfrm, or wcsftime function in which the specified length was
28798 too small to hold the entire null-terminated result (<a href="#7.23.4.5">7.23.4.5</a>, <a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.4.4.4">7.28.4.4.4</a>,
28800 <!--page 584 -->
28801 <li> The first argument in the very first call to the strtok or wcstok is a null pointer
28803 <li> The type of an argument to a type-generic macro is not compatible with the type of
28805 <li> A complex argument is supplied for a generic parameter of a type-generic macro that
28807 <li> At least one field of the broken-down time passed to asctime contains a value
28808 outside its normal range, or the calculated year exceeds four digits or is less than the
28810 <li> The argument corresponding to an s specifier without an l qualifier in a call to the
28811 fwprintf function does not point to a valid multibyte character sequence that
28813 <li> In a call to the wcstok function, the object pointed to by ptr does not have the
28814 value stored by the previous call for the same wide string (<a href="#7.28.4.5.7">7.28.4.5.7</a>).
28816 <li> The value of an argument of type wint_t to a wide character classification or case
28817 mapping function is neither equal to the value of WEOF nor representable as a
28819 <li> The iswctype function is called using a different LC_CTYPE category from the
28820 one in effect for the call to the wctype function that returned the description
28822 <li> The towctrans function is called using a different LC_CTYPE category from the
28823 one in effect for the call to the wctrans function that returned the description
28825 </ul>
28830 A conforming implementation is required to document its choice of behavior in each of
28831 the areas listed in this subclause. The following are implementation-defined:
28832 <!--page 585 -->
28837 <ul>
28838 <li> How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
28839 <li> Whether each nonempty sequence of white-space characters other than new-line is
28840 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
28841 </ul>
28846 <ul>
28847 <li> The mapping between physical source file multibyte characters and the source
28849 <li> The name and type of the function called at program startup in a freestanding
28851 <li> The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
28852 <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>).
28853 <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>).
28855 <li> Whether a program can have more than one thread of execution in a freestanding
28857 <li> The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
28858 <li> Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
28860 <li> Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
28862 <li> The set of environment names and the method for altering the environment list used
28864 <li> The manner of execution of the string by the system function (<a href="#7.22.4.8">7.22.4.8</a>).
28865 </ul>
28870 <ul>
28871 <li> Which additional multibyte characters may appear in identifiers and their
28873 <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>).
28874 <!--page 586 -->
28875 </ul>
28880 <ul>
28883 <li> The unique value of the member of the execution character set produced for each of
28885 <li> The value of a char object into which has been stored any character other than a
28887 <li> Which of signed char or unsigned char has the same range, representation,
28889 <li> The mapping of members of the source character set (in character constants and string
28890 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>).
28891 <li> The value of an integer character constant containing more than one character or
28892 containing a character or escape sequence that does not map to a single-byte
28894 <li> The value of a wide character constant containing more than one multibyte character
28895 or a single multibyte character that maps to multiple members of the extended
28896 execution character set, or containing a multibyte character or escape sequence not
28898 <li> The current locale used to convert a wide character constant consisting of a single
28899 multibyte character that maps to a member of the extended execution character set
28901 <li> Whether differently-prefixed wide string literal tokens can be concatenated and, if so,
28903 <li> The current locale used to convert a wide string literal into corresponding wide
28905 <li> The value of a string literal containing a multibyte character or escape sequence not
28907 <li> The encoding of any of wchar_t, char16_t, and char32_t where the
28908 corresponding standard encoding macro (__STDC_ISO_10646__,
28910 <!--page 587 -->
28911 </ul>
28916 <ul>
28917 <li> Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
28918 <li> Whether signed integer types are represented using sign and magnitude, two's
28919 complement, or ones' complement, and whether the extraordinary value is a trap
28921 <li> The rank of any extended integer type relative to another extended integer type with
28923 <li> The result of, or the signal raised by, converting an integer to a signed integer type
28924 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
28926 </ul>
28931 <ul>
28932 <li> The accuracy of the floating-point operations and of the library functions in
28933 <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>).
28934 <li> The accuracy of the conversions between floating-point internal representations and
28935 string representations performed by the library functions in <a href="#7.21"><stdio.h></a>,
28936 <a href="#7.22"><stdlib.h></a>, and <a href="#7.28"><wchar.h></a> (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
28937 <li> The rounding behaviors characterized by non-standard values of FLT_ROUNDS
28939 <li> The evaluation methods characterized by non-standard negative values of
28941 <li> The direction of rounding when an integer is converted to a floating-point number that
28943 <li> The direction of rounding when a floating-point number is converted to a narrower
28945 <li> How the nearest representable value or the larger or smaller representable value
28946 immediately adjacent to the nearest representable value is chosen for certain floating
28948 <li> Whether and how floating expressions are contracted when not disallowed by the
28951 <li> Additional floating-point exceptions, rounding modes, environments, and
28954 <!--page 588 -->
28955 </ul>
28960 <ul>
28961 <li> The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
28962 <li> The size of the result of subtracting two pointers to elements of the same array
28964 </ul>
28969 <ul>
28970 <li> The extent to which suggestions made by using the register storage-class
28972 <li> The extent to which suggestions made by using the inline function specifier are
28974 </ul>
28977 <h4><a name="J.3.9" href="#J.3.9">J.3.9 Structures, unions, enumerations, and bit-fields</a></h4>
28979 <ul>
28980 <li> Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
28982 <li> Allowable bit-field types other than _Bool, signed int, and unsigned int
28985 <li> Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
28987 <li> The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
28988 no problem unless binary data written by one implementation is read by another.
28990 </ul>
28995 <ul>
28996 <li> What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
28997 </ul>
29002 <ul>
29003 <li> The locations within #pragma directives where header name preprocessing tokens
29005 <li> How sequences in both forms of header names are mapped to headers or external
29007 <li> Whether the value of a character constant in a constant expression that controls
29008 conditional inclusion matches the value of the same character constant in the
29010 <li> Whether the value of a single-character character constant in a constant expression
29012 <!--page 589 -->
29013 <li> The places that are searched for an included < > delimited header, and how the places
29017 <li> The method by which preprocessing tokens (possibly resulting from macro
29018 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
29020 <li> Whether the # operator inserts a \ character before the \ character that begins a
29021 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
29022 <li> The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
29023 <li> The definitions for __DATE__ and __TIME__ when respectively, the date and
29025 </ul>
29030 <ul>
29031 <li> Any library facilities available to a freestanding program, other than the minimal set
29033 <li> The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
29034 <li> The representation of the floating-point status flags stored by the
29036 <li> Whether the feraiseexcept function raises the ''inexact'' floating-point
29037 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
29041 <li> The types defined for float_t and double_t when the value of the
29043 <li> Domain errors for the mathematics functions, other than those required by this
29045 <li> The values returned by the mathematics functions on domain errors or pole errors
29047 <li> The values returned by the mathematics functions on underflow range errors, whether
29048 errno is set to the value of the macro ERANGE when the integer expression
29049 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
29050 floating-point exception is raised when the integer expression math_errhandling
29052 <!--page 590 -->
29053 <li> Whether a domain error occurs or zero is returned when an fmod function has a
29055 <li> Whether a domain error occurs or zero is returned when a remainder function has
29059 <li> Whether a domain error occurs or zero is returned when a remquo function has a
29061 <li> Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
29062 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>).
29064 <li> Whether the last line of a text stream requires a terminating new-line character
29066 <li> Whether space characters that are written out to a text stream immediately before a
29068 <li> The number of null characters that may be appended to data written to a binary
29070 <li> Whether the file position indicator of an append-mode stream is initially positioned at
29072 <li> Whether a write on a text stream causes the associated file to be truncated beyond that
29077 <li> Whether the same file can be simultaneously open multiple times (<a href="#7.21.3">7.21.3</a>).
29078 <li> The nature and choice of encodings used for multibyte characters in files (<a href="#7.21.3">7.21.3</a>).
29080 <li> The effect if a file with the new name exists prior to a call to the rename function
29082 <li> Whether an open temporary file is removed upon abnormal program termination
29084 <li> Which changes of mode are permitted (if any), and under what circumstances
29086 <!--page 591 -->
29087 <li> The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
29088 sequence printed for a NaN (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
29089 <li> The output for %p conversion in the fprintf or fwprintf function (<a href="#7.21.6.1">7.21.6.1</a>,
29091 <li> The interpretation of a - character that is neither the first nor the last character, nor
29092 the second where a ^ character is the first, in the scanlist for %[ conversion in the
29093 fscanf or fwscanf function (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>).
29094 <li> The set of sequences matched by a %p conversion and the interpretation of the
29095 corresponding input item in the fscanf or fwscanf function (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
29096 <li> The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
29097 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>).
29098 <li> The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
29099 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
29101 <li> Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
29102 function sets errno to ERANGE when underflow occurs (<a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>).
29103 <li> Whether the calloc, malloc, and realloc functions return a null pointer or a
29104 pointer to an allocated object when the size requested is zero (<a href="#7.22.3">7.22.3</a>).
29105 <li> Whether open streams with unwritten buffered data are flushed, open streams are
29106 closed, or temporary files are removed when the abort or _Exit function is called
29108 <li> The termination status returned to the host environment by the abort, exit,
29109 _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>).
29110 <li> The value returned by the system function when its argument is not a null pointer
29113 <li> The range and precision of times representable in clock_t and time_t (<a href="#7.26">7.26</a>).
29115 <li> The replacement string for the %Z specifier to the strftime, and wcsftime
29116 functions in the "C" locale (<a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.5.1">7.28.5.1</a>).
29117 <li> Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
29118 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.10">F.10</a>).
29119 <!--page 592 -->
29120 </ul>
29125 <ul>
29126 <li> The values or expressions assigned to the macros specified in the headers
29127 <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>).
29128 <li> The result of attempting to indirectly access an object with automatic or thread
29129 storage duration from a thread other than the one with which it is associated (<a href="#6.2.4">6.2.4</a>).
29130 <li> The number, order, and encoding of bytes in any object (when not explicitly specified
29132 <li> Whether any extended alignments are supported and the contexts in which they are
29134 <li> Valid alignment values other than those returned by an alignof expression for
29136 <li> The value of the result of the sizeof and alignof operators (<a href="#6.5.3.4">6.5.3.4</a>).
29137 </ul>
29142 The following characteristics of a hosted environment are locale-specific and are required
29143 to be documented by the implementation:
29144 <ul>
29145 <li> Additional members of the source and execution character sets beyond the basic
29147 <li> The presence, meaning, and representation of additional multibyte characters in the
29149 <li> The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
29154 <li> The sets of characters tested for by the isalpha, isblank, islower, ispunct,
29155 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
29156 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>,
29157 <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.29.2.1.2">7.29.2.1.2</a>, <a href="#7.29.2.1.3">7.29.2.1.3</a>, <a href="#7.29.2.1.7">7.29.2.1.7</a>, <a href="#7.29.2.1.9">7.29.2.1.9</a>, <a href="#7.29.2.1.10">7.29.2.1.10</a>, <a href="#7.29.2.1.11">7.29.2.1.11</a>).
29159 <li> Additional subject sequences accepted by the numeric conversion functions (<a href="#7.22.1">7.22.1</a>,
29161 <li> The collation sequence of the execution character set (<a href="#7.23.4.3">7.23.4.3</a>, <a href="#7.28.4.4.2">7.28.4.4.2</a>).
29162 <!--page 593 -->
29163 <li> The contents of the error message strings set up by the strerror function
29165 <li> The formats for time and date (<a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.5.1">7.28.5.1</a>).
29166 <li> Character mappings that are supported by the towctrans function (<a href="#7.29.1">7.29.1</a>).
29167 <li> Character classifications that are supported by the iswctype function (<a href="#7.29.1">7.29.1</a>).
29168 </ul>
29173 The following extensions are widely used in many systems, but are not portable to all
29174 implementations. The inclusion of any extension that may cause a strictly conforming
29175 program to become invalid renders an implementation nonconforming. Examples of such
29176 extensions are new keywords, extra library functions declared in standard headers, or
29177 predefined macros with names that do not begin with an underscore.
29182 In a hosted environment, the main function receives a third argument, char *envp[],
29183 that points to a null-terminated array of pointers to char, each of which points to a string
29184 that provides information about the environment for this execution of the program
29190 Characters other than the underscore _, letters, and digits, that are not part of the basic
29191 source character set (such as the dollar sign $, or characters in national character sets)
29197 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
29202 A function identifier, or the identifier of an object the declaration of which contains the
29208 String literals are modifiable (in which case, identical string literals should denote distinct
29210 <!--page 594 -->
29215 Additional arithmetic types, such as __int128 or double double, and their
29216 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
29217 more range or precision than long double, may be used for evaluating expressions of
29218 other floating types, and may be used to define float_t or double_t.
29223 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
29226 A pointer to a function may be cast to a pointer to an object or to void, allowing a
29227 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
29232 A bit-field may be declared with a type other than _Bool, unsigned int, or
29238 The fortran function specifier may be used in a function declaration to indicate that
29239 calls suitable for FORTRAN should be generated, or that a different representation for the
29245 The asm keyword may be used to insert assembly language directly into the translator
29246 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
29247 <pre>
29248 asm ( character-string-literal );
29249 </pre>
29254 There may be more than one external definition for the identifier of an object, with or
29255 without the explicit use of the keyword extern; if the definitions disagree, or more than
29261 Macro names that do not begin with an underscore, describing the translation and
29262 execution environments, are defined by the implementation before translation begins
29264 <!--page 595 -->
29269 If any floating-point status flags are set on normal termination after all calls to functions
29270 registered by the atexit function have been made (see <a href="#7.22.4.4">7.22.4.4</a>), the implementation
29271 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
29276 Handlers for specific signals are called with extra arguments in addition to the signal
29280 <h4><a name="J.5.15" href="#J.5.15">J.5.15 Additional stream types and file-opening modes</a></h4>
29284 Additional file-opening modes may be specified by characters appended to the mode
29290 The file position indicator is decremented by each successful call to the ungetc or
29291 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>,
29297 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
29298 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
29300 <!--page 596 -->
29304 <pre>
29305 (normative)
29306 Bounds-checking interfaces
29307 </pre>
29312 Traditionally, the C Library has contained many functions that trust the programmer to
29313 provide output character arrays big enough to hold the result being produced. Not only
29314 do these functions not check that the arrays are big enough, they frequently lack the
29315 information needed to perform such checks. While it is possible to write safe, robust, and
29316 error-free code using the existing library, the library tends to promote programming styles
29317 that lead to mysterious failures if a result is too big for the provided array.
29319 A common programming style is to declare character arrays large enough to handle most
29320 practical cases. However, if these arrays are not large enough to handle the resulting
29321 strings, data can be written past the end of the array overwriting other data and program
29322 structures. The program never gets any indication that a problem exists, and so never has
29323 a chance to recover or to fail gracefully.
29325 Worse, this style of programming has compromised the security of computers and
29326 networks. Buffer overflows can often be exploited to run arbitrary code with the
29327 permissions of the vulnerable (defective) program.
29329 If the programmer writes runtime checks to verify lengths before calling library
29330 functions, then those runtime checks frequently duplicate work done inside the library
29331 functions, which discover string lengths as a side effect of doing their job.
29333 This annex provides alternative library functions that promote safer, more secure
29334 programming. The alternative functions verify that output buffers are large enough for
29335 the intended result and return a failure indicator if they are not. Data is never written past
29336 the end of an array. All string results are null terminated.
29338 This annex also addresses another problem that complicates writing robust code:
29339 functions that are not reentrant because they return pointers to static objects owned by the
29340 function. Such functions can be troublesome since a previously returned result can
29341 change if the function is called again, perhaps by another thread.
29342 <!--page 597 -->
29347 This annex specifies a series of optional extensions that can be useful in the mitigation of
29348 security vulnerabilities in programs, and comprise new functions, macros, and types
29349 declared or defined in existing standard headers.
29351 An implementation that defines __STDC_LIB_EXT1__ shall conform to the
29354 Subclause <a href="#K.3">K.3</a> should be read as if it were merged into the parallel structure of named
29355 subclauses of clause 7.
29358 <p><small><a name="note367" href="#note367">367)</a> Implementations that do not define __STDC_LIB_EXT1__ are not required to conform to these
29359 specifications.
29360 </small>
29371 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are not
29372 declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
29373 defined as a macro which expands to the integer constant 0 at the point in the source file
29374 where the appropriate header is first included.
29376 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are
29377 declared and defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
29378 defined as a macro which expands to the integer constant 1 at the point in the source file
29381 It is implementation-defined whether the functions, macros, and types declared or defined
29382 in <a href="#K.3">K.3</a> and its subclauses are declared or defined by their respective headers if
29383 __STDC_WANT_LIB_EXT1__ is not defined as a macro at the point in the source file
29386 Within a preprocessing translation unit, __STDC_WANT_LIB_EXT1__ shall be
29387 defined identically for all inclusions of any headers from subclause <a href="#K.3">K.3</a>. If
29388 __STDC_WANT_LIB_EXT1__ is defined differently for any such inclusion, the
29389 implementation shall issue a diagnostic as if a preprocessor error directive were used.
29392 <!--page 598 -->
29395 <p><small><a name="note368" href="#note368">368)</a> Future revisions of this International Standard may define meanings for other values of
29396 __STDC_WANT_LIB_EXT1__.
29397 </small>
29398 <p><small><a name="note369" href="#note369">369)</a> Subclause <a href="#7.1.3">7.1.3</a> reserves certain names and patterns of names that an implementation may use in
29399 headers. All other names are not reserved, and a conforming implementation is not permitted to use
29400 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
29401 unreserved name is defined in a header when __STDC_WANT_LIB_EXT1__ is defined as 0, the
29402 implementation is not conforming.
29403 </small>
29408 Each macro name in any of the following subclauses is reserved for use as specified if it
29409 is defined by any of its associated headers when included; unless explicitly stated
29412 All identifiers with external linkage in any of the following subclauses are reserved for
29413 use as identifiers with external linkage if any of them are used by the program. None of
29414 them are reserved if none of them are used.
29416 Each identifier with file scope listed in any of the following subclauses is reserved for use
29417 as a macro name and as an identifier with file scope in the same name space if it is
29418 defined by any of its associated headers when included.
29423 An implementation may set errno for the functions defined in this annex, but is not
29424 required to.
29429 Most functions in this annex include as part of their specification a list of runtime-
29430 constraints. These runtime-constraints are requirements on the program using the
29433 Implementations shall verify that the runtime-constraints for a function are not violated
29434 by the program. If a runtime-constraint is violated, the implementation shall call the
29435 currently registered runtime-constraint handler (see set_constraint_handler_s
29436 in <a href="#7.22"><stdlib.h></a>). Multiple runtime-constraint violations in the same call to a library
29437 function result in only one call to the runtime-constraint handler. It is unspecified which
29438 one of the multiple runtime-constraint violations cause the handler to be called.
29440 If the runtime-constraints section for a function states an action to be performed when a
29441 runtime-constraint violation occurs, the function shall perform the action before calling
29442 the runtime-constraint handler. If the runtime-constraints section lists actions that are
29443 prohibited when a runtime-constraint violation occurs, then such actions are prohibited to
29444 the function both before calling the handler and after the handler returns.
29446 The runtime-constraint handler might not return. If the handler does return, the library
29447 function whose runtime-constraint was violated shall return some indication of failure as
29448 given by the returns section in the function's specification.
29452 <!--page 599 -->
29455 <p><small><a name="note370" href="#note370">370)</a> Although runtime-constraints replace many cases of undefined behavior, undefined behavior still
29456 exists in this annex. Implementations are free to detect any case of undefined behavior and treat it as a
29457 runtime-constraint violation by calling the runtime-constraint handler. This license comes directly
29458 from the definition of undefined behavior.
29459 </small>
29466 The type is
29467 <pre>
29468 errno_t
29469 </pre>
29473 <p><small><a name="note371" href="#note371">371)</a> As a matter of programming style, errno_t may be used as the type of something that deals only
29474 with the values that might be found in errno. For example, a function which returns the value of
29475 errno might be declared as having the return type errno_t.
29476 </small>
29483 The type is
29484 <pre>
29485 rsize_t
29486 </pre>
29490 <p><small><a name="note372" href="#note372">372)</a> See the description of the RSIZE_MAX macro in <a href="#7.20"><stdint.h></a>.
29491 </small>
29498 The macro is
29499 <pre>
29500 RSIZE_MAX
29501 </pre>
29502 which expands to a value<sup><a href="#note373"><b>373)</b></a></sup> of type size_t. Functions that have parameters of type
29503 rsize_t consider it a runtime-constraint violation if the values of those parameters are
29504 greater than RSIZE_MAX.
29507 Extremely large object sizes are frequently a sign that an object's size was calculated
29508 incorrectly. For example, negative numbers appear as very large positive numbers when
29509 converted to an unsigned type like size_t. Also, some implementations do not support
29510 objects as large as the maximum value that can be represented by type size_t.
29512 For those reasons, it is sometimes beneficial to restrict the range of object sizes to detect
29513 programming errors. For implementations targeting machines with large address spaces,
29514 it is recommended that RSIZE_MAX be defined as the smaller of the size of the largest
29516 some legitimate, but very large, objects. Implementations targeting machines with small
29517 address spaces may wish to define RSIZE_MAX as SIZE_MAX, which means that there
29519 <!--page 600 -->
29520 is no object size that is considered a runtime-constraint violation.
29523 <p><small><a name="note373" href="#note373">373)</a> The macro RSIZE_MAX need not expand to a constant expression.
29524 </small>
29531 The macros are
29532 <pre>
29533 L_tmpnam_s
29534 </pre>
29535 which expands to an integer constant expression that is the size needed for an array of
29536 char large enough to hold a temporary file name string generated by the tmpnam_s
29537 function;
29538 <pre>
29539 TMP_MAX_S
29540 </pre>
29541 which expands to an integer constant expression that is the maximum number of unique
29542 file names that can be generated by the tmpnam_s function.
29544 The types are
29545 <pre>
29546 errno_t
29547 </pre>
29548 which is type int; and
29549 <pre>
29550 rsize_t
29551 </pre>
29552 which is the type size_t.
29561 <pre>
29562 #define __STDC_WANT_LIB_EXT1__ 1
29564 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
29565 </pre>
29566 Runtime-constraints
29568 streamptr shall not be a null pointer.
29570 If there is a runtime-constraint violation, tmpfile_s does not attempt to create a file.
29573 The tmpfile_s function creates a temporary binary file that is different from any other
29574 existing file and that will automatically be removed when it is closed or at program
29575 termination. If the program terminates abnormally, whether an open temporary file is
29576 removed is implementation-defined. The file is opened for update with "wb+" mode
29577 with the meaning that mode has in the fopen_s function (including the mode's effect
29578 on exclusive access and file permissions).
29579 <!--page 601 -->
29581 If the file was created successfully, then the pointer to FILE pointed to by streamptr
29582 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
29583 to FILE pointed to by streamptr will be set to a null pointer.
29585 It should be possible to open at least TMP_MAX_S temporary files during the lifetime of
29586 the program (this limit may be shared with tmpnam_s) and there should be no limit on
29587 the number simultaneously open other than this limit and any limit on the number of open
29588 files (FOPEN_MAX).
29591 The tmpfile_s function returns zero if it created the file. If it did not create the file or
29592 there was a runtime-constraint violation, tmpfile_s returns a nonzero value.
29598 <pre>
29599 #define __STDC_WANT_LIB_EXT1__ 1
29601 errno_t tmpnam_s(char *s, rsize_t maxsize);
29602 </pre>
29603 Runtime-constraints
29605 s shall not be a null pointer. maxsize shall be less than or equal to RSIZE_MAX.
29606 maxsize shall be greater than the length of the generated file name string.
29609 The tmpnam_s function generates a string that is a valid file name and that is not the
29610 same as the name of an existing file.<sup><a href="#note374"><b>374)</b></a></sup> The function is potentially capable of generating
29611 TMP_MAX_S different strings, but any or all of them may already be in use by existing
29612 files and thus not be suitable return values. The lengths of these strings shall be less than
29613 the value of the L_tmpnam_s macro.
29615 The tmpnam_s function generates a different string each time it is called.
29617 It is assumed that s points to an array of at least maxsize characters. This array will be
29618 set to generated string, as specified below.
29622 <!--page 602 -->
29624 The implementation shall behave as if no library function except tmpnam calls the
29628 After a program obtains a file name using the tmpnam_s function and before the
29629 program creates a file with that name, the possibility exists that someone else may create
29630 a file with that same name. To avoid this race condition, the tmpfile_s function
29631 should be used instead of tmpnam_s when possible. One situation that requires the use
29632 of the tmpnam_s function is when the program needs to create a temporary directory
29633 rather than a temporary file.
29636 If no suitable string can be generated, or if there is a runtime-constraint violation, the
29637 tmpnam_s function writes a null character to s[0] (only if s is not null and maxsize
29638 is greater than zero) and returns a nonzero value.
29640 Otherwise, the tmpnam_s function writes the string in the array pointed to by s and
29641 returns zero.
29644 The value of the macro TMP_MAX_S shall be at least 25.
29647 <p><small><a name="note374" href="#note374">374)</a> Files created using strings generated by the tmpnam_s function are temporary only in the sense that
29648 their names should not collide with those generated by conventional naming rules for the
29649 implementation. It is still necessary to use the remove function to remove such files when their use
29650 is ended, and before program termination. Implementations should take care in choosing the patterns
29651 used for names returned by tmpnam_s. For example, making a thread id part of the names avoids the
29652 race condition and possible conflict when multiple programs run simultaneously by the same user
29653 generate the same temporary file names.
29654 </small>
29655 <p><small><a name="note375" href="#note375">375)</a> An implementation may have tmpnam call tmpnam_s (perhaps so there is only one naming
29656 convention for temporary files), but this is not required.
29657 </small>
29666 <pre>
29667 #define __STDC_WANT_LIB_EXT1__ 1
29669 errno_t fopen_s(FILE * restrict * restrict streamptr,
29670 const char * restrict filename,
29671 const char * restrict mode);
29672 </pre>
29673 Runtime-constraints
29675 None of streamptr, filename, or mode shall be a null pointer.
29677 If there is a runtime-constraint violation, fopen_s does not attempt to open a file.
29678 Furthermore, if streamptr is not a null pointer, fopen_s sets *streamptr to the
29679 null pointer.
29684 <!--page 603 -->
29687 The fopen_s function opens the file whose name is the string pointed to by
29688 filename, and associates a stream with it.
29690 The mode string shall be as described for fopen, with the addition that modes starting
29691 with the character 'w' or 'a' may be preceded by the character 'u', see below:
29692 uw truncate to zero length or create text file for writing, default
29693 <pre>
29694 permissions
29695 </pre>
29696 uwx create text file for writing, default permissions
29697 ua append; open or create text file for writing at end-of-file, default
29698 <pre>
29699 permissions
29700 </pre>
29701 uwb truncate to zero length or create binary file for writing, default
29702 <pre>
29703 permissions
29704 </pre>
29705 uwbx create binary file for writing, default permissions
29706 uab append; open or create binary file for writing at end-of-file, default
29707 <pre>
29708 permissions
29709 </pre>
29710 uw+ truncate to zero length or create text file for update, default
29711 <pre>
29712 permissions
29713 </pre>
29714 uw+x create text file for update, default permissions
29715 ua+ append; open or create text file for update, writing at end-of-file,
29716 <pre>
29717 default permissions
29718 </pre>
29719 uw+b or uwb+ truncate to zero length or create binary file for update, default
29720 <pre>
29721 permissions
29722 </pre>
29723 uw+bx or uwb+x create binary file for update, default permissions
29724 ua+b or uab+ append; open or create binary file for update, writing at end-of-file,
29725 <pre>
29726 default permissions
29727 </pre>
29729 Opening a file with exclusive mode ('x' as the last character in the mode argument)
29730 fails if the file already exists or cannot be created.
29732 To the extent that the underlying system supports the concepts, files opened for writing
29733 shall be opened with exclusive (also known as non-shared) access. If the file is being
29734 created, and the first character of the mode string is not 'u', to the extent that the
29735 underlying system supports it, the file shall have a file permission that prevents other
29736 users on the system from accessing the file. If the file is being created and first character
29737 of the mode string is 'u', then by the time the file has been closed, it shall have the
29740 If the file was opened successfully, then the pointer to FILE pointed to by streamptr
29741 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
29744 <!--page 604 -->
29745 to FILE pointed to by streamptr will be set to a null pointer.
29748 The fopen_s function returns zero if it opened the file. If it did not open the file or if
29749 there was a runtime-constraint violation, fopen_s returns a nonzero value.
29752 <p><small><a name="note376" href="#note376">376)</a> These are the same permissions that the file would have been created with by fopen.
29753 </small>
29759 <pre>
29760 #define __STDC_WANT_LIB_EXT1__ 1
29762 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
29763 const char * restrict filename,
29764 const char * restrict mode,
29765 FILE * restrict stream);
29766 </pre>
29767 Runtime-constraints
29769 None of newstreamptr, mode, and stream shall be a null pointer.
29771 If there is a runtime-constraint violation, freopen_s neither attempts to close any file
29772 associated with stream nor attempts to open a file. Furthermore, if newstreamptr is
29773 not a null pointer, fopen_s sets *newstreamptr to the null pointer.
29776 The freopen_s function opens the file whose name is the string pointed to by
29777 filename and associates the stream pointed to by stream with it. The mode
29778 argument has the same meaning as in the fopen_s function (including the mode's effect
29779 on exclusive access and file permissions).
29781 If filename is a null pointer, the freopen_s function attempts to change the mode of
29782 the stream to that specified by mode, as if the name of the file currently associated with
29783 the stream had been used. It is implementation-defined which changes of mode are
29784 permitted (if any), and under what circumstances.
29786 The freopen_s function first attempts to close any file that is associated with stream.
29787 Failure to close the file is ignored. The error and end-of-file indicators for the stream are
29788 cleared.
29790 If the file was opened successfully, then the pointer to FILE pointed to by
29791 newstreamptr will be set to the value of stream. Otherwise, the pointer to FILE
29792 pointed to by newstreamptr will be set to a null pointer.
29795 The freopen_s function returns zero if it opened the file. If it did not open the file or
29796 there was a runtime-constraint violation, freopen_s returns a nonzero value.
29797 <!--page 605 -->
29802 Unless explicitly stated otherwise, if the execution of a function described in this
29803 subclause causes copying to take place between objects that overlap, the objects take on
29804 unspecified values.
29810 <pre>
29811 #define __STDC_WANT_LIB_EXT1__ 1
29813 int fprintf_s(FILE * restrict stream,
29814 const char * restrict format, ...);
29815 </pre>
29816 Runtime-constraints
29818 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note377"><b>377)</b></a></sup> (modified or
29819 not by flags, field width, or precision) shall not appear in the string pointed to by
29820 format. Any argument to fprintf_s corresponding to a %s specifier shall not be a
29821 null pointer.
29823 If there is a runtime-constraint violation,<sup><a href="#note378"><b>378)</b></a></sup> the fprintf_s function does not attempt
29824 to produce further output, and it is unspecified to what extent fprintf_s produced
29825 output before discovering the runtime-constraint violation.
29828 The fprintf_s function is equivalent to the fprintf function except for the explicit
29829 runtime-constraints listed above.
29832 The fprintf_s function returns the number of characters transmitted, or a negative
29833 value if an output error, encoding error, or runtime-constraint violation occurred.
29838 <!--page 606 -->
29841 <p><small><a name="note377" href="#note377">377)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
29842 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
29843 format string was %%n.
29844 </small>
29845 <p><small><a name="note378" href="#note378">378)</a> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
29846 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
29847 constraint violation.
29848 </small>
29854 <pre>
29855 #define __STDC_WANT_LIB_EXT1__ 1
29857 int fscanf_s(FILE * restrict stream,
29858 const char * restrict format, ...);
29859 </pre>
29860 Runtime-constraints
29862 Neither stream nor format shall be a null pointer. Any argument indirected though in
29863 order to store converted input shall not be a null pointer.
29865 If there is a runtime-constraint violation,<sup><a href="#note379"><b>379)</b></a></sup> the fscanf_s function does not attempt to
29866 perform further input, and it is unspecified to what extent fscanf_s performed input
29867 before discovering the runtime-constraint violation.
29870 The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion
29871 specifiers apply to a pair of arguments (unless assignment suppression is indicated by a
29872 *). The first of these arguments is the same as for fscanf. That argument is
29873 immediately followed in the argument list by the second argument, which has type
29874 rsize_t and gives the number of elements in the array pointed to by the first argument
29875 of the pair. If the first argument points to a scalar object, it is considered to be an array of
29878 A matching failure occurs if the number of elements in a receiving object is insufficient to
29879 hold the converted input (including any trailing null character).
29882 The fscanf_s function returns the value of the macro EOF if an input failure occurs
29883 before any conversion or if there is a runtime-constraint violation. Otherwise, the
29885 <!--page 607 -->
29886 fscanf_s function returns the number of input items assigned, which can be fewer than
29887 provided for, or even zero, in the event of an early matching failure.
29889 EXAMPLE 1 The call:
29890 <pre>
29891 #define __STDC_WANT_LIB_EXT1__ 1
29893 /* ... */
29894 int n, i; float x; char name[50];
29896 </pre>
29897 with the input line:
29898 <pre>
29899 25 54.32E-1 thompson
29900 </pre>
29901 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
29902 thompson\0.
29905 EXAMPLE 2 The call:
29906 <pre>
29907 #define __STDC_WANT_LIB_EXT1__ 1
29909 /* ... */
29910 int n; char s[5];
29911 n = fscanf_s(stdin, "%s", s, sizeof s);
29912 </pre>
29913 with the input line:
29914 <pre>
29915 hello
29916 </pre>
29917 will assign to n the value 0 since a matching failure occurred because the sequence hello\0 requires an
29918 array of six characters to store it.
29922 <p><small><a name="note379" href="#note379">379)</a> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
29923 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
29924 constraint violation.
29925 </small>
29926 <p><small><a name="note380" href="#note380">380)</a> If the format is known at translation time, an implementation may issue a diagnostic for any argument
29927 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
29928 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
29929 the format is not known at translation time. For example, an implementation may issue a diagnostic
29930 for each argument after format that has of type pointer to one of char, signed char,
29931 unsigned char, or void that is not followed by an argument of a type compatible with
29932 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
29933 using the hh length modifier, a length argument must follow the pointer argument. Another useful
29934 diagnostic could flag any non-pointer argument following format that did not have a type
29935 compatible with rsize_t.
29936 </small>
29942 <pre>
29943 #define __STDC_WANT_LIB_EXT1__ 1
29945 int printf_s(const char * restrict format, ...);
29946 </pre>
29947 Runtime-constraints
29949 format shall not be a null pointer. The %n specifier<sup><a href="#note381"><b>381)</b></a></sup> (modified or not by flags, field
29950 width, or precision) shall not appear in the string pointed to by format. Any argument
29951 to printf_s corresponding to a %s specifier shall not be a null pointer.
29953 If there is a runtime-constraint violation, the printf_s function does not attempt to
29954 produce further output, and it is unspecified to what extent printf_s produced output
29955 before discovering the runtime-constraint violation.
29958 <!--page 608 -->
29961 The printf_s function is equivalent to the printf function except for the explicit
29962 runtime-constraints listed above.
29965 The printf_s function returns the number of characters transmitted, or a negative
29966 value if an output error, encoding error, or runtime-constraint violation occurred.
29969 <p><small><a name="note381" href="#note381">381)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
29970 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
29971 format string was %%n.
29972 </small>
29978 <pre>
29979 #define __STDC_WANT_LIB_EXT1__ 1
29981 int scanf_s(const char * restrict format, ...);
29982 </pre>
29983 Runtime-constraints
29985 format shall not be a null pointer. Any argument indirected though in order to store
29986 converted input shall not be a null pointer.
29988 If there is a runtime-constraint violation, the scanf_s function does not attempt to
29989 perform further input, and it is unspecified to what extent scanf_s performed input
29990 before discovering the runtime-constraint violation.
29993 The scanf_s function is equivalent to fscanf_s with the argument stdin
29994 interposed before the arguments to scanf_s.
29997 The scanf_s function returns the value of the macro EOF if an input failure occurs
29998 before any conversion or if there is a runtime-constraint violation. Otherwise, the
29999 scanf_s function returns the number of input items assigned, which can be fewer than
30000 provided for, or even zero, in the event of an early matching failure.
30006 <pre>
30007 #define __STDC_WANT_LIB_EXT1__ 1
30009 int snprintf_s(char * restrict s, rsize_t n,
30010 const char * restrict format, ...);
30011 </pre>
30012 Runtime-constraints
30014 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30015 than RSIZE_MAX. The %n specifier<sup><a href="#note382"><b>382)</b></a></sup> (modified or not by flags, field width, or
30016 precision) shall not appear in the string pointed to by format. Any argument to
30017 <!--page 609 -->
30018 snprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
30019 error shall occur.
30021 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30022 than zero and less than RSIZE_MAX, then the snprintf_s function sets s[0] to the
30023 null character.
30026 The snprintf_s function is equivalent to the snprintf function except for the
30027 explicit runtime-constraints listed above.
30029 The snprintf_s function, unlike sprintf_s, will truncate the result to fit within the
30030 array pointed to by s.
30033 The snprintf_s function returns the number of characters that would have been
30034 written had n been sufficiently large, not counting the terminating null character, or a
30035 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
30036 output has been completely written if and only if the returned value is nonnegative and
30037 less than n.
30040 <p><small><a name="note382" href="#note382">382)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30041 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30042 format string was %%n.
30043 </small>
30049 <pre>
30050 #define __STDC_WANT_LIB_EXT1__ 1
30052 int sprintf_s(char * restrict s, rsize_t n,
30053 const char * restrict format, ...);
30054 </pre>
30055 Runtime-constraints
30057 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30058 than RSIZE_MAX. The number of characters (including the trailing null) required for the
30059 result to be written to the array pointed to by s shall not be greater than n. The %n
30060 specifier<sup><a href="#note383"><b>383)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
30061 string pointed to by format. Any argument to sprintf_s corresponding to a %s
30062 specifier shall not be a null pointer. No encoding error shall occur.
30066 <!--page 610 -->
30068 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30069 than zero and less than RSIZE_MAX, then the sprintf_s function sets s[0] to the
30070 null character.
30073 The sprintf_s function is equivalent to the sprintf function except for the
30074 parameter n and the explicit runtime-constraints listed above.
30076 The sprintf_s function, unlike snprintf_s, treats a result too big for the array
30077 pointed to by s as a runtime-constraint violation.
30080 If no runtime-constraint violation occurred, the sprintf_s function returns the number
30081 of characters written in the array, not counting the terminating null character. If an
30082 encoding error occurred, sprintf_s returns a negative value. If any other runtime-
30083 constraint violation occurred, sprintf_s returns zero.
30086 <p><small><a name="note383" href="#note383">383)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30087 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30088 format string was %%n.
30089 </small>
30095 <pre>
30096 #define __STDC_WANT_LIB_EXT1__ 1
30098 int sscanf_s(const char * restrict s,
30099 const char * restrict format, ...);
30100 </pre>
30101 Runtime-constraints
30103 Neither s nor format shall be a null pointer. Any argument indirected though in order
30104 to store converted input shall not be a null pointer.
30106 If there is a runtime-constraint violation, the sscanf_s function does not attempt to
30107 perform further input, and it is unspecified to what extent sscanf_s performed input
30108 before discovering the runtime-constraint violation.
30111 The sscanf_s function is equivalent to fscanf_s, except that input is obtained from
30112 a string (specified by the argument s) rather than from a stream. Reaching the end of the
30113 string is equivalent to encountering end-of-file for the fscanf_s function. If copying
30114 takes place between objects that overlap, the objects take on unspecified values.
30117 The sscanf_s function returns the value of the macro EOF if an input failure occurs
30118 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30119 sscanf_s function returns the number of input items assigned, which can be fewer than
30120 provided for, or even zero, in the event of an early matching failure.
30121 <!--page 611 -->
30127 <pre>
30128 #define __STDC_WANT_LIB_EXT1__ 1
30131 int vfprintf_s(FILE * restrict stream,
30132 const char * restrict format,
30133 va_list arg);
30134 </pre>
30135 Runtime-constraints
30137 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note384"><b>384)</b></a></sup> (modified or
30138 not by flags, field width, or precision) shall not appear in the string pointed to by
30139 format. Any argument to vfprintf_s corresponding to a %s specifier shall not be a
30140 null pointer.
30142 If there is a runtime-constraint violation, the vfprintf_s function does not attempt to
30143 produce further output, and it is unspecified to what extent vfprintf_s produced
30144 output before discovering the runtime-constraint violation.
30147 The vfprintf_s function is equivalent to the vfprintf function except for the
30148 explicit runtime-constraints listed above.
30151 The vfprintf_s function returns the number of characters transmitted, or a negative
30152 value if an output error, encoding error, or runtime-constraint violation occurred.
30155 <p><small><a name="note384" href="#note384">384)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30156 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30157 format string was %%n.
30158 </small>
30164 <pre>
30165 #define __STDC_WANT_LIB_EXT1__ 1
30168 int vfscanf_s(FILE * restrict stream,
30169 const char * restrict format,
30170 va_list arg);
30171 </pre>
30176 <!--page 612 -->
30177 Runtime-constraints
30179 Neither stream nor format shall be a null pointer. Any argument indirected though in
30180 order to store converted input shall not be a null pointer.
30182 If there is a runtime-constraint violation, the vfscanf_s function does not attempt to
30183 perform further input, and it is unspecified to what extent vfscanf_s performed input
30184 before discovering the runtime-constraint violation.
30187 The vfscanf_s function is equivalent to fscanf_s, with the variable argument list
30188 replaced by arg, which shall have been initialized by the va_start macro (and
30189 possibly subsequent va_arg calls). The vfscanf_s function does not invoke the
30193 The vfscanf_s function returns the value of the macro EOF if an input failure occurs
30194 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30195 vfscanf_s function returns the number of input items assigned, which can be fewer
30196 than provided for, or even zero, in the event of an early matching failure.
30199 <p><small><a name="note385" href="#note385">385)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
30200 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
30201 indeterminate.
30202 </small>
30208 <pre>
30209 #define __STDC_WANT_LIB_EXT1__ 1
30212 int vprintf_s(const char * restrict format,
30213 va_list arg);
30214 </pre>
30215 Runtime-constraints
30217 format shall not be a null pointer. The %n specifier<sup><a href="#note386"><b>386)</b></a></sup> (modified or not by flags, field
30218 width, or precision) shall not appear in the string pointed to by format. Any argument
30219 to vprintf_s corresponding to a %s specifier shall not be a null pointer.
30221 If there is a runtime-constraint violation, the vprintf_s function does not attempt to
30222 produce further output, and it is unspecified to what extent vprintf_s produced output
30223 before discovering the runtime-constraint violation.
30225 <!--page 613 -->
30228 The vprintf_s function is equivalent to the vprintf function except for the explicit
30229 runtime-constraints listed above.
30232 The vprintf_s function returns the number of characters transmitted, or a negative
30233 value if an output error, encoding error, or runtime-constraint violation occurred.
30236 <p><small><a name="note386" href="#note386">386)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30237 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30238 format string was %%n.
30239 </small>
30245 <pre>
30246 #define __STDC_WANT_LIB_EXT1__ 1
30249 int vscanf_s(const char * restrict format,
30250 va_list arg);
30251 </pre>
30252 Runtime-constraints
30254 format shall not be a null pointer. Any argument indirected though in order to store
30255 converted input shall not be a null pointer.
30257 If there is a runtime-constraint violation, the vscanf_s function does not attempt to
30258 perform further input, and it is unspecified to what extent vscanf_s performed input
30259 before discovering the runtime-constraint violation.
30262 The vscanf_s function is equivalent to scanf_s, with the variable argument list
30263 replaced by arg, which shall have been initialized by the va_start macro (and
30264 possibly subsequent va_arg calls). The vscanf_s function does not invoke the
30268 The vscanf_s function returns the value of the macro EOF if an input failure occurs
30269 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30270 vscanf_s function returns the number of input items assigned, which can be fewer than
30271 provided for, or even zero, in the event of an early matching failure.
30276 <!--page 614 -->
30279 <p><small><a name="note387" href="#note387">387)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
30280 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
30281 indeterminate.
30282 </small>
30288 <pre>
30289 #define __STDC_WANT_LIB_EXT1__ 1
30292 int vsnprintf_s(char * restrict s, rsize_t n,
30293 const char * restrict format,
30294 va_list arg);
30295 </pre>
30296 Runtime-constraints
30298 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30299 than RSIZE_MAX. The %n specifier<sup><a href="#note388"><b>388)</b></a></sup> (modified or not by flags, field width, or
30300 precision) shall not appear in the string pointed to by format. Any argument to
30301 vsnprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
30302 error shall occur.
30304 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30305 than zero and less than RSIZE_MAX, then the vsnprintf_s function sets s[0] to the
30306 null character.
30309 The vsnprintf_s function is equivalent to the vsnprintf function except for the
30310 explicit runtime-constraints listed above.
30312 The vsnprintf_s function, unlike vsprintf_s, will truncate the result to fit within
30313 the array pointed to by s.
30316 The vsnprintf_s function returns the number of characters that would have been
30317 written had n been sufficiently large, not counting the terminating null character, or a
30318 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
30319 output has been completely written if and only if the returned value is nonnegative and
30320 less than n.
30325 <!--page 615 -->
30328 <p><small><a name="note388" href="#note388">388)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30329 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30330 format string was %%n.
30331 </small>
30337 <pre>
30338 #define __STDC_WANT_LIB_EXT1__ 1
30341 int vsprintf_s(char * restrict s, rsize_t n,
30342 const char * restrict format,
30343 va_list arg);
30344 </pre>
30345 Runtime-constraints
30347 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30348 than RSIZE_MAX. The number of characters (including the trailing null) required for the
30349 result to be written to the array pointed to by s shall not be greater than n. The %n
30350 specifier<sup><a href="#note389"><b>389)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
30351 string pointed to by format. Any argument to vsprintf_s corresponding to a %s
30352 specifier shall not be a null pointer. No encoding error shall occur.
30354 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30355 than zero and less than RSIZE_MAX, then the vsprintf_s function sets s[0] to the
30356 null character.
30359 The vsprintf_s function is equivalent to the vsprintf function except for the
30360 parameter n and the explicit runtime-constraints listed above.
30362 The vsprintf_s function, unlike vsnprintf_s, treats a result too big for the array
30363 pointed to by s as a runtime-constraint violation.
30366 If no runtime-constraint violation occurred, the vsprintf_s function returns the
30367 number of characters written in the array, not counting the terminating null character. If
30368 an encoding error occurred, vsprintf_s returns a negative value. If any other
30369 runtime-constraint violation occurred, vsprintf_s returns zero.
30374 <!--page 616 -->
30377 <p><small><a name="note389" href="#note389">389)</a> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
30378 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
30379 format string was %%n.
30380 </small>
30386 <pre>
30387 #define __STDC_WANT_LIB_EXT1__ 1
30390 int vsscanf_s(const char * restrict s,
30391 const char * restrict format,
30392 va_list arg);
30393 </pre>
30394 Runtime-constraints
30396 Neither s nor format shall be a null pointer. Any argument indirected though in order
30397 to store converted input shall not be a null pointer.
30399 If there is a runtime-constraint violation, the vsscanf_s function does not attempt to
30400 perform further input, and it is unspecified to what extent vsscanf_s performed input
30401 before discovering the runtime-constraint violation.
30404 The vsscanf_s function is equivalent to sscanf_s, with the variable argument list
30405 replaced by arg, which shall have been initialized by the va_start macro (and
30406 possibly subsequent va_arg calls). The vsscanf_s function does not invoke the
30410 The vsscanf_s function returns the value of the macro EOF if an input failure occurs
30411 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30412 vscanf_s function returns the number of input items assigned, which can be fewer than
30413 provided for, or even zero, in the event of an early matching failure.
30416 <p><small><a name="note390" href="#note390">390)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
30417 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
30418 indeterminate.
30419 </small>
30428 <pre>
30429 #define __STDC_WANT_LIB_EXT1__ 1
30431 char *gets_s(char *s, rsize_t n);
30432 </pre>
30437 <!--page 617 -->
30438 Runtime-constraints
30440 s shall not be a null pointer. n shall neither be equal to zero nor be greater than
30441 RSIZE_MAX. A new-line character, end-of-file, or read error shall occur within reading
30444 If there is a runtime-constraint violation, s[0] is set to the null character, and characters
30445 are read and discarded from stdin until a new-line character is read, or end-of-file or a
30446 read error occurs.
30449 The gets_s function reads at most one less than the number of characters specified by n
30450 from the stream pointed to by stdin, into the array pointed to by s. No additional
30451 characters are read after a new-line character (which is discarded) or after end-of-file.
30452 The discarded new-line character does not count towards number of characters read. A
30453 null character is written immediately after the last character read into the array.
30455 If end-of-file is encountered and no characters have been read into the array, or if a read
30456 error occurs during the operation, then s[0] is set to the null character, and the other
30457 elements of s take unspecified values.
30460 The fgets function allows properly-written programs to safely process input lines too
30461 long to store in the result array. In general this requires that callers of fgets pay
30462 attention to the presence or absence of a new-line character in the result array. Consider
30463 using fgets (along with any needed processing based on new-line characters) instead of
30464 gets_s.
30467 The gets_s function returns s if successful. If there was a runtime-constraint violation,
30468 or if end-of-file is encountered and no characters have been read into the array, or if a
30469 read error occurs during the operation, then a null pointer is returned.
30474 <!--page 618 -->
30477 <p><small><a name="note391" href="#note391">391)</a> The gets_s function, unlike the historical gets function, makes it a runtime-constraint violation for
30478 a line of input to overflow the buffer to store it. Unlike the fgets function, gets_s maintains a
30479 one-to-one relationship between input lines and successful calls to gets_s. Programs that use gets
30480 expect such a relationship.
30481 </small>
30488 The types are
30489 <pre>
30490 errno_t
30491 </pre>
30492 which is type int; and
30493 <pre>
30494 rsize_t
30495 </pre>
30496 which is the type size_t; and
30497 <pre>
30498 constraint_handler_t
30499 </pre>
30500 which has the following definition
30501 <pre>
30502 typedef void (*constraint_handler_t)(
30503 const char * restrict msg,
30504 void * restrict ptr,
30505 errno_t error);
30506 </pre>
30512 <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>
30515 <pre>
30516 #define __STDC_WANT_LIB_EXT1__ 1
30518 constraint_handler_t set_constraint_handler_s(
30519 constraint_handler_t handler);
30520 </pre>
30523 The set_constraint_handler_s function sets the runtime-constraint handler to
30524 be handler. The runtime-constraint handler is the function to be called when a library
30525 function detects a runtime-constraint violation. Only the most recent handler registered
30526 with set_constraint_handler_s is called when a runtime-constraint violation
30527 occurs.
30529 When the handler is called, it is passed the following arguments in the following order:
30530 <ol>
30531 <li> A pointer to a character string describing the runtime-constraint violation.
30532 <li> A null pointer or a pointer to an implementation defined object.
30533 <li> If the function calling the handler has a return type declared as errno_t, the
30534 return value of the function is passed. Otherwise, a positive value of type
30535 errno_t is passed.
30536 <!--page 619 -->
30537 </ol>
30539 The implementation has a default constraint handler that is used if no calls to the
30540 set_constraint_handler_s function have been made. The behavior of the
30541 default handler is implementation-defined, and it may cause the program to exit or abort.
30543 If the handler argument to set_constraint_handler_s is a null pointer, the
30544 implementation default handler becomes the current constraint handler.
30547 The set_constraint_handler_s function returns a pointer to the previously
30551 <p><small><a name="note392" href="#note392">392)</a> If the previous handler was registered by calling set_constraint_handler_s with a null
30552 pointer argument, a pointer to the implementation default handler is returned (not NULL).
30553 </small>
30559 <pre>
30560 #define __STDC_WANT_LIB_EXT1__ 1
30562 void abort_handler_s(
30563 const char * restrict msg,
30564 void * restrict ptr,
30565 errno_t error);
30566 </pre>
30569 A pointer to the abort_handler_s function shall be a suitable argument to the
30570 set_constraint_handler_s function.
30572 The abort_handler_s function writes a message on the standard error stream in an
30573 implementation-defined format. The message shall include the string pointed to by msg.
30574 The abort_handler_s function then calls the abort function.<sup><a href="#note393"><b>393)</b></a></sup>
30577 The abort_handler_s function does not return to its caller.
30582 <!--page 620 -->
30585 <p><small><a name="note393" href="#note393">393)</a> Many implementations invoke a debugger when the abort function is called.
30586 </small>
30592 <pre>
30593 #define __STDC_WANT_LIB_EXT1__ 1
30595 void ignore_handler_s(
30596 const char * restrict msg,
30597 void * restrict ptr,
30598 errno_t error);
30599 </pre>
30602 A pointer to the ignore_handler_s function shall be a suitable argument to the
30603 set_constraint_handler_s function.
30605 The ignore_handler_s function simply returns to its caller.<sup><a href="#note394"><b>394)</b></a></sup>
30608 The ignore_handler_s function returns no value.
30611 <p><small><a name="note394" href="#note394">394)</a> If the runtime-constraint handler is set to the ignore_handler_s function, any library function in
30612 which a runtime-constraint violation occurs will return to its caller. The caller can determine whether
30613 a runtime-constraint violation occurred based on the library function's specification (usually, the
30614 library function returns a nonzero errno_t).
30615 </small>
30624 <pre>
30625 #define __STDC_WANT_LIB_EXT1__ 1
30627 errno_t getenv_s(size_t * restrict len,
30628 char * restrict value, rsize_t maxsize,
30629 const char * restrict name);
30630 </pre>
30631 Runtime-constraints
30633 name shall not be a null pointer. maxsize shall neither equal zero nor be greater than
30634 RSIZE_MAX. If maxsize is not equal to zero, then value shall not be a null pointer.
30636 If there is a runtime-constraint violation, the integer pointed to by len is set to 0 (if len
30637 is not null), and the environment list is not searched.
30640 The getenv_s function searches an environment list, provided by the host environment,
30641 for a string that matches the string pointed to by name.
30644 <!--page 621 -->
30646 If that name is found then getenv_s performs the following actions. If len is not a
30647 null pointer, the length of the string associated with the matched list member is stored in
30648 the integer pointed to by len. If the length of the associated string is less than maxsize,
30649 then the associated string is copied to the array pointed to by value.
30651 If that name is not found then getenv_s performs the following actions. If len is not
30652 a null pointer, zero is stored in the integer pointed to by len. If maxsize is greater than
30653 zero, then value[0] is set to the null character.
30655 The set of environment names and the method for altering the environment list are
30656 implementation-defined.
30659 The getenv_s function returns zero if the specified name is found and the associated
30660 string was successfully stored in value. Otherwise, a nonzero value is returned.
30665 These utilities make use of a comparison function to search or sort arrays of unspecified
30666 type. Where an argument declared as size_t nmemb specifies the length of the array
30667 for a function, if nmemb has the value zero on a call to that function, then the comparison
30668 function is not called, a search finds no matching element, sorting performs no
30669 rearrangement, and the pointer to the array may be null.
30671 The implementation shall ensure that the second argument of the comparison function
30672 (when called from bsearch_s), or both arguments (when called from qsort_s), are
30673 pointers to elements of the array.<sup><a href="#note395"><b>395)</b></a></sup> The first argument when called from bsearch_s
30674 shall equal key.
30676 The comparison function shall not alter the contents of either the array or search key. The
30677 implementation may reorder elements of the array between calls to the comparison
30678 function, but shall not otherwise alter the contents of any individual element.
30680 When the same objects (consisting of size bytes, irrespective of their current positions
30681 in the array) are passed more than once to the comparison function, the results shall be
30682 consistent with one another. That is, for qsort_s they shall define a total ordering on
30683 the array, and for bsearch_s the same object shall always compare the same way with
30684 the key.
30689 <!--page 622 -->
30691 A sequence point occurs immediately before and immediately after each call to the
30692 comparison function, and also between any call to the comparison function and any
30693 movement of the objects passed as arguments to that call.
30696 <p><small><a name="note395" href="#note395">395)</a> That is, if the value passed is p, then the following expressions are always valid and nonzero:
30698 <pre>
30699 ((char *)p - (char *)base) % size == 0
30700 (char *)p >= (char *)base
30701 (char *)p < (char *)base + nmemb * size
30702 </pre>
30703 </small>
30709 <pre>
30710 #define __STDC_WANT_LIB_EXT1__ 1
30712 void *bsearch_s(const void *key, const void *base,
30713 rsize_t nmemb, rsize_t size,
30714 int (*compar)(const void *k, const void *y,
30715 void *context),
30716 void *context);
30717 </pre>
30718 Runtime-constraints
30720 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
30721 zero, then none of key, base, or compar shall be a null pointer.
30723 If there is a runtime-constraint violation, the bsearch_s function does not search the
30724 array.
30727 The bsearch_s function searches an array of nmemb objects, the initial element of
30728 which is pointed to by base, for an element that matches the object pointed to by key.
30729 The size of each element of the array is specified by size.
30731 The comparison function pointed to by compar is called with three arguments. The first
30732 two point to the key object and to an array element, in that order. The function shall
30733 return an integer less than, equal to, or greater than zero if the key object is considered,
30734 respectively, to be less than, to match, or to be greater than the array element. The array
30735 shall consist of: all the elements that compare less than, all the elements that compare
30736 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note396"><b>396)</b></a></sup>
30737 The third argument to the comparison function is the context argument passed to
30738 bsearch_s. The sole use of context by bsearch_s is to pass it to the comparison
30744 <!--page 623 -->
30747 The bsearch_s function returns a pointer to a matching element of the array, or a null
30748 pointer if no match is found or there is a runtime-constraint violation. If two elements
30749 compare as equal, which element is matched is unspecified.
30752 <p><small><a name="note396" href="#note396">396)</a> In practice, this means that the entire array has been sorted according to the comparison function.
30753 </small>
30754 <p><small><a name="note397" href="#note397">397)</a> The context argument is for the use of the comparison function in performing its duties. For
30755 example, it might specify a collating sequence used by the comparison function.
30756 </small>
30762 <pre>
30763 #define __STDC_WANT_LIB_EXT1__ 1
30765 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
30766 int (*compar)(const void *x, const void *y,
30767 void *context),
30768 void *context);
30769 </pre>
30770 Runtime-constraints
30772 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
30773 zero, then neither base nor compar shall be a null pointer.
30775 If there is a runtime-constraint violation, the qsort_s function does not sort the array.
30778 The qsort_s function sorts an array of nmemb objects, the initial element of which is
30779 pointed to by base. The size of each object is specified by size.
30781 The contents of the array are sorted into ascending order according to a comparison
30782 function pointed to by compar, which is called with three arguments. The first two
30783 point to the objects being compared. The function shall return an integer less than, equal
30784 to, or greater than zero if the first argument is considered to be respectively less than,
30785 equal to, or greater than the second. The third argument to the comparison function is the
30786 context argument passed to qsort_s. The sole use of context by qsort_s is to
30789 If two elements compare as equal, their relative order in the resulting sorted array is
30790 unspecified.
30793 The qsort_s function returns zero if there was no runtime-constraint violation.
30794 Otherwise, a nonzero value is returned.
30799 <!--page 624 -->
30802 <p><small><a name="note398" href="#note398">398)</a> The context argument is for the use of the comparison function in performing its duties. For
30803 example, it might specify a collating sequence used by the comparison function.
30804 </small>
30807 <h5><a name="K.3.6.4" href="#K.3.6.4">K.3.6.4 Multibyte/wide character conversion functions</a></h5>
30809 The behavior of the multibyte character functions is affected by the LC_CTYPE category
30810 of the current locale. For a state-dependent encoding, each function is placed into its
30811 initial conversion state by a call for which its character pointer argument, s, is a null
30812 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
30813 state of the function to be altered as necessary. A call with s as a null pointer causes
30814 these functions to set the int pointed to by their status argument to a nonzero value if
30815 encodings have state dependency, and zero otherwise.<sup><a href="#note399"><b>399)</b></a></sup> Changing the LC_CTYPE
30816 category causes the conversion state of these functions to be indeterminate.
30819 <p><small><a name="note399" href="#note399">399)</a> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
30820 character codes, but are grouped with an adjacent multibyte character.
30821 </small>
30827 <pre>
30828 #define __STDC_WANT_LIB_EXT1__ 1
30830 errno_t wctomb_s(int * restrict status,
30831 char * restrict s,
30832 rsize_t smax,
30833 wchar_t wc);
30834 </pre>
30835 Runtime-constraints
30837 Let n denote the number of bytes needed to represent the multibyte character
30838 corresponding to the wide character given by wc (including any shift sequences).
30840 If s is not a null pointer, then smax shall not be less than n, and smax shall not be
30841 greater than RSIZE_MAX. If s is a null pointer, then smax shall equal zero.
30843 If there is a runtime-constraint violation, wctomb_s does not modify the int pointed to
30844 by status, and if s is not a null pointer, no more than smax elements in the array
30845 pointed to by s will be accessed.
30848 The wctomb_s function determines n and stores the multibyte character representation
30849 of wc in the array whose first element is pointed to by s (if s is not a null pointer). The
30850 number of characters stored never exceeds MB_CUR_MAX or smax. If wc is a null wide
30851 character, a null byte is stored, preceded by any shift sequence needed to restore the
30852 initial shift state, and the function is left in the initial conversion state.
30854 The implementation shall behave as if no library function calls the wctomb_s function.
30859 <!--page 625 -->
30861 If s is a null pointer, the wctomb_s function stores into the int pointed to by status a
30862 nonzero or zero value, if multibyte character encodings, respectively, do or do not have
30863 state-dependent encodings.
30865 If s is not a null pointer, the wctomb_s function stores into the int pointed to by
30866 status either n or -1 if wc, respectively, does or does not correspond to a valid
30867 multibyte character.
30869 In no case will the int pointed to by status be set to a value greater than the
30870 MB_CUR_MAX macro.
30873 The wctomb_s function returns zero if successful, and a nonzero value if there was a
30874 runtime-constraint violation or wc did not correspond to a valid multibyte character.
30877 <h5><a name="K.3.6.5" href="#K.3.6.5">K.3.6.5 Multibyte/wide string conversion functions</a></h5>
30879 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
30880 the current locale.
30886 <pre>
30888 errno_t mbstowcs_s(size_t * restrict retval,
30889 wchar_t * restrict dst, rsize_t dstmax,
30890 const char * restrict src, rsize_t len);
30891 </pre>
30892 Runtime-constraints
30894 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
30895 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
30896 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
30897 zero. If dst is not a null pointer and len is not less than dstmax, then a null character
30898 shall occur within the first dstmax multibyte characters of the array pointed to by src.
30900 If there is a runtime-constraint violation, then mbstowcs_s does the following. If
30901 retval is not a null pointer, then mbstowcs_s sets *retval to (size_t)(-1). If
30902 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
30903 then mbstowcs_s sets dst[0] to the null wide character.
30906 The mbstowcs_s function converts a sequence of multibyte characters that begins in
30907 the initial shift state from the array pointed to by src into a sequence of corresponding
30908 wide characters. If dst is not a null pointer, the converted characters are stored into the
30909 array pointed to by dst. Conversion continues up to and including a terminating null
30910 character, which is also stored. Conversion stops earlier in two cases: when a sequence of
30911 <!--page 626 -->
30912 bytes is encountered that does not form a valid multibyte character, or (if dst is not a
30913 null pointer) when len wide characters have been stored into the array pointed to by
30914 dst.<sup><a href="#note400"><b>400)</b></a></sup> If dst is not a null pointer and no null wide character was stored into the array
30915 pointed to by dst, then dst[len] is set to the null wide character. Each conversion
30916 takes place as if by a call to the mbrtowc function.
30918 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
30919 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
30920 the mbstowcs_s function stores the value (size_t)(-1) into *retval.
30921 Otherwise, the mbstowcs_s function stores into *retval the number of multibyte
30922 characters successfully converted, not including the terminating null character (if any).
30924 All elements following the terminating null wide character (if any) written by
30925 mbstowcs_s in the array of dstmax wide characters pointed to by dst take
30928 If copying takes place between objects that overlap, the objects take on unspecified
30929 values.
30932 The mbstowcs_s function returns zero if no runtime-constraint violation and no
30933 encoding error occurred. Otherwise, a nonzero value is returned.
30936 <p><small><a name="note400" href="#note400">400)</a> Thus, the value of len is ignored if dst is a null pointer.
30937 </small>
30938 <p><small><a name="note401" href="#note401">401)</a> This allows an implementation to attempt converting the multibyte string before discovering a
30939 terminating null character did not occur where required.
30940 </small>
30946 <pre>
30948 errno_t wcstombs_s(size_t * restrict retval,
30949 char * restrict dst, rsize_t dstmax,
30950 const wchar_t * restrict src, rsize_t len);
30951 </pre>
30952 Runtime-constraints
30954 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
30955 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
30956 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
30957 zero. If dst is not a null pointer and len is not less than dstmax, then the conversion
30958 shall have been stopped (see below) because a terminating null wide character was
30959 reached or because an encoding error occurred.
30964 <!--page 627 -->
30966 If there is a runtime-constraint violation, then wcstombs_s does the following. If
30967 retval is not a null pointer, then wcstombs_s sets *retval to (size_t)(-1). If
30968 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
30969 then wcstombs_s sets dst[0] to the null character.
30972 The wcstombs_s function converts a sequence of wide characters from the array
30973 pointed to by src into a sequence of corresponding multibyte characters that begins in
30974 the initial shift state. If dst is not a null pointer, the converted characters are then stored
30975 into the array pointed to by dst. Conversion continues up to and including a terminating
30976 null wide character, which is also stored. Conversion stops earlier in two cases:
30977 <ul>
30978 <li> when a wide character is reached that does not correspond to a valid multibyte
30979 character;
30980 <li> (if dst is not a null pointer) when the next multibyte character would exceed the
30981 limit of n total bytes to be stored into the array pointed to by dst. If the wide
30982 character being converted is the null wide character, then n is the lesser of len or
30983 dstmax. Otherwise, n is the lesser of len or dstmax-1.
30984 </ul>
30985 If the conversion stops without converting a null wide character and dst is not a null
30986 pointer, then a null character is stored into the array pointed to by dst immediately
30987 following any multibyte characters already stored. Each conversion takes place as if by a
30990 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
30991 wide character that does not correspond to a valid multibyte character, an encoding error
30992 occurs: the wcstombs_s function stores the value (size_t)(-1) into *retval.
30993 Otherwise, the wcstombs_s function stores into *retval the number of bytes in the
30994 resulting multibyte character sequence, not including the terminating null character (if
30995 any).
30997 All elements following the terminating null character (if any) written by wcstombs_s
30998 in the array of dstmax elements pointed to by dst take unspecified values when
31001 If copying takes place between objects that overlap, the objects take on unspecified
31002 values.
31005 <!--page 628 -->
31008 The wcstombs_s function returns zero if no runtime-constraint violation and no
31009 encoding error occurred. Otherwise, a nonzero value is returned.
31012 <p><small><a name="note402" href="#note402">402)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
31013 include those necessary to reach the initial shift state immediately before the null byte. However, if
31014 the conversion stops before a terminating null wide character has been reached, the result will be null
31015 terminated, but might not end in the initial shift state.
31016 </small>
31017 <p><small><a name="note403" href="#note403">403)</a> When len is not less than dstmax, the implementation might fill the array before discovering a
31018 runtime-constraint violation.
31019 </small>
31026 The types are
31027 <pre>
31028 errno_t
31029 </pre>
31030 which is type int; and
31031 <pre>
31032 rsize_t
31033 </pre>
31034 which is the type size_t.
31043 <pre>
31044 #define __STDC_WANT_LIB_EXT1__ 1
31046 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
31047 const void * restrict s2, rsize_t n);
31048 </pre>
31049 Runtime-constraints
31051 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31052 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
31053 objects that overlap.
31055 If there is a runtime-constraint violation, the memcpy_s function stores zeros in the first
31056 s1max characters of the object pointed to by s1 if s1 is not a null pointer and s1max is
31057 not greater than RSIZE_MAX.
31060 The memcpy_s function copies n characters from the object pointed to by s2 into the
31061 object pointed to by s1.
31064 The memcpy_s function returns zero if there was no runtime-constraint violation.
31065 Otherwise, a nonzero value is returned.
31066 <!--page 629 -->
31072 <pre>
31073 #define __STDC_WANT_LIB_EXT1__ 1
31075 errno_t memmove_s(void *s1, rsize_t s1max,
31076 const void *s2, rsize_t n);
31077 </pre>
31078 Runtime-constraints
31080 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31081 RSIZE_MAX. n shall not be greater than s1max.
31083 If there is a runtime-constraint violation, the memmove_s function stores zeros in the
31084 first s1max characters of the object pointed to by s1 if s1 is not a null pointer and
31085 s1max is not greater than RSIZE_MAX.
31088 The memmove_s function copies n characters from the object pointed to by s2 into the
31089 object pointed to by s1. This copying takes place as if the n characters from the object
31090 pointed to by s2 are first copied into a temporary array of n characters that does not
31091 overlap the objects pointed to by s1 or s2, and then the n characters from the temporary
31092 array are copied into the object pointed to by s1.
31095 The memmove_s function returns zero if there was no runtime-constraint violation.
31096 Otherwise, a nonzero value is returned.
31102 <pre>
31103 #define __STDC_WANT_LIB_EXT1__ 1
31105 errno_t strcpy_s(char * restrict s1,
31106 rsize_t s1max,
31107 const char * restrict s2);
31108 </pre>
31109 Runtime-constraints
31111 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
31112 s1max shall not equal zero. s1max shall be greater than strnlen_s(s2, s1max).
31113 Copying shall not take place between objects that overlap.
31115 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31116 greater than zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the
31117 null character.
31118 <!--page 630 -->
31121 The strcpy_s function copies the string pointed to by s2 (including the terminating
31122 null character) into the array pointed to by s1.
31124 All elements following the terminating null character (if any) written by strcpy_s in
31125 the array of s1max characters pointed to by s1 take unspecified values when
31129 The strcpy_s function returns zero<sup><a href="#note405"><b>405)</b></a></sup> if there was no runtime-constraint violation.
31130 Otherwise, a nonzero value is returned.
31133 <p><small><a name="note404" href="#note404">404)</a> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
31134 any of those characters are null. Such an approach might write a character to every element of s1
31135 before discovering that the first element should be set to the null character.
31136 </small>
31137 <p><small><a name="note405" href="#note405">405)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 fit
31138 within the array pointed to by s1 and that the result in s1 is null terminated.
31139 </small>
31145 <pre>
31146 #define __STDC_WANT_LIB_EXT1__ 1
31148 errno_t strncpy_s(char * restrict s1,
31149 rsize_t s1max,
31150 const char * restrict s2,
31151 rsize_t n);
31152 </pre>
31153 Runtime-constraints
31155 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31156 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
31157 shall be greater than strnlen_s(s2, s1max). Copying shall not take place between
31158 objects that overlap.
31160 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31161 greater than zero and not greater than RSIZE_MAX, then strncpy_s sets s1[0] to the
31162 null character.
31165 The strncpy_s function copies not more than n successive characters (characters that
31166 follow a null character are not copied) from the array pointed to by s2 to the array
31167 pointed to by s1. If no null character was copied from s2, then s1[n] is set to a null
31168 character.
31171 <!--page 631 -->
31173 All elements following the terminating null character (if any) written by strncpy_s in
31174 the array of s1max characters pointed to by s1 take unspecified values when
31178 The strncpy_s function returns zero<sup><a href="#note407"><b>407)</b></a></sup> if there was no runtime-constraint violation.
31179 Otherwise, a nonzero value is returned.
31181 EXAMPLE 1 The strncpy_s function can be used to copy a string without the danger that the result
31182 will not be null terminated or that characters will be written past the end of the destination array.
31183 <pre>
31184 #define __STDC_WANT_LIB_EXT1__ 1
31186 /* ... */
31188 char src2[7] = {'g', 'o', 'o', 'd', 'b', 'y', 'e'};
31190 int r1, r2, r3;
31194 </pre>
31195 The first call will assign to r1 the value zero and to dst1 the sequence hello\0.
31196 The second call will assign to r2 a nonzero value and to dst2 the sequence \0.
31197 The third call will assign to r3 the value zero and to dst3 the sequence good\0.
31201 <p><small><a name="note406" href="#note406">406)</a> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
31202 any of those characters are null. Such an approach might write a character to every element of s1
31203 before discovering that the first element should be set to the null character.
31204 </small>
31205 <p><small><a name="note407" href="#note407">407)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 fit
31206 within the array pointed to by s1 and that the result in s1 is null terminated.
31207 </small>
31216 <pre>
31217 #define __STDC_WANT_LIB_EXT1__ 1
31219 errno_t strcat_s(char * restrict s1,
31220 rsize_t s1max,
31221 const char * restrict s2);
31222 </pre>
31223 Runtime-constraints
31225 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
31226 strcat_s.
31231 <!--page 632 -->
31233 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
31234 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note408"><b>408)</b></a></sup> m shall be greater than
31235 strnlen_s(s2, m). Copying shall not take place between objects that overlap.
31237 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31238 greater than zero and not greater than RSIZE_MAX, then strcat_s sets s1[0] to the
31239 null character.
31242 The strcat_s function appends a copy of the string pointed to by s2 (including the
31243 terminating null character) to the end of the string pointed to by s1. The initial character
31244 from s2 overwrites the null character at the end of s1.
31246 All elements following the terminating null character (if any) written by strcat_s in
31247 the array of s1max characters pointed to by s1 take unspecified values when
31251 The strcat_s function returns zero<sup><a href="#note410"><b>410)</b></a></sup> if there was no runtime-constraint violation.
31252 Otherwise, a nonzero value is returned.
31255 <p><small><a name="note408" href="#note408">408)</a> Zero means that s1 was not null terminated upon entry to strcat_s.
31256 </small>
31257 <p><small><a name="note409" href="#note409">409)</a> This allows an implementation to append characters from s2 to s1 while simultaneously checking if
31258 any of those characters are null. Such an approach might write a character to every element of s1
31259 before discovering that the first element should be set to the null character.
31260 </small>
31261 <p><small><a name="note410" href="#note410">410)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 were
31262 appended to the string pointed to by s1 and that the result in s1 is null terminated.
31263 </small>
31269 <pre>
31270 #define __STDC_WANT_LIB_EXT1__ 1
31272 errno_t strncat_s(char * restrict s1,
31273 rsize_t s1max,
31274 const char * restrict s2,
31275 rsize_t n);
31276 </pre>
31277 Runtime-constraints
31279 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
31280 strncat_s.
31282 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31283 RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.<sup><a href="#note411"><b>411)</b></a></sup> If n is not less
31286 <!--page 633 -->
31287 than m, then m shall be greater than strnlen_s(s2, m). Copying shall not take
31288 place between objects that overlap.
31290 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31291 greater than zero and not greater than RSIZE_MAX, then strncat_s sets s1[0] to the
31292 null character.
31295 The strncat_s function appends not more than n successive characters (characters
31296 that follow a null character are not copied) from the array pointed to by s2 to the end of
31297 the string pointed to by s1. The initial character from s2 overwrites the null character at
31298 the end of s1. If no null character was copied from s2, then s1[s1max-m+n] is set to
31299 a null character.
31301 All elements following the terminating null character (if any) written by strncat_s in
31302 the array of s1max characters pointed to by s1 take unspecified values when
31306 The strncat_s function returns zero<sup><a href="#note413"><b>413)</b></a></sup> if there was no runtime-constraint violation.
31307 Otherwise, a nonzero value is returned.
31309 EXAMPLE 1 The strncat_s function can be used to copy a string without the danger that the result
31310 will not be null terminated or that characters will be written past the end of the destination array.
31311 <pre>
31312 #define __STDC_WANT_LIB_EXT1__ 1
31314 /* ... */
31320 int r1, r2, r3, r4;
31325 </pre>
31326 After the first call r1 will have the value zero and s1 will contain the sequence goodbye\0.
31330 <!--page 634 -->
31331 After the second call r2 will have the value zero and s2 will contain the sequence hello\0.
31332 After the third call r3 will have a nonzero value and s3 will contain the sequence \0.
31333 After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0.
31337 <p><small><a name="note411" href="#note411">411)</a> Zero means that s1 was not null terminated upon entry to strncat_s.
31338 </small>
31339 <p><small><a name="note412" href="#note412">412)</a> This allows an implementation to append characters from s2 to s1 while simultaneously checking if
31340 any of those characters are null. Such an approach might write a character to every element of s1
31341 before discovering that the first element should be set to the null character.
31342 </small>
31343 <p><small><a name="note413" href="#note413">413)</a> A zero return value implies that all of the requested characters from the string pointed to by s2 were
31344 appended to the string pointed to by s1 and that the result in s1 is null terminated.
31345 </small>
31354 <pre>
31355 #define __STDC_WANT_LIB_EXT1__ 1
31357 char *strtok_s(char * restrict s1,
31358 rsize_t * restrict s1max,
31359 const char * restrict s2,
31360 char ** restrict ptr);
31361 </pre>
31362 Runtime-constraints
31364 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
31365 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
31366 The end of the token found shall occur within the first *s1max characters of s1 for the
31367 first call, and shall occur within the first *s1max characters of where searching resumes
31368 on subsequent calls.
31370 If there is a runtime-constraint violation, the strtok_s function does not indirect
31371 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
31374 A sequence of calls to the strtok_s function breaks the string pointed to by s1 into a
31375 sequence of tokens, each of which is delimited by a character from the string pointed to
31376 by s2. The fourth argument points to a caller-provided char pointer into which the
31377 strtok_s function stores information necessary for it to continue scanning the same
31378 string.
31380 The first call in a sequence has a non-null first argument and s1max points to an object
31381 whose value is the number of elements in the character array pointed to by the first
31382 argument. The first call stores an initial value in the object pointed to by ptr and
31383 updates the value pointed to by s1max to reflect the number of elements that remain in
31384 relation to ptr. Subsequent calls in the sequence have a null first argument and the
31385 objects pointed to by s1max and ptr are required to have the values stored by the
31386 previous call in the sequence, which are then updated. The separator string pointed to by
31387 s2 may be different from call to call.
31389 The first call in the sequence searches the string pointed to by s1 for the first character
31390 that is not contained in the current separator string pointed to by s2. If no such character
31391 is found, then there are no tokens in the string pointed to by s1 and the strtok_s
31392 function returns a null pointer. If such a character is found, it is the start of the first token.
31393 <!--page 635 -->
31395 The strtok_s function then searches from there for the first character in s1 that is
31396 contained in the current separator string. If no such character is found, the current token
31397 extends to the end of the string pointed to by s1, and subsequent searches in the same
31398 string for a token return a null pointer. If such a character is found, it is overwritten by a
31399 null character, which terminates the current token.
31401 In all cases, the strtok_s function stores sufficient information in the pointer pointed
31402 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
31403 value for ptr, shall start searching just past the element overwritten by a null character
31404 (if any).
31407 The strtok_s function returns a pointer to the first character of a token, or a null
31408 pointer if there is no token or there is a runtime-constraint violation.
31410 EXAMPLE
31411 <pre>
31412 #define __STDC_WANT_LIB_EXT1__ 1
31414 static char str1[] = "?a???b,,,#c";
31415 static char str2[] = "\t \t";
31416 char *t, *ptr1, *ptr2;
31417 rsize_t max1 = sizeof(str1);
31418 rsize_t max2 = sizeof(str2);
31424 </pre>
31434 <pre>
31435 #define __STDC_WANT_LIB_EXT1__ 1
31437 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
31438 </pre>
31439 Runtime-constraints
31441 s shall not be a null pointer. Neither smax nor n shall be greater than RSIZE_MAX. n
31442 shall not be greater than smax.
31444 If there is a runtime-constraint violation, then if s is not a null pointer and smax is not
31445 greater than RSIZE_MAX, the memset_s function stores the value of c (converted to an
31446 unsigned char) into each of the first smax characters of the object pointed to by s.
31447 <!--page 636 -->
31450 The memset_s function copies the value of c (converted to an unsigned char) into
31451 each of the first n characters of the object pointed to by s. Unlike memset, any call to
31452 the memset_s function shall be evaluated strictly according to the rules of the abstract
31453 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
31454 assume that the memory indicated by s and n may be accessible in the future and thus
31455 must contain the values indicated by c.
31458 The memset_s function returns zero if there was no runtime-constraint violation.
31459 Otherwise, a nonzero value is returned.
31465 <pre>
31466 #define __STDC_WANT_LIB_EXT1__ 1
31468 errno_t strerror_s(char *s, rsize_t maxsize,
31469 errno_t errnum);
31470 </pre>
31471 Runtime-constraints
31473 s shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX.
31474 maxsize shall not equal zero.
31476 If there is a runtime-constraint violation, then the array (if any) pointed to by s is not
31477 modified.
31480 The strerror_s function maps the number in errnum to a locale-specific message
31481 string. Typically, the values for errnum come from errno, but strerror_s shall
31482 map any value of type int to a message.
31484 If the length of the desired string is less than maxsize, then the string is copied to the
31485 array pointed to by s.
31487 Otherwise, if maxsize is greater than zero, then maxsize-1 characters are copied
31488 from the string to the array pointed to by s and then s[maxsize-1] is set to the null
31493 The strerror_s function returns zero if the length of the desired string was less than
31494 maxsize and there was no runtime-constraint violation. Otherwise, the strerror_s
31495 function returns a nonzero value.
31496 <!--page 637 -->
31502 <pre>
31503 #define __STDC_WANT_LIB_EXT1__ 1
31505 size_t strerrorlen_s(errno_t errnum);
31506 </pre>
31509 The strerrorlen_s function calculates the length of the (untruncated) locale-specific
31510 message string that the strerror_s function maps to errnum.
31513 The strerrorlen_s function returns the number of characters (not including the null
31514 character) in the full message string.
31520 <pre>
31521 #define __STDC_WANT_LIB_EXT1__ 1
31523 size_t strnlen_s(const char *s, size_t maxsize);
31524 </pre>
31527 The strnlen_s function computes the length of the string pointed to by s.
31530 If s is a null pointer,<sup><a href="#note414"><b>414)</b></a></sup> then the strnlen_s function returns zero.
31532 Otherwise, the strnlen_s function returns the number of characters that precede the
31533 terminating null character. If there is no null character in the first maxsize characters of
31534 s then strnlen_s returns maxsize. At most the first maxsize characters of s shall
31535 be accessed by strnlen_s.
31540 <!--page 638 -->
31543 <p><small><a name="note414" href="#note414">414)</a> Note that the strnlen_s function has no runtime-constraints. This lack of runtime-constraints
31544 along with the values returned for a null pointer or an unterminated string argument make
31545 strnlen_s useful in algorithms that gracefully handle such exceptional data.
31546 </small>
31553 The types are
31554 <pre>
31555 errno_t
31556 </pre>
31557 which is type int; and
31558 <pre>
31559 rsize_t
31560 </pre>
31561 which is the type size_t.
31566 A broken-down time is normalized if the values of the members of the tm structure are in
31570 <p><small><a name="note415" href="#note415">415)</a> The normal ranges are defined in <a href="#7.26.1">7.26.1</a>.
31571 </small>
31576 Like the strftime function, the asctime_s and ctime_s functions do not return a
31577 pointer to a static object, and other library functions are permitted to call them.
31583 <pre>
31584 #define __STDC_WANT_LIB_EXT1__ 1
31586 errno_t asctime_s(char *s, rsize_t maxsize,
31587 const struct tm *timeptr);
31588 </pre>
31589 Runtime-constraints
31591 Neither s nor timeptr shall be a null pointer. maxsize shall not be less than 26 and
31592 shall not be greater than RSIZE_MAX. The broken-down time pointed to by timeptr
31593 shall be normalized. The calendar year represented by the broken-down time pointed to
31594 by timeptr shall not be less than calendar year 0 and shall not be greater than calendar
31595 year 9999.
31597 If there is a runtime-constraint violation, there is no attempt to convert the time, and
31598 s[0] is set to a null character if s is not a null pointer and maxsize is not zero and is
31599 not greater than RSIZE_MAX.
31602 The asctime_s function converts the normalized broken-down time in the structure
31603 pointed to by timeptr into a 26 character (including the null character) string in the
31606 <!--page 639 -->
31607 form
31608 <pre>
31610 </pre>
31611 The fields making up this string are (in order):
31612 <ol>
31614 following three character weekday names: Sun, Mon, Tue, Wed, Thu, Fri, and Sat.
31615 <li> The character space.
31617 three character month names: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct,
31618 Nov, and Dec.
31619 <li> The character space.
31621 "%2d".
31622 <li> The character space.
31624 "%.2d".
31625 <li> The character colon.
31627 "%.2d".
31628 <li> The character colon.
31630 "%.2d".
31631 <li> The character space.
31633 format "%4d".
31634 <li> The character new line.
31635 <li> The null character.
31636 </ol>
31638 The strftime function allows more flexible formatting and supports locale-specific
31639 behavior. If you do not require the exact form of the result string produced by the
31640 asctime_s function, consider using the strftime function instead.
31643 The asctime_s function returns zero if the time was successfully converted and stored
31644 into the array pointed to by s. Otherwise, it returns a nonzero value.
31645 <!--page 640 -->
31651 <pre>
31652 #define __STDC_WANT_LIB_EXT1__ 1
31654 errno_t ctime_s(char *s, rsize_t maxsize,
31655 const time_t *timer);
31656 </pre>
31657 Runtime-constraints
31659 Neither s nor timer shall be a null pointer. maxsize shall not be less than 26 and
31660 shall not be greater than RSIZE_MAX.
31662 If there is a runtime-constraint violation, s[0] is set to a null character if s is not a null
31663 pointer and maxsize is not equal zero and is not greater than RSIZE_MAX.
31666 The ctime_s function converts the calendar time pointed to by timer to local time in
31667 the form of a string. It is equivalent to
31668 <pre>
31669 asctime_s(s, maxsize, localtime_s(timer))
31670 </pre>
31672 The strftime function allows more flexible formatting and supports locale-specific
31673 behavior. If you do not require the exact form of the result string produced by the
31674 ctime_s function, consider using the strftime function instead.
31677 The ctime_s function returns zero if the time was successfully converted and stored
31678 into the array pointed to by s. Otherwise, it returns a nonzero value.
31684 <pre>
31685 #define __STDC_WANT_LIB_EXT1__ 1
31687 struct tm *gmtime_s(const time_t * restrict timer,
31688 struct tm * restrict result);
31689 </pre>
31690 Runtime-constraints
31692 Neither timer nor result shall be a null pointer.
31694 If there is a runtime-constraint violation, there is no attempt to convert the time.
31697 The gmtime_s function converts the calendar time pointed to by timer into a broken-
31698 down time, expressed as UTC. The broken-down time is stored in the structure pointed
31699 <!--page 641 -->
31700 to by result.
31703 The gmtime_s function returns result, or a null pointer if the specified time cannot
31704 be converted to UTC or there is a runtime-constraint violation.
31710 <pre>
31711 #define __STDC_WANT_LIB_EXT1__ 1
31713 struct tm *localtime_s(const time_t * restrict timer,
31714 struct tm * restrict result);
31715 </pre>
31716 Runtime-constraints
31718 Neither timer nor result shall be a null pointer.
31720 If there is a runtime-constraint violation, there is no attempt to convert the time.
31723 The localtime_s function converts the calendar time pointed to by timer into a
31724 broken-down time, expressed as local time. The broken-down time is stored in the
31725 structure pointed to by result.
31728 The localtime_s function returns result, or a null pointer if the specified time
31729 cannot be converted to local time or there is a runtime-constraint violation.
31732 <h4><a name="K.3.9" href="#K.3.9">K.3.9 Extended multibyte and wide character utilities <wchar.h></a></h4>
31736 The types are
31737 <pre>
31738 errno_t
31739 </pre>
31740 which is type int; and
31741 <pre>
31742 rsize_t
31743 </pre>
31744 which is the type size_t.
31746 Unless explicitly stated otherwise, if the execution of a function described in this
31747 subclause causes copying to take place between objects that overlap, the objects take on
31748 unspecified values.
31749 <!--page 642 -->
31752 <h5><a name="K.3.9.1" href="#K.3.9.1">K.3.9.1 Formatted wide character input/output functions</a></h5>
31758 <pre>
31759 #define __STDC_WANT_LIB_EXT1__ 1
31761 int fwprintf_s(FILE * restrict stream,
31762 const wchar_t * restrict format, ...);
31763 </pre>
31764 Runtime-constraints
31766 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note416"><b>416)</b></a></sup> (modified or
31767 not by flags, field width, or precision) shall not appear in the wide string pointed to by
31768 format. Any argument to fwprintf_s corresponding to a %s specifier shall not be a
31769 null pointer.
31771 If there is a runtime-constraint violation, the fwprintf_s function does not attempt to
31772 produce further output, and it is unspecified to what extent fwprintf_s produced
31773 output before discovering the runtime-constraint violation.
31776 The fwprintf_s function is equivalent to the fwprintf function except for the
31777 explicit runtime-constraints listed above.
31780 The fwprintf_s function returns the number of wide characters transmitted, or a
31781 negative value if an output error, encoding error, or runtime-constraint violation occurred.
31784 <p><small><a name="note416" href="#note416">416)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
31785 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
31786 example, if the entire format string was L"%%n".
31787 </small>
31793 <pre>
31794 #define __STDC_WANT_LIB_EXT1__ 1
31797 int fwscanf_s(FILE * restrict stream,
31798 const wchar_t * restrict format, ...);
31799 </pre>
31800 Runtime-constraints
31802 Neither stream nor format shall be a null pointer. Any argument indirected though in
31803 order to store converted input shall not be a null pointer.
31806 <!--page 643 -->
31808 If there is a runtime-constraint violation, the fwscanf_s function does not attempt to
31809 perform further input, and it is unspecified to what extent fwscanf_s performed input
31810 before discovering the runtime-constraint violation.
31813 The fwscanf_s function is equivalent to fwscanf except that the c, s, and [
31814 conversion specifiers apply to a pair of arguments (unless assignment suppression is
31815 indicated by a *). The first of these arguments is the same as for fwscanf. That
31816 argument is immediately followed in the argument list by the second argument, which has
31817 type size_t and gives the number of elements in the array pointed to by the first
31818 argument of the pair. If the first argument points to a scalar object, it is considered to be
31821 A matching failure occurs if the number of elements in a receiving object is insufficient to
31822 hold the converted input (including any trailing null character).
31825 The fwscanf_s function returns the value of the macro EOF if an input failure occurs
31826 before any conversion or if there is a runtime-constraint violation. Otherwise, the
31827 fwscanf_s function returns the number of input items assigned, which can be fewer
31828 than provided for, or even zero, in the event of an early matching failure.
31831 <p><small><a name="note417" href="#note417">417)</a> If the format is known at translation time, an implementation may issue a diagnostic for any argument
31832 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
31833 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
31834 the format is not known at translation time. For example, an implementation may issue a diagnostic
31835 for each argument after format that has of type pointer to one of char, signed char,
31836 unsigned char, or void that is not followed by an argument of a type compatible with
31837 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
31838 using the hh length modifier, a length argument must follow the pointer argument. Another useful
31839 diagnostic could flag any non-pointer argument following format that did not have a type
31840 compatible with rsize_t.
31841 </small>
31847 <pre>
31848 #define __STDC_WANT_LIB_EXT1__ 1
31850 int snwprintf_s(wchar_t * restrict s,
31851 rsize_t n,
31852 const wchar_t * restrict format, ...);
31853 </pre>
31854 Runtime-constraints
31856 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
31857 than RSIZE_MAX. The %n specifier<sup><a href="#note418"><b>418)</b></a></sup> (modified or not by flags, field width, or
31859 <!--page 644 -->
31860 precision) shall not appear in the wide string pointed to by format. Any argument to
31861 snwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
31862 error shall occur.
31864 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
31865 than zero and less than RSIZE_MAX, then the snwprintf_s function sets s[0] to the
31866 null wide character.
31869 The snwprintf_s function is equivalent to the swprintf function except for the
31870 explicit runtime-constraints listed above.
31872 The snwprintf_s function, unlike swprintf_s, will truncate the result to fit within
31873 the array pointed to by s.
31876 The snwprintf_s function returns the number of wide characters that would have
31877 been written had n been sufficiently large, not counting the terminating wide null
31878 character, or a negative value if a runtime-constraint violation occurred. Thus, the null-
31879 terminated output has been completely written if and only if the returned value is
31880 nonnegative and less than n.
31883 <p><small><a name="note418" href="#note418">418)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
31884 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
31885 example, if the entire format string was L"%%n".
31886 </small>
31892 <pre>
31893 #define __STDC_WANT_LIB_EXT1__ 1
31895 int swprintf_s(wchar_t * restrict s, rsize_t n,
31896 const wchar_t * restrict format, ...);
31897 </pre>
31898 Runtime-constraints
31900 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
31901 than RSIZE_MAX. The number of wide characters (including the trailing null) required
31902 for the result to be written to the array pointed to by s shall not be greater than n. The %n
31903 specifier<sup><a href="#note419"><b>419)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
31904 wide string pointed to by format. Any argument to swprintf_s corresponding to a
31905 %s specifier shall not be a null pointer. No encoding error shall occur.
31908 <!--page 645 -->
31910 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
31911 than zero and less than RSIZE_MAX, then the swprintf_s function sets s[0] to the
31912 null wide character.
31915 The swprintf_s function is equivalent to the swprintf function except for the
31916 explicit runtime-constraints listed above.
31918 The swprintf_s function, unlike snwprintf_s, treats a result too big for the array
31919 pointed to by s as a runtime-constraint violation.
31922 If no runtime-constraint violation occurred, the swprintf_s function returns the
31923 number of wide characters written in the array, not counting the terminating null wide
31924 character. If an encoding error occurred or if n or more wide characters are requested to
31925 be written, swprintf_s returns a negative value. If any other runtime-constraint
31926 violation occurred, swprintf_s returns zero.
31929 <p><small><a name="note419" href="#note419">419)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
31930 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
31931 example, if the entire format string was L"%%n".
31932 </small>
31938 <pre>
31939 #define __STDC_WANT_LIB_EXT1__ 1
31941 int swscanf_s(const wchar_t * restrict s,
31942 const wchar_t * restrict format, ...);
31943 </pre>
31944 Runtime-constraints
31946 Neither s nor format shall be a null pointer. Any argument indirected though in order
31947 to store converted input shall not be a null pointer.
31949 If there is a runtime-constraint violation, the swscanf_s function does not attempt to
31950 perform further input, and it is unspecified to what extent swscanf_s performed input
31951 before discovering the runtime-constraint violation.
31954 The swscanf_s function is equivalent to fwscanf_s, except that the argument s
31955 specifies a wide string from which the input is to be obtained, rather than from a stream.
31956 Reaching the end of the wide string is equivalent to encountering end-of-file for the
31957 fwscanf_s function.
31960 The swscanf_s function returns the value of the macro EOF if an input failure occurs
31961 before any conversion or if there is a runtime-constraint violation. Otherwise, the
31962 swscanf_s function returns the number of input items assigned, which can be fewer
31963 than provided for, or even zero, in the event of an early matching failure.
31964 <!--page 646 -->
31970 <pre>
31971 #define __STDC_WANT_LIB_EXT1__ 1
31975 int vfwprintf_s(FILE * restrict stream,
31976 const wchar_t * restrict format,
31977 va_list arg);
31978 </pre>
31979 Runtime-constraints
31981 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note420"><b>420)</b></a></sup> (modified or
31982 not by flags, field width, or precision) shall not appear in the wide string pointed to by
31983 format. Any argument to vfwprintf_s corresponding to a %s specifier shall not be
31984 a null pointer.
31986 If there is a runtime-constraint violation, the vfwprintf_s function does not attempt
31987 to produce further output, and it is unspecified to what extent vfwprintf_s produced
31988 output before discovering the runtime-constraint violation.
31991 The vfwprintf_s function is equivalent to the vfwprintf function except for the
31992 explicit runtime-constraints listed above.
31995 The vfwprintf_s function returns the number of wide characters transmitted, or a
31996 negative value if an output error, encoding error, or runtime-constraint violation occurred.
31999 <p><small><a name="note420" href="#note420">420)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32000 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32001 example, if the entire format string was L"%%n".
32002 </small>
32008 <pre>
32009 #define __STDC_WANT_LIB_EXT1__ 1
32013 int vfwscanf_s(FILE * restrict stream,
32014 const wchar_t * restrict format, va_list arg);
32015 </pre>
32019 <!--page 647 -->
32020 Runtime-constraints
32022 Neither stream nor format shall be a null pointer. Any argument indirected though in
32023 order to store converted input shall not be a null pointer.
32025 If there is a runtime-constraint violation, the vfwscanf_s function does not attempt to
32026 perform further input, and it is unspecified to what extent vfwscanf_s performed input
32027 before discovering the runtime-constraint violation.
32030 The vfwscanf_s function is equivalent to fwscanf_s, with the variable argument
32031 list replaced by arg, which shall have been initialized by the va_start macro (and
32032 possibly subsequent va_arg calls). The vfwscanf_s function does not invoke the
32036 The vfwscanf_s function returns the value of the macro EOF if an input failure occurs
32037 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32038 vfwscanf_s function returns the number of input items assigned, which can be fewer
32039 than provided for, or even zero, in the event of an early matching failure.
32042 <p><small><a name="note421" href="#note421">421)</a> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
32043 value of arg after the return is indeterminate.
32044 </small>
32050 <pre>
32051 #define __STDC_WANT_LIB_EXT1__ 1
32054 int vsnwprintf_s(wchar_t * restrict s,
32055 rsize_t n,
32056 const wchar_t * restrict format,
32057 va_list arg);
32058 </pre>
32059 Runtime-constraints
32061 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
32062 than RSIZE_MAX. The %n specifier<sup><a href="#note422"><b>422)</b></a></sup> (modified or not by flags, field width, or
32063 precision) shall not appear in the wide string pointed to by format. Any argument to
32064 vsnwprintf_s corresponding to a %s specifier shall not be a null pointer. No
32065 encoding error shall occur.
32067 <!--page 648 -->
32069 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
32070 than zero and less than RSIZE_MAX, then the vsnwprintf_s function sets s[0] to
32071 the null wide character.
32074 The vsnwprintf_s function is equivalent to the vswprintf function except for the
32075 explicit runtime-constraints listed above.
32077 The vsnwprintf_s function, unlike vswprintf_s, will truncate the result to fit
32078 within the array pointed to by s.
32081 The vsnwprintf_s function returns the number of wide characters that would have
32082 been written had n been sufficiently large, not counting the terminating null character, or
32083 a negative value if a runtime-constraint violation occurred. Thus, the null-terminated
32084 output has been completely written if and only if the returned value is nonnegative and
32085 less than n.
32088 <p><small><a name="note422" href="#note422">422)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32089 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32090 example, if the entire format string was L"%%n".
32091 </small>
32097 <pre>
32098 #define __STDC_WANT_LIB_EXT1__ 1
32101 int vswprintf_s(wchar_t * restrict s,
32102 rsize_t n,
32103 const wchar_t * restrict format,
32104 va_list arg);
32105 </pre>
32106 Runtime-constraints
32108 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
32109 than RSIZE_MAX. The number of wide characters (including the trailing null) required
32110 for the result to be written to the array pointed to by s shall not be greater than n. The %n
32111 specifier<sup><a href="#note423"><b>423)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
32112 wide string pointed to by format. Any argument to vswprintf_s corresponding to a
32113 %s specifier shall not be a null pointer. No encoding error shall occur.
32115 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
32116 than zero and less than RSIZE_MAX, then the vswprintf_s function sets s[0] to the
32117 null wide character.
32119 <!--page 649 -->
32122 The vswprintf_s function is equivalent to the vswprintf function except for the
32123 explicit runtime-constraints listed above.
32125 The vswprintf_s function, unlike vsnwprintf_s, treats a result too big for the
32126 array pointed to by s as a runtime-constraint violation.
32129 If no runtime-constraint violation occurred, the vswprintf_s function returns the
32130 number of wide characters written in the array, not counting the terminating null wide
32131 character. If an encoding error occurred or if n or more wide characters are requested to
32132 be written, vswprintf_s returns a negative value. If any other runtime-constraint
32133 violation occurred, vswprintf_s returns zero.
32136 <p><small><a name="note423" href="#note423">423)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32137 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32138 example, if the entire format string was L"%%n".
32139 </small>
32145 <pre>
32146 #define __STDC_WANT_LIB_EXT1__ 1
32149 int vswscanf_s(const wchar_t * restrict s,
32150 const wchar_t * restrict format,
32151 va_list arg);
32152 </pre>
32153 Runtime-constraints
32155 Neither s nor format shall be a null pointer. Any argument indirected though in order
32156 to store converted input shall not be a null pointer.
32158 If there is a runtime-constraint violation, the vswscanf_s function does not attempt to
32159 perform further input, and it is unspecified to what extent vswscanf_s performed input
32160 before discovering the runtime-constraint violation.
32163 The vswscanf_s function is equivalent to swscanf_s, with the variable argument
32164 list replaced by arg, which shall have been initialized by the va_start macro (and
32165 possibly subsequent va_arg calls). The vswscanf_s function does not invoke the
32171 <!--page 650 -->
32174 The vswscanf_s function returns the value of the macro EOF if an input failure occurs
32175 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32176 vswscanf_s function returns the number of input items assigned, which can be fewer
32177 than provided for, or even zero, in the event of an early matching failure.
32180 <p><small><a name="note424" href="#note424">424)</a> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
32181 value of arg after the return is indeterminate.
32182 </small>
32188 <pre>
32189 #define __STDC_WANT_LIB_EXT1__ 1
32192 int vwprintf_s(const wchar_t * restrict format,
32193 va_list arg);
32194 </pre>
32195 Runtime-constraints
32197 format shall not be a null pointer. The %n specifier<sup><a href="#note425"><b>425)</b></a></sup> (modified or not by flags, field
32198 width, or precision) shall not appear in the wide string pointed to by format. Any
32199 argument to vwprintf_s corresponding to a %s specifier shall not be a null pointer.
32201 If there is a runtime-constraint violation, the vwprintf_s function does not attempt to
32202 produce further output, and it is unspecified to what extent vwprintf_s produced
32203 output before discovering the runtime-constraint violation.
32206 The vwprintf_s function is equivalent to the vwprintf function except for the
32207 explicit runtime-constraints listed above.
32210 The vwprintf_s function returns the number of wide characters transmitted, or a
32211 negative value if an output error, encoding error, or runtime-constraint violation occurred.
32216 <!--page 651 -->
32219 <p><small><a name="note425" href="#note425">425)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32220 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32221 example, if the entire format string was L"%%n".
32222 </small>
32228 <pre>
32229 #define __STDC_WANT_LIB_EXT1__ 1
32232 int vwscanf_s(const wchar_t * restrict format,
32233 va_list arg);
32234 </pre>
32235 Runtime-constraints
32237 format shall not be a null pointer. Any argument indirected though in order to store
32238 converted input shall not be a null pointer.
32240 If there is a runtime-constraint violation, the vwscanf_s function does not attempt to
32241 perform further input, and it is unspecified to what extent vwscanf_s performed input
32242 before discovering the runtime-constraint violation.
32245 The vwscanf_s function is equivalent to wscanf_s, with the variable argument list
32246 replaced by arg, which shall have been initialized by the va_start macro (and
32247 possibly subsequent va_arg calls). The vwscanf_s function does not invoke the
32251 The vwscanf_s function returns the value of the macro EOF if an input failure occurs
32252 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32253 vwscanf_s function returns the number of input items assigned, which can be fewer
32254 than provided for, or even zero, in the event of an early matching failure.
32257 <p><small><a name="note426" href="#note426">426)</a> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
32258 value of arg after the return is indeterminate.
32259 </small>
32265 <pre>
32266 #define __STDC_WANT_LIB_EXT1__ 1
32268 int wprintf_s(const wchar_t * restrict format, ...);
32269 </pre>
32270 Runtime-constraints
32272 format shall not be a null pointer. The %n specifier<sup><a href="#note427"><b>427)</b></a></sup> (modified or not by flags, field
32274 <!--page 652 -->
32275 width, or precision) shall not appear in the wide string pointed to by format. Any
32276 argument to wprintf_s corresponding to a %s specifier shall not be a null pointer.
32278 If there is a runtime-constraint violation, the wprintf_s function does not attempt to
32279 produce further output, and it is unspecified to what extent wprintf_s produced output
32280 before discovering the runtime-constraint violation.
32283 The wprintf_s function is equivalent to the wprintf function except for the explicit
32284 runtime-constraints listed above.
32287 The wprintf_s function returns the number of wide characters transmitted, or a
32288 negative value if an output error, encoding error, or runtime-constraint violation occurred.
32291 <p><small><a name="note427" href="#note427">427)</a> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
32292 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
32293 example, if the entire format string was L"%%n".
32294 </small>
32300 <pre>
32301 #define __STDC_WANT_LIB_EXT1__ 1
32303 int wscanf_s(const wchar_t * restrict format, ...);
32304 </pre>
32305 Runtime-constraints
32307 format shall not be a null pointer. Any argument indirected though in order to store
32308 converted input shall not be a null pointer.
32310 If there is a runtime-constraint violation, the wscanf_s function does not attempt to
32311 perform further input, and it is unspecified to what extent wscanf_s performed input
32312 before discovering the runtime-constraint violation.
32315 The wscanf_s function is equivalent to fwscanf_s with the argument stdin
32316 interposed before the arguments to wscanf_s.
32319 The wscanf_s function returns the value of the macro EOF if an input failure occurs
32320 before any conversion or if there is a runtime-constraint violation. Otherwise, the
32321 wscanf_s function returns the number of input items assigned, which can be fewer than
32322 provided for, or even zero, in the event of an early matching failure.
32323 <!--page 653 -->
32335 <pre>
32336 #define __STDC_WANT_LIB_EXT1__ 1
32338 errno_t wcscpy_s(wchar_t * restrict s1,
32339 rsize_t s1max,
32340 const wchar_t * restrict s2);
32341 </pre>
32342 Runtime-constraints
32344 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
32345 s1max shall not equal zero. s1max shall be greater than wcsnlen_s(s2, s1max).
32346 Copying shall not take place between objects that overlap.
32348 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32349 greater than zero and not greater than RSIZE_MAX, then wcscpy_s sets s1[0] to the
32350 null wide character.
32353 The wcscpy_s function copies the wide string pointed to by s2 (including the
32354 terminating null wide character) into the array pointed to by s1.
32356 All elements following the terminating null wide character (if any) written by
32357 wcscpy_s in the array of s1max wide characters pointed to by s1 take unspecified
32361 The wcscpy_s function returns zero<sup><a href="#note429"><b>429)</b></a></sup> if there was no runtime-constraint violation.
32362 Otherwise, a nonzero value is returned.
32367 <!--page 654 -->
32370 <p><small><a name="note428" href="#note428">428)</a> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
32371 if any of those wide characters are null. Such an approach might write a wide character to every
32372 element of s1 before discovering that the first element should be set to the null wide character.
32373 </small>
32374 <p><small><a name="note429" href="#note429">429)</a> A zero return value implies that all of the requested wide characters from the string pointed to by s2
32375 fit within the array pointed to by s1 and that the result in s1 is null terminated.
32376 </small>
32382 <pre>
32383 #define __STDC_WANT_LIB_EXT1__ 1
32385 errno_t wcsncpy_s(wchar_t * restrict s1,
32386 rsize_t s1max,
32387 const wchar_t * restrict s2,
32388 rsize_t n);
32389 </pre>
32390 Runtime-constraints
32392 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32393 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
32394 shall be greater than wcsnlen_s(s2, s1max). Copying shall not take place between
32395 objects that overlap.
32397 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32398 greater than zero and not greater than RSIZE_MAX, then wcsncpy_s sets s1[0] to the
32399 null wide character.
32402 The wcsncpy_s function copies not more than n successive wide characters (wide
32403 characters that follow a null wide character are not copied) from the array pointed to by
32404 s2 to the array pointed to by s1. If no null wide character was copied from s2, then
32405 s1[n] is set to a null wide character.
32407 All elements following the terminating null wide character (if any) written by
32408 wcsncpy_s in the array of s1max wide characters pointed to by s1 take unspecified
32412 The wcsncpy_s function returns zero<sup><a href="#note431"><b>431)</b></a></sup> if there was no runtime-constraint violation.
32413 Otherwise, a nonzero value is returned.
32415 EXAMPLE 1 The wcsncpy_s function can be used to copy a wide string without the danger that the
32416 result will not be null terminated or that wide characters will be written past the end of the destination
32417 array.
32422 <!--page 655 -->
32423 <pre>
32424 #define __STDC_WANT_LIB_EXT1__ 1
32426 /* ... */
32428 wchar_t src2[7] = {L'g', L'o', L'o', L'd', L'b', L'y', L'e'};
32430 int r1, r2, r3;
32434 </pre>
32435 The first call will assign to r1 the value zero and to dst1 the sequence of wide characters hello\0.
32436 The second call will assign to r2 a nonzero value and to dst2 the sequence of wide characters \0.
32437 The third call will assign to r3 the value zero and to dst3 the sequence of wide characters good\0.
32441 <p><small><a name="note430" href="#note430">430)</a> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
32442 if any of those wide characters are null. Such an approach might write a wide character to every
32443 element of s1 before discovering that the first element should be set to the null wide character.
32444 </small>
32445 <p><small><a name="note431" href="#note431">431)</a> A zero return value implies that all of the requested wide characters from the string pointed to by s2
32446 fit within the array pointed to by s1 and that the result in s1 is null terminated.
32447 </small>
32453 <pre>
32454 #define __STDC_WANT_LIB_EXT1__ 1
32456 errno_t wmemcpy_s(wchar_t * restrict s1,
32457 rsize_t s1max,
32458 const wchar_t * restrict s2,
32459 rsize_t n);
32460 </pre>
32461 Runtime-constraints
32463 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32464 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
32465 objects that overlap.
32467 If there is a runtime-constraint violation, the wmemcpy_s function stores zeros in the
32468 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
32469 s1max is not greater than RSIZE_MAX.
32472 The wmemcpy_s function copies n successive wide characters from the object pointed
32473 to by s2 into the object pointed to by s1.
32476 The wmemcpy_s function returns zero if there was no runtime-constraint violation.
32477 Otherwise, a nonzero value is returned.
32478 <!--page 656 -->
32484 <pre>
32485 #define __STDC_WANT_LIB_EXT1__ 1
32487 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
32488 const wchar_t *s2, rsize_t n);
32489 </pre>
32490 Runtime-constraints
32492 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32493 RSIZE_MAX. n shall not be greater than s1max.
32495 If there is a runtime-constraint violation, the wmemmove_s function stores zeros in the
32496 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
32497 s1max is not greater than RSIZE_MAX.
32500 The wmemmove_s function copies n successive wide characters from the object pointed
32501 to by s2 into the object pointed to by s1. This copying takes place as if the n wide
32502 characters from the object pointed to by s2 are first copied into a temporary array of n
32503 wide characters that does not overlap the objects pointed to by s1 or s2, and then the n
32504 wide characters from the temporary array are copied into the object pointed to by s1.
32507 The wmemmove_s function returns zero if there was no runtime-constraint violation.
32508 Otherwise, a nonzero value is returned.
32511 <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>
32517 <pre>
32518 #define __STDC_WANT_LIB_EXT1__ 1
32520 errno_t wcscat_s(wchar_t * restrict s1,
32521 rsize_t s1max,
32522 const wchar_t * restrict s2);
32523 </pre>
32524 Runtime-constraints
32526 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
32527 wcscat_s.
32529 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
32530 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note432"><b>432)</b></a></sup> m shall be greater than
32531 wcsnlen_s(s2, m). Copying shall not take place between objects that overlap.
32532 <!--page 657 -->
32534 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32535 greater than zero and not greater than RSIZE_MAX, then wcscat_s sets s1[0] to the
32536 null wide character.
32539 The wcscat_s function appends a copy of the wide string pointed to by s2 (including
32540 the terminating null wide character) to the end of the wide string pointed to by s1. The
32541 initial wide character from s2 overwrites the null wide character at the end of s1.
32543 All elements following the terminating null wide character (if any) written by
32544 wcscat_s in the array of s1max wide characters pointed to by s1 take unspecified
32548 The wcscat_s function returns zero<sup><a href="#note434"><b>434)</b></a></sup> if there was no runtime-constraint violation.
32549 Otherwise, a nonzero value is returned.
32552 <p><small><a name="note432" href="#note432">432)</a> Zero means that s1 was not null terminated upon entry to wcscat_s.
32553 </small>
32554 <p><small><a name="note433" href="#note433">433)</a> This allows an implementation to append wide characters from s2 to s1 while simultaneously
32555 checking if any of those wide characters are null. Such an approach might write a wide character to
32556 every element of s1 before discovering that the first element should be set to the null wide character.
32557 </small>
32558 <p><small><a name="note434" href="#note434">434)</a> A zero return value implies that all of the requested wide characters from the wide string pointed to by
32559 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
32560 </small>
32566 <pre>
32567 #define __STDC_WANT_LIB_EXT1__ 1
32569 errno_t wcsncat_s(wchar_t * restrict s1,
32570 rsize_t s1max,
32571 const wchar_t * restrict s2,
32572 rsize_t n);
32573 </pre>
32574 Runtime-constraints
32576 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
32577 wcsncat_s.
32579 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
32580 RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.<sup><a href="#note435"><b>435)</b></a></sup> If n is not less
32581 than m, then m shall be greater than wcsnlen_s(s2, m). Copying shall not take
32582 place between objects that overlap.
32585 <!--page 658 -->
32587 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
32588 greater than zero and not greater than RSIZE_MAX, then wcsncat_s sets s1[0] to the
32589 null wide character.
32592 The wcsncat_s function appends not more than n successive wide characters (wide
32593 characters that follow a null wide character are not copied) from the array pointed to by
32594 s2 to the end of the wide string pointed to by s1. The initial wide character from s2
32595 overwrites the null wide character at the end of s1. If no null wide character was copied
32596 from s2, then s1[s1max-m+n] is set to a null wide character.
32598 All elements following the terminating null wide character (if any) written by
32599 wcsncat_s in the array of s1max wide characters pointed to by s1 take unspecified
32603 The wcsncat_s function returns zero<sup><a href="#note437"><b>437)</b></a></sup> if there was no runtime-constraint violation.
32604 Otherwise, a nonzero value is returned.
32606 EXAMPLE 1 The wcsncat_s function can be used to copy a wide string without the danger that the
32607 result will not be null terminated or that wide characters will be written past the end of the destination
32608 array.
32609 <pre>
32610 #define __STDC_WANT_LIB_EXT1__ 1
32612 /* ... */
32618 int r1, r2, r3, r4;
32623 </pre>
32624 After the first call r1 will have the value zero and s1 will be the wide character sequence goodbye\0.
32625 After the second call r2 will have the value zero and s2 will be the wide character sequence hello\0.
32626 After the third call r3 will have a nonzero value and s3 will be the wide character sequence \0.
32627 After the fourth call r4 will have the value zero and s4 will be the wide character sequence abcdef\0.
32632 <!--page 659 -->
32635 <p><small><a name="note435" href="#note435">435)</a> Zero means that s1 was not null terminated upon entry to wcsncat_s.
32636 </small>
32637 <p><small><a name="note436" href="#note436">436)</a> This allows an implementation to append wide characters from s2 to s1 while simultaneously
32638 checking if any of those wide characters are null. Such an approach might write a wide character to
32639 every element of s1 before discovering that the first element should be set to the null wide character.
32640 </small>
32641 <p><small><a name="note437" href="#note437">437)</a> A zero return value implies that all of the requested wide characters from the wide string pointed to by
32642 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
32643 </small>
32652 <pre>
32653 #define __STDC_WANT_LIB_EXT1__ 1
32655 wchar_t *wcstok_s(wchar_t * restrict s1,
32656 rsize_t * restrict s1max,
32657 const wchar_t * restrict s2,
32658 wchar_t ** restrict ptr);
32659 </pre>
32660 Runtime-constraints
32662 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
32663 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
32664 The end of the token found shall occur within the first *s1max wide characters of s1 for
32665 the first call, and shall occur within the first *s1max wide characters of where searching
32666 resumes on subsequent calls.
32668 If there is a runtime-constraint violation, the wcstok_s function does not indirect
32669 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
32672 A sequence of calls to the wcstok_s function breaks the wide string pointed to by s1
32673 into a sequence of tokens, each of which is delimited by a wide character from the wide
32674 string pointed to by s2. The fourth argument points to a caller-provided wchar_t
32675 pointer into which the wcstok_s function stores information necessary for it to
32676 continue scanning the same wide string.
32678 The first call in a sequence has a non-null first argument and s1max points to an object
32679 whose value is the number of elements in the wide character array pointed to by the first
32680 argument. The first call stores an initial value in the object pointed to by ptr and
32681 updates the value pointed to by s1max to reflect the number of elements that remain in
32682 relation to ptr. Subsequent calls in the sequence have a null first argument and the
32683 objects pointed to by s1max and ptr are required to have the values stored by the
32684 previous call in the sequence, which are then updated. The separator wide string pointed
32685 to by s2 may be different from call to call.
32687 The first call in the sequence searches the wide string pointed to by s1 for the first wide
32688 character that is not contained in the current separator wide string pointed to by s2. If no
32689 such wide character is found, then there are no tokens in the wide string pointed to by s1
32690 and the wcstok_s function returns a null pointer. If such a wide character is found, it is
32691 the start of the first token.
32692 <!--page 660 -->
32694 The wcstok_s function then searches from there for the first wide character in s1 that
32695 is contained in the current separator wide string. If no such wide character is found, the
32696 current token extends to the end of the wide string pointed to by s1, and subsequent
32697 searches in the same wide string for a token return a null pointer. If such a wide character
32698 is found, it is overwritten by a null wide character, which terminates the current token.
32700 In all cases, the wcstok_s function stores sufficient information in the pointer pointed
32701 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
32702 value for ptr, shall start searching just past the element overwritten by a null wide
32703 character (if any).
32706 The wcstok_s function returns a pointer to the first wide character of a token, or a null
32707 pointer if there is no token or there is a runtime-constraint violation.
32709 EXAMPLE
32710 <pre>
32711 #define __STDC_WANT_LIB_EXT1__ 1
32713 static wchar_t str1[] = L"?a???b,,,#c";
32714 static wchar_t str2[] = L"\t \t";
32715 wchar_t *t, *ptr1, *ptr2;
32716 rsize_t max1 = wcslen(str1)+1;
32717 rsize_t max2 = wcslen(str2)+1;
32723 </pre>
32733 <pre>
32734 #define __STDC_WANT_LIB_EXT1__ 1
32736 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
32737 </pre>
32740 The wcsnlen_s function computes the length of the wide string pointed to by s.
32743 If s is a null pointer,<sup><a href="#note438"><b>438)</b></a></sup> then the wcsnlen_s function returns zero.
32745 Otherwise, the wcsnlen_s function returns the number of wide characters that precede
32746 the terminating null wide character. If there is no null wide character in the first
32747 maxsize wide characters of s then wcsnlen_s returns maxsize. At most the first
32748 <!--page 661 -->
32749 maxsize wide characters of s shall be accessed by wcsnlen_s.
32752 <p><small><a name="note438" href="#note438">438)</a> Note that the wcsnlen_s function has no runtime-constraints. This lack of runtime-constraints
32753 along with the values returned for a null pointer or an unterminated wide string argument make
32754 wcsnlen_s useful in algorithms that gracefully handle such exceptional data.
32755 </small>
32758 <h5><a name="K.3.9.3" href="#K.3.9.3">K.3.9.3 Extended multibyte/wide character conversion utilities</a></h5>
32761 <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>
32763 Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the
32764 conversion state) to be a null pointer.
32770 <pre>
32772 errno_t wcrtomb_s(size_t * restrict retval,
32773 char * restrict s, rsize_t smax,
32774 wchar_t wc, mbstate_t * restrict ps);
32775 </pre>
32776 Runtime-constraints
32778 Neither retval nor ps shall be a null pointer. If s is not a null pointer, then smax
32779 shall not equal zero and shall not be greater than RSIZE_MAX. If s is not a null pointer,
32780 then smax shall be not be less than the number of bytes to be stored in the array pointed
32781 to by s. If s is a null pointer, then smax shall equal zero.
32783 If there is a runtime-constraint violation, then wcrtomb_s does the following. If s is
32784 not a null pointer and smax is greater than zero and not greater than RSIZE_MAX, then
32785 wcrtomb_s sets s[0] to the null character. If retval is not a null pointer, then
32786 wcrtomb_s sets *retval to (size_t)(-1).
32789 If s is a null pointer, the wcrtomb_s function is equivalent to the call
32790 <pre>
32792 </pre>
32793 where retval and buf are internal variables of the appropriate types, and the size of
32794 buf is greater than MB_CUR_MAX.
32796 If s is not a null pointer, the wcrtomb_s function determines the number of bytes
32797 needed to represent the multibyte character that corresponds to the wide character given
32798 by wc (including any shift sequences), and stores the multibyte character representation
32799 in the array whose first element is pointed to by s. At most MB_CUR_MAX bytes are
32800 stored. If wc is a null wide character, a null byte is stored, preceded by any shift
32801 sequence needed to restore the initial shift state; the resulting state described is the initial
32802 conversion state.
32804 <!--page 662 -->
32806 If wc does not correspond to a valid multibyte character, an encoding error occurs: the
32807 wcrtomb_s function stores the value (size_t)(-1) into *retval and the
32808 conversion state is unspecified. Otherwise, the wcrtomb_s function stores into
32809 *retval the number of bytes (including any shift sequences) stored in the array pointed
32810 to by s.
32813 The wcrtomb_s function returns zero if no runtime-constraint violation and no
32814 encoding error occurred. Otherwise, a nonzero value is returned.
32817 <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>
32819 Unlike mbsrtowcs and wcsrtombs, mbsrtowcs_s and wcsrtombs_s do not
32820 permit the ps parameter (the pointer to the conversion state) to be a null pointer.
32826 <pre>
32828 errno_t mbsrtowcs_s(size_t * restrict retval,
32829 wchar_t * restrict dst, rsize_t dstmax,
32830 const char ** restrict src, rsize_t len,
32831 mbstate_t * restrict ps);
32832 </pre>
32833 Runtime-constraints
32835 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
32836 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
32837 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
32838 not equal zero. If dst is not a null pointer and len is not less than dstmax, then a null
32839 character shall occur within the first dstmax multibyte characters of the array pointed to
32840 by *src.
32842 If there is a runtime-constraint violation, then mbsrtowcs_s does the following. If
32843 retval is not a null pointer, then mbsrtowcs_s sets *retval to (size_t)(-1).
32844 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
32845 then mbsrtowcs_s sets dst[0] to the null wide character.
32848 The mbsrtowcs_s function converts a sequence of multibyte characters that begins in
32849 the conversion state described by the object pointed to by ps, from the array indirectly
32850 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
32851 pointer, the converted characters are stored into the array pointed to by dst. Conversion
32852 continues up to and including a terminating null character, which is also stored.
32853 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
32854 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
32855 <!--page 663 -->
32856 characters have been stored into the array pointed to by dst.<sup><a href="#note439"><b>439)</b></a></sup> If dst is not a null
32857 pointer and no null wide character was stored into the array pointed to by dst, then
32858 dst[len] is set to the null wide character. Each conversion takes place as if by a call
32859 to the mbrtowc function.
32861 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
32862 pointer (if conversion stopped due to reaching a terminating null character) or the address
32863 just past the last multibyte character converted (if any). If conversion stopped due to
32864 reaching a terminating null character and if dst is not a null pointer, the resulting state
32865 described is the initial conversion state.
32867 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
32868 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
32869 the mbsrtowcs_s function stores the value (size_t)(-1) into *retval and the
32870 conversion state is unspecified. Otherwise, the mbsrtowcs_s function stores into
32871 *retval the number of multibyte characters successfully converted, not including the
32872 terminating null character (if any).
32874 All elements following the terminating null wide character (if any) written by
32875 mbsrtowcs_s in the array of dstmax wide characters pointed to by dst take
32878 If copying takes place between objects that overlap, the objects take on unspecified
32879 values.
32882 The mbsrtowcs_s function returns zero if no runtime-constraint violation and no
32883 encoding error occurred. Otherwise, a nonzero value is returned.
32886 <p><small><a name="note439" href="#note439">439)</a> Thus, the value of len is ignored if dst is a null pointer.
32887 </small>
32888 <p><small><a name="note440" href="#note440">440)</a> This allows an implementation to attempt converting the multibyte string before discovering a
32889 terminating null character did not occur where required.
32890 </small>
32896 <pre>
32898 errno_t wcsrtombs_s(size_t * restrict retval,
32899 char * restrict dst, rsize_t dstmax,
32900 const wchar_t ** restrict src, rsize_t len,
32901 mbstate_t * restrict ps);
32902 </pre>
32907 <!--page 664 -->
32908 Runtime-constraints
32910 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
32911 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
32912 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
32913 not equal zero. If dst is not a null pointer and len is not less than dstmax, then the
32914 conversion shall have been stopped (see below) because a terminating null wide character
32915 was reached or because an encoding error occurred.
32917 If there is a runtime-constraint violation, then wcsrtombs_s does the following. If
32918 retval is not a null pointer, then wcsrtombs_s sets *retval to (size_t)(-1).
32919 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
32920 then wcsrtombs_s sets dst[0] to the null character.
32923 The wcsrtombs_s function converts a sequence of wide characters from the array
32924 indirectly pointed to by src into a sequence of corresponding multibyte characters that
32925 begins in the conversion state described by the object pointed to by ps. If dst is not a
32926 null pointer, the converted characters are then stored into the array pointed to by dst.
32927 Conversion continues up to and including a terminating null wide character, which is also
32928 stored. Conversion stops earlier in two cases:
32929 <ul>
32930 <li> when a wide character is reached that does not correspond to a valid multibyte
32931 character;
32932 <li> (if dst is not a null pointer) when the next multibyte character would exceed the
32933 limit of n total bytes to be stored into the array pointed to by dst. If the wide
32934 character being converted is the null wide character, then n is the lesser of len or
32935 dstmax. Otherwise, n is the lesser of len or dstmax-1.
32936 </ul>
32937 If the conversion stops without converting a null wide character and dst is not a null
32938 pointer, then a null character is stored into the array pointed to by dst immediately
32939 following any multibyte characters already stored. Each conversion takes place as if by a
32942 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
32943 pointer (if conversion stopped due to reaching a terminating null wide character) or the
32944 address just past the last wide character converted (if any). If conversion stopped due to
32945 reaching a terminating null wide character, the resulting state described is the initial
32946 conversion state.
32949 <!--page 665 -->
32951 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
32952 wide character that does not correspond to a valid multibyte character, an encoding error
32953 occurs: the wcsrtombs_s function stores the value (size_t)(-1) into *retval
32954 and the conversion state is unspecified. Otherwise, the wcsrtombs_s function stores
32955 into *retval the number of bytes in the resulting multibyte character sequence, not
32956 including the terminating null character (if any).
32958 All elements following the terminating null character (if any) written by wcsrtombs_s
32959 in the array of dstmax elements pointed to by dst take unspecified values when
32962 If copying takes place between objects that overlap, the objects take on unspecified
32963 values.
32966 The wcsrtombs_s function returns zero if no runtime-constraint violation and no
32967 encoding error occurred. Otherwise, a nonzero value is returned.
32972 <!--page 666 -->
32975 <p><small><a name="note441" href="#note441">441)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
32976 include those necessary to reach the initial shift state immediately before the null byte. However, if
32977 the conversion stops before a terminating null wide character has been reached, the result will be null
32978 terminated, but might not end in the initial shift state.
32979 </small>
32980 <p><small><a name="note442" href="#note442">442)</a> When len is not less than dstmax, the implementation might fill the array before discovering a
32981 runtime-constraint violation.
32982 </small>
32986 <pre>
32987 (normative)
32988 Analyzability
32989 </pre>
32994 This annex specifies optional behavior that can aid in the analyzability of C programs.
32996 An implementation that defines __STDC_ANALYZABLE__ shall conform to the
33000 <p><small><a name="note443" href="#note443">443)</a> Implementations that do not define __STDC_ANALYZABLE__ are not required to conform to these
33001 specifications.
33002 </small>
33010 out-of-bounds store
33011 an (attempted) access (<a href="#3.1">3.1</a>) that, at run time, for a given computational state, would
33012 modify (or, for an object declared volatile, fetch) one or more bytes that lie outside
33013 the bounds permitted by this Standard.
33018 bounded undefined behavior
33021 NOTE 1 The behavior might perform a trap.
33024 NOTE 2 Any values produced or stored might be indeterminate values.
33030 critical undefined behavior
33031 undefined behavior that is not bounded undefined behavior.
33033 NOTE The behavior might perform an out-of-bounds store or perform a trap.
33038 <!--page 667 -->
33043 If the program performs a trap (<a href="#3.19.5">3.19.5</a>), the implementation is permitted to invoke a
33044 runtime-constraint handler. Any such semantics are implementation-defined.
33046 All undefined behavior shall be limited to bounded undefined behavior, except for the
33047 following which are permitted to result in critical undefined behavior:
33048 <ul>
33051 <li> A pointer is used to call a function whose type is not compatible with the referenced
33053 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
33054 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
33055 integer type produces a result that points just beyond the array object and is used as
33057 <li> An argument to a library function has an invalid value or a type not expected by a
33059 <li> The value of a pointer that refers to space deallocated by a call to the free or realloc
33061 <li> A string or wide string utility function is instructed to access an array beyond the end
33063 <!--page 668 -->
33064 </ul>
33068 <ol>
33069 <li> ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
33070 published in The C Programming Language by Brian W. Kernighan and Dennis
33073 California, USA, November 1984.
33075 Processing Systems, Information Processing Systems Technical Report.
33077 Arithmetic.
33079 Floating-Point Arithmetic.
33083 symbols for use in the physical sciences and technology.
33085 information interchange.
33087 Fundamental terms.
33090 interchange -- Representation of dates and times.
33099 <!--page 669 -->
33101 Interface (POSIX) -- Part 2: Shell and Utilities.
33103 preparation of programming language standards.
33105 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
33117 syllables.
33119 Tibetan.
33121 additional characters.
33124 Identifiers for characters.
33126 Ethiopic.
33128 Unified Canadian Aboriginal Syllabics.
33130 Cherokee.
33132 arithmetic -- Part 1: Integer and floating point arithmetic.
33133 <!--page 670 -->
33135 their environments and system software interfaces -- Extensions for the
33136 programming language C to support new character data types.
33138 their environments and system software interfaces -- Extensions to the C library
33139 -- Part 1: Bounds-checking interfaces.
33140 <!--page 671 -->
33141 </ol>
33145 <pre>
33146 [^ 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>
33147 , (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>,
33149 ! (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>
33150 != (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>
33151 # 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>
33152 # 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>
33153 # punctuator, <a href="#6.10">6.10</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
33154 ## 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>
33155 #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>,
33157 #else preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.9">6.7.9</a>
33158 #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>
33159 #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>
33160 #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>
33161 <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>
33162 #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>
33163 #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>
33164 #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>
33165 <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>,
33166 #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>
33167 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
33168 #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>
33170 % (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>
33171 %: (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>
33172 %:%: (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>
33173 %= (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>
33174 %> (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>,
33175 & (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="#7.24">7.24</a>, <a href="#7.30.1">7.30.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
33176 & (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="#7.30.2">7.30.2</a>
33177 && (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="#7.30.3">7.30.3</a>, <a href="#K.3.2">K.3.2</a>
33178 &= (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>, <a href="#F">F</a>,
33179 ' ' (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="#H">H</a>
33180 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.29.2.1.3">7.29.2.1.3</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>,
33182 ( ) (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="#7.30.4">7.30.4</a>
33183 ( ) (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>
33184 ( ){ } (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>
33185 * (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="#7.30.5">7.30.5</a>
33186 * (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="#7.24">7.24</a>, <a href="#F">F</a>,
33187 * (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>
33188 <a href="#G.5.1">G.5.1</a> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
33189 *= (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="#7.30.6">7.30.6</a>
33190 + (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>
33191 <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>
33192 + (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>
33193 ++ (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="#7.18"><stdbool.h></a> header, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.30.7">7.30.7</a>, <a href="#H">H</a>
33194 ++ (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="#7.19"><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>,
33196 <!--page 672 -->
33197 <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> \x hexadecimal digits (hexadecimal-character
33198 <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>, escape sequence), <a href="#6.4.4.4">6.4.4.4</a>
33199 <a href="#7.20">7.20</a>, <a href="#7.30.8">7.30.8</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</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>
33200 <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="#7.30.9">7.30.9</a>, <a href="#F">F</a>, ^= (bitwise exclusive OR assignment operator),
33202 <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="#7.30.10">7.30.10</a>, <a href="#F">F</a>, __alignas_is_defined macro, <a href="#7.15">7.15</a>
33204 <a href="#7.23"><string.h></a> header, <a href="#7.23">7.23</a>, <a href="#7.30.11">7.30.11</a>, <a href="#K.3.7">K.3.7</a> macro, <a href="#7.18">7.18</a>
33205 <a href="#7.24"><tgmath.h></a> header, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> __cplusplus macro, <a href="#6.10.8">6.10.8</a>
33206 <a href="#7.25"><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="#7.25">7.25</a> __DATE__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33207 <a href="#7.26"><time.h></a> header, <a href="#7.26">7.26</a>, <a href="#K.3.8">K.3.8</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>
33208 <a href="#7.27"><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="#7.27">7.27</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>
33209 <a href="#7.28"><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="#7.28">7.28</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>
33210 <a href="#7.30.12">7.30.12</a>, <a href="#F">F</a>, <a href="#K.3.9">K.3.9</a> __STDC_, <a href="#6.11.9">6.11.9</a>
33211 <a href="#7.29"><wctype.h></a> header, <a href="#7.29">7.29</a>, <a href="#7.30.13">7.30.13</a> __STDC__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33212 = (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_ANALYZABLE__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#L.1">L.1</a>
33213 = (simple assignment operator), <a href="#6.5.16.1">6.5.16.1</a> __STDC_HOSTED__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33214 == (equality operator), <a href="#6.5.9">6.5.9</a> __STDC_IEC_559__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#F.1">F.1</a>
33216 >= (greater-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a> <a href="#6.10.8.3">6.10.8.3</a>, <a href="#G.1">G.1</a>
33217 >> (right-shift operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a> __STDC_ISO_10646__ macro, <a href="#6.10.8.2">6.10.8.2</a>
33218 >>= (right-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a> __STDC_LIB_EXT1__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#K.2">K.2</a>
33219 ? : (conditional operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.15">6.5.15</a> __STDC_MB_MIGHT_NEQ_WC__ macro,
33220 ?? (trigraph sequences), <a href="#5.2.1.1">5.2.1.1</a> <a href="#6.10.8.2">6.10.8.2</a>, <a href="#7.19">7.19</a>
33221 [ ] (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> __STDC_NO_COMPLEX__ macro, <a href="#6.10.8.3">6.10.8.3</a>,
33222 [ ] (brackets punctuator), <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.9">6.7.9</a> <a href="#7.3.1">7.3.1</a>
33223 \ (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> __STDC_NO_THREADS__ macro, <a href="#6.10.8.3">6.10.8.3</a>,
33224 \ (escape character), <a href="#6.4.4.4">6.4.4.4</a> <a href="#7.17.1">7.17.1</a>, <a href="#7.25.1">7.25.1</a>
33225 \" (double-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, __STDC_NO_VLA__ macro, <a href="#6.10.8.3">6.10.8.3</a>
33226 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> __STDC_UTF_16__ macro, <a href="#6.10.8.2">6.10.8.2</a>
33227 \\ (backslash escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a> __STDC_UTF_32__ macro, <a href="#6.10.8.2">6.10.8.2</a>
33228 \' (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_VERSION__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33229 \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_WANT_LIB_EXT1__ macro, <a href="#K.3.1.1">K.3.1.1</a>
33230 padding of binary stream, <a href="#7.21.2">7.21.2</a> __TIME__ macro, <a href="#6.10.8.1">6.10.8.1</a>
33231 \? (question-mark escape sequence), <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>
33232 \a (alert escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _Alignas, <a href="#6.7.5">6.7.5</a>
33233 \b (backspace escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _Atomic type qualifier, <a href="#6.7.3">6.7.3</a>
33234 \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>, _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="#7.17.1">7.17.1</a>,
33236 \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>, _Bool type conversions, <a href="#6.3.1.2">6.3.1.2</a>
33237 <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>
33239 <a href="#6.4.4.4">6.4.4.4</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>
33240 \r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, _Imaginary keyword, <a href="#G.2">G.2</a>
33241 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> _Imaginary types, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
33242 \t (horizontal-tab escape sequence), <a href="#5.2.2">5.2.2</a>, _Imaginary_I macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a>
33243 <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="#7.29.2.1.3">7.29.2.1.3</a> _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>
33244 \U (universal character names), <a href="#6.4.3">6.4.3</a> _IOLBF macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.6">7.21.5.6</a>
33245 \u (universal character names), <a href="#6.4.3">6.4.3</a> _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>
33246 \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>, _Noreturn, <a href="#6.7.4">6.7.4</a>
33247 <a href="#7.4.1.10">7.4.1.10</a> _Pragma operator, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a>
33248 <!--page 673 -->
33249 _Static_assert, <a href="#6.7.10">6.7.10</a>, <a href="#7.2">7.2</a> allocated storage, order and contiguity, <a href="#7.22.3">7.22.3</a>
33250 _Thread_local storage-class specifier, <a href="#6.2.4">6.2.4</a>, and macro, <a href="#7.9">7.9</a>
33252 { } (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>, bitwise (&), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.10">6.5.10</a>
33254 { } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> logical (&&), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a>
33255 | (bitwise inclusive OR operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a> and_eq macro, <a href="#7.9">7.9</a>
33256 |= (bitwise inclusive OR assignment operator), anonymous structure, <a href="#6.7.2.1">6.7.2.1</a>
33258 || (logical OR operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a> ANSI/IEEE 754, <a href="#F.1">F.1</a>
33259 ~ (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> ANSI/IEEE 854, <a href="#F.1">F.1</a>
33261 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>, argument, <a href="#3.3">3.3</a>
33262 <a href="#7.22.4.1">7.22.4.1</a>, <a href="#7.25.3.6">7.25.3.6</a>, <a href="#K.3.6.1.2">K.3.6.1.2</a> array, <a href="#6.9.1">6.9.1</a>
33263 abort_handler_s function, <a href="#K.3.6.1.2">K.3.6.1.2</a> default promotions, <a href="#6.5.2.2">6.5.2.2</a>
33264 abs function, <a href="#7.22.6.1">7.22.6.1</a> function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
33266 complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a> argument, complex, <a href="#7.3.9.1">7.3.9.1</a>
33267 integer, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.22.6.1">7.22.6.1</a> argv (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a>
33268 real, <a href="#7.12.7">7.12.7</a>, <a href="#F.10.4">F.10.4</a> arithmetic constant expression, <a href="#6.6">6.6</a>
33269 abstract declarator, <a href="#6.7.7">6.7.7</a> arithmetic conversions, usual, see usual arithmetic
33271 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 operators
33272 accuracy, see floating-point accuracy 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>
33273 acos functions, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#F.10.1.1">F.10.1.1</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>
33274 acos type-generic macro, <a href="#7.24">7.24</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>
33275 acosh functions, <a href="#7.12.5.1">7.12.5.1</a>, <a href="#F.10.2.1">F.10.2.1</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>
33276 acosh type-generic macro, <a href="#7.24">7.24</a> shift, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
33278 acquire operation, <a href="#5.1.2.4">5.1.2.4</a> arithmetic types, <a href="#6.2.5">6.2.5</a>
33282 addition assignment operator (+=), <a href="#6.5.16.2">6.5.16.2</a> declarator, <a href="#6.7.6.2">6.7.6.2</a>
33283 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>, initialization, <a href="#6.7.9">6.7.9</a>
33284 <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> multidimensional, <a href="#6.5.2.1">6.5.2.1</a>
33285 additive expressions, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> parameter, <a href="#6.9.1">6.9.1</a>
33287 address operator (&), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</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>
33291 alert escape sequence (\a), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> 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>
33294 aligned_alloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.1">7.22.3.1</a> ASCII code set, <a href="#5.2.1.1">5.2.1.1</a>
33295 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> asctime function, <a href="#7.26.3.1">7.26.3.1</a>
33296 pointer, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.3">6.3.2.3</a> 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>
33297 structure/union member, <a href="#6.7.2.1">6.7.2.1</a> asin functions, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#F.10.1.2">F.10.1.2</a>
33298 alignment specifier, <a href="#6.7.5">6.7.5</a> asin type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
33299 alignof operator, <a href="#6.5.3">6.5.3</a>, <a href="#6.5.3.4">6.5.3.4</a> asinh functions, <a href="#7.12.5.2">7.12.5.2</a>, <a href="#F.10.2.2">F.10.2.2</a>
33300 <!--page 674 -->
33301 asinh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> atomic_is_lock_free generic function,
33303 assert macro, <a href="#7.2.1.1">7.2.1.1</a> ATOMIC_LLONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33304 assert.h header, <a href="#7.2">7.2</a> atomic_load generic functions, <a href="#7.17.7.2">7.17.7.2</a>
33306 compound, <a href="#6.5.16.2">6.5.16.2</a> ATOMIC_SHORT_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33307 conversion, <a href="#6.5.16.1">6.5.16.1</a> atomic_signal_fence function, <a href="#7.17.4.2">7.17.4.2</a>
33308 expression, <a href="#6.5.16">6.5.16</a> atomic_store generic functions, <a href="#7.17.7.1">7.17.7.1</a>
33309 operators, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a> atomic_thread_fence function, <a href="#7.17.4.1">7.17.4.1</a>
33310 simple, <a href="#6.5.16.1">6.5.16.1</a> ATOMIC_VAR_INIT macro, <a href="#7.17.2.1">7.17.2.1</a>
33311 associativity of operators, <a href="#6.5">6.5</a> ATOMIC_WCHAR_T_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
33312 asterisk punctuator (*), <a href="#6.7.6.1">6.7.6.1</a>, <a href="#6.7.6.2">6.7.6.2</a> atomics header, <a href="#7.17">7.17</a>
33313 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>, auto storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
33314 <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> automatic storage duration, <a href="#5.2.3">5.2.3</a>, <a href="#6.2.4">6.2.4</a>
33316 atan type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</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>
33317 atan2 functions, <a href="#7.12.4.4">7.12.4.4</a>, <a href="#F.10.1.4">F.10.1.4</a> backslash escape sequence (\\), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a>
33318 atan2 type-generic macro, <a href="#7.24">7.24</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>
33319 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 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>
33320 atanh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> basic types, <a href="#6.2.5">6.2.5</a>
33321 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>, behavior, <a href="#3.4">3.4</a>
33322 <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> 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>,
33323 atof function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.1">7.22.1.1</a> <a href="#7.21.9.4">7.21.9.4</a>
33324 atoi function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> bit, <a href="#3.5">3.5</a>
33325 atol 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>
33326 atoll 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>
33327 atomic lock-free macros, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.5">7.17.5</a> bit-field, <a href="#6.7.2.1">6.7.2.1</a>
33329 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>, bitor macro, <a href="#7.9">7.9</a>
33330 <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>, bitwise operators, <a href="#6.5">6.5</a>
33331 <a href="#7.17.6">7.17.6</a> AND, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.10">6.5.10</a>
33332 atomic_address type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.6">7.17.6</a> AND assignment (&=), <a href="#6.5.16.2">6.5.16.2</a>
33333 ATOMIC_ADDRESS_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>
33334 atomic_bool type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.6">7.17.6</a> exclusive OR, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a>
33335 ATOMIC_CHAR16_T_LOCK_FREE macro, exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
33336 <a href="#7.17.1">7.17.1</a> inclusive OR, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a>
33337 ATOMIC_CHAR32_T_LOCK_FREE macro, inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
33338 <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>
33339 ATOMIC_CHAR_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a> blank character, <a href="#7.4.1.3">7.4.1.3</a>
33340 atomic_compare_exchange generic 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>
33342 atomic_exchange generic functions, <a href="#7.17.7.3">7.17.7.3</a> block structure, <a href="#6.2.1">6.2.1</a>
33345 atomic_flag type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.8">7.17.8</a> boolean type, <a href="#6.3.1.2">6.3.1.2</a>
33346 atomic_flag_clear functions, <a href="#7.17.8.2">7.17.8.2</a> 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>
33347 ATOMIC_FLAG_INIT macro, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.8">7.17.8</a> bounded undefined behavior, <a href="#L.2.2">L.2.2</a>
33348 atomic_flag_test_and_set functions, 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>,
33350 atomic_init generic function, <a href="#7.17.2.2">7.17.2.2</a> brackets operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>
33351 ATOMIC_INT_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a> brackets punctuator ([ ]), <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.9">6.7.9</a>
33352 <!--page 675 -->
33354 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>
33355 broken-down time, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.3">7.26.2.3</a>, <a href="#7.26.3">7.26.3</a>, type-generic macro for, <a href="#7.24">7.24</a>
33356 <a href="#7.26.3.1">7.26.3.1</a>, <a href="#7.26.3.3">7.26.3.3</a>, <a href="#7.26.3.4">7.26.3.4</a>, <a href="#7.26.3.5">7.26.3.5</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>
33357 <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="#7.24">7.24</a>
33358 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="#7.30.1">7.30.1</a>
33359 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="#7.30.1">7.30.1</a>
33360 btowc function, <a href="#7.28.6.1.1">7.28.6.1.1</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>
33361 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="#7.24">7.24</a>
33362 byte, <a href="#3.6">3.6</a>, <a href="#6.5.3.4">6.5.3.4</a> cexp2 function, <a href="#7.30.1">7.30.1</a>
33363 byte input/output functions, <a href="#7.21.1">7.21.1</a> cexpm1 function, <a href="#7.30.1">7.30.1</a>
33364 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>,
33366 <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>,
33368 c32rtomb function, <a href="#7.27.1.4">7.27.1.4</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="#6.10.8.2">6.10.8.2</a>, <a href="#7.27">7.27</a>
33369 cabs functions, <a href="#7.3.8.1">7.3.8.1</a>, <a href="#G.6">G.6</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="#6.10.8.2">6.10.8.2</a>, <a href="#7.27">7.27</a>
33370 type-generic macro for, <a href="#7.24">7.24</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>
33371 cacos functions, <a href="#7.3.5.1">7.3.5.1</a>, <a href="#G.6.1.1">G.6.1.1</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>
33372 type-generic macro for, <a href="#7.24">7.24</a> CHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
33373 cacosh functions, <a href="#7.3.6.1">7.3.6.1</a>, <a href="#G.6.2.1">G.6.2.1</a> character, <a href="#3.7">3.7</a>, <a href="#3.7.1">3.7.1</a>
33374 type-generic macro for, <a href="#7.24">7.24</a> character array initialization, <a href="#6.7.9">6.7.9</a>
33375 calendar time, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.2">7.26.2.2</a>, <a href="#7.26.2.3">7.26.2.3</a>, <a href="#7.26.2.4">7.26.2.4</a>, character case mapping functions, <a href="#7.4.2">7.4.2</a>
33376 <a href="#7.26.3.2">7.26.3.2</a>, <a href="#7.26.3.3">7.26.3.3</a>, <a href="#7.26.3.4">7.26.3.4</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>, wide character, <a href="#7.29.3.1">7.29.3.1</a>
33377 <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> extensible, <a href="#7.29.3.2">7.29.3.2</a>
33378 call by value, <a href="#6.5.2.2">6.5.2.2</a> character classification functions, <a href="#7.4.1">7.4.1</a>
33379 call_once function, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.1">7.25.2.1</a> wide character, <a href="#7.29.2.1">7.29.2.1</a>
33380 calloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.2">7.22.3.2</a> extensible, <a href="#7.29.2.2">7.29.2.2</a>
33381 carg functions, <a href="#7.3.9.1">7.3.9.1</a>, <a href="#G.6">G.6</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>
33382 carg type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> character display semantics, <a href="#5.2.2">5.2.2</a>
33383 carriage-return escape sequence (\r), <a href="#5.2.2">5.2.2</a>, character handling header, <a href="#7.4">7.4</a>, <a href="#7.11.1.1">7.11.1.1</a>
33384 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</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>
33385 carries a dependency, <a href="#5.1.2.4">5.1.2.4</a> wide character, <a href="#7.28.3">7.28.3</a>
33386 case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> character sets, <a href="#5.2.1">5.2.1</a>
33387 case mapping functions character string literal, see string literal
33388 character, <a href="#7.4.2">7.4.2</a> character type conversion, <a href="#6.3.1.1">6.3.1.1</a>
33389 wide character, <a href="#7.29.3.1">7.29.3.1</a> character types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.9">6.7.9</a>
33390 extensible, <a href="#7.29.3.2">7.29.3.2</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>
33391 casin functions, <a href="#7.3.5.2">7.3.5.2</a>, <a href="#G.6">G.6</a> cimag type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
33393 casinh functions, <a href="#7.3.6.2">7.3.6.2</a>, <a href="#G.6.2.2">G.6.2.2</a> classification functions
33396 cast operator (( )), <a href="#6.5.4">6.5.4</a> wide character, <a href="#7.29.2.1">7.29.2.1</a>
33397 catan functions, <a href="#7.3.5.3">7.3.5.3</a>, <a href="#G.6">G.6</a> extensible, <a href="#7.29.2.2">7.29.2.2</a>
33398 type-generic macro for, <a href="#7.24">7.24</a> clearerr function, <a href="#7.21.10.1">7.21.10.1</a>
33399 catanh functions, <a href="#7.3.6.3">7.3.6.3</a>, <a href="#G.6.2.3">G.6.2.3</a> clgamma function, <a href="#7.30.1">7.30.1</a>
33400 type-generic macro for, <a href="#7.24">7.24</a> clock function, <a href="#7.26.2.1">7.26.2.1</a>
33401 cbrt functions, <a href="#7.12.7.1">7.12.7.1</a>, <a href="#F.10.4.1">F.10.4.1</a> clock_t type, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.1">7.26.2.1</a>
33402 cbrt type-generic macro, <a href="#7.24">7.24</a> CLOCKS_PER_SEC macro, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.1">7.26.2.1</a>
33403 ccos functions, <a href="#7.3.5.4">7.3.5.4</a>, <a href="#G.6">G.6</a> clog functions, <a href="#7.3.7.2">7.3.7.2</a>, <a href="#G.6.3.2">G.6.3.2</a>
33404 <!--page 676 -->
33405 type-generic macro for, <a href="#7.24">7.24</a> string, <a href="#7.23.3">7.23.3</a>, <a href="#K.3.7.2">K.3.7.2</a>
33406 clog10 function, <a href="#7.30.1">7.30.1</a> wide string, <a href="#7.28.4.3">7.28.4.3</a>, <a href="#K.3.9.2.2">K.3.9.2.2</a>
33410 cnd_broadcast function, <a href="#7.25.3.1">7.25.3.1</a>, <a href="#7.25.3.5">7.25.3.5</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>,
33411 <a href="#7.25.3.6">7.25.3.6</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>
33412 cnd_destroy function, <a href="#7.25.3.2">7.25.3.2</a> conditional inclusion, <a href="#6.10.1">6.10.1</a>
33413 cnd_init function, <a href="#7.25.3.3">7.25.3.3</a> conditional operator (? :), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.15">6.5.15</a>
33414 cnd_signal function, <a href="#7.25.3.4">7.25.3.4</a>, <a href="#7.25.3.5">7.25.3.5</a>, conflict, <a href="#5.1.2.4">5.1.2.4</a>
33416 cnd_t type, <a href="#7.25.1">7.25.1</a> conj functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a>
33417 cnd_timedwait function, <a href="#7.25.3.5">7.25.3.5</a> conj type-generic macro, <a href="#7.24">7.24</a>
33418 cnd_wait function, <a href="#7.25.3.3">7.25.3.3</a>, <a href="#7.25.3.6">7.25.3.6</a> const type qualifier, <a href="#6.7.3">6.7.3</a>
33419 collating sequences, <a href="#5.2.1">5.2.1</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>
33420 colon punctuator (:), <a href="#6.7.2.1">6.7.2.1</a> constant expression, <a href="#6.6">6.6</a>, <a href="#F.8.4">F.8.4</a>
33421 comma operator (,), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.17">6.5.17</a> constants, <a href="#6.4.4">6.4.4</a>
33422 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>, as primary expression, <a href="#6.5.1">6.5.1</a>
33423 <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a> character, <a href="#6.4.4.4">6.4.4.4</a>
33424 command processor, <a href="#7.22.4.8">7.22.4.8</a> enumeration, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
33425 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> floating, <a href="#6.4.4.2">6.4.4.2</a>
33426 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> hexadecimal, <a href="#6.4.4.1">6.4.4.1</a>
33429 common real type, <a href="#6.3.1.8">6.3.1.8</a> constraint, <a href="#3.8">3.8</a>, <a href="#4">4</a>
33431 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>, consume operation, <a href="#5.1.2.4">5.1.2.4</a>
33432 <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> content of structure/union/enumeration, <a href="#6.7.2.3">6.7.2.3</a>
33433 string, <a href="#7.23.4">7.23.4</a> contiguity of allocated storage, <a href="#7.22.3">7.22.3</a>
33434 wide string, <a href="#7.28.4.4">7.28.4.4</a> continue statement, <a href="#6.8.6.2">6.8.6.2</a>
33435 comparison macros, <a href="#7.12.14">7.12.14</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>
33436 comparison, pointer, <a href="#6.5.8">6.5.8</a> control character, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a>
33437 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 wide character, <a href="#7.29.2">7.29.2</a>
33439 complement operator (~), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a> arithmetic operands, <a href="#6.3.1">6.3.1</a>
33442 complex numbers, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a> arrays, <a href="#6.3.2.1">6.3.2.1</a>
33443 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> boolean, <a href="#6.3.1.2">6.3.1.2</a>
33444 complex type domain, <a href="#6.2.5">6.2.5</a> boolean, characters, and integers, <a href="#6.3.1.1">6.3.1.1</a>
33445 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> by assignment, <a href="#6.5.16.1">6.5.16.1</a>
33446 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>, by return statement, <a href="#6.8.6.4">6.8.6.4</a>
33447 <a href="#7.3">7.3</a>, <a href="#7.24">7.24</a>, <a href="#7.30.1">7.30.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a> complex types, <a href="#6.3.1.6">6.3.1.6</a>
33449 components of time, <a href="#7.26.1">7.26.1</a>, <a href="#K.3.8.1">K.3.8.1</a> function, <a href="#6.3.2.1">6.3.2.1</a>
33450 composite type, <a href="#6.2.7">6.2.7</a> function argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
33451 compound assignment, <a href="#6.5.16.2">6.5.16.2</a> function designators, <a href="#6.3.2.1">6.3.2.1</a>
33452 compound literals, <a href="#6.5.2.5">6.5.2.5</a> function parameter, <a href="#6.9.1">6.9.1</a>
33454 compound-literal operator (( ){ }), <a href="#6.5.2.5">6.5.2.5</a> imaginary and complex, <a href="#G.4.3">G.4.3</a>
33456 <!--page 677 -->
33457 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>
33458 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="#7.24">7.24</a>
33459 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>
33460 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.24">7.24</a>
33461 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>
33462 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="#7.24">7.24</a>
33463 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>
33467 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>
33468 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="#7.30.2">7.30.2</a>
33469 extended, <a href="#7.28.6">7.28.6</a>, <a href="#K.3.9.3">K.3.9.3</a> current object, <a href="#6.7.9">6.7.9</a>
33470 restartable, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.6.3">7.28.6.3</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>
33472 restartable, <a href="#7.28.6.4">7.28.6.4</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="#7.22.4.6">7.22.4.6</a>,
33473 numeric, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> <a href="#7.23.5.8">7.23.5.8</a>, <a href="#7.23.6.2">7.23.6.2</a>, <a href="#7.26.3">7.26.3</a>, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.6.3">7.28.6.3</a>,
33474 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.28.4.1">7.28.4.1</a> <a href="#7.28.6.4">7.28.6.4</a>
33476 time, <a href="#7.26.3">7.26.3</a>, <a href="#K.3.8.2">K.3.8.2</a> date and time header, <a href="#7.26">7.26</a>, <a href="#K.3.8">K.3.8</a>
33477 wide character, <a href="#7.28.5">7.28.5</a> Daylight Saving Time, <a href="#7.26.1">7.26.1</a>
33478 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="#7.28.2.1">7.28.2.1</a>, DBL_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33480 conversion state, <a href="#7.22.7">7.22.7</a>, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.1.1">7.27.1.1</a>, DBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33481 <a href="#7.27.1.2">7.27.1.2</a>, <a href="#7.27.1.3">7.27.1.3</a>, <a href="#7.27.1.4">7.27.1.4</a>, <a href="#7.28.6">7.28.6</a>, DBL_HAS_SUBNORM macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33482 <a href="#7.28.6.2.1">7.28.6.2.1</a>, <a href="#7.28.6.3">7.28.6.3</a>, <a href="#7.28.6.3.2">7.28.6.3.2</a>, <a href="#7.28.6.3.3">7.28.6.3.3</a>, DBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33483 <a href="#7.28.6.4">7.28.6.4</a>, <a href="#7.28.6.4.1">7.28.6.4.1</a>, <a href="#7.28.6.4.2">7.28.6.4.2</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>
33484 <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>
33486 conversion state functions, <a href="#7.28.6.2">7.28.6.2</a> DBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33488 string, <a href="#7.23.2">7.23.2</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>
33489 wide string, <a href="#7.28.4.2">7.28.4.2</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>
33490 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>
33492 copysign type-generic macro, <a href="#7.24">7.24</a> decimal-point character, <a href="#7.1.1">7.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
33493 correctly rounded result, <a href="#3.9">3.9</a> 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>,
33494 corresponding real type, <a href="#6.2.5">6.2.5</a> <a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#F.5">F.5</a>
33495 cos functions, <a href="#7.12.4.5">7.12.4.5</a>, <a href="#F.10.1.5">F.10.1.5</a> declaration specifiers, <a href="#6.7">6.7</a>
33496 cos type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> declarations, <a href="#6.7">6.7</a>
33497 cosh functions, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#F.10.2.4">F.10.2.4</a> function, <a href="#6.7.6.3">6.7.6.3</a>
33498 cosh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> pointer, <a href="#6.7.6.1">6.7.6.1</a>
33499 cpow functions, <a href="#7.3.8.2">7.3.8.2</a>, <a href="#G.6.4.1">G.6.4.1</a> structure/union, <a href="#6.7.2.1">6.7.2.1</a>
33501 cproj functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a> declarator, <a href="#6.7.6">6.7.6</a>
33503 creal functions, <a href="#7.3.9.6">7.3.9.6</a>, <a href="#G.6">G.6</a> declarator type derivation, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.6">6.7.6</a>
33504 creal type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
33506 csin functions, <a href="#7.3.5.5">7.3.5.5</a>, <a href="#G.6">G.6</a> default argument promotions, <a href="#6.5.2.2">6.5.2.2</a>
33507 type-generic macro for, <a href="#7.24">7.24</a> default initialization, <a href="#6.7.9">6.7.9</a>
33508 <!--page 678 -->
33509 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>
33510 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>
33511 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>
33514 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="#7.27.1.1">7.27.1.1</a>, <a href="#7.27.1.2">7.27.1.2</a>,
33515 derived declarator types, <a href="#6.2.5">6.2.5</a> <a href="#7.27.1.3">7.27.1.3</a>, <a href="#7.27.1.4">7.27.1.4</a>, <a href="#7.28.3.1">7.28.3.1</a>, <a href="#7.28.3.3">7.28.3.3</a>,
33516 derived types, <a href="#6.2.5">6.2.5</a> <a href="#7.28.6.3.2">7.28.6.3.2</a>, <a href="#7.28.6.3.3">7.28.6.3.3</a>, <a href="#7.28.6.4.1">7.28.6.4.1</a>, <a href="#7.28.6.4.2">7.28.6.4.2</a>,
33517 designated initializer, <a href="#6.7.9">6.7.9</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.3.9.3.1.1">K.3.9.3.1.1</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>,
33520 diagnostic message, <a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</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>,
33521 diagnostics, <a href="#5.1.1.3">5.1.1.3</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="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>,
33522 diagnostics header, <a href="#7.2">7.2</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="#7.28.3.1">7.28.3.1</a>,
33526 direct input/output functions, <a href="#7.21.8">7.21.8</a> endif preprocessing directive, <a href="#6.10.1">6.10.1</a>
33527 display device, <a href="#5.2.2">5.2.2</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>
33529 div_t type, <a href="#7.22">7.22</a> enumeration, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.2">6.7.2.2</a>
33530 division assignment operator (/=), <a href="#6.5.16.2">6.5.16.2</a> enumeration constant, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
33531 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> enumeration content, <a href="#6.7.2.3">6.7.2.3</a>
33532 do statement, <a href="#6.8.5.2">6.8.5.2</a> enumeration members, <a href="#6.7.2.2">6.7.2.2</a>
33533 documentation of implementation, <a href="#4">4</a> enumeration specifiers, <a href="#6.7.2.2">6.7.2.2</a>
33534 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 tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
33535 <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>, enumerator, <a href="#6.7.2.2">6.7.2.2</a>
33536 <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>, environment, <a href="#5">5</a>
33537 <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>, environment functions, <a href="#7.22.4">7.22.4</a>, <a href="#K.3.6.2">K.3.6.2</a>
33538 <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> 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>
33539 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> environmental considerations, <a href="#5.2">5.2</a>
33540 double _Complex type, <a href="#6.2.5">6.2.5</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>,
33541 double _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <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>,
33542 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.22.4.3">7.22.4.3</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
33543 double _Imaginary type, <a href="#G.2">G.2</a> 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>,
33544 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>, <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>,
33545 <a href="#7.28.2.2">7.28.2.2</a>, <a href="#F.2">F.2</a> <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>,
33546 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>, <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>,
33547 <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.28.1">7.28.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#7.28.2.4">7.28.2.4</a>,
33548 double-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.8">7.28.2.8</a>, <a href="#7.28.2.10">7.28.2.10</a>, <a href="#7.28.2.12">7.28.2.12</a>,
33549 double-quote escape sequence (\"), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.28.3.4">7.28.3.4</a>, <a href="#7.28.6.1.1">7.28.6.1.1</a>, <a href="#7.28.6.1.2">7.28.6.1.2</a>, <a href="#K.3.5.3.7">K.3.5.3.7</a>,
33550 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</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.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>,
33551 double_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> <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>,
33553 EDOM macro, <a href="#7.5">7.5</a>, <a href="#7.12.1">7.12.1</a>, see also domain error 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>
33555 EILSEQ macro, <a href="#7.5">7.5</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.27.1.1">7.27.1.1</a>, <a href="#7.27.1.2">7.27.1.2</a>, equality expressions, <a href="#6.5.9">6.5.9</a>
33556 <a href="#7.27.1.3">7.27.1.3</a>, <a href="#7.27.1.4">7.27.1.4</a>, <a href="#7.28.3.1">7.28.3.1</a>, <a href="#7.28.3.3">7.28.3.3</a>, equality operator (==), <a href="#6.5.9">6.5.9</a>
33557 <a href="#7.28.6.3.2">7.28.6.3.2</a>, <a href="#7.28.6.3.3">7.28.6.3.3</a>, <a href="#7.28.6.4.1">7.28.6.4.1</a>, <a href="#7.28.6.4.2">7.28.6.4.2</a>, 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>,
33558 see also encoding error <a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a>, see
33560 <!--page 679 -->
33561 erf functions, <a href="#7.12.8.1">7.12.8.1</a>, <a href="#F.10.5.1">F.10.5.1</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>
33562 erf type-generic macro, <a href="#7.24">7.24</a> exp2 type-generic macro, <a href="#7.24">7.24</a>
33563 erfc functions, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#F.10.5.2">F.10.5.2</a> explicit conversion, <a href="#6.3">6.3</a>
33564 erfc type-generic macro, <a href="#7.24">7.24</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>
33565 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 type-generic macro, <a href="#7.24">7.24</a>
33566 <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>, exponent part, <a href="#6.4.4.2">6.4.4.2</a>
33567 <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="#7.23.6.2">7.23.6.2</a>, <a href="#7.27.1.1">7.27.1.1</a>, exponential functions
33568 <a href="#7.27.1.2">7.27.1.2</a>, <a href="#7.27.1.3">7.27.1.3</a>, <a href="#7.27.1.4">7.27.1.4</a>, <a href="#7.28.3.1">7.28.3.1</a>, complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
33569 <a href="#7.28.3.3">7.28.3.3</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a>, <a href="#7.28.6.3.2">7.28.6.3.2</a>, real, <a href="#7.12.6">7.12.6</a>, <a href="#F.10.3">F.10.3</a>
33570 <a href="#7.28.6.3.3">7.28.6.3.3</a>, <a href="#7.28.6.4.1">7.28.6.4.1</a>, <a href="#7.28.6.4.2">7.28.6.4.2</a>, <a href="#J.5.17">J.5.17</a>, expression, <a href="#6.5">6.5</a>
33571 <a href="#K.3.1.3">K.3.1.3</a>, <a href="#K.3.7.4.2">K.3.7.4.2</a> assignment, <a href="#6.5.16">6.5.16</a>
33572 errno.h header, <a href="#7.5">7.5</a>, <a href="#7.30.3">7.30.3</a>, <a href="#K.3.2">K.3.2</a> cast, <a href="#6.5.4">6.5.4</a>
33573 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>, constant, <a href="#6.6">6.6</a>
33574 <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> evaluation, <a href="#5.1.2.3">5.1.2.3</a>
33576 domain, see domain error order of evaluation, see order of evaluation
33580 error conditions, <a href="#7.12.1">7.12.1</a> expression statement, <a href="#6.8.3">6.8.3</a>
33581 error functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.10.5">F.10.5</a> extended alignment, <a href="#6.2.8">6.2.8</a>
33582 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 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>
33583 <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 characters, <a href="#5.2.1">5.2.1</a>
33584 <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 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>,
33586 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> extended multibyte/wide character conversion
33587 error-handling functions, <a href="#7.21.10">7.21.10</a>, <a href="#7.23.6.2">7.23.6.2</a>, utilities, <a href="#7.28.6">7.28.6</a>, <a href="#K.3.9.3">K.3.9.3</a>
33588 <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> extensible wide character case mapping functions,
33590 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 classification functions,
33591 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> <a href="#7.29.2.2">7.29.2.2</a>
33592 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> extern storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.7.1">6.7.1</a>
33593 evaluation of expression, <a href="#5.1.2.3">5.1.2.3</a> external definition, <a href="#6.9">6.9</a>
33594 evaluation order, see order of evaluation external identifiers, underscore, <a href="#7.1.3">7.1.3</a>
33596 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> external name, <a href="#6.4.2.1">6.4.2.1</a>
33597 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> external object definitions, <a href="#6.9.2">6.9.2</a>
33598 exclusive OR operators
33599 bitwise (^), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a> 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>
33600 bitwise assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> fabs type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
33602 execution character set, <a href="#5.2.1">5.2.1</a> fclose function, <a href="#7.21.5.1">7.21.5.1</a>
33603 execution environment, <a href="#5">5</a>, <a href="#5.1.2">5.1.2</a>, see also fdim functions, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#F.10.9.1">F.10.9.1</a>
33605 execution sequence, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.8">6.8</a> FE_ALL_EXCEPT macro, <a href="#7.6">7.6</a>
33606 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>, FE_DFL_ENV macro, <a href="#7.6">7.6</a>
33607 <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a> FE_DIVBYZERO macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
33608 EXIT_FAILURE macro, <a href="#7.22">7.22</a>, <a href="#7.22.4.4">7.22.4.4</a> FE_DOWNWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
33609 EXIT_SUCCESS macro, <a href="#7.22">7.22</a>, <a href="#7.22.4.4">7.22.4.4</a> FE_INEXACT macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
33610 exp functions, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#F.10.3.1">F.10.3.1</a> FE_INVALID macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
33611 exp type-generic macro, <a href="#7.24">7.24</a> FE_OVERFLOW macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
33612 <!--page 680 -->
33613 FE_TONEAREST 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>,
33614 FE_TOWARDZERO 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>
33615 FE_UNDERFLOW 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>
33616 FE_UPWARD macro, <a href="#7.6">7.6</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>
33617 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 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>,
33618 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> <a href="#6.3.1.8">6.3.1.8</a>
33619 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> 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>,
33620 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> <a href="#7.28.4.1.1">7.28.4.1.1</a>
33621 feholdexcept function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.3">7.6.4.3</a>, float_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a>
33622 <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a> floating constant, <a href="#6.4.4.2">6.4.4.2</a>
33623 fence, <a href="#5.1.2.4">5.1.2.4</a> floating suffix, f or <a href="#F">F</a>, <a href="#6.4.4.2">6.4.4.2</a>
33624 fences, <a href="#7.17.4">7.17.4</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>,
33625 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>, <a href="#F">F</a>, <a href="#H">H</a> <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a>
33626 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>
33627 <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>,
33628 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
33629 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>
33630 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>
33631 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>
33632 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>
33633 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 exception, <a href="#7.6">7.6</a>, <a href="#7.6.2">7.6.2</a>, <a href="#F.10">F.10</a>
33634 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 number, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.2.5">6.2.5</a>
33635 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 rounding mode, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33636 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 status flag, <a href="#7.6">7.6</a>, <a href="#F.8.6">F.8.6</a>
33637 fexcept_t type, <a href="#7.6">7.6</a>, <a href="#F.3">F.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>
33638 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 type-generic macro, <a href="#7.24">7.24</a>
33639 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>, FLT_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33640 <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.8.1">7.21.8.1</a> FLT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33641 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> FLT_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33642 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> 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>,
33643 fgetwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.28.3.1">7.28.3.1</a>, <a href="#F.10.11">F.10.11</a>
33645 fgetws function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.2">7.28.3.2</a> FLT_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33646 field width, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a> FLT_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33648 access functions, <a href="#7.21.5">7.21.5</a>, <a href="#K.3.5.2">K.3.5.2</a> FLT_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33650 operations, <a href="#7.21.4">7.21.4</a>, <a href="#K.3.5.1">K.3.5.1</a> FLT_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33651 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>, FLT_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33652 <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>, 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>,
33653 <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>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>
33654 <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="#7.28.3.1">7.28.3.1</a>, 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>
33655 <a href="#7.28.3.3">7.28.3.3</a>, <a href="#7.28.3.10">7.28.3.10</a> FLT_TRUE_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33656 positioning functions, <a href="#7.21.9">7.21.9</a> 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>
33657 file scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.9">6.9</a> fma type-generic macro, <a href="#7.24">7.24</a>
33658 FILE type, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> fmax functions, <a href="#7.12.12.2">7.12.12.2</a>, <a href="#F.10.9.2">F.10.9.2</a>
33659 FILENAME_MAX macro, <a href="#7.21.1">7.21.1</a> fmax type-generic macro, <a href="#7.24">7.24</a>
33660 flags, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>, see also floating-point fmin functions, <a href="#7.12.12.3">7.12.12.3</a>, <a href="#F.10.9.3">F.10.9.3</a>
33662 flexible array member, <a href="#6.7.2.1">6.7.2.1</a> fmod functions, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#F.10.7.1">F.10.7.1</a>
33663 float _Complex type, <a href="#6.2.5">6.2.5</a> fmod type-generic macro, <a href="#7.24">7.24</a>
33664 <!--page 681 -->
33665 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="#K.3.5.3.7">K.3.5.3.7</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>
33666 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>, 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>,
33667 <a href="#K.3.5.1.1">K.3.5.1.1</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="#7.28.3.10">7.28.3.10</a>
33668 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>, 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>,
33669 <a href="#K.3.5.2.2">K.3.5.2.2</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="#7.28.3.10">7.28.3.10</a>
33670 for statement, <a href="#6.8.5">6.8.5</a>, <a href="#6.8.5.3">6.8.5.3</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>
33671 form-feed character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> full declarator, <a href="#6.7.6">6.7.6</a>
33672 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>, full expression, <a href="#6.8">6.8</a>
33675 formal parameter, <a href="#3.16">3.16</a> argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
33676 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>
33678 wide character, <a href="#7.28.2">7.28.2</a>, <a href="#K.3.9.1">K.3.9.1</a> library, <a href="#7.1.4">7.1.4</a>
33679 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>
33680 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>
33681 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>
33684 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>
33685 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>
33686 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>
33687 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>
33688 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>,
33689 FP_NAN macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> <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>
33690 FP_NORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> prototype scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.7.6.2">6.7.6.2</a>
33691 FP_SUBNORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> recursive call, <a href="#6.5.2.2">6.5.2.2</a>
33692 FP_ZERO macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> return, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a>
33693 fpclassify macro, <a href="#7.12.3.1">7.12.3.1</a>, <a href="#F.3">F.3</a> scope, <a href="#6.2.1">6.2.1</a>
33694 fpos_t type, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a> type, <a href="#6.2.5">6.2.5</a>
33695 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>, type conversion, <a href="#6.3.2.1">6.3.2.1</a>
33696 <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>, function specifiers, <a href="#6.7.4">6.7.4</a>
33697 <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#F.3">F.3</a>, <a href="#K.3.5.3.1">K.3.5.3.1</a> function type, <a href="#6.2.5">6.2.5</a>
33698 fprintf_s function, <a href="#K.3.5.3.1">K.3.5.3.1</a> function-call operator (( )), <a href="#6.5.2.2">6.5.2.2</a>
33699 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>, function-like macro, <a href="#6.10.3">6.10.3</a>
33700 <a href="#7.21.7.7">7.21.7.7</a>, <a href="#7.21.8.2">7.21.8.2</a> fundamental alignment, <a href="#6.2.8">6.2.8</a>
33701 fputs function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.4">7.21.7.4</a> future directions
33702 fputwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.28.3.3">7.28.3.3</a>, language, <a href="#6.11">6.11</a>
33704 fputws function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.4">7.28.3.4</a> fwide function, <a href="#7.21.2">7.21.2</a>, <a href="#7.28.3.5">7.28.3.5</a>
33705 fread function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.8.1">7.21.8.1</a> 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>,
33706 free function, <a href="#7.22.3.3">7.22.3.3</a>, <a href="#7.22.3.5">7.22.3.5</a> <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#7.28.2.3">7.28.2.3</a>, <a href="#7.28.2.5">7.28.2.5</a>,
33707 freestanding execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, <a href="#7.28.2.11">7.28.2.11</a>, <a href="#K.3.9.1.1">K.3.9.1.1</a>
33709 freopen function, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.5.4">7.21.5.4</a> fwrite function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.8.2">7.21.8.2</a>
33710 freopen_s function, <a href="#K.3.5.2.2">K.3.5.2.2</a> fwscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.2">7.28.2.2</a>,
33711 frexp functions, <a href="#7.12.6.4">7.12.6.4</a>, <a href="#F.10.3.4">F.10.3.4</a> <a href="#7.28.2.4">7.28.2.4</a>, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.12">7.28.2.12</a>, <a href="#7.28.3.10">7.28.3.10</a>,
33713 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>, fwscanf_s function, <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>,
33714 <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> <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>
33716 <!--page 682 -->
33717 gamma functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.10.5">F.10.5</a> name spaces, <a href="#6.2.3">6.2.3</a>
33718 general utilities, <a href="#7.22">7.22</a>, <a href="#K.3.6">K.3.6</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>
33719 wide string, <a href="#7.28.4">7.28.4</a>, <a href="#K.3.9.2">K.3.9.2</a> scope, <a href="#6.2.1">6.2.1</a>
33720 general wide string utilities, <a href="#7.28.4">7.28.4</a>, <a href="#K.3.9.2">K.3.9.2</a> type, <a href="#6.2.5">6.2.5</a>
33722 generic selection, <a href="#6.5.1.1">6.5.1.1</a> identifier nondigit, <a href="#6.4.2.1">6.4.2.1</a>
33723 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>
33724 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>,
33725 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>,
33729 getwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.6">7.28.3.6</a>, <a href="#7.28.3.7">7.28.3.7</a> IEEE floating-point arithmetic standard, see
33730 getwchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.7">7.28.3.7</a> IEC 60559, ANSI/IEEE 754,
33732 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>,
33733 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>
33735 greater-than operator (>), <a href="#6.5.8">6.5.8</a> ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a>
33736 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>
33738 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>
33739 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 ilogb type-generic macro, <a href="#7.24">7.24</a>
33740 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> imaginary macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a>
33742 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> imaginary type domain, <a href="#G.2">G.2</a>
33745 (\x hexadecimal digits), <a href="#6.4.4.4">6.4.4.4</a> imaxdiv function, <a href="#7.8">7.8</a>, <a href="#7.8.2.2">7.8.2.2</a>
33747 horizontal-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> implementation, <a href="#3.12">3.12</a>
33748 horizontal-tab escape sequence (\r), <a href="#7.29.2.1.3">7.29.2.1.3</a> 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>,
33749 horizontal-tab escape sequence (\t), <a href="#5.2.2">5.2.2</a>, <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
33750 <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> limits
33751 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> implementation-defined behavior, <a href="#3.4.1">3.4.1</a>, <a href="#4">4</a>, <a href="#J.3">J.3</a>
33752 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>, implementation-defined value, <a href="#3.19.1">3.19.1</a>
33753 <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#F.10">F.10</a> implicit conversion, <a href="#6.3">6.3</a>
33754 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>, implicit initialization, <a href="#6.7.9">6.7.9</a>
33755 <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#F.10">F.10</a> include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.2">6.10.2</a>
33756 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>, inclusive OR operators
33757 <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#F.10">F.10</a> bitwise (|), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a>
33759 complex, <a href="#7.3.6">7.3.6</a>, <a href="#G.6.2">G.6.2</a> incomplete type, <a href="#6.2.5">6.2.5</a>
33760 real, <a href="#7.12.5">7.12.5</a>, <a href="#F.10.2">F.10.2</a> increment operators, see arithmetic operators,
33761 hypot functions, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#F.10.4.3">F.10.4.3</a> increment and decrement
33762 hypot type-generic macro, <a href="#7.24">7.24</a> indeterminate value, <a href="#3.19.2">3.19.2</a>
33764 <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> <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,
33766 linkage, see linkage indirection operator (*), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>
33767 maximum length, <a href="#6.4.2.1">6.4.2.1</a> inequality operator (!=), <a href="#6.5.9">6.5.9</a>
33768 <!--page 683 -->
33769 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>
33770 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> inter-thread happens before, <a href="#5.1.2.4">5.1.2.4</a>
33771 initial position, <a href="#5.2.2">5.2.2</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>
33772 initial shift state, <a href="#5.2.1.2">5.2.1.2</a> internal linkage, <a href="#6.2.2">6.2.2</a>
33773 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 name, <a href="#6.4.2.1">6.4.2.1</a>
33776 initializer, <a href="#6.7.9">6.7.9</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>
33777 permitted form, <a href="#6.6">6.6</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>
33778 string literal, <a href="#6.3.2.1">6.3.2.1</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>,
33779 inline, <a href="#6.7.4">6.7.4</a> <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
33781 input failure, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.8">7.28.2.8</a>, <a href="#7.28.2.10">7.28.2.10</a>, INTN_MAX macros, <a href="#7.20.2.1">7.20.2.1</a>
33782 <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_MIN macros, <a href="#7.20.2.1">7.20.2.1</a>
33783 <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_t types, <a href="#7.20.1.1">7.20.1.1</a>
33784 <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> INTPTR_MAX macro, <a href="#7.20.2.4">7.20.2.4</a>
33786 character, <a href="#7.21.7">7.21.7</a>, <a href="#K.3.5.4">K.3.5.4</a> intptr_t type, <a href="#7.20.1.4">7.20.1.4</a>
33787 direct, <a href="#7.21.8">7.21.8</a> inttypes.h header, <a href="#7.8">7.8</a>, <a href="#7.30.4">7.30.4</a>
33788 formatted, <a href="#7.21.6">7.21.6</a>, <a href="#K.3.5.3">K.3.5.3</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>
33789 wide character, <a href="#7.28.2">7.28.2</a>, <a href="#K.3.9.1">K.3.9.1</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>
33791 formatted, <a href="#7.28.2">7.28.2</a>, <a href="#K.3.9.1">K.3.9.1</a> 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>,
33792 input/output header, <a href="#7.21">7.21</a>, <a href="#K.3.5">K.3.5</a> <a href="#7.4.1.11">7.4.1.11</a>
33793 input/output, device, <a href="#5.1.2.3">5.1.2.3</a> 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>,
33794 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> <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>
33795 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>, isfinite macro, <a href="#7.12.3.2">7.12.3.2</a>, <a href="#F.3">F.3</a>
33797 INT_FASTN_MAX macros, <a href="#7.20.2.3">7.20.2.3</a> isgreater macro, <a href="#7.12.14.1">7.12.14.1</a>, <a href="#F.3">F.3</a>
33798 INT_FASTN_MIN macros, <a href="#7.20.2.3">7.20.2.3</a> isgreaterequal macro, <a href="#7.12.14.2">7.12.14.2</a>, <a href="#F.3">F.3</a>
33799 int_fastN_t types, <a href="#7.20.1.3">7.20.1.3</a> isinf macro, <a href="#7.12.3.3">7.12.3.3</a>
33800 INT_LEASTN_MAX macros, <a href="#7.20.2.2">7.20.2.2</a> isless macro, <a href="#7.12.14.3">7.12.14.3</a>, <a href="#F.3">F.3</a>
33801 INT_LEASTN_MIN macros, <a href="#7.20.2.2">7.20.2.2</a> islessequal macro, <a href="#7.12.14.4">7.12.14.4</a>, <a href="#F.3">F.3</a>
33802 int_leastN_t types, <a href="#7.20.1.2">7.20.1.2</a> islessgreater macro, <a href="#7.12.14.5">7.12.14.5</a>, <a href="#F.3">F.3</a>
33803 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> 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>,
33804 INT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a> <a href="#7.4.2.2">7.4.2.2</a>
33805 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>, isnan macro, <a href="#7.12.3.4">7.12.3.4</a>, <a href="#F.3">F.3</a>
33807 integer character constant, <a href="#6.4.4.4">6.4.4.4</a> ISO 31-11, <a href="#2">2</a>, <a href="#3">3</a>
33808 integer constant, <a href="#6.4.4.1">6.4.4.1</a> ISO 4217, <a href="#2">2</a>, <a href="#7.11.2.1">7.11.2.1</a>
33809 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>, ISO 8601, <a href="#2">2</a>, <a href="#7.26.3.5">7.26.3.5</a>
33810 <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>, 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>
33812 integer conversion rank, <a href="#6.3.1.1">6.3.1.1</a> ISO/IEC 2382-1, <a href="#2">2</a>, <a href="#3">3</a>
33813 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>, ISO/IEC 646, <a href="#2">2</a>, <a href="#5.2.1.1">5.2.1.1</a>
33814 <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>, ISO/IEC 9945-2, <a href="#7.11">7.11</a>
33815 <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a> iso646.h header, <a href="#4">4</a>, <a href="#7.9">7.9</a> *
33816 integer suffix, <a href="#6.4.4.1">6.4.4.1</a> isprint function, <a href="#5.2.2">5.2.2</a>, <a href="#7.4.1.8">7.4.1.8</a>
33817 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>, 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>,
33819 integer types, <a href="#6.2.5">6.2.5</a>, <a href="#7.20">7.20</a> 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>,
33820 <!--page 684 -->
33821 <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>
33822 <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.28.2.2">7.28.2.2</a> LC_COLLATE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.4.3">7.23.4.3</a>,
33823 isunordered macro, <a href="#7.12.14.6">7.12.14.6</a>, <a href="#F.3">F.3</a> <a href="#7.28.4.4.2">7.28.4.4.2</a>
33824 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>,
33825 <a href="#7.4.2.2">7.4.2.2</a> <a href="#7.22.8">7.22.8</a>, <a href="#7.28.6">7.28.6</a>, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a>, <a href="#7.29.2.2.2">7.29.2.2.2</a>,
33826 iswalnum function, <a href="#7.29.2.1.1">7.29.2.1.1</a>, <a href="#7.29.2.1.9">7.29.2.1.9</a>, <a href="#7.29.3.2.1">7.29.3.2.1</a>, <a href="#7.29.3.2.2">7.29.3.2.2</a>, <a href="#K.3.6.4">K.3.6.4</a>, <a href="#K.3.6.5">K.3.6.5</a>
33827 <a href="#7.29.2.1.10">7.29.2.1.10</a>, <a href="#7.29.2.2.1">7.29.2.2.1</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>
33828 iswalpha function, <a href="#7.29.2.1.1">7.29.2.1.1</a>, <a href="#7.29.2.1.2">7.29.2.1.2</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>
33829 <a href="#7.29.2.2.1">7.29.2.2.1</a> LC_TIME macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.26.3.5">7.26.3.5</a>
33830 iswblank function, <a href="#7.29.2.1.3">7.29.2.1.3</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> lconv structure type, <a href="#7.11">7.11</a>
33831 iswcntrl function, <a href="#7.29.2.1.2">7.29.2.1.2</a>, <a href="#7.29.2.1.4">7.29.2.1.4</a>, LDBL_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33832 <a href="#7.29.2.1.7">7.29.2.1.7</a>, <a href="#7.29.2.1.11">7.29.2.1.11</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> LDBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33833 iswctype function, <a href="#7.29.2.2.1">7.29.2.2.1</a>, <a href="#7.29.2.2.2">7.29.2.2.2</a> LDBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33834 iswdigit function, <a href="#7.29.2.1.1">7.29.2.1.1</a>, <a href="#7.29.2.1.2">7.29.2.1.2</a>, LDBL_HAS_SUBNORM macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33835 <a href="#7.29.2.1.5">7.29.2.1.5</a>, <a href="#7.29.2.1.7">7.29.2.1.7</a>, <a href="#7.29.2.1.11">7.29.2.1.11</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> LDBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33836 iswgraph function, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.1.6">7.29.2.1.6</a>, LDBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33837 <a href="#7.29.2.1.10">7.29.2.1.10</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> LDBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33838 iswlower function, <a href="#7.29.2.1.2">7.29.2.1.2</a>, <a href="#7.29.2.1.7">7.29.2.1.7</a>, LDBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33839 <a href="#7.29.2.2.1">7.29.2.2.1</a>, <a href="#7.29.3.1.1">7.29.3.1.1</a>, <a href="#7.29.3.1.2">7.29.3.1.2</a> LDBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33840 iswprint function, <a href="#7.29.2.1.6">7.29.2.1.6</a>, <a href="#7.29.2.1.8">7.29.2.1.8</a>, LDBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33842 iswpunct function, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.1.2">7.29.2.1.2</a>, LDBL_TRUE_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
33843 <a href="#7.29.2.1.7">7.29.2.1.7</a>, <a href="#7.29.2.1.9">7.29.2.1.9</a>, <a href="#7.29.2.1.10">7.29.2.1.10</a>, ldexp functions, <a href="#7.12.6.6">7.12.6.6</a>, <a href="#F.10.3.6">F.10.3.6</a>
33844 <a href="#7.29.2.1.11">7.29.2.1.11</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> ldexp type-generic macro, <a href="#7.24">7.24</a>
33845 iswspace function, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>, ldiv function, <a href="#7.22.6.2">7.22.6.2</a>
33846 <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a>, <a href="#7.29.2.1.2">7.29.2.1.2</a>, <a href="#7.29.2.1.6">7.29.2.1.6</a>, ldiv_t type, <a href="#7.22">7.22</a>
33847 <a href="#7.29.2.1.7">7.29.2.1.7</a>, <a href="#7.29.2.1.9">7.29.2.1.9</a>, <a href="#7.29.2.1.10">7.29.2.1.10</a>, leading underscore in identifiers, <a href="#7.1.3">7.1.3</a>
33848 <a href="#7.29.2.1.11">7.29.2.1.11</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> left-shift assignment operator (<<=), <a href="#6.5.16.2">6.5.16.2</a>
33849 iswupper function, <a href="#7.29.2.1.2">7.29.2.1.2</a>, <a href="#7.29.2.1.11">7.29.2.1.11</a>, left-shift operator (<<), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
33850 <a href="#7.29.2.2.1">7.29.2.2.1</a>, <a href="#7.29.3.1.1">7.29.3.1.1</a>, <a href="#7.29.3.1.2">7.29.3.1.2</a> length
33851 iswxdigit function, <a href="#7.29.2.1.12">7.29.2.1.12</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> 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>
33852 isxdigit function, <a href="#7.4.1.12">7.4.1.12</a>, <a href="#7.11.1.1">7.11.1.1</a> 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>
33853 italic type convention, <a href="#3">3</a>, <a href="#6.1">6.1</a> identifier, <a href="#6.4.2.1">6.4.2.1</a>
33854 iteration statements, <a href="#6.8.5">6.8.5</a> internal name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
33855 length function, <a href="#7.22.7.1">7.22.7.1</a>, <a href="#7.23.6.3">7.23.6.3</a>, <a href="#7.28.4.6.1">7.28.4.6.1</a>,
33856 jmp_buf type, <a href="#7.13">7.13</a> <a href="#7.28.6.3.1">7.28.6.3.1</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>
33857 jump statements, <a href="#6.8.6">6.8.6</a> 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="#7.28.2.1">7.28.2.1</a>,
33859 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> less-than operator (<), <a href="#6.5.8">6.5.8</a>
33860 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> less-than-or-equal-to operator (<=), <a href="#6.5.8">6.5.8</a>
33861 known constant size, <a href="#6.2.5">6.2.5</a> letter, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a>
33863 L_tmpnam macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.4.4">7.21.4.4</a> lgamma functions, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#F.10.5.3">F.10.5.3</a>
33864 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> lgamma type-generic macro, <a href="#7.24">7.24</a>
33865 label name, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.3">6.2.3</a> library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7">7</a>, <a href="#K.3">K.3</a>
33872 <!--page 685 -->
33873 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>
33875 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>
33876 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>,
33877 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="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#F.2">F.2</a>
33878 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>,
33879 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>
33880 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>,
33881 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="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
33882 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>,
33883 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>
33884 <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>
33885 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>,
33886 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="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
33887 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>,
33888 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>
33889 <a href="#7.28.4.1.2">7.28.4.1.2</a> long long integer suffix, ll or LL, <a href="#6.4.4.1">6.4.4.1</a>
33890 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="#7.28.4.1.2">7.28.4.1.2</a>
33891 <a href="#7.28.4.1.2">7.28.4.1.2</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="#7.28.4.1.2">7.28.4.1.2</a>
33892 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>,
33894 llround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.10.6.7">F.10.6.7</a> loop body, <a href="#6.8.5">6.8.5</a>
33897 locale, <a href="#3.4.2">3.4.2</a> 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>
33898 locale-specific behavior, <a href="#3.4.2">3.4.2</a>, <a href="#J.4">J.4</a> lrint type-generic macro, <a href="#7.24">7.24</a>
33899 locale.h header, <a href="#7.11">7.11</a>, <a href="#7.30.5">7.30.5</a> lround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.10.6.7">F.10.6.7</a>
33900 localeconv function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a> lround type-generic macro, <a href="#7.24">7.24</a>
33901 localization, <a href="#7.11">7.11</a> 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>,
33903 localtime_s function, <a href="#K.3.8.2.4">K.3.8.2.4</a> 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>,
33904 log functions, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#F.10.3.7">F.10.3.7</a> <a href="#6.5.16.2">6.5.16.2</a>
33906 log10 functions, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#F.10.3.8">F.10.3.8</a> macro argument substitution, <a href="#6.10.3.1">6.10.3.1</a>
33908 log1p functions, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#F.10.3.9">F.10.3.9</a> library function, <a href="#7.1.4">7.1.4</a>
33909 log1p type-generic macro, <a href="#7.24">7.24</a> macro invocation, <a href="#6.10.3">6.10.3</a>
33910 log2 functions, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#F.10.3.10">F.10.3.10</a> macro name, <a href="#6.10.3">6.10.3</a>
33913 complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a> redefinition, <a href="#6.10.3">6.10.3</a>
33914 real, <a href="#7.12.6">7.12.6</a>, <a href="#F.10.3">F.10.3</a> scope, <a href="#6.10.3.5">6.10.3.5</a>
33915 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> macro parameter, <a href="#6.10.3">6.10.3</a>
33916 logb type-generic macro, <a href="#7.24">7.24</a> macro preprocessor, <a href="#6.10">6.10</a>
33918 AND (&&), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a> magnitude, complex, <a href="#7.3.8.1">7.3.8.1</a>
33919 negation (!), <a href="#6.5.3.3">6.5.3.3</a> 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>,
33920 OR (||), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a> <a href="#7.21.3">7.21.3</a>
33921 logical source lines, <a href="#5.1.1.2">5.1.1.2</a> 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>
33924 <!--page 686 -->
33925 real, <a href="#7.12.11">7.12.11</a>, <a href="#F.10.8">F.10.8</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>
33926 matching failure, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.8">7.28.2.8</a>, <a href="#7.28.2.10">7.28.2.10</a>, modifiable lvalue, <a href="#6.3.2.1">6.3.2.1</a>
33927 <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> modification order, <a href="#5.1.2.4">5.1.2.4</a>
33928 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="#7.24">7.24</a>, <a href="#F">F</a>, modulus functions, <a href="#7.12.6.12">7.12.6.12</a>
33929 <a href="#F.10">F.10</a>, <a href="#J.5.17">J.5.17</a> modulus, complex, <a href="#7.3.8.1">7.3.8.1</a>
33930 MATH_ERREXCEPT macro, <a href="#7.12">7.12</a>, <a href="#F.10">F.10</a> mtx_destroy function, <a href="#7.25.4.1">7.25.4.1</a>
33931 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> mtx_init function, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.4.2">7.25.4.2</a>
33932 MATH_ERRNO macro, <a href="#7.12">7.12</a> mtx_lock function, <a href="#7.25.4.3">7.25.4.3</a>
33934 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="#7.25.4.4">7.25.4.4</a>
33935 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="#7.25.4.5">7.25.4.5</a>
33936 <a href="#7.22.7.3">7.22.7.3</a>, <a href="#7.27.1.2">7.27.1.2</a>, <a href="#7.27.1.4">7.27.1.4</a>, <a href="#7.28.6.3.3">7.28.6.3.3</a>, mtx_unlock function, <a href="#7.25.4.3">7.25.4.3</a>, <a href="#7.25.4.4">7.25.4.4</a>,
33937 <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="#7.25.4.5">7.25.4.5</a>, <a href="#7.25.4.6">7.25.4.6</a>
33938 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>
33939 mblen function, <a href="#7.22.7.1">7.22.7.1</a>, <a href="#7.28.6.3">7.28.6.3</a> multibyte conversion functions
33940 mbrlen function, <a href="#7.28.6.3.1">7.28.6.3.1</a> wide character, <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a>
33941 mbrtoc16 function, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.27.1.1">7.27.1.1</a> extended, <a href="#7.28.6">7.28.6</a>, <a href="#K.3.9.3">K.3.9.3</a>
33942 mbrtoc32 function, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.27.1.3">7.27.1.3</a> restartable, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.6.3">7.28.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a>
33943 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>
33944 <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#7.28.6.3.1">7.28.6.3.1</a>, <a href="#7.28.6.3.2">7.28.6.3.2</a>, restartable, <a href="#7.28.6.4">7.28.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>
33945 <a href="#7.28.6.4.1">7.28.6.4.1</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> multibyte string, <a href="#7.1.1">7.1.1</a>
33946 mbsinit function, <a href="#7.28.6.2.1">7.28.6.2.1</a> multibyte/wide character conversion functions,
33947 mbsrtowcs function, <a href="#7.28.6.4.1">7.28.6.4.1</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a>
33948 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> extended, <a href="#7.28.6">7.28.6</a>, <a href="#K.3.9.3">K.3.9.3</a>
33949 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>, restartable, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.6.3">7.28.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a>
33950 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.27">7.27</a>, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.1">7.28.1</a>, <a href="#7.28.2.1">7.28.2.1</a>, multibyte/wide string conversion functions,
33951 <a href="#7.28.2.2">7.28.2.2</a>, <a href="#7.28.6">7.28.6</a>, <a href="#7.28.6.2.1">7.28.6.2.1</a>, <a href="#7.28.6.3">7.28.6.3</a>, <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a>
33952 <a href="#7.28.6.3.1">7.28.6.3.1</a>, <a href="#7.28.6.4">7.28.6.4</a> restartable, <a href="#7.28.6.4">7.28.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>
33953 mbstowcs function, <a href="#6.4.5">6.4.5</a>, <a href="#7.22.8.1">7.22.8.1</a>, <a href="#7.28.6.4">7.28.6.4</a> multidimensional array, <a href="#6.5.2.1">6.5.2.1</a>
33954 mbstowcs_s function, <a href="#K.3.6.5.1">K.3.6.5.1</a> multiplication assignment operator (*=), <a href="#6.5.16.2">6.5.16.2</a>
33955 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>, 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>,
33957 member access operators (. and ->), <a href="#6.5.2.3">6.5.2.3</a> multiplicative expressions, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
33959 memchr function, <a href="#7.23.5.1">7.23.5.1</a> n-char sequence, <a href="#7.22.1.3">7.22.1.3</a>
33960 memcmp function, <a href="#7.23.4">7.23.4</a>, <a href="#7.23.4.1">7.23.4.1</a> n-wchar sequence, <a href="#7.28.4.1.1">7.28.4.1.1</a>
33962 memcpy_s function, <a href="#K.3.7.1.1">K.3.7.1.1</a> 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>
33964 memmove_s function, <a href="#K.3.7.1.2">K.3.7.1.2</a> internal, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
33966 memory management functions, <a href="#7.22.3">7.22.3</a> structure/union member, <a href="#6.2.3">6.2.3</a>
33967 memory_order type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.3">7.17.3</a> name spaces, <a href="#6.2.3">6.2.3</a>
33968 memset function, <a href="#7.23.6.1">7.23.6.1</a>, <a href="#K.3.7.4.1">K.3.7.4.1</a> named label, <a href="#6.8.1">6.8.1</a>
33970 minimum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.10.9">F.10.9</a> 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>
33971 minus operator, unary, <a href="#6.5.3.3">6.5.3.3</a> NAN macro, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a>
33973 string, <a href="#7.23.6">7.23.6</a>, <a href="#K.3.7.4">K.3.7.4</a> 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>,
33974 wide string, <a href="#7.28.4.6">7.28.4.6</a>, <a href="#K.3.9.2.4">K.3.9.2.4</a> <a href="#F.10.6.3">F.10.6.3</a>
33975 mktime function, <a href="#7.26.2.3">7.26.2.3</a> nearbyint type-generic macro, <a href="#7.24">7.24</a>
33976 <!--page 687 -->
33977 nearest integer functions, <a href="#7.12.9">7.12.9</a>, <a href="#F.10.6">F.10.6</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>
33978 negation operator (!), <a href="#6.5.3.3">6.5.3.3</a> operations on files, <a href="#7.21.4">7.21.4</a>, <a href="#K.3.5.1">K.3.5.1</a>
33979 negative zero, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.12.11.1">7.12.11.1</a> operator, <a href="#6.4.6">6.4.6</a>
33980 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> operators, <a href="#6.5">6.5</a>
33981 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>, additive, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>
33983 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>, assignment, <a href="#6.5.16">6.5.16</a>
33986 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> 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>
33989 no-return function, <a href="#6.7.4">6.7.4</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>
33990 non-stop floating-point control mode, <a href="#7.6.4.2">7.6.4.2</a> relational, <a href="#6.5.8">6.5.8</a>
33991 nongraphic characters, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> shift, <a href="#6.5.7">6.5.7</a>
33994 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>
33998 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> bitwise exclusive (^), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a>
33999 padding of binary stream, <a href="#7.21.2">7.21.2</a> bitwise exclusive assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
34000 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="#7.23.1">7.23.1</a>, bitwise inclusive (|), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a>
34001 <a href="#7.26.1">7.26.1</a>, <a href="#7.28.1">7.28.1</a> bitwise inclusive assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
34002 null pointer, <a href="#6.3.2.3">6.3.2.3</a> logical (||), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a>
34004 null preprocessing directive, <a href="#6.10.7">6.10.7</a> order of allocated storage, <a href="#7.22.3">7.22.3</a>
34005 null statement, <a href="#6.8.3">6.8.3</a> 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>,
34007 number classification macros, <a href="#7.12">7.12</a>, <a href="#7.12.3.1">7.12.3.1</a> ordinary identifier name space, <a href="#6.2.3">6.2.3</a>
34008 numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> orientation of stream, <a href="#7.21.2">7.21.2</a>, <a href="#7.28.3.5">7.28.3.5</a>
34009 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.28.4.1">7.28.4.1</a> out-of-bounds store, <a href="#L.2.1">L.2.1</a>
34015 object-like macro, <a href="#6.10.3">6.10.3</a> bits, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.20.1.1">7.20.1.1</a>
34016 observable behavior, <a href="#5.1.2.3">5.1.2.3</a> structure/union, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.7.2.1">6.7.2.1</a>
34017 obsolescence, <a href="#6.11">6.11</a>, <a href="#7.30">7.30</a> parameter, <a href="#3.16">3.16</a>
34019 octal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.4">6.4.4.4</a> ellipsis, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.10.3">6.10.3</a>
34020 octal-character escape sequence (\octal digits), 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>
34024 once_flag type, <a href="#7.25.1">7.25.1</a> parameter type list, <a href="#6.7.6.3">6.7.6.3</a>
34025 ONCE_FLAG_INIT macro, <a href="#7.25.1">7.25.1</a> 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>
34026 ones' complement, <a href="#6.2.6.2">6.2.6.2</a> parenthesized expression, <a href="#6.5.1">6.5.1</a>
34027 operand, <a href="#6.4.6">6.4.6</a>, <a href="#6.5">6.5</a> parse state, <a href="#7.21.2">7.21.2</a>
34028 <!--page 688 -->
34030 permitted form of initializer, <a href="#6.6">6.6</a> PRIcFASTN macros, <a href="#7.8.1">7.8.1</a>
34031 perror function, <a href="#7.21.10.4">7.21.10.4</a> PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a>
34032 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>
34033 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>
34035 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>
34036 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>,
34038 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>
34039 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>
34040 pointer to function, <a href="#6.5.2.2">6.5.2.2</a> printing wide character, <a href="#7.29.2">7.29.2</a>
34042 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>
34044 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>
34045 <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>
34046 <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>
34047 portability, <a href="#4">4</a>, <a href="#J">J</a> 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>
34048 position indicator, file, see file position indicator program structure, <a href="#5.1.1.1">5.1.1.1</a>
34049 positive difference, <a href="#7.12.12.1">7.12.12.1</a> 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>,
34050 positive difference functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.10.9">F.10.9</a> <a href="#5.1.2.3">5.1.2.3</a>
34051 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> program, conforming, <a href="#4">4</a>
34052 postfix expressions, <a href="#6.5.2">6.5.2</a> program, strictly conforming, <a href="#4">4</a>
34053 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> promotions
34054 pow functions, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#F.10.4.4">F.10.4.4</a> default argument, <a href="#6.5.2.2">6.5.2.2</a>
34055 pow type-generic macro, <a href="#7.24">7.24</a> integer, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.3.1.1">6.3.1.1</a>
34056 power functions prototype, see function prototype
34057 complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a> pseudo-random sequence functions, <a href="#7.22.2">7.22.2</a>
34058 real, <a href="#7.12.7">7.12.7</a>, <a href="#F.10.4">F.10.4</a> PTRDIFF_MAX macro, <a href="#7.20.3">7.20.3</a>
34060 pragma operator, <a href="#6.10.9">6.10.9</a> 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>,
34061 pragma preprocessing directive, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
34063 precedence of syntax rules, <a href="#5.1.1.2">5.1.1.2</a> 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>
34064 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="#7.28.2.1">7.28.2.1</a> putchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.8">7.21.7.8</a>
34065 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> puts function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.9">7.21.7.9</a>
34066 predefined macro names, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a> putwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.8">7.28.3.8</a>, <a href="#7.28.3.9">7.28.3.9</a>
34067 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> putwchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.9">7.28.3.9</a>
34068 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>
34069 preprocessing concatenation, <a href="#6.10.3.3">6.10.3.3</a> qsort function, <a href="#7.22.5">7.22.5</a>, <a href="#7.22.5.2">7.22.5.2</a>
34070 preprocessing directives, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10">6.10</a> 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>
34071 preprocessing file, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.10">6.10</a> qualified types, <a href="#6.2.5">6.2.5</a>
34072 preprocessing numbers, <a href="#6.4">6.4</a>, <a href="#6.4.8">6.4.8</a> qualified version of type, <a href="#6.2.5">6.2.5</a>
34074 #, <a href="#6.10.3.2">6.10.3.2</a> 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>,
34076 _Pragma, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a> quiet NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34078 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> 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>
34079 preprocessing translation unit, <a href="#5.1.1.1">5.1.1.1</a> 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>
34080 <!--page 689 -->
34081 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>
34083 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>,
34084 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="#7.28.3.10">7.28.3.10</a>
34085 <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>
34086 <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>
34087 <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>
34088 <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="#7.24">7.24</a>
34089 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>
34090 read-modify-write operations, <a href="#5.1.2.4">5.1.2.4</a> round type-generic macro, <a href="#7.24">7.24</a>
34091 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>
34092 <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>,
34093 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>,
34094 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>,
34095 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>,
34096 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>,
34097 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>,
34098 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>,
34099 recursion, <a href="#6.5.2.2">6.5.2.2</a> <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>,
34100 recursive function call, <a href="#6.5.2.2">6.5.2.2</a> <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>,
34101 redefinition of macro, <a href="#6.10.3">6.10.3</a> <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>,
34102 reentrancy, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</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>
34103 library functions, <a href="#7.1.4">7.1.4</a> 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>,
34104 referenced type, <a href="#6.2.5">6.2.5</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>
34105 register storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a> runtime-constraint, <a href="#3.18">3.18</a>
34106 relational expressions, <a href="#6.5.8">6.5.8</a> Runtime-constraint handling functions, <a href="#K.3.6.1">K.3.6.1</a>
34107 relaxed atomic operations, <a href="#5.1.2.4">5.1.2.4</a> rvalue, <a href="#6.3.2.1">6.3.2.1</a>
34110 release sequence, <a href="#5.1.2.4">5.1.2.4</a> save calling environment function, <a href="#7.13.1">7.13.1</a>
34111 reliability of data, interrupted, <a href="#5.1.2.3">5.1.2.3</a> scalar types, <a href="#6.2.5">6.2.5</a>
34112 remainder assignment operator (%=), <a href="#6.5.16.2">6.5.16.2</a> 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>
34113 remainder functions, <a href="#7.12.10">7.12.10</a>, <a href="#F.10.7">F.10.7</a> scalbln type-generic macro, <a href="#7.24">7.24</a>
34114 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>, 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>
34116 remainder operator (%), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a> 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>
34117 remainder type-generic macro, <a href="#7.24">7.24</a> 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>
34118 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> scanlist, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>
34119 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> scanset, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>
34120 remquo type-generic macro, <a href="#7.24">7.24</a> SCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
34121 rename function, <a href="#7.21.4.2">7.21.4.2</a> SCHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
34122 representations of types, <a href="#6.2.6">6.2.6</a> SCNcFASTN macros, <a href="#7.8.1">7.8.1</a>
34124 rescanning and replacement, <a href="#6.10.3.4">6.10.3.4</a> SCNcMAX macros, <a href="#7.8.1">7.8.1</a>
34125 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> SCNcN macros, <a href="#7.8.1">7.8.1</a>
34127 functions, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.6.3">7.28.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a> scope of identifier, <a href="#6.2.1">6.2.1</a>, <a href="#6.9.2">6.9.2</a>
34128 restartable multibyte/wide string conversion search functions
34129 functions, <a href="#7.28.6.4">7.28.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> string, <a href="#7.23.5">7.23.5</a>, <a href="#K.3.7.3">K.3.7.3</a>
34130 restore calling environment function, <a href="#7.13.2">7.13.2</a> utility, <a href="#7.22.5">7.22.5</a>, <a href="#K.3.6.3">K.3.6.3</a>
34131 restrict type qualifier, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a> wide string, <a href="#7.28.4.5">7.28.4.5</a>, <a href="#K.3.9.2.3">K.3.9.2.3</a>
34132 <!--page 690 -->
34133 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>
34134 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>
34135 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>
34136 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>
34137 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>
34138 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.h header, <a href="#7.14">7.14</a>, <a href="#7.30.6">7.30.6</a>
34139 <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</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>
34140 separate compilation, <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>
34141 separate translation, <a href="#5.1.1.1">5.1.1.1</a> signbit macro, <a href="#7.12.3.6">7.12.3.6</a>, <a href="#F.3">F.3</a>
34142 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>, 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>,
34143 <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>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</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>
34144 <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="#7.28.2">7.28.2</a>, <a href="#C">C</a>, <a href="#K.3.6.3">K.3.6.3</a> signed character, <a href="#6.3.1.1">6.3.1.1</a>
34145 sequenced after, see sequenced before 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>
34146 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 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>,
34147 <a href="#6.5.16">6.5.16</a>, see also indeterminately sequenced, <a href="#6.3.1.8">6.3.1.8</a>
34149 sequencing of statements, <a href="#6.8">6.8</a> significand part, <a href="#6.4.4.2">6.4.4.2</a>
34150 set_constraint_handler_s function, SIGSEGV macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>
34151 <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> SIGTERM macro, <a href="#7.14">7.14</a>
34152 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> simple assignment operator (=), <a href="#6.5.16.1">6.5.16.1</a>
34153 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> sin functions, <a href="#7.12.4.6">7.12.4.6</a>, <a href="#F.10.1.6">F.10.1.6</a>
34154 setjmp.h header, <a href="#7.13">7.13</a> sin type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
34155 setlocale function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a> single-byte character, <a href="#3.7.1">3.7.1</a>, <a href="#5.2.1.2">5.2.1.2</a>
34156 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>, single-byte/wide character conversion functions,
34157 <a href="#7.21.5.5">7.21.5.5</a>, <a href="#7.21.5.6">7.21.5.6</a> <a href="#7.28.6.1">7.28.6.1</a>
34159 shift expressions, <a href="#6.5.7">6.5.7</a> single-quote escape sequence (\'), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>
34161 shift states, <a href="#5.2.1.2">5.2.1.2</a> sinh functions, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#F.10.2.5">F.10.2.5</a>
34162 short identifier, character, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.3">6.4.3</a> sinh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
34163 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>, SIZE_MAX macro, <a href="#7.20.3">7.20.3</a>
34164 <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a> 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>,
34165 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>, <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="#7.23.1">7.23.1</a>, <a href="#7.26.1">7.26.1</a>, <a href="#7.27">7.27</a>,
34166 <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.28.1">7.28.1</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>,
34167 SHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> <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>
34168 SHRT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> 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>
34169 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>, snprintf function, <a href="#7.21.6.5">7.21.6.5</a>, <a href="#7.21.6.12">7.21.6.12</a>,
34170 <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>, <a href="#K.3.5.3.5">K.3.5.3.5</a>
34171 <a href="#7.21.7.7">7.21.7.7</a>, <a href="#7.28.3.6">7.28.3.6</a>, <a href="#7.28.3.8">7.28.3.8</a>, <a href="#F.8.1">F.8.1</a>, <a href="#F.9.1">F.9.1</a>, 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>
34172 <a href="#F.9.3">F.9.3</a> 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>
34173 SIG_ATOMIC_MAX macro, <a href="#7.20.3">7.20.3</a> sorting utility functions, <a href="#7.22.5">7.22.5</a>, <a href="#K.3.6.3">K.3.6.3</a>
34174 SIG_ATOMIC_MIN macro, <a href="#7.20.3">7.20.3</a> source character set, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>
34175 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>, source file, <a href="#5.1.1.1">5.1.1.1</a>
34176 <a href="#7.20.3">7.20.3</a> name, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8.1">6.10.8.1</a>
34177 SIG_DFL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> source file inclusion, <a href="#6.10.2">6.10.2</a>
34178 SIG_ERR macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> source lines, <a href="#5.1.1.2">5.1.1.2</a>
34179 SIG_IGN macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> source text, <a href="#5.1.1.2">5.1.1.2</a>
34180 SIGABRT macro, <a href="#7.14">7.14</a>, <a href="#7.22.4.1">7.22.4.1</a> 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>,
34181 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.5.17">J.5.17</a> <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.29.2.1.3">7.29.2.1.3</a>
34182 SIGILL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> 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>
34183 SIGINT macro, <a href="#7.14">7.14</a> 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>
34184 <!--page 691 -->
34185 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> do, <a href="#6.8.5.2">6.8.5.2</a>
34188 sscanf function, <a href="#7.21.6.7">7.21.6.7</a>, <a href="#7.21.6.14">7.21.6.14</a> for, <a href="#6.8.5.3">6.8.5.3</a>
34189 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> goto, <a href="#6.8.6.1">6.8.6.1</a>
34190 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> if, <a href="#6.8.4.1">6.8.4.1</a>
34191 standard headers, <a href="#4">4</a>, <a href="#7.1.2">7.1.2</a> iteration, <a href="#6.8.5">6.8.5</a>
34193 <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>, labeled, <a href="#6.8.1">6.8.1</a>
34194 <a href="#7.24">7.24</a>, <a href="#7.30.1">7.30.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a> null, <a href="#6.8.3">6.8.3</a>
34195 <a href="#7.4"><ctype.h></a>, <a href="#7.4">7.4</a>, <a href="#7.30.2">7.30.2</a> return, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a>
34196 <a href="#7.5"><errno.h></a>, <a href="#7.5">7.5</a>, <a href="#7.30.3">7.30.3</a>, <a href="#K.3.2">K.3.2</a> selection, <a href="#6.8.4">6.8.4</a>
34197 <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>, <a href="#F">F</a>, <a href="#H">H</a> sequencing, <a href="#6.8">6.8</a>
34198 <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>, switch, <a href="#6.8.4.2">6.8.4.2</a>
34200 <a href="#7.8"><inttypes.h></a>, <a href="#7.8">7.8</a>, <a href="#7.30.4">7.30.4</a> static assertions, <a href="#6.7.10">6.7.10</a>
34201 <a href="#7.9"><iso646.h></a>, <a href="#4">4</a>, <a href="#7.9">7.9</a> static storage duration, <a href="#6.2.4">6.2.4</a>
34202 <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> 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>
34203 <a href="#7.11"><locale.h></a>, <a href="#7.11">7.11</a>, <a href="#7.30.5">7.30.5</a> 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>
34204 <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="#7.24">7.24</a>, <a href="#F">F</a>, <a href="#F.10">F.10</a>, static_assert declaration, <a href="#6.7.10">6.7.10</a>
34206 <a href="#7.13"><setjmp.h></a>, <a href="#7.13">7.13</a> stdalign.h header, <a href="#4">4</a>, <a href="#7.15">7.15</a>
34207 <a href="#7.14"><signal.h></a>, <a href="#7.14">7.14</a>, <a href="#7.30.6">7.30.6</a> 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>
34208 <a href="#7.15"><stdalign.h></a>, <a href="#4">4</a>, <a href="#7.15">7.15</a> 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>
34209 <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> stdbool.h header, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.30.7">7.30.7</a>, <a href="#H">H</a>
34210 <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> STDC, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a>
34211 <a href="#7.18"><stdbool.h></a>, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.30.7">7.30.7</a>, <a href="#H">H</a> 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>,
34212 <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>, <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>
34213 <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> 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>
34214 <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>, 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>,
34215 <a href="#7.30.8">7.30.8</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a> <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.28.2.12">7.28.2.12</a>, <a href="#7.28.3.7">7.28.3.7</a>, <a href="#K.3.5.3.4">K.3.5.3.4</a>,
34216 <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="#7.30.9">7.30.9</a>, <a href="#F">F</a>, <a href="#K.3.5">K.3.5</a> <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>
34217 <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="#7.30.10">7.30.10</a>, <a href="#F">F</a>, 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>,
34218 <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6">K.3.6</a> <a href="#7.30.8">7.30.8</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>
34219 <a href="#7.23"><string.h></a>, <a href="#7.23">7.23</a>, <a href="#7.30.11">7.30.11</a>, <a href="#K.3.7">K.3.7</a> 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="#7.30.9">7.30.9</a>, <a href="#F">F</a>, <a href="#K.3.5">K.3.5</a>
34220 <a href="#7.24"><tgmath.h></a>, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> 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="#7.30.10">7.30.10</a>, <a href="#F">F</a>,
34221 <a href="#7.25"><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="#7.25">7.25</a> <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6">K.3.6</a>
34222 <a href="#7.26"><time.h></a>, <a href="#7.26">7.26</a>, <a href="#K.3.8">K.3.8</a> 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>,
34223 <a href="#7.27"><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="#7.27">7.27</a> <a href="#7.21.7.8">7.21.7.8</a>, <a href="#7.21.7.9">7.21.7.9</a>, <a href="#7.28.2.11">7.28.2.11</a>, <a href="#7.28.3.9">7.28.3.9</a>
34224 <a href="#7.28"><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="#7.28">7.28</a>, <a href="#7.30.12">7.30.12</a>, storage duration, <a href="#6.2.4">6.2.4</a>
34225 <a href="#F">F</a>, <a href="#K.3.9">K.3.9</a> storage order of array, <a href="#6.5.2.1">6.5.2.1</a>
34226 <a href="#7.29"><wctype.h></a>, <a href="#7.29">7.29</a>, <a href="#7.30.13">7.30.13</a> 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>
34227 standard input stream, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> storage-class specifiers, <a href="#6.7.1">6.7.1</a>, <a href="#6.11.5">6.11.5</a>
34228 standard integer types, <a href="#6.2.5">6.2.5</a> strcat function, <a href="#7.23.3.1">7.23.3.1</a>
34229 standard output stream, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> strcat_s function, <a href="#K.3.7.2.1">K.3.7.2.1</a>
34230 standard signed integer types, <a href="#6.2.5">6.2.5</a> strchr function, <a href="#7.23.5.2">7.23.5.2</a>
34231 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> strcmp function, <a href="#7.23.4">7.23.4</a>, <a href="#7.23.4.2">7.23.4.2</a>
34232 statements, <a href="#6.8">6.8</a> strcoll function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.4.3">7.23.4.3</a>, <a href="#7.23.4.5">7.23.4.5</a>
34236 <!--page 692 -->
34237 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="#7.28.2.2">7.28.2.2</a>
34238 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>
34239 line buffered, <a href="#7.21.3">7.21.3</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
34241 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>
34242 standard input, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> struct tm, <a href="#7.26.1">7.26.1</a>
34244 unbuffered, <a href="#7.21.3">7.21.3</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
34245 strerror function, <a href="#7.21.10.4">7.21.10.4</a>, <a href="#7.23.6.2">7.23.6.2</a> content, <a href="#6.7.2.3">6.7.2.3</a>
34246 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> dot operator (.), <a href="#6.5.2.3">6.5.2.3</a>
34247 strerrorlen_s function, <a href="#K.3.7.4.3">K.3.7.4.3</a> initialization, <a href="#6.7.9">6.7.9</a>
34248 strftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.26.3">7.26.3</a>, <a href="#7.26.3.5">7.26.3.5</a>, member alignment, <a href="#6.7.2.1">6.7.2.1</a>
34249 <a href="#7.28.5.1">7.28.5.1</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> member name space, <a href="#6.2.3">6.2.3</a>
34250 stricter, <a href="#6.2.8">6.2.8</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>
34251 strictly conforming program, <a href="#4">4</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
34253 comparison functions, <a href="#7.23.4">7.23.4</a> tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
34254 concatenation functions, <a href="#7.23.3">7.23.3</a>, <a href="#K.3.7.2">K.3.7.2</a> type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a>
34255 conversion functions, <a href="#7.11.1.1">7.11.1.1</a> strxfrm function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.4.5">7.23.4.5</a>
34256 copying functions, <a href="#7.23.2">7.23.2</a>, <a href="#K.3.7.1">K.3.7.1</a> subnormal floating-point numbers, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34257 library function conventions, <a href="#7.23.1">7.23.1</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
34258 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> subtraction assignment operator (-=), <a href="#6.5.16.2">6.5.16.2</a>
34259 miscellaneous functions, <a href="#7.23.6">7.23.6</a>, <a href="#K.3.7.4">K.3.7.4</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>
34260 numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> suffix
34261 search functions, <a href="#7.23.5">7.23.5</a>, <a href="#K.3.7.3">K.3.7.3</a> floating constant, <a href="#6.4.4.2">6.4.4.2</a>
34262 string handling header, <a href="#7.23">7.23</a>, <a href="#K.3.7">K.3.7</a> integer constant, <a href="#6.4.4.1">6.4.4.1</a>
34263 string.h header, <a href="#7.23">7.23</a>, <a href="#7.30.11">7.30.11</a>, <a href="#K.3.7">K.3.7</a> switch body, <a href="#6.8.4.2">6.8.4.2</a>
34264 stringizing, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.9">6.10.9</a> switch case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
34265 strlen function, <a href="#7.23.6.3">7.23.6.3</a> switch default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
34266 strncat function, <a href="#7.23.3.2">7.23.3.2</a> switch statement, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
34267 strncat_s function, <a href="#K.3.7.2.2">K.3.7.2.2</a> swprintf function, <a href="#7.28.2.3">7.28.2.3</a>, <a href="#7.28.2.7">7.28.2.7</a>,
34268 strncmp function, <a href="#7.23.4">7.23.4</a>, <a href="#7.23.4.4">7.23.4.4</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>
34269 strncpy function, <a href="#7.23.2.4">7.23.2.4</a> 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>
34270 strncpy_s function, <a href="#K.3.7.1.4">K.3.7.1.4</a> swscanf function, <a href="#7.28.2.4">7.28.2.4</a>, <a href="#7.28.2.8">7.28.2.8</a>
34271 strnlen_s function, <a href="#K.3.7.4.4">K.3.7.4.4</a> 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>
34273 strpbrk function, <a href="#7.23.5.4">7.23.5.4</a> synchronization operation, <a href="#5.1.2.4">5.1.2.4</a>
34274 strrchr function, <a href="#7.23.5.5">7.23.5.5</a> synchronize with, <a href="#5.1.2.4">5.1.2.4</a>
34275 strspn function, <a href="#7.23.5.6">7.23.5.6</a> syntactic categories, <a href="#6.1">6.1</a>
34277 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>, syntax rule precedence, <a href="#5.1.1.2">5.1.1.2</a>
34278 <a href="#7.28.2.2">7.28.2.2</a>, <a href="#F.3">F.3</a> syntax summary, language, <a href="#A">A</a>
34279 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> system function, <a href="#7.22.4.8">7.22.4.8</a>
34281 strtok function, <a href="#7.23.5.8">7.23.5.8</a> tab characters, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
34282 strtok_s function, <a href="#K.3.7.3.1">K.3.7.3.1</a> tag compatibility, <a href="#6.2.7">6.2.7</a>
34283 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>, tag name space, <a href="#6.2.3">6.2.3</a>
34284 <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.28.2.2">7.28.2.2</a> tags, <a href="#6.7.2.3">6.7.2.3</a>
34285 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> tan functions, <a href="#7.12.4.7">7.12.4.7</a>, <a href="#F.10.1.7">F.10.1.7</a>
34286 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> tan type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
34287 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>, tanh functions, <a href="#7.12.5.6">7.12.5.6</a>, <a href="#F.10.2.6">F.10.2.6</a>
34288 <!--page 693 -->
34289 tanh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> toupper function, <a href="#7.4.2.2">7.4.2.2</a>
34290 temporary lifetime, <a href="#6.2.4">6.2.4</a> towctrans function, <a href="#7.29.3.2.1">7.29.3.2.1</a>, <a href="#7.29.3.2.2">7.29.3.2.2</a>
34291 tentative definition, <a href="#6.9.2">6.9.2</a> towlower function, <a href="#7.29.3.1.1">7.29.3.1.1</a>, <a href="#7.29.3.2.1">7.29.3.2.1</a>
34292 terms, <a href="#3">3</a> towupper function, <a href="#7.29.3.1.2">7.29.3.1.2</a>, <a href="#7.29.3.2.1">7.29.3.2.1</a>
34293 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> translation environment, <a href="#5">5</a>, <a href="#5.1.1">5.1.1</a>
34294 tgamma functions, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#F.10.5.4">F.10.5.4</a> translation limits, <a href="#5.2.4.1">5.2.4.1</a>
34295 tgamma type-generic macro, <a href="#7.24">7.24</a> translation phases, <a href="#5.1.1.2">5.1.1.2</a>
34296 tgmath.h header, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> translation unit, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.9">6.9</a>
34297 thrd_create function, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.5.1">7.25.5.1</a> trap, see perform a trap
34298 thrd_current function, <a href="#7.25.5.2">7.25.5.2</a> 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>,
34299 thrd_detach function, <a href="#7.25.5.3">7.25.5.3</a> <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.5.2.3">6.5.2.3</a>
34301 thrd_exit function, <a href="#7.25.5.5">7.25.5.5</a> complex, <a href="#7.3.5">7.3.5</a>, <a href="#G.6.1">G.6.1</a>
34302 thrd_join function, <a href="#7.25.5.6">7.25.5.6</a> real, <a href="#7.12.4">7.12.4</a>, <a href="#F.10.1">F.10.1</a>
34303 thrd_sleep function, <a href="#7.25.5.7">7.25.5.7</a> trigraph sequences, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1.1">5.2.1.1</a>
34305 thrd_t type, <a href="#7.25.1">7.25.1</a> trunc functions, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#F.10.6.8">F.10.6.8</a>
34306 thrd_yield function, <a href="#7.25.5.8">7.25.5.8</a> trunc type-generic macro, <a href="#7.24">7.24</a>
34307 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> 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>
34308 thread storage duration, <a href="#6.2.4">6.2.4</a>, <a href="#7.6">7.6</a> truncation toward zero, <a href="#6.5.5">6.5.5</a>
34309 threads header, <a href="#7.25">7.25</a> tss_create function, <a href="#7.25.6.1">7.25.6.1</a>
34310 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="#7.25">7.25</a> tss_delete function, <a href="#7.25.6.2">7.25.6.2</a>
34312 broken down, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.3">7.26.2.3</a>, <a href="#7.26.3">7.26.3</a>, <a href="#7.26.3.1">7.26.3.1</a>, tss_dtor_t type, <a href="#7.25.1">7.25.1</a>
34313 <a href="#7.26.3.3">7.26.3.3</a>, <a href="#7.26.3.4">7.26.3.4</a>, <a href="#7.26.3.5">7.26.3.5</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a>, tss_get function, <a href="#7.25.6.3">7.25.6.3</a>
34314 <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> tss_set function, <a href="#7.25.6.4">7.25.6.4</a>
34315 calendar, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.2">7.26.2.2</a>, <a href="#7.26.2.3">7.26.2.3</a>, <a href="#7.26.2.4">7.26.2.4</a>, tss_t type, <a href="#7.25.1">7.25.1</a>
34316 <a href="#7.26.3.2">7.26.3.2</a>, <a href="#7.26.3.3">7.26.3.3</a>, <a href="#7.26.3.4">7.26.3.4</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>, 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>
34317 <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> type category, <a href="#6.2.5">6.2.5</a>
34318 components, <a href="#7.26.1">7.26.1</a>, <a href="#K.3.8.1">K.3.8.1</a> type conversion, <a href="#6.3">6.3</a>
34319 conversion functions, <a href="#7.26.3">7.26.3</a>, <a href="#K.3.8.2">K.3.8.2</a> type definitions, <a href="#6.7.8">6.7.8</a>
34320 wide character, <a href="#7.28.5">7.28.5</a> type domain, <a href="#6.2.5">6.2.5</a>, <a href="#G.2">G.2</a>
34322 manipulation functions, <a href="#7.26.2">7.26.2</a> type punning, <a href="#6.5.2.3">6.5.2.3</a>
34323 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> type qualifiers, <a href="#6.7.3">6.7.3</a>
34325 time.h header, <a href="#7.26">7.26</a>, <a href="#K.3.8">K.3.8</a> type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
34327 TIME_UTC macro, <a href="#7.25.7.1">7.25.7.1</a> typedef storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.7.8">6.7.8</a>
34328 tm structure type, <a href="#7.26.1">7.26.1</a>, <a href="#7.28.1">7.28.1</a>, <a href="#K.3.8.1">K.3.8.1</a> types, <a href="#6.2.5">6.2.5</a>
34329 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> 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>,
34330 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> <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>
34331 tmpfile function, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.22.4.4">7.22.4.4</a> character, <a href="#6.7.9">6.7.9</a>
34332 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> 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>
34333 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>, complex, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a>
34335 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> const qualified, <a href="#6.7.3">6.7.3</a>
34336 token, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, see also preprocessing tokens conversions, <a href="#6.3">6.3</a>
34338 token pasting, <a href="#6.10.3.3">6.10.3.3</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
34339 tolower function, <a href="#7.4.2.1">7.4.2.1</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
34340 <!--page 694 -->
34341 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="#7.27">7.27</a> universal character name, <a href="#6.4.3">6.4.3</a>
34342 UCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> unnormalized floating-point numbers, <a href="#5.2.4.2.2">5.2.4.2.2</a>
34343 UINT_FASTN_MAX macros, <a href="#7.20.2.3">7.20.2.3</a> unqualified type, <a href="#6.2.5">6.2.5</a>
34344 uint_fastN_t types, <a href="#7.20.1.3">7.20.1.3</a> unqualified version of type, <a href="#6.2.5">6.2.5</a>
34345 uint_least16_t type, <a href="#7.27">7.27</a> 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
34348 uint_leastN_t types, <a href="#7.20.1.2">7.20.1.2</a> 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>
34349 UINT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> unsigned integer suffix, u or <a href="#U">U</a>, <a href="#6.4.4.1">6.4.4.1</a>
34350 UINTMAX_C macro, <a href="#7.20.4.2">7.20.4.2</a> 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>
34351 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> 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>,
34352 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>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
34353 <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a> 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>,
34354 UINTN_C macros, <a href="#7.20.4.1">7.20.4.1</a> <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
34355 UINTN_MAX macros, <a href="#7.20.2.1">7.20.2.1</a> unspecified behavior, <a href="#3.4.4">3.4.4</a>, <a href="#4">4</a>, <a href="#J.1">J.1</a>
34356 uintN_t types, <a href="#7.20.1.1">7.20.1.1</a> unspecified value, <a href="#3.19.3">3.19.3</a>
34357 UINTPTR_MAX macro, <a href="#7.20.2.4">7.20.2.4</a> uppercase letter, <a href="#5.2.1">5.2.1</a>
34358 uintptr_t type, <a href="#7.20.1.4">7.20.1.4</a> use of library functions, <a href="#7.1.4">7.1.4</a>
34359 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>, USHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
34360 <a href="#7.28.4.1.2">7.28.4.1.2</a> 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>,
34361 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>, <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>
34363 unary arithmetic operators, <a href="#6.5.3.3">6.5.3.3</a> UTF-32, <a href="#6.10.8.2">6.10.8.2</a>
34365 unary minus operator (-), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a> utilities, general, <a href="#7.22">7.22</a>, <a href="#K.3.6">K.3.6</a>
34366 unary operators, <a href="#6.5.3">6.5.3</a> wide string, <a href="#7.28.4">7.28.4</a>, <a href="#K.3.9.2">K.3.9.2</a>
34368 unbuffered stream, <a href="#7.21.3">7.21.3</a> 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>,
34369 undef preprocessing directive, <a href="#6.10.3.5">6.10.3.5</a>, <a href="#7.1.3">7.1.3</a>, <a href="#7.16.1.4">7.16.1.4</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>,
34370 <a href="#7.1.4">7.1.4</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>,
34371 undefined behavior, <a href="#3.4.3">3.4.3</a>, <a href="#4">4</a>, <a href="#J.2">J.2</a> <a href="#7.28.2.5">7.28.2.5</a>, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.7">7.28.2.7</a>, <a href="#7.28.2.8">7.28.2.8</a>,
34372 underscore character, <a href="#6.4.2.1">6.4.2.1</a> <a href="#7.28.2.9">7.28.2.9</a>, <a href="#7.28.2.10">7.28.2.10</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>,
34373 underscore, leading, in identifier, <a href="#7.1.3">7.1.3</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.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a>
34374 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>, 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>,
34375 <a href="#7.21.9.3">7.21.9.3</a> <a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.3">7.16.1.3</a>
34376 ungetwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.10">7.28.3.10</a> 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>,
34377 Unicode, <a href="#7.27">7.27</a>, see also char16_t type, <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>,
34378 char32_t type, wchar_t type <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>,
34379 Unicode required set, <a href="#6.10.8.2">6.10.8.2</a> <a href="#7.28.2.5">7.28.2.5</a>, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.7">7.28.2.7</a>, <a href="#7.28.2.8">7.28.2.8</a>,
34380 union <a href="#7.28.2.9">7.28.2.9</a>, <a href="#7.28.2.10">7.28.2.10</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>,
34381 arrow operator (->), <a href="#6.5.2.3">6.5.2.3</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.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a>
34382 content, <a href="#6.7.2.3">6.7.2.3</a> va_list type, <a href="#7.16">7.16</a>, <a href="#7.16.1.3">7.16.1.3</a>
34383 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> 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>,
34384 initialization, <a href="#6.7.9">6.7.9</a> <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>,
34385 member alignment, <a href="#6.7.2.1">6.7.2.1</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>,
34386 member name space, <a href="#6.2.3">6.2.3</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="#7.28.2.5">7.28.2.5</a>, <a href="#7.28.2.6">7.28.2.6</a>,
34387 member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a> <a href="#7.28.2.7">7.28.2.7</a>, <a href="#7.28.2.8">7.28.2.8</a>, <a href="#7.28.2.9">7.28.2.9</a>, <a href="#7.28.2.10">7.28.2.10</a>,
34388 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</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.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>,
34389 specifier, <a href="#6.7.2.1">6.7.2.1</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>
34390 tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a> value, <a href="#3.19">3.19</a>
34391 type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a> value bits, <a href="#6.2.6.2">6.2.6.2</a>
34392 <!--page 695 -->
34393 variable arguments, <a href="#6.10.3">6.10.3</a>, <a href="#7.16">7.16</a> vswscanf function, <a href="#7.28.2.8">7.28.2.8</a>
34394 variable arguments header, <a href="#7.16">7.16</a> vswscanf_s function, <a href="#K.3.9.1.10">K.3.9.1.10</a>
34395 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> vwprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.9">7.28.2.9</a>, <a href="#K.3.9.1.11">K.3.9.1.11</a>
34396 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> vwprintf_s function, <a href="#K.3.9.1.11">K.3.9.1.11</a>
34397 vertical-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> vwscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.10">7.28.2.10</a>, <a href="#7.28.3.10">7.28.3.10</a>
34398 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>, vwscanf_s function, <a href="#K.3.9.1.12">K.3.9.1.12</a>
34400 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> warnings, <a href="#I">I</a>
34401 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>, 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="#7.28">7.28</a>, <a href="#7.30.12">7.30.12</a>,
34402 <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="#F">F</a>, <a href="#K.3.9">K.3.9</a>
34403 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> WCHAR_MAX macro, <a href="#7.20.3">7.20.3</a>, <a href="#7.28.1">7.28.1</a>
34404 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>, WCHAR_MIN macro, <a href="#7.20.3">7.20.3</a>, <a href="#7.28.1">7.28.1</a>
34405 <a href="#K.3.5.3.14">K.3.5.3.14</a> 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>,
34406 vfwprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.5">7.28.2.5</a>, <a href="#K.3.9.1.6">K.3.9.1.6</a> <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="#7.28.1">7.28.1</a>,
34407 vfwprintf_s function, <a href="#K.3.9.1.6">K.3.9.1.6</a> <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
34408 vfwscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.3.10">7.28.3.10</a> wcrtomb function, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>,
34409 vfwscanf_s function, <a href="#K.3.9.1.7">K.3.9.1.7</a> <a href="#7.28.6.3.3">7.28.6.3.3</a>, <a href="#7.28.6.4.2">7.28.6.4.2</a>, <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>,
34411 visible sequence of side effects, <a href="#5.1.2.4">5.1.2.4</a> 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>
34412 visible side effect, <a href="#5.1.2.4">5.1.2.4</a> wcscat function, <a href="#7.28.4.3.1">7.28.4.3.1</a>
34414 void expression, <a href="#6.3.2.2">6.3.2.2</a> wcschr function, <a href="#7.28.4.5.1">7.28.4.5.1</a>
34415 void function parameter, <a href="#6.7.6.3">6.7.6.3</a> wcscmp function, <a href="#7.28.4.4.1">7.28.4.4.1</a>, <a href="#7.28.4.4.4">7.28.4.4.4</a>
34416 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>, wcscoll function, <a href="#7.28.4.4.2">7.28.4.4.2</a>, <a href="#7.28.4.4.4">7.28.4.4.4</a>
34418 void type conversion, <a href="#6.3.2.2">6.3.2.2</a> wcscpy_s function, <a href="#K.3.9.2.1.1">K.3.9.2.1.1</a>
34419 volatile storage, <a href="#5.1.2.3">5.1.2.3</a> wcscspn function, <a href="#7.28.4.5.2">7.28.4.5.2</a>
34420 volatile type qualifier, <a href="#6.7.3">6.7.3</a> wcsftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.28.5.1">7.28.5.1</a>
34421 volatile-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a> wcslen function, <a href="#7.28.4.6.1">7.28.4.6.1</a>
34422 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>, wcsncat function, <a href="#7.28.4.3.2">7.28.4.3.2</a>
34423 <a href="#K.3.5.3.10">K.3.5.3.10</a> wcsncat_s function, <a href="#K.3.9.2.2.2">K.3.9.2.2.2</a>
34424 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>, wcsncmp function, <a href="#7.28.4.4.3">7.28.4.4.3</a>
34425 <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> wcsncpy function, <a href="#7.28.4.2.2">7.28.4.2.2</a>
34426 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> wcsncpy_s function, <a href="#K.3.9.2.1.2">K.3.9.2.1.2</a>
34427 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>, wcsnlen_s function, <a href="#K.3.9.2.4.1">K.3.9.2.4.1</a>
34429 vsnprintf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.12">7.21.6.12</a>, wcsrchr function, <a href="#7.28.4.5.4">7.28.4.5.4</a>
34430 <a href="#K.3.5.3.12">K.3.5.3.12</a> wcsrtombs function, <a href="#7.28.6.4.2">7.28.6.4.2</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>
34431 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>, 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>
34432 <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> wcsspn function, <a href="#7.28.4.5.5">7.28.4.5.5</a>
34433 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> wcsstr function, <a href="#7.28.4.5.6">7.28.4.5.6</a>
34434 vsprintf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.13">7.21.6.13</a>, wcstod function, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>
34436 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>, wcstof function, <a href="#7.28.4.1.1">7.28.4.1.1</a>
34437 <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> wcstoimax function, <a href="#7.8.2.4">7.8.2.4</a>
34438 vsscanf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.14">7.21.6.14</a> wcstok function, <a href="#7.28.4.5.7">7.28.4.5.7</a>
34439 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>, wcstok_s function, <a href="#K.3.9.2.3.1">K.3.9.2.3.1</a>
34440 <a href="#K.3.5.3.14">K.3.5.3.14</a> 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="#7.28.2.2">7.28.2.2</a>,
34441 vswprintf function, <a href="#7.28.2.7">7.28.2.7</a>, <a href="#K.3.9.1.8">K.3.9.1.8</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a>
34443 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="#7.28.4.1.2">7.28.4.1.2</a>
34444 <!--page 696 -->
34445 wcstombs function, <a href="#7.22.8.2">7.22.8.2</a>, <a href="#7.28.6.4">7.28.6.4</a> <a href="#7.29.1">7.29.1</a>
34446 wcstombs_s function, <a href="#K.3.6.5.2">K.3.6.5.2</a> wmemchr function, <a href="#7.28.4.5.8">7.28.4.5.8</a>
34447 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="#7.28.2.2">7.28.2.2</a>, wmemcmp function, <a href="#7.28.4.4.5">7.28.4.4.5</a>
34449 wcstoull function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a> wmemcpy_s function, <a href="#K.3.9.2.1.3">K.3.9.2.1.3</a>
34450 wcstoumax function, <a href="#7.8.2.4">7.8.2.4</a> wmemmove function, <a href="#7.28.4.2.4">7.28.4.2.4</a>
34451 wcsxfrm function, <a href="#7.28.4.4.4">7.28.4.4.4</a> wmemmove_s function, <a href="#K.3.9.2.1.4">K.3.9.2.1.4</a>
34452 wctob function, <a href="#7.28.6.1.2">7.28.6.1.2</a>, <a href="#7.29.2.1">7.29.2.1</a> wmemset function, <a href="#7.28.4.6.2">7.28.4.6.2</a>
34453 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="#7.28.6.3">7.28.6.3</a> wprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.9">7.28.2.9</a>, <a href="#7.28.2.11">7.28.2.11</a>,
34455 wctrans function, <a href="#7.29.3.2.1">7.29.3.2.1</a>, <a href="#7.29.3.2.2">7.29.3.2.2</a> wprintf_s function, <a href="#K.3.9.1.13">K.3.9.1.13</a>
34456 wctrans_t type, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.3.2.2">7.29.3.2.2</a> wscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.10">7.28.2.10</a>, <a href="#7.28.2.12">7.28.2.12</a>,
34457 wctype function, <a href="#7.29.2.2.1">7.29.2.2.1</a>, <a href="#7.29.2.2.2">7.29.2.2.2</a> <a href="#7.28.3.10">7.28.3.10</a>
34458 wctype.h header, <a href="#7.29">7.29</a>, <a href="#7.30.13">7.30.13</a> wscanf_s function, <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>
34461 WEOF macro, <a href="#7.28.1">7.28.1</a>, <a href="#7.28.3.1">7.28.3.1</a>, <a href="#7.28.3.3">7.28.3.3</a>, <a href="#7.28.3.6">7.28.3.6</a>, xor_eq macro, <a href="#7.9">7.9</a>
34462 <a href="#7.28.3.7">7.28.3.7</a>, <a href="#7.28.3.8">7.28.3.8</a>, <a href="#7.28.3.9">7.28.3.9</a>, <a href="#7.28.3.10">7.28.3.10</a>, xtime type, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.3.5">7.25.3.5</a>, <a href="#7.25.4.4">7.25.4.4</a>, <a href="#7.25.5.7">7.25.5.7</a>,
34463 <a href="#7.28.6.1.1">7.28.6.1.1</a>, <a href="#7.29.1">7.29.1</a> <a href="#7.25.7.1">7.25.7.1</a>
34464 while statement, <a href="#6.8.5.1">6.8.5.1</a> xtime_get function, <a href="#7.25.7.1">7.25.7.1</a>
34465 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>,
34484 wide string copying functions, <a href="#7.28.4.2">7.28.4.2</a>, <a href="#K.3.9.2.1">K.3.9.2.1</a>
34485 wide string literal, see string literal
34490 wide string search functions, <a href="#7.28.4.5">7.28.4.5</a>, <a href="#K.3.9.2.3">K.3.9.2.3</a>
34495 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="#7.28.1">7.28.1</a>, <a href="#7.28.2.1">7.28.2.1</a>,
34496 </pre>
34498 </body></html>