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13 </pre>
16 <pre>
19 ABSTRACT
23 (Cover sheet to be provided by ISO Secretariat.)
25 This International Standard specifies the form and establishes the interpretation of
26 programs expressed in the programming language C. Its purpose is to promote
27 portability, reliability, maintainability, and efficient execution of C language programs on
28 a variety of computing systems.
30 Clauses are included that detail the C language itself and the contents of the C language
31 execution library. Annexes summarize aspects of both of them, and enumerate factors
32 that influence the portability of C programs.
34 Although this International Standard is intended to guide knowledgeable C language
35 programmers as well as implementors of C language translation systems, the document
36 itself is not designed to serve as a tutorial.
38 Recipients of this draft are invited to submit, with their comments, notification of any
39 relevant patent rights of which they are aware and to provide supporting documentation.
41 Changes from the previous draft (N1256) are indicated by ''diff marks'' in the right
42 margin: deleted text is marked with ''*'', new or changed text with '' ''.
43 <!--page 2 -->
44 <!--page 3 -->
45 </pre>
48 <ul>
56 <ul>
58 <ul>
61 </ul>
63 <ul>
68 </ul>
69 </ul>
71 <ul>
74 <ul>
83 </ul>
85 <ul>
88 </ul>
90 <ul>
100 <!--page 4 -->
101 </ul>
103 <ul>
121 </ul>
124 <ul>
135 </ul>
137 <ul>
144 </ul>
146 <ul>
149 </ul>
151 <ul>
155 <!--page 5 -->
162 </ul>
164 <ul>
174 </ul>
175 </ul>
177 <ul>
179 <ul>
184 </ul>
186 <ul>
188 </ul>
190 <ul>
200 </ul>
202 <ul>
205 </ul>
208 <ul>
213 </ul>
215 <!--page 6 -->
217 <ul>
220 </ul>
224 <ul>
227 </ul>
229 <ul>
244 </ul>
246 <ul>
249 </ul>
251 <ul>
254 </ul>
257 <ul>
259 </ul>
261 <ul>
270 </ul>
274 <!--page 7 -->
275 <ul>
280 </ul>
282 <ul>
293 </ul>
295 <ul>
304 </ul>
306 <ul>
313 </ul>
316 <ul>
324 </ul>
326 <ul>
330 <!--page 8 -->
331 </ul>
333 <ul>
335 </ul>
337 <ul>
342 <ul>
349 </ul>
352 <ul>
357 </ul>
358 </ul>
359 <li><a href="#7.29"> 7.29 Wide character classification and mapping utilities <wctype.h></a>
360 <ul>
363 <ul>
366 </ul>
368 <ul>
371 </ul>
372 </ul>
374 <ul>
386 <!--page 9 -->
387 <li><a href="#7.30.12"> 7.30.12 Extended multibyte and wide character utilities <wchar.h></a>
388 <li><a href="#7.30.13"> 7.30.13 Wide character classification and mapping utilities <wctype.h></a>
389 </ul>
390 </ul>
392 <ul>
396 </ul>
398 <ul>
426 <li><a href="#B.28"> B.28 Wide character classification and mapping utilities <wctype.h></a>
427 </ul>
430 <ul>
433 </ul>
435 <!--page 10 -->
437 <ul>
448 <ul>
460 </ul>
461 </ul>
463 <ul>
468 <ul>
472 </ul>
474 <ul>
477 </ul>
479 <ul>
484 </ul>
486 </ul>
488 <ul>
492 <!--page 11 -->
493 </ul>
496 <ul>
502 </ul>
504 <ul>
508 <ul>
510 <ul>
515 </ul>
520 <ul>
525 </ul>
527 <ul>
533 </ul>
535 <ul>
540 </ul>
542 <ul>
545 </ul>
547 <ul>
550 <!--page 12 -->
552 </ul>
553 </ul>
554 </ul>
556 <ul>
560 </ul>
563 <!--page 13 -->
564 </ul>
568 ISO (the International Organization for Standardization) and IEC (the International
569 Electrotechnical Commission) form the specialized system for worldwide
570 standardization. National bodies that are member of ISO or IEC participate in the
571 development of International Standards through technical committees established by the
572 respective organization to deal with particular fields of technical activity. ISO and IEC
573 technical committees collaborate in fields of mutual interest. Other international
574 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
575 take part in the work.
577 International Standards are drafted in accordance with the rules given in the ISO/IEC
578 Directives, Part 2. This International Standard was drafted in accordance with the fifth
579 edition (2004).
581 In the field of information technology, ISO and IEC have established a joint technical
582 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
583 committee are circulated to national bodies for voting. Publication as an International
584 Standard requires approval by at least 75% of the national bodies casting a vote.
586 Attention is drawn to the possibility that some of the elements of this document may be
587 the subject of patent rights. ISO and IEC shall not be held responsible for identifying any
588 or all such patent rights.
590 This International Standard was prepared by Joint Technical Committee ISO/IEC JTC 1,
591 Information technology, Subcommittee SC 22, Programming languages, their
592 environments and system software interfaces. The Working Group responsible for this
593 standard (WG 14) maintains a site on the World Wide Web at http://www.open-
594 std.org/JTC1/SC22/WG14/ containing additional information relevant to this
595 standard such as a Rationale for many of the decisions made during its preparation and a
596 log of Defect Reports and Responses.
601 <ul>
602 <li> conditional (optional) features (including some that were previously mandatory)
603 <li> support for multiple threads of execution including an improved memory sequencing
607 <li> querying and specifying alignment of objects (<a href="#7.15"><stdalign.h></a>, <a href="#7.22"><stdlib.h></a>)
608 <li> Unicode characters and strings (<a href="#7.27"><uchar.h></a>) (originally specified in
610 <li> type-generic expressions
611 <!--page 14 -->
612 <li> static assertions
613 <li> anonymous structures and unions
614 <li> no-return functions
616 <li> support for opening files for exclusive access
618 <li> added the aligned_alloc, at_quick_exit, and quick_exit functions
620 <li> (conditional) support for bounds-checking interfaces (originally specified in
622 <li> (conditional) support for analyzability
623 </ul>
625 Major changes in the second edition included:
626 <ul>
627 <li> restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
628 in AMD1)
629 <li> wide character library support in <a href="#7.28"><wchar.h></a> and <a href="#7.29"><wctype.h></a> (originally
630 specified in AMD1)
631 <li> more precise aliasing rules via effective type
632 <li> restricted pointers
633 <li> variable length arrays
634 <li> flexible array members
635 <li> static and type qualifiers in parameter array declarators
638 <li> the long long int type and library functions
639 <li> increased minimum translation limits
641 <li> remove implicit int
642 <li> reliable integer division
643 <li> universal character names (\u and \U)
644 <li> extended identifiers
645 <li> hexadecimal floating-point constants and %a and %A printf/scanf conversion
646 specifiers
647 <!--page 15 -->
648 <li> compound literals
649 <li> designated initializers
650 <li> // comments
651 <li> extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.20"><stdint.h></a>
652 <li> remove implicit function declaration
653 <li> preprocessor arithmetic done in intmax_t/uintmax_t
654 <li> mixed declarations and code
655 <li> new block scopes for selection and iteration statements
656 <li> integer constant type rules
657 <li> integer promotion rules
658 <li> macros with a variable number of arguments
659 <li> the vscanf family of functions in <a href="#7.21"><stdio.h></a> and <a href="#7.28"><wchar.h></a>
661 <li> treatment of error conditions by math library functions (math_errhandling)
664 <li> trailing comma allowed in enum declaration
665 <li> %lf conversion specifier allowed in printf
666 <li> inline functions
669 <li> idempotent type qualifiers
670 <li> empty macro arguments
671 <li> new structure type compatibility rules (tag compatibility)
672 <li> additional predefined macro names
673 <li> _Pragma preprocessing operator
674 <li> standard pragmas
675 <li> __func__ predefined identifier
676 <li> va_copy macro
677 <li> additional strftime conversion specifiers
678 <li> LIA compatibility annex
679 <!--page 16 -->
680 <li> deprecate ungetc at the beginning of a binary file
681 <li> remove deprecation of aliased array parameters
682 <li> conversion of array to pointer not limited to lvalues
683 <li> relaxed constraints on aggregate and union initialization
684 <li> relaxed restrictions on portable header names
685 <li> return without expression not permitted in function that returns a value (and vice
686 versa)
687 </ul>
689 Annexes D, F, G, K, and L form a normative part of this standard; annexes A, B, C, E, H, *
690 I, J, the bibliography, and the index are for information only. In accordance with Part 2 of
691 the ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples
692 are also for information only.
693 <!--page 17 -->
697 With the introduction of new devices and extended character sets, new features may be
698 added to this International Standard. Subclauses in the language and library clauses warn
699 implementors and programmers of usages which, though valid in themselves, may
700 conflict with future additions.
702 Certain features are obsolescent, which means that they may be considered for
703 withdrawal in future revisions of this International Standard. They are retained because
704 of their widespread use, but their use in new implementations (for implementation
705 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.
707 This International Standard is divided into four major subdivisions:
708 <ul>
713 </ul>
715 Examples are provided to illustrate possible forms of the constructions described.
716 Footnotes are provided to emphasize consequences of the rules described in that
717 subclause or elsewhere in this International Standard. References are used to refer to
718 other related subclauses. Recommendations are provided to give advice or guidance to
719 implementors. Annexes provide additional information and summarize the information
720 contained in this International Standard. A bibliography lists documents that were
721 referred to during the preparation of the standard.
723 The language clause (clause 6) is derived from ''The C Reference Manual''.
726 <!--page 18 -->
727 <!--page 19 -->
736 This International Standard specifies the form and establishes the interpretation of
737 programs written in the C programming language.<sup><a href="#note1"><b>1)</b></a></sup> It specifies
738 <ul>
739 <li> the representation of C programs;
740 <li> the syntax and constraints of the C language;
741 <li> the semantic rules for interpreting C programs;
742 <li> the representation of input data to be processed by C programs;
743 <li> the representation of output data produced by C programs;
744 <li> the restrictions and limits imposed by a conforming implementation of C.
745 </ul>
747 This International Standard does not specify
748 <ul>
749 <li> the mechanism by which C programs are transformed for use by a data-processing
750 system;
751 <li> the mechanism by which C programs are invoked for use by a data-processing
752 system;
753 <li> the mechanism by which input data are transformed for use by a C program;
754 <li> the mechanism by which output data are transformed after being produced by a C
755 program;
756 <li> the size or complexity of a program and its data that will exceed the capacity of any
757 specific data-processing system or the capacity of a particular processor;
758 <li> all minimal requirements of a data-processing system that is capable of supporting a
759 conforming implementation.
762 <!--page 20 -->
763 </ul>
766 <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
767 data-processing systems. It is intended for use by implementors and programmers.
768 </small>
772 The following referenced documents are indispensable for the application of this
773 document. For dated references, only the edition cited applies. For undated references,
774 the latest edition of the referenced document (including any amendments) applies.
777 use in the physical sciences and technology.
780 interchange.
783 terms.
785 ISO 4217, Codes for the representation of currencies and funds.
787 ISO 8601, Data elements and interchange formats -- Information interchange --
788 Representation of dates and times.
790 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
791 Character Set (UCS).
795 <!--page 21 -->
799 For the purposes of this International Standard, the following definitions apply. Other
800 terms are defined where they appear in italic type or on the left side of a syntax rule.
801 Terms explicitly defined in this International Standard are not to be presumed to refer
802 implicitly to similar terms defined elsewhere. Terms not defined in this International
811 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
814 NOTE 2 ''Modify'' includes the case where the new value being stored is the same as the previous value.
817 NOTE 3 Expressions that are not evaluated do not access objects.
823 requirement that objects of a particular type be located on storage boundaries with
824 addresses that are particular multiples of a byte address
829 actual argument
830 actual parameter (deprecated)
831 expression in the comma-separated list bounded by the parentheses in a function call
832 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
833 by the parentheses in a function-like macro invocation
838 external appearance or action
843 unspecified behavior where each implementation documents how the choice is made
845 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
846 when a signed integer is shifted right.
852 behavior that depends on local conventions of nationality, culture, and language that each
853 implementation documents
854 <!--page 22 -->
856 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
857 characters other than the 26 lowercase Latin letters.
863 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
864 for which this International Standard imposes no requirements
866 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
867 results, to behaving during translation or program execution in a documented manner characteristic of the
868 environment (with or without the issuance of a diagnostic message), to terminating a translation or
869 execution (with the issuance of a diagnostic message).
872 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
878 use of an unspecified value, or other behavior where this International Standard provides
879 two or more possibilities and imposes no further requirements on which is chosen in any
880 instance
882 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
883 evaluated.
889 unit of data storage in the execution environment large enough to hold an object that may
890 have one of two values
892 NOTE It need not be possible to express the address of each individual bit of an object.
898 addressable unit of data storage large enough to hold any member of the basic character
899 set of the execution environment
901 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
904 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
905 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
906 bit.
913 representation of data
918 single-byte character
920 <!--page 23 -->
925 sequence of one or more bytes representing a member of the extended character set of
926 either the source or the execution environment
928 NOTE The extended character set is a superset of the basic character set.
934 bit representation that fits in an object of type wchar_t, capable of representing any
935 character in the current locale
940 restriction, either syntactic or semantic, by which the exposition of language elements is
941 to be interpreted
946 representation in the result format that is nearest in value, subject to the current rounding
947 mode, to what the result would be given unlimited range and precision
952 message belonging to an implementation-defined subset of the implementation's message
953 output
958 reference to a later subclause of this International Standard that contains additional
959 information relevant to this subclause
964 particular set of software, running in a particular translation environment under particular
965 control options, that performs translation of programs for, and supports execution of
966 functions in, a particular execution environment
971 restriction imposed upon programs by the implementation
976 either an object of scalar type, or a maximal sequence of adjacent bit-fields all having
977 nonzero width
978 <!--page 24 -->
980 NOTE 1 Two threads of execution can update and access separate memory locations without interfering
981 with each other.
984 NOTE 2 A bit-field and an adjacent non-bit-field member are in separate memory locations. The same
985 applies to two bit-fields, if one is declared inside a nested structure declaration and the other is not, or if the
986 two are separated by a zero-length bit-field declaration, or if they are separated by a non-bit-field member
987 declaration. It is not safe to concurrently update two non-atomic bit-fields in the same structure if all
988 members declared between them are also (non-zero-length) bit-fields, no matter what the sizes of those
989 intervening bit-fields happen to be.
992 EXAMPLE A structure declared as
993 <pre>
994 struct {
995 char a;
997 struct { int ee:8; } e;
998 }
999 </pre>
1000 contains four separate memory locations: The member a, and bit-fields d and e.ee are each separate
1001 memory locations, and can be modified concurrently without interfering with each other. The bit-fields b
1002 and c together constitute the fourth memory location. The bit-fields b and c cannot be concurrently
1003 modified, but b and a, for example, can be.
1009 region of data storage in the execution environment, the contents of which can represent
1010 values
1012 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>.
1018 formal parameter
1019 formal argument (deprecated)
1020 object declared as part of a function declaration or definition that acquires a value on
1021 entry to the function, or an identifier from the comma-separated list bounded by the
1022 parentheses immediately following the macro name in a function-like macro definition
1027 specification that is strongly recommended as being in keeping with the intent of the
1028 standard, but that may be impractical for some implementations
1033 requirement on a program when calling a library function
1035 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
1036 need not be diagnosed at translation time.
1039 NOTE 2 Implementations that support the extensions in <a href="#K">annex K</a> are required to verify that the runtime-
1040 constraints for a library function are not violated by the program; see <a href="#K.3.1.4">K.3.1.4</a>.
1041 <!--page 25 -->
1046 precise meaning of the contents of an object when interpreted as having a specific type
1051 unspecified value where each implementation documents how the choice is made
1056 either an unspecified value or a trap representation
1061 valid value of the relevant type where this International Standard imposes no
1062 requirements on which value is chosen in any instance
1064 NOTE An unspecified value cannot be a trap representation.
1070 an object representation that need not represent a value of the object type
1075 interrupt execution of the program such that no further operations are performed
1077 NOTE In this International Standard, when the word ''trap'' is not immediately followed by
1082 <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
1083 representation might perform a trap but is not required to (see <a href="#6.2.6.1">6.2.6.1</a>).
1084 </small>
1089 ceiling of x: the least integer greater than or equal to x
1097 floor of x: the greatest integer less than or equal to x
1104 <!--page 26 -->
1108 In this International Standard, ''shall'' is to be interpreted as a requirement on an
1109 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
1110 prohibition.
1112 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint or runtime-
1113 constraint is violated, the behavior is undefined. Undefined behavior is otherwise
1114 indicated in this International Standard by the words ''undefined behavior'' or by the
1115 omission of any explicit definition of behavior. There is no difference in emphasis among
1116 these three; they all describe ''behavior that is undefined''.
1118 A program that is correct in all other aspects, operating on correct data, containing
1119 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
1121 The implementation shall not successfully translate a preprocessing translation unit
1122 containing a #error preprocessing directive unless it is part of a group skipped by
1123 conditional inclusion.
1125 A strictly conforming program shall use only those features of the language and library
1126 specified in this International Standard.<sup><a href="#note3"><b>3)</b></a></sup> It shall not produce output dependent on any
1127 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
1128 minimum implementation limit.
1130 The two forms of conforming implementation are hosted and freestanding. A conforming
1131 hosted implementation shall accept any strictly conforming program. A conforming
1132 freestanding implementation shall accept any strictly conforming program that does not
1133 use complex types and in which the use of the features specified in the library clause
1134 (clause 7) is confined to the contents of the standard headers <a href="#7.7"><float.h></a>,
1135 <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>,
1136 <a href="#7.19"><stddef.h></a>, and <a href="#7.20"><stdint.h></a>. A conforming implementation may have extensions
1137 (including additional library functions), provided they do not alter the behavior of any
1142 <!--page 27 -->
1144 A conforming program is one that is acceptable to a conforming implementation.<sup><a href="#note5"><b>5)</b></a></sup>
1146 An implementation shall be accompanied by a document that defines all implementation-
1147 defined and locale-specific characteristics and all extensions.
1148 <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>),
1149 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>
1150 (<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>),
1151 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>
1152 (<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>).
1157 <!--page 28 -->
1160 <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
1161 by an appropriate conditional inclusion preprocessing directive using the related macro. For example:
1163 <pre>
1164 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
1165 /* ... */
1166 fesetround(FE_UPWARD);
1167 /* ... */
1168 #endif
1169 </pre>
1171 </small>
1172 <p><small><a name="note4" href="#note4">4)</a> This implies that a conforming implementation reserves no identifiers other than those explicitly
1173 reserved in this International Standard.
1174 </small>
1175 <p><small><a name="note5" href="#note5">5)</a> Strictly conforming programs are intended to be maximally portable among conforming
1176 implementations. Conforming programs may depend upon nonportable features of a conforming
1177 implementation.
1178 </small>
1182 An implementation translates C source files and executes C programs in two data-
1183 processing-system environments, which will be called the translation environment and
1184 the execution environment in this International Standard. Their characteristics define and
1185 constrain the results of executing conforming C programs constructed according to the
1186 syntactic and semantic rules for conforming implementations.
1188 have been noted.
1196 A C program need not all be translated at the same time. The text of the program is kept
1197 in units called source files, (or preprocessing files) in this International Standard. A
1198 source file together with all the headers and source files included via the preprocessing
1199 directive #include is known as a preprocessing translation unit. After preprocessing, a
1200 preprocessing translation unit is called a translation unit. Previously translated translation
1201 units may be preserved individually or in libraries. The separate translation units of a
1202 program communicate by (for example) calls to functions whose identifiers have external
1203 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
1204 of data files. Translation units may be separately translated and then later linked to
1205 produce an executable program.
1206 <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>),
1211 The precedence among the syntax rules of translation is specified by the following
1213 <ol>
1214 <li> Physical source file multibyte characters are mapped, in an implementation-
1215 defined manner, to the source character set (introducing new-line characters for
1216 end-of-line indicators) if necessary. Trigraph sequences are replaced by
1217 corresponding single-character internal representations.
1221 <!--page 29 -->
1222 <li> Each instance of a backslash character (\) immediately followed by a new-line
1223 character is deleted, splicing physical source lines to form logical source lines.
1224 Only the last backslash on any physical source line shall be eligible for being part
1225 of such a splice. A source file that is not empty shall end in a new-line character,
1226 which shall not be immediately preceded by a backslash character before any such
1227 splicing takes place.
1228 <li> The source file is decomposed into preprocessing tokens<sup><a href="#note7"><b>7)</b></a></sup> and sequences of
1229 white-space characters (including comments). A source file shall not end in a
1230 partial preprocessing token or in a partial comment. Each comment is replaced by
1231 one space character. New-line characters are retained. Whether each nonempty
1232 sequence of white-space characters other than new-line is retained or replaced by
1233 one space character is implementation-defined.
1234 <li> Preprocessing directives are executed, macro invocations are expanded, and
1235 _Pragma unary operator expressions are executed. If a character sequence that
1236 matches the syntax of a universal character name is produced by token
1237 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
1238 directive causes the named header or source file to be processed from phase 1
1239 through phase 4, recursively. All preprocessing directives are then deleted.
1240 <li> Each source character set member and escape sequence in character constants and
1241 string literals is converted to the corresponding member of the execution character
1242 set; if there is no corresponding member, it is converted to an implementation-
1244 <li> Adjacent string literal tokens are concatenated.
1245 <li> White-space characters separating tokens are no longer significant. Each
1246 preprocessing token is converted into a token. The resulting tokens are
1247 syntactically and semantically analyzed and translated as a translation unit.
1248 <li> All external object and function references are resolved. Library components are
1249 linked to satisfy external references to functions and objects not defined in the
1250 current translation. All such translator output is collected into a program image
1251 which contains information needed for execution in its execution environment.
1252 </ol>
1253 <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>),
1254 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>).
1258 <!--page 30 -->
1261 <p><small><a name="note6" href="#note6">6)</a> Implementations shall behave as if these separate phases occur, even though many are typically folded
1262 together in practice. Source files, translation units, and translated translation units need not
1263 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
1264 and any external representation. The description is conceptual only, and does not specify any
1265 particular implementation.
1266 </small>
1267 <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
1268 context-dependent. For example, see the handling of < within a #include preprocessing directive.
1269 </small>
1270 <p><small><a name="note8" href="#note8">8)</a> An implementation need not convert all non-corresponding source characters to the same execution
1271 character.
1272 </small>
1276 A conforming implementation shall produce at least one diagnostic message (identified in
1277 an implementation-defined manner) if a preprocessing translation unit or translation unit
1278 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1279 specified as undefined or implementation-defined. Diagnostic messages need not be
1282 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1283 <pre>
1284 char i;
1285 int i;
1286 </pre>
1287 because in those cases where wording in this International Standard describes the behavior for a construct
1288 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1292 <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
1293 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1294 valid program is still correctly translated. It may also successfully translate an invalid program.
1295 </small>
1299 Two execution environments are defined: freestanding and hosted. In both cases,
1300 program startup occurs when a designated C function is called by the execution
1301 environment. All objects with static storage duration shall be initialized (set to their
1302 initial values) before program startup. The manner and timing of such initialization are
1303 otherwise unspecified. Program termination returns control to the execution
1304 environment.
1305 <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>).
1309 In a freestanding environment (in which C program execution may take place without any
1310 benefit of an operating system), the name and type of the function called at program
1311 startup are implementation-defined. Any library facilities available to a freestanding
1312 program, other than the minimal set required by clause 4, are implementation-defined.
1314 The effect of program termination in a freestanding environment is implementation-
1315 defined.
1319 A hosted environment need not be provided, but shall conform to the following
1320 specifications if present.
1325 <!--page 31 -->
1329 The function called at program startup is named main. The implementation declares no
1330 prototype for this function. It shall be defined with a return type of int and with no
1331 parameters:
1332 <pre>
1333 int main(void) { /* ... */ }
1334 </pre>
1335 or with two parameters (referred to here as argc and argv, though any names may be
1336 used, as they are local to the function in which they are declared):
1337 <pre>
1338 int main(int argc, char *argv[]) { /* ... */ }
1339 </pre>
1340 or equivalent;<sup><a href="#note10"><b>10)</b></a></sup> or in some other implementation-defined manner.
1342 If they are declared, the parameters to the main function shall obey the following
1343 constraints:
1344 <ul>
1345 <li> The value of argc shall be nonnegative.
1346 <li> argv[argc] shall be a null pointer.
1348 argv[argc-1] inclusive shall contain pointers to strings, which are given
1349 implementation-defined values by the host environment prior to program startup. The
1350 intent is to supply to the program information determined prior to program startup
1351 from elsewhere in the hosted environment. If the host environment is not capable of
1352 supplying strings with letters in both uppercase and lowercase, the implementation
1353 shall ensure that the strings are received in lowercase.
1356 program name is not available from the host environment. If the value of argc is
1358 represent the program parameters.
1359 <li> The parameters argc and argv and the strings pointed to by the argv array shall
1360 be modifiable by the program, and retain their last-stored values between program
1361 startup and program termination.
1362 </ul>
1365 <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
1366 char ** argv, and so on.
1367 </small>
1371 In a hosted environment, a program may use all the functions, macros, type definitions,
1372 and objects described in the library clause (clause 7).
1377 <!--page 32 -->
1381 If the return type of the main function is a type compatible with int, a return from the
1382 initial call to the main function is equivalent to calling the exit function with the value
1383 returned by the main function as its argument;<sup><a href="#note11"><b>11)</b></a></sup> reaching the } that terminates the
1384 main function returns a value of 0. If the return type is not compatible with int, the
1385 termination status returned to the host environment is unspecified.
1386 <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>).
1389 <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
1390 will have ended in the former case, even where they would not have in the latter.
1391 </small>
1395 The semantic descriptions in this International Standard describe the behavior of an
1396 abstract machine in which issues of optimization are irrelevant.
1398 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1399 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
1400 the execution environment. Evaluation of an expression in general includes both value
1401 computations and initiation of side effects. Value computation for an lvalue expression
1402 includes determining the identity of the designated object.
1404 Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations
1405 executed by a single thread, which induces a partial order among those evaluations.
1406 Given any two evaluations A and B, if A is sequenced before B, then the execution of A
1407 shall precede the execution of B. (Conversely, if A is sequenced before B, then B is
1408 sequenced after A.) If A is not sequenced before or after B, then A and B are
1409 unsequenced. Evaluations A and B are indeterminately sequenced when A is sequenced
1410 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
1411 between the evaluation of expressions A and B implies that every value computation and
1412 side effect associated with A is sequenced before every value computation and side effect
1415 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1416 actual implementation need not evaluate part of an expression if it can deduce that its
1417 value is not used and that no needed side effects are produced (including any caused by
1419 <!--page 33 -->
1420 calling a function or accessing a volatile object).
1422 When the processing of the abstract machine is interrupted by receipt of a signal, the
1423 values of objects that are neither lock-free atomic objects nor of type volatile
1424 sig_atomic_t are unspecified, and the value of any object that is modified by the
1425 handler that is neither a lock-free atomic object nor of type volatile
1426 sig_atomic_t becomes undefined.
1428 The least requirements on a conforming implementation are:
1429 <ul>
1430 <li> Accesses to volatile objects are evaluated strictly according to the rules of the abstract
1431 machine.
1432 <li> At program termination, all data written into files shall be identical to the result that
1433 execution of the program according to the abstract semantics would have produced.
1434 <li> The input and output dynamics of interactive devices shall take place as specified in
1435 <a href="#7.21.3">7.21.3</a>. The intent of these requirements is that unbuffered or line-buffered output
1436 appear as soon as possible, to ensure that prompting messages actually appear prior to
1437 a program waiting for input.
1438 </ul>
1439 This is the observable behavior of the program.
1441 What constitutes an interactive device is implementation-defined.
1443 More stringent correspondences between abstract and actual semantics may be defined by
1444 each implementation.
1446 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1447 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1448 abstract semantics. The keyword volatile would then be redundant.
1450 Alternatively, an implementation might perform various optimizations within each translation unit, such
1451 that the actual semantics would agree with the abstract semantics only when making function calls across
1452 translation unit boundaries. In such an implementation, at the time of each function entry and function
1453 return where the calling function and the called function are in different translation units, the values of all
1454 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1455 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1456 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1457 type of implementation, objects referred to by interrupt service routines activated by the signal function
1458 would require explicit specification of volatile storage, as well as other implementation-defined
1459 restrictions.
1462 EXAMPLE 2 In executing the fragment
1463 <pre>
1464 char c1, c2;
1465 /* ... */
1466 c1 = c1 + c2;
1467 </pre>
1468 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1469 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1470 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1471 produce the same result, possibly omitting the promotions.
1472 <!--page 34 -->
1474 EXAMPLE 3 Similarly, in the fragment
1475 <pre>
1476 float f1, f2;
1477 double d;
1478 /* ... */
1479 f1 = f2 * d;
1480 </pre>
1481 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1482 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1483 were replaced by the constant 2.0, which has type double).
1486 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1487 semantics. Values are independent of whether they are represented in a register or in memory. For
1488 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1489 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1490 perform their specified conversion. For the fragment
1491 <pre>
1492 double d1, d2;
1493 float f;
1494 d1 = f = expression;
1495 d2 = (float) expression;
1496 </pre>
1497 the values assigned to d1 and d2 are required to have been converted to float.
1500 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1501 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1502 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1503 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1504 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1506 <pre>
1507 double x, y, z;
1508 /* ... */
1509 x = (x * y) * z; // not equivalent to x *= y * z;
1510 z = (x - y) + y ; // not equivalent to z = x;
1511 z = x + x * y; // not equivalent to z = x * (1.0 + y);
1513 </pre>
1516 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1517 <pre>
1518 int a, b;
1519 /* ... */
1521 </pre>
1522 the expression statement behaves exactly the same as
1523 <pre>
1525 </pre>
1526 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1527 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1528 which overflows produce an explicit trap and in which the range of values representable by an int is
1530 <pre>
1531 a = ((a + b) + 32765);
1532 </pre>
1533 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1534 while the original expression would not; nor can the expression be rewritten either as
1535 <!--page 35 -->
1536 <pre>
1537 a = ((a + 32765) + b);
1538 </pre>
1539 or
1540 <pre>
1541 a = (a + (b + 32765));
1542 </pre>
1543 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1544 in which overflow silently generates some value and where positive and negative overflows cancel, the
1545 above expression statement can be rewritten by the implementation in any of the above ways because the
1546 same result will occur.
1549 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1550 following fragment
1551 <pre>
1553 int sum;
1554 char *p;
1555 /* ... */
1557 </pre>
1558 the expression statement is grouped as if it were written as
1559 <pre>
1561 </pre>
1562 but the actual increment of p can occur at any time between the previous sequence point and the next
1563 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1564 value.
1566 <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
1570 <p><small><a name="note12" href="#note12">12)</a> The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
1571 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1572 values of floating-point operations. Implementations that support such floating-point state are
1573 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1574 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1575 effects matter, freeing the implementations in other cases.
1576 </small>
1577 <p><small><a name="note13" href="#note13">13)</a> The executions of unsequenced evaluations can interleave. Indeterminately sequenced evaluations
1578 cannot interleave, but can be executed in any order.
1579 </small>
1581 <h5><a name="5.1.2.4" href="#5.1.2.4">5.1.2.4 Multi-threaded executions and data races</a></h5>
1583 Under a hosted implementation, a program can have more than one thread of execution
1584 (or thread) running concurrently. The execution of each thread proceeds as defined by
1585 the remainder of this standard. The execution of the entire program consists of an
1586 execution of all of its threads.<sup><a href="#note14"><b>14)</b></a></sup> Under a freestanding implementation, it is
1587 implementation-defined whether a program can have more than one thread of execution.
1589 The value of an object visible to a thread T at a particular point is the initial value of the
1590 object, a value stored in the object by T , or a value stored in the object by another thread,
1591 according to the rules below.
1593 NOTE 1 In some cases, there may instead be undefined behavior. Much of this section is motivated by
1594 the desire to support atomic operations with explicit and detailed visibility constraints. However, it also
1595 implicitly supports a simpler view for more restricted programs.
1598 Two expression evaluations conflict if one of them modifies a memory location and the
1599 other one reads or modifies the same memory location.
1604 <!--page 36 -->
1606 The library defines a number of atomic operations (<a href="#7.17">7.17</a>) and operations on mutexes
1607 (<a href="#7.25.4">7.25.4</a>) that are specially identified as synchronization operations. These operations play
1608 a special role in making assignments in one thread visible to another. A synchronization
1609 operation on one or more memory locations is either an acquire operation, a release
1610 operation, both an acquire and release operation, or a consume operation. A
1611 synchronization operation without an associated memory location is a fence and can be
1612 either an acquire fence, a release fence, or both an acquire and release fence. In addition,
1613 there are relaxed atomic operations, which are not synchronization operations, and
1614 atomic read-modify-write operations, which have special characteristics.
1616 NOTE 2 For example, a call that acquires a mutex will perform an acquire operation on the locations
1617 composing the mutex. Correspondingly, a call that releases the same mutex will perform a release
1618 operation on those same locations. Informally, performing a release operation on A forces prior side effects
1619 on other memory locations to become visible to other threads that later perform an acquire or consume
1620 operation on A. We do not include relaxed atomic operations as synchronization operations although, like
1621 synchronization operations, they cannot contribute to data races.
1624 All modifications to a particular atomic object M occur in some particular total order,
1625 called the modification order of M. If A and B are modifications of an atomic object M,
1626 and A happens before B, then A shall precede B in the modification order of M, which is
1627 defined below.
1629 NOTE 3 This states that the modification orders must respect the ''happens before'' relation.
1632 NOTE 4 There is a separate order for each atomic object. There is no requirement that these can be
1633 combined into a single total order for all objects. In general this will be impossible since different threads
1634 may observe modifications to different variables in inconsistent orders.
1637 A release sequence on an atomic object M is a maximal contiguous sub-sequence of side
1638 effects in the modification order of M, where the first operation is a release and every
1639 subsequent operation either is performed by the same thread that performed the release or
1640 is an atomic read-modify-write operation.
1642 Certain library calls synchronize with other library calls performed by another thread. In
1643 particular, an atomic operation A that performs a release operation on an object M
1644 synchronizes with an atomic operation B that performs an acquire operation on M and
1645 reads a value written by any side effect in the release sequence headed by A.
1647 NOTE 5 Except in the specified cases, reading a later value does not necessarily ensure visibility as
1648 described below. Such a requirement would sometimes interfere with efficient implementation.
1651 NOTE 6 The specifications of the synchronization operations define when one reads the value written by
1652 another. For atomic variables, the definition is clear. All operations on a given mutex occur in a single total
1653 order. Each mutex acquisition ''reads the value written'' by the last mutex release.
1656 An evaluation A carries a dependency <sup><a href="#note15"><b>15)</b></a></sup> to an evaluation B if:
1659 <!--page 37 -->
1660 <ul>
1661 <li> the value of A is used as an operand of B, unless:
1662 <ul>
1663 <li> B is an invocation of the kill_dependency macro,
1667 <li> A is the left operand of a ? : operator, or
1669 <li> A is the left operand of a , operator;
1670 </ul>
1671 or
1672 <li> A writes a scalar object or bit-field M, B reads from M the value written by A, and A
1673 is sequenced before B, or
1674 <li> for some evaluation X, A carries a dependency to X and X carries a dependency to B.
1675 </ul>
1677 An evaluation A is dependency-ordered before<sup><a href="#note16"><b>16)</b></a></sup> an evaluation B if:
1678 <ul>
1679 <li> A performs a release operation on an atomic object M, and B performs a consume
1680 operation on M and reads a value written by any side effect in the release sequence
1681 headed by A, or
1682 <li> for some evaluation X, A is dependency-ordered before X and X carries a
1683 dependency to B.
1684 </ul>
1686 An evaluation A inter-thread happens before an evaluation B if A synchronizes with B, A
1687 is dependency-ordered before B, or, for some evaluation X:
1688 <ul>
1689 <li> A synchronizes with X and X is sequenced before B,
1690 <li> A is sequenced before X and X inter-thread happens before B, or
1691 <li> A inter-thread happens before X and X inter-thread happens before B.
1692 </ul>
1694 NOTE 7 The ''inter-thread happens before'' relation describes arbitrary concatenations of ''sequenced
1695 before'', ''synchronizes with'', and ''dependency-ordered before'' relationships, with two exceptions. The
1696 first exception is that a concatenation is not permitted to end with ''dependency-ordered before'' followed
1697 by ''sequenced before''. The reason for this limitation is that a consume operation participating in a
1698 ''dependency-ordered before'' relationship provides ordering only with respect to operations to which this
1699 consume operation actually carries a dependency. The reason that this limitation applies only to the end of
1700 such a concatenation is that any subsequent release operation will provide the required ordering for a prior
1701 consume operation. The second exception is that a concatenation is not permitted to consist entirely of
1702 ''sequenced before''. The reasons for this limitation are (1) to permit ''inter-thread happens before'' to be
1703 transitively closed and (2) the ''happens before'' relation, defined below, provides for relationships
1704 consisting entirely of ''sequenced before''.
1707 An evaluation A happens before an evaluation B if A is sequenced before B or A inter-
1708 thread happens before B.
1712 <!--page 38 -->
1714 A visible side effect A on an object M with respect to a value computation B of M
1715 satisfies the conditions:
1716 <ul>
1717 <li> A happens before B, and
1718 <li> there is no other side effect X to M such that A happens before X and X happens
1719 before B.
1720 </ul>
1721 The value of a non-atomic scalar object M, as determined by evaluation B, shall be the
1722 value stored by the visible side effect A.
1724 NOTE 8 If there is ambiguity about which side effect to a non-atomic object is visible, then there is a data
1725 race and the behavior is undefined.
1728 NOTE 9 This states that operations on ordinary variables are not visibly reordered. This is not actually
1729 detectable without data races, but it is necessary to ensure that data races, as defined here, and with suitable
1730 restrictions on the use of atomics, correspond to data races in a simple interleaved (sequentially consistent)
1731 execution.
1734 The visible sequence of side effects on an atomic object M, with respect to a value
1735 computation B of M, is a maximal contiguous sub-sequence of side effects in the
1736 modification order of M, where the first side effect is visible with respect to B, and for
1737 every subsequent side effect, it is not the case that B happens before it. The value of an
1738 atomic object M, as determined by evaluation B, shall be the value stored by some
1739 operation in the visible sequence of M with respect to B. Furthermore, if a value
1740 computation A of an atomic object M happens before a value computation B of M, and
1741 the value computed by A corresponds to the value stored by side effect X, then the value
1742 computed by B shall either equal the value computed by A, or be the value stored by side
1743 effect Y , where Y follows X in the modification order of M.
1745 NOTE 10 This effectively disallows compiler reordering of atomic operations to a single object, even if
1746 both operations are ''relaxed'' loads. By doing so, we effectively make the ''cache coherence'' guarantee
1747 provided by most hardware available to C atomic operations.
1750 NOTE 11 The visible sequence depends on the ''happens before'' relation, which in turn depends on the
1751 values observed by loads of atomics, which we are restricting here. The intended reading is that there must
1752 exist an association of atomic loads with modifications they observe that, together with suitably chosen
1753 modification orders and the ''happens before'' relation derived as described above, satisfy the resulting
1754 constraints as imposed here.
1757 The execution of a program contains a data race if it contains two conflicting actions in
1758 different threads, at least one of which is not atomic, and neither happens before the
1759 other. Any such data race results in undefined behavior.
1761 NOTE 12 It can be shown that programs that correctly use simple mutexes and
1762 memory_order_seq_cst operations to prevent all data races, and use no other synchronization
1763 operations, behave as though the operations executed by their constituent threads were simply interleaved,
1764 with each value computation of an object being the last value stored in that interleaving. This is normally
1765 referred to as ''sequential consistency''. However, this applies only to data-race-free programs, and data-
1766 race-free programs cannot observe most program transformations that do not change single-threaded
1767 program semantics. In fact, most single-threaded program transformations continue to be allowed, since
1768 any program that behaves differently as a result must contain undefined behavior.
1769 <!--page 39 -->
1771 NOTE 13 Compiler transformations that introduce assignments to a potentially shared memory location
1772 that would not be modified by the abstract machine are generally precluded by this standard, since such an
1773 assignment might overwrite another assignment by a different thread in cases in which an abstract machine
1774 execution would not have encountered a data race. This includes implementations of data member
1775 assignment that overwrite adjacent members in separate memory locations. We also generally preclude
1776 reordering of atomic loads in cases in which the atomics in question may alias, since this may violate the
1777 "visible sequence" rules.
1780 NOTE 14 Transformations that introduce a speculative read of a potentially shared memory location may
1781 not preserve the semantics of the program as defined in this standard, since they potentially introduce a data
1782 race. However, they are typically valid in the context of an optimizing compiler that targets a specific
1783 machine with well-defined semantics for data races. They would be invalid for a hypothetical machine that
1784 is not tolerant of races or provides hardware race detection.
1785 <!--page 40 -->
1788 <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
1789 atomic operations, for example, allow executions inconsistent with a simple interleaving as described
1790 below.
1791 </small>
1792 <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
1793 strictly intra-thread.
1794 </small>
1795 <p><small><a name="note16" href="#note16">16)</a> The ''dependency-ordered before'' relation is analogous to the ''synchronizes with'' relation, but uses
1796 release/consume in place of release/acquire.
1797 </small>
1803 Two sets of characters and their associated collating sequences shall be defined: the set in
1804 which source files are written (the source character set), and the set interpreted in the
1805 execution environment (the execution character set). Each set is further divided into a
1806 basic character set, whose contents are given by this subclause, and a set of zero or more
1807 locale-specific members (which are not members of the basic character set) called
1808 extended characters. The combined set is also called the extended character set. The
1809 values of the members of the execution character set are implementation-defined.
1811 In a character constant or string literal, members of the execution character set shall be
1812 represented by corresponding members of the source character set or by escape
1813 sequences consisting of the backslash \ followed by one or more characters. A byte with
1814 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1815 is used to terminate a character string.
1817 Both the basic source and basic execution character sets shall have the following
1818 members: the 26 uppercase letters of the Latin alphabet
1819 <pre>
1820 A B C D E F G H I J K L M
1821 N O P Q R S T U V W X Y Z
1822 </pre>
1823 the 26 lowercase letters of the Latin alphabet
1824 <pre>
1825 a b c d e f g h i j k l m
1826 n o p q r s t u v w x y z
1827 </pre>
1828 the 10 decimal digits
1829 <pre>
1830 0 1 2 3 4 5 6 7 8 9
1831 </pre>
1832 the following 29 graphic characters
1833 <pre>
1834 ! " # % & ' ( ) * + , - . / :
1835 ; < = > ? [ \ ] ^ _ { | } ~
1836 </pre>
1837 the space character, and control characters representing horizontal tab, vertical tab, and
1838 form feed. The representation of each member of the source and execution basic
1839 character sets shall fit in a byte. In both the source and execution basic character sets, the
1840 value of each character after 0 in the above list of decimal digits shall be one greater than
1841 the value of the previous. In source files, there shall be some way of indicating the end of
1842 each line of text; this International Standard treats such an end-of-line indicator as if it
1843 were a single new-line character. In the basic execution character set, there shall be
1844 control characters representing alert, backspace, carriage return, and new line. If any
1845 other characters are encountered in a source file (except in an identifier, a character
1846 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1847 <!--page 41 -->
1848 converted to a token), the behavior is undefined.
1849 <p><!--para 4 -->
1850 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1851 Standard the term does not include other characters that are letters in other alphabets.
1852 <p><!--para 5 -->
1853 The universal character name construct provides a way to name other characters.
1854 <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>),
1855 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>).
1858 <p><!--para 1 -->
1859 Before any other processing takes place, each occurrence of one of the following
1860 sequences of three characters (called trigraph sequences<sup><a href="#note17"><b>17)</b></a></sup>) is replaced with the
1861 corresponding single character.
1862 <pre>
1863 ??= # ??) ] ??! |
1864 ??( [ ??' ^ ??> }
1865 ??/ \ ??< { ??- ~
1866 </pre>
1867 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1868 above is not changed.
1869 <p><!--para 2 -->
1870 EXAMPLE 1
1871 <pre>
1872 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
1873 </pre>
1874 becomes
1875 <pre>
1876 #define arraycheck(a, b) a[b] || b[a]
1877 </pre>
1879 <p><!--para 3 -->
1880 EXAMPLE 2 The following source line
1881 <pre>
1883 </pre>
1884 becomes (after replacement of the trigraph sequence ??/)
1885 <pre>
1887 </pre>
1890 <p><b>Footnotes</b>
1891 <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
1892 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1893 </small>
1896 <p><!--para 1 -->
1897 The source character set may contain multibyte characters, used to represent members of
1898 the extended character set. The execution character set may also contain multibyte
1899 characters, which need not have the same encoding as for the source character set. For
1900 both character sets, the following shall hold:
1901 <ul>
1902 <li> The basic character set shall be present and each character shall be encoded as a
1903 single byte.
1904 <li> The presence, meaning, and representation of any additional members is locale-
1905 specific.
1907 <!--page 42 -->
1908 <li> A multibyte character set may have a state-dependent encoding, wherein each
1909 sequence of multibyte characters begins in an initial shift state and enters other
1910 locale-specific shift states when specific multibyte characters are encountered in the
1911 sequence. While in the initial shift state, all single-byte characters retain their usual
1912 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1913 in the sequence is a function of the current shift state.
1914 <li> A byte with all bits zero shall be interpreted as a null character independent of shift
1915 state. Such a byte shall not occur as part of any other multibyte character.
1916 </ul>
1917 <p><!--para 2 -->
1918 For source files, the following shall hold:
1919 <ul>
1920 <li> An identifier, comment, string literal, character constant, or header name shall begin
1921 and end in the initial shift state.
1922 <li> An identifier, comment, string literal, character constant, or header name shall consist
1923 of a sequence of valid multibyte characters.
1924 </ul>
1927 <p><!--para 1 -->
1928 The active position is that location on a display device where the next character output by
1929 the fputc function would appear. The intent of writing a printing character (as defined
1930 by the isprint function) to a display device is to display a graphic representation of
1931 that character at the active position and then advance the active position to the next
1932 position on the current line. The direction of writing is locale-specific. If the active
1933 position is at the final position of a line (if there is one), the behavior of the display device
1934 is unspecified.
1935 <p><!--para 2 -->
1936 Alphabetic escape sequences representing nongraphic characters in the execution
1937 character set are intended to produce actions on display devices as follows:
1938 \a (alert) Produces an audible or visible alert without changing the active position.
1939 \b (backspace) Moves the active position to the previous position on the current line. If
1940 <pre>
1941 the active position is at the initial position of a line, the behavior of the display
1942 device is unspecified.
1943 </pre>
1944 \f ( form feed) Moves the active position to the initial position at the start of the next
1945 <pre>
1946 logical page.
1947 </pre>
1948 \n (new line) Moves the active position to the initial position of the next line.
1949 \r (carriage return) Moves the active position to the initial position of the current line.
1950 \t (horizontal tab) Moves the active position to the next horizontal tabulation position
1951 <pre>
1952 on the current line. If the active position is at or past the last defined horizontal
1953 tabulation position, the behavior of the display device is unspecified.
1954 </pre>
1955 \v (vertical tab) Moves the active position to the initial position of the next vertical
1956 <!--page 43 -->
1957 <pre>
1958 tabulation position. If the active position is at or past the last defined vertical
1959 tabulation position, the behavior of the display device is unspecified.
1960 </pre>
1961 <p><!--para 3 -->
1962 Each of these escape sequences shall produce a unique implementation-defined value
1963 which can be stored in a single char object. The external representations in a text file
1964 need not be identical to the internal representations, and are outside the scope of this
1965 International Standard.
1966 <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>).
1969 <p><!--para 1 -->
1970 Functions shall be implemented such that they may be interrupted at any time by a signal,
1971 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
1972 invocations' control flow (after the interruption), function return values, or objects with
1973 automatic storage duration. All such objects shall be maintained outside the function
1974 image (the instructions that compose the executable representation of a function) on a
1975 per-invocation basis.
1978 <p><!--para 1 -->
1979 Both the translation and execution environments constrain the implementation of
1980 language translators and libraries. The following summarizes the language-related
1981 environmental limits on a conforming implementation; the library-related limits are
1982 discussed in clause 7.
1985 <p><!--para 1 -->
1986 The implementation shall be able to translate and execute at least one program that
1987 contains at least one instance of every one of the following limits:<sup><a href="#note18"><b>18)</b></a></sup>
1988 <ul>
1989 <li> 127 nesting levels of blocks
1990 <li> 63 nesting levels of conditional inclusion
1991 <li> 12 pointer, array, and function declarators (in any combinations) modifying an
1992 arithmetic, structure, union, or void type in a declaration
1993 <li> 63 nesting levels of parenthesized declarators within a full declarator
1994 <li> 63 nesting levels of parenthesized expressions within a full expression
1995 <li> 63 significant initial characters in an internal identifier or a macro name (each
1996 universal character name or extended source character is considered a single
1997 character)
1998 <li> 31 significant initial characters in an external identifier (each universal character name
1999 specifying a short identifier of 0000FFFF or less is considered 6 characters, each
2002 <!--page 44 -->
2003 <pre>
2004 universal character name specifying a short identifier of 00010000 or more is
2005 considered 10 characters, and each extended source character is considered the same
2006 number of characters as the corresponding universal character name, if any)<sup><a href="#note19"><b>19)</b></a></sup>
2007 </pre>
2008 <li> 4095 external identifiers in one translation unit
2009 <li> 511 identifiers with block scope declared in one block
2010 <li> 4095 macro identifiers simultaneously defined in one preprocessing translation unit
2011 <li> 127 parameters in one function definition
2012 <li> 127 arguments in one function call
2013 <li> 127 parameters in one macro definition
2014 <li> 127 arguments in one macro invocation
2015 <li> 4095 characters in a logical source line
2016 <li> 4095 characters in a string literal (after concatenation)
2017 <li> 65535 bytes in an object (in a hosted environment only)
2018 <li> 15 nesting levels for #included files
2019 <li> 1023 case labels for a switch statement (excluding those for any nested switch
2020 statements)
2021 <li> 1023 members in a single structure or union
2022 <li> 1023 enumeration constants in a single enumeration
2023 <li> 63 levels of nested structure or union definitions in a single struct-declaration-list
2024 </ul>
2026 <p><b>Footnotes</b>
2027 <p><small><a name="note18" href="#note18">18)</a> Implementations should avoid imposing fixed translation limits whenever possible.
2028 </small>
2029 <p><small><a name="note19" href="#note19">19)</a> See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
2030 </small>
2033 <p><!--para 1 -->
2034 An implementation is required to document all the limits specified in this subclause,
2035 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
2037 <p><b> Forward references</b>: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>).
2039 <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>
2040 <p><!--para 1 -->
2041 The values given below shall be replaced by constant expressions suitable for use in #if
2042 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
2043 following shall be replaced by expressions that have the same type as would an
2044 expression that is an object of the corresponding type converted according to the integer
2045 promotions. Their implementation-defined values shall be equal or greater in magnitude
2048 <!--page 45 -->
2049 (absolute value) to those shown, with the same sign.
2050 <ul>
2051 <li> number of bits for smallest object that is not a bit-field (byte)
2052 CHAR_BIT 8
2053 <li> minimum value for an object of type signed char
2054 SCHAR_MIN -127 // -(27 - 1)
2055 <li> maximum value for an object of type signed char
2056 SCHAR_MAX +127 // 27 - 1
2057 <li> maximum value for an object of type unsigned char
2058 UCHAR_MAX 255 // 28 - 1
2059 <li> minimum value for an object of type char
2060 CHAR_MIN see below
2061 <li> maximum value for an object of type char
2062 CHAR_MAX see below
2063 <li> maximum number of bytes in a multibyte character, for any supported locale
2064 MB_LEN_MAX 1
2065 <li> minimum value for an object of type short int
2066 SHRT_MIN -32767 // -(215 - 1)
2067 <li> maximum value for an object of type short int
2068 SHRT_MAX +32767 // 215 - 1
2069 <li> maximum value for an object of type unsigned short int
2070 USHRT_MAX 65535 // 216 - 1
2071 <li> minimum value for an object of type int
2072 INT_MIN -32767 // -(215 - 1)
2073 <li> maximum value for an object of type int
2074 INT_MAX +32767 // 215 - 1
2075 <li> maximum value for an object of type unsigned int
2076 UINT_MAX 65535 // 216 - 1
2077 <li> minimum value for an object of type long int
2078 LONG_MIN -2147483647 // -(231 - 1)
2079 <li> maximum value for an object of type long int
2080 LONG_MAX +2147483647 // 231 - 1
2081 <li> maximum value for an object of type unsigned long int
2082 ULONG_MAX 4294967295 // 232 - 1
2083 <!--page 46 -->
2084 <li> minimum value for an object of type long long int
2085 LLONG_MIN -9223372036854775807 // -(263 - 1)
2086 <li> maximum value for an object of type long long int
2087 LLONG_MAX +9223372036854775807 // 263 - 1
2088 <li> maximum value for an object of type unsigned long long int
2089 ULLONG_MAX 18446744073709551615 // 264 - 1
2090 </ul>
2091 <p><!--para 2 -->
2092 If the value of an object of type char is treated as a signed integer when used in an
2093 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
2094 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
2095 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
2096 UCHAR_MAX.<sup><a href="#note20"><b>20)</b></a></sup> The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
2097 <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>).
2099 <p><b>Footnotes</b>
2101 </small>
2103 <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>
2104 <p><!--para 1 -->
2105 The characteristics of floating types are defined in terms of a model that describes a
2106 representation of floating-point numbers and values that provide information about an
2107 implementation's floating-point arithmetic.<sup><a href="#note21"><b>21)</b></a></sup> The following parameters are used to
2108 define the model for each floating-point type:
2109 <pre>
2110 s sign ((+-)1)
2111 b base or radix of exponent representation (an integer > 1)
2112 e exponent (an integer between a minimum emin and a maximum emax )
2113 p precision (the number of base-b digits in the significand)
2114 fk nonnegative integers less than b (the significand digits)
2115 </pre>
2116 <p><!--para 2 -->
2117 A floating-point number (x) is defined by the following model:
2118 <pre>
2119 p
2120 x = sb e (Sum) f k b-k ,
2121 k=1
2122 emin <= e <= emax
2123 </pre>
2125 <p><!--para 3 -->
2126 In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be
2127 able to contain other kinds of floating-point numbers, such as subnormal floating-point
2128 numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0,
2129 e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and
2130 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
2131 through almost every arithmetic operation without raising a floating-point exception; a
2132 signaling NaN generally raises a floating-point exception when occurring as an
2135 <!--page 47 -->
2137 <p><!--para 4 -->
2138 An implementation may give zero and values that are not floating-point numbers (such as
2139 infinities and NaNs) a sign or may leave them unsigned. Wherever such values are
2140 unsigned, any requirement in this International Standard to retrieve the sign shall produce
2141 an unspecified sign, and any requirement to set the sign shall be ignored.
2142 <p><!--para 5 -->
2143 The minimum range of representable values for a floating type is the most negative finite
2144 floating-point number representable in that type through the most positive finite floating-
2145 point number representable in that type. In addition, if negative infinity is representable
2146 in a type, the range of that type is extended to all negative real numbers; likewise, if
2147 positive infinity is representable in a type, the range of that type is extended to all positive
2148 real numbers.
2149 <p><!--para 6 -->
2150 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
2151 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
2152 defined, as is the accuracy of the conversion between floating-point internal
2153 representations and string representations performed by the library functions in
2154 <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
2155 accuracy is unknown.
2156 <p><!--para 7 -->
2157 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
2158 expressions suitable for use in #if preprocessing directives; all floating values shall be
2159 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
2160 and FLT_ROUNDS have separate names for all three floating-point types. The floating-
2161 point model representation is provided for all values except FLT_EVAL_METHOD and
2162 FLT_ROUNDS.
2163 <p><!--para 8 -->
2164 The rounding mode for floating-point addition is characterized by the implementation-
2166 <pre>
2167 -1 indeterminable
2168 0 toward zero
2169 1 to nearest
2170 2 toward positive infinity
2171 3 toward negative infinity
2172 </pre>
2173 All other values for FLT_ROUNDS characterize implementation-defined rounding
2174 behavior.
2177 <!--page 48 -->
2178 <p><!--para 9 -->
2179 Except for assignment and cast (which remove all extra range and precision), the values
2180 yielded by operators with floating operands and values subject to the usual arithmetic
2181 conversions and of floating constants are evaluated to a format whose range and precision
2182 may be greater than required by the type. The use of evaluation formats is characterized
2183 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note24"><b>24)</b></a></sup>
2184 <pre>
2185 -1 indeterminable;
2186 0 evaluate all operations and constants just to the range and precision of the
2187 type;
2188 1 evaluate operations and constants of type float and double to the
2189 range and precision of the double type, evaluate long double
2190 operations and constants to the range and precision of the long double
2191 type;
2192 2 evaluate all operations and constants to the range and precision of the
2193 long double type.
2194 </pre>
2195 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
2196 behavior.
2197 <p><!--para 10 -->
2198 The presence or absence of subnormal numbers is characterized by the implementation-
2199 defined values of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and
2200 LDBL_HAS_SUBNORM:
2201 <pre>
2204 1 present (type does support subnormal numbers)
2205 </pre>
2206 <p><!--para 11 -->
2207 The values given in the following list shall be replaced by constant expressions with
2208 implementation-defined values that are greater or equal in magnitude (absolute value) to
2209 those shown, with the same sign:
2210 <ul>
2211 <li> radix of exponent representation, b
2212 FLT_RADIX 2
2217 <!--page 49 -->
2218 <li> number of base-FLT_RADIX digits in the floating-point significand, p
2219 FLT_MANT_DIG
2220 DBL_MANT_DIG
2221 LDBL_MANT_DIG
2222 <li> number of decimal digits, n, such that any floating-point number with p radix b digits
2223 can be rounded to a floating-point number with n decimal digits and back again
2224 without change to the value,
2225 <pre>
2226 { p log10 b if b is a power of 10
2227 {
2228 { [^1 + p log10 b^] otherwise
2229 </pre>
2230 FLT_DECIMAL_DIG 6
2231 DBL_DECIMAL_DIG 10
2232 LDBL_DECIMAL_DIG 10
2233 <li> number of decimal digits, n, such that any floating-point number in the widest
2234 supported floating type with pmax radix b digits can be rounded to a floating-point
2235 number with n decimal digits and back again without change to the value,
2236 <pre>
2237 { pmax log10 b if b is a power of 10
2238 {
2239 { [^1 + pmax log10 b^] otherwise
2240 </pre>
2241 DECIMAL_DIG 10
2242 <li> number of decimal digits, q, such that any floating-point number with q decimal digits
2243 can be rounded into a floating-point number with p radix b digits and back again
2244 without change to the q decimal digits,
2245 <pre>
2246 { p log10 b if b is a power of 10
2247 {
2248 { [_( p - 1) log10 b_] otherwise
2249 </pre>
2250 FLT_DIG 6
2251 DBL_DIG 10
2252 LDBL_DIG 10
2253 <li> minimum negative integer such that FLT_RADIX raised to one less than that power is
2254 a normalized floating-point number, emin
2255 FLT_MIN_EXP
2256 DBL_MIN_EXP
2257 LDBL_MIN_EXP
2258 <!--page 50 -->
2259 <li> minimum negative integer such that 10 raised to that power is in the range of
2260 normalized floating-point numbers, [^log10 b emin -1 ^]
2261 <pre>
2262 [ ]
2263 </pre>
2264 FLT_MIN_10_EXP -37
2265 DBL_MIN_10_EXP -37
2266 LDBL_MIN_10_EXP -37
2267 <li> maximum integer such that FLT_RADIX raised to one less than that power is a
2268 representable finite floating-point number, emax
2269 <pre>
2270 FLT_MAX_EXP
2271 DBL_MAX_EXP
2272 LDBL_MAX_EXP
2273 </pre>
2274 <li> maximum integer such that 10 raised to that power is in the range of representable
2275 finite floating-point numbers, [_log10 ((1 - b- p )b emax )_]
2276 <pre>
2277 FLT_MAX_10_EXP +37
2278 DBL_MAX_10_EXP +37
2279 LDBL_MAX_10_EXP +37
2280 </pre>
2281 </ul>
2282 <p><!--para 12 -->
2283 The values given in the following list shall be replaced by constant expressions with
2284 implementation-defined values that are greater than or equal to those shown:
2285 <ul>
2286 <li> maximum representable finite floating-point number, (1 - b- p )b emax
2287 <pre>
2288 FLT_MAX 1E+37
2289 DBL_MAX 1E+37
2290 LDBL_MAX 1E+37
2291 </pre>
2292 </ul>
2293 <p><!--para 13 -->
2294 The values given in the following list shall be replaced by constant expressions with
2295 implementation-defined (positive) values that are less than or equal to those shown:
2296 <ul>
2297 <li> the difference between 1 and the least value greater than 1 that is representable in the
2298 given floating point type, b1- p
2299 <pre>
2300 FLT_EPSILON 1E-5
2301 DBL_EPSILON 1E-9
2302 LDBL_EPSILON 1E-9
2303 </pre>
2304 <li> minimum normalized positive floating-point number, b emin -1
2305 <!--page 51 -->
2306 <pre>
2307 FLT_MIN 1E-37
2308 DBL_MIN 1E-37
2309 LDBL_MIN 1E-37
2310 </pre>
2312 FLT_TRUE_MIN 1E-37
2313 DBL_TRUE_MIN 1E-37
2314 LDBL_TRUE_MIN 1E-37
2315 </ul>
2316 <p><b>Recommended practice</b>
2317 <p><!--para 14 -->
2318 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
2319 should be the identity function.
2320 <p><!--para 15 -->
2321 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
2322 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
2323 float:
2324 <pre>
2325 6
2326 x = s16e (Sum) f k 16-k ,
2327 k=1
2328 -31 <= e <= +32
2329 </pre>
2331 <pre>
2332 FLT_RADIX 16
2333 FLT_MANT_DIG 6
2334 FLT_EPSILON 9.53674316E-07F
2335 FLT_DECIMAL_DIG 9
2336 FLT_DIG 6
2337 FLT_MIN_EXP -31
2338 FLT_MIN 2.93873588E-39F
2339 FLT_MIN_10_EXP -38
2340 FLT_MAX_EXP +32
2341 FLT_MAX 3.40282347E+38F
2342 FLT_MAX_10_EXP +38
2343 </pre>
2345 <p><!--para 16 -->
2346 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
2347 single-precision and double-precision numbers in IEC 60559,<sup><a href="#note28"><b>28)</b></a></sup> and the appropriate values in a
2349 <pre>
2350 24
2351 x f = s2e (Sum) f k 2-k ,
2352 k=1
2353 -125 <= e <= +128
2354 </pre>
2356 <pre>
2357 53
2358 x d = s2e (Sum) f k 2-k ,
2359 k=1
2360 -1021 <= e <= +1024
2361 </pre>
2363 <pre>
2364 FLT_RADIX 2
2365 DECIMAL_DIG 17
2366 FLT_MANT_DIG 24
2367 FLT_EPSILON 1.19209290E-07F // decimal constant
2368 FLT_EPSILON 0X1P-23F // hex constant
2369 FLT_DECIMAL_DIG 9
2370 </pre>
2373 <!--page 52 -->
2374 <pre>
2375 FLT_DIG 6
2376 FLT_MIN_EXP -125
2377 FLT_MIN 1.17549435E-38F // decimal constant
2378 FLT_MIN 0X1P-126F // hex constant
2379 FLT_TRUE_MIN 1.40129846E-45F // decimal constant
2380 FLT_TRUE_MIN 0X1P-149F // hex constant
2381 FLT_HAS_SUBNORM 1
2382 FLT_MIN_10_EXP -37
2383 FLT_MAX_EXP +128
2384 FLT_MAX 3.40282347E+38F // decimal constant
2385 FLT_MAX 0X1.fffffeP127F // hex constant
2386 FLT_MAX_10_EXP +38
2387 DBL_MANT_DIG 53
2388 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
2389 DBL_EPSILON 0X1P-52 // hex constant
2390 DBL_DECIMAL_DIG 17
2391 DBL_DIG 15
2392 DBL_MIN_EXP -1021
2393 DBL_MIN 2.2250738585072014E-308 // decimal constant
2394 DBL_MIN 0X1P-1022 // hex constant
2395 DBL_TRUE_MIN 4.9406564584124654E-324 // decimal constant
2396 DBL_TRUE_MIN 0X1P-1074 // hex constant
2397 DBL_HAS_SUBNORM 1
2398 DBL_MIN_10_EXP -307
2399 DBL_MAX_EXP +1024
2400 DBL_MAX 1.7976931348623157E+308 // decimal constant
2401 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
2402 DBL_MAX_10_EXP +308
2403 </pre>
2404 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
2405 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
2406 precision), then DECIMAL_DIG would be 21.
2408 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
2409 <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>
2410 (<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>
2411 (<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>).
2412 <!--page 53 -->
2414 <p><b>Footnotes</b>
2415 <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
2416 does not require the floating-point arithmetic of the implementation to be identical.
2417 </small>
2418 <p><small><a name="note22" href="#note22">22)</a> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
2419 IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
2420 similar behavior.
2421 </small>
2422 <p><small><a name="note23" href="#note23">23)</a> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
2424 </small>
2425 <p><small><a name="note24" href="#note24">24)</a> The evaluation method determines evaluation formats of expressions involving all floating types, not
2426 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
2427 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
2428 double.
2429 </small>
2430 <p><small><a name="note25" href="#note25">25)</a> Characterization as indeterminable is intended if floating-point operations do not consistently interpret
2431 subnormal representations as zero, nor as nonzero.
2432 </small>
2433 <p><small><a name="note26" href="#note26">26)</a> Characterization as absent is intended if no floating-point operations produce subnormal results from
2434 non-subnormal inputs, even if the type format includes representations of subnormal numbers.
2435 </small>
2436 <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
2437 positive number no greater than the minimum normalized positive number for the type.
2438 </small>
2439 <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
2440 limits are one less than shown here.
2441 </small>
2446 <p><!--para 1 -->
2447 In the syntax notation used in this clause, syntactic categories (nonterminals) are
2448 indicated by italic type, and literal words and character set members (terminals) by bold
2449 type. A colon (:) following a nonterminal introduces its definition. Alternative
2450 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
2451 optional symbol is indicated by the subscript ''opt'', so that
2452 <pre>
2453 { expression<sub>opt</sub> }
2454 </pre>
2455 indicates an optional expression enclosed in braces.
2456 <p><!--para 2 -->
2457 When syntactic categories are referred to in the main text, they are not italicized and
2458 words are separated by spaces instead of hyphens.
2459 <p><!--para 3 -->
2465 <p><!--para 1 -->
2466 An identifier can denote an object; a function; a tag or a member of a structure, union, or
2467 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
2468 same identifier can denote different entities at different points in the program. A member
2469 of an enumeration is called an enumeration constant. Macro names and macro
2470 parameters are not considered further here, because prior to the semantic phase of
2471 program translation any occurrences of macro names in the source file are replaced by the
2472 preprocessing token sequences that constitute their macro definitions.
2473 <p><!--para 2 -->
2474 For each different entity that an identifier designates, the identifier is visible (i.e., can be
2475 used) only within a region of program text called its scope. Different entities designated
2476 by the same identifier either have different scopes, or are in different name spaces. There
2477 are four kinds of scopes: function, file, block, and function prototype. (A function
2478 prototype is a declaration of a function that declares the types of its parameters.)
2479 <p><!--para 3 -->
2480 A label name is the only kind of identifier that has function scope. It can be used (in a
2481 goto statement) anywhere in the function in which it appears, and is declared implicitly
2482 by its syntactic appearance (followed by a : and a statement).
2483 <p><!--para 4 -->
2484 Every other identifier has scope determined by the placement of its declaration (in a
2485 declarator or type specifier). If the declarator or type specifier that declares the identifier
2486 appears outside of any block or list of parameters, the identifier has file scope, which
2487 terminates at the end of the translation unit. If the declarator or type specifier that
2488 declares the identifier appears inside a block or within the list of parameter declarations in
2489 a function definition, the identifier has block scope, which terminates at the end of the
2490 associated block. If the declarator or type specifier that declares the identifier appears
2491 <!--page 54 -->
2492 within the list of parameter declarations in a function prototype (not part of a function
2493 definition), the identifier has function prototype scope, which terminates at the end of the
2494 function declarator. If an identifier designates two different entities in the same name
2495 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will end
2496 strictly before the scope of the other entity (the outer scope). Within the inner scope, the
2497 identifier designates the entity declared in the inner scope; the entity declared in the outer
2498 scope is hidden (and not visible) within the inner scope.
2499 <p><!--para 5 -->
2500 Unless explicitly stated otherwise, where this International Standard uses the term
2501 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
2502 entity in the relevant name space whose declaration is visible at the point the identifier
2503 occurs.
2504 <p><!--para 6 -->
2505 Two identifiers have the same scope if and only if their scopes terminate at the same
2506 point.
2507 <p><!--para 7 -->
2508 Structure, union, and enumeration tags have scope that begins just after the appearance of
2509 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
2510 begins just after the appearance of its defining enumerator in an enumerator list. Any
2511 other identifier has scope that begins just after the completion of its declarator.
2512 <p><!--para 8 -->
2513 As a special case, a type name (which is not a declaration of an identifier) is considered to
2514 have a scope that begins just after the place within the type name where the omitted
2515 identifier would appear were it not omitted.
2516 <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
2517 (<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>),
2521 <p><!--para 1 -->
2522 An identifier declared in different scopes or in the same scope more than once can be
2523 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
2524 three kinds of linkage: external, internal, and none.
2525 <p><!--para 2 -->
2526 In the set of translation units and libraries that constitutes an entire program, each
2527 declaration of a particular identifier with external linkage denotes the same object or
2528 function. Within one translation unit, each declaration of an identifier with internal
2529 linkage denotes the same object or function. Each declaration of an identifier with no
2530 linkage denotes a unique entity.
2531 <p><!--para 3 -->
2532 If the declaration of a file scope identifier for an object or a function contains the storage-
2533 class specifier static, the identifier has internal linkage.<sup><a href="#note30"><b>30)</b></a></sup>
2537 <!--page 55 -->
2538 <p><!--para 4 -->
2539 For an identifier declared with the storage-class specifier extern in a scope in which a
2540 prior declaration of that identifier is visible,<sup><a href="#note31"><b>31)</b></a></sup> if the prior declaration specifies internal or
2541 external linkage, the linkage of the identifier at the later declaration is the same as the
2542 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
2543 declaration specifies no linkage, then the identifier has external linkage.
2544 <p><!--para 5 -->
2545 If the declaration of an identifier for a function has no storage-class specifier, its linkage
2546 is determined exactly as if it were declared with the storage-class specifier extern. If
2547 the declaration of an identifier for an object has file scope and no storage-class specifier,
2548 its linkage is external.
2549 <p><!--para 6 -->
2550 The following identifiers have no linkage: an identifier declared to be anything other than
2551 an object or a function; an identifier declared to be a function parameter; a block scope
2552 identifier for an object declared without the storage-class specifier extern.
2553 <p><!--para 7 -->
2554 If, within a translation unit, the same identifier appears with both internal and external
2555 linkage, the behavior is undefined.
2556 <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>),
2559 <p><b>Footnotes</b>
2560 <p><small><a name="note29" href="#note29">29)</a> There is no linkage between different identifiers.
2561 </small>
2562 <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
2564 </small>
2565 <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.
2566 </small>
2569 <p><!--para 1 -->
2570 If more than one declaration of a particular identifier is visible at any point in a
2571 translation unit, the syntactic context disambiguates uses that refer to different entities.
2572 Thus, there are separate name spaces for various categories of identifiers, as follows:
2573 <ul>
2574 <li> label names (disambiguated by the syntax of the label declaration and use);
2575 <li> the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note32"><b>32)</b></a></sup>
2576 of the keywords struct, union, or enum);
2577 <li> the members of structures or unions; each structure or union has a separate name
2578 space for its members (disambiguated by the type of the expression used to access the
2579 member via the . or -> operator);
2580 <li> all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
2581 enumeration constants).
2582 </ul>
2583 <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>),
2584 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
2587 <!--page 56 -->
2589 <p><b>Footnotes</b>
2590 <p><small><a name="note32" href="#note32">32)</a> There is only one name space for tags even though three are possible.
2591 </small>
2594 <p><!--para 1 -->
2595 An object has a storage duration that determines its lifetime. There are four storage
2596 durations: static, thread, automatic, and allocated. Allocated storage is described in
2598 <p><!--para 2 -->
2599 The lifetime of an object is the portion of program execution during which storage is
2600 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note33"><b>33)</b></a></sup> and retains
2601 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
2602 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
2603 the object it points to (or just past) reaches the end of its lifetime.
2604 <p><!--para 3 -->
2605 An object whose identifier is declared without the storage-class specifier
2606 _Thread_local, and either with external or internal linkage or with the storage-class
2607 specifier static, has static storage duration. Its lifetime is the entire execution of the
2608 program and its stored value is initialized only once, prior to program startup.
2609 <p><!--para 4 -->
2610 An object whose identifier is declared with the storage-class specifier _Thread_local
2611 has thread storage duration. Its lifetime is the entire execution of the thread for which it
2612 is created, and its stored value is initialized when the thread is started. There is a distinct
2613 object per thread, and use of the declared name in an expression refers to the object
2614 associated with the thread evaluating the expression. The result of attempting to
2615 indirectly access an object with thread storage duration from a thread other than the one
2616 with which the object is associated is implementation-defined.
2617 <p><!--para 5 -->
2618 An object whose identifier is declared with no linkage and without the storage-class
2619 specifier static has automatic storage duration, as do some compound literals. The
2620 result of attempting to indirectly access an object with automatic storage duration from a
2621 thread other than the one with which the object is associated is implementation-defined.
2622 <p><!--para 6 -->
2623 For such an object that does not have a variable length array type, its lifetime extends
2624 from entry into the block with which it is associated until execution of that block ends in
2625 any way. (Entering an enclosed block or calling a function suspends, but does not end,
2626 execution of the current block.) If the block is entered recursively, a new instance of the
2627 object is created each time. The initial value of the object is indeterminate. If an
2628 initialization is specified for the object, it is performed each time the declaration or
2629 compound literal is reached in the execution of the block; otherwise, the value becomes
2630 indeterminate each time the declaration is reached.
2634 <!--page 57 -->
2635 <p><!--para 7 -->
2636 For such an object that does have a variable length array type, its lifetime extends from
2637 the declaration of the object until execution of the program leaves the scope of the
2638 declaration.<sup><a href="#note35"><b>35)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2639 each time. The initial value of the object is indeterminate.
2640 <p><!--para 8 -->
2641 A non-lvalue expression with structure or union type, where the structure or union
2642 contains a member with array type (including, recursively, members of all contained
2643 structures and unions) refers to an object with automatic storage duration and temporary
2644 lifetime.<sup><a href="#note36"><b>36)</b></a></sup> Its lifetime begins when the expression is evaluated and its initial value is the
2645 value of the expression. Its lifetime ends when the evaluation of the containing full
2646 expression or full declarator ends. Any attempt to modify an object with temporary
2647 lifetime results in undefined behavior.
2648 <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
2649 (<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>).
2651 <p><b>Footnotes</b>
2652 <p><small><a name="note33" href="#note33">33)</a> The term ''constant address'' means that two pointers to the object constructed at possibly different
2653 times will compare equal. The address may be different during two different executions of the same
2654 program.
2655 </small>
2656 <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.
2657 </small>
2658 <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
2659 embedded block prior to the declaration, leaves the scope of the declaration.
2660 </small>
2661 <p><small><a name="note36" href="#note36">36)</a> The address of such an object is taken implicitly when an array member is accessed.
2662 </small>
2665 <p><!--para 1 -->
2666 The meaning of a value stored in an object or returned by a function is determined by the
2667 type of the expression used to access it. (An identifier declared to be an object is the
2668 simplest such expression; the type is specified in the declaration of the identifier.) Types
2669 are partitioned into object types (types that describe objects) and function types (types
2670 that describe functions). At various points within a translation unit an object type may be
2671 incomplete (lacking sufficient information to determine the size of objects of that type) or
2673 <p><!--para 2 -->
2674 An object declared as type _Bool is large enough to store the values 0 and 1.
2675 <p><!--para 3 -->
2676 An object declared as type char is large enough to store any member of the basic
2677 execution character set. If a member of the basic execution character set is stored in a
2678 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2679 a char object, the resulting value is implementation-defined but shall be within the range
2680 of values that can be represented in that type.
2681 <p><!--para 4 -->
2682 There are five standard signed integer types, designated as signed char, short
2683 int, int, long int, and long long int. (These and other types may be
2684 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2685 implementation-defined extended signed integer types.<sup><a href="#note38"><b>38)</b></a></sup> The standard and extended
2686 signed integer types are collectively called signed integer types.<sup><a href="#note39"><b>39)</b></a></sup>
2688 <!--page 58 -->
2689 <p><!--para 5 -->
2690 An object declared as type signed char occupies the same amount of storage as a
2691 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2692 architecture of the execution environment (large enough to contain any value in the range
2694 <p><!--para 6 -->
2695 For each of the signed integer types, there is a corresponding (but different) unsigned
2696 integer type (designated with the keyword unsigned) that uses the same amount of
2697 storage (including sign information) and has the same alignment requirements. The type
2698 _Bool and the unsigned integer types that correspond to the standard signed integer
2699 types are the standard unsigned integer types. The unsigned integer types that
2700 correspond to the extended signed integer types are the extended unsigned integer types.
2701 The standard and extended unsigned integer types are collectively called unsigned integer
2703 <p><!--para 7 -->
2704 The standard signed integer types and standard unsigned integer types are collectively
2705 called the standard integer types, the extended signed integer types and extended
2706 unsigned integer types are collectively called the extended integer types.
2707 <p><!--para 8 -->
2708 For any two integer types with the same signedness and different integer conversion rank
2709 (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
2710 subrange of the values of the other type.
2711 <p><!--para 9 -->
2712 The range of nonnegative values of a signed integer type is a subrange of the
2713 corresponding unsigned integer type, and the representation of the same value in each
2714 type is the same.<sup><a href="#note41"><b>41)</b></a></sup> A computation involving unsigned operands can never overflow,
2715 because a result that cannot be represented by the resulting unsigned integer type is
2716 reduced modulo the number that is one greater than the largest value that can be
2717 represented by the resulting type.
2718 <p><!--para 10 -->
2719 There are three real floating types, designated as float, double, and long
2720 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
2721 type double; the set of values of the type double is a subset of the set of values of the
2722 type long double.
2725 <!--page 59 -->
2726 <p><!--para 11 -->
2727 There are three complex types, designated as float _Complex, double
2728 _Complex, and long double _Complex.<sup><a href="#note43"><b>43)</b></a></sup> (Complex types are a conditional
2729 feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.) The real floating and
2730 complex types are collectively called the floating types.
2731 <p><!--para 12 -->
2732 For each floating type there is a corresponding real type, which is always a real floating
2733 type. For real floating types, it is the same type. For complex types, it is the type given
2734 by deleting the keyword _Complex from the type name.
2735 <p><!--para 13 -->
2736 Each complex type has the same representation and alignment requirements as an array
2737 type containing exactly two elements of the corresponding real type; the first element is
2738 equal to the real part, and the second element to the imaginary part, of the complex
2739 number.
2740 <p><!--para 14 -->
2741 The type char, the signed and unsigned integer types, and the floating types are
2742 collectively called the basic types. The basic types are complete object types. Even if the
2743 implementation defines two or more basic types to have the same representation, they are
2745 <p><!--para 15 -->
2746 The three types char, signed char, and unsigned char are collectively called
2747 the character types. The implementation shall define char to have the same range,
2748 representation, and behavior as either signed char or unsigned char.<sup><a href="#note45"><b>45)</b></a></sup>
2749 <p><!--para 16 -->
2750 An enumeration comprises a set of named integer constant values. Each distinct
2751 enumeration constitutes a different enumerated type.
2752 <p><!--para 17 -->
2753 The type char, the signed and unsigned integer types, and the enumerated types are
2754 collectively called integer types. The integer and real floating types are collectively called
2755 real types.
2756 <p><!--para 18 -->
2757 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2758 belongs to one type domain: the real type domain comprises the real types, the complex
2759 type domain comprises the complex types.
2760 <p><!--para 19 -->
2761 The void type comprises an empty set of values; it is an incomplete object type that
2762 cannot be completed.
2766 <!--page 60 -->
2767 <p><!--para 20 -->
2768 Any number of derived types can be constructed from the object and function types, as
2769 follows:
2770 <ul>
2771 <li> An array type describes a contiguously allocated nonempty set of objects with a
2772 particular member object type, called the element type. The element type shall be
2773 complete whenever the array type is specified. Array types are characterized by their
2774 element type and by the number of elements in the array. An array type is said to be
2775 derived from its element type, and if its element type is T , the array type is sometimes
2776 called ''array of T ''. The construction of an array type from an element type is called
2777 ''array type derivation''.
2778 <li> A structure type describes a sequentially allocated nonempty set of member objects
2779 (and, in certain circumstances, an incomplete array), each of which has an optionally
2780 specified name and possibly distinct type.
2781 <li> A union type describes an overlapping nonempty set of member objects, each of
2782 which has an optionally specified name and possibly distinct type.
2783 <li> A function type describes a function with specified return type. A function type is
2784 characterized by its return type and the number and types of its parameters. A
2785 function type is said to be derived from its return type, and if its return type is T , the
2786 function type is sometimes called ''function returning T ''. The construction of a
2787 function type from a return type is called ''function type derivation''.
2788 <li> A pointer type may be derived from a function type or an object type, called the
2789 referenced type. A pointer type describes an object whose value provides a reference
2790 to an entity of the referenced type. A pointer type derived from the referenced type T
2791 is sometimes called ''pointer to T ''. The construction of a pointer type from a
2792 referenced type is called ''pointer type derivation''. A pointer type is a complete
2793 object type.
2794 <li> An atomic type describes the type designated by the construct _Atomic ( type-
2795 name ). (Atomic types are a conditional feature that implementations need not
2797 </ul>
2798 These methods of constructing derived types can be applied recursively.
2799 <p><!--para 21 -->
2800 Arithmetic types and pointer types are collectively called scalar types. Array and
2801 structure types are collectively called aggregate types.<sup><a href="#note46"><b>46)</b></a></sup>
2802 <p><!--para 22 -->
2803 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2804 that type, by specifying the size in a later declaration (with internal or external linkage).
2805 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
2808 <!--page 61 -->
2809 type. It is completed, for all declarations of that type, by declaring the same structure or
2810 union tag with its defining content later in the same scope.
2811 <p><!--para 23 -->
2812 A type has known constant size if the type is not incomplete and is not a variable length
2813 array type.
2814 <p><!--para 24 -->
2815 Array, function, and pointer types are collectively called derived declarator types. A
2816 declarator type derivation from a type T is the construction of a derived declarator type
2817 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2818 T.
2819 <p><!--para 25 -->
2820 A type is characterized by its type category, which is either the outermost derivation of a
2821 derived type (as noted above in the construction of derived types), or the type itself if the
2822 type consists of no derived types.
2823 <p><!--para 26 -->
2824 Any type so far mentioned is an unqualified type. Each unqualified type has several
2825 qualified versions of its type,<sup><a href="#note47"><b>47)</b></a></sup> corresponding to the combinations of one, two, or all
2826 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2827 versions of a type are distinct types that belong to the same type category and have the
2828 same representation and alignment requirements.<sup><a href="#note48"><b>48)</b></a></sup> A derived type is not qualified by the
2829 qualifiers (if any) of the type from which it is derived.
2830 <p><!--para 27 -->
2831 Further, there is the _Atomic qualifier. The presence of the _Atomic qualifier
2832 designates an atomic type. The size, representation, and alignment of an atomic type
2833 need not be the same as those of the corresponding unqualified type. Therefore, this
2834 Standard explicitly uses the phrase ''atomic, qualified or unqualified type'' whenever the
2835 atomic version of a type is permitted along with the other qualified versions of a type.
2836 The phrase ''qualified or unqualified type'', without specific mention of atomic, does not
2837 include the atomic types.
2838 <p><!--para 28 -->
2839 A pointer to void shall have the same representation and alignment requirements as a
2840 pointer to a character type.<sup><a href="#note48"><b>48)</b></a></sup> Similarly, pointers to qualified or unqualified versions of
2841 compatible types shall have the same representation and alignment requirements. All
2842 pointers to structure types shall have the same representation and alignment requirements
2843 as each other. All pointers to union types shall have the same representation and
2844 alignment requirements as each other. Pointers to other types need not have the same
2845 representation or alignment requirements.
2846 <p><!--para 29 -->
2847 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2848 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2849 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2852 <!--page 62 -->
2853 qualified float'' and is a pointer to a qualified type.
2855 <p><!--para 30 -->
2856 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
2857 function returning struct tag''. The array has length five and the function has a single parameter of type
2858 float. Its type category is array.
2860 <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>).
2862 <p><b>Footnotes</b>
2863 <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
2864 different points within a translation unit.
2865 </small>
2866 <p><small><a name="note38" href="#note38">38)</a> Implementation-defined keywords shall have the form of an identifier reserved for any use as
2868 </small>
2869 <p><small><a name="note39" href="#note39">39)</a> Therefore, any statement in this Standard about signed integer types also applies to the extended
2870 signed integer types.
2871 </small>
2872 <p><small><a name="note40" href="#note40">40)</a> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2873 unsigned integer types.
2874 </small>
2875 <p><small><a name="note41" href="#note41">41)</a> The same representation and alignment requirements are meant to imply interchangeability as
2876 arguments to functions, return values from functions, and members of unions.
2877 </small>
2878 <p><small><a name="note42" href="#note42">42)</a> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2879 </small>
2880 <p><small><a name="note43" href="#note43">43)</a> A specification for imaginary types is in <a href="#G">annex G</a>.
2881 </small>
2882 <p><small><a name="note44" href="#note44">44)</a> An implementation may define new keywords that provide alternative ways to designate a basic (or
2883 any other) type; this does not violate the requirement that all basic types be different.
2884 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2886 </small>
2887 <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
2888 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2889 other two and is not compatible with either.
2890 </small>
2891 <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
2892 contain one member at a time.
2893 </small>
2894 <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.
2895 </small>
2896 <p><small><a name="note48" href="#note48">48)</a> The same representation and alignment requirements are meant to imply interchangeability as
2897 arguments to functions, return values from functions, and members of unions.
2898 </small>
2903 <p><!--para 1 -->
2904 The representations of all types are unspecified except as stated in this subclause.
2905 <p><!--para 2 -->
2906 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2907 the number, order, and encoding of which are either explicitly specified or
2908 implementation-defined.
2909 <p><!--para 3 -->
2910 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2912 <p><!--para 4 -->
2913 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2914 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2915 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
2916 called the object representation of the value. Values stored in bit-fields consist of m bits,
2917 where m is the size specified for the bit-field. The object representation is the set of m
2918 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
2919 than NaNs) with the same object representation compare equal, but values that compare
2920 equal may have different object representations.
2921 <p><!--para 5 -->
2922 Certain object representations need not represent a value of the object type. If the stored
2923 value of an object has such a representation and is read by an lvalue expression that does
2924 not have character type, the behavior is undefined. If such a representation is produced
2925 by a side effect that modifies all or any part of the object by an lvalue expression that
2926 does not have character type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup> Such a representation is called
2927 a trap representation.
2928 <p><!--para 6 -->
2929 When a value is stored in an object of structure or union type, including in a member
2930 object, the bytes of the object representation that correspond to any padding bytes take
2931 unspecified values.<sup><a href="#note51"><b>51)</b></a></sup> The value of a structure or union object is never a trap
2934 <!--page 63 -->
2935 representation, even though the value of a member of the structure or union object may be
2936 a trap representation.
2937 <p><!--para 7 -->
2938 When a value is stored in a member of an object of union type, the bytes of the object
2939 representation that do not correspond to that member but do correspond to other members
2940 take unspecified values.
2941 <p><!--para 8 -->
2942 Where an operator is applied to a value that has more than one object representation,
2943 which object representation is used shall not affect the value of the result.<sup><a href="#note52"><b>52)</b></a></sup> Where a
2944 value is stored in an object using a type that has more than one object representation for
2945 that value, it is unspecified which representation is used, but a trap representation shall
2946 not be generated.
2947 <p><!--para 9 -->
2948 Loads and stores of objects with atomic types are done with
2949 memory_order_seq_cst semantics.
2950 <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
2951 designators (<a href="#6.3.2.1">6.3.2.1</a>), order and consistency (<a href="#7.17.3">7.17.3</a>).
2953 <p><b>Footnotes</b>
2954 <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
2955 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
2956 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
2957 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
2958 type unsigned char range from 0 to 2
2960 <pre>
2961 CHAR_BIT
2962 - 1.
2963 </pre>
2964 </small>
2965 <p><small><a name="note50" href="#note50">50)</a> Thus, an automatic variable can be initialized to a trap representation without causing undefined
2966 behavior, but the value of the variable cannot be used until a proper value is stored in it.
2967 </small>
2968 <p><small><a name="note51" href="#note51">51)</a> Thus, for example, structure assignment need not copy any padding bits.
2969 </small>
2970 <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
2971 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
2972 defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
2973 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
2974 on values of type T may distinguish between them.
2975 </small>
2978 <p><!--para 1 -->
2979 For unsigned integer types other than unsigned char, the bits of the object
2980 representation shall be divided into two groups: value bits and padding bits (there need
2981 not be any of the latter). If there are N value bits, each bit shall represent a different
2982 power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of
2983 representing values from 0 to 2 N - 1 using a pure binary representation; this shall be
2984 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note53"><b>53)</b></a></sup>
2985 <p><!--para 2 -->
2986 For signed integer types, the bits of the object representation shall be divided into three
2987 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
2988 signed char shall not have any padding bits. There shall be exactly one sign bit.
2989 Each bit that is a value bit shall have the same value as the same bit in the object
2990 representation of the corresponding unsigned type (if there are M value bits in the signed
2991 type and N in the unsigned type, then M <= N ). If the sign bit is zero, it shall not affect
2993 <!--page 64 -->
2994 the resulting value. If the sign bit is one, the value shall be modified in one of the
2995 following ways:
2996 <ul>
2997 <li> the corresponding value with sign bit 0 is negated (sign and magnitude);
2998 <li> the sign bit has the value -(2 M ) (two's complement);
2999 <li> the sign bit has the value -(2 M - 1) (ones' complement).
3000 </ul>
3001 Which of these applies is implementation-defined, as is whether the value with sign bit 1
3002 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
3003 complement), is a trap representation or a normal value. In the case of sign and
3004 magnitude and ones' complement, if this representation is a normal value it is called a
3005 negative zero.
3006 <p><!--para 3 -->
3007 If the implementation supports negative zeros, they shall be generated only by:
3008 <ul>
3009 <li> the &, |, ^, ~, <<, and >> operators with operands that produce such a value;
3010 <li> the +, -, *, /, and % operators where one operand is a negative zero and the result is
3011 zero;
3012 <li> compound assignment operators based on the above cases.
3013 </ul>
3014 It is unspecified whether these cases actually generate a negative zero or a normal zero,
3015 and whether a negative zero becomes a normal zero when stored in an object.
3016 <p><!--para 4 -->
3017 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
3018 and >> operators with operands that would produce such a value is undefined.
3019 <p><!--para 5 -->
3020 The values of any padding bits are unspecified.<sup><a href="#note54"><b>54)</b></a></sup> A valid (non-trap) object representation
3021 of a signed integer type where the sign bit is zero is a valid object representation of the
3022 corresponding unsigned type, and shall represent the same value. For any integer type,
3023 the object representation where all the bits are zero shall be a representation of the value
3024 zero in that type.
3025 <p><!--para 6 -->
3026 The precision of an integer type is the number of bits it uses to represent values,
3027 excluding any sign and padding bits. The width of an integer type is the same but
3028 including any sign bit; thus for unsigned integer types the two values are the same, while
3029 for signed integer types the width is one greater than the precision.
3034 <!--page 65 -->
3036 <p><b>Footnotes</b>
3037 <p><small><a name="note53" href="#note53">53)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
3038 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
3039 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
3040 with unsigned types. All other combinations of padding bits are alternative object representations of
3041 the value specified by the value bits.
3042 </small>
3043 <p><small><a name="note54" href="#note54">54)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
3044 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
3045 representation other than as part of an exceptional condition such as an overflow. All other
3046 combinations of padding bits are alternative object representations of the value specified by the value
3047 bits.
3048 </small>
3051 <p><!--para 1 -->
3052 Two types have compatible type if their types are the same. Additional rules for
3053 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
3054 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,
3055 union, or enumerated types declared in separate translation units are compatible if their
3056 tags and members satisfy the following requirements: If one is declared with a tag, the
3057 other shall be declared with the same tag. If both are completed anywhere within their
3058 respective translation units, then the following additional requirements apply: there shall
3059 be a one-to-one correspondence between their members such that each pair of
3060 corresponding members are declared with compatible types; if one member of the pair is
3061 declared with an alignment specifier, the other is declared with an equivalent alignment
3062 specifier; and if one member of the pair is declared with a name, the other is declared
3063 with the same name. For two structures, corresponding members shall be declared in the
3064 same order. For two structures or unions, corresponding bit-fields shall have the same
3065 widths. For two enumerations, corresponding members shall have the same values.
3066 <p><!--para 2 -->
3067 All declarations that refer to the same object or function shall have compatible type;
3068 otherwise, the behavior is undefined.
3069 <p><!--para 3 -->
3070 A composite type can be constructed from two types that are compatible; it is a type that
3071 is compatible with both of the two types and satisfies the following conditions:
3072 <ul>
3073 <li> If both types are array types, the following rules are applied:
3074 <ul>
3075 <li> If one type is an array of known constant size, the composite type is an array of
3076 that size.
3077 <li> Otherwise, if one type is a variable length array whose size is specified by an
3078 expression that is not evaluated, the behavior is undefined.
3079 <li> Otherwise, if one type is a variable length array whose size is specified, the
3080 composite type is a variable length array of that size.
3081 <li> Otherwise, if one type is a variable length array of unspecified size, the composite
3082 type is a variable length array of unspecified size.
3083 <li> Otherwise, both types are arrays of unknown size and the composite type is an
3084 array of unknown size.
3085 </ul>
3086 The element type of the composite type is the composite type of the two element
3087 types.
3088 <li> If only one type is a function type with a parameter type list (a function prototype),
3089 the composite type is a function prototype with the parameter type list.
3092 <!--page 66 -->
3093 <li> If both types are function types with parameter type lists, the type of each parameter
3094 in the composite parameter type list is the composite type of the corresponding
3095 parameters.
3096 </ul>
3097 These rules apply recursively to the types from which the two types are derived.
3098 <p><!--para 4 -->
3099 For an identifier with internal or external linkage declared in a scope in which a prior
3100 declaration of that identifier is visible,<sup><a href="#note56"><b>56)</b></a></sup> if the prior declaration specifies internal or
3101 external linkage, the type of the identifier at the later declaration becomes the composite
3102 type.
3104 <p><!--para 5 -->
3105 EXAMPLE Given the following two file scope declarations:
3106 <pre>
3107 int f(int (*)(), double (*)[3]);
3108 int f(int (*)(char *), double (*)[]);
3109 </pre>
3110 The resulting composite type for the function is:
3111 <pre>
3112 int f(int (*)(char *), double (*)[3]);
3113 </pre>
3116 <p><b>Footnotes</b>
3117 <p><small><a name="note55" href="#note55">55)</a> Two types need not be identical to be compatible.
3118 </small>
3119 <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.
3120 </small>
3123 <p><!--para 1 -->
3124 Complete object types have alignment requirements which place restrictions on the
3125 addresses at which objects of that type may be allocated. An alignment is an
3126 implementation-defined integer value representing the number of bytes between
3127 successive addresses at which a given object can be allocated. An object type imposes an
3128 alignment requirement on every object of that type: stricter alignment can be requested
3129 using the _Alignas keyword.
3130 <p><!--para 2 -->
3131 A fundamental alignment is represented by an alignment less than or equal to the greatest
3132 alignment supported by the implementation in all contexts, which is equal to
3133 alignof(max_align_t).
3134 <p><!--para 3 -->
3135 An extended alignment is represented by an alignment greater than
3136 alignof(max_align_t). It is implementation-defined whether any extended
3137 alignments are supported and the contexts in which they are supported. A type having an
3138 extended alignment requirement is an over-aligned type.<sup><a href="#note57"><b>57)</b></a></sup>
3139 <p><!--para 4 -->
3140 Alignments are represented as values of the type size_t. Valid alignments include only
3141 those values returned by an alignof expression for fundamental types, plus an
3142 additional implementation-defined set of values, which may be empty. Every valid
3143 alignment value shall be a nonnegative integral power of two.
3146 <!--page 67 -->
3147 <p><!--para 5 -->
3148 Alignments have an order from weaker to stronger or stricter alignments. Stricter
3149 alignments have larger alignment values. An address that satisfies an alignment
3150 requirement also satisfies any weaker valid alignment requirement.
3151 <p><!--para 6 -->
3152 The alignment requirement of a complete type can be queried using an alignof
3153 expression. The types char, signed char, and unsigned char shall have the
3154 weakest alignment requirement.
3155 <p><!--para 7 -->
3156 Comparing alignments is meaningful and provides the obvious results:
3157 <ul>
3158 <li> Two alignments are equal when their numeric values are equal.
3159 <li> Two alignments are different when their numeric values are not equal.
3160 <li> When an alignment is larger than another it represents a stricter alignment.
3161 <!--page 68 -->
3162 </ul>
3164 <p><b>Footnotes</b>
3165 <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
3166 alignment has been applied.
3167 </small>
3170 <p><!--para 1 -->
3171 Several operators convert operand values from one type to another automatically. This
3172 subclause specifies the result required from such an implicit conversion, as well as those
3173 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
3174 the conversions performed by most ordinary operators; it is supplemented as required by
3176 <p><!--para 2 -->
3177 Conversion of an operand value to a compatible type causes no change to the value or the
3178 representation.
3184 <p><!--para 1 -->
3185 Every integer type has an integer conversion rank defined as follows:
3186 <ul>
3187 <li> No two signed integer types shall have the same rank, even if they have the same
3188 representation.
3189 <li> The rank of a signed integer type shall be greater than the rank of any signed integer
3190 type with less precision.
3191 <li> The rank of long long int shall be greater than the rank of long int, which
3192 shall be greater than the rank of int, which shall be greater than the rank of short
3193 int, which shall be greater than the rank of signed char.
3194 <li> The rank of any unsigned integer type shall equal the rank of the corresponding
3195 signed integer type, if any.
3196 <li> The rank of any standard integer type shall be greater than the rank of any extended
3197 integer type with the same width.
3198 <li> The rank of char shall equal the rank of signed char and unsigned char.
3199 <li> The rank of _Bool shall be less than the rank of all other standard integer types.
3200 <li> The rank of any enumerated type shall equal the rank of the compatible integer type
3202 <li> The rank of any extended signed integer type relative to another extended signed
3203 integer type with the same precision is implementation-defined, but still subject to the
3204 other rules for determining the integer conversion rank.
3205 <li> For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
3206 greater rank than T3, then T1 has greater rank than T3.
3207 </ul>
3208 <p><!--para 2 -->
3209 The following may be used in an expression wherever an int or unsigned int may
3210 be used:
3211 <!--page 69 -->
3212 <ul>
3213 <li> An object or expression with an integer type (other than int or unsigned int)
3214 whose integer conversion rank is less than or equal to the rank of int and
3215 unsigned int.
3216 <li> A bit-field of type _Bool, int, signed int, or unsigned int.
3217 </ul>
3218 If an int can represent all values of the original type (as restricted by the width, for a
3219 bit-field), the value is converted to an int; otherwise, it is converted to an unsigned
3220 int. These are called the integer promotions.<sup><a href="#note58"><b>58)</b></a></sup> All other types are unchanged by the
3221 integer promotions.
3222 <p><!--para 3 -->
3223 The integer promotions preserve value including sign. As discussed earlier, whether a
3224 ''plain'' char is treated as signed is implementation-defined.
3225 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
3228 <p><b>Footnotes</b>
3229 <p><small><a name="note58" href="#note58">58)</a> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
3230 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
3231 shift operators, as specified by their respective subclauses.
3232 </small>
3235 <p><!--para 1 -->
3236 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
3239 <p><b>Footnotes</b>
3240 <p><small><a name="note59" href="#note59">59)</a> NaNs do not compare equal to 0 and thus convert to 1.
3241 </small>
3244 <p><!--para 1 -->
3245 When a value with integer type is converted to another integer type other than _Bool, if
3246 the value can be represented by the new type, it is unchanged.
3247 <p><!--para 2 -->
3248 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
3249 subtracting one more than the maximum value that can be represented in the new type
3251 <p><!--para 3 -->
3252 Otherwise, the new type is signed and the value cannot be represented in it; either the
3253 result is implementation-defined or an implementation-defined signal is raised.
3255 <p><b>Footnotes</b>
3256 <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.
3257 </small>
3260 <p><!--para 1 -->
3261 When a finite value of real floating type is converted to an integer type other than _Bool,
3262 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
3263 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note61"><b>61)</b></a></sup>
3266 <!--page 70 -->
3267 <p><!--para 2 -->
3268 When a value of integer type is converted to a real floating type, if the value being
3269 converted can be represented exactly in the new type, it is unchanged. If the value being
3270 converted is in the range of values that can be represented but cannot be represented
3271 exactly, the result is either the nearest higher or nearest lower representable value, chosen
3272 in an implementation-defined manner. If the value being converted is outside the range of
3273 values that can be represented, the behavior is undefined. Results of some implicit
3274 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
3275 required by the new type.
3277 <p><b>Footnotes</b>
3278 <p><small><a name="note61" href="#note61">61)</a> The remaindering operation performed when a value of integer type is converted to unsigned type
3279 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
3280 range of portable real floating values is (-1, Utype_MAX+1).
3281 </small>
3284 <p><!--para 1 -->
3285 When a value of real floating type is converted to a real floating type, if the value being
3286 converted can be represented exactly in the new type, it is unchanged. If the value being
3287 converted is in the range of values that can be represented but cannot be represented
3288 exactly, the result is either the nearest higher or nearest lower representable value, chosen
3289 in an implementation-defined manner. If the value being converted is outside the range of
3290 values that can be represented, the behavior is undefined. Results of some implicit
3291 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
3292 required by the new type.
3295 <p><!--para 1 -->
3296 When a value of complex type is converted to another complex type, both the real and
3297 imaginary parts follow the conversion rules for the corresponding real types.
3300 <p><!--para 1 -->
3301 When a value of real type is converted to a complex type, the real part of the complex
3302 result value is determined by the rules of conversion to the corresponding real type and
3303 the imaginary part of the complex result value is a positive zero or an unsigned zero.
3304 <p><!--para 2 -->
3305 When a value of complex type is converted to a real type, the imaginary part of the
3306 complex value is discarded and the value of the real part is converted according to the
3307 conversion rules for the corresponding real type.
3310 <p><!--para 1 -->
3311 Many operators that expect operands of arithmetic type cause conversions and yield result
3312 types in a similar way. The purpose is to determine a common real type for the operands
3313 and result. For the specified operands, each operand is converted, without change of type
3314 domain, to a type whose corresponding real type is the common real type. Unless
3315 explicitly stated otherwise, the common real type is also the corresponding real type of
3316 the result, whose type domain is the type domain of the operands if they are the same,
3317 and complex otherwise. This pattern is called the usual arithmetic conversions:
3318 <!--page 71 -->
3319 <pre>
3320 First, if the corresponding real type of either operand is long double, the other
3321 operand is converted, without change of type domain, to a type whose
3322 corresponding real type is long double.
3323 Otherwise, if the corresponding real type of either operand is double, the other
3324 operand is converted, without change of type domain, to a type whose
3325 corresponding real type is double.
3326 Otherwise, if the corresponding real type of either operand is float, the other
3327 operand is converted, without change of type domain, to a type whose
3329 Otherwise, the integer promotions are performed on both operands. Then the
3330 following rules are applied to the promoted operands:
3331 If both operands have the same type, then no further conversion is needed.
3332 Otherwise, if both operands have signed integer types or both have unsigned
3333 integer types, the operand with the type of lesser integer conversion rank is
3334 converted to the type of the operand with greater rank.
3335 Otherwise, if the operand that has unsigned integer type has rank greater or
3336 equal to the rank of the type of the other operand, then the operand with
3337 signed integer type is converted to the type of the operand with unsigned
3338 integer type.
3339 Otherwise, if the type of the operand with signed integer type can represent
3340 all of the values of the type of the operand with unsigned integer type, then
3341 the operand with unsigned integer type is converted to the type of the
3342 operand with signed integer type.
3343 Otherwise, both operands are converted to the unsigned integer type
3344 corresponding to the type of the operand with signed integer type.
3345 </pre>
3346 <p><!--para 2 -->
3347 The values of floating operands and of the results of floating expressions may be
3348 represented in greater precision and range than that required by the type; the types are not
3354 <!--page 72 -->
3356 <p><b>Footnotes</b>
3357 <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
3358 float operand to double (and yields a double _Complex result).
3359 </small>
3360 <p><small><a name="note63" href="#note63">63)</a> The cast and assignment operators are still required to remove extra range and precision.
3361 </small>
3365 <h5><a name="6.3.2.1" href="#6.3.2.1">6.3.2.1 Lvalues, arrays, and function designators</a></h5>
3366 <p><!--para 1 -->
3367 An lvalue is an expression (with an object type other than void) that potentially
3368 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
3369 behavior is undefined. When an object is said to have a particular type, the type is
3370 specified by the lvalue used to designate the object. A modifiable lvalue is an lvalue that
3371 does not have array type, does not have an incomplete type, does not have a const-
3372 qualified type, and if it is a structure or union, does not have any member (including,
3373 recursively, any member or element of all contained aggregates or unions) with a const-
3374 qualified type.
3375 <p><!--para 2 -->
3376 Except when it is the operand of the sizeof operator, the unary & operator, the ++
3377 operator, the -- operator, or the left operand of the . operator or an assignment operator,
3378 an lvalue that does not have array type is converted to the value stored in the designated
3379 object (and is no longer an lvalue); this is called lvalue conversion. If the lvalue has
3380 qualified type, the value has the unqualified version of the type of the lvalue; additionally,
3381 if the lvalue has atomic type, the value has the non-atomic version of the type of the
3382 lvalue; otherwise, the value has the type of the lvalue. If the lvalue has an incomplete
3383 type and does not have array type, the behavior is undefined. If the lvalue designates an
3384 object of automatic storage duration that could have been declared with the register
3385 storage class (never had its address taken), and that object is uninitialized (not declared
3386 with an initializer and no assignment to it has been performed prior to use), the behavior
3387 is undefined.
3388 <p><!--para 3 -->
3389 Except when it is the operand of the sizeof operator or the unary & operator, or is a
3390 string literal used to initialize an array, an expression that has type ''array of type'' is
3391 converted to an expression with type ''pointer to type'' that points to the initial element of
3392 the array object and is not an lvalue. If the array object has register storage class, the
3393 behavior is undefined.
3394 <p><!--para 4 -->
3395 A function designator is an expression that has function type. Except when it is the
3396 operand of the sizeof operator<sup><a href="#note65"><b>65)</b></a></sup> or the unary & operator, a function designator with
3397 type ''function returning type'' is converted to an expression that has type ''pointer to
3400 <!--page 73 -->
3401 function returning type''.
3402 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
3403 (<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
3404 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
3405 (<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>).
3407 <p><b>Footnotes</b>
3408 <p><small><a name="note64" href="#note64">64)</a> The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
3409 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
3410 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
3411 as the ''value of an expression''.
3412 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
3413 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
3414 </small>
3415 <p><small><a name="note65" href="#note65">65)</a> Because this conversion does not occur, the operand of the sizeof operator remains a function
3417 </small>
3420 <p><!--para 1 -->
3421 The (nonexistent) value of a void expression (an expression that has type void) shall not
3422 be used in any way, and implicit or explicit conversions (except to void) shall not be
3423 applied to such an expression. If an expression of any other type is evaluated as a void
3424 expression, its value or designator is discarded. (A void expression is evaluated for its
3425 side effects.)
3428 <p><!--para 1 -->
3429 A pointer to void may be converted to or from a pointer to any object type. A pointer to
3430 any object type may be converted to a pointer to void and back again; the result shall
3431 compare equal to the original pointer.
3432 <p><!--para 2 -->
3433 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
3434 the q-qualified version of the type; the values stored in the original and converted pointers
3435 shall compare equal.
3436 <p><!--para 3 -->
3437 An integer constant expression with the value 0, or such an expression cast to type
3438 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
3439 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
3440 to a pointer to any object or function.
3441 <p><!--para 4 -->
3442 Conversion of a null pointer to another pointer type yields a null pointer of that type.
3443 Any two null pointers shall compare equal.
3444 <p><!--para 5 -->
3445 An integer may be converted to any pointer type. Except as previously specified, the
3446 result is implementation-defined, might not be correctly aligned, might not point to an
3447 entity of the referenced type, and might be a trap representation.<sup><a href="#note67"><b>67)</b></a></sup>
3448 <p><!--para 6 -->
3449 Any pointer type may be converted to an integer type. Except as previously specified, the
3450 result is implementation-defined. If the result cannot be represented in the integer type,
3451 the behavior is undefined. The result need not be in the range of values of any integer
3452 type.
3457 <!--page 74 -->
3458 <p><!--para 7 -->
3459 A pointer to an object type may be converted to a pointer to a different object type. If the
3460 resulting pointer is not correctly aligned<sup><a href="#note68"><b>68)</b></a></sup> for the referenced type, the behavior is
3461 undefined. Otherwise, when converted back again, the result shall compare equal to the
3462 original pointer. When a pointer to an object is converted to a pointer to a character type,
3463 the result points to the lowest addressed byte of the object. Successive increments of the
3464 result, up to the size of the object, yield pointers to the remaining bytes of the object.
3465 <p><!--para 8 -->
3466 A pointer to a function of one type may be converted to a pointer to a function of another
3467 type and back again; the result shall compare equal to the original pointer. If a converted
3468 pointer is used to call a function whose type is not compatible with the referenced type,
3469 the behavior is undefined.
3470 <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
3471 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>).
3476 <!--page 75 -->
3478 <p><b>Footnotes</b>
3479 <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>.
3480 </small>
3481 <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
3482 be consistent with the addressing structure of the execution environment.
3483 </small>
3484 <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
3485 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
3486 correctly aligned for a pointer to type C.
3487 </small>
3490 <p><b>Syntax</b>
3491 <p><!--para 1 -->
3492 <pre>
3493 token:
3494 keyword
3495 identifier
3496 constant
3497 string-literal
3498 punctuator
3499 preprocessing-token:
3500 header-name
3501 identifier
3502 pp-number
3503 character-constant
3504 string-literal
3505 punctuator
3506 each non-white-space character that cannot be one of the above
3507 </pre>
3508 <p><b>Constraints</b>
3509 <p><!--para 2 -->
3510 Each preprocessing token that is converted to a token shall have the lexical form of a
3511 keyword, an identifier, a constant, a string literal, or a punctuator.
3512 <p><b>Semantics</b>
3513 <p><!--para 3 -->
3514 A token is the minimal lexical element of the language in translation phases 7 and 8. The
3515 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
3516 A preprocessing token is the minimal lexical element of the language in translation
3517 phases 3 through 6. The categories of preprocessing tokens are: header names,
3518 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
3519 single non-white-space characters that do not lexically match the other preprocessing
3520 token categories.<sup><a href="#note69"><b>69)</b></a></sup> If a ' or a " character matches the last category, the behavior is
3521 undefined. Preprocessing tokens can be separated by white space; this consists of
3522 comments (described later), or white-space characters (space, horizontal tab, new-line,
3523 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
3524 during translation phase 4, white space (or the absence thereof) serves as more than
3525 preprocessing token separation. White space may appear within a preprocessing token
3526 only as part of a header name or between the quotation characters in a character constant
3527 or string literal.
3531 <!--page 76 -->
3533 If the input stream has been parsed into preprocessing tokens up to a given character, the
3534 next preprocessing token is the longest sequence of characters that could constitute a
3535 preprocessing token. There is one exception to this rule: header name preprocessing
3536 tokens are recognized only within #include preprocessing directives and in
3537 implementation-defined locations within #pragma directives. In such contexts, a
3538 sequence of characters that could be either a header name or a string literal is recognized
3539 as the former.
3541 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
3542 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
3543 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
3544 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
3545 not E is a macro name.
3548 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
3549 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
3551 <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>),
3552 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
3553 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
3554 (<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
3558 <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
3559 occur in source files.
3560 </small>
3565 <pre>
3566 keyword: one of
3567 alignof goto union
3568 auto if unsigned
3569 break inline void
3570 case int volatile
3571 char long while
3572 const register _Alignas
3573 continue restrict _Atomic
3574 default return _Bool
3575 do short _Complex
3576 double signed _Generic
3577 else sizeof _Imaginary
3578 enum static _Noreturn
3579 extern struct _Static_assert
3580 float switch _Thread_local
3581 for typedef
3582 </pre>
3586 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
3587 <!--page 77 -->
3591 <p><small><a name="note70" href="#note70">70)</a> One possible specification for imaginary types appears in <a href="#G">annex G</a>.
3592 </small>
3599 <pre>
3600 identifier:
3601 identifier-nondigit
3602 identifier identifier-nondigit
3603 identifier digit
3604 identifier-nondigit:
3605 nondigit
3606 universal-character-name
3607 other implementation-defined characters
3608 nondigit: one of
3609 _ a b c d e f g h i j k l m
3610 n o p q r s t u v w x y z
3611 A B C D E F G H I J K L M
3612 N O P Q R S T U V W X Y Z
3613 digit: one of
3614 0 1 2 3 4 5 6 7 8 9
3615 </pre>
3618 An identifier is a sequence of nondigit characters (including the underscore _, the
3619 lowercase and uppercase Latin letters, and other characters) and digits, which designates
3620 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
3621 There is no specific limit on the maximum length of an identifier.
3623 Each universal character name in an identifier shall designate a character whose encoding
3624 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
3625 shall not be a universal character name designating a character whose encoding falls into
3626 one of the ranges specified in <a href="#D.2">D.2</a>. An implementation may allow multibyte characters
3627 that are not part of the basic source character set to appear in identifiers; which characters
3628 and their correspondence to universal character names is implementation-defined.
3632 <!--page 78 -->
3634 When preprocessing tokens are converted to tokens during translation phase 7, if a
3635 preprocessing token could be converted to either a keyword or an identifier, it is converted
3636 to a keyword.
3639 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
3640 characters in an identifier; the limit for an external name (an identifier that has external
3641 linkage) may be more restrictive than that for an internal name (a macro name or an
3642 identifier that does not have external linkage). The number of significant characters in an
3643 identifier is implementation-defined.
3645 Any identifiers that differ in a significant character are different identifiers. If two
3646 identifiers differ only in nonsignificant characters, the behavior is undefined.
3647 <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>).
3650 <p><small><a name="note71" href="#note71">71)</a> On systems in which linkers cannot accept extended characters, an encoding of the universal character
3651 name may be used in forming valid external identifiers. For example, some otherwise unused
3652 character or sequence of characters may be used to encode the \u in a universal character name.
3653 Extended characters may produce a long external identifier.
3654 </small>
3659 The identifier __func__ shall be implicitly declared by the translator as if,
3660 immediately following the opening brace of each function definition, the declaration
3661 <pre>
3662 static const char __func__[] = "function-name";
3663 </pre>
3664 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note72"><b>72)</b></a></sup>
3666 This name is encoded as if the implicit declaration had been written in the source
3667 character set and then translated into the execution character set as indicated in translation
3668 phase 5.
3670 EXAMPLE Consider the code fragment:
3671 <pre>
3673 void myfunc(void)
3674 {
3675 printf("%s\n", __func__);
3676 /* ... */
3677 }
3678 </pre>
3679 Each time the function is called, it will print to the standard output stream:
3680 <pre>
3681 myfunc
3682 </pre>
3689 <!--page 79 -->
3692 <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
3693 identifier is explicitly declared using the name __func__, the behavior is undefined.
3694 </small>
3699 <pre>
3700 universal-character-name:
3701 \u hex-quad
3702 \U hex-quad hex-quad
3703 hex-quad:
3704 hexadecimal-digit hexadecimal-digit
3705 hexadecimal-digit hexadecimal-digit
3706 </pre>
3709 A universal character name shall not specify a character whose short identifier is less than
3714 Universal character names may be used in identifiers, character constants, and string
3715 literals to designate characters that are not in the basic character set.
3718 The universal character name \Unnnnnnnn designates the character whose eight-digit
3719 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note74"><b>74)</b></a></sup> Similarly, the universal
3720 character name \unnnn designates the character whose four-digit short identifier is nnnn
3721 (and whose eight-digit short identifier is 0000nnnn).
3726 <!--page 80 -->
3729 <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
3730 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
3731 UTF-16).
3733 </small>
3734 <p><small><a name="note74" href="#note74">74)</a> Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
3735 </small>
3740 <pre>
3741 constant:
3742 integer-constant
3743 floating-constant
3744 enumeration-constant
3745 character-constant
3746 </pre>
3749 Each constant shall have a type and the value of a constant shall be in the range of
3750 representable values for its type.
3753 Each constant has a type, determined by its form and value, as detailed later.
3758 <!--page 81 -->
3759 <pre>
3760 integer-constant:
3764 decimal-constant:
3765 nonzero-digit
3766 decimal-constant digit
3767 octal-constant:
3768 0
3769 octal-constant octal-digit
3770 hexadecimal-constant:
3771 hexadecimal-prefix hexadecimal-digit
3772 hexadecimal-constant hexadecimal-digit
3773 hexadecimal-prefix: one of
3775 nonzero-digit: one of
3776 1 2 3 4 5 6 7 8 9
3777 octal-digit: one of
3778 0 1 2 3 4 5 6 7
3779 hexadecimal-digit: one of
3780 0 1 2 3 4 5 6 7 8 9
3781 a b c d e f
3782 A B C D E F
3783 integer-suffix:
3785 unsigned-suffix long-long-suffix
3788 unsigned-suffix: one of
3789 u U
3790 long-suffix: one of
3791 l L
3792 long-long-suffix: one of
3793 ll LL
3794 </pre>
3797 An integer constant begins with a digit, but has no period or exponent part. It may have a
3798 prefix that specifies its base and a suffix that specifies its type.
3800 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3801 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3803 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3808 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3810 The type of an integer constant is the first of the corresponding list in which its value can
3811 be represented.
3812 <!--page 82 -->
3813 <pre>
3814 Octal or Hexadecimal
3815 </pre>
3816 Suffix Decimal Constant Constant
3818 none int int
3819 <pre>
3820 long int unsigned int
3821 long long int long int
3822 unsigned long int
3823 long long int
3824 unsigned long long int
3825 </pre>
3827 u or U unsigned int unsigned int
3828 <pre>
3829 unsigned long int unsigned long int
3830 unsigned long long int unsigned long long int
3831 </pre>
3833 l or L long int long int
3834 <pre>
3835 long long int unsigned long int
3836 long long int
3837 unsigned long long int
3838 </pre>
3840 Both u or U unsigned long int unsigned long int
3841 and l or L unsigned long long int unsigned long long int
3843 ll or LL long long int long long int
3844 <pre>
3845 unsigned long long int
3846 </pre>
3848 Both u or U unsigned long long int unsigned long long int
3849 and ll or LL
3851 If an integer constant cannot be represented by any type in its list, it may have an
3852 extended integer type, if the extended integer type can represent its value. If all of the
3853 types in the list for the constant are signed, the extended integer type shall be signed. If
3854 all of the types in the list for the constant are unsigned, the extended integer type shall be
3855 unsigned. If the list contains both signed and unsigned types, the extended integer type
3856 may be signed or unsigned. If an integer constant cannot be represented by any type in
3857 its list and has no extended integer type, then the integer constant has no type.
3858 <!--page 83 -->
3863 <!--page 84 -->
3864 <pre>
3865 floating-constant:
3866 decimal-floating-constant
3867 hexadecimal-floating-constant
3868 decimal-floating-constant:
3871 hexadecimal-floating-constant:
3872 hexadecimal-prefix hexadecimal-fractional-constant
3874 hexadecimal-prefix hexadecimal-digit-sequence
3876 fractional-constant:
3878 digit-sequence .
3879 exponent-part:
3882 sign: one of
3883 + -
3884 digit-sequence:
3885 digit
3886 digit-sequence digit
3887 hexadecimal-fractional-constant:
3889 hexadecimal-digit-sequence
3890 hexadecimal-digit-sequence .
3891 binary-exponent-part:
3894 hexadecimal-digit-sequence:
3895 hexadecimal-digit
3896 hexadecimal-digit-sequence hexadecimal-digit
3897 floating-suffix: one of
3898 f l F L
3899 </pre>
3902 A floating constant has a significand part that may be followed by an exponent part and a
3903 suffix that specifies its type. The components of the significand part may include a digit
3904 sequence representing the whole-number part, followed by a period (.), followed by a
3905 digit sequence representing the fraction part. The components of the exponent part are an
3906 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
3907 Either the whole-number part or the fraction part has to be present; for decimal floating
3908 constants, either the period or the exponent part has to be present.
3911 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
3912 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
3913 floating constants, the exponent indicates the power of 10 by which the significand part is
3914 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
3915 by which the significand part is to be scaled. For decimal floating constants, and also for
3916 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
3917 the nearest representable value, or the larger or smaller representable value immediately
3918 adjacent to the nearest representable value, chosen in an implementation-defined manner.
3919 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
3920 correctly rounded.
3922 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
3923 type float. If suffixed by the letter l or L, it has type long double.
3925 Floating constants are converted to internal format as if at translation-time. The
3926 conversion of a floating constant shall not raise an exceptional condition or a floating-
3927 point exception at execution time. All floating constants of the same source form<sup><a href="#note75"><b>75)</b></a></sup> shall
3928 convert to the same internal format with the same value.
3931 The implementation should produce a diagnostic message if a hexadecimal constant
3932 cannot be represented exactly in its evaluation format; the implementation should then
3933 proceed with the translation of the program.
3935 The translation-time conversion of floating constants should match the execution-time
3936 conversion of character strings by library functions, such as strtod, given matching
3937 inputs suitable for both conversions, the same result format, and default execution-time
3940 <!--page 85 -->
3943 <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
3944 convert to the same internal format and value.
3945 </small>
3946 <p><small><a name="note76" href="#note76">76)</a> The specification for the library functions recommends more accurate conversion than required for
3948 </small>
3953 <pre>
3954 enumeration-constant:
3955 identifier
3956 </pre>
3959 An identifier declared as an enumeration constant has type int.
3965 <!--page 86 -->
3966 <pre>
3967 character-constant:
3968 ' c-char-sequence '
3969 L' c-char-sequence '
3970 u' c-char-sequence '
3971 U' c-char-sequence '
3972 c-char-sequence:
3973 c-char
3974 c-char-sequence c-char
3975 c-char:
3976 any member of the source character set except
3977 the single-quote ', backslash \, or new-line character
3978 escape-sequence
3979 escape-sequence:
3980 simple-escape-sequence
3981 octal-escape-sequence
3982 hexadecimal-escape-sequence
3983 universal-character-name
3984 simple-escape-sequence: one of
3985 \' \" \? \\
3986 \a \b \f \n \r \t \v
3987 octal-escape-sequence:
3988 \ octal-digit
3989 \ octal-digit octal-digit
3990 \ octal-digit octal-digit octal-digit
3991 hexadecimal-escape-sequence:
3992 \x hexadecimal-digit
3993 hexadecimal-escape-sequence hexadecimal-digit
3994 </pre>
3995 <p><b>Description</b>
3996 <p><!--para 2 -->
3997 An integer character constant is a sequence of one or more multibyte characters enclosed
3998 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
3999 letter L, u, or U. With a few exceptions detailed later, the elements of the sequence are
4000 any members of the source character set; they are mapped in an implementation-defined
4001 manner to members of the execution character set.
4002 <p><!--para 3 -->
4003 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
4004 arbitrary integer values are representable according to the following table of escape
4005 sequences:
4006 <pre>
4007 single quote ' \'
4008 double quote " \"
4009 question mark ? \?
4010 backslash \ \\
4011 octal character \octal digits
4012 hexadecimal character \x hexadecimal digits
4013 </pre>
4015 The double-quote " and question-mark ? are representable either by themselves or by the
4016 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
4017 shall be represented, respectively, by the escape sequences \' and \\.
4019 The octal digits that follow the backslash in an octal escape sequence are taken to be part
4020 of the construction of a single character for an integer character constant or of a single
4021 wide character for a wide character constant. The numerical value of the octal integer so
4022 formed specifies the value of the desired character or wide character.
4024 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
4025 sequence are taken to be part of the construction of a single character for an integer
4026 character constant or of a single wide character for a wide character constant. The
4027 numerical value of the hexadecimal integer so formed specifies the value of the desired
4028 character or wide character.
4030 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
4031 constitute the escape sequence.
4033 In addition, characters not in the basic character set are representable by universal
4034 character names and certain nongraphic characters are representable by escape sequences
4035 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
4037 <!--page 87 -->
4040 The value of an octal or hexadecimal escape sequence shall be in the range of
4041 representable values for the corresponding type:
4042 <pre>
4043 Prefix Corresponding Type
4044 none unsigned char
4045 L the unsigned type corresponding to wchar_t
4046 u char16_t
4047 U char32_t
4048 </pre>
4051 An integer character constant has type int. The value of an integer character constant
4052 containing a single character that maps to a single-byte execution character is the
4053 numerical value of the representation of the mapped character interpreted as an integer.
4054 The value of an integer character constant containing more than one character (e.g.,
4055 'ab'), or containing a character or escape sequence that does not map to a single-byte
4056 execution character, is implementation-defined. If an integer character constant contains
4057 a single character or escape sequence, its value is the one that results when an object with
4058 type char whose value is that of the single character or escape sequence is converted to
4059 type int.
4061 A wide character constant prefixed by the letter L has type wchar_t, an integer type
4062 defined in the <a href="#7.19"><stddef.h></a> header; a wide character constant prefixed by the letter u or
4063 U has type char16_t or char32_t, respectively, unsigned integer types defined in the
4064 <a href="#7.27"><uchar.h></a> header. The value of a wide character constant containing a single
4065 multibyte character that maps to a single member of the extended execution character set
4066 is the wide character corresponding to that multibyte character, as defined by the
4067 mbtowc, mbrtoc16, or mbrtoc32 function as appropriate for its type, with an
4068 implementation-defined current locale. The value of a wide character constant containing
4069 more than one multibyte character or a single multibyte character that maps to multiple
4070 members of the extended execution character set, or containing a multibyte character or
4071 escape sequence not represented in the extended execution character set, is
4072 implementation-defined.
4077 EXAMPLE 2 Consider implementations that use two's complement representation for integers and eight
4078 bits for objects that have type char. In an implementation in which type char has the same range of
4079 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
4080 same range of values as unsigned char, the character constant '\xFF' has the value +255.
4085 <!--page 88 -->
4087 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
4088 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
4089 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
4090 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
4091 escape sequence is terminated after three octal digits. (The value of this two-character integer character
4092 constant is implementation-defined.)
4095 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
4096 L'\1234' specifies the implementation-defined value that results from the combination of the values
4099 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbtowc function
4100 (<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>).
4103 <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,
4104 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
4105 </small>
4110 <pre>
4111 string-literal:
4113 encoding-prefix:
4114 u8
4115 u
4116 U
4117 L
4118 s-char-sequence:
4119 s-char
4120 s-char-sequence s-char
4121 s-char:
4122 any member of the source character set except
4123 the double-quote ", backslash \, or new-line character
4124 escape-sequence
4125 </pre>
4126 <p><b>Constraints</b>
4127 <p><!--para 2 -->
4128 A sequence of adjacent string literal tokens shall not include both a wide string literal and
4129 a UTF-8 string literal.
4130 <p><b>Description</b>
4131 <p><!--para 3 -->
4132 A character string literal is a sequence of zero or more multibyte characters enclosed in
4134 A wide string literal is the same, except prefixed by the letter L, u, or U.
4135 <p><!--para 4 -->
4136 The same considerations apply to each element of the sequence in a string literal as if it
4137 were in an integer character constant (for a character or UTF-8 string literal) or a wide
4138 character constant (for a wide string literal), except that the single-quote ' is
4139 representable either by itself or by the escape sequence \', but the double-quote " shall
4140 <!--page 89 -->
4141 be represented by the escape sequence \".
4142 <p><b>Semantics</b>
4143 <p><!--para 5 -->
4144 In translation phase 6, the multibyte character sequences specified by any sequence of
4145 adjacent character and identically-prefixed string literal tokens are concatenated into a
4146 single multibyte character sequence. If any of the tokens has an encoding prefix, the
4147 resulting multibyte character sequence is treated as having the same prefix; otherwise, it
4148 is treated as a character string literal. Whether differently-prefixed wide string literal
4149 tokens can be concatenated and, if so, the treatment of the resulting multibyte character
4150 sequence are implementation-defined.
4151 <p><!--para 6 -->
4152 In translation phase 7, a byte or code of value zero is appended to each multibyte
4153 character sequence that results from a string literal or literals.<sup><a href="#note78"><b>78)</b></a></sup> The multibyte character
4154 sequence is then used to initialize an array of static storage duration and length just
4155 sufficient to contain the sequence. For character string literals, the array elements have
4156 type char, and are initialized with the individual bytes of the multibyte character
4157 sequence. For UTF-8 string literals, the array elements have type char, and are
4158 initialized with the characters of the multibyte character sequence, as encoded in UTF-8.
4159 For wide string literals prefixed by the letter L, the array elements have type wchar_t
4160 and are initialized with the sequence of wide characters corresponding to the multibyte
4161 character sequence, as defined by the mbstowcs function with an implementation-
4162 defined current locale. For wide string literals prefixed by the letter u or U, the array
4163 elements have type char16_t or char32_t, respectively, and are initialized with the
4164 sequence of wide characters corresponding to the multibyte character sequence, as
4165 defined by successive calls to the mbrtoc16, or mbrtoc32 function as appropriate for
4166 its type, with an implementation-defined current locale. The value of a string literal
4167 containing a multibyte character or escape sequence not represented in the execution
4168 character set is implementation-defined.
4169 <p><!--para 7 -->
4170 It is unspecified whether these arrays are distinct provided their elements have the
4171 appropriate values. If the program attempts to modify such an array, the behavior is
4172 undefined.
4173 <p><!--para 8 -->
4174 EXAMPLE 1 This pair of adjacent character string literals
4175 <pre>
4177 </pre>
4178 produces a single character string literal containing the two characters whose values are '\x12' and '3',
4179 because escape sequences are converted into single members of the execution character set just prior to
4180 adjacent string literal concatenation.
4182 <p><!--para 9 -->
4183 EXAMPLE 2 Each of the sequences of adjacent string literal tokens
4187 <!--page 90 -->
4188 <pre>
4193 </pre>
4194 is equivalent to the string literal
4195 <pre>
4197 </pre>
4198 Likewise, each of the sequences
4199 <pre>
4204 </pre>
4205 is equivalent to
4206 <pre>
4208 </pre>
4210 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbstowcs
4211 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>).
4213 <p><b>Footnotes</b>
4214 <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
4215 \0 escape sequence.
4216 </small>
4219 <p><b>Syntax</b>
4220 <p><!--para 1 -->
4221 <pre>
4222 punctuator: one of
4223 [ ] ( ) { } . ->
4224 ++ -- & * + - ~ !
4225 / % << >> < > <= >= == != ^ | && ||
4226 ? : ; ...
4227 = *= /= %= += -= <<= >>= &= ^= |=
4228 , # ##
4229 <: :> <% %> %: %:%:
4230 </pre>
4231 <p><b>Semantics</b>
4232 <p><!--para 2 -->
4233 A punctuator is a symbol that has independent syntactic and semantic significance.
4234 Depending on context, it may specify an operation to be performed (which in turn may
4235 yield a value or a function designator, produce a side effect, or some combination thereof)
4236 in which case it is known as an operator (other forms of operator also exist in some
4237 contexts). An operand is an entity on which an operator acts.
4238 <!--page 91 -->
4239 <p><!--para 3 -->
4241 <pre>
4242 <: :> <% %> %: %:%:
4243 </pre>
4244 behave, respectively, the same as the six tokens
4245 <pre>
4246 [ ] { } # ##
4247 </pre>
4249 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
4252 <p><b>Footnotes</b>
4253 <p><small><a name="note79" href="#note79">79)</a> These tokens are sometimes called ''digraphs''.
4254 </small>
4255 <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
4256 interchanged.
4257 </small>
4260 <p><b>Syntax</b>
4261 <p><!--para 1 -->
4262 <pre>
4263 header-name:
4264 < h-char-sequence >
4266 h-char-sequence:
4267 h-char
4268 h-char-sequence h-char
4269 h-char:
4270 any member of the source character set except
4271 the new-line character and >
4272 q-char-sequence:
4273 q-char
4274 q-char-sequence q-char
4275 q-char:
4276 any member of the source character set except
4277 the new-line character and "
4278 </pre>
4281 The sequences in both forms of header names are mapped in an implementation-defined
4284 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
4285 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
4290 <!--page 92 -->
4291 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note81"><b>81)</b></a></sup> Header name
4292 preprocessing tokens are recognized only within #include preprocessing directives and
4293 in implementation-defined locations within #pragma directives.<sup><a href="#note82"><b>82)</b></a></sup>
4295 EXAMPLE The following sequence of characters:
4296 <pre>
4299 #define const.member@$
4300 </pre>
4301 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
4302 by a { on the left and a } on the right).
4303 <pre>
4306 {#}{define} {const}{.}{member}{@}{$}
4307 </pre>
4312 <p><small><a name="note81" href="#note81">81)</a> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
4313 </small>
4314 <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>.
4315 </small>
4320 <pre>
4321 pp-number:
4322 digit
4323 . digit
4324 pp-number digit
4325 pp-number identifier-nondigit
4326 pp-number e sign
4327 pp-number E sign
4328 pp-number p sign
4329 pp-number P sign
4330 pp-number .
4331 </pre>
4334 A preprocessing number begins with a digit optionally preceded by a period (.) and may
4335 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
4336 p+, p-, P+, or P-.
4338 Preprocessing number tokens lexically include all floating and integer constant tokens.
4341 A preprocessing number does not have type or a value; it acquires both after a successful
4342 conversion (as part of translation phase 7) to a floating constant token or an integer
4343 constant token.
4346 <!--page 93 -->
4350 Except within a character constant, a string literal, or a comment, the characters /*
4351 introduce a comment. The contents of such a comment are examined only to identify
4352 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note83"><b>83)</b></a></sup>
4354 Except within a character constant, a string literal, or a comment, the characters //
4355 introduce a comment that includes all multibyte characters up to, but not including, the
4356 next new-line character. The contents of such a comment are examined only to identify
4357 multibyte characters and to find the terminating new-line character.
4359 EXAMPLE
4360 <pre>
4361 "a//b" // four-character string literal
4362 #include "//e" // undefined behavior
4363 // */ // comment, not syntax error
4364 f = g/**//h; // equivalent to f = g / h;
4365 //\
4366 i(); // part of a two-line comment
4367 /\
4368 / j(); // part of a two-line comment
4369 #define glue(x,y) x##y
4370 glue(/,/) k(); // syntax error, not comment
4371 /*//*/ l(); // equivalent to l();
4372 m = n//**/o
4373 + p; // equivalent to m = n + p;
4374 </pre>
4379 <!--page 94 -->
4383 </small>
4387 An expression is a sequence of operators and operands that specifies computation of a
4388 value, or that designates an object or a function, or that generates side effects, or that
4389 performs a combination thereof. The value computations of the operands of an operator
4390 are sequenced before the value computation of the result of the operator.
4392 If a side effect on a scalar object is unsequenced relative to either a different side effect
4393 on the same scalar object or a value computation using the value of the same scalar
4394 object, the behavior is undefined. If there are multiple allowable orderings of the
4395 subexpressions of an expression, the behavior is undefined if such an unsequenced side
4398 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note85"><b>85)</b></a></sup> Except as specified
4399 later, side effects and value computations of subexpressions are unsequenced.<sup><a href="#note86"><b>86)</b></a></sup> *
4401 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
4402 collectively described as bitwise operators) are required to have operands that have
4403 integer type. These operators yield values that depend on the internal representations of
4404 integers, and have implementation-defined and undefined aspects for signed types.
4406 If an exceptional condition occurs during the evaluation of an expression (that is, if the
4407 result is not mathematically defined or not in the range of representable values for its
4408 type), the behavior is undefined.
4412 <!--page 95 -->
4414 The effective type of an object for an access to its stored value is the declared type of the
4415 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
4416 lvalue having a type that is not a character type, then the type of the lvalue becomes the
4417 effective type of the object for that access and for subsequent accesses that do not modify
4418 the stored value. If a value is copied into an object having no declared type using
4419 memcpy or memmove, or is copied as an array of character type, then the effective type
4420 of the modified object for that access and for subsequent accesses that do not modify the
4421 value is the effective type of the object from which the value is copied, if it has one. For
4422 all other accesses to an object having no declared type, the effective type of the object is
4423 simply the type of the lvalue used for the access.
4425 An object shall have its stored value accessed only by an lvalue expression that has one of
4427 <ul>
4428 <li> a type compatible with the effective type of the object,
4429 <li> a qualified version of a type compatible with the effective type of the object,
4430 <li> a type that is the signed or unsigned type corresponding to the effective type of the
4431 object,
4432 <li> a type that is the signed or unsigned type corresponding to a qualified version of the
4433 effective type of the object,
4434 <li> an aggregate or union type that includes one of the aforementioned types among its
4435 members (including, recursively, a member of a subaggregate or contained union), or
4436 <li> a character type.
4437 </ul>
4439 A floating expression may be contracted, that is, evaluated as though it were a single
4440 operation, thereby omitting rounding errors implied by the source code and the
4441 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
4442 way to disallow contracted expressions. Otherwise, whether and how expressions are
4444 <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>).
4447 <!--page 96 -->
4450 <p><small><a name="note84" href="#note84">84)</a> This paragraph renders undefined statement expressions such as
4452 <pre>
4453 i = ++i + 1;
4454 a[i++] = i;
4455 </pre>
4456 while allowing
4458 <pre>
4459 i = i + 1;
4460 a[i] = i;
4461 </pre>
4463 </small>
4464 <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
4465 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
4466 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
4467 <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
4468 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
4469 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
4471 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
4472 indicated in each subclause by the syntax for the expressions discussed therein.
4473 </small>
4474 <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
4475 indeterminately sequenced evaluations of its subexpressions need not be performed consistently in
4476 different evaluations.
4477 </small>
4479 </small>
4480 <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.
4481 </small>
4482 <p><small><a name="note89" href="#note89">89)</a> The intermediate operations in the contracted expression are evaluated as if to infinite precision and
4483 range, while the final operation is rounded to the format determined by the expression evaluation
4484 method. A contracted expression might also omit the raising of floating-point exceptions.
4485 </small>
4486 <p><small><a name="note90" href="#note90">90)</a> This license is specifically intended to allow implementations to exploit fast machine instructions that
4487 combine multiple C operators. As contractions potentially undermine predictability, and can even
4488 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
4489 documented.
4490 </small>
4495 <pre>
4496 primary-expression:
4497 identifier
4498 constant
4499 string-literal
4500 ( expression )
4501 generic-selection
4502 </pre>
4505 An identifier is a primary expression, provided it has been declared as designating an
4506 object (in which case it is an lvalue) or a function (in which case it is a function
4509 A constant is a primary expression. Its type depends on its form and value, as detailed in
4512 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>.
4514 A parenthesized expression is a primary expression. Its type and value are identical to
4515 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
4516 expression if the unparenthesized expression is, respectively, an lvalue, a function
4517 designator, or a void expression.
4521 <p><small><a name="note91" href="#note91">91)</a> Thus, an undeclared identifier is a violation of the syntax.
4522 </small>
4527 <pre>
4528 generic-selection:
4529 _Generic ( assignment-expression , generic-assoc-list )
4530 generic-assoc-list:
4531 generic-association
4532 generic-assoc-list , generic-association
4533 generic-association:
4534 type-name : assignment-expression
4535 default : assignment-expression
4536 </pre>
4539 A generic selection shall have no more than one default generic association. The type
4540 name in a generic association shall specify a complete object type other than a variably
4542 <!--page 97 -->
4543 modified type. No two generic associations in the same generic selection shall specify
4544 compatible types. The controlling expression of a generic selection shall have type
4545 compatible with at most one of the types named in its generic association list. If a
4546 generic selection has no default generic association, its controlling expression shall
4547 have type compatible with exactly one of the types named in its generic association list.
4550 The controlling expression of a generic selection is not evaluated. If a generic selection
4551 has a generic association with a type name that is compatible with the type of the
4552 controlling expression, then the result expression of the generic selection is the
4553 expression in that generic association. Otherwise, the result expression of the generic
4554 selection is the expression in the default generic association. None of the expressions
4555 from any other generic association of the generic selection is evaluated.
4557 The type and value of a generic selection are identical to those of its result expression. It
4558 is an lvalue, a function designator, or a void expression if its result expression is,
4559 respectively, an lvalue, a function designator, or a void expression.
4561 EXAMPLE The cbrt type-generic macro could be implemented as follows:
4562 <pre>
4563 #define cbrt(X) _Generic((X), \
4564 long double: cbrtl, \
4565 default: cbrt, \
4566 float: cbrtf \
4567 )(X)
4568 </pre>
4574 <!--page 98 -->
4575 <pre>
4576 postfix-expression:
4577 primary-expression
4578 postfix-expression [ expression ]
4580 postfix-expression . identifier
4581 postfix-expression -> identifier
4582 postfix-expression ++
4583 postfix-expression --
4584 ( type-name ) { initializer-list }
4585 ( type-name ) { initializer-list , }
4586 argument-expression-list:
4587 assignment-expression
4588 argument-expression-list , assignment-expression
4589 </pre>
4594 One of the expressions shall have type ''pointer to complete object type'', the other
4595 expression shall have integer type, and the result has type ''type''.
4598 A postfix expression followed by an expression in square brackets [] is a subscripted
4599 designation of an element of an array object. The definition of the subscript operator []
4600 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
4601 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
4602 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
4603 element of E1 (counting from zero).
4605 Successive subscript operators designate an element of a multidimensional array object.
4607 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
4608 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
4609 implicitly as a result of subscripting, the result is the referenced (n - 1)-dimensional
4610 array, which itself is converted into a pointer if used as other than an lvalue. It follows
4611 from this that arrays are stored in row-major order (last subscript varies fastest).
4613 EXAMPLE Consider the array object defined by the declaration
4614 <pre>
4616 </pre>
4617 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
4618 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
4619 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
4620 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
4621 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
4622 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
4623 yields an int.
4625 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
4631 The expression that denotes the called function<sup><a href="#note92"><b>92)</b></a></sup> shall have type pointer to function
4632 returning void or returning a complete object type other than an array type.
4634 If the expression that denotes the called function has a type that includes a prototype, the
4635 number of arguments shall agree with the number of parameters. Each argument shall
4638 <!--page 99 -->
4639 have a type such that its value may be assigned to an object with the unqualified version
4640 of the type of its corresponding parameter.
4643 A postfix expression followed by parentheses () containing a possibly empty, comma-
4644 separated list of expressions is a function call. The postfix expression denotes the called
4645 function. The list of expressions specifies the arguments to the function.
4647 An argument may be an expression of any complete object type. In preparing for the call
4648 to a function, the arguments are evaluated, and each parameter is assigned the value of the
4651 If the expression that denotes the called function has type pointer to function returning an
4652 object type, the function call expression has the same type as that object type, and has the
4653 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void. *
4655 If the expression that denotes the called function has a type that does not include a
4656 prototype, the integer promotions are performed on each argument, and arguments that
4657 have type float are promoted to double. These are called the default argument
4658 promotions. If the number of arguments does not equal the number of parameters, the
4659 behavior is undefined. If the function is defined with a type that includes a prototype, and
4660 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
4661 promotion are not compatible with the types of the parameters, the behavior is undefined.
4662 If the function is defined with a type that does not include a prototype, and the types of
4663 the arguments after promotion are not compatible with those of the parameters after
4664 promotion, the behavior is undefined, except for the following cases:
4665 <ul>
4666 <li> one promoted type is a signed integer type, the other promoted type is the
4667 corresponding unsigned integer type, and the value is representable in both types;
4668 <li> both types are pointers to qualified or unqualified versions of a character type or
4669 void.
4670 </ul>
4672 If the expression that denotes the called function has a type that does include a prototype,
4673 the arguments are implicitly converted, as if by assignment, to the types of the
4674 corresponding parameters, taking the type of each parameter to be the unqualified version
4675 of its declared type. The ellipsis notation in a function prototype declarator causes
4676 argument type conversion to stop after the last declared parameter. The default argument
4677 promotions are performed on trailing arguments.
4681 <!--page 100 -->
4683 No other conversions are performed implicitly; in particular, the number and types of
4684 arguments are not compared with those of the parameters in a function definition that
4685 does not include a function prototype declarator.
4687 If the function is defined with a type that is not compatible with the type (of the
4688 expression) pointed to by the expression that denotes the called function, the behavior is
4689 undefined.
4691 There is a sequence point after the evaluations of the function designator and the actual
4692 arguments but before the actual call. Every evaluation in the calling function (including
4693 other function calls) that is not otherwise specifically sequenced before or after the
4694 execution of the body of the called function is indeterminately sequenced with respect to
4697 Recursive function calls shall be permitted, both directly and indirectly through any chain
4698 of other functions.
4700 EXAMPLE In the function call
4701 <pre>
4702 (*pf[f1()]) (f2(), f3() + f4())
4703 </pre>
4704 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
4705 the function pointed to by pf[f1()] is called.
4707 <p><b> Forward references</b>: function declarators (including prototypes) (<a href="#6.7.6.3">6.7.6.3</a>), function
4708 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>).
4711 <p><small><a name="note92" href="#note92">92)</a> Most often, this is the result of converting an identifier that is a function designator.
4712 </small>
4713 <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
4714 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
4715 change the value of the object pointed to. A parameter declared to have array or function type is
4717 </small>
4718 <p><small><a name="note94" href="#note94">94)</a> In other words, function executions do not ''interleave'' with each other.
4719 </small>
4724 The first operand of the . operator shall have an atomic, qualified, or unqualified
4725 structure or union type, and the second operand shall name a member of that type.
4727 The first operand of the -> operator shall have type ''pointer to atomic, qualified, or
4728 unqualified structure'' or ''pointer to atomic, qualified, or unqualified union'', and the
4729 second operand shall name a member of the type pointed to.
4732 A postfix expression followed by the . operator and an identifier designates a member of
4733 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
4734 the first expression is an lvalue. If the first expression has qualified type, the result has
4735 the so-qualified version of the type of the designated member.
4737 <!--page 101 -->
4739 A postfix expression followed by the -> operator and an identifier designates a member
4740 of a structure or union object. The value is that of the named member of the object to
4741 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
4742 a qualified type, the result has the so-qualified version of the type of the designated
4743 member.
4745 Accessing a member of an atomic structure or union object results in undefined
4748 One special guarantee is made in order to simplify the use of unions: if a union contains
4749 several structures that share a common initial sequence (see below), and if the union
4750 object currently contains one of these structures, it is permitted to inspect the common
4751 initial part of any of them anywhere that a declaration of the completed type of the union
4752 is visible. Two structures share a common initial sequence if corresponding members
4753 have compatible types (and, for bit-fields, the same widths) for a sequence of one or more
4754 initial members.
4756 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
4757 union, f().x is a valid postfix expression but is not an lvalue.
4760 EXAMPLE 2 In:
4761 <pre>
4762 struct s { int i; const int ci; };
4763 struct s s;
4764 const struct s cs;
4765 volatile struct s vs;
4766 </pre>
4767 the various members have the types:
4768 <pre>
4769 s.i int
4770 s.ci const int
4771 cs.i const int
4772 cs.ci const int
4773 vs.i volatile int
4774 vs.ci volatile const int
4775 </pre>
4780 <!--page 102 -->
4782 EXAMPLE 3 The following is a valid fragment:
4783 <pre>
4784 union {
4785 struct {
4786 int alltypes;
4787 } n;
4788 struct {
4789 int type;
4790 int intnode;
4791 } ni;
4792 struct {
4793 int type;
4794 double doublenode;
4795 } nf;
4796 } u;
4797 u.nf.type = 1;
4799 /* ... */
4800 if (u.n.alltypes == 1)
4801 if (sin(u.nf.doublenode) == 0.0)
4802 /* ... */
4803 </pre>
4804 The following is not a valid fragment (because the union type is not visible within function f):
4805 <pre>
4806 struct t1 { int m; };
4807 struct t2 { int m; };
4808 int f(struct t1 *p1, struct t2 *p2)
4809 {
4812 return p1->m;
4813 }
4814 int g()
4815 {
4816 union {
4817 struct t1 s1;
4818 struct t2 s2;
4819 } u;
4820 /* ... */
4822 }
4823 </pre>
4825 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
4827 <!--page 103 -->
4830 <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
4831 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
4832 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
4833 punning''). This might be a trap representation.
4834 </small>
4835 <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
4837 </small>
4838 <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
4839 with access to a member from another thread, where at least one access is a modification. Members
4840 can be safely accessed using a non-atomic object which is assigned to or from the atomic object.
4841 </small>
4843 <h5><a name="6.5.2.4" href="#6.5.2.4">6.5.2.4 Postfix increment and decrement operators</a></h5>
4846 The operand of the postfix increment or decrement operator shall have atomic, qualified,
4847 or unqualified real or pointer type, and shall be a modifiable lvalue.
4850 The result of the postfix ++ operator is the value of the operand. As a side effect, the
4851 value of the operand object is incremented (that is, the value 1 of the appropriate type is
4852 added to it). See the discussions of additive operators and compound assignment for
4853 information on constraints, types, and conversions and the effects of operations on
4854 pointers. The value computation of the result is sequenced before the side effect of
4855 updating the stored value of the operand. With respect to an indeterminately-sequenced
4856 function call, the operation of postfix ++ is a single evaluation. Postfix ++ on an object
4857 with atomic type is a read-modify-write operation with memory_order_seq_cst
4860 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
4861 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
4862 it).
4863 <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>).
4866 <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
4867 where T is the type of E:
4869 <pre>
4870 T tmp;
4871 T result = E;
4872 do {
4873 tmp = result + 1;
4875 </pre>
4876 with result being the result of the operation.
4877 </small>
4882 The type name shall specify a complete object type or an array of unknown size, but not a
4883 variable length array type.
4885 All the constraints for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.
4888 A postfix expression that consists of a parenthesized type name followed by a brace-
4889 enclosed list of initializers is a compound literal. It provides an unnamed object whose
4893 <!--page 104 -->
4895 If the type name specifies an array of unknown size, the size is determined by the
4896 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
4897 completed array type. Otherwise (when the type name specifies an object type), the type
4898 of the compound literal is that specified by the type name. In either case, the result is an
4899 lvalue.
4901 The value of the compound literal is that of an unnamed object initialized by the
4902 initializer list. If the compound literal occurs outside the body of a function, the object
4903 has static storage duration; otherwise, it has automatic storage duration associated with
4904 the enclosing block.
4906 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>
4908 String literals, and compound literals with const-qualified types, need not designate
4911 EXAMPLE 1 The file scope definition
4912 <pre>
4914 </pre>
4915 initializes p to point to the first element of an array of two ints, the first having the value two and the
4916 second, four. The expressions in this compound literal are required to be constant. The unnamed object
4917 has static storage duration.
4920 EXAMPLE 2 In contrast, in
4921 <pre>
4922 void f(void)
4923 {
4924 int *p;
4925 /*...*/
4926 p = (int [2]){*p};
4927 /*...*/
4928 }
4929 </pre>
4930 p is assigned the address of the first element of an array of two ints, the first having the value previously
4931 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
4932 unnamed object has automatic storage duration.
4935 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
4936 created using compound literals can be passed to functions without depending on member order:
4937 <pre>
4940 </pre>
4941 Or, if drawline instead expected pointers to struct point:
4945 <!--page 105 -->
4946 <pre>
4949 </pre>
4952 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
4953 <pre>
4955 </pre>
4958 EXAMPLE 5 The following three expressions have different meanings:
4959 <pre>
4960 "/tmp/fileXXXXXX"
4961 (char []){"/tmp/fileXXXXXX"}
4962 (const char []){"/tmp/fileXXXXXX"}
4963 </pre>
4964 The first always has static storage duration and has type array of char, but need not be modifiable; the last
4965 two have automatic storage duration when they occur within the body of a function, and the first of these
4966 two is modifiable.
4969 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
4970 and can even be shared. For example,
4971 <pre>
4973 </pre>
4974 might yield 1 if the literals' storage is shared.
4977 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
4978 linked object. For example, there is no way to write a self-referential compound literal that could be used
4979 as the function argument in place of the named object endless_zeros below:
4980 <pre>
4981 struct int_list { int car; struct int_list *cdr; };
4983 eval(endless_zeros);
4984 </pre>
4987 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
4988 <pre>
4989 struct s { int i; };
4990 int f (void)
4991 {
4992 struct s *p = 0, *q;
4993 int j = 0;
4994 again:
4995 q = p, p = &((struct s){ j++ });
4998 }
4999 </pre>
5000 The function f() always returns the value 1.
5002 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
5003 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
5004 have an indeterminate value, which would result in undefined behavior.
5006 <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>).
5007 <!--page 106 -->
5010 <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
5011 or void only, and the result of a cast expression is not an lvalue.
5012 </small>
5013 <p><small><a name="note100" href="#note100">100)</a> For example, subobjects without explicit initializers are initialized to zero.
5014 </small>
5015 <p><small><a name="note101" href="#note101">101)</a> This allows implementations to share storage for string literals and constant compound literals with
5016 the same or overlapping representations.
5017 </small>
5022 <pre>
5023 unary-expression:
5024 postfix-expression
5025 ++ unary-expression
5026 -- unary-expression
5027 unary-operator cast-expression
5028 sizeof unary-expression
5029 sizeof ( type-name )
5030 alignof ( type-name )
5031 unary-operator: one of
5032 & * + - ~ !
5033 </pre>
5035 <h5><a name="6.5.3.1" href="#6.5.3.1">6.5.3.1 Prefix increment and decrement operators</a></h5>
5038 The operand of the prefix increment or decrement operator shall have atomic, qualified,
5039 or unqualified real or pointer type, and shall be a modifiable lvalue.
5042 The value of the operand of the prefix ++ operator is incremented. The result is the new
5043 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
5044 See the discussions of additive operators and compound assignment for information on
5045 constraints, types, side effects, and conversions and the effects of operations on pointers.
5047 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
5048 operand is decremented.
5049 <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>).
5054 The operand of the unary & operator shall be either a function designator, the result of a
5055 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
5056 not declared with the register storage-class specifier.
5058 The operand of the unary * operator shall have pointer type.
5061 The unary & operator yields the address of its operand. If the operand has type ''type'',
5062 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
5063 neither that operator nor the & operator is evaluated and the result is as if both were
5064 omitted, except that the constraints on the operators still apply and the result is not an
5065 <!--page 107 -->
5066 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
5067 the unary * that is implied by the [] is evaluated and the result is as if the & operator
5068 were removed and the [] operator were changed to a + operator. Otherwise, the result is
5069 a pointer to the object or function designated by its operand.
5071 The unary * operator denotes indirection. If the operand points to a function, the result is
5072 a function designator; if it points to an object, the result is an lvalue designating the
5073 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
5074 invalid value has been assigned to the pointer, the behavior of the unary * operator is
5076 <p><b> Forward references</b>: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
5080 <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
5081 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
5082 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
5083 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
5084 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
5085 address inappropriately aligned for the type of object pointed to, and the address of an object after the
5086 end of its lifetime.
5087 </small>
5092 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
5093 integer type; of the ! operator, scalar type.
5096 The result of the unary + operator is the value of its (promoted) operand. The integer
5097 promotions are performed on the operand, and the result has the promoted type.
5099 The result of the unary - operator is the negative of its (promoted) operand. The integer
5100 promotions are performed on the operand, and the result has the promoted type.
5102 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
5103 each bit in the result is set if and only if the corresponding bit in the converted operand is
5104 not set). The integer promotions are performed on the operand, and the result has the
5105 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
5106 to the maximum value representable in that type minus E.
5108 The result of the logical negation operator ! is 0 if the value of its operand compares
5110 The expression !E is equivalent to (0==E).
5114 <!--page 108 -->
5119 The sizeof operator shall not be applied to an expression that has function type or an
5120 incomplete type, to the parenthesized name of such a type, or to an expression that
5121 designates a bit-field member. The alignof operator shall not be applied to a function
5122 type or an incomplete type.
5125 The sizeof operator yields the size (in bytes) of its operand, which may be an
5126 expression or the parenthesized name of a type. The size is determined from the type of
5127 the operand. The result is an integer. If the type of the operand is a variable length array
5128 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
5129 integer constant.
5131 The alignof operator yields the alignment requirement of its operand type. The result
5132 is an integer constant. When applied to an array type, the result is the alignment
5133 requirement of the element type.
5135 When sizeof is applied to an operand that has type char, unsigned char, or
5136 signed char, (or a qualified version thereof) the result is 1. When applied to an
5137 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
5138 applied to an operand that has structure or union type, the result is the total number of
5139 bytes in such an object, including internal and trailing padding.
5141 The value of the result of both operators is implementation-defined, and its type (an
5142 unsigned integer type) is size_t, defined in <a href="#7.19"><stddef.h></a> (and other headers).
5144 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
5145 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
5146 allocate and return a pointer to void. For example:
5147 <pre>
5148 extern void *alloc(size_t);
5149 double *dp = alloc(sizeof *dp);
5150 </pre>
5151 The implementation of the alloc function should ensure that its return value is aligned suitably for
5152 conversion to a pointer to double.
5155 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
5156 <pre>
5157 sizeof array / sizeof array[0]
5158 </pre>
5161 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
5162 function:
5163 <pre>
5165 </pre>
5169 <!--page 109 -->
5170 <pre>
5171 size_t fsize3(int n)
5172 {
5173 char b[n+3]; // variable length array
5174 return sizeof b; // execution time sizeof
5175 }
5176 int main()
5177 {
5178 size_t size;
5180 return 0;
5181 }
5182 </pre>
5184 <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>),
5185 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>).
5188 <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
5190 </small>
5195 <pre>
5196 cast-expression:
5197 unary-expression
5198 ( type-name ) cast-expression
5199 </pre>
5202 Unless the type name specifies a void type, the type name shall specify atomic, qualified,
5203 or unqualified scalar type, and the operand shall have scalar type.
5205 Conversions that involve pointers, other than where permitted by the constraints of
5208 A pointer type shall not be converted to any floating type. A floating type shall not be
5209 converted to any pointer type.
5212 Preceding an expression by a parenthesized type name converts the value of the
5213 expression to the named type. This construction is called a cast.<sup><a href="#note104"><b>104)</b></a></sup> A cast that specifies
5214 no conversion has no effect on the type or value of an expression.
5216 If the value of the expression is represented with greater precision or range than required
5217 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
5218 type of the expression is the same as the named type and removes any extra range and
5219 precision.
5220 <p><b> Forward references</b>: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
5221 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>).
5223 <!--page 110 -->
5226 <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
5227 unqualified version of the type.
5228 </small>
5233 <pre>
5234 multiplicative-expression:
5235 cast-expression
5236 multiplicative-expression * cast-expression
5237 multiplicative-expression / cast-expression
5238 multiplicative-expression % cast-expression
5239 </pre>
5242 Each of the operands shall have arithmetic type. The operands of the % operator shall
5243 have integer type.
5246 The usual arithmetic conversions are performed on the operands.
5248 The result of the binary * operator is the product of the operands.
5250 The result of the / operator is the quotient from the division of the first operand by the
5251 second; the result of the % operator is the remainder. In both operations, if the value of
5252 the second operand is zero, the behavior is undefined.
5254 When integers are divided, the result of the / operator is the algebraic quotient with any
5255 fractional part discarded.<sup><a href="#note105"><b>105)</b></a></sup> If the quotient a/b is representable, the expression
5256 (a/b)*b + a%b shall equal a; otherwise, the behavior of both a/b and a%b is
5257 undefined.
5260 <p><small><a name="note105" href="#note105">105)</a> This is often called ''truncation toward zero''.
5261 </small>
5266 <pre>
5267 additive-expression:
5268 multiplicative-expression
5269 additive-expression + multiplicative-expression
5270 additive-expression - multiplicative-expression
5271 </pre>
5274 For addition, either both operands shall have arithmetic type, or one operand shall be a
5275 pointer to a complete object type and the other shall have integer type. (Incrementing is
5276 equivalent to adding 1.)
5278 For subtraction, one of the following shall hold:
5283 <!--page 111 -->
5284 <ul>
5285 <li> both operands have arithmetic type;
5286 <li> both operands are pointers to qualified or unqualified versions of compatible complete
5287 object types; or
5288 <li> the left operand is a pointer to a complete object type and the right operand has
5289 integer type.
5290 </ul>
5291 (Decrementing is equivalent to subtracting 1.)
5294 If both operands have arithmetic type, the usual arithmetic conversions are performed on
5295 them.
5297 The result of the binary + operator is the sum of the operands.
5299 The result of the binary - operator is the difference resulting from the subtraction of the
5300 second operand from the first.
5302 For the purposes of these operators, a pointer to an object that is not an element of an
5303 array behaves the same as a pointer to the first element of an array of length one with the
5304 type of the object as its element type.
5306 When an expression that has integer type is added to or subtracted from a pointer, the
5307 result has the type of the pointer operand. If the pointer operand points to an element of
5308 an array object, and the array is large enough, the result points to an element offset from
5309 the original element such that the difference of the subscripts of the resulting and original
5310 array elements equals the integer expression. In other words, if the expression P points to
5311 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
5312 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
5313 the array object, provided they exist. Moreover, if the expression P points to the last
5314 element of an array object, the expression (P)+1 points one past the last element of the
5315 array object, and if the expression Q points one past the last element of an array object,
5316 the expression (Q)-1 points to the last element of the array object. If both the pointer
5317 operand and the result point to elements of the same array object, or one past the last
5318 element of the array object, the evaluation shall not produce an overflow; otherwise, the
5319 behavior is undefined. If the result points one past the last element of the array object, it
5320 shall not be used as the operand of a unary * operator that is evaluated.
5322 When two pointers are subtracted, both shall point to elements of the same array object,
5323 or one past the last element of the array object; the result is the difference of the
5324 subscripts of the two array elements. The size of the result is implementation-defined,
5325 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.19"><stddef.h></a> header.
5326 If the result is not representable in an object of that type, the behavior is undefined. In
5327 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
5328 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
5329 <!--page 112 -->
5330 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
5331 an array object or one past the last element of an array object, and the expression Q points
5332 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
5334 expression P points one past the last element of the array object, even though the
5335 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note106"><b>106)</b></a></sup>
5337 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
5338 <pre>
5339 {
5341 int a[n][m];
5345 n = p - a; // n == 1
5346 }
5347 </pre>
5349 If array a in the above example were declared to be an array of known constant size, and pointer p were
5350 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
5351 the same.
5353 <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>
5357 <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
5358 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
5359 by the size of the object originally pointed to, and the resulting pointer is converted back to the
5360 original type. For pointer subtraction, the result of the difference between the character pointers is
5361 similarly divided by the size of the object originally pointed to.
5362 When viewed in this way, an implementation need only provide one extra byte (which may overlap
5363 another object in the program) just after the end of the object in order to satisfy the ''one past the last
5364 element'' requirements.
5365 </small>
5370 <pre>
5371 shift-expression:
5372 additive-expression
5373 shift-expression << additive-expression
5374 shift-expression >> additive-expression
5375 </pre>
5378 Each of the operands shall have integer type.
5381 The integer promotions are performed on each of the operands. The type of the result is
5382 that of the promoted left operand. If the value of the right operand is negative or is
5384 <!--page 113 -->
5385 greater than or equal to the width of the promoted left operand, the behavior is undefined.
5387 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
5388 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
5389 one more than the maximum value representable in the result type. If E1 has a signed
5390 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
5391 the resulting value; otherwise, the behavior is undefined.
5393 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
5394 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
5395 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
5396 resulting value is implementation-defined.
5401 <pre>
5402 relational-expression:
5403 shift-expression
5404 relational-expression < shift-expression
5405 relational-expression > shift-expression
5406 relational-expression <= shift-expression
5407 relational-expression >= shift-expression
5408 </pre>
5411 One of the following shall hold:
5412 <ul>
5413 <li> both operands have real type; or *
5414 <li> both operands are pointers to qualified or unqualified versions of compatible object
5415 types.
5416 </ul>
5419 If both of the operands have arithmetic type, the usual arithmetic conversions are
5420 performed.
5422 For the purposes of these operators, a pointer to an object that is not an element of an
5423 array behaves the same as a pointer to the first element of an array of length one with the
5424 type of the object as its element type.
5426 When two pointers are compared, the result depends on the relative locations in the
5427 address space of the objects pointed to. If two pointers to object types both point to the
5428 same object, or both point one past the last element of the same array object, they
5429 compare equal. If the objects pointed to are members of the same aggregate object,
5430 pointers to structure members declared later compare greater than pointers to members
5431 declared earlier in the structure, and pointers to array elements with larger subscript
5432 values compare greater than pointers to elements of the same array with lower subscript
5433 <!--page 114 -->
5434 values. All pointers to members of the same union object compare equal. If the
5435 expression P points to an element of an array object and the expression Q points to the
5436 last element of the same array object, the pointer expression Q+1 compares greater than
5437 P. In all other cases, the behavior is undefined.
5439 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
5444 <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
5445 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
5446 </small>
5451 <pre>
5452 equality-expression:
5453 relational-expression
5454 equality-expression == relational-expression
5455 equality-expression != relational-expression
5456 </pre>
5459 One of the following shall hold:
5460 <ul>
5461 <li> both operands have arithmetic type;
5462 <li> both operands are pointers to qualified or unqualified versions of compatible types;
5463 <li> one operand is a pointer to an object type and the other is a pointer to a qualified or
5464 unqualified version of void; or
5465 <li> one operand is a pointer and the other is a null pointer constant.
5466 </ul>
5469 The == (equal to) and != (not equal to) operators are analogous to the relational
5470 operators except for their lower precedence.<sup><a href="#note108"><b>108)</b></a></sup> Each of the operators yields 1 if the
5471 specified relation is true and 0 if it is false. The result has type int. For any pair of
5472 operands, exactly one of the relations is true.
5474 If both of the operands have arithmetic type, the usual arithmetic conversions are
5475 performed. Values of complex types are equal if and only if both their real parts are equal
5476 and also their imaginary parts are equal. Any two values of arithmetic types from
5477 different type domains are equal if and only if the results of their conversions to the
5478 (complex) result type determined by the usual arithmetic conversions are equal.
5482 <!--page 115 -->
5484 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
5485 null pointer constant, the null pointer constant is converted to the type of the pointer. If
5486 one operand is a pointer to an object type and the other is a pointer to a qualified or
5487 unqualified version of void, the former is converted to the type of the latter.
5489 Two pointers compare equal if and only if both are null pointers, both are pointers to the
5490 same object (including a pointer to an object and a subobject at its beginning) or function,
5491 both are pointers to one past the last element of the same array object, or one is a pointer
5492 to one past the end of one array object and the other is a pointer to the start of a different
5493 array object that happens to immediately follow the first array object in the address
5496 For the purposes of these operators, a pointer to an object that is not an element of an
5497 array behaves the same as a pointer to the first element of an array of length one with the
5498 type of the object as its element type.
5501 <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.
5502 </small>
5503 <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
5504 adjacent members of a structure with no padding between them, or because the implementation chose
5505 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
5506 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
5507 behavior.
5508 </small>
5513 <pre>
5514 AND-expression:
5515 equality-expression
5516 AND-expression & equality-expression
5517 </pre>
5520 Each of the operands shall have integer type.
5523 The usual arithmetic conversions are performed on the operands.
5525 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
5526 the result is set if and only if each of the corresponding bits in the converted operands is
5527 set).
5532 <!--page 116 -->
5537 <pre>
5538 exclusive-OR-expression:
5539 AND-expression
5540 exclusive-OR-expression ^ AND-expression
5541 </pre>
5544 Each of the operands shall have integer type.
5547 The usual arithmetic conversions are performed on the operands.
5549 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
5550 in the result is set if and only if exactly one of the corresponding bits in the converted
5551 operands is set).
5556 <pre>
5557 inclusive-OR-expression:
5558 exclusive-OR-expression
5559 inclusive-OR-expression | exclusive-OR-expression
5560 </pre>
5563 Each of the operands shall have integer type.
5566 The usual arithmetic conversions are performed on the operands.
5568 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
5569 the result is set if and only if at least one of the corresponding bits in the converted
5570 operands is set).
5571 <!--page 117 -->
5576 <pre>
5577 logical-AND-expression:
5578 inclusive-OR-expression
5579 logical-AND-expression && inclusive-OR-expression
5580 </pre>
5583 Each of the operands shall have scalar type.
5586 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
5587 yields 0. The result has type int.
5589 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
5590 if the second operand is evaluated, there is a sequence point between the evaluations of
5591 the first and second operands. If the first operand compares equal to 0, the second
5592 operand is not evaluated.
5597 <pre>
5598 logical-OR-expression:
5599 logical-AND-expression
5600 logical-OR-expression || logical-AND-expression
5601 </pre>
5604 Each of the operands shall have scalar type.
5608 yields 0. The result has type int.
5610 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; if the
5611 second operand is evaluated, there is a sequence point between the evaluations of the first
5612 and second operands. If the first operand compares unequal to 0, the second operand is
5613 not evaluated.
5614 <!--page 118 -->
5619 <pre>
5620 conditional-expression:
5621 logical-OR-expression
5622 logical-OR-expression ? expression : conditional-expression
5623 </pre>
5626 The first operand shall have scalar type.
5628 One of the following shall hold for the second and third operands:
5629 <ul>
5630 <li> both operands have arithmetic type;
5631 <li> both operands have the same structure or union type;
5632 <li> both operands have void type;
5633 <li> both operands are pointers to qualified or unqualified versions of compatible types;
5634 <li> one operand is a pointer and the other is a null pointer constant; or
5635 <li> one operand is a pointer to an object type and the other is a pointer to a qualified or
5636 unqualified version of void.
5637 </ul>
5640 The first operand is evaluated; there is a sequence point between its evaluation and the
5641 evaluation of the second or third operand (whichever is evaluated). The second operand
5642 is evaluated only if the first compares unequal to 0; the third operand is evaluated only if
5643 the first compares equal to 0; the result is the value of the second or third operand
5644 (whichever is evaluated), converted to the type described below.<sup><a href="#note110"><b>110)</b></a></sup> *
5646 If both the second and third operands have arithmetic type, the result type that would be
5647 determined by the usual arithmetic conversions, were they applied to those two operands,
5648 is the type of the result. If both the operands have structure or union type, the result has
5649 that type. If both operands have void type, the result has void type.
5651 If both the second and third operands are pointers or one is a null pointer constant and the
5652 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
5653 of the types referenced by both operands. Furthermore, if both operands are pointers to
5654 compatible types or to differently qualified versions of compatible types, the result type is
5655 a pointer to an appropriately qualified version of the composite type; if one operand is a
5656 null pointer constant, the result has the type of the other operand; otherwise, one operand
5657 is a pointer to void or a qualified version of void, in which case the result type is a
5658 pointer to an appropriately qualified version of void.
5660 <!--page 119 -->
5662 EXAMPLE The common type that results when the second and third operands are pointers is determined
5663 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
5664 pointers have compatible types.
5666 Given the declarations
5667 <pre>
5668 const void *c_vp;
5669 void *vp;
5670 const int *c_ip;
5671 volatile int *v_ip;
5672 int *ip;
5673 const char *c_cp;
5674 </pre>
5675 the third column in the following table is the common type that is the result of a conditional expression in
5676 which the first two columns are the second and third operands (in either order):
5677 <pre>
5678 c_vp c_ip const void *
5679 v_ip 0 volatile int *
5680 c_ip v_ip const volatile int *
5681 vp c_cp const void *
5682 ip c_ip const int *
5683 vp ip void *
5684 </pre>
5688 <p><small><a name="note110" href="#note110">110)</a> A conditional expression does not yield an lvalue.
5689 </small>
5694 <pre>
5695 assignment-expression:
5696 conditional-expression
5697 unary-expression assignment-operator assignment-expression
5698 assignment-operator: one of
5700 </pre>
5703 An assignment operator shall have a modifiable lvalue as its left operand.
5706 An assignment operator stores a value in the object designated by the left operand. An
5707 assignment expression has the value of the left operand after the assignment,<sup><a href="#note111"><b>111)</b></a></sup> but is not
5708 an lvalue. The type of an assignment expression is the type the left operand would have
5709 after lvalue conversion. The side effect of updating the stored value of the left operand is
5710 sequenced after the value computations of the left and right operands. The evaluations of
5711 the operands are unsequenced.
5716 <!--page 120 -->
5719 <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
5720 when the object has volatile-qualified type.
5721 </small>
5727 <ul>
5728 <li> the left operand has atomic, qualified, or unqualified arithmetic type, and the right has
5729 arithmetic type;
5730 <li> the left operand has an atomic, qualified, or unqualified version of a structure or union
5731 type compatible with the type of the right;
5732 <li> the left operand has atomic, qualified, or unqualified pointer type, and (considering
5733 the type the left operand would have after lvalue conversion) both operands are
5734 pointers to qualified or unqualified versions of compatible types, and the type pointed
5735 to by the left has all the qualifiers of the type pointed to by the right;
5736 <li> the left operand has atomic, qualified, or unqualified pointer type, and (considering
5737 the type the left operand would have after lvalue conversion) one operand is a pointer
5738 to an object type, and the other is a pointer to a qualified or unqualified version of
5739 void, and the type pointed to by the left has all the qualifiers of the type pointed to
5740 by the right;
5741 <li> the left operand is an atomic, qualified, or unqualified pointer, and the right is a null
5742 pointer constant; or
5743 <li> the left operand has type atomic, qualified, or unqualified _Bool, and the right is a
5744 pointer.
5745 </ul>
5748 In simple assignment (=), the value of the right operand is converted to the type of the
5749 assignment expression and replaces the value stored in the object designated by the left
5750 operand.
5752 If the value being stored in an object is read from another object that overlaps in any way
5753 the storage of the first object, then the overlap shall be exact and the two objects shall
5754 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
5755 undefined.
5757 EXAMPLE 1 In the program fragment
5762 <!--page 121 -->
5763 <pre>
5764 int f(void);
5765 char c;
5766 /* ... */
5767 if ((c = f()) == -1)
5768 /* ... */
5769 </pre>
5770 the int value returned by the function may be truncated when stored in the char, and then converted back
5771 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
5772 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
5773 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
5774 variable c should be declared as int.
5777 EXAMPLE 2 In the fragment:
5778 <pre>
5779 char c;
5780 int i;
5781 long l;
5782 l = (c = i);
5783 </pre>
5784 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
5785 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
5786 that is, long int type.
5789 EXAMPLE 3 Consider the fragment:
5790 <pre>
5791 const char **cpp;
5792 char *p;
5793 const char c = 'A';
5794 cpp = &p; // constraint violation
5795 *cpp = &c; // valid
5796 *p = 0; // valid
5797 </pre>
5798 The first assignment is unsafe because it would allow the following valid code to attempt to change the
5799 value of the const object c.
5803 <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
5804 (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
5805 qualifiers that were applied to the type category of the expression (for example, it removes const but
5806 not volatile from the type int volatile * const).
5807 </small>
5812 For the operators += and -= only, either the left operand shall be an atomic, qualified, or
5813 unqualified pointer to a complete object type, and the right shall have integer type; or the
5814 left operand shall have atomic, qualified, or unqualified arithmetic type, and the right
5815 shall have arithmetic type.
5817 For the other operators, the left operand shall have atomic, qualified, or unqualified
5818 arithmetic type, and (considering the type the left operand would have after lvalue
5819 conversion) each operand shall have arithmetic type consistent with those allowed by the
5820 corresponding binary operator.
5823 A compound assignment of the form E1 op = E2 is equivalent to the simple assignment
5824 expression E1 = E1 op (E2), except that the lvalue E1 is evaluated only once, and with
5825 respect to an indeterminately-sequenced function call, the operation of a compound
5826 <!--page 122 -->
5827 assignment is a single evaluation. If E1 has an atomic type, compound assignment is a
5828 read-modify-write operation with memory_order_seq_cst memory order
5832 <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
5833 where T is the type of E1:
5835 <pre>
5836 T tmp = E1;
5837 T result;
5838 do {
5839 result = tmp op (E2);
5841 </pre>
5842 with result being the result of the operation.
5843 </small>
5848 <pre>
5849 expression:
5850 assignment-expression
5851 expression , assignment-expression
5852 </pre>
5855 The left operand of a comma operator is evaluated as a void expression; there is a
5856 sequence point between its evaluation and that of the right operand. Then the right
5857 operand is evaluated; the result has its type and value.<sup><a href="#note114"><b>114)</b></a></sup> *
5859 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
5860 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
5861 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
5862 expression of a conditional operator in such contexts. In the function call
5863 <pre>
5865 </pre>
5866 the function has three arguments, the second of which has the value 5.
5873 <!--page 123 -->
5876 <p><small><a name="note114" href="#note114">114)</a> A comma operator does not yield an lvalue.
5877 </small>
5882 <pre>
5883 constant-expression:
5884 conditional-expression
5885 </pre>
5888 A constant expression can be evaluated during translation rather than runtime, and
5889 accordingly may be used in any place that a constant may be.
5892 Constant expressions shall not contain assignment, increment, decrement, function-call,
5893 or comma operators, except when they are contained within a subexpression that is not
5896 Each constant expression shall evaluate to a constant that is in the range of representable
5897 values for its type.
5900 An expression that evaluates to a constant is required in several contexts. If a floating
5901 expression is evaluated in the translation environment, the arithmetic precision and range
5902 shall be at least as great as if the expression were being evaluated in the execution
5905 An integer constant expression<sup><a href="#note117"><b>117)</b></a></sup> shall have integer type and shall only have operands
5906 that are integer constants, enumeration constants, character constants, sizeof
5907 expressions whose results are integer constants, and floating constants that are the
5908 immediate operands of casts. Cast operators in an integer constant expression shall only
5909 convert arithmetic types to integer types, except as part of an operand to the sizeof
5910 operator.
5912 More latitude is permitted for constant expressions in initializers. Such a constant
5913 expression shall be, or evaluate to, one of the following:
5914 <ul>
5915 <li> an arithmetic constant expression,
5919 <!--page 124 -->
5920 <li> a null pointer constant,
5921 <li> an address constant, or
5922 <li> an address constant for a complete object type plus or minus an integer constant
5923 expression.
5924 </ul>
5926 An arithmetic constant expression shall have arithmetic type and shall only have
5927 operands that are integer constants, floating constants, enumeration constants, character
5928 constants, and sizeof expressions. Cast operators in an arithmetic constant expression
5929 shall only convert arithmetic types to arithmetic types, except as part of an operand to a
5930 sizeof operator whose result is an integer constant.
5932 An address constant is a null pointer, a pointer to an lvalue designating an object of static
5933 storage duration, or a pointer to a function designator; it shall be created explicitly using
5934 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
5935 an expression of array or function type. The array-subscript [] and member-access .
5936 and -> operators, the address & and indirection * unary operators, and pointer casts may
5937 be used in the creation of an address constant, but the value of an object shall not be
5938 accessed by use of these operators.
5940 An implementation may accept other forms of constant expressions.
5942 The semantic rules for the evaluation of a constant expression are the same as for
5944 <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>).
5949 <!--page 125 -->
5952 <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>).
5953 </small>
5954 <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
5955 the translation environment.
5956 </small>
5957 <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
5958 member of a structure, the value of an enumeration constant, and the size of a non-variable length
5959 array. Further constraints that apply to the integer constant expressions used in conditional-inclusion
5961 </small>
5964 <pre>
5966 </pre>
5967 the expression is a valid integer constant expression with value one.
5968 </small>
5973 <pre>
5974 declaration:
5976 static_assert-declaration
5977 declaration-specifiers:
5983 init-declarator-list:
5984 init-declarator
5985 init-declarator-list , init-declarator
5986 init-declarator:
5987 declarator
5988 declarator = initializer
5989 </pre>
5992 A declaration other than a static_assert declaration shall declare at least a declarator
5993 (other than the parameters of a function or the members of a structure or union), a tag, or
5994 the members of an enumeration.
5996 If an identifier has no linkage, there shall be no more than one declaration of the identifier
5997 (in a declarator or type specifier) with the same scope and in the same name space, except
5998 that a typedef name can be redefined to denote the same type as it currently does and tags
6001 All declarations in the same scope that refer to the same object or function shall specify
6002 compatible types.
6005 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
6006 of an identifier is a declaration for that identifier that:
6007 <ul>
6008 <li> for an object, causes storage to be reserved for that object;
6013 <!--page 126 -->
6014 <li> for an enumeration constant or typedef name, is the (only) declaration of the
6015 identifier.
6016 </ul>
6018 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
6019 storage duration, and part of the type of the entities that the declarators denote. The init-
6020 declarator-list is a comma-separated sequence of declarators, each of which may have
6021 additional type information, or an initializer, or both. The declarators contain the
6022 identifiers (if any) being declared.
6024 If an identifier for an object is declared with no linkage, the type for the object shall be
6025 complete by the end of its declarator, or by the end of its init-declarator if it has an
6026 initializer; in the case of function parameters (including in prototypes), it is the adjusted
6028 <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
6029 (<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>).
6032 <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>.
6033 </small>
6038 <pre>
6039 storage-class-specifier:
6040 typedef
6041 extern
6042 static
6043 _Thread_local
6044 auto
6045 register
6046 </pre>
6049 At most, one storage-class specifier may be given in the declaration specifiers in a
6050 declaration, except that _Thread_local may appear with static or extern.<sup><a href="#note120"><b>120)</b></a></sup>
6052 In the declaration of an object with block scope, if the declaration specifiers include
6053 _Thread_local, they shall also include either static or extern. If
6054 _Thread_local appears in any declaration of an object, it shall be present in every
6055 declaration of that object.
6058 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
6059 only; it is discussed in <a href="#6.7.8">6.7.8</a>. The meanings of the various linkages and storage durations
6064 <!--page 127 -->
6066 A declaration of an identifier for an object with storage-class specifier register
6067 suggests that access to the object be as fast as possible. The extent to which such
6068 suggestions are effective is implementation-defined.<sup><a href="#note121"><b>121)</b></a></sup>
6070 The declaration of an identifier for a function that has block scope shall have no explicit
6071 storage-class specifier other than extern.
6073 If an aggregate or union object is declared with a storage-class specifier other than
6074 typedef, the properties resulting from the storage-class specifier, except with respect to
6075 linkage, also apply to the members of the object, and so on recursively for any aggregate
6076 or union member objects.
6080 <p><small><a name="note120" href="#note120">120)</a> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
6081 </small>
6082 <p><small><a name="note121" href="#note121">121)</a> The implementation may treat any register declaration simply as an auto declaration. However,
6083 whether or not addressable storage is actually used, the address of any part of an object declared with
6084 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
6085 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
6086 <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
6087 register is sizeof.
6088 </small>
6093 <pre>
6094 type-specifier:
6095 void
6096 char
6097 short
6098 int
6099 long
6100 float
6101 double
6102 signed
6103 unsigned
6104 _Bool
6105 _Complex
6106 atomic-type-specifier
6107 struct-or-union-specifier
6108 enum-specifier
6109 typedef-name
6110 </pre>
6113 At least one type specifier shall be given in the declaration specifiers in each declaration,
6114 and in the specifier-qualifier list in each struct declaration and type name. Each list of
6117 <!--page 128 -->
6118 type specifiers shall be one of the following multisets (delimited by commas, when there
6119 is more than one multiset per item); the type specifiers may occur in any order, possibly
6120 intermixed with the other declaration specifiers.
6121 <ul>
6122 <li> void
6123 <li> char
6124 <li> signed char
6125 <li> unsigned char
6126 <li> short, signed short, short int, or signed short int
6127 <li> unsigned short, or unsigned short int
6128 <li> int, signed, or signed int
6129 <li> unsigned, or unsigned int
6130 <li> long, signed long, long int, or signed long int
6131 <li> unsigned long, or unsigned long int
6132 <li> long long, signed long long, long long int, or
6133 signed long long int
6134 <li> unsigned long long, or unsigned long long int
6135 <li> float
6136 <li> double
6137 <li> long double
6138 <li> _Bool
6139 <li> float _Complex
6140 <li> double _Complex
6141 <li> long double _Complex
6142 <li> atomic type specifier
6143 <li> struct or union specifier
6144 <li> enum specifier
6145 <li> typedef name
6146 </ul>
6148 The type specifier _Complex shall not be used if the implementation does not support
6150 <!--page 129 -->
6153 Specifiers for structures, unions, enumerations, and atomic types are discussed in <a href="#6.7.2.1">6.7.2.1</a>
6154 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
6157 Each of the comma-separated multisets designates the same type, except that for bit-
6158 fields, it is implementation-defined whether the specifier int designates the same type as
6159 signed int or the same type as unsigned int.
6160 <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>),
6161 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>).
6166 <pre>
6167 struct-or-union-specifier:
6169 struct-or-union identifier
6170 struct-or-union:
6171 struct
6172 union
6173 struct-declaration-list:
6174 struct-declaration
6175 struct-declaration-list struct-declaration
6176 struct-declaration:
6178 static_assert-declaration
6179 specifier-qualifier-list:
6182 struct-declarator-list:
6183 struct-declarator
6184 struct-declarator-list , struct-declarator
6185 struct-declarator:
6186 declarator
6188 </pre>
6191 A struct-declaration that does not declare an anonymous structure or anonymous union
6192 shall contain a struct-declarator-list.
6193 <!--page 130 -->
6195 A structure or union shall not contain a member with incomplete or function type (hence,
6196 a structure shall not contain an instance of itself, but may contain a pointer to an instance
6197 of itself), except that the last member of a structure with more than one named member
6198 may have incomplete array type; such a structure (and any union containing, possibly
6199 recursively, a member that is such a structure) shall not be a member of a structure or an
6200 element of an array.
6202 The expression that specifies the width of a bit-field shall be an integer constant
6203 expression with a nonnegative value that does not exceed the width of an object of the
6204 type that would be specified were the colon and expression omitted.<sup><a href="#note122"><b>122)</b></a></sup> If the value is
6205 zero, the declaration shall have no declarator.
6207 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
6208 int, unsigned int, or some other implementation-defined type. It is
6209 implementation-defined whether atomic types are permitted.
6212 As discussed in <a href="#6.2.5">6.2.5</a>, a structure is a type consisting of a sequence of members, whose
6213 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
6214 of members whose storage overlap.
6216 Structure and union specifiers have the same form. The keywords struct and union
6217 indicate that the type being specified is, respectively, a structure type or a union type.
6219 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
6220 within a translation unit. The struct-declaration-list is a sequence of declarations for the
6221 members of the structure or union. If the struct-declaration-list contains no named
6222 members, no anonymous structures, and no anonymous unions, the behavior is undefined.
6223 The type is incomplete until immediately after the } that terminates the list, and complete
6224 thereafter.
6226 A member of a structure or union may have any complete object type other than a
6227 variably modified type.<sup><a href="#note123"><b>123)</b></a></sup> In addition, a member may be declared to consist of a
6228 specified number of bits (including a sign bit, if any). Such a member is called a
6231 A bit-field is interpreted as having a signed or unsigned integer type consisting of the
6232 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
6234 <!--page 131 -->
6235 type _Bool, the value of the bit-field shall compare equal to the value stored; a _Bool
6236 bit-field has the semantics of a _Bool.
6238 An implementation may allocate any addressable storage unit large enough to hold a bit-
6239 field. If enough space remains, a bit-field that immediately follows another bit-field in a
6240 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
6241 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
6242 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
6243 low-order or low-order to high-order) is implementation-defined. The alignment of the
6244 addressable storage unit is unspecified.
6246 A bit-field declaration with no declarator, but only a colon and a width, indicates an
6247 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
6248 indicates that no further bit-field is to be packed into the unit in which the previous bit-
6249 field, if any, was placed.
6251 An unnamed member of structure type with no tag is called an anonymous structure; an
6252 unnamed member of union type with no tag is called an anonymous union. The members
6253 of an anonymous structure or union are considered to be members of the containing
6254 structure or union. This applies recursively if the containing structure or union is also
6255 anonymous.
6257 Each non-bit-field member of a structure or union object is aligned in an implementation-
6258 defined manner appropriate to its type.
6260 Within a structure object, the non-bit-field members and the units in which bit-fields
6261 reside have addresses that increase in the order in which they are declared. A pointer to a
6262 structure object, suitably converted, points to its initial member (or if that member is a
6263 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
6264 padding within a structure object, but not at its beginning.
6266 The size of a union is sufficient to contain the largest of its members. The value of at
6267 most one of the members can be stored in a union object at any time. A pointer to a
6268 union object, suitably converted, points to each of its members (or if a member is a bit-
6269 field, then to the unit in which it resides), and vice versa.
6271 There may be unnamed padding at the end of a structure or union.
6273 As a special case, the last element of a structure with more than one named member may
6274 have an incomplete array type; this is called a flexible array member. In most situations,
6277 <!--page 132 -->
6278 the flexible array member is ignored. In particular, the size of the structure is as if the
6279 flexible array member were omitted except that it may have more trailing padding than
6280 the omission would imply. However, when a . (or ->) operator has a left operand that is
6281 (a pointer to) a structure with a flexible array member and the right operand names that
6282 member, it behaves as if that member were replaced with the longest array (with the same
6283 element type) that would not make the structure larger than the object being accessed; the
6284 offset of the array shall remain that of the flexible array member, even if this would differ
6285 from that of the replacement array. If this array would have no elements, it behaves as if
6286 it had one element but the behavior is undefined if any attempt is made to access that
6287 element or to generate a pointer one past it.
6289 EXAMPLE 1 The following illustrates anonymous structures and unions:
6290 <pre>
6291 struct v {
6292 union { // anonymous union
6293 struct { int i, j; }; // anonymous structure
6294 struct { long k, l; } w;
6295 };
6296 int m;
6297 } v1;
6298 v1.i = 2; // valid
6299 v1.k = 3; // invalid: inner structure is not anonymous
6300 v1.w.k = 5; // valid
6301 </pre>
6304 EXAMPLE 2 After the declaration:
6305 <pre>
6306 struct s { int n; double d[]; };
6307 </pre>
6308 the structure struct s has a flexible array member d. A typical way to use this is:
6309 <pre>
6310 int m = /* some value */;
6311 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
6312 </pre>
6313 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
6314 p had been declared as:
6315 <pre>
6316 struct { int n; double d[m]; } *p;
6317 </pre>
6318 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
6319 not be the same).
6321 Following the above declaration:
6322 <pre>
6323 struct s t1 = { 0 }; // valid
6325 t1.n = 4; // valid
6327 </pre>
6328 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
6329 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
6330 <pre>
6331 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)
6332 </pre>
6333 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
6334 code.
6335 <!--page 133 -->
6337 After the further declaration:
6338 <pre>
6339 struct ss { int n; };
6340 </pre>
6341 the expressions:
6342 <pre>
6343 sizeof (struct s) >= sizeof (struct ss)
6344 sizeof (struct s) >= offsetof(struct s, d)
6345 </pre>
6346 are always equal to 1.
6348 If sizeof (double) is 8, then after the following code is executed:
6349 <pre>
6350 struct s *s1;
6351 struct s *s2;
6352 s1 = malloc(sizeof (struct s) + 64);
6353 s2 = malloc(sizeof (struct s) + 46);
6354 </pre>
6355 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
6356 purposes, as if the identifiers had been declared as:
6357 <pre>
6358 struct { int n; double d[8]; } *s1;
6359 struct { int n; double d[5]; } *s2;
6360 </pre>
6362 Following the further successful assignments:
6363 <pre>
6364 s1 = malloc(sizeof (struct s) + 10);
6365 s2 = malloc(sizeof (struct s) + 6);
6366 </pre>
6367 they then behave as if the declarations were:
6368 <pre>
6369 struct { int n; double d[1]; } *s1, *s2;
6370 </pre>
6371 and:
6372 <pre>
6373 double *dp;
6375 *dp = 42; // valid
6377 *dp = 42; // undefined behavior
6378 </pre>
6380 The assignment:
6381 <pre>
6382 *s1 = *s2;
6383 </pre>
6384 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
6385 of the structure, they might be copied or simply overwritten with indeterminate values.
6387 <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>).
6388 <!--page 134 -->
6391 <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
6392 value bits) of a _Bool may be just 1 bit.
6393 </small>
6394 <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
6396 </small>
6397 <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
6398 or arrays of bit-field objects.
6399 </small>
6400 <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,
6401 then it is implementation-defined whether the bit-field is signed or unsigned.
6402 </small>
6403 <p><small><a name="note126" href="#note126">126)</a> An unnamed bit-field structure member is useful for padding to conform to externally imposed
6404 layouts.
6405 </small>
6410 <pre>
6411 enum-specifier:
6414 enum identifier
6415 enumerator-list:
6416 enumerator
6417 enumerator-list , enumerator
6418 enumerator:
6419 enumeration-constant
6420 enumeration-constant = constant-expression
6421 </pre>
6424 The expression that defines the value of an enumeration constant shall be an integer
6425 constant expression that has a value representable as an int.
6428 The identifiers in an enumerator list are declared as constants that have type int and
6429 may appear wherever such are permitted.<sup><a href="#note127"><b>127)</b></a></sup> An enumerator with = defines its
6430 enumeration constant as the value of the constant expression. If the first enumerator has
6431 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
6432 defines its enumeration constant as the value of the constant expression obtained by
6433 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
6434 = may produce enumeration constants with values that duplicate other values in the same
6435 enumeration.) The enumerators of an enumeration are also known as its members.
6437 Each enumerated type shall be compatible with char, a signed integer type, or an
6438 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note128"><b>128)</b></a></sup> but shall be
6439 capable of representing the values of all the members of the enumeration. The
6440 enumerated type is incomplete until immediately after the } that terminates the list of
6441 enumerator declarations, and complete thereafter.
6446 <!--page 135 -->
6448 EXAMPLE The following fragment:
6449 <pre>
6450 enum hue { chartreuse, burgundy, claret=20, winedark };
6451 enum hue col, *cp;
6452 col = claret;
6453 cp = &col;
6454 if (*cp != burgundy)
6455 /* ... */
6456 </pre>
6457 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
6458 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
6463 <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
6464 each other and from other identifiers declared in ordinary declarators.
6465 </small>
6466 <p><small><a name="note128" href="#note128">128)</a> An implementation may delay the choice of which integer type until all enumeration constants have
6467 been seen.
6468 </small>
6473 A specific type shall have its content defined at most once.
6475 Where two declarations that use the same tag declare the same type, they shall both use
6476 the same choice of struct, union, or enum.
6478 A type specifier of the form
6479 <pre>
6480 enum identifier
6481 </pre>
6482 without an enumerator list shall only appear after the type it specifies is complete.
6485 All declarations of structure, union, or enumerated types that have the same scope and
6486 use the same tag declare the same type. Irrespective of whether there is a tag or what
6487 other declarations of the type are in the same translation unit, the type is incomplete<sup><a href="#note129"><b>129)</b></a></sup>
6488 until immediately after the closing brace of the list defining the content, and complete
6489 thereafter.
6491 Two declarations of structure, union, or enumerated types which are in different scopes or
6492 use different tags declare distinct types. Each declaration of a structure, union, or
6493 enumerated type which does not include a tag declares a distinct type.
6495 A type specifier of the form
6500 <!--page 136 -->
6501 <pre>
6503 </pre>
6504 or
6505 <pre>
6507 </pre>
6508 or
6509 <pre>
6511 </pre>
6512 declares a structure, union, or enumerated type. The list defines the structure content,
6513 union content, or enumeration content. If an identifier is provided,<sup><a href="#note130"><b>130)</b></a></sup> the type specifier
6514 also declares the identifier to be the tag of that type.
6516 A declaration of the form
6517 <pre>
6518 struct-or-union identifier ;
6519 </pre>
6520 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>
6522 If a type specifier of the form
6523 <pre>
6524 struct-or-union identifier
6525 </pre>
6526 occurs other than as part of one of the above forms, and no other declaration of the
6527 identifier as a tag is visible, then it declares an incomplete structure or union type, and
6530 If a type specifier of the form
6531 <pre>
6532 struct-or-union identifier
6533 </pre>
6534 or
6535 <pre>
6536 enum identifier
6537 </pre>
6538 occurs other than as part of one of the above forms, and a declaration of the identifier as a
6539 tag is visible, then it specifies the same type as that other declaration, and does not
6540 redeclare the tag.
6542 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
6543 <pre>
6544 struct tnode {
6545 int count;
6546 struct tnode *left, *right;
6547 };
6548 </pre>
6549 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
6550 declaration has been given, the declaration
6555 <!--page 137 -->
6556 <pre>
6557 struct tnode s, *sp;
6558 </pre>
6559 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
6560 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
6561 which sp points; the expression s.right->count designates the count member of the right struct
6562 tnode pointed to from s.
6564 The following alternative formulation uses the typedef mechanism:
6565 <pre>
6566 typedef struct tnode TNODE;
6567 struct tnode {
6568 int count;
6569 TNODE *left, *right;
6570 };
6571 TNODE s, *sp;
6572 </pre>
6575 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
6576 structures, the declarations
6577 <pre>
6578 struct s1 { struct s2 *s2p; /* ... */ }; // D1
6579 struct s2 { struct s1 *s1p; /* ... */ }; // D2
6580 </pre>
6581 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
6582 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
6583 D2. To eliminate this context sensitivity, the declaration
6584 <pre>
6585 struct s2;
6586 </pre>
6587 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
6588 completes the specification of the new type.
6590 <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>).
6593 <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
6594 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
6595 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
6596 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
6597 </small>
6598 <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
6599 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
6600 can make use of that typedef name to declare objects having the specified structure, union, or
6601 enumerated type.
6602 </small>
6603 <p><small><a name="note131" href="#note131">131)</a> A similar construction with enum does not exist.
6604 </small>
6609 <pre>
6610 atomic-type-specifier:
6611 _Atomic ( type-name )
6612 </pre>
6615 Atomic type specifiers shall not be used if the implementation does not support atomic
6618 The type name in an atomic type specifier shall not refer to an array type, a function type,
6619 an atomic type, or a qualified type.
6622 The properties associated with atomic types are meaningful only for expressions that are
6623 lvalues. If the _Atomic keyword is immediately followed by a left parenthesis, it is
6624 interpreted as a type specifier (with a type name), not as a type qualifier.
6625 <!--page 138 -->
6630 <pre>
6631 type-qualifier:
6632 const
6633 restrict
6634 volatile
6635 _Atomic
6636 </pre>
6639 Types other than pointer types whose referenced type is an object type shall not be
6640 restrict-qualified.
6642 The type modified by the _Atomic qualifier shall not be an array type or a function
6643 type.
6646 The properties associated with qualified types are meaningful only for expressions that
6649 If the same qualifier appears more than once in the same specifier-qualifier-list, either
6650 directly or via one or more typedefs, the behavior is the same as if it appeared only
6651 once. If other qualifiers appear along with the _Atomic qualifier in a specifier-qualifier-
6652 list, the resulting type is the so-qualified atomic type.
6654 If an attempt is made to modify an object defined with a const-qualified type through use
6655 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
6656 made to refer to an object defined with a volatile-qualified type through use of an lvalue
6657 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note133"><b>133)</b></a></sup>
6659 An object that has volatile-qualified type may be modified in ways unknown to the
6660 implementation or have other unknown side effects. Therefore any expression referring
6661 to such an object shall be evaluated strictly according to the rules of the abstract machine,
6662 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
6663 object shall agree with that prescribed by the abstract machine, except as modified by the
6668 <!--page 139 -->
6669 unknown factors mentioned previously.<sup><a href="#note134"><b>134)</b></a></sup> What constitutes an access to an object that
6670 has volatile-qualified type is implementation-defined.
6672 An object that is accessed through a restrict-qualified pointer has a special association
6673 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
6674 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note135"><b>135)</b></a></sup> The intended
6675 use of the restrict qualifier (like the register storage class) is to promote
6676 optimization, and deleting all instances of the qualifier from all preprocessing translation
6677 units composing a conforming program does not change its meaning (i.e., observable
6678 behavior).
6680 If the specification of an array type includes any type qualifiers, the element type is so-
6681 qualified, not the array type. If the specification of a function type includes any type
6684 For two qualified types to be compatible, both shall have the identically qualified version
6685 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
6686 does not affect the specified type.
6688 EXAMPLE 1 An object declared
6689 <pre>
6690 extern const volatile int real_time_clock;
6691 </pre>
6692 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
6695 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
6696 modify an aggregate type:
6697 <pre>
6698 const struct s { int mem; } cs = { 1 };
6699 struct s ncs; // the object ncs is modifiable
6702 int *pi;
6703 const int *pci;
6704 ncs = cs; // valid
6705 cs = ncs; // violates modifiable lvalue constraint for =
6706 pi = &ncs.mem; // valid
6707 pi = &cs.mem; // violates type constraints for =
6708 pci = &cs.mem; // valid
6710 </pre>
6714 <!--page 140 -->
6716 EXAMPLE 3 The declaration
6717 <pre>
6718 _Atomic volatile int *p;
6719 </pre>
6720 specifies that p has the type ''pointer to volatile atomic int'', a pointer to a volatile-qualified atomic type.
6724 <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
6725 storage. Moreover, the implementation need not allocate storage for such an object if its address is
6726 never used.
6727 </small>
6728 <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
6729 never actually defined as objects in the program (such as an object at a memory-mapped input/output
6730 address).
6731 </small>
6732 <p><small><a name="note134" href="#note134">134)</a> A volatile declaration may be used to describe an object corresponding to a memory-mapped
6733 input/output port or an object accessed by an asynchronously interrupting function. Actions on
6734 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
6735 permitted by the rules for evaluating expressions.
6736 </small>
6737 <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
6738 association between the allocated object and the pointer.
6739 </small>
6740 <p><small><a name="note136" href="#note136">136)</a> Both of these can occur through the use of typedefs.
6741 </small>
6745 Let D be a declaration of an ordinary identifier that provides a means of designating an
6746 object P as a restrict-qualified pointer to type T.
6748 If D appears inside a block and does not have storage class extern, let B denote the
6749 block. If D appears in the list of parameter declarations of a function definition, let B
6750 denote the associated block. Otherwise, let B denote the block of main (or the block of
6751 whatever function is called at program startup in a freestanding environment).
6753 In what follows, a pointer expression E is said to be based on object P if (at some
6754 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
6755 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>
6756 Note that ''based'' is defined only for expressions with pointer types.
6758 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
6759 access the value of the object X that it designates, and X is also modified (by any means),
6760 then the following requirements apply: T shall not be const-qualified. Every other lvalue
6761 used to access the value of X shall also have its address based on P. Every access that
6762 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
6763 is assigned the value of a pointer expression E that is based on another restricted pointer
6764 object P2, associated with block B2, then either the execution of B2 shall begin before
6765 the execution of B, or the execution of B2 shall end prior to the assignment. If these
6766 requirements are not met, then the behavior is undefined.
6768 Here an execution of B means that portion of the execution of the program that would
6769 correspond to the lifetime of an object with scalar type and automatic storage duration
6770 associated with B.
6772 A translator is free to ignore any or all aliasing implications of uses of restrict.
6774 EXAMPLE 1 The file scope declarations
6775 <pre>
6776 int * restrict a;
6777 int * restrict b;
6778 extern int c[];
6779 </pre>
6780 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
6781 program, then it is never accessed using either of the other two.
6784 <!--page 141 -->
6786 EXAMPLE 2 The function parameter declarations in the following example
6787 <pre>
6788 void f(int n, int * restrict p, int * restrict q)
6789 {
6791 *p++ = *q++;
6792 }
6793 </pre>
6794 assert that, during each execution of the function, if an object is accessed through one of the pointer
6795 parameters, then it is not also accessed through the other.
6797 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
6798 analysis of function f without examining any of the calls of f in the program. The cost is that the
6799 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
6800 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
6801 both p and q.
6802 <pre>
6803 void g(void)
6804 {
6805 extern int d[100];
6808 }
6809 </pre>
6812 EXAMPLE 3 The function parameter declarations
6813 <pre>
6814 void h(int n, int * restrict p, int * restrict q, int * restrict r)
6815 {
6816 int i;
6818 p[i] = q[i] + r[i];
6819 }
6820 </pre>
6821 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
6822 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
6823 modified within function h.
6826 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
6827 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
6828 between restricted pointers declared in nested blocks have defined behavior.
6829 <!--page 142 -->
6830 <pre>
6831 {
6832 int * restrict p1;
6833 int * restrict q1;
6834 p1 = q1; // undefined behavior
6835 {
6836 int * restrict p2 = p1; // valid
6837 int * restrict q2 = q1; // valid
6838 p1 = q2; // undefined behavior
6839 p2 = q2; // undefined behavior
6840 }
6841 }
6842 </pre>
6844 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
6845 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
6846 example, this permits new_vector to return a vector.
6847 <pre>
6848 typedef struct { int n; float * restrict v; } vector;
6849 vector new_vector(int n)
6850 {
6851 vector t;
6852 t.n = n;
6853 t.v = malloc(n * sizeof (float));
6854 return t;
6855 }
6856 </pre>
6860 <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
6861 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
6862 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
6863 expressions *p and p[1] are not.
6864 </small>
6869 <pre>
6870 function-specifier:
6871 inline
6872 _Noreturn
6873 </pre>
6876 Function specifiers shall be used only in the declaration of an identifier for a function.
6878 An inline definition of a function with external linkage shall not contain a definition of a
6879 modifiable object with static or thread storage duration, and shall not contain a reference
6880 to an identifier with internal linkage.
6882 In a hosted environment, no function specifier(s) shall appear in a declaration of main.
6885 A function specifier may appear more than once; the behavior is the same as if it
6886 appeared only once.
6888 A function declared with an inline function specifier is an inline function. Making a *
6889 function an inline function suggests that calls to the function be as fast as possible.<sup><a href="#note138"><b>138)</b></a></sup>
6890 The extent to which such suggestions are effective is implementation-defined.<sup><a href="#note139"><b>139)</b></a></sup>
6895 <!--page 143 -->
6897 Any function with internal linkage can be an inline function. For a function with external
6898 linkage, the following restrictions apply: If a function is declared with an inline
6899 function specifier, then it shall also be defined in the same translation unit. If all of the
6900 file scope declarations for a function in a translation unit include the inline function
6901 specifier without extern, then the definition in that translation unit is an inline
6902 definition. An inline definition does not provide an external definition for the function,
6903 and does not forbid an external definition in another translation unit. An inline definition
6904 provides an alternative to an external definition, which a translator may use to implement
6905 any call to the function in the same translation unit. It is unspecified whether a call to the
6906 function uses the inline definition or the external definition.<sup><a href="#note140"><b>140)</b></a></sup>
6908 A function declared with a _Noreturn function specifier shall not return to its caller.
6911 The implementation should produce a diagnostic message for a function declared with a
6912 _Noreturn function specifier that appears to be capable of returning to its caller.
6914 EXAMPLE 1 The declaration of an inline function with external linkage can result in either an external
6915 definition, or a definition available for use only within the translation unit. A file scope declaration with
6916 extern creates an external definition. The following example shows an entire translation unit.
6917 <pre>
6918 inline double fahr(double t)
6919 {
6921 }
6922 inline double cels(double t)
6923 {
6925 }
6926 extern double fahr(double); // creates an external definition
6927 double convert(int is_fahr, double temp)
6928 {
6929 /* A translator may perform inline substitutions */
6930 return is_fahr ? cels(temp) : fahr(temp);
6931 }
6932 </pre>
6934 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
6935 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
6936 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
6937 definition are distinct and either may be used for the call.
6940 EXAMPLE 2
6945 <!--page 144 -->
6946 <pre>
6947 _Noreturn void f () {
6948 abort(); // ok
6949 }
6952 }
6953 </pre>
6958 <p><small><a name="note138" href="#note138">138)</a> By using, for example, an alternative to the usual function call mechanism, such as ''inline
6959 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
6960 Therefore, for example, the expansion of a macro used within the body of the function uses the
6961 definition it had at the point the function body appears, and not where the function is called; and
6962 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
6963 single address, regardless of the number of inline definitions that occur in addition to the external
6964 definition.
6965 </small>
6966 <p><small><a name="note139" href="#note139">139)</a> For example, an implementation might never perform inline substitution, or might only perform inline
6967 substitutions to calls in the scope of an inline declaration.
6968 </small>
6969 <p><small><a name="note140" href="#note140">140)</a> Since an inline definition is distinct from the corresponding external definition and from any other
6970 corresponding inline definitions in other translation units, all corresponding objects with static storage
6971 duration are also distinct in each of the definitions.
6972 </small>
6977 <pre>
6978 alignment-specifier:
6979 _Alignas ( type-name )
6980 _Alignas ( constant-expression )
6981 </pre>
6984 An alignment attribute shall not be specified in a declaration of a typedef, or a bit-field, or
6985 a function, or a parameter, or an object declared with the register storage-class
6986 specifier.
6988 The constant expression shall be an integer constant expression. It shall evaluate to a
6989 valid fundamental alignment, or to a valid extended alignment supported by the
6990 implementation in the context in which it appears, or to zero.
6992 The combined effect of all alignment attributes in a declaration shall not specify an
6993 alignment that is less strict than the alignment that would otherwise be required for the
6994 type of the object or member being declared.
6997 The first form is equivalent to _Alignas(alignof(type-name)).
6999 The alignment requirement of the declared object or member is taken to be the specified
7000 alignment. An alignment specification of zero has no effect.<sup><a href="#note141"><b>141)</b></a></sup> When multiple
7001 alignment specifiers occur in a declaration, the effective alignment requirement is the
7002 strictest specified alignment.
7004 If the definition of an object has an alignment specifier, any other declaration of that
7005 object shall either specify equivalent alignment or have no alignment specifier. If the
7006 definition of an object does not have an alignment specifier, any other declaration of that
7007 object shall also have no alignment specifier. If declarations of an object in different
7008 translation units have different alignment specifiers, the behavior is undefined.
7012 <!--page 145 -->
7015 <p><small><a name="note141" href="#note141">141)</a> An alignment specification of zero also does not affect other alignment specifications in the same
7016 declaration.
7017 </small>
7022 <pre>
7023 declarator:
7025 direct-declarator:
7026 identifier
7027 ( declarator )
7030 direct-declarator [ type-qualifier-list static assignment-expression ]
7032 direct-declarator ( parameter-type-list )
7034 pointer:
7037 type-qualifier-list:
7038 type-qualifier
7039 type-qualifier-list type-qualifier
7040 parameter-type-list:
7041 parameter-list
7042 parameter-list , ...
7043 parameter-list:
7044 parameter-declaration
7045 parameter-list , parameter-declaration
7046 parameter-declaration:
7047 declaration-specifiers declarator
7049 identifier-list:
7050 identifier
7051 identifier-list , identifier
7052 </pre>
7055 Each declarator declares one identifier, and asserts that when an operand of the same
7056 form as the declarator appears in an expression, it designates a function or object with the
7057 scope, storage duration, and type indicated by the declaration specifiers.
7059 A full declarator is a declarator that is not part of another declarator. The end of a full
7060 declarator is a sequence point. If, in the nested sequence of declarators in a full
7061 <!--page 146 -->
7062 declarator, there is a declarator specifying a variable length array type, the type specified
7063 by the full declarator is said to be variably modified. Furthermore, any type derived by
7064 declarator type derivation from a variably modified type is itself variably modified.
7066 In the following subclauses, consider a declaration
7067 <pre>
7068 T D1
7069 </pre>
7070 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
7071 a declarator that contains an identifier ident. The type specified for the identifier ident in
7072 the various forms of declarator is described inductively using this notation.
7074 If, in the declaration ''T D1'', D1 has the form
7075 <pre>
7076 identifier
7077 </pre>
7078 then the type specified for ident is T .
7080 If, in the declaration ''T D1'', D1 has the form
7081 <pre>
7082 ( D )
7083 </pre>
7084 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
7085 parentheses is identical to the unparenthesized declarator, but the binding of complicated
7086 declarators may be altered by parentheses.
7089 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of pointer, array, and
7090 function declarators that modify an arithmetic, structure, union, or void type, either
7091 directly or via one or more typedefs.
7092 <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>).
7097 If, in the declaration ''T D1'', D1 has the form
7098 <pre>
7100 </pre>
7101 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7102 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
7103 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
7105 For two pointer types to be compatible, both shall be identically qualified and both shall
7106 be pointers to compatible types.
7108 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
7109 to a constant value'' and a ''constant pointer to a variable value''.
7110 <!--page 147 -->
7111 <pre>
7112 const int *ptr_to_constant;
7113 int *const constant_ptr;
7114 </pre>
7115 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
7116 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
7117 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
7118 same location.
7120 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
7121 type ''pointer to int''.
7122 <pre>
7123 typedef int *int_ptr;
7124 const int_ptr constant_ptr;
7125 </pre>
7126 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
7132 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
7133 an expression or *. If they delimit an expression (which specifies the size of an array), the
7134 expression shall have an integer type. If the expression is a constant expression, it shall
7135 have a value greater than zero. The element type shall not be an incomplete or function
7136 type. The optional type qualifiers and the keyword static shall appear only in a
7137 declaration of a function parameter with an array type, and then only in the outermost
7138 array type derivation.
7140 If an identifier is declared as having a variably modified type, it shall be an ordinary
7141 identifier (as defined in <a href="#6.2.3">6.2.3</a>), have no linkage, and have either block scope or function
7142 prototype scope. If an identifier is declared to be an object with static or thread storage
7143 duration, it shall not have a variable length array type.
7146 If, in the declaration ''T D1'', D1 has one of the forms:
7147 <pre>
7150 D[ type-qualifier-list static assignment-expression ]
7152 </pre>
7153 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7154 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note142"><b>142)</b></a></sup>
7155 (See <a href="#6.7.6.3">6.7.6.3</a> for the meaning of the optional type qualifiers and the keyword static.)
7157 If the size is not present, the array type is an incomplete type. If the size is * instead of
7158 being an expression, the array type is a variable length array type of unspecified size,
7159 which can only be used in declarations or type names with function prototype scope;<sup><a href="#note143"><b>143)</b></a></sup>
7161 <!--page 148 -->
7162 such arrays are nonetheless complete types. If the size is an integer constant expression
7163 and the element type has a known constant size, the array type is not a variable length
7164 array type; otherwise, the array type is a variable length array type. (Variable length
7165 arrays are a conditional feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.)
7167 If the size is an expression that is not an integer constant expression: if it occurs in a
7168 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
7169 each time it is evaluated it shall have a value greater than zero. The size of each instance
7170 of a variable length array type does not change during its lifetime. Where a size
7171 expression is part of the operand of a sizeof operator and changing the value of the
7172 size expression would not affect the result of the operator, it is unspecified whether or not
7173 the size expression is evaluated.
7175 For two array types to be compatible, both shall have compatible element types, and if
7176 both size specifiers are present, and are integer constant expressions, then both size
7177 specifiers shall have the same constant value. If the two array types are used in a context
7178 which requires them to be compatible, it is undefined behavior if the two size specifiers
7179 evaluate to unequal values.
7181 EXAMPLE 1
7182 <pre>
7184 </pre>
7185 declares an array of float numbers and an array of pointers to float numbers.
7188 EXAMPLE 2 Note the distinction between the declarations
7189 <pre>
7190 extern int *x;
7191 extern int y[];
7192 </pre>
7193 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
7194 (an incomplete type), the storage for which is defined elsewhere.
7197 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
7198 <pre>
7199 extern int n;
7200 extern int m;
7201 void fcompat(void)
7202 {
7203 int a[n][6][m];
7205 int c[n][n][6][m];
7206 int (*r)[n][n][n+1];
7208 r = c; // compatible, but defined behavior only if
7210 }
7211 </pre>
7216 <!--page 149 -->
7218 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
7219 function prototype scope. Array objects declared with the _Thread_local, static, or extern
7220 storage-class specifier cannot have a variable length array (VLA) type. However, an object declared with
7221 the static storage-class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all
7222 identifiers declared with a VM type have to be ordinary identifiers and cannot, therefore, be members of
7223 structures or unions.
7224 <pre>
7225 extern int n;
7226 int A[n]; // invalid: file scope VLA
7227 extern int (*p2)[n]; // invalid: file scope VM
7228 int B[100]; // valid: file scope but not VM
7229 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
7230 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
7231 {
7232 typedef int VLA[m][m]; // valid: block scope typedef VLA
7233 struct tag {
7234 int (*y)[n]; // invalid: y not ordinary identifier
7235 int z[n]; // invalid: z not ordinary identifier
7236 };
7237 int D[m]; // valid: auto VLA
7238 static int E[m]; // invalid: static block scope VLA
7239 extern int F[m]; // invalid: F has linkage and is VLA
7240 int (*s)[m]; // valid: auto pointer to VLA
7241 extern int (*r)[m]; // invalid: r has linkage and points to VLA
7242 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
7243 }
7244 </pre>
7246 <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>),
7250 <p><small><a name="note142" href="#note142">142)</a> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
7251 </small>
7252 <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>).
7253 </small>
7255 <h5><a name="6.7.6.3" href="#6.7.6.3">6.7.6.3 Function declarators (including prototypes)</a></h5>
7258 A function declarator shall not specify a return type that is a function type or an array
7259 type.
7261 The only storage-class specifier that shall occur in a parameter declaration is register.
7263 An identifier list in a function declarator that is not part of a definition of that function
7264 shall be empty.
7266 After adjustment, the parameters in a parameter type list in a function declarator that is
7267 part of a definition of that function shall not have incomplete type.
7270 If, in the declaration ''T D1'', D1 has the form
7271 <!--page 150 -->
7272 <pre>
7273 D( parameter-type-list )
7274 </pre>
7275 or
7276 <pre>
7278 </pre>
7279 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
7280 T '', then the type specified for ident is ''derived-declarator-type-list function returning
7281 T ''.
7283 A parameter type list specifies the types of, and may declare identifiers for, the
7284 parameters of the function.
7286 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
7287 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
7288 array type derivation. If the keyword static also appears within the [ and ] of the
7289 array type derivation, then for each call to the function, the value of the corresponding
7290 actual argument shall provide access to the first element of an array with at least as many
7291 elements as specified by the size expression.
7293 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
7296 If the list terminates with an ellipsis (, ...), no information about the number or types
7299 The special case of an unnamed parameter of type void as the only item in the list
7300 specifies that the function has no parameters.
7302 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
7303 parameter name, it shall be taken as a typedef name.
7305 If the function declarator is not part of a definition of that function, parameters may have
7306 incomplete type and may use the [*] notation in their sequences of declarator specifiers
7307 to specify variable length array types.
7309 The storage-class specifier in the declaration specifiers for a parameter declaration, if
7310 present, is ignored unless the declared parameter is one of the members of the parameter
7311 type list for a function definition.
7313 An identifier list declares only the identifiers of the parameters of the function. An empty
7314 list in a function declarator that is part of a definition of that function specifies that the
7315 function has no parameters. The empty list in a function declarator that is not part of a
7316 definition of that function specifies that no information about the number or types of the
7321 <!--page 151 -->
7323 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note146"><b>146)</b></a></sup>
7324 Moreover, the parameter type lists, if both are present, shall agree in the number of
7325 parameters and in use of the ellipsis terminator; corresponding parameters shall have
7326 compatible types. If one type has a parameter type list and the other type is specified by a
7327 function declarator that is not part of a function definition and that contains an empty
7328 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
7329 parameter shall be compatible with the type that results from the application of the
7330 default argument promotions. If one type has a parameter type list and the other type is
7331 specified by a function definition that contains a (possibly empty) identifier list, both shall
7332 agree in the number of parameters, and the type of each prototype parameter shall be
7333 compatible with the type that results from the application of the default argument
7334 promotions to the type of the corresponding identifier. (In the determination of type
7335 compatibility and of a composite type, each parameter declared with function or array
7336 type is taken as having the adjusted type and each parameter declared with qualified type
7337 is taken as having the unqualified version of its declared type.)
7339 EXAMPLE 1 The declaration
7340 <pre>
7341 int f(void), *fip(), (*pfi)();
7342 </pre>
7343 declares a function f with no parameters returning an int, a function fip with no parameter specification
7344 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
7345 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
7346 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
7347 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
7348 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
7349 designator, which is then used to call the function; it returns an int.
7351 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
7352 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
7353 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
7354 the identifier of the pointer pfi has block scope and no linkage.
7357 EXAMPLE 2 The declaration
7358 <pre>
7359 int (*apfi[3])(int *x, int *y);
7360 </pre>
7361 declares an array apfi of three pointers to functions returning int. Each of these functions has two
7362 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
7363 go out of scope at the end of the declaration of apfi.
7366 EXAMPLE 3 The declaration
7367 <pre>
7368 int (*fpfi(int (*)(long), int))(int, ...);
7369 </pre>
7370 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
7371 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
7372 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
7375 <!--page 152 -->
7376 additional arguments of any type.
7379 EXAMPLE 4 The following prototype has a variably modified parameter.
7380 <pre>
7381 void addscalar(int n, int m,
7382 double a[n][n*m+300], double x);
7383 int main()
7384 {
7387 return 0;
7388 }
7389 void addscalar(int n, int m,
7390 double a[n][n*m+300], double x)
7391 {
7394 // a is a pointer to a VLA with n*m+300 elements
7395 a[i][j] += x;
7396 }
7397 </pre>
7400 EXAMPLE 5 The following are all compatible function prototype declarators.
7401 <pre>
7402 double maximum(int n, int m, double a[n][m]);
7403 double maximum(int n, int m, double a[*][*]);
7404 double maximum(int n, int m, double a[ ][*]);
7405 double maximum(int n, int m, double a[ ][m]);
7406 </pre>
7407 as are:
7408 <pre>
7409 void f(double (* restrict a)[5]);
7410 void f(double a[restrict][5]);
7413 </pre>
7414 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
7415 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
7417 <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>).
7418 <!--page 153 -->
7421 <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
7422 correspond to the ellipsis.
7423 </small>
7424 <p><small><a name="note145" href="#note145">145)</a> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
7425 </small>
7426 <p><small><a name="note146" href="#note146">146)</a> If both function types are ''old style'', parameter types are not compared.
7427 </small>
7432 <pre>
7433 type-name:
7435 abstract-declarator:
7436 pointer
7438 direct-abstract-declarator:
7439 ( abstract-declarator )
7443 assignment-expression ]
7445 assignment-expression ]
7448 </pre>
7451 In several contexts, it is necessary to specify a type. This is accomplished using a type
7452 name, which is syntactically a declaration for a function or an object of that type that
7455 EXAMPLE The constructions
7456 <pre>
7457 (a) int
7458 (b) int *
7459 (c) int *[3]
7460 (d) int (*)[3]
7461 (e) int (*)[*]
7462 (f) int *()
7463 (g) int (*)(void)
7464 (h) int (*const [])(unsigned int, ...)
7465 </pre>
7466 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
7467 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
7468 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
7469 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
7470 parameter that has type unsigned int and an unspecified number of other parameters, returning an
7471 int.
7476 <!--page 154 -->
7479 <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
7480 parameter specification'', rather than redundant parentheses around the omitted identifier.
7481 </small>
7486 <pre>
7487 typedef-name:
7488 identifier
7489 </pre>
7492 If a typedef name specifies a variably modified type then it shall have block scope.
7495 In a declaration whose storage-class specifier is typedef, each declarator defines an
7496 identifier to be a typedef name that denotes the type specified for the identifier in the way
7497 described in <a href="#6.7.6">6.7.6</a>. Any array size expressions associated with variable length array
7498 declarators are evaluated each time the declaration of the typedef name is reached in the
7499 order of execution. A typedef declaration does not introduce a new type, only a
7500 synonym for the type so specified. That is, in the following declarations:
7501 <pre>
7502 typedef T type_ident;
7503 type_ident D;
7504 </pre>
7505 type_ident is defined as a typedef name with the type specified by the declaration
7506 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
7507 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
7508 typedef name shares the same name space as other identifiers declared in ordinary
7509 declarators.
7511 EXAMPLE 1 After
7512 <pre>
7513 typedef int MILES, KLICKSP();
7514 typedef struct { double hi, lo; } range;
7515 </pre>
7516 the constructions
7517 <pre>
7518 MILES distance;
7519 extern KLICKSP *metricp;
7520 range x;
7521 range z, *zp;
7522 </pre>
7523 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
7524 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
7525 such a structure. The object distance has a type compatible with any other int object.
7528 EXAMPLE 2 After the declarations
7529 <pre>
7530 typedef struct s1 { int x; } t1, *tp1;
7531 typedef struct s2 { int x; } t2, *tp2;
7532 </pre>
7533 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
7534 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
7535 <!--page 155 -->
7537 EXAMPLE 3 The following obscure constructions
7538 <pre>
7539 typedef signed int t;
7540 typedef int plain;
7541 struct tag {
7542 unsigned t:4;
7543 const t:5;
7544 plain r:5;
7545 };
7546 </pre>
7547 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
7548 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
7549 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
7550 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
7551 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
7552 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
7553 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
7554 in an inner scope by
7555 <pre>
7556 t f(t (t));
7557 long t;
7558 </pre>
7559 then a function f is declared with type ''function returning signed int with one unnamed parameter
7560 with type pointer to function returning signed int with one unnamed parameter with type signed
7561 int'', and an identifier t with type long int.
7564 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
7565 following declarations of the signal function specify exactly the same type, the first without making use
7566 of any typedef names.
7567 <pre>
7568 typedef void fv(int), (*pfv)(int);
7569 void (*signal(int, void (*)(int)))(int);
7570 fv *signal(int, fv *);
7571 pfv signal(int, pfv);
7572 </pre>
7575 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
7576 time the typedef name is defined, not each time it is used:
7577 <!--page 156 -->
7578 <pre>
7579 void copyt(int n)
7580 {
7581 typedef int B[n]; // B is n ints, n evaluated now
7582 n += 1;
7583 B a; // a is n ints, n without += 1
7584 int b[n]; // a and b are different sizes
7586 a[i-1] = b[i];
7587 }
7588 </pre>
7593 <pre>
7594 initializer:
7595 assignment-expression
7596 { initializer-list }
7597 { initializer-list , }
7598 initializer-list:
7601 designation:
7602 designator-list =
7603 designator-list:
7604 designator
7605 designator-list designator
7606 designator:
7607 [ constant-expression ]
7608 . identifier
7609 </pre>
7612 No initializer shall attempt to provide a value for an object not contained within the entity
7613 being initialized.
7615 The type of the entity to be initialized shall be an array of unknown size or a complete
7616 object type that is not a variable length array type.
7618 All the expressions in an initializer for an object that has static or thread storage duration
7619 shall be constant expressions or string literals.
7621 If the declaration of an identifier has block scope, and the identifier has external or
7622 internal linkage, the declaration shall have no initializer for the identifier.
7624 If a designator has the form
7625 <pre>
7626 [ constant-expression ]
7627 </pre>
7628 then the current object (defined below) shall have array type and the expression shall be
7629 an integer constant expression. If the array is of unknown size, any nonnegative value is
7630 valid.
7632 If a designator has the form
7633 <pre>
7634 . identifier
7635 </pre>
7636 then the current object (defined below) shall have structure or union type and the
7637 identifier shall be the name of a member of that type.
7638 <!--page 157 -->
7641 An initializer specifies the initial value stored in an object.
7643 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
7644 members of objects of structure and union type do not participate in initialization.
7645 Unnamed members of structure objects have indeterminate value even after initialization.
7647 If an object that has automatic storage duration is not initialized explicitly, its value is
7648 indeterminate. If an object that has static or thread storage duration is not initialized
7649 explicitly, then:
7650 <ul>
7651 <li> if it has pointer type, it is initialized to a null pointer;
7652 <li> if it has arithmetic type, it is initialized to (positive or unsigned) zero;
7653 <li> if it is an aggregate, every member is initialized (recursively) according to these rules,
7654 and any padding is initialized to zero bits;
7655 <li> if it is a union, the first named member is initialized (recursively) according to these
7656 rules, and any padding is initialized to zero bits;
7657 </ul>
7659 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
7660 initial value of the object is that of the expression (after conversion); the same type
7661 constraints and conversions as for simple assignment apply, taking the type of the scalar
7662 to be the unqualified version of its declared type.
7664 The rest of this subclause deals with initializers for objects that have aggregate or union
7665 type.
7667 The initializer for a structure or union object that has automatic storage duration shall be
7668 either an initializer list as described below, or a single expression that has compatible
7669 structure or union type. In the latter case, the initial value of the object, including
7670 unnamed members, is that of the expression.
7672 An array of character type may be initialized by a character string literal or UTF-8 string
7673 literal, optionally enclosed in braces. Successive bytes of the string literal (including the
7674 terminating null character if there is room or if the array is of unknown size) initialize the
7675 elements of the array.
7677 An array with element type compatible with a qualified or unqualified version of
7678 wchar_t may be initialized by a wide string literal, optionally enclosed in braces.
7679 Successive wide characters of the wide string literal (including the terminating null wide
7680 character if there is room or if the array is of unknown size) initialize the elements of the
7681 array.
7683 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
7684 enclosed list of initializers for the elements or named members.
7685 <!--page 158 -->
7687 Each brace-enclosed initializer list has an associated current object. When no
7688 designations are present, subobjects of the current object are initialized in order according
7689 to the type of the current object: array elements in increasing subscript order, structure
7690 members in declaration order, and the first named member of a union.<sup><a href="#note148"><b>148)</b></a></sup> In contrast, a
7691 designation causes the following initializer to begin initialization of the subobject
7692 described by the designator. Initialization then continues forward in order, beginning
7693 with the next subobject after that described by the designator.<sup><a href="#note149"><b>149)</b></a></sup>
7695 Each designator list begins its description with the current object associated with the
7696 closest surrounding brace pair. Each item in the designator list (in order) specifies a
7697 particular member of its current object and changes the current object for the next
7698 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
7699 designator list is the subobject to be initialized by the following initializer.
7701 The initialization shall occur in initializer list order, each initializer provided for a
7702 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note151"><b>151)</b></a></sup>
7703 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
7704 objects that have static storage duration.
7706 If the aggregate or union contains elements or members that are aggregates or unions,
7707 these rules apply recursively to the subaggregates or contained unions. If the initializer of
7708 a subaggregate or contained union begins with a left brace, the initializers enclosed by
7709 that brace and its matching right brace initialize the elements or members of the
7710 subaggregate or the contained union. Otherwise, only enough initializers from the list are
7711 taken to account for the elements or members of the subaggregate or the first member of
7712 the contained union; any remaining initializers are left to initialize the next element or
7713 member of the aggregate of which the current subaggregate or contained union is a part.
7715 If there are fewer initializers in a brace-enclosed list than there are elements or members
7716 of an aggregate, or fewer characters in a string literal used to initialize an array of known
7717 size than there are elements in the array, the remainder of the aggregate shall be
7718 initialized implicitly the same as objects that have static storage duration.
7722 <!--page 159 -->
7724 If an array of unknown size is initialized, its size is determined by the largest indexed
7725 element with an explicit initializer. The array type is completed at the end of its
7726 initializer list.
7728 The evaluations of the initialization list expressions are indeterminately sequenced with
7729 respect to one another and thus the order in which any side effects occur is
7732 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
7733 <pre>
7736 </pre>
7740 EXAMPLE 2 The declaration
7741 <pre>
7743 </pre>
7744 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
7745 and there are three initializers.
7748 EXAMPLE 3 The declaration
7749 <pre>
7754 };
7755 </pre>
7756 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
7758 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
7759 been achieved by
7760 <pre>
7763 };
7764 </pre>
7765 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
7769 EXAMPLE 4 The declaration
7770 <pre>
7773 };
7774 </pre>
7775 initializes the first column of z as specified and initializes the rest with zeros.
7778 EXAMPLE 5 The declaration
7779 <pre>
7781 </pre>
7782 is a definition with an inconsistently bracketed initialization. It defines an array with two element
7786 <!--page 160 -->
7790 EXAMPLE 6 The declaration
7791 <pre>
7793 { 1 },
7796 };
7797 </pre>
7798 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
7800 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
7801 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
7802 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
7803 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
7804 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
7805 diagnostic message would have been issued. The same initialization result could have been achieved by:
7806 <pre>
7811 };
7812 </pre>
7813 or by:
7814 <pre>
7816 {
7817 { 1 },
7818 },
7819 {
7821 },
7822 {
7824 { 6 },
7825 }
7826 };
7827 </pre>
7828 in a fully bracketed form.
7830 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
7831 cause confusion.
7834 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
7835 declaration
7836 <pre>
7837 typedef int A[]; // OK - declared with block scope
7838 </pre>
7839 the declaration
7840 <pre>
7842 </pre>
7843 is identical to
7844 <pre>
7846 </pre>
7847 due to the rules for incomplete types.
7848 <!--page 161 -->
7850 EXAMPLE 8 The declaration
7851 <pre>
7853 </pre>
7854 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
7855 This declaration is identical to
7856 <pre>
7857 char s[] = { 'a', 'b', 'c', '\0' },
7858 t[] = { 'a', 'b', 'c' };
7859 </pre>
7860 The contents of the arrays are modifiable. On the other hand, the declaration
7861 <pre>
7862 char *p = "abc";
7863 </pre>
7864 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
7865 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
7866 modify the contents of the array, the behavior is undefined.
7869 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
7870 designators:
7871 <pre>
7872 enum { member_one, member_two };
7873 const char *nm[] = {
7874 [member_two] = "member two",
7875 [member_one] = "member one",
7876 };
7877 </pre>
7880 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
7881 <pre>
7883 </pre>
7886 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
7887 might be misunderstood:
7888 <pre>
7889 struct { int a[3], b; } w[] =
7891 </pre>
7894 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
7895 <pre>
7896 int a[MAX] = {
7898 };
7899 </pre>
7901 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
7902 than ten, some of the values provided by the first five initializers will be overridden by the second five.
7905 EXAMPLE 13 Any member of a union can be initialized:
7906 <pre>
7907 union { /* ... */ } u = { .any_member = 42 };
7908 </pre>
7910 <p><b> Forward references</b>: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>).
7911 <!--page 162 -->
7914 <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
7915 subobjects are initialized as usual, but the subaggregate or contained union does not become the
7916 current object: current objects are associated only with brace-enclosed initializer lists.
7917 </small>
7918 <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
7919 the next subobject of an object containing the union.
7920 </small>
7921 <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
7922 the surrounding brace pair. Note, too, that each separate designator list is independent.
7923 </small>
7924 <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
7925 not be evaluated at all.
7926 </small>
7927 <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.
7928 </small>
7933 <pre>
7934 static_assert-declaration:
7935 _Static_assert ( constant-expression , string-literal ) ;
7936 </pre>
7939 The constant expression shall compare unequal to 0.
7942 The constant expression shall be an integer constant expression. If the value of the
7943 constant expression compares unequal to 0, the declaration has no effect. Otherwise, the
7944 constraint is violated and the implementation shall produce a diagnostic message that
7945 includes the text of the string literal, except that characters not in the basic source
7946 character set are not required to appear in the message.
7948 <!--page 163 -->
7953 <pre>
7954 statement:
7955 labeled-statement
7956 compound-statement
7957 expression-statement
7958 selection-statement
7959 iteration-statement
7960 jump-statement
7961 </pre>
7964 A statement specifies an action to be performed. Except as indicated, statements are
7965 executed in sequence.
7967 A block allows a set of declarations and statements to be grouped into one syntactic unit.
7968 The initializers of objects that have automatic storage duration, and the variable length
7969 array declarators of ordinary identifiers with block scope, are evaluated and the values are
7970 stored in the objects (including storing an indeterminate value in objects without an
7971 initializer) each time the declaration is reached in the order of execution, as if it were a
7972 statement, and within each declaration in the order that declarators appear.
7974 A full expression is an expression that is not part of another expression or of a declarator.
7975 Each of the following is a full expression: an initializer that is not part of a compound
7976 literal; the expression in an expression statement; the controlling expression of a selection
7977 statement (if or switch); the controlling expression of a while or do statement; each
7978 of the (optional) expressions of a for statement; the (optional) expression in a return
7979 statement. There is a sequence point between the evaluation of a full expression and the
7980 evaluation of the next full expression to be evaluated.
7981 <p><b> Forward references</b>: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
7982 (<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>).
7987 <pre>
7988 labeled-statement:
7989 identifier : statement
7990 case constant-expression : statement
7991 default : statement
7992 </pre>
7995 A case or default label shall appear only in a switch statement. Further
7996 constraints on such labels are discussed under the switch statement.
7997 <!--page 164 -->
7999 Label names shall be unique within a function.
8002 Any statement may be preceded by a prefix that declares an identifier as a label name.
8003 Labels in themselves do not alter the flow of control, which continues unimpeded across
8004 them.
8005 <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>).
8010 <pre>
8011 compound-statement:
8013 block-item-list:
8014 block-item
8015 block-item-list block-item
8016 block-item:
8017 declaration
8018 statement
8019 </pre>
8022 A compound statement is a block.
8027 <pre>
8028 expression-statement:
8030 </pre>
8033 The expression in an expression statement is evaluated as a void expression for its side
8036 A null statement (consisting of just a semicolon) performs no operations.
8038 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
8039 discarding of its value may be made explicit by converting the expression to a void expression by means of
8040 a cast:
8041 <pre>
8042 int p(int);
8043 /* ... */
8044 (void)p(0);
8045 </pre>
8049 <!--page 165 -->
8051 EXAMPLE 2 In the program fragment
8052 <pre>
8053 char *s;
8054 /* ... */
8055 while (*s++ != '\0')
8056 ;
8057 </pre>
8058 a null statement is used to supply an empty loop body to the iteration statement.
8061 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
8062 statement.
8063 <pre>
8064 while (loop1) {
8065 /* ... */
8066 while (loop2) {
8067 /* ... */
8068 if (want_out)
8069 goto end_loop1;
8070 /* ... */
8071 }
8072 /* ... */
8073 end_loop1: ;
8074 }
8075 </pre>
8080 <p><small><a name="note153" href="#note153">153)</a> Such as assignments, and function calls which have side effects.
8081 </small>
8086 <pre>
8087 selection-statement:
8088 if ( expression ) statement
8089 if ( expression ) statement else statement
8090 switch ( expression ) statement
8091 </pre>
8094 A selection statement selects among a set of statements depending on the value of a
8095 controlling expression.
8097 A selection statement is a block whose scope is a strict subset of the scope of its
8098 enclosing block. Each associated substatement is also a block whose scope is a strict
8099 subset of the scope of the selection statement.
8104 The controlling expression of an if statement shall have scalar type.
8107 In both forms, the first substatement is executed if the expression compares unequal to 0.
8108 In the else form, the second substatement is executed if the expression compares equal
8109 <!--page 166 -->
8110 to 0. If the first substatement is reached via a label, the second substatement is not
8111 executed.
8113 An else is associated with the lexically nearest preceding if that is allowed by the
8114 syntax.
8119 The controlling expression of a switch statement shall have integer type.
8121 If a switch statement has an associated case or default label within the scope of an
8122 identifier with a variably modified type, the entire switch statement shall be within the
8125 The expression of each case label shall be an integer constant expression and no two of
8126 the case constant expressions in the same switch statement shall have the same value
8127 after conversion. There may be at most one default label in a switch statement.
8128 (Any enclosed switch statement may have a default label or case constant
8129 expressions with values that duplicate case constant expressions in the enclosing
8130 switch statement.)
8133 A switch statement causes control to jump to, into, or past the statement that is the
8134 switch body, depending on the value of a controlling expression, and on the presence of a
8135 default label and the values of any case labels on or in the switch body. A case or
8136 default label is accessible only within the closest enclosing switch statement.
8138 The integer promotions are performed on the controlling expression. The constant
8139 expression in each case label is converted to the promoted type of the controlling
8140 expression. If a converted value matches that of the promoted controlling expression,
8141 control jumps to the statement following the matched case label. Otherwise, if there is
8142 a default label, control jumps to the labeled statement. If no converted case constant
8143 expression matches and there is no default label, no part of the switch body is
8144 executed.
8147 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
8148 switch statement.
8153 <!--page 167 -->
8155 EXAMPLE In the artificial program fragment
8156 <pre>
8157 switch (expr)
8158 {
8159 int i = 4;
8160 f(i);
8161 case 0:
8162 i = 17;
8163 /* falls through into default code */
8164 default:
8165 printf("%d\n", i);
8166 }
8167 </pre>
8168 the object whose identifier is i exists with automatic storage duration (within the block) but is never
8169 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
8170 access an indeterminate value. Similarly, the call to the function f cannot be reached.
8174 <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
8175 default label associated with the switch that is in the block containing the declaration.
8176 </small>
8181 <pre>
8182 iteration-statement:
8183 while ( expression ) statement
8184 do statement while ( expression ) ;
8185 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
8187 </pre>
8190 The controlling expression of an iteration statement shall have scalar type.
8192 The declaration part of a for statement shall only declare identifiers for objects having
8193 storage class auto or register.
8196 An iteration statement causes a statement called the loop body to be executed repeatedly
8197 until the controlling expression compares equal to 0. The repetition occurs regardless of
8198 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note155"><b>155)</b></a></sup>
8200 An iteration statement is a block whose scope is a strict subset of the scope of its
8201 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
8202 of the iteration statement.
8204 An iteration statement whose controlling expression is not a constant expression,<sup><a href="#note156"><b>156)</b></a></sup> that
8205 performs no input/output operations, does not access volatile objects, and performs no
8206 synchronization or atomic operations in its body, controlling expression, or (in the case of
8208 <!--page 168 -->
8209 a for statement) its expression-3, may be assumed by the implementation to
8213 <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
8214 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
8215 </small>
8216 <p><small><a name="note156" href="#note156">156)</a> An omitted controlling expression is replaced by a nonzero constant, which is a constant expression.
8217 </small>
8218 <p><small><a name="note157" href="#note157">157)</a> This is intended to allow compiler transformations such as removal of empty loops even when
8219 termination cannot be proven.
8220 </small>
8224 The evaluation of the controlling expression takes place before each execution of the loop
8225 body.
8229 The evaluation of the controlling expression takes place after each execution of the loop
8230 body.
8234 The statement
8235 <pre>
8237 </pre>
8238 behaves as follows: The expression expression-2 is the controlling expression that is
8239 evaluated before each execution of the loop body. The expression expression-3 is
8240 evaluated as a void expression after each execution of the loop body. If clause-1 is a
8241 declaration, the scope of any identifiers it declares is the remainder of the declaration and
8242 the entire loop, including the other two expressions; it is reached in the order of execution
8243 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
8244 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note158"><b>158)</b></a></sup>
8247 nonzero constant.
8250 <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
8251 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
8252 such that execution of the loop continues until the expression compares equal to 0; and expression-3
8253 specifies an operation (such as incrementing) that is performed after each iteration.
8254 </small>
8259 <pre>
8260 jump-statement:
8261 goto identifier ;
8262 continue ;
8263 break ;
8265 </pre>
8270 <!--page 169 -->
8273 A jump statement causes an unconditional jump to another place.
8278 The identifier in a goto statement shall name a label located somewhere in the enclosing
8279 function. A goto statement shall not jump from outside the scope of an identifier having
8280 a variably modified type to inside the scope of that identifier.
8283 A goto statement causes an unconditional jump to the statement prefixed by the named
8284 label in the enclosing function.
8286 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
8287 following outline presents one possible approach to a problem based on these three assumptions:
8288 <ol>
8289 <li> The general initialization code accesses objects only visible to the current function.
8290 <li> The general initialization code is too large to warrant duplication.
8291 <li> The code to determine the next operation is at the head of the loop. (To allow it to be reached by
8292 continue statements, for example.)
8293 <!--page 170 -->
8294 <pre>
8295 /* ... */
8296 goto first_time;
8297 for (;;) {
8298 // determine next operation
8299 /* ... */
8300 if (need to reinitialize) {
8301 // reinitialize-only code
8302 /* ... */
8303 first_time:
8304 // general initialization code
8305 /* ... */
8306 continue;
8307 }
8308 // handle other operations
8309 /* ... */
8310 }
8311 </pre>
8312 </ol>
8314 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
8315 modified types. A jump within the scope, however, is permitted.
8316 <pre>
8317 goto lab3; // invalid: going INTO scope of VLA.
8318 {
8319 double a[n];
8321 lab3:
8323 goto lab4; // valid: going WITHIN scope of VLA.
8325 lab4:
8327 }
8328 goto lab4; // invalid: going INTO scope of VLA.
8329 </pre>
8335 A continue statement shall appear only in or as a loop body.
8338 A continue statement causes a jump to the loop-continuation portion of the smallest
8339 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
8340 of the statements
8341 while (/* ... */) { do { for (/* ... */) {
8342 <pre>
8343 /* ... */ /* ... */ /* ... */
8344 continue; continue; continue;
8345 /* ... */ /* ... */ /* ... */
8346 </pre>
8347 contin: ; contin: ; contin: ;
8348 } } while (/* ... */); }
8349 unless the continue statement shown is in an enclosed iteration statement (in which
8350 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note159"><b>159)</b></a></sup>
8353 <p><small><a name="note159" href="#note159">159)</a> Following the contin: label is a null statement.
8354 </small>
8359 A break statement shall appear only in or as a switch body or loop body.
8362 A break statement terminates execution of the smallest enclosing switch or iteration
8363 statement.
8367 <!--page 171 -->
8372 A return statement with an expression shall not appear in a function whose return type
8373 is void. A return statement without an expression shall only appear in a function
8374 whose return type is void.
8377 A return statement terminates execution of the current function and returns control to
8378 its caller. A function may have any number of return statements.
8380 If a return statement with an expression is executed, the value of the expression is
8381 returned to the caller as the value of the function call expression. If the expression has a
8382 type different from the return type of the function in which it appears, the value is
8383 converted as if by assignment to an object having the return type of the function.<sup><a href="#note160"><b>160)</b></a></sup>
8385 EXAMPLE In:
8386 <pre>
8387 struct s { double i; } f(void);
8388 union {
8389 struct {
8390 int f1;
8391 struct s f2;
8392 } u1;
8393 struct {
8394 struct s f3;
8395 int f4;
8396 } u2;
8397 } g;
8398 struct s f(void)
8399 {
8400 return g.u1.f2;
8401 }
8402 /* ... */
8403 g.u2.f3 = f();
8404 </pre>
8405 there is no undefined behavior, although there would be if the assignment were done directly (without using
8406 a function call to fetch the value).
8411 <!--page 172 -->
8414 <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
8415 apply to the case of function return. The representation of floating-point values may have wider range
8416 or precision than implied by the type; a cast may be used to remove this extra range and precision.
8417 </small>
8422 <pre>
8423 translation-unit:
8424 external-declaration
8425 translation-unit external-declaration
8426 external-declaration:
8427 function-definition
8428 declaration
8429 </pre>
8432 The storage-class specifiers auto and register shall not appear in the declaration
8433 specifiers in an external declaration.
8435 There shall be no more than one external definition for each identifier declared with
8436 internal linkage in a translation unit. Moreover, if an identifier declared with internal
8437 linkage is used in an expression (other than as a part of the operand of a sizeof
8438 operator whose result is an integer constant), there shall be exactly one external definition
8439 for the identifier in the translation unit.
8442 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,
8443 which consists of a sequence of external declarations. These are described as ''external''
8444 because they appear outside any function (and hence have file scope). As discussed in
8445 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
8446 by the identifier is a definition.
8448 An external definition is an external declaration that is also a definition of a function
8449 (other than an inline definition) or an object. If an identifier declared with external
8450 linkage is used in an expression (other than as part of the operand of a sizeof operator
8451 whose result is an integer constant), somewhere in the entire program there shall be
8452 exactly one external definition for the identifier; otherwise, there shall be no more than
8458 <!--page 173 -->
8461 <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
8462 external definition for it.
8463 </small>
8468 <pre>
8469 function-definition:
8471 declaration-list:
8472 declaration
8473 declaration-list declaration
8474 </pre>
8477 The identifier declared in a function definition (which is the name of the function) shall
8478 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note162"><b>162)</b></a></sup>
8480 The return type of a function shall be void or a complete object type other than array
8481 type.
8483 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
8484 static.
8486 If the declarator includes a parameter type list, the declaration of each parameter shall
8487 include an identifier, except for the special case of a parameter list consisting of a single
8488 parameter of type void, in which case there shall not be an identifier. No declaration list
8489 shall follow.
8491 If the declarator includes an identifier list, each declaration in the declaration list shall
8492 have at least one declarator, those declarators shall declare only identifiers from the
8493 identifier list, and every identifier in the identifier list shall be declared. An identifier
8494 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
8495 declaration list shall contain no storage-class specifier other than register and no
8496 initializations.
8500 <!--page 174 -->
8503 The declarator in a function definition specifies the name of the function being defined
8504 and the identifiers of its parameters. If the declarator includes a parameter type list, the
8505 list also specifies the types of all the parameters; such a declarator also serves as a
8506 function prototype for later calls to the same function in the same translation unit. If the
8507 declarator includes an identifier list,<sup><a href="#note163"><b>163)</b></a></sup> the types of the parameters shall be declared in a
8508 following declaration list. In either case, the type of each parameter is adjusted as
8509 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
8510 type.
8512 If a function that accepts a variable number of arguments is defined without a parameter
8513 type list that ends with the ellipsis notation, the behavior is undefined.
8515 Each parameter has automatic storage duration; its identifier is an lvalue.<sup><a href="#note164"><b>164)</b></a></sup> The layout
8516 of the storage for parameters is unspecified.
8518 On entry to the function, the size expressions of each variably modified parameter are
8519 evaluated and the value of each argument expression is converted to the type of the
8520 corresponding parameter as if by assignment. (Array expressions and function
8521 designators as arguments were converted to pointers before the call.)
8523 After all parameters have been assigned, the compound statement that constitutes the
8524 body of the function definition is executed.
8526 If the } that terminates a function is reached, and the value of the function call is used by
8527 the caller, the behavior is undefined.
8529 EXAMPLE 1 In the following:
8530 <pre>
8531 extern int max(int a, int b)
8532 {
8533 return a > b ? a : b;
8534 }
8535 </pre>
8536 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
8537 function declarator; and
8538 <pre>
8539 { return a > b ? a : b; }
8540 </pre>
8541 is the function body. The following similar definition uses the identifier-list form for the parameter
8542 declarations:
8547 <!--page 175 -->
8548 <pre>
8549 extern int max(a, b)
8550 int a, b;
8551 {
8552 return a > b ? a : b;
8553 }
8554 </pre>
8555 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
8556 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
8557 to the function, whereas the second form does not.
8560 EXAMPLE 2 To pass one function to another, one might say
8561 <pre>
8562 int f(void);
8563 /* ... */
8564 g(f);
8565 </pre>
8566 Then the definition of g might read
8567 <pre>
8568 void g(int (*funcp)(void))
8569 {
8570 /* ... */
8571 (*funcp)(); /* or funcp(); ... */
8572 }
8573 </pre>
8574 or, equivalently,
8575 <pre>
8576 void g(int func(void))
8577 {
8578 /* ... */
8579 func(); /* or (*func)(); ... */
8580 }
8581 </pre>
8585 <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:
8587 <pre>
8588 typedef int F(void); // type F is ''function with no parameters
8589 // returning int''
8590 F f, g; // f and g both have type compatible with F
8591 F f { /* ... */ } // WRONG: syntax/constraint error
8592 F g() { /* ... */ } // WRONG: declares that g returns a function
8593 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
8594 int g() { /* ... */ } // RIGHT: g has type compatible with F
8595 F *e(void) { /* ... */ } // e returns a pointer to a function
8596 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
8597 int (*fp)(void); // fp points to a function that has type F
8598 F *Fp; // Fp points to a function that has type F
8599 </pre>
8600 </small>
8601 <p><small><a name="note163" href="#note163">163)</a> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
8602 </small>
8603 <p><small><a name="note164" href="#note164">164)</a> A parameter identifier cannot be redeclared in the function body except in an enclosed block.
8604 </small>
8609 If the declaration of an identifier for an object has file scope and an initializer, the
8610 declaration is an external definition for the identifier.
8612 A declaration of an identifier for an object that has file scope without an initializer, and
8613 without a storage-class specifier or with the storage-class specifier static, constitutes a
8614 tentative definition. If a translation unit contains one or more tentative definitions for an
8615 identifier, and the translation unit contains no external definition for that identifier, then
8616 the behavior is exactly as if the translation unit contains a file scope declaration of that
8617 identifier, with the composite type as of the end of the translation unit, with an initializer
8618 equal to 0.
8620 If the declaration of an identifier for an object is a tentative definition and has internal
8621 linkage, the declared type shall not be an incomplete type.
8622 <!--page 176 -->
8624 EXAMPLE 1
8625 <pre>
8626 int i1 = 1; // definition, external linkage
8627 static int i2 = 2; // definition, internal linkage
8628 extern int i3 = 3; // definition, external linkage
8629 int i4; // tentative definition, external linkage
8630 static int i5; // tentative definition, internal linkage
8631 int i1; // valid tentative definition, refers to previous
8633 int i3; // valid tentative definition, refers to previous
8634 int i4; // valid tentative definition, refers to previous
8636 extern int i1; // refers to previous, whose linkage is external
8637 extern int i2; // refers to previous, whose linkage is internal
8638 extern int i3; // refers to previous, whose linkage is external
8639 extern int i4; // refers to previous, whose linkage is external
8640 extern int i5; // refers to previous, whose linkage is internal
8641 </pre>
8644 EXAMPLE 2 If at the end of the translation unit containing
8645 <pre>
8646 int i[];
8647 </pre>
8648 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
8649 zero on program startup.
8650 <!--page 177 -->
8655 <!--page 178 -->
8656 <pre>
8657 preprocessing-file:
8659 group:
8660 group-part
8661 group group-part
8662 group-part:
8663 if-section
8664 control-line
8665 text-line
8666 # non-directive
8667 if-section:
8669 if-group:
8673 elif-groups:
8674 elif-group
8675 elif-groups elif-group
8676 elif-group:
8678 else-group:
8680 endif-line:
8681 # endif new-line
8682 control-line:
8683 # include pp-tokens new-line
8684 # define identifier replacement-list new-line
8686 replacement-list new-line
8687 # define identifier lparen ... ) replacement-list new-line
8688 # define identifier lparen identifier-list , ... )
8689 replacement-list new-line
8690 # undef identifier new-line
8691 # line pp-tokens new-line
8694 # new-line
8695 text-line:
8697 non-directive:
8698 pp-tokens new-line
8699 lparen:
8700 a ( character not immediately preceded by white-space
8701 replacement-list:
8703 pp-tokens:
8704 preprocessing-token
8705 pp-tokens preprocessing-token
8706 new-line:
8707 the new-line character
8708 </pre>
8711 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
8712 following constraints: The first token in the sequence is a # preprocessing token that (at
8713 the start of translation phase 4) is either the first character in the source file (optionally
8714 after white space containing no new-line characters) or that follows white space
8715 containing at least one new-line character. The last token in the sequence is the first new-
8716 line character that follows the first token in the sequence.<sup><a href="#note165"><b>165)</b></a></sup> A new-line character ends
8717 the preprocessing directive even if it occurs within what would otherwise be an
8719 <!--page 179 -->
8720 invocation of a function-like macro.
8722 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
8723 with any of the directive names appearing in the syntax.
8725 When in a group that is skipped (<a href="#6.10.1">6.10.1</a>), the directive syntax is relaxed to allow any
8726 sequence of preprocessing tokens to occur between the directive name and the following
8727 new-line character.
8730 The only white-space characters that shall appear between preprocessing tokens within a
8731 preprocessing directive (from just after the introducing # preprocessing token through
8732 just before the terminating new-line character) are space and horizontal-tab (including
8733 spaces that have replaced comments or possibly other white-space characters in
8734 translation phase 3).
8737 The implementation can process and skip sections of source files conditionally, include
8738 other source files, and replace macros. These capabilities are called preprocessing,
8739 because conceptually they occur before translation of the resulting translation unit.
8741 The preprocessing tokens within a preprocessing directive are not subject to macro
8742 expansion unless otherwise stated.
8744 EXAMPLE In:
8745 <pre>
8746 #define EMPTY
8748 </pre>
8749 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
8750 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
8751 replaced.
8755 <p><small><a name="note165" href="#note165">165)</a> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
8756 significance, as all white space is equivalent except in certain situations during preprocessing (see the
8757 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
8758 </small>
8763 The expression that controls conditional inclusion shall be an integer constant expression
8764 except that: identifiers (including those lexically identical to keywords) are interpreted as *
8765 described below;<sup><a href="#note166"><b>166)</b></a></sup> and it may contain unary operator expressions of the form
8766 <pre>
8767 defined identifier
8768 </pre>
8769 or
8770 <pre>
8771 defined ( identifier )
8772 </pre>
8773 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
8776 <!--page 180 -->
8777 predefined or if it has been the subject of a #define preprocessing directive without an
8778 intervening #undef directive with the same subject identifier), 0 if it is not.
8780 Each preprocessing token that remains (in the list of preprocessing tokens that will
8781 become the controlling expression) after all macro replacements have occurred shall be in
8785 Preprocessing directives of the forms
8786 <pre>
8789 </pre>
8790 check whether the controlling constant expression evaluates to nonzero.
8792 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
8793 the controlling constant expression are replaced (except for those macro names modified
8794 by the defined unary operator), just as in normal text. If the token defined is
8795 generated as a result of this replacement process or use of the defined unary operator
8796 does not match one of the two specified forms prior to macro replacement, the behavior is
8797 undefined. After all replacements due to macro expansion and the defined unary
8798 operator have been performed, all remaining identifiers (including those lexically
8799 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
8800 token is converted into a token. The resulting tokens compose the controlling constant
8801 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
8802 token conversion and evaluation, all signed integer types and all unsigned integer types
8803 act as if they have the same representation as, respectively, the types intmax_t and
8804 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
8805 character constants, which may involve converting escape sequences into execution
8806 character set members. Whether the numeric value for these character constants matches
8807 the value obtained when an identical character constant occurs in an expression (other
8808 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note168"><b>168)</b></a></sup> Also, whether a
8809 single-character character constant may have a negative value is implementation-defined.
8814 <!--page 181 -->
8816 Preprocessing directives of the forms
8817 <pre>
8820 </pre>
8821 check whether the identifier is or is not currently defined as a macro name. Their
8822 conditions are equivalent to #if defined identifier and #if !defined identifier
8823 respectively.
8825 Each directive's condition is checked in order. If it evaluates to false (zero), the group
8826 that it controls is skipped: directives are processed only through the name that determines
8827 the directive in order to keep track of the level of nested conditionals; the rest of the
8828 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
8829 group. Only the first group whose control condition evaluates to true (nonzero) is
8830 processed. If none of the conditions evaluates to true, and there is a #else directive, the
8831 group controlled by the #else is processed; lacking a #else directive, all the groups
8833 <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
8837 <p><small><a name="note166" href="#note166">166)</a> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
8838 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
8839 </small>
8840 <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
8841 0x8000 is signed and positive within a #if expression even though it would be unsigned in
8842 translation phase 7.
8843 </small>
8844 <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
8845 evaluate to the same value in these two contexts.
8846 #if 'z' - 'a' == 25
8847 if ('z' - 'a' == 25)
8848 </small>
8849 <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
8850 before the terminating new-line character. However, comments may appear anywhere in a source file,
8851 including within a preprocessing directive.
8852 </small>
8857 A #include directive shall identify a header or source file that can be processed by the
8858 implementation.
8861 A preprocessing directive of the form
8862 <pre>
8864 </pre>
8865 searches a sequence of implementation-defined places for a header identified uniquely by
8866 the specified sequence between the < and > delimiters, and causes the replacement of that
8867 directive by the entire contents of the header. How the places are specified or the header
8868 identified is implementation-defined.
8870 A preprocessing directive of the form
8871 <pre>
8872 # include "q-char-sequence" new-line
8873 </pre>
8874 causes the replacement of that directive by the entire contents of the source file identified
8875 by the specified sequence between the " delimiters. The named source file is searched
8878 <!--page 182 -->
8879 for in an implementation-defined manner. If this search is not supported, or if the search
8880 fails, the directive is reprocessed as if it read
8881 <pre>
8882 # include <h-char-sequence> new-line
8883 </pre>
8884 with the identical contained sequence (including > characters, if any) from the original
8885 directive.
8886 <p><!--para 4 -->
8887 A preprocessing directive of the form
8888 <pre>
8889 # include pp-tokens new-line
8890 </pre>
8891 (that does not match one of the two previous forms) is permitted. The preprocessing
8892 tokens after include in the directive are processed just as in normal text. (Each
8893 identifier currently defined as a macro name is replaced by its replacement list of
8894 preprocessing tokens.) The directive resulting after all replacements shall match one of
8895 the two previous forms.<sup><a href="#note170"><b>170)</b></a></sup> The method by which a sequence of preprocessing tokens
8896 between a < and a > preprocessing token pair or a pair of " characters is combined into a
8897 single header name preprocessing token is implementation-defined.
8899 The implementation shall provide unique mappings for sequences consisting of one or
8900 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
8901 first character shall not be a digit. The implementation may ignore distinctions of
8902 alphabetical case and restrict the mapping to eight significant characters before the
8903 period.
8905 A #include preprocessing directive may appear in a source file that has been read
8906 because of a #include directive in another file, up to an implementation-defined
8909 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
8910 <pre>
8912 #include "myprog.h"
8913 </pre>
8918 <!--page 183 -->
8920 EXAMPLE 2 This illustrates macro-replaced #include directives:
8921 <pre>
8922 #if VERSION == 1
8923 #define INCFILE "vers1.h"
8924 #elif VERSION == 2
8925 #define INCFILE "vers2.h" // and so on
8926 #else
8927 #define INCFILE "versN.h"
8928 #endif
8929 #include INCFILE
8930 </pre>
8935 <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
8936 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.
8937 </small>
8942 Two replacement lists are identical if and only if the preprocessing tokens in both have
8943 the same number, ordering, spelling, and white-space separation, where all white-space
8944 separations are considered identical.
8946 An identifier currently defined as an object-like macro shall not be redefined by another
8947 #define preprocessing directive unless the second definition is an object-like macro
8948 definition and the two replacement lists are identical. Likewise, an identifier currently
8949 defined as a function-like macro shall not be redefined by another #define
8950 preprocessing directive unless the second definition is a function-like macro definition
8951 that has the same number and spelling of parameters, and the two replacement lists are
8952 identical.
8954 There shall be white-space between the identifier and the replacement list in the definition
8955 of an object-like macro.
8957 If the identifier-list in the macro definition does not end with an ellipsis, the number of
8958 arguments (including those arguments consisting of no preprocessing tokens) in an
8959 invocation of a function-like macro shall equal the number of parameters in the macro
8960 definition. Otherwise, there shall be more arguments in the invocation than there are
8961 parameters in the macro definition (excluding the ...). There shall exist a )
8962 preprocessing token that terminates the invocation.
8964 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
8965 macro that uses the ellipsis notation in the parameters.
8967 A parameter identifier in a function-like macro shall be uniquely declared within its
8968 scope.
8971 The identifier immediately following the define is called the macro name. There is one
8972 name space for macro names. Any white-space characters preceding or following the
8973 replacement list of preprocessing tokens are not considered part of the replacement list
8974 <!--page 184 -->
8975 for either form of macro.
8977 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
8978 a preprocessing directive could begin, the identifier is not subject to macro replacement.
8980 A preprocessing directive of the form
8981 <pre>
8982 # define identifier replacement-list new-line
8983 </pre>
8984 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note171"><b>171)</b></a></sup>
8985 to be replaced by the replacement list of preprocessing tokens that constitute the
8986 remainder of the directive. The replacement list is then rescanned for more macro names
8987 as specified below.
8989 A preprocessing directive of the form
8990 <pre>
8992 # define identifier lparen ... ) replacement-list new-line
8993 # define identifier lparen identifier-list , ... ) replacement-list new-line
8994 </pre>
8995 defines a function-like macro with parameters, whose use is similar syntactically to a
8996 function call. The parameters are specified by the optional list of identifiers, whose scope
8997 extends from their declaration in the identifier list until the new-line character that
8998 terminates the #define preprocessing directive. Each subsequent instance of the
8999 function-like macro name followed by a ( as the next preprocessing token introduces the
9000 sequence of preprocessing tokens that is replaced by the replacement list in the definition
9001 (an invocation of the macro). The replaced sequence of preprocessing tokens is
9002 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
9003 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
9004 tokens making up an invocation of a function-like macro, new-line is considered a normal
9005 white-space character.
9007 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
9008 forms the list of arguments for the function-like macro. The individual arguments within
9009 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
9010 between matching inner parentheses do not separate arguments. If there are sequences of
9011 preprocessing tokens within the list of arguments that would otherwise act as
9012 preprocessing directives,<sup><a href="#note172"><b>172)</b></a></sup> the behavior is undefined.
9014 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
9015 including any separating comma preprocessing tokens, are merged to form a single item:
9018 <!--page 185 -->
9019 the variable arguments. The number of arguments so combined is such that, following
9020 merger, the number of arguments is one more than the number of parameters in the macro
9021 definition (excluding the ...).
9024 <p><small><a name="note171" href="#note171">171)</a> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
9025 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
9026 are never scanned for macro names or parameters.
9027 </small>
9028 <p><small><a name="note172" href="#note172">172)</a> Despite the name, a non-directive is a preprocessing directive.
9029 </small>
9033 After the arguments for the invocation of a function-like macro have been identified,
9034 argument substitution takes place. A parameter in the replacement list, unless preceded
9035 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
9036 replaced by the corresponding argument after all macros contained therein have been
9037 expanded. Before being substituted, each argument's preprocessing tokens are
9038 completely macro replaced as if they formed the rest of the preprocessing file; no other
9039 preprocessing tokens are available.
9041 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
9042 were a parameter, and the variable arguments shall form the preprocessing tokens used to
9043 replace it.
9048 Each # preprocessing token in the replacement list for a function-like macro shall be
9049 followed by a parameter as the next preprocessing token in the replacement list.
9052 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
9053 token, both are replaced by a single character string literal preprocessing token that
9054 contains the spelling of the preprocessing token sequence for the corresponding
9055 argument. Each occurrence of white space between the argument's preprocessing tokens
9056 becomes a single space character in the character string literal. White space before the
9057 first preprocessing token and after the last preprocessing token composing the argument
9058 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
9059 is retained in the character string literal, except for special handling for producing the
9060 spelling of string literals and character constants: a \ character is inserted before each "
9061 and \ character of a character constant or string literal (including the delimiting "
9062 characters), except that it is implementation-defined whether a \ character is inserted
9063 before the \ character beginning a universal character name. If the replacement that
9064 results is not a valid character string literal, the behavior is undefined. The character
9065 string literal corresponding to an empty argument is "". The order of evaluation of # and
9066 ## operators is unspecified.
9067 <!--page 186 -->
9072 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
9073 list for either form of macro definition.
9076 If, in the replacement list of a function-like macro, a parameter is immediately preceded
9077 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
9078 argument's preprocessing token sequence; however, if an argument consists of no
9079 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
9082 For both object-like and function-like macro invocations, before the replacement list is
9083 reexamined for more macro names to replace, each instance of a ## preprocessing token
9084 in the replacement list (not from an argument) is deleted and the preceding preprocessing
9085 token is concatenated with the following preprocessing token. Placemarker
9086 preprocessing tokens are handled specially: concatenation of two placemarkers results in
9087 a single placemarker preprocessing token, and concatenation of a placemarker with a
9088 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
9089 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
9090 token is available for further macro replacement. The order of evaluation of ## operators
9091 is unspecified.
9093 EXAMPLE In the following fragment:
9094 <pre>
9095 #define hash_hash # ## #
9096 #define mkstr(a) # a
9097 #define in_between(a) mkstr(a)
9098 #define join(c, d) in_between(c hash_hash d)
9099 char p[] = join(x, y); // equivalent to
9100 // char p[] = "x ## y";
9101 </pre>
9102 The expansion produces, at various stages:
9103 <pre>
9104 join(x, y)
9105 in_between(x hash_hash y)
9106 in_between(x ## y)
9107 mkstr(x ## y)
9108 "x ## y"
9109 </pre>
9110 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
9111 this new token is not the ## operator.
9114 <!--page 187 -->
9117 <p><small><a name="note173" href="#note173">173)</a> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
9118 exist only within translation phase 4.
9119 </small>
9123 After all parameters in the replacement list have been substituted and # and ##
9124 processing has taken place, all placemarker preprocessing tokens are removed. The
9125 resulting preprocessing token sequence is then rescanned, along with all subsequent
9126 preprocessing tokens of the source file, for more macro names to replace.
9128 If the name of the macro being replaced is found during this scan of the replacement list
9129 (not including the rest of the source file's preprocessing tokens), it is not replaced.
9130 Furthermore, if any nested replacements encounter the name of the macro being replaced,
9131 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
9132 available for further replacement even if they are later (re)examined in contexts in which
9133 that macro name preprocessing token would otherwise have been replaced.
9135 The resulting completely macro-replaced preprocessing token sequence is not processed
9136 as a preprocessing directive even if it resembles one, but all pragma unary operator
9141 A macro definition lasts (independent of block structure) until a corresponding #undef
9142 directive is encountered or (if none is encountered) until the end of the preprocessing
9143 translation unit. Macro definitions have no significance after translation phase 4.
9145 A preprocessing directive of the form
9146 <pre>
9147 # undef identifier new-line
9148 </pre>
9149 causes the specified identifier no longer to be defined as a macro name. It is ignored if
9150 the specified identifier is not currently defined as a macro name.
9152 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
9153 <pre>
9154 #define TABSIZE 100
9155 int table[TABSIZE];
9156 </pre>
9159 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
9160 It has the advantages of working for any compatible types of the arguments and of generating in-line code
9161 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
9162 arguments a second time (including side effects) and generating more code than a function if invoked
9163 several times. It also cannot have its address taken, as it has none.
9164 <pre>
9165 #define max(a, b) ((a) > (b) ? (a) : (b))
9166 </pre>
9167 The parentheses ensure that the arguments and the resulting expression are bound properly.
9168 <!--page 188 -->
9170 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
9171 <pre>
9172 #define x 3
9173 #define f(a) f(x * (a))
9174 #undef x
9175 #define x 2
9176 #define g f
9177 #define z z[0]
9178 #define h g(~
9179 #define m(a) a(w)
9181 #define t(a) a
9182 #define p() int
9183 #define q(x) x
9184 #define r(x,y) x ## y
9185 #define str(x) # x
9188 (f)^m(m);
9191 </pre>
9192 results in
9193 <pre>
9198 </pre>
9201 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
9202 sequence
9203 <pre>
9204 #define str(s) # s
9205 #define xstr(s) str(s)
9207 x ## s, x ## t)
9208 #define INCFILE(n) vers ## n
9209 #define glue(a, b) a ## b
9210 #define xglue(a, b) glue(a, b)
9211 #define HIGHLOW "hello"
9212 #define LOW LOW ", world"
9215 == 0) str(: @\n), s);
9216 #include xstr(INCFILE(2).h)
9217 glue(HIGH, LOW);
9218 xglue(HIGH, LOW)
9219 </pre>
9220 results in
9221 <!--page 189 -->
9222 <pre>
9224 fputs(
9226 s);
9227 #include "vers2.h" (after macro replacement, before file access)
9228 "hello";
9230 </pre>
9231 or, after concatenation of the character string literals,
9232 <pre>
9233 printf("x1= %d, x2= %s", x1, x2);
9234 fputs(
9236 s);
9237 #include "vers2.h" (after macro replacement, before file access)
9238 "hello";
9239 "hello, world"
9240 </pre>
9241 Space around the # and ## tokens in the macro definition is optional.
9244 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
9245 <pre>
9246 #define t(x,y,z) x ## y ## z
9249 </pre>
9250 results in
9251 <pre>
9254 </pre>
9257 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
9258 <pre>
9261 #define FUNC_LIKE(a) ( a )
9262 #define FUNC_LIKE( a )( /* note the white space */ \
9263 a /* other stuff on this line
9264 */ )
9265 </pre>
9266 But the following redefinitions are invalid:
9267 <pre>
9268 #define OBJ_LIKE (0) // different token sequence
9270 #define FUNC_LIKE(b) ( a ) // different parameter usage
9271 #define FUNC_LIKE(b) ( b ) // different parameter spelling
9272 </pre>
9275 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
9276 <!--page 190 -->
9277 <pre>
9278 #define debug(...) fprintf(stderr, __VA_ARGS__)
9279 #define showlist(...) puts(#__VA_ARGS__)
9280 #define report(test, ...) ((test)?puts(#test):\
9281 printf(__VA_ARGS__))
9282 debug("Flag");
9283 debug("X = %d\n", x);
9284 showlist(The first, second, and third items.);
9286 </pre>
9287 results in
9288 <pre>
9289 fprintf(stderr, "Flag" );
9290 fprintf(stderr, "X = %d\n", x );
9291 puts( "The first, second, and third items." );
9293 printf("x is %d but y is %d", x, y));
9294 </pre>
9300 The string literal of a #line directive, if present, shall be a character string literal.
9303 The line number of the current source line is one greater than the number of new-line
9304 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
9305 file to the current token.
9307 A preprocessing directive of the form
9308 <pre>
9309 # line digit-sequence new-line
9310 </pre>
9311 causes the implementation to behave as if the following sequence of source lines begins
9312 with a source line that has a line number as specified by the digit sequence (interpreted as
9313 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
9314 2147483647.
9316 A preprocessing directive of the form
9317 <pre>
9318 # line digit-sequence "s-char-sequence<sub>opt</sub>" new-line
9319 </pre>
9320 sets the presumed line number similarly and changes the presumed name of the source
9321 file to be the contents of the character string literal.
9323 A preprocessing directive of the form
9324 <pre>
9325 # line pp-tokens new-line
9326 </pre>
9327 (that does not match one of the two previous forms) is permitted. The preprocessing
9328 tokens after line on the directive are processed just as in normal text (each identifier
9329 currently defined as a macro name is replaced by its replacement list of preprocessing
9330 tokens). The directive resulting after all replacements shall match one of the two
9331 previous forms and is then processed as appropriate.
9332 <!--page 191 -->
9337 A preprocessing directive of the form
9338 <pre>
9340 </pre>
9341 causes the implementation to produce a diagnostic message that includes the specified
9342 sequence of preprocessing tokens.
9347 A preprocessing directive of the form
9348 <pre>
9350 </pre>
9351 where the preprocessing token STDC does not immediately follow pragma in the
9352 directive (prior to any macro replacement)<sup><a href="#note174"><b>174)</b></a></sup> causes the implementation to behave in an
9353 implementation-defined manner. The behavior might cause translation to fail or cause the
9354 translator or the resulting program to behave in a non-conforming manner. Any such
9355 pragma that is not recognized by the implementation is ignored.
9357 If the preprocessing token STDC does immediately follow pragma in the directive (prior
9358 to any macro replacement), then no macro replacement is performed on the directive, and
9359 the directive shall have one of the following forms<sup><a href="#note175"><b>175)</b></a></sup> whose meanings are described
9360 elsewhere:
9361 <pre>
9362 #pragma STDC FP_CONTRACT on-off-switch
9363 #pragma STDC FENV_ACCESS on-off-switch
9364 #pragma STDC CX_LIMITED_RANGE on-off-switch
9365 on-off-switch: one of
9366 ON OFF DEFAULT
9367 </pre>
9368 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
9374 <!--page 192 -->
9377 <p><small><a name="note174" href="#note174">174)</a> An implementation is not required to perform macro replacement in pragmas, but it is permitted
9378 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
9379 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
9380 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
9381 but is not required to.
9382 </small>
9383 <p><small><a name="note175" href="#note175">175)</a> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
9384 </small>
9389 A preprocessing directive of the form
9390 <pre>
9391 # new-line
9392 </pre>
9393 has no effect.
9397 The values of the predefined macros listed in the following subclauses<sup><a href="#note176"><b>176)</b></a></sup> (except for
9398 __FILE__ and __LINE__) remain constant throughout the translation unit.
9400 None of these macro names, nor the identifier defined, shall be the subject of a
9401 #define or a #undef preprocessing directive. Any other predefined macro names
9402 shall begin with a leading underscore followed by an uppercase letter or a second
9403 underscore.
9405 The implementation shall not predefine the macro __cplusplus, nor shall it define it
9406 in any standard header.
9410 <p><small><a name="note176" href="#note176">176)</a> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
9411 </small>
9415 The following macro names shall be defined by the implementation:
9416 __DATE__ The date of translation of the preprocessing translation unit: a character
9417 <pre>
9418 string literal of the form "Mmm dd yyyy", where the names of the
9419 months are the same as those generated by the asctime function, and the
9420 first character of dd is a space character if the value is less than 10. If the
9421 date of translation is not available, an implementation-defined valid date
9422 shall be supplied.
9423 </pre>
9424 __FILE__ The presumed name of the current source file (a character string literal).<sup><a href="#note177"><b>177)</b></a></sup>
9425 __LINE__ The presumed line number (within the current source file) of the current
9426 <pre>
9428 </pre>
9429 __STDC__ The integer constant 1, intended to indicate a conforming implementation.
9430 __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
9431 <pre>
9432 implementation or the integer constant 0 if it is not.
9433 </pre>
9438 <!--page 193 -->
9440 __TIME__ The time of translation of the preprocessing translation unit: a character
9441 <pre>
9442 string literal of the form "hh:mm:ss" as in the time generated by the
9443 asctime function. If the time of translation is not available, an
9444 implementation-defined valid time shall be supplied.
9445 </pre>
9449 <p><small><a name="note177" href="#note177">177)</a> The presumed source file name and line number can be changed by the #line directive.
9450 </small>
9451 <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
9453 remain an integer constant of type long int that is increased with each revision of this International
9454 Standard.
9455 </small>
9459 The following macro names are conditionally defined by the implementation:
9460 __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
9461 <pre>
9462 199712L). If this symbol is defined, then every character in the Unicode
9463 required set, when stored in an object of type wchar_t, has the same
9464 value as the short identifier of that character. The Unicode required set
9465 consists of all the characters that are defined by ISO/IEC 10646, along with
9466 all amendments and technical corrigenda, as of the specified year and
9467 month. If some other encoding is used, the macro shall not be defined and
9468 the actual encoding used is implementation-defined.
9469 </pre>
9470 __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
9471 <pre>
9472 the encoding for wchar_t, a member of the basic character set need not
9473 have a code value equal to its value when used as the lone character in an
9474 integer character constant.
9475 </pre>
9476 __STDC_UTF_16__ The integer constant 1, intended to indicate that values of type
9477 <pre>
9478 char16_t are UTF-16 encoded. If some other encoding is used, the
9479 macro shall not be defined and the actual encoding used is implementation-
9480 defined.
9481 </pre>
9482 __STDC_UTF_32__ The integer constant 1, intended to indicate that values of type
9483 <pre>
9484 char32_t are UTF-32 encoded. If some other encoding is used, the
9485 macro shall not be defined and the actual encoding used is implementation-
9486 defined.
9487 </pre>
9488 <p><b> Forward references</b>: common definitions (<a href="#7.19">7.19</a>), unicode utilities (<a href="#7.27">7.27</a>).
9493 <!--page 194 -->
9497 The following macro names are conditionally defined by the implementation:
9498 __STDC_ANALYZABLE__ The integer constant 1, intended to indicate conformance to
9499 <pre>
9501 </pre>
9502 __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
9503 <pre>
9505 </pre>
9506 __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
9507 <pre>
9509 arithmetic).
9510 </pre>
9511 __STDC_LIB_EXT1__ The integer constant 201ymmL, intended to indicate support
9512 <pre>
9513 for the extensions defined in <a href="#K">annex K</a> (Bounds-checking interfaces).<sup><a href="#note179"><b>179)</b></a></sup>
9514 </pre>
9515 __STDC_NO_COMPLEX__ The integer constant 1, intended to indicate that the
9516 <pre>
9518 header.
9519 </pre>
9520 __STDC_NO_THREADS__ The integer constant 1, intended to indicate that the
9521 <pre>
9522 implementation does not support atomic types (including the _Atomic
9523 type qualifier and the <a href="#7.17"><stdatomic.h></a> header) or the <a href="#7.25"><threads.h></a>
9524 header.
9525 </pre>
9526 __STDC_NO_VLA__ The integer constant 1, intended to indicate that the
9527 <pre>
9528 implementation does not support variable length arrays or variably
9529 modified types.
9530 </pre>
9532 An implementation that defines __STDC_NO_COMPLEX__ shall not define
9533 __STDC_IEC_559_COMPLEX__.
9536 <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
9537 each revision of this International Standard.
9538 </small>
9543 A unary operator expression of the form:
9544 <pre>
9545 _Pragma ( string-literal )
9546 </pre>
9547 is processed as follows: The string literal is destringized by deleting the L prefix, if
9548 present, deleting the leading and trailing double-quotes, replacing each escape sequence
9549 \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
9550 resulting sequence of characters is processed through translation phase 3 to produce
9551 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
9554 <!--page 195 -->
9555 directive. The original four preprocessing tokens in the unary operator expression are
9556 removed.
9557 <p><!--para 2 -->
9558 EXAMPLE A directive of the form:
9559 <pre>
9561 </pre>
9562 can also be expressed as:
9563 <pre>
9565 </pre>
9566 The latter form is processed in the same way whether it appears literally as shown, or results from macro
9567 replacement, as in:
9568 <!--page 196 -->
9569 <pre>
9570 #define LISTING(x) PRAGMA(listing on #x)
9571 #define PRAGMA(x) _Pragma(#x)
9572 LISTING ( ..\listing.dir )
9573 </pre>
9578 <p><!--para 1 -->
9579 Future standardization may include additional floating-point types, including those with
9580 greater range, precision, or both than long double.
9583 <p><!--para 1 -->
9584 Declaring an identifier with internal linkage at file scope without the static storage-
9585 class specifier is an obsolescent feature.
9588 <p><!--para 1 -->
9589 Restriction of the significance of an external name to fewer than 255 characters
9590 (considering each universal character name or extended source character as a single
9591 character) is an obsolescent feature that is a concession to existing implementations.
9594 <p><!--para 1 -->
9595 Lowercase letters as escape sequences are reserved for future standardization. Other
9596 characters may be used in extensions.
9599 <p><!--para 1 -->
9600 The placement of a storage-class specifier other than at the beginning of the declaration
9601 specifiers in a declaration is an obsolescent feature.
9604 <p><!--para 1 -->
9605 The use of function declarators with empty parentheses (not prototype-format parameter
9606 type declarators) is an obsolescent feature.
9609 <p><!--para 1 -->
9610 The use of function definitions with separate parameter identifier and declaration lists
9611 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
9614 <p><!--para 1 -->
9615 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
9618 <p><!--para 1 -->
9619 Macro names beginning with __STDC_ are reserved for future standardization.
9620 <!--page 197 -->
9627 <p><!--para 1 -->
9628 A string is a contiguous sequence of characters terminated by and including the first null
9629 character. The term multibyte string is sometimes used instead to emphasize special
9630 processing given to multibyte characters contained in the string or to avoid confusion
9631 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
9632 character. The length of a string is the number of bytes preceding the null character and
9633 the value of a string is the sequence of the values of the contained characters, in order.
9634 <p><!--para 2 -->
9635 The decimal-point character is the character used by functions that convert floating-point
9636 numbers to or from character sequences to denote the beginning of the fractional part of
9637 such character sequences.<sup><a href="#note180"><b>180)</b></a></sup> It is represented in the text and examples by a period, but
9638 may be changed by the setlocale function.
9639 <p><!--para 3 -->
9640 A null wide character is a wide character with code value zero.
9641 <p><!--para 4 -->
9642 A wide string is a contiguous sequence of wide characters terminated by and including
9643 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
9644 addressed) wide character. The length of a wide string is the number of wide characters
9645 preceding the null wide character and the value of a wide string is the sequence of code
9646 values of the contained wide characters, in order.
9647 <p><!--para 5 -->
9648 A shift sequence is a contiguous sequence of bytes within a multibyte string that
9649 (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
9650 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
9652 <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>).
9657 <!--page 198 -->
9659 <p><b>Footnotes</b>
9660 <p><small><a name="note180" href="#note180">180)</a> The functions that make use of the decimal-point character are the numeric conversion functions
9661 (<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>).
9662 </small>
9663 <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
9664 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
9665 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
9666 implementation's choice.
9667 </small>
9670 <p><!--para 1 -->
9671 Each library function is declared, with a type that includes a prototype, in a header,<sup><a href="#note182"><b>182)</b></a></sup>
9672 whose contents are made available by the #include preprocessing directive. The
9673 header declares a set of related functions, plus any necessary types and additional macros
9674 needed to facilitate their use. Declarations of types described in this clause shall not
9675 include type qualifiers, unless explicitly stated otherwise.
9676 <p><!--para 2 -->
9678 <pre>
9679 <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>
9680 <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>
9681 <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>
9682 <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>
9683 <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>
9684 <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>
9685 <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>
9686 </pre>
9687 <p><!--para 3 -->
9688 If a file with the same name as one of the above < and > delimited sequences, not
9689 provided as part of the implementation, is placed in any of the standard places that are
9690 searched for included source files, the behavior is undefined.
9691 <p><!--para 4 -->
9692 Standard headers may be included in any order; each may be included more than once in
9693 a given scope, with no effect different from being included only once, except that the
9694 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
9695 used, a header shall be included outside of any external declaration or definition, and it
9696 shall first be included before the first reference to any of the functions or objects it
9697 declares, or to any of the types or macros it defines. However, if an identifier is declared
9698 or defined in more than one header, the second and subsequent associated headers may be
9699 included after the initial reference to the identifier. The program shall not have any
9700 macros with names lexically identical to keywords currently defined prior to the
9701 inclusion.
9702 <p><!--para 5 -->
9703 Any definition of an object-like macro described in this clause shall expand to code that is
9704 fully protected by parentheses where necessary, so that it groups in an arbitrary
9705 expression as if it were a single identifier.
9706 <p><!--para 6 -->
9707 Any declaration of a library function shall have external linkage.
9712 <!--page 199 -->
9713 <p><!--para 7 -->
9717 <p><b>Footnotes</b>
9718 <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
9719 necessarily valid source file names.
9720 </small>
9721 <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
9723 </small>
9726 <p><!--para 1 -->
9727 Each header declares or defines all identifiers listed in its associated subclause, and
9728 optionally declares or defines identifiers listed in its associated future library directions
9729 subclause and identifiers which are always reserved either for any use or for use as file
9730 scope identifiers.
9731 <ul>
9732 <li> All identifiers that begin with an underscore and either an uppercase letter or another
9733 underscore are always reserved for any use.
9734 <li> All identifiers that begin with an underscore are always reserved for use as identifiers
9735 with file scope in both the ordinary and tag name spaces.
9736 <li> Each macro name in any of the following subclauses (including the future library
9737 directions) is reserved for use as specified if any of its associated headers is included;
9739 <li> All identifiers with external linkage in any of the following subclauses (including the
9740 future library directions) and errno are always reserved for use as identifiers with
9742 <li> Each identifier with file scope listed in any of the following subclauses (including the
9743 future library directions) is reserved for use as a macro name and as an identifier with
9744 file scope in the same name space if any of its associated headers is included.
9745 </ul>
9746 <p><!--para 2 -->
9747 No other identifiers are reserved. If the program declares or defines an identifier in a
9748 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
9749 identifier as a macro name, the behavior is undefined.
9750 <p><!--para 3 -->
9751 If the program removes (with #undef) any macro definition of an identifier in the first
9752 group listed above, the behavior is undefined.
9757 <!--page 200 -->
9759 <p><b>Footnotes</b>
9760 <p><small><a name="note184" href="#note184">184)</a> The list of reserved identifiers with external linkage includes math_errhandling, setjmp,
9761 va_copy, and va_end.
9762 </small>
9765 <p><!--para 1 -->
9766 Each of the following statements applies unless explicitly stated otherwise in the detailed
9767 descriptions that follow: If an argument to a function has an invalid value (such as a value
9768 outside the domain of the function, or a pointer outside the address space of the program,
9769 or a null pointer, or a pointer to non-modifiable storage when the corresponding
9770 parameter is not const-qualified) or a type (after promotion) not expected by a function
9771 with variable number of arguments, the behavior is undefined. If a function argument is
9772 described as being an array, the pointer actually passed to the function shall have a value
9773 such that all address computations and accesses to objects (that would be valid if the
9774 pointer did point to the first element of such an array) are in fact valid. Any function
9775 declared in a header may be additionally implemented as a function-like macro defined in
9776 the header, so if a library function is declared explicitly when its header is included, one
9777 of the techniques shown below can be used to ensure the declaration is not affected by
9778 such a macro. Any macro definition of a function can be suppressed locally by enclosing
9779 the name of the function in parentheses, because the name is then not followed by the left
9780 parenthesis that indicates expansion of a macro function name. For the same syntactic
9781 reason, it is permitted to take the address of a library function even if it is also defined as
9782 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
9783 actual function is referred to. Any invocation of a library function that is implemented as
9784 a macro shall expand to code that evaluates each of its arguments exactly once, fully
9785 protected by parentheses where necessary, so it is generally safe to use arbitrary
9786 expressions as arguments.<sup><a href="#note186"><b>186)</b></a></sup> Likewise, those function-like macros described in the
9787 following subclauses may be invoked in an expression anywhere a function with a
9788 compatible return type could be called.<sup><a href="#note187"><b>187)</b></a></sup> All object-like macros listed as expanding to
9791 <!--page 201 -->
9792 integer constant expressions shall additionally be suitable for use in #if preprocessing
9793 directives.
9794 <p><!--para 2 -->
9795 Provided that a library function can be declared without reference to any type defined in a
9796 header, it is also permissible to declare the function and use it without including its
9797 associated header.
9798 <p><!--para 3 -->
9799 There is a sequence point immediately before a library function returns.
9800 <p><!--para 4 -->
9801 The functions in the standard library are not guaranteed to be reentrant and may modify
9803 <p><!--para 5 -->
9804 Unless explicitly stated otherwise in the detailed descriptions that follow, library
9805 functions shall prevent data races as follows: A library function shall not directly or
9806 indirectly access objects accessible by threads other than the current thread unless the
9807 objects are accessed directly or indirectly via the function's arguments. A library
9808 function shall not directly or indirectly modify objects accessible by threads other than
9809 the current thread unless the objects are accessed directly or indirectly via the function's
9810 non-const arguments.<sup><a href="#note189"><b>189)</b></a></sup> Implementations may share their own internal objects between
9811 threads if the objects are not visible to users and are protected against data races.
9812 <p><!--para 6 -->
9813 Unless otherwise specified, library functions shall perform all operations solely within the
9814 current thread if those operations have effects that are visible to users.<sup><a href="#note190"><b>190)</b></a></sup>
9815 <p><!--para 7 -->
9816 EXAMPLE The function atoi may be used in any of several ways:
9817 <ul>
9818 <li> by use of its associated header (possibly generating a macro expansion)
9819 <pre>
9821 const char *str;
9822 /* ... */
9823 i = atoi(str);
9824 </pre>
9825 <li> by use of its associated header (assuredly generating a true function reference)
9830 <!--page 202 -->
9831 <pre>
9833 #undef atoi
9834 const char *str;
9835 /* ... */
9836 i = atoi(str);
9837 </pre>
9838 or
9839 <pre>
9841 const char *str;
9842 /* ... */
9843 i = (atoi)(str);
9844 </pre>
9845 <li> by explicit declaration
9846 <!--page 203 -->
9847 <pre>
9848 extern int atoi(const char *);
9849 const char *str;
9850 /* ... */
9851 i = atoi(str);
9852 </pre>
9853 </ul>
9855 <p><b>Footnotes</b>
9856 <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
9857 also provides a macro for that function.
9858 </small>
9859 <p><small><a name="note186" href="#note186">186)</a> Such macros might not contain the sequence points that the corresponding function calls do.
9860 </small>
9861 <p><small><a name="note187" href="#note187">187)</a> Because external identifiers and some macro names beginning with an underscore are reserved,
9862 implementations may provide special semantics for such names. For example, the identifier
9863 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
9864 appropriate header could specify
9866 <pre>
9867 #define abs(x) _BUILTIN_abs(x)
9868 </pre>
9869 for a compiler whose code generator will accept it.
9870 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
9871 function may write
9873 <pre>
9874 #undef abs
9875 </pre>
9876 whether the implementation's header provides a macro implementation of abs or a built-in
9877 implementation. The prototype for the function, which precedes and is hidden by any macro
9878 definition, is thereby revealed also.
9879 </small>
9880 <p><small><a name="note188" href="#note188">188)</a> Thus, a signal handler cannot, in general, call standard library functions.
9881 </small>
9882 <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
9883 purposes without synchronization because it could cause a data race even in programs that do not
9884 explicitly share objects between threads.
9885 </small>
9886 <p><small><a name="note190" href="#note190">190)</a> This allows implementations to parallelize operations if there are no visible side effects.
9887 </small>
9890 <p><!--para 1 -->
9892 refers to another macro,
9893 <pre>
9894 NDEBUG
9895 </pre>
9896 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
9897 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
9898 simply as
9899 <pre>
9900 #define assert(ignore) ((void)0)
9901 </pre>
9902 The assert macro is redefined according to the current state of NDEBUG each time that
9904 <p><!--para 2 -->
9905 The assert macro shall be implemented as a macro, not as an actual function. If the
9906 macro definition is suppressed in order to access an actual function, the behavior is
9907 undefined.
9908 <p><!--para 3 -->
9909 The macro
9910 <pre>
9911 static_assert
9912 </pre>
9913 expands to _Static_assert.
9918 <p><b>Synopsis</b>
9919 <p><!--para 1 -->
9920 <pre>
9922 void assert(scalar expression);
9923 </pre>
9924 <p><b>Description</b>
9925 <p><!--para 2 -->
9926 The assert macro puts diagnostic tests into programs; it expands to a void expression.
9927 When it is executed, if expression (which shall have a scalar type) is false (that is,
9928 compares equal to 0), the assert macro writes information about the particular call that
9929 failed (including the text of the argument, the name of the source file, the source line
9930 number, and the name of the enclosing function -- the latter are respectively the values of
9931 the preprocessing macros __FILE__ and __LINE__ and of the identifier
9932 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note191"><b>191)</b></a></sup> It
9933 then calls the abort function.
9937 <!--page 204 -->
9938 <p><b>Returns</b>
9939 <p><!--para 3 -->
9940 The assert macro returns no value.
9942 <!--page 205 -->
9944 <p><b>Footnotes</b>
9946 Assertion failed: expression, function abc, file xyz, line nnn.
9947 </small>
9952 <p><!--para 1 -->
9953 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
9955 <p><!--para 2 -->
9956 Implementations that define the macro __STDC_NO_COMPLEX__ need not provide
9957 this header nor support any of its facilities.
9958 <p><!--para 3 -->
9959 Each synopsis specifies a family of functions consisting of a principal function with one
9960 or more double complex parameters and a double complex or double return
9961 value; and other functions with the same name but with f and l suffixes which are
9962 corresponding functions with float and long double parameters and return values.
9963 <p><!--para 4 -->
9964 The macro
9965 <pre>
9966 complex
9967 </pre>
9968 expands to _Complex; the macro
9969 <pre>
9970 _Complex_I
9971 </pre>
9972 expands to a constant expression of type const float _Complex, with the value of
9974 <p><!--para 5 -->
9975 The macros
9976 <pre>
9977 imaginary
9978 </pre>
9979 and
9980 <pre>
9981 _Imaginary_I
9982 </pre>
9983 are defined if and only if the implementation supports imaginary types;<sup><a href="#note194"><b>194)</b></a></sup> if defined,
9984 they expand to _Imaginary and a constant expression of type const float
9985 _Imaginary with the value of the imaginary unit.
9986 <p><!--para 6 -->
9987 The macro
9988 <pre>
9989 I
9990 </pre>
9991 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
9992 defined, I shall expand to _Complex_I.
9993 <p><!--para 7 -->
9994 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
9995 redefine the macros complex, imaginary, and I.
9997 <!--page 206 -->
9998 <p><b> Forward references</b>: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
10000 <p><b>Footnotes</b>
10001 <p><small><a name="note192" href="#note192">192)</a> See ''future library directions'' (<a href="#7.30.1">7.30.1</a>).
10002 </small>
10003 <p><small><a name="note193" href="#note193">193)</a> The imaginary unit is a number i such that i 2 = -1.
10004 </small>
10005 <p><small><a name="note194" href="#note194">194)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
10006 </small>
10009 <p><!--para 1 -->
10010 Values are interpreted as radians, not degrees. An implementation may set errno but is
10011 not required to.
10014 <p><!--para 1 -->
10015 Some of the functions below have branch cuts, across which the function is
10016 discontinuous. For implementations with a signed zero (including all IEC 60559
10017 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
10018 one side of a cut from another so the function is continuous (except for format
10019 limitations) as the cut is approached from either side. For example, for the square root
10020 function, which has a branch cut along the negative real axis, the top of the cut, with
10021 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
10022 imaginary part -0, maps to the negative imaginary axis.
10023 <p><!--para 2 -->
10024 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
10025 sides of branch cuts. These implementations shall map a cut so the function is continuous
10026 as the cut is approached coming around the finite endpoint of the cut in a counter
10027 clockwise direction. (Branch cuts for the functions specified here have just one finite
10028 endpoint.) For example, for the square root function, coming counter clockwise around
10029 the finite endpoint of the cut along the negative real axis approaches the cut from above,
10030 so the cut maps to the positive imaginary axis.
10033 <p><b>Synopsis</b>
10034 <p><!--para 1 -->
10035 <pre>
10037 #pragma STDC CX_LIMITED_RANGE on-off-switch
10038 </pre>
10039 <p><b>Description</b>
10040 <p><!--para 2 -->
10041 The usual mathematical formulas for complex multiply, divide, and absolute value are
10042 problematic because of their treatment of infinities and because of undue overflow and
10043 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
10044 implementation that (where the state is ''on'') the usual mathematical formulas are
10045 acceptable.<sup><a href="#note195"><b>195)</b></a></sup> The pragma can occur either outside external declarations or preceding all
10046 explicit declarations and statements inside a compound statement. When outside external
10047 declarations, the pragma takes effect from its occurrence until another
10048 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
10049 When inside a compound statement, the pragma takes effect from its occurrence until
10050 another CX_LIMITED_RANGE pragma is encountered (including within a nested
10051 compound statement), or until the end of the compound statement; at the end of a
10052 compound statement the state for the pragma is restored to its condition just before the
10053 <!--page 207 -->
10054 compound statement. If this pragma is used in any other context, the behavior is
10055 undefined. The default state for the pragma is ''off''.
10057 <p><b>Footnotes</b>
10058 <p><small><a name="note195" href="#note195">195)</a> The purpose of the pragma is to allow the implementation to use the formulas:
10060 <pre>
10061 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
10062 (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
10063 | x + iy | = (sqrt) x 2 + y 2
10064 -----
10065 </pre>
10066 where the programmer can determine they are safe.
10067 </small>
10072 <p><b>Synopsis</b>
10073 <p><!--para 1 -->
10074 <pre>
10076 double complex cacos(double complex z);
10077 float complex cacosf(float complex z);
10078 long double complex cacosl(long double complex z);
10079 </pre>
10080 <p><b>Description</b>
10081 <p><!--para 2 -->
10082 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
10083 interval [-1, +1] along the real axis.
10084 <p><b>Returns</b>
10085 <p><!--para 3 -->
10086 The cacos functions return the complex arc cosine value, in the range of a strip
10087 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
10088 real axis.
10091 <p><b>Synopsis</b>
10092 <p><!--para 1 -->
10093 <pre>
10095 double complex casin(double complex z);
10096 float complex casinf(float complex z);
10097 long double complex casinl(long double complex z);
10098 </pre>
10099 <p><b>Description</b>
10100 <p><!--para 2 -->
10101 The casin functions compute the complex arc sine of z, with branch cuts outside the
10102 interval [-1, +1] along the real axis.
10103 <p><b>Returns</b>
10104 <p><!--para 3 -->
10105 The casin functions return the complex arc sine value, in the range of a strip
10106 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
10108 <!--page 208 -->
10109 along the real axis.
10112 <p><b>Synopsis</b>
10113 <p><!--para 1 -->
10114 <pre>
10116 double complex catan(double complex z);
10117 float complex catanf(float complex z);
10118 long double complex catanl(long double complex z);
10119 </pre>
10120 <p><b>Description</b>
10121 <p><!--para 2 -->
10122 The catan functions compute the complex arc tangent of z, with branch cuts outside the
10123 interval [-i, +i] along the imaginary axis.
10124 <p><b>Returns</b>
10125 <p><!--para 3 -->
10126 The catan functions return the complex arc tangent value, in the range of a strip
10127 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
10128 along the real axis.
10131 <p><b>Synopsis</b>
10132 <p><!--para 1 -->
10133 <pre>
10135 double complex ccos(double complex z);
10136 float complex ccosf(float complex z);
10137 long double complex ccosl(long double complex z);
10138 </pre>
10139 <p><b>Description</b>
10140 <p><!--para 2 -->
10141 The ccos functions compute the complex cosine of z.
10142 <p><b>Returns</b>
10143 <p><!--para 3 -->
10144 The ccos functions return the complex cosine value.
10147 <p><b>Synopsis</b>
10148 <p><!--para 1 -->
10149 <pre>
10151 double complex csin(double complex z);
10152 float complex csinf(float complex z);
10153 long double complex csinl(long double complex z);
10154 </pre>
10155 <p><b>Description</b>
10156 <p><!--para 2 -->
10157 The csin functions compute the complex sine of z.
10158 <!--page 209 -->
10159 <p><b>Returns</b>
10160 <p><!--para 3 -->
10161 The csin functions return the complex sine value.
10164 <p><b>Synopsis</b>
10165 <p><!--para 1 -->
10166 <pre>
10168 double complex ctan(double complex z);
10169 float complex ctanf(float complex z);
10170 long double complex ctanl(long double complex z);
10171 </pre>
10172 <p><b>Description</b>
10173 <p><!--para 2 -->
10174 The ctan functions compute the complex tangent of z.
10175 <p><b>Returns</b>
10176 <p><!--para 3 -->
10177 The ctan functions return the complex tangent value.
10182 <p><b>Synopsis</b>
10183 <p><!--para 1 -->
10184 <pre>
10186 double complex cacosh(double complex z);
10187 float complex cacoshf(float complex z);
10188 long double complex cacoshl(long double complex z);
10189 </pre>
10190 <p><b>Description</b>
10191 <p><!--para 2 -->
10192 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
10193 cut at values less than 1 along the real axis.
10194 <p><b>Returns</b>
10195 <p><!--para 3 -->
10196 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
10197 half-strip of nonnegative values along the real axis and in the interval [-ipi , +ipi ] along the
10198 imaginary axis.
10201 <p><b>Synopsis</b>
10202 <p><!--para 1 -->
10203 <!--page 210 -->
10204 <pre>
10206 double complex casinh(double complex z);
10207 float complex casinhf(float complex z);
10208 long double complex casinhl(long double complex z);
10209 </pre>
10210 <p><b>Description</b>
10211 <p><!--para 2 -->
10212 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
10213 outside the interval [-i, +i] along the imaginary axis.
10214 <p><b>Returns</b>
10215 <p><!--para 3 -->
10216 The casinh functions return the complex arc hyperbolic sine value, in the range of a
10217 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
10218 along the imaginary axis.
10221 <p><b>Synopsis</b>
10222 <p><!--para 1 -->
10223 <pre>
10225 double complex catanh(double complex z);
10226 float complex catanhf(float complex z);
10227 long double complex catanhl(long double complex z);
10228 </pre>
10229 <p><b>Description</b>
10230 <p><!--para 2 -->
10231 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
10232 cuts outside the interval [-1, +1] along the real axis.
10233 <p><b>Returns</b>
10234 <p><!--para 3 -->
10235 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
10236 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
10237 along the imaginary axis.
10240 <p><b>Synopsis</b>
10241 <p><!--para 1 -->
10242 <pre>
10244 double complex ccosh(double complex z);
10245 float complex ccoshf(float complex z);
10246 long double complex ccoshl(long double complex z);
10247 </pre>
10248 <p><b>Description</b>
10249 <p><!--para 2 -->
10250 The ccosh functions compute the complex hyperbolic cosine of z.
10251 <p><b>Returns</b>
10252 <p><!--para 3 -->
10253 The ccosh functions return the complex hyperbolic cosine value.
10254 <!--page 211 -->
10257 <p><b>Synopsis</b>
10258 <p><!--para 1 -->
10259 <pre>
10261 double complex csinh(double complex z);
10262 float complex csinhf(float complex z);
10263 long double complex csinhl(long double complex z);
10264 </pre>
10265 <p><b>Description</b>
10266 <p><!--para 2 -->
10267 The csinh functions compute the complex hyperbolic sine of z.
10268 <p><b>Returns</b>
10269 <p><!--para 3 -->
10270 The csinh functions return the complex hyperbolic sine value.
10273 <p><b>Synopsis</b>
10274 <p><!--para 1 -->
10275 <pre>
10277 double complex ctanh(double complex z);
10278 float complex ctanhf(float complex z);
10279 long double complex ctanhl(long double complex z);
10280 </pre>
10281 <p><b>Description</b>
10282 <p><!--para 2 -->
10283 The ctanh functions compute the complex hyperbolic tangent of z.
10284 <p><b>Returns</b>
10285 <p><!--para 3 -->
10286 The ctanh functions return the complex hyperbolic tangent value.
10291 <p><b>Synopsis</b>
10292 <p><!--para 1 -->
10293 <pre>
10295 double complex cexp(double complex z);
10296 float complex cexpf(float complex z);
10297 long double complex cexpl(long double complex z);
10298 </pre>
10299 <p><b>Description</b>
10300 <p><!--para 2 -->
10301 The cexp functions compute the complex base-e exponential of z.
10302 <p><b>Returns</b>
10303 <p><!--para 3 -->
10304 The cexp functions return the complex base-e exponential value.
10305 <!--page 212 -->
10308 <p><b>Synopsis</b>
10309 <p><!--para 1 -->
10310 <pre>
10312 double complex clog(double complex z);
10313 float complex clogf(float complex z);
10314 long double complex clogl(long double complex z);
10315 </pre>
10316 <p><b>Description</b>
10317 <p><!--para 2 -->
10318 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
10319 cut along the negative real axis.
10320 <p><b>Returns</b>
10321 <p><!--para 3 -->
10322 The clog functions return the complex natural logarithm value, in the range of a strip
10323 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
10324 imaginary axis.
10329 <p><b>Synopsis</b>
10330 <p><!--para 1 -->
10331 <pre>
10333 double cabs(double complex z);
10334 float cabsf(float complex z);
10335 long double cabsl(long double complex z);
10336 </pre>
10337 <p><b>Description</b>
10338 <p><!--para 2 -->
10339 The cabs functions compute the complex absolute value (also called norm, modulus, or
10340 magnitude) of z.
10341 <p><b>Returns</b>
10342 <p><!--para 3 -->
10343 The cabs functions return the complex absolute value.
10346 <p><b>Synopsis</b>
10347 <p><!--para 1 -->
10348 <!--page 213 -->
10349 <pre>
10351 double complex cpow(double complex x, double complex y);
10352 float complex cpowf(float complex x, float complex y);
10353 long double complex cpowl(long double complex x,
10354 long double complex y);
10355 </pre>
10356 <p><b>Description</b>
10357 <p><!--para 2 -->
10358 The cpow functions compute the complex power function xy , with a branch cut for the
10359 first parameter along the negative real axis.
10360 <p><b>Returns</b>
10361 <p><!--para 3 -->
10362 The cpow functions return the complex power function value.
10365 <p><b>Synopsis</b>
10366 <p><!--para 1 -->
10367 <pre>
10369 double complex csqrt(double complex z);
10370 float complex csqrtf(float complex z);
10371 long double complex csqrtl(long double complex z);
10372 </pre>
10373 <p><b>Description</b>
10374 <p><!--para 2 -->
10375 The csqrt functions compute the complex square root of z, with a branch cut along the
10376 negative real axis.
10377 <p><b>Returns</b>
10378 <p><!--para 3 -->
10379 The csqrt functions return the complex square root value, in the range of the right half-
10380 plane (including the imaginary axis).
10385 <p><b>Synopsis</b>
10386 <p><!--para 1 -->
10387 <pre>
10389 double carg(double complex z);
10390 float cargf(float complex z);
10391 long double cargl(long double complex z);
10392 </pre>
10393 <p><b>Description</b>
10394 <p><!--para 2 -->
10395 The carg functions compute the argument (also called phase angle) of z, with a branch
10396 cut along the negative real axis.
10397 <p><b>Returns</b>
10398 <p><!--para 3 -->
10399 The carg functions return the value of the argument in the interval [-pi , +pi ].
10400 <!--page 214 -->
10403 <p><b>Synopsis</b>
10404 <p><!--para 1 -->
10405 <pre>
10407 double cimag(double complex z);
10408 float cimagf(float complex z);
10409 long double cimagl(long double complex z);
10410 </pre>
10411 <p><b>Description</b>
10412 <p><!--para 2 -->
10413 The cimag functions compute the imaginary part of z.<sup><a href="#note196"><b>196)</b></a></sup>
10414 <p><b>Returns</b>
10415 <p><!--para 3 -->
10416 The cimag functions return the imaginary part value (as a real).
10418 <p><b>Footnotes</b>
10419 <p><small><a name="note196" href="#note196">196)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
10420 </small>
10423 <p><b>Synopsis</b>
10424 <p><!--para 1 -->
10425 <pre>
10427 double complex CMPLX(double x, double y);
10428 float complex CMPLXF(float x, float y);
10429 long double complex CMPLXL(long double x, long double y);
10430 </pre>
10431 <p><b>Description</b>
10432 <p><!--para 2 -->
10433 The CMPLX macros expand to an expression of the specified complex type, with the real
10434 part having the (converted) value of x and the imaginary part having the (converted)
10435 value of y.
10436 <p><b>Recommended practice</b>
10437 <p><!--para 3 -->
10438 The resulting expression should be suitable for use as an initializer for an object with
10439 static or thread storage duration, provided both arguments are likewise suitable.
10440 <p><b>Returns</b>
10441 <p><!--para 4 -->
10442 The CMPLX macros return the complex value x + i y.
10443 <p><!--para 5 -->
10444 NOTE These macros act as if the implementation supported imaginary types and the definitions were:
10445 <pre>
10446 #define CMPLX(x, y) ((double complex)((double)(x) + \
10447 _Imaginary_I * (double)(y)))
10448 #define CMPLXF(x, y) ((float complex)((float)(x) + \
10449 _Imaginary_I * (float)(y)))
10450 #define CMPLXL(x, y) ((long double complex)((long double)(x) + \
10451 _Imaginary_I * (long double)(y)))
10452 </pre>
10457 <!--page 215 -->
10460 <p><b>Synopsis</b>
10461 <p><!--para 1 -->
10462 <pre>
10464 double complex conj(double complex z);
10465 float complex conjf(float complex z);
10466 long double complex conjl(long double complex z);
10467 </pre>
10468 <p><b>Description</b>
10469 <p><!--para 2 -->
10470 The conj functions compute the complex conjugate of z, by reversing the sign of its
10471 imaginary part.
10472 <p><b>Returns</b>
10473 <p><!--para 3 -->
10474 The conj functions return the complex conjugate value.
10477 <p><b>Synopsis</b>
10478 <p><!--para 1 -->
10479 <pre>
10481 double complex cproj(double complex z);
10482 float complex cprojf(float complex z);
10483 long double complex cprojl(long double complex z);
10484 </pre>
10485 <p><b>Description</b>
10486 <p><!--para 2 -->
10487 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
10488 z except that all complex infinities (even those with one infinite part and one NaN part)
10489 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
10490 equivalent to
10491 <pre>
10492 INFINITY + I * copysign(0.0, cimag(z))
10493 </pre>
10494 <p><b>Returns</b>
10495 <p><!--para 3 -->
10496 The cproj functions return the value of the projection onto the Riemann sphere.
10499 <p><b>Synopsis</b>
10500 <p><!--para 1 -->
10501 <pre>
10503 double creal(double complex z);
10504 float crealf(float complex z);
10505 long double creall(long double complex z);
10506 </pre>
10507 <p><b>Description</b>
10508 <p><!--para 2 -->
10510 <!--page 216 -->
10511 <p><b>Returns</b>
10512 <p><!--para 3 -->
10513 The creal functions return the real part value.
10518 <!--page 217 -->
10520 <p><b>Footnotes</b>
10521 <p><small><a name="note197" href="#note197">197)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
10522 </small>
10525 <p><!--para 1 -->
10526 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
10527 characters.<sup><a href="#note198"><b>198)</b></a></sup> In all cases the argument is an int, the value of which shall be
10528 representable as an unsigned char or shall equal the value of the macro EOF. If the
10529 argument has any other value, the behavior is undefined.
10530 <p><!--para 2 -->
10531 The behavior of these functions is affected by the current locale. Those functions that
10533 <p><!--para 3 -->
10534 The term printing character refers to a member of a locale-specific set of characters, each
10535 of which occupies one printing position on a display device; the term control character
10536 refers to a member of a locale-specific set of characters that are not printing
10537 characters.<sup><a href="#note199"><b>199)</b></a></sup> All letters and digits are printing characters.
10538 <p><b> Forward references</b>: EOF (<a href="#7.21.1">7.21.1</a>), localization (<a href="#7.11">7.11</a>).
10540 <p><b>Footnotes</b>
10541 <p><small><a name="note198" href="#note198">198)</a> See ''future library directions'' (<a href="#7.30.2">7.30.2</a>).
10542 </small>
10543 <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
10544 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
10545 values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
10546 </small>
10549 <p><!--para 1 -->
10550 The functions in this subclause return nonzero (true) if and only if the value of the
10551 argument c conforms to that in the description of the function.
10554 <p><b>Synopsis</b>
10555 <p><!--para 1 -->
10556 <pre>
10558 int isalnum(int c);
10559 </pre>
10560 <p><b>Description</b>
10561 <p><!--para 2 -->
10562 The isalnum function tests for any character for which isalpha or isdigit is true.
10565 <p><b>Synopsis</b>
10566 <p><!--para 1 -->
10567 <pre>
10569 int isalpha(int c);
10570 </pre>
10571 <p><b>Description</b>
10572 <p><!--para 2 -->
10573 The isalpha function tests for any character for which isupper or islower is true,
10574 or any character that is one of a locale-specific set of alphabetic characters for which
10578 <!--page 218 -->
10579 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note200"><b>200)</b></a></sup> In the "C" locale,
10580 isalpha returns true only for the characters for which isupper or islower is true.
10582 <p><b>Footnotes</b>
10583 <p><small><a name="note200" href="#note200">200)</a> The functions islower and isupper test true or false separately for each of these additional
10584 characters; all four combinations are possible.
10585 </small>
10588 <p><b>Synopsis</b>
10589 <p><!--para 1 -->
10590 <pre>
10592 int isblank(int c);
10593 </pre>
10594 <p><b>Description</b>
10595 <p><!--para 2 -->
10596 The isblank function tests for any character that is a standard blank character or is one
10597 of a locale-specific set of characters for which isspace is true and that is used to
10598 separate words within a line of text. The standard blank characters are the following:
10600 for the standard blank characters.
10603 <p><b>Synopsis</b>
10604 <p><!--para 1 -->
10605 <pre>
10607 int iscntrl(int c);
10608 </pre>
10609 <p><b>Description</b>
10610 <p><!--para 2 -->
10611 The iscntrl function tests for any control character.
10614 <p><b>Synopsis</b>
10615 <p><!--para 1 -->
10616 <pre>
10618 int isdigit(int c);
10619 </pre>
10620 <p><b>Description</b>
10621 <p><!--para 2 -->
10622 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
10625 <p><b>Synopsis</b>
10626 <p><!--para 1 -->
10627 <pre>
10629 int isgraph(int c);
10630 </pre>
10635 <!--page 219 -->
10636 <p><b>Description</b>
10637 <p><!--para 2 -->
10638 The isgraph function tests for any printing character except space (' ').
10641 <p><b>Synopsis</b>
10642 <p><!--para 1 -->
10643 <pre>
10645 int islower(int c);
10646 </pre>
10647 <p><b>Description</b>
10648 <p><!--para 2 -->
10649 The islower function tests for any character that is a lowercase letter or is one of a
10650 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
10655 <p><b>Synopsis</b>
10656 <p><!--para 1 -->
10657 <pre>
10659 int isprint(int c);
10660 </pre>
10661 <p><b>Description</b>
10662 <p><!--para 2 -->
10663 The isprint function tests for any printing character including space (' ').
10666 <p><b>Synopsis</b>
10667 <p><!--para 1 -->
10668 <pre>
10670 int ispunct(int c);
10671 </pre>
10672 <p><b>Description</b>
10673 <p><!--para 2 -->
10674 The ispunct function tests for any printing character that is one of a locale-specific set
10676 locale, ispunct returns true for every printing character for which neither isspace
10677 nor isalnum is true.
10680 <p><b>Synopsis</b>
10681 <p><!--para 1 -->
10682 <pre>
10684 int isspace(int c);
10685 </pre>
10686 <p><b>Description</b>
10687 <p><!--para 2 -->
10688 The isspace function tests for any character that is a standard white-space character or
10689 is one of a locale-specific set of characters for which isalnum is false. The standard
10690 <!--page 220 -->
10691 white-space characters are the following: space (' '), form feed ('\f'), new-line
10692 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
10696 <p><b>Synopsis</b>
10697 <p><!--para 1 -->
10698 <pre>
10700 int isupper(int c);
10701 </pre>
10702 <p><b>Description</b>
10703 <p><!--para 2 -->
10704 The isupper function tests for any character that is an uppercase letter or is one of a
10705 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
10710 <p><b>Synopsis</b>
10711 <p><!--para 1 -->
10712 <pre>
10714 int isxdigit(int c);
10715 </pre>
10716 <p><b>Description</b>
10717 <p><!--para 2 -->
10718 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
10723 <p><b>Synopsis</b>
10724 <p><!--para 1 -->
10725 <pre>
10727 int tolower(int c);
10728 </pre>
10729 <p><b>Description</b>
10730 <p><!--para 2 -->
10731 The tolower function converts an uppercase letter to a corresponding lowercase letter.
10732 <p><b>Returns</b>
10733 <p><!--para 3 -->
10734 If the argument is a character for which isupper is true and there are one or more
10735 corresponding characters, as specified by the current locale, for which islower is true,
10736 the tolower function returns one of the corresponding characters (always the same one
10737 for any given locale); otherwise, the argument is returned unchanged.
10738 <!--page 221 -->
10741 <p><b>Synopsis</b>
10742 <p><!--para 1 -->
10743 <pre>
10745 int toupper(int c);
10746 </pre>
10747 <p><b>Description</b>
10748 <p><!--para 2 -->
10749 The toupper function converts a lowercase letter to a corresponding uppercase letter.
10750 <p><b>Returns</b>
10751 <p><!--para 3 -->
10752 If the argument is a character for which islower is true and there are one or more
10753 corresponding characters, as specified by the current locale, for which isupper is true,
10754 the toupper function returns one of the corresponding characters (always the same one
10755 for any given locale); otherwise, the argument is returned unchanged.
10756 <!--page 222 -->
10759 <p><!--para 1 -->
10760 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
10761 conditions.
10762 <p><!--para 2 -->
10763 The macros are
10764 <pre>
10765 EDOM
10766 EILSEQ
10767 ERANGE
10768 </pre>
10769 which expand to integer constant expressions with type int, distinct positive values, and
10770 which are suitable for use in #if preprocessing directives; and
10771 <pre>
10772 errno
10773 </pre>
10774 which expands to a modifiable lvalue<sup><a href="#note201"><b>201)</b></a></sup> that has type int and thread local storage
10775 duration, the value of which is set to a positive error number by several library functions.
10776 If a macro definition is suppressed in order to access an actual object, or a program
10777 defines an identifier with the name errno, the behavior is undefined.
10778 <p><!--para 3 -->
10779 The value of errno in the initial thread is zero at program startup (the initial value of
10780 errno in other threads is an indeterminate value), but is never set to zero by any library
10781 function.<sup><a href="#note202"><b>202)</b></a></sup> The value of errno may be set to nonzero by a library function call
10782 whether or not there is an error, provided the use of errno is not documented in the
10783 description of the function in this International Standard.
10784 <p><!--para 4 -->
10785 Additional macro definitions, beginning with E and a digit or E and an uppercase
10786 letter,<sup><a href="#note203"><b>203)</b></a></sup> may also be specified by the implementation.
10791 <!--page 223 -->
10793 <p><b>Footnotes</b>
10794 <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
10795 resulting from a function call (for example, *errno()).
10796 </small>
10797 <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,
10798 then inspect it before a subsequent library function call. Of course, a library function can save the
10799 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
10800 value is still zero just before the return.
10801 </small>
10802 <p><small><a name="note203" href="#note203">203)</a> See ''future library directions'' (<a href="#7.30.3">7.30.3</a>).
10803 </small>
10806 <p><!--para 1 -->
10807 The header <a href="#7.6"><fenv.h></a> defines several macros, and declares types and functions that
10808 provide access to the floating-point environment. The floating-point environment refers
10809 collectively to any floating-point status flags and control modes supported by the
10810 implementation.<sup><a href="#note204"><b>204)</b></a></sup> A floating-point status flag is a system variable whose value is set
10811 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
10812 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note205"><b>205)</b></a></sup> A floating-
10813 point control mode is a system variable whose value may be set by the user to affect the
10814 subsequent behavior of floating-point arithmetic.
10815 <p><!--para 2 -->
10816 The floating-point environment has thread storage duration. The initial state for a
10817 thread's floating-point environment is the current state of the floating-point environment
10818 of the thread that creates it at the time of creation.
10819 <p><!--para 3 -->
10820 Certain programming conventions support the intended model of use for the floating-
10822 <ul>
10823 <li> a function call does not alter its caller's floating-point control modes, clear its caller's
10824 floating-point status flags, nor depend on the state of its caller's floating-point status
10825 flags unless the function is so documented;
10826 <li> a function call is assumed to require default floating-point control modes, unless its
10827 documentation promises otherwise;
10828 <li> a function call is assumed to have the potential for raising floating-point exceptions,
10829 unless its documentation promises otherwise.
10830 </ul>
10831 <p><!--para 4 -->
10832 The type
10833 <pre>
10834 fenv_t
10835 </pre>
10836 represents the entire floating-point environment.
10837 <p><!--para 5 -->
10838 The type
10839 <pre>
10840 fexcept_t
10841 </pre>
10842 represents the floating-point status flags collectively, including any status the
10843 implementation associates with the flags.
10846 <!--page 224 -->
10847 <p><!--para 6 -->
10848 Each of the macros
10849 <pre>
10850 FE_DIVBYZERO
10851 FE_INEXACT
10852 FE_INVALID
10853 FE_OVERFLOW
10854 FE_UNDERFLOW
10855 </pre>
10856 is defined if and only if the implementation supports the floating-point exception by
10857 means of the functions in 7.6.2.<sup><a href="#note207"><b>207)</b></a></sup> Additional implementation-defined floating-point
10858 exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
10859 be specified by the implementation. The defined macros expand to integer constant
10860 expressions with values such that bitwise ORs of all combinations of the macros result in
10861 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
10863 <p><!--para 7 -->
10864 The macro
10865 <pre>
10866 FE_ALL_EXCEPT
10867 </pre>
10868 is simply the bitwise OR of all floating-point exception macros defined by the
10869 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
10870 <p><!--para 8 -->
10871 Each of the macros
10872 <pre>
10873 FE_DOWNWARD
10874 FE_TONEAREST
10875 FE_TOWARDZERO
10876 FE_UPWARD
10877 </pre>
10878 is defined if and only if the implementation supports getting and setting the represented
10879 rounding direction by means of the fegetround and fesetround functions.
10880 Additional implementation-defined rounding directions, with macro definitions beginning
10881 with FE_ and an uppercase letter, may also be specified by the implementation. The
10882 defined macros expand to integer constant expressions whose values are distinct
10884 <p><!--para 9 -->
10885 The macro
10889 <!--page 225 -->
10890 <pre>
10891 FE_DFL_ENV
10892 </pre>
10893 represents the default floating-point environment -- the one installed at program startup
10894 <ul>
10895 <li> and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
10896 </ul>
10898 <p><!--para 10 -->
10899 Additional implementation-defined environments, with macro definitions beginning with
10900 FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
10901 also be specified by the implementation.
10903 <p><b>Footnotes</b>
10904 <p><small><a name="note204" href="#note204">204)</a> This header is designed to support the floating-point exception status flags and directed-rounding
10905 control modes required by IEC 60559, and other similar floating-point state information. It is also
10906 designed to facilitate code portability among all systems.
10907 </small>
10908 <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.
10909 </small>
10910 <p><small><a name="note206" href="#note206">206)</a> With these conventions, a programmer can safely assume default floating-point control modes (or be
10911 unaware of them). The responsibilities associated with accessing the floating-point environment fall
10912 on the programmer or program that does so explicitly.
10913 </small>
10914 <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
10915 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
10916 necessary for all the functions to succeed all the time.
10917 </small>
10918 <p><small><a name="note208" href="#note208">208)</a> The macros should be distinct powers of two.
10919 </small>
10920 <p><small><a name="note209" href="#note209">209)</a> Even though the rounding direction macros may expand to constants corresponding to the values of
10921 FLT_ROUNDS, they are not required to do so.
10922 </small>
10925 <p><b>Synopsis</b>
10926 <p><!--para 1 -->
10927 <pre>
10929 #pragma STDC FENV_ACCESS on-off-switch
10930 </pre>
10931 <p><b>Description</b>
10932 <p><!--para 2 -->
10933 The FENV_ACCESS pragma provides a means to inform the implementation when a
10934 program might access the floating-point environment to test floating-point status flags or
10935 run under non-default floating-point control modes.<sup><a href="#note210"><b>210)</b></a></sup> The pragma shall occur either
10936 outside external declarations or preceding all explicit declarations and statements inside a
10937 compound statement. When outside external declarations, the pragma takes effect from
10938 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
10939 the translation unit. When inside a compound statement, the pragma takes effect from its
10940 occurrence until another FENV_ACCESS pragma is encountered (including within a
10941 nested compound statement), or until the end of the compound statement; at the end of a
10942 compound statement the state for the pragma is restored to its condition just before the
10943 compound statement. If this pragma is used in any other context, the behavior is
10944 undefined. If part of a program tests floating-point status flags, sets floating-point control
10945 modes, or runs under non-default mode settings, but was translated with the state for the
10946 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
10947 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
10948 the program translated with FENV_ACCESS ''off'' to a part translated with
10949 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
10950 floating-point control modes have their default settings.)
10955 <!--page 226 -->
10956 <p><!--para 3 -->
10957 EXAMPLE
10958 <pre>
10960 void f(double x)
10961 {
10962 #pragma STDC FENV_ACCESS ON
10963 void g(double);
10964 void h(double);
10965 /* ... */
10966 g(x + 1);
10967 h(x + 1);
10968 /* ... */
10969 }
10970 </pre>
10971 <p><!--para 4 -->
10972 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
10973 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
10974 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note211"><b>211)</b></a></sup>
10977 <p><b>Footnotes</b>
10978 <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
10979 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
10980 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
10981 modes are in effect and the flags are not tested.
10982 </small>
10983 <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
10984 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
10985 ''off'', just one evaluation of x + 1 would suffice.
10986 </small>
10989 <p><!--para 1 -->
10990 The following functions provide access to the floating-point status flags.<sup><a href="#note212"><b>212)</b></a></sup> The int
10991 input argument for the functions represents a subset of floating-point exceptions, and can
10992 be zero or the bitwise OR of one or more floating-point exception macros, for example
10993 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
10994 functions is undefined.
10996 <p><b>Footnotes</b>
10997 <p><small><a name="note212" href="#note212">212)</a> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
10998 abstraction of flags that are either set or clear. An implementation may endow floating-point status
10999 flags with more information -- for example, the address of the code which first raised the floating-
11000 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
11001 content of flags.
11002 </small>
11005 <p><b>Synopsis</b>
11006 <p><!--para 1 -->
11007 <pre>
11009 int feclearexcept(int excepts);
11010 </pre>
11011 <p><b>Description</b>
11012 <p><!--para 2 -->
11013 The feclearexcept function attempts to clear the supported floating-point exceptions
11014 represented by its argument.
11015 <p><b>Returns</b>
11016 <p><!--para 3 -->
11017 The feclearexcept function returns zero if the excepts argument is zero or if all
11018 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
11021 <!--page 227 -->
11024 <p><b>Synopsis</b>
11025 <p><!--para 1 -->
11026 <pre>
11028 int fegetexceptflag(fexcept_t *flagp,
11029 int excepts);
11030 </pre>
11031 <p><b>Description</b>
11032 <p><!--para 2 -->
11033 The fegetexceptflag function attempts to store an implementation-defined
11034 representation of the states of the floating-point status flags indicated by the argument
11035 excepts in the object pointed to by the argument flagp.
11036 <p><b>Returns</b>
11037 <p><!--para 3 -->
11038 The fegetexceptflag function returns zero if the representation was successfully
11039 stored. Otherwise, it returns a nonzero value.
11042 <p><b>Synopsis</b>
11043 <p><!--para 1 -->
11044 <pre>
11046 int feraiseexcept(int excepts);
11047 </pre>
11048 <p><b>Description</b>
11049 <p><!--para 2 -->
11050 The feraiseexcept function attempts to raise the supported floating-point exceptions
11051 represented by its argument.<sup><a href="#note213"><b>213)</b></a></sup> The order in which these floating-point exceptions are
11052 raised is unspecified, except as stated in <a href="#F.8.6">F.8.6</a>. Whether the feraiseexcept function
11053 additionally raises the ''inexact'' floating-point exception whenever it raises the
11054 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
11055 <p><b>Returns</b>
11056 <p><!--para 3 -->
11057 The feraiseexcept function returns zero if the excepts argument is zero or if all
11058 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
11063 <!--page 228 -->
11065 <p><b>Footnotes</b>
11066 <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.
11067 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
11069 </small>
11072 <p><b>Synopsis</b>
11073 <p><!--para 1 -->
11074 <pre>
11076 int fesetexceptflag(const fexcept_t *flagp,
11077 int excepts);
11078 </pre>
11079 <p><b>Description</b>
11080 <p><!--para 2 -->
11081 The fesetexceptflag function attempts to set the floating-point status flags
11082 indicated by the argument excepts to the states stored in the object pointed to by
11083 flagp. The value of *flagp shall have been set by a previous call to
11084 fegetexceptflag whose second argument represented at least those floating-point
11085 exceptions represented by the argument excepts. This function does not raise floating-
11086 point exceptions, but only sets the state of the flags.
11087 <p><b>Returns</b>
11088 <p><!--para 3 -->
11089 The fesetexceptflag function returns zero if the excepts argument is zero or if
11090 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
11091 a nonzero value.
11094 <p><b>Synopsis</b>
11095 <p><!--para 1 -->
11096 <pre>
11098 int fetestexcept(int excepts);
11099 </pre>
11100 <p><b>Description</b>
11101 <p><!--para 2 -->
11102 The fetestexcept function determines which of a specified subset of the floating-
11103 point exception flags are currently set. The excepts argument specifies the floating-
11105 <p><b>Returns</b>
11106 <p><!--para 3 -->
11107 The fetestexcept function returns the value of the bitwise OR of the floating-point
11108 exception macros corresponding to the currently set floating-point exceptions included in
11109 excepts.
11110 <p><!--para 4 -->
11111 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
11116 <!--page 229 -->
11117 <pre>
11119 /* ... */
11120 {
11121 #pragma STDC FENV_ACCESS ON
11122 int set_excepts;
11123 feclearexcept(FE_INVALID | FE_OVERFLOW);
11124 // maybe raise exceptions
11125 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
11126 if (set_excepts & FE_INVALID) f();
11127 if (set_excepts & FE_OVERFLOW) g();
11128 /* ... */
11129 }
11130 </pre>
11133 <p><b>Footnotes</b>
11134 <p><small><a name="note214" href="#note214">214)</a> This mechanism allows testing several floating-point exceptions with just one function call.
11135 </small>
11138 <p><!--para 1 -->
11139 The fegetround and fesetround functions provide control of rounding direction
11140 modes.
11143 <p><b>Synopsis</b>
11144 <p><!--para 1 -->
11145 <pre>
11147 int fegetround(void);
11148 </pre>
11149 <p><b>Description</b>
11150 <p><!--para 2 -->
11151 The fegetround function gets the current rounding direction.
11152 <p><b>Returns</b>
11153 <p><!--para 3 -->
11154 The fegetround function returns the value of the rounding direction macro
11155 representing the current rounding direction or a negative value if there is no such
11156 rounding direction macro or the current rounding direction is not determinable.
11159 <p><b>Synopsis</b>
11160 <p><!--para 1 -->
11161 <pre>
11163 int fesetround(int round);
11164 </pre>
11165 <p><b>Description</b>
11166 <p><!--para 2 -->
11167 The fesetround function establishes the rounding direction represented by its
11168 argument round. If the argument is not equal to the value of a rounding direction macro,
11169 the rounding direction is not changed.
11170 <p><b>Returns</b>
11171 <p><!--para 3 -->
11172 The fesetround function returns zero if and only if the requested rounding direction
11173 was established.
11174 <!--page 230 -->
11175 <p><!--para 4 -->
11176 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
11177 rounding direction fails.
11178 <pre>
11181 void f(int round_dir)
11182 {
11183 #pragma STDC FENV_ACCESS ON
11184 int save_round;
11185 int setround_ok;
11186 save_round = fegetround();
11187 setround_ok = fesetround(round_dir);
11188 assert(setround_ok == 0);
11189 /* ... */
11190 fesetround(save_round);
11191 /* ... */
11192 }
11193 </pre>
11197 <p><!--para 1 -->
11198 The functions in this section manage the floating-point environment -- status flags and
11199 control modes -- as one entity.
11202 <p><b>Synopsis</b>
11203 <p><!--para 1 -->
11204 <pre>
11206 int fegetenv(fenv_t *envp);
11207 </pre>
11208 <p><b>Description</b>
11209 <p><!--para 2 -->
11210 The fegetenv function attempts to store the current floating-point environment in the
11211 object pointed to by envp.
11212 <p><b>Returns</b>
11213 <p><!--para 3 -->
11214 The fegetenv function returns zero if the environment was successfully stored.
11215 Otherwise, it returns a nonzero value.
11218 <p><b>Synopsis</b>
11219 <p><!--para 1 -->
11220 <pre>
11222 int feholdexcept(fenv_t *envp);
11223 </pre>
11224 <p><b>Description</b>
11225 <p><!--para 2 -->
11226 The feholdexcept function saves the current floating-point environment in the object
11227 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
11228 (continue on floating-point exceptions) mode, if available, for all floating-point
11230 <!--page 231 -->
11231 <p><b>Returns</b>
11232 <p><!--para 3 -->
11233 The feholdexcept function returns zero if and only if non-stop floating-point
11234 exception handling was successfully installed.
11236 <p><b>Footnotes</b>
11237 <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
11238 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
11239 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
11240 function to write routines that hide spurious floating-point exceptions from their callers.
11241 </small>
11244 <p><b>Synopsis</b>
11245 <p><!--para 1 -->
11246 <pre>
11248 int fesetenv(const fenv_t *envp);
11249 </pre>
11250 <p><b>Description</b>
11251 <p><!--para 2 -->
11252 The fesetenv function attempts to establish the floating-point environment represented
11253 by the object pointed to by envp. The argument envp shall point to an object set by a
11254 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
11255 Note that fesetenv merely installs the state of the floating-point status flags
11256 represented through its argument, and does not raise these floating-point exceptions.
11257 <p><b>Returns</b>
11258 <p><!--para 3 -->
11259 The fesetenv function returns zero if the environment was successfully established.
11260 Otherwise, it returns a nonzero value.
11263 <p><b>Synopsis</b>
11264 <p><!--para 1 -->
11265 <pre>
11267 int feupdateenv(const fenv_t *envp);
11268 </pre>
11269 <p><b>Description</b>
11270 <p><!--para 2 -->
11271 The feupdateenv function attempts to save the currently raised floating-point
11272 exceptions in its automatic storage, install the floating-point environment represented by
11273 the object pointed to by envp, and then raise the saved floating-point exceptions. The
11274 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
11275 or equal a floating-point environment macro.
11276 <p><b>Returns</b>
11277 <p><!--para 3 -->
11278 The feupdateenv function returns zero if all the actions were successfully carried out.
11279 Otherwise, it returns a nonzero value.
11284 <!--page 232 -->
11285 <p><!--para 4 -->
11286 EXAMPLE Hide spurious underflow floating-point exceptions:
11287 <!--page 233 -->
11288 <pre>
11290 double f(double x)
11291 {
11292 #pragma STDC FENV_ACCESS ON
11293 double result;
11294 fenv_t save_env;
11295 if (feholdexcept(&save_env))
11296 return /* indication of an environmental problem */;
11297 // compute result
11298 if (/* test spurious underflow */)
11299 if (feclearexcept(FE_UNDERFLOW))
11300 return /* indication of an environmental problem */;
11301 if (feupdateenv(&save_env))
11302 return /* indication of an environmental problem */;
11303 return result;
11304 }
11305 </pre>
11308 <p><!--para 1 -->
11309 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
11310 parameters of the standard floating-point types.
11311 <p><!--para 2 -->
11312 The macros, their meanings, and the constraints (or restrictions) on their values are listed
11314 <!--page 234 -->
11316 <h3><a name="7.8" href="#7.8">7.8 Format conversion of integer types <inttypes.h></a></h3>
11317 <p><!--para 1 -->
11318 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.20"><stdint.h></a> and extends it with
11319 additional facilities provided by hosted implementations.
11320 <p><!--para 2 -->
11321 It declares functions for manipulating greatest-width integers and converting numeric
11322 character strings to greatest-width integers, and it declares the type
11323 <pre>
11324 imaxdiv_t
11325 </pre>
11326 which is a structure type that is the type of the value returned by the imaxdiv function.
11327 For each type declared in <a href="#7.20"><stdint.h></a>, it defines corresponding macros for conversion
11328 specifiers for use with the formatted input/output functions.<sup><a href="#note216"><b>216)</b></a></sup>
11329 <p><b> Forward references</b>: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>), formatted input/output
11330 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>).
11332 <p><b>Footnotes</b>
11333 <p><small><a name="note216" href="#note216">216)</a> See ''future library directions'' (<a href="#7.30.4">7.30.4</a>).
11334 </small>
11337 <p><!--para 1 -->
11338 Each of the following object-like macros expands to a character string literal containing a *
11339 conversion specifier, possibly modified by a length modifier, suitable for use within the
11340 format argument of a formatted input/output function when converting the corresponding
11341 integer type. These macro names have the general form of PRI (character string literals
11342 for the fprintf and fwprintf family) or SCN (character string literals for the
11343 fscanf and fwscanf family),<sup><a href="#note217"><b>217)</b></a></sup> followed by the conversion specifier, followed by a
11344 name corresponding to a similar type name in <a href="#7.20.1">7.20.1</a>. In these names, N represents the
11345 width of the type as described in <a href="#7.20.1">7.20.1</a>. For example, PRIdFAST32 can be used in a
11346 format string to print the value of an integer of type int_fast32_t.
11347 <p><!--para 2 -->
11348 The fprintf macros for signed integers are:
11349 <pre>
11350 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
11351 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
11352 </pre>
11353 <p><!--para 3 -->
11354 The fprintf macros for unsigned integers are:
11355 <pre>
11356 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
11357 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
11358 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
11359 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
11360 </pre>
11361 <p><!--para 4 -->
11362 The fscanf macros for signed integers are:
11366 <!--page 235 -->
11367 <pre>
11368 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
11369 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
11370 </pre>
11371 <p><!--para 5 -->
11372 The fscanf macros for unsigned integers are:
11373 <pre>
11374 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
11375 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
11376 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
11377 </pre>
11378 <p><!--para 6 -->
11379 For each type that the implementation provides in <a href="#7.20"><stdint.h></a>, the corresponding
11380 fprintf macros shall be defined and the corresponding fscanf macros shall be
11381 defined unless the implementation does not have a suitable fscanf length modifier for
11382 the type.
11383 <p><!--para 7 -->
11384 EXAMPLE
11385 <pre>
11388 int main(void)
11389 {
11390 uintmax_t i = UINTMAX_MAX; // this type always exists
11393 return 0;
11394 }
11395 </pre>
11398 <p><b>Footnotes</b>
11399 <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,
11400 different format specifiers may be required for fprintf and fscanf, even when the type is the
11401 same.
11402 </small>
11407 <p><b>Synopsis</b>
11408 <p><!--para 1 -->
11409 <pre>
11411 intmax_t imaxabs(intmax_t j);
11412 </pre>
11413 <p><b>Description</b>
11414 <p><!--para 2 -->
11415 The imaxabs function computes the absolute value of an integer j. If the result cannot
11417 <p><b>Returns</b>
11418 <p><!--para 3 -->
11419 The imaxabs function returns the absolute value.
11424 <!--page 236 -->
11426 <p><b>Footnotes</b>
11427 <p><small><a name="note218" href="#note218">218)</a> The absolute value of the most negative number cannot be represented in two's complement.
11428 </small>
11431 <p><b>Synopsis</b>
11432 <p><!--para 1 -->
11433 <pre>
11435 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
11436 </pre>
11437 <p><b>Description</b>
11438 <p><!--para 2 -->
11439 The imaxdiv function computes numer / denom and numer % denom in a single
11440 operation.
11441 <p><b>Returns</b>
11442 <p><!--para 3 -->
11443 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
11444 quotient and the remainder. The structure shall contain (in either order) the members
11445 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
11446 either part of the result cannot be represented, the behavior is undefined.
11449 <p><b>Synopsis</b>
11450 <p><!--para 1 -->
11451 <pre>
11453 intmax_t strtoimax(const char * restrict nptr,
11454 char ** restrict endptr, int base);
11455 uintmax_t strtoumax(const char * restrict nptr,
11456 char ** restrict endptr, int base);
11457 </pre>
11458 <p><b>Description</b>
11459 <p><!--para 2 -->
11460 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
11461 strtoul, and strtoull functions, except that the initial portion of the string is
11462 converted to intmax_t and uintmax_t representation, respectively.
11463 <p><b>Returns</b>
11464 <p><!--para 3 -->
11465 The strtoimax and strtoumax functions return the converted value, if any. If no
11466 conversion could be performed, zero is returned. If the correct value is outside the range
11467 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
11468 (according to the return type and sign of the value, if any), and the value of the macro
11469 ERANGE is stored in errno.
11470 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
11472 <!--page 237 -->
11475 <p><b>Synopsis</b>
11476 <p><!--para 1 -->
11477 <pre>
11480 intmax_t wcstoimax(const wchar_t * restrict nptr,
11481 wchar_t ** restrict endptr, int base);
11482 uintmax_t wcstoumax(const wchar_t * restrict nptr,
11483 wchar_t ** restrict endptr, int base);
11484 </pre>
11485 <p><b>Description</b>
11486 <p><!--para 2 -->
11487 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
11488 wcstoul, and wcstoull functions except that the initial portion of the wide string is
11489 converted to intmax_t and uintmax_t representation, respectively.
11490 <p><b>Returns</b>
11491 <p><!--para 3 -->
11492 The wcstoimax function returns the converted value, if any. If no conversion could be
11493 performed, zero is returned. If the correct value is outside the range of representable
11494 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
11495 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
11496 errno.
11497 <p><b> Forward references</b>: the wcstol, wcstoll, wcstoul, and wcstoull functions
11499 <!--page 238 -->
11502 <p><!--para 1 -->
11503 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
11504 to the corresponding tokens (on the right):
11505 <!--page 239 -->
11506 <pre>
11507 and &&
11508 and_eq &=
11509 bitand &
11510 bitor |
11511 compl ~
11512 not !
11513 not_eq !=
11514 or ||
11515 or_eq |=
11516 xor ^
11517 xor_eq ^=
11518 </pre>
11521 <p><!--para 1 -->
11522 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
11523 parameters of the standard integer types.
11524 <p><!--para 2 -->
11525 The macros, their meanings, and the constraints (or restrictions) on their values are listed
11527 <!--page 240 -->
11530 <p><!--para 1 -->
11531 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
11532 <p><!--para 2 -->
11533 The type is
11534 <pre>
11535 struct lconv
11536 </pre>
11537 which contains members related to the formatting of numeric values. The structure shall
11538 contain at least the following members, in any order. The semantics of the members and
11539 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
11540 the values specified in the comments.
11541 <!--page 241 -->
11542 <pre>
11552 char frac_digits; // CHAR_MAX
11553 char p_cs_precedes; // CHAR_MAX
11554 char n_cs_precedes; // CHAR_MAX
11555 char p_sep_by_space; // CHAR_MAX
11556 char n_sep_by_space; // CHAR_MAX
11557 char p_sign_posn; // CHAR_MAX
11558 char n_sign_posn; // CHAR_MAX
11560 char int_frac_digits; // CHAR_MAX
11561 char int_p_cs_precedes; // CHAR_MAX
11562 char int_n_cs_precedes; // CHAR_MAX
11563 char int_p_sep_by_space; // CHAR_MAX
11564 char int_n_sep_by_space; // CHAR_MAX
11565 char int_p_sign_posn; // CHAR_MAX
11566 char int_n_sign_posn; // CHAR_MAX
11567 </pre>
11568 <p><!--para 3 -->
11570 <pre>
11571 LC_ALL
11572 LC_COLLATE
11573 LC_CTYPE
11574 LC_MONETARY
11575 LC_NUMERIC
11576 LC_TIME
11577 </pre>
11578 which expand to integer constant expressions with distinct values, suitable for use as the
11579 first argument to the setlocale function.<sup><a href="#note219"><b>219)</b></a></sup> Additional macro definitions, beginning
11580 with the characters LC_ and an uppercase letter,<sup><a href="#note220"><b>220)</b></a></sup> may also be specified by the
11581 implementation.
11583 <p><b>Footnotes</b>
11584 <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.
11585 </small>
11586 <p><small><a name="note220" href="#note220">220)</a> See ''future library directions'' (<a href="#7.30.5">7.30.5</a>).
11587 </small>
11592 <p><b>Synopsis</b>
11593 <p><!--para 1 -->
11594 <pre>
11596 char *setlocale(int category, const char *locale);
11597 </pre>
11598 <p><b>Description</b>
11599 <p><!--para 2 -->
11600 The setlocale function selects the appropriate portion of the program's locale as
11601 specified by the category and locale arguments. The setlocale function may be
11602 used to change or query the program's entire current locale or portions thereof. The value
11603 LC_ALL for category names the program's entire locale; the other values for
11604 category name only a portion of the program's locale. LC_COLLATE affects the
11605 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
11606 the character handling functions<sup><a href="#note221"><b>221)</b></a></sup> and the multibyte and wide character functions.
11607 LC_MONETARY affects the monetary formatting information returned by the
11608 localeconv function. LC_NUMERIC affects the decimal-point character for the
11609 formatted input/output functions and the string conversion functions, as well as the
11610 nonmonetary formatting information returned by the localeconv function. LC_TIME
11611 affects the behavior of the strftime and wcsftime functions.
11612 <p><!--para 3 -->
11615 implementation-defined strings may be passed as the second argument to setlocale.
11617 <!--page 242 -->
11618 <p><!--para 4 -->
11619 At program startup, the equivalent of
11620 <pre>
11622 </pre>
11623 is executed.
11624 <p><!--para 5 -->
11625 A call to the setlocale function may introduce a data race with other calls to the
11626 setlocale function or with calls to functions that are affected by the current locale.
11627 The implementation shall behave as if no library function calls the setlocale function.
11628 <p><b>Returns</b>
11629 <p><!--para 6 -->
11630 If a pointer to a string is given for locale and the selection can be honored, the
11631 setlocale function returns a pointer to the string associated with the specified
11632 category for the new locale. If the selection cannot be honored, the setlocale
11633 function returns a null pointer and the program's locale is not changed.
11634 <p><!--para 7 -->
11635 A null pointer for locale causes the setlocale function to return a pointer to the
11636 string associated with the category for the program's current locale; the program's
11638 <p><!--para 8 -->
11639 The pointer to string returned by the setlocale function is such that a subsequent call
11640 with that string value and its associated category will restore that part of the program's
11641 locale. The string pointed to shall not be modified by the program, but may be
11642 overwritten by a subsequent call to the setlocale function.
11643 <p><b> Forward references</b>: formatted input/output functions (<a href="#7.21.6">7.21.6</a>), multibyte/wide
11644 character conversion functions (<a href="#7.22.7">7.22.7</a>), multibyte/wide string conversion functions
11645 (<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
11646 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>).
11648 <p><b>Footnotes</b>
11649 <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
11650 isxdigit.
11651 </small>
11652 <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
11653 locale when category has the value LC_ALL.
11654 </small>
11659 <p><b>Synopsis</b>
11660 <p><!--para 1 -->
11661 <pre>
11663 struct lconv *localeconv(void);
11664 </pre>
11665 <p><b>Description</b>
11666 <p><!--para 2 -->
11667 The localeconv function sets the components of an object with type struct lconv
11668 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
11669 according to the rules of the current locale.
11673 <!--page 243 -->
11674 <p><!--para 3 -->
11675 The members of the structure with type char * are pointers to strings, any of which
11677 the current locale or is of zero length. Apart from grouping and mon_grouping, the
11678 strings shall start and end in the initial shift state. The members with type char are
11679 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
11680 available in the current locale. The members include the following:
11681 char *decimal_point
11682 <pre>
11683 The decimal-point character used to format nonmonetary quantities.
11684 </pre>
11685 char *thousands_sep
11686 <pre>
11687 The character used to separate groups of digits before the decimal-point
11688 character in formatted nonmonetary quantities.
11689 </pre>
11690 char *grouping
11691 <pre>
11692 A string whose elements indicate the size of each group of digits in
11693 formatted nonmonetary quantities.
11694 </pre>
11695 char *mon_decimal_point
11696 <pre>
11697 The decimal-point used to format monetary quantities.
11698 </pre>
11699 char *mon_thousands_sep
11700 <pre>
11701 The separator for groups of digits before the decimal-point in formatted
11702 monetary quantities.
11703 </pre>
11704 char *mon_grouping
11705 <pre>
11706 A string whose elements indicate the size of each group of digits in
11707 formatted monetary quantities.
11708 </pre>
11709 char *positive_sign
11710 <pre>
11711 The string used to indicate a nonnegative-valued formatted monetary
11712 quantity.
11713 </pre>
11714 char *negative_sign
11715 <pre>
11716 The string used to indicate a negative-valued formatted monetary quantity.
11717 </pre>
11718 char *currency_symbol
11719 <pre>
11720 The local currency symbol applicable to the current locale.
11721 </pre>
11722 char frac_digits
11723 <pre>
11724 The number of fractional digits (those after the decimal-point) to be
11725 displayed in a locally formatted monetary quantity.
11726 </pre>
11727 char p_cs_precedes
11728 <!--page 244 -->
11729 <pre>
11730 Set to 1 or 0 if the currency_symbol respectively precedes or
11731 succeeds the value for a nonnegative locally formatted monetary quantity.
11732 </pre>
11733 char n_cs_precedes
11734 <pre>
11735 Set to 1 or 0 if the currency_symbol respectively precedes or
11736 succeeds the value for a negative locally formatted monetary quantity.
11737 </pre>
11738 char p_sep_by_space
11739 <pre>
11740 Set to a value indicating the separation of the currency_symbol, the
11741 sign string, and the value for a nonnegative locally formatted monetary
11742 quantity.
11743 </pre>
11744 char n_sep_by_space
11745 <pre>
11746 Set to a value indicating the separation of the currency_symbol, the
11747 sign string, and the value for a negative locally formatted monetary
11748 quantity.
11749 </pre>
11750 char p_sign_posn
11751 <pre>
11752 Set to a value indicating the positioning of the positive_sign for a
11753 nonnegative locally formatted monetary quantity.
11754 </pre>
11755 char n_sign_posn
11756 <pre>
11757 Set to a value indicating the positioning of the negative_sign for a
11758 negative locally formatted monetary quantity.
11759 </pre>
11760 char *int_curr_symbol
11761 <pre>
11762 The international currency symbol applicable to the current locale. The
11763 first three characters contain the alphabetic international currency symbol
11764 in accordance with those specified in ISO 4217. The fourth character
11765 (immediately preceding the null character) is the character used to separate
11766 the international currency symbol from the monetary quantity.
11767 </pre>
11768 char int_frac_digits
11769 <pre>
11770 The number of fractional digits (those after the decimal-point) to be
11771 displayed in an internationally formatted monetary quantity.
11772 </pre>
11773 char int_p_cs_precedes
11774 <pre>
11775 Set to 1 or 0 if the int_curr_symbol respectively precedes or
11776 succeeds the value for a nonnegative internationally formatted monetary
11777 quantity.
11778 </pre>
11779 char int_n_cs_precedes
11780 <pre>
11781 Set to 1 or 0 if the int_curr_symbol respectively precedes or
11782 succeeds the value for a negative internationally formatted monetary
11783 quantity.
11784 </pre>
11785 char int_p_sep_by_space
11786 <!--page 245 -->
11787 <pre>
11788 Set to a value indicating the separation of the int_curr_symbol, the
11789 sign string, and the value for a nonnegative internationally formatted
11790 monetary quantity.
11791 </pre>
11792 char int_n_sep_by_space
11793 <pre>
11794 Set to a value indicating the separation of the int_curr_symbol, the
11795 sign string, and the value for a negative internationally formatted monetary
11796 quantity.
11797 </pre>
11798 char int_p_sign_posn
11799 <pre>
11800 Set to a value indicating the positioning of the positive_sign for a
11801 nonnegative internationally formatted monetary quantity.
11802 </pre>
11803 char int_n_sign_posn
11804 <pre>
11805 Set to a value indicating the positioning of the negative_sign for a
11806 negative internationally formatted monetary quantity.
11807 </pre>
11808 <p><!--para 4 -->
11809 The elements of grouping and mon_grouping are interpreted according to the
11810 following:
11811 CHAR_MAX No further grouping is to be performed.
11812 0 The previous element is to be repeatedly used for the remainder of the
11813 <pre>
11814 digits.
11815 </pre>
11816 other The integer value is the number of digits that compose the current group.
11817 <pre>
11818 The next element is examined to determine the size of the next group of
11819 digits before the current group.
11820 </pre>
11821 <p><!--para 5 -->
11822 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
11823 and int_n_sep_by_space are interpreted according to the following:
11824 0 No space separates the currency symbol and value.
11825 1 If the currency symbol and sign string are adjacent, a space separates them from the
11826 <pre>
11827 value; otherwise, a space separates the currency symbol from the value.
11828 </pre>
11829 2 If the currency symbol and sign string are adjacent, a space separates them;
11830 <pre>
11831 otherwise, a space separates the sign string from the value.
11832 </pre>
11833 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
11834 int_curr_symbol is used instead of a space.
11835 <p><!--para 6 -->
11836 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
11837 int_n_sign_posn are interpreted according to the following:
11838 0 Parentheses surround the quantity and currency symbol.
11839 1 The sign string precedes the quantity and currency symbol.
11840 2 The sign string succeeds the quantity and currency symbol.
11841 3 The sign string immediately precedes the currency symbol.
11842 4 The sign string immediately succeeds the currency symbol.
11843 <!--page 246 -->
11844 <p><!--para 7 -->
11845 The implementation shall behave as if no library function calls the localeconv
11846 function.
11847 <p><b>Returns</b>
11848 <p><!--para 8 -->
11849 The localeconv function returns a pointer to the filled-in object. The structure
11850 pointed to by the return value shall not be modified by the program, but may be
11851 overwritten by a subsequent call to the localeconv function. In addition, calls to the
11852 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
11853 overwrite the contents of the structure.
11854 <p><!--para 9 -->
11855 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
11856 monetary quantities.
11857 <pre>
11858 Local format International format
11859 </pre>
11861 Country Positive Negative Positive Negative
11863 Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
11864 Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
11865 Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
11866 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
11867 <p><!--para 10 -->
11868 For these four countries, the respective values for the monetary members of the structure returned by
11869 localeconv could be:
11870 <pre>
11871 Country1 Country2 Country3 Country4
11872 </pre>
11880 frac_digits 2 0 2 2
11881 p_cs_precedes 0 1 1 1
11882 n_cs_precedes 0 1 1 1
11883 p_sep_by_space 1 0 1 0
11884 n_sep_by_space 1 0 2 0
11885 p_sign_posn 1 1 1 1
11886 n_sign_posn 1 1 4 2
11888 int_frac_digits 2 0 2 2
11889 int_p_cs_precedes 1 1 1 1
11890 int_n_cs_precedes 1 1 1 1
11891 int_p_sep_by_space 1 1 1 1
11892 int_n_sep_by_space 2 1 2 1
11893 int_p_sign_posn 1 1 1 1
11894 int_n_sign_posn 4 1 4 2
11895 <!--page 247 -->
11896 <p><!--para 11 -->
11897 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
11898 affect the formatted value.
11899 <pre>
11900 p_sep_by_space
11901 </pre>
11903 p_cs_precedes p_sign_posn 0 1 2
11905 <pre>
11911 </pre>
11913 <!--page 248 -->
11914 <pre>
11920 </pre>
11923 <p><!--para 1 -->
11924 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
11925 several macros. Most synopses specify a family of functions consisting of a principal
11926 function with one or more double parameters, a double return value, or both; and
11927 other functions with the same name but with f and l suffixes, which are corresponding
11928 functions with float and long double parameters, return values, or both.<sup><a href="#note223"><b>223)</b></a></sup>
11929 Integer arithmetic functions and conversion functions are discussed later.
11930 <p><!--para 2 -->
11931 The types
11932 <pre>
11933 float_t
11934 double_t
11935 </pre>
11936 are floating types at least as wide as float and double, respectively, and such that
11937 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
11938 float_t and double_t are float and double, respectively; if
11939 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
11940 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
11942 <p><!--para 3 -->
11943 The macro
11944 <pre>
11945 HUGE_VAL
11946 </pre>
11947 expands to a positive double constant expression, not necessarily representable as a
11948 float. The macros
11949 <pre>
11950 HUGE_VALF
11951 HUGE_VALL
11952 </pre>
11953 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note225"><b>225)</b></a></sup>
11954 <p><!--para 4 -->
11955 The macro
11956 <pre>
11957 INFINITY
11958 </pre>
11959 expands to a constant expression of type float representing positive or unsigned
11960 infinity, if available; else to a positive constant of type float that overflows at
11964 <!--page 249 -->
11966 <p><!--para 5 -->
11967 The macro
11968 <pre>
11969 NAN
11970 </pre>
11971 is defined if and only if the implementation supports quiet NaNs for the float type. It
11972 expands to a constant expression of type float representing a quiet NaN.
11973 <p><!--para 6 -->
11974 The number classification macros
11975 <pre>
11976 FP_INFINITE
11977 FP_NAN
11978 FP_NORMAL
11979 FP_SUBNORMAL
11980 FP_ZERO
11981 </pre>
11982 represent the mutually exclusive kinds of floating-point values. They expand to integer
11983 constant expressions with distinct values. Additional implementation-defined floating-
11984 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
11985 may also be specified by the implementation.
11986 <p><!--para 7 -->
11987 The macro
11988 <pre>
11989 FP_FAST_FMA
11990 </pre>
11991 is optionally defined. If defined, it indicates that the fma function generally executes
11992 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
11993 macros
11994 <pre>
11995 FP_FAST_FMAF
11996 FP_FAST_FMAL
11997 </pre>
11998 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
11999 these macros expand to the integer constant 1.
12000 <p><!--para 8 -->
12001 The macros
12002 <pre>
12003 FP_ILOGB0
12004 FP_ILOGBNAN
12005 </pre>
12006 expand to integer constant expressions whose values are returned by ilogb(x) if x is
12007 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
12008 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
12011 <!--page 250 -->
12012 <p><!--para 9 -->
12013 The macros
12014 <pre>
12015 MATH_ERRNO
12016 MATH_ERREXCEPT
12017 </pre>
12018 expand to the integer constants 1 and 2, respectively; the macro
12019 <pre>
12020 math_errhandling
12021 </pre>
12022 expands to an expression that has type int and the value MATH_ERRNO,
12023 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
12024 constant for the duration of the program. It is unspecified whether
12025 math_errhandling is a macro or an identifier with external linkage. If a macro
12026 definition is suppressed or a program defines an identifier with the name
12027 math_errhandling, the behavior is undefined. If the expression
12028 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
12029 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
12032 <p><b>Footnotes</b>
12033 <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
12034 and return values in wider format than the synopsis prototype indicates.
12035 </small>
12036 <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
12037 least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
12038 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
12039 </small>
12040 <p><small><a name="note225" href="#note225">225)</a> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
12041 supports infinities.
12042 </small>
12043 <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.
12044 </small>
12045 <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
12046 directly with a hardware multiply-add instruction. Software implementations are expected to be
12047 substantially slower.
12048 </small>
12051 <p><!--para 1 -->
12052 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
12053 values of its input arguments, except where stated otherwise. Each function shall execute
12054 as if it were a single operation without raising SIGFPE and without generating any of the
12055 floating-point exceptions ''invalid'', ''divide-by-zero'', or ''overflow'' except to reflect
12056 the result of the function.
12057 <p><!--para 2 -->
12058 For all functions, a domain error occurs if an input argument is outside the domain over
12059 which the mathematical function is defined. The description of each function lists any
12060 required domain errors; an implementation may define additional domain errors, provided
12061 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note228"><b>228)</b></a></sup> On a
12062 domain error, the function returns an implementation-defined value; if the integer
12063 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
12064 errno acquires the value EDOM; if the integer expression math_errhandling &
12065 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
12066 <p><!--para 3 -->
12067 Similarly, a pole error (also known as a singularity or infinitary) occurs if the
12068 mathematical function has an exact infinite result as the finite input argument(s) are
12069 approached in the limit (for example, log(0.0)). The description of each function lists
12070 any required pole errors; an implementation may define additional pole errors, provided
12071 that such errors are consistent with the mathematical definition of the function. On a pole
12072 error, the function returns an implementation-defined value; if the integer expression
12075 <!--page 251 -->
12076 math_errhandling & MATH_ERRNO is nonzero, the integer expression errno
12077 acquires the value ERANGE; if the integer expression math_errhandling &
12078 MATH_ERREXCEPT is nonzero, the ''divide-by-zero'' floating-point exception is raised.
12079 <p><!--para 4 -->
12080 Likewise, a range error occurs if the mathematical result of the function cannot be
12081 represented in an object of the specified type, due to extreme magnitude.
12082 <p><!--para 5 -->
12083 A floating result overflows if the magnitude of the mathematical result is finite but so
12084 large that the mathematical result cannot be represented without extraordinary roundoff
12085 error in an object of the specified type. If a floating result overflows and default rounding
12086 is in effect, then the function returns the value of the macro HUGE_VAL, HUGE_VALF, or *
12087 HUGE_VALL according to the return type, with the same sign as the correct value of the
12088 function; if the integer expression math_errhandling & MATH_ERRNO is nonzero,
12089 the integer expression errno acquires the value ERANGE; if the integer expression
12090 math_errhandling & MATH_ERREXCEPT is nonzero, the ''overflow'' floating-
12091 point exception is raised.
12092 <p><!--para 6 -->
12093 The result underflows if the magnitude of the mathematical result is so small that the
12094 mathematical result cannot be represented, without extraordinary roundoff error, in an
12095 object of the specified type.<sup><a href="#note229"><b>229)</b></a></sup> If the result underflows, the function returns an
12096 implementation-defined value whose magnitude is no greater than the smallest
12097 normalized positive number in the specified type; if the integer expression
12098 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
12099 value ERANGE is implementation-defined; if the integer expression
12100 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
12101 floating-point exception is raised is implementation-defined.
12102 <p><!--para 7 -->
12103 If a domain, pole, or range error occurs and the integer expression
12104 math_errhandling & MATH_ERRNO is zero,<sup><a href="#note230"><b>230)</b></a></sup> then errno shall either be set to
12105 the value corresponding to the error or left unmodified. If no such error occurs, errno
12106 shall be left unmodified regardless of the setting of math_errhandling.
12111 <!--page 252 -->
12113 <p><b>Footnotes</b>
12114 <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
12115 error if the mathematical domain of the function does not include the infinity.
12116 </small>
12117 <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
12118 also ''flush-to-zero'' underflow.
12119 </small>
12120 <p><small><a name="note230" href="#note230">230)</a> Math errors are being indicated by the floating-point exception flags rather than by errno.
12121 </small>
12124 <p><b>Synopsis</b>
12125 <p><!--para 1 -->
12126 <pre>
12128 #pragma STDC FP_CONTRACT on-off-switch
12129 </pre>
12130 <p><b>Description</b>
12131 <p><!--para 2 -->
12132 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
12133 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
12134 either outside external declarations or preceding all explicit declarations and statements
12135 inside a compound statement. When outside external declarations, the pragma takes
12136 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
12137 the end of the translation unit. When inside a compound statement, the pragma takes
12138 effect from its occurrence until another FP_CONTRACT pragma is encountered
12139 (including within a nested compound statement), or until the end of the compound
12140 statement; at the end of a compound statement the state for the pragma is restored to its
12141 condition just before the compound statement. If this pragma is used in any other
12142 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
12143 implementation-defined.
12146 <p><!--para 1 -->
12147 In the synopses in this subclause, real-floating indicates that the argument shall be an
12148 expression of real floating type.
12151 <p><b>Synopsis</b>
12152 <p><!--para 1 -->
12153 <pre>
12155 int fpclassify(real-floating x);
12156 </pre>
12157 <p><b>Description</b>
12158 <p><!--para 2 -->
12159 The fpclassify macro classifies its argument value as NaN, infinite, normal,
12160 subnormal, zero, or into another implementation-defined category. First, an argument
12161 represented in a format wider than its semantic type is converted to its semantic type.
12162 Then classification is based on the type of the argument.<sup><a href="#note231"><b>231)</b></a></sup>
12163 <p><b>Returns</b>
12164 <p><!--para 3 -->
12165 The fpclassify macro returns the value of the number classification macro
12166 appropriate to the value of its argument. *
12169 <!--page 253 -->
12171 <p><b>Footnotes</b>
12172 <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
12173 know the type that classification is based on. For example, a normal long double value might
12174 become subnormal when converted to double, and zero when converted to float.
12175 </small>
12178 <p><b>Synopsis</b>
12179 <p><!--para 1 -->
12180 <pre>
12182 int isfinite(real-floating x);
12183 </pre>
12184 <p><b>Description</b>
12185 <p><!--para 2 -->
12186 The isfinite macro determines whether its argument has a finite value (zero,
12187 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
12188 format wider than its semantic type is converted to its semantic type. Then determination
12189 is based on the type of the argument.
12190 <p><b>Returns</b>
12191 <p><!--para 3 -->
12192 The isfinite macro returns a nonzero value if and only if its argument has a finite
12193 value.
12196 <p><b>Synopsis</b>
12197 <p><!--para 1 -->
12198 <pre>
12200 int isinf(real-floating x);
12201 </pre>
12202 <p><b>Description</b>
12203 <p><!--para 2 -->
12204 The isinf macro determines whether its argument value is an infinity (positive or
12205 negative). First, an argument represented in a format wider than its semantic type is
12206 converted to its semantic type. Then determination is based on the type of the argument.
12207 <p><b>Returns</b>
12208 <p><!--para 3 -->
12209 The isinf macro returns a nonzero value if and only if its argument has an infinite
12210 value.
12213 <p><b>Synopsis</b>
12214 <p><!--para 1 -->
12215 <pre>
12217 int isnan(real-floating x);
12218 </pre>
12219 <p><b>Description</b>
12220 <p><!--para 2 -->
12221 The isnan macro determines whether its argument value is a NaN. First, an argument
12222 represented in a format wider than its semantic type is converted to its semantic type.
12223 Then determination is based on the type of the argument.<sup><a href="#note232"><b>232)</b></a></sup>
12226 <!--page 254 -->
12227 <p><b>Returns</b>
12228 <p><!--para 3 -->
12229 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
12231 <p><b>Footnotes</b>
12232 <p><small><a name="note232" href="#note232">232)</a> For the isnan macro, the type for determination does not matter unless the implementation supports
12233 NaNs in the evaluation type but not in the semantic type.
12234 </small>
12237 <p><b>Synopsis</b>
12238 <p><!--para 1 -->
12239 <pre>
12241 int isnormal(real-floating x);
12242 </pre>
12243 <p><b>Description</b>
12244 <p><!--para 2 -->
12245 The isnormal macro determines whether its argument value is normal (neither zero,
12246 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
12247 semantic type is converted to its semantic type. Then determination is based on the type
12248 of the argument.
12249 <p><b>Returns</b>
12250 <p><!--para 3 -->
12251 The isnormal macro returns a nonzero value if and only if its argument has a normal
12252 value.
12255 <p><b>Synopsis</b>
12256 <p><!--para 1 -->
12257 <pre>
12259 int signbit(real-floating x);
12260 </pre>
12261 <p><b>Description</b>
12262 <p><!--para 2 -->
12263 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note233"><b>233)</b></a></sup>
12264 <p><b>Returns</b>
12265 <p><!--para 3 -->
12266 The signbit macro returns a nonzero value if and only if the sign of its argument value
12267 is negative.
12272 <!--page 255 -->
12274 <p><b>Footnotes</b>
12275 <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
12276 unsigned, it is treated as positive.
12277 </small>
12282 <p><b>Synopsis</b>
12283 <p><!--para 1 -->
12284 <pre>
12286 double acos(double x);
12287 float acosf(float x);
12288 long double acosl(long double x);
12289 </pre>
12290 <p><b>Description</b>
12291 <p><!--para 2 -->
12292 The acos functions compute the principal value of the arc cosine of x. A domain error
12293 occurs for arguments not in the interval [-1, +1].
12294 <p><b>Returns</b>
12295 <p><!--para 3 -->
12296 The acos functions return arccos x in the interval [0, pi ] radians.
12299 <p><b>Synopsis</b>
12300 <p><!--para 1 -->
12301 <pre>
12303 double asin(double x);
12304 float asinf(float x);
12305 long double asinl(long double x);
12306 </pre>
12307 <p><b>Description</b>
12308 <p><!--para 2 -->
12309 The asin functions compute the principal value of the arc sine of x. A domain error
12310 occurs for arguments not in the interval [-1, +1].
12311 <p><b>Returns</b>
12312 <p><!--para 3 -->
12313 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
12316 <p><b>Synopsis</b>
12317 <p><!--para 1 -->
12318 <pre>
12320 double atan(double x);
12321 float atanf(float x);
12322 long double atanl(long double x);
12323 </pre>
12324 <p><b>Description</b>
12325 <p><!--para 2 -->
12326 The atan functions compute the principal value of the arc tangent of x.
12327 <!--page 256 -->
12328 <p><b>Returns</b>
12329 <p><!--para 3 -->
12330 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
12333 <p><b>Synopsis</b>
12334 <p><!--para 1 -->
12335 <pre>
12337 double atan2(double y, double x);
12338 float atan2f(float y, float x);
12339 long double atan2l(long double y, long double x);
12340 </pre>
12341 <p><b>Description</b>
12342 <p><!--para 2 -->
12343 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
12344 arguments to determine the quadrant of the return value. A domain error may occur if
12345 both arguments are zero.
12346 <p><b>Returns</b>
12347 <p><!--para 3 -->
12348 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
12351 <p><b>Synopsis</b>
12352 <p><!--para 1 -->
12353 <pre>
12355 double cos(double x);
12356 float cosf(float x);
12357 long double cosl(long double x);
12358 </pre>
12359 <p><b>Description</b>
12360 <p><!--para 2 -->
12361 The cos functions compute the cosine of x (measured in radians).
12362 <p><b>Returns</b>
12363 <p><!--para 3 -->
12364 The cos functions return cos x.
12367 <p><b>Synopsis</b>
12368 <p><!--para 1 -->
12369 <pre>
12371 double sin(double x);
12372 float sinf(float x);
12373 long double sinl(long double x);
12374 </pre>
12375 <p><b>Description</b>
12376 <p><!--para 2 -->
12377 The sin functions compute the sine of x (measured in radians).
12378 <!--page 257 -->
12379 <p><b>Returns</b>
12380 <p><!--para 3 -->
12381 The sin functions return sin x.
12384 <p><b>Synopsis</b>
12385 <p><!--para 1 -->
12386 <pre>
12388 double tan(double x);
12389 float tanf(float x);
12390 long double tanl(long double x);
12391 </pre>
12392 <p><b>Description</b>
12393 <p><!--para 2 -->
12394 The tan functions return the tangent of x (measured in radians).
12395 <p><b>Returns</b>
12396 <p><!--para 3 -->
12397 The tan functions return tan x.
12402 <p><b>Synopsis</b>
12403 <p><!--para 1 -->
12404 <pre>
12406 double acosh(double x);
12407 float acoshf(float x);
12408 long double acoshl(long double x);
12409 </pre>
12410 <p><b>Description</b>
12411 <p><!--para 2 -->
12412 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
12413 error occurs for arguments less than 1.
12414 <p><b>Returns</b>
12415 <p><!--para 3 -->
12416 The acosh functions return arcosh x in the interval [0, +(inf)].
12419 <p><b>Synopsis</b>
12420 <p><!--para 1 -->
12421 <pre>
12423 double asinh(double x);
12424 float asinhf(float x);
12425 long double asinhl(long double x);
12426 </pre>
12427 <p><b>Description</b>
12428 <p><!--para 2 -->
12429 The asinh functions compute the arc hyperbolic sine of x.
12430 <!--page 258 -->
12431 <p><b>Returns</b>
12432 <p><!--para 3 -->
12433 The asinh functions return arsinh x.
12436 <p><b>Synopsis</b>
12437 <p><!--para 1 -->
12438 <pre>
12440 double atanh(double x);
12441 float atanhf(float x);
12442 long double atanhl(long double x);
12443 </pre>
12444 <p><b>Description</b>
12445 <p><!--para 2 -->
12446 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
12447 for arguments not in the interval [-1, +1]. A pole error may occur if the argument equals
12448 -1 or +1.
12449 <p><b>Returns</b>
12450 <p><!--para 3 -->
12451 The atanh functions return artanh x.
12454 <p><b>Synopsis</b>
12455 <p><!--para 1 -->
12456 <pre>
12458 double cosh(double x);
12459 float coshf(float x);
12460 long double coshl(long double x);
12461 </pre>
12462 <p><b>Description</b>
12463 <p><!--para 2 -->
12464 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
12465 magnitude of x is too large.
12466 <p><b>Returns</b>
12467 <p><!--para 3 -->
12468 The cosh functions return cosh x.
12471 <p><b>Synopsis</b>
12472 <p><!--para 1 -->
12473 <pre>
12475 double sinh(double x);
12476 float sinhf(float x);
12477 long double sinhl(long double x);
12478 </pre>
12479 <p><b>Description</b>
12480 <p><!--para 2 -->
12481 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
12482 magnitude of x is too large.
12483 <!--page 259 -->
12484 <p><b>Returns</b>
12485 <p><!--para 3 -->
12486 The sinh functions return sinh x.
12489 <p><b>Synopsis</b>
12490 <p><!--para 1 -->
12491 <pre>
12493 double tanh(double x);
12494 float tanhf(float x);
12495 long double tanhl(long double x);
12496 </pre>
12497 <p><b>Description</b>
12498 <p><!--para 2 -->
12499 The tanh functions compute the hyperbolic tangent of x.
12500 <p><b>Returns</b>
12501 <p><!--para 3 -->
12502 The tanh functions return tanh x.
12507 <p><b>Synopsis</b>
12508 <p><!--para 1 -->
12509 <pre>
12511 double exp(double x);
12512 float expf(float x);
12513 long double expl(long double x);
12514 </pre>
12515 <p><b>Description</b>
12516 <p><!--para 2 -->
12517 The exp functions compute the base-e exponential of x. A range error occurs if the
12518 magnitude of x is too large.
12519 <p><b>Returns</b>
12520 <p><!--para 3 -->
12521 The exp functions return ex .
12524 <p><b>Synopsis</b>
12525 <p><!--para 1 -->
12526 <pre>
12528 double exp2(double x);
12529 float exp2f(float x);
12530 long double exp2l(long double x);
12531 </pre>
12532 <p><b>Description</b>
12533 <p><!--para 2 -->
12534 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
12535 magnitude of x is too large.
12536 <!--page 260 -->
12537 <p><b>Returns</b>
12538 <p><!--para 3 -->
12539 The exp2 functions return 2x .
12542 <p><b>Synopsis</b>
12543 <p><!--para 1 -->
12544 <pre>
12546 double expm1(double x);
12547 float expm1f(float x);
12548 long double expm1l(long double x);
12549 </pre>
12550 <p><b>Description</b>
12551 <p><!--para 2 -->
12552 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
12554 <p><b>Returns</b>
12555 <p><!--para 3 -->
12556 The expm1 functions return ex - 1.
12558 <p><b>Footnotes</b>
12559 <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.
12560 </small>
12563 <p><b>Synopsis</b>
12564 <p><!--para 1 -->
12565 <pre>
12567 double frexp(double value, int *exp);
12568 float frexpf(float value, int *exp);
12569 long double frexpl(long double value, int *exp);
12570 </pre>
12571 <p><b>Description</b>
12572 <p><!--para 2 -->
12573 The frexp functions break a floating-point number into a normalized fraction and an
12574 integral power of 2. They store the integer in the int object pointed to by exp.
12575 <p><b>Returns</b>
12576 <p><!--para 3 -->
12577 If value is not a floating-point number or if the integral power of 2 is outside the range
12578 of int, the results are unspecified. Otherwise, the frexp functions return the value x,
12579 such that x has a magnitude in the interval [1/2, 1) or zero, and value equals x x 2*exp .
12580 If value is zero, both parts of the result are zero.
12585 <!--page 261 -->
12588 <p><b>Synopsis</b>
12589 <p><!--para 1 -->
12590 <pre>
12592 int ilogb(double x);
12593 int ilogbf(float x);
12594 int ilogbl(long double x);
12595 </pre>
12596 <p><b>Description</b>
12597 <p><!--para 2 -->
12598 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
12599 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
12600 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
12601 the corresponding logb function and casting the returned value to type int. A domain
12602 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
12603 the range of the return type, the numeric result is unspecified.
12604 <p><b>Returns</b>
12605 <p><!--para 3 -->
12606 The ilogb functions return the exponent of x as a signed int value.
12610 <p><b>Synopsis</b>
12611 <p><!--para 1 -->
12612 <pre>
12614 double ldexp(double x, int exp);
12615 float ldexpf(float x, int exp);
12616 long double ldexpl(long double x, int exp);
12617 </pre>
12618 <p><b>Description</b>
12619 <p><!--para 2 -->
12620 The ldexp functions multiply a floating-point number by an integral power of 2. A
12621 range error may occur.
12622 <p><b>Returns</b>
12623 <p><!--para 3 -->
12624 The ldexp functions return x x 2exp .
12627 <p><b>Synopsis</b>
12628 <p><!--para 1 -->
12629 <!--page 262 -->
12630 <pre>
12632 double log(double x);
12633 float logf(float x);
12634 long double logl(long double x);
12635 </pre>
12636 <p><b>Description</b>
12637 <p><!--para 2 -->
12638 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
12639 the argument is negative. A pole error may occur if the argument is zero.
12640 <p><b>Returns</b>
12641 <p><!--para 3 -->
12642 The log functions return loge x.
12645 <p><b>Synopsis</b>
12646 <p><!--para 1 -->
12647 <pre>
12649 double log10(double x);
12650 float log10f(float x);
12651 long double log10l(long double x);
12652 </pre>
12653 <p><b>Description</b>
12654 <p><!--para 2 -->
12655 The log10 functions compute the base-10 (common) logarithm of x. A domain error
12656 occurs if the argument is negative. A pole error may occur if the argument is zero.
12657 <p><b>Returns</b>
12658 <p><!--para 3 -->
12659 The log10 functions return log10 x.
12662 <p><b>Synopsis</b>
12663 <p><!--para 1 -->
12664 <pre>
12666 double log1p(double x);
12667 float log1pf(float x);
12668 long double log1pl(long double x);
12669 </pre>
12670 <p><b>Description</b>
12671 <p><!--para 2 -->
12672 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note235"><b>235)</b></a></sup>
12673 A domain error occurs if the argument is less than -1. A pole error may occur if the
12674 argument equals -1.
12675 <p><b>Returns</b>
12676 <p><!--para 3 -->
12677 The log1p functions return loge (1 + x).
12682 <!--page 263 -->
12684 <p><b>Footnotes</b>
12685 <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).
12686 </small>
12689 <p><b>Synopsis</b>
12690 <p><!--para 1 -->
12691 <pre>
12693 double log2(double x);
12694 float log2f(float x);
12695 long double log2l(long double x);
12696 </pre>
12697 <p><b>Description</b>
12698 <p><!--para 2 -->
12699 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
12700 argument is less than zero. A pole error may occur if the argument is zero.
12701 <p><b>Returns</b>
12702 <p><!--para 3 -->
12703 The log2 functions return log2 x.
12706 <p><b>Synopsis</b>
12707 <p><!--para 1 -->
12708 <pre>
12710 double logb(double x);
12711 float logbf(float x);
12712 long double logbl(long double x);
12713 </pre>
12714 <p><b>Description</b>
12715 <p><!--para 2 -->
12716 The logb functions extract the exponent of x, as a signed integer value in floating-point
12717 format. If x is subnormal it is treated as though it were normalized; thus, for positive
12718 finite x,
12719 <pre>
12720 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX
12721 </pre>
12722 A domain error or pole error may occur if the argument is zero.
12723 <p><b>Returns</b>
12724 <p><!--para 3 -->
12725 The logb functions return the signed exponent of x.
12728 <p><b>Synopsis</b>
12729 <p><!--para 1 -->
12730 <pre>
12732 double modf(double value, double *iptr);
12733 float modff(float value, float *iptr);
12734 long double modfl(long double value, long double *iptr);
12735 </pre>
12736 <p><b>Description</b>
12737 <p><!--para 2 -->
12738 The modf functions break the argument value into integral and fractional parts, each of
12739 which has the same type and sign as the argument. They store the integral part (in
12740 <!--page 264 -->
12741 floating-point format) in the object pointed to by iptr.
12742 <p><b>Returns</b>
12743 <p><!--para 3 -->
12744 The modf functions return the signed fractional part of value.
12747 <p><b>Synopsis</b>
12748 <p><!--para 1 -->
12749 <pre>
12751 double scalbn(double x, int n);
12752 float scalbnf(float x, int n);
12753 long double scalbnl(long double x, int n);
12754 double scalbln(double x, long int n);
12755 float scalblnf(float x, long int n);
12756 long double scalblnl(long double x, long int n);
12757 </pre>
12758 <p><b>Description</b>
12759 <p><!--para 2 -->
12760 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
12761 normally by computing FLT_RADIXn explicitly. A range error may occur.
12762 <p><b>Returns</b>
12763 <p><!--para 3 -->
12764 The scalbn and scalbln functions return x x FLT_RADIXn .
12769 <p><b>Synopsis</b>
12770 <p><!--para 1 -->
12771 <pre>
12773 double cbrt(double x);
12774 float cbrtf(float x);
12775 long double cbrtl(long double x);
12776 </pre>
12777 <p><b>Description</b>
12778 <p><!--para 2 -->
12779 The cbrt functions compute the real cube root of x.
12780 <p><b>Returns</b>
12781 <p><!--para 3 -->
12782 The cbrt functions return x1/3 .
12783 <!--page 265 -->
12786 <p><b>Synopsis</b>
12787 <p><!--para 1 -->
12788 <pre>
12790 double fabs(double x);
12791 float fabsf(float x);
12792 long double fabsl(long double x);
12793 </pre>
12794 <p><b>Description</b>
12795 <p><!--para 2 -->
12796 The fabs functions compute the absolute value of a floating-point number x.
12797 <p><b>Returns</b>
12798 <p><!--para 3 -->
12799 The fabs functions return | x |.
12802 <p><b>Synopsis</b>
12803 <p><!--para 1 -->
12804 <pre>
12806 double hypot(double x, double y);
12807 float hypotf(float x, float y);
12808 long double hypotl(long double x, long double y);
12809 </pre>
12810 <p><b>Description</b>
12811 <p><!--para 2 -->
12812 The hypot functions compute the square root of the sum of the squares of x and y,
12813 without undue overflow or underflow. A range error may occur.
12814 <p><!--para 3 -->
12815 <p><b>Returns</b>
12816 <p><!--para 4 -->
12817 The hypot functions return (sqrt)x2 + y2 .
12818 <pre>
12819 -
12820 -----
12821 </pre>
12824 <p><b>Synopsis</b>
12825 <p><!--para 1 -->
12826 <pre>
12828 double pow(double x, double y);
12829 float powf(float x, float y);
12830 long double powl(long double x, long double y);
12831 </pre>
12832 <p><b>Description</b>
12833 <p><!--para 2 -->
12834 The pow functions compute x raised to the power y. A domain error occurs if x is finite
12835 and negative and y is finite and not an integer value. A range error may occur. A domain
12836 error may occur if x is zero and y is zero. A domain error or pole error may occur if x is
12837 zero and y is less than zero.
12838 <!--page 266 -->
12839 <p><b>Returns</b>
12840 <p><!--para 3 -->
12841 The pow functions return xy .
12844 <p><b>Synopsis</b>
12845 <p><!--para 1 -->
12846 <pre>
12848 double sqrt(double x);
12849 float sqrtf(float x);
12850 long double sqrtl(long double x);
12851 </pre>
12852 <p><b>Description</b>
12853 <p><!--para 2 -->
12854 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
12855 the argument is less than zero.
12856 <p><b>Returns</b>
12857 <p><!--para 3 -->
12858 The sqrt functions return (sqrt)x.
12859 <pre>
12860 -
12861 -
12862 </pre>
12867 <p><b>Synopsis</b>
12868 <p><!--para 1 -->
12869 <pre>
12871 double erf(double x);
12872 float erff(float x);
12873 long double erfl(long double x);
12874 </pre>
12875 <p><b>Description</b>
12876 <p><!--para 2 -->
12877 The erf functions compute the error function of x.
12878 <p><b>Returns</b>
12879 <p><!--para 3 -->
12880 <pre>
12881 2 x
12882 (integral) e-t dt.
12883 2
12884 </pre>
12885 The erf functions return erf x =
12886 <pre>
12887 (sqrt)pi
12888 -
12889 - 0
12890 </pre>
12894 <p><b>Synopsis</b>
12895 <p><!--para 1 -->
12896 <pre>
12898 double erfc(double x);
12899 float erfcf(float x);
12900 long double erfcl(long double x);
12901 </pre>
12902 <p><b>Description</b>
12903 <p><!--para 2 -->
12904 The erfc functions compute the complementary error function of x. A range error
12905 occurs if x is too large.
12906 <!--page 267 -->
12907 <p><b>Returns</b>
12908 <p><!--para 3 -->
12909 <pre>
12910 2 (inf)
12911 (integral) e-t dt.
12912 2
12913 </pre>
12914 The erfc functions return erfc x = 1 - erf x =
12915 <pre>
12916 (sqrt)pi
12917 -
12918 - x
12919 </pre>
12923 <p><b>Synopsis</b>
12924 <p><!--para 1 -->
12925 <pre>
12927 double lgamma(double x);
12928 float lgammaf(float x);
12929 long double lgammal(long double x);
12930 </pre>
12931 <p><b>Description</b>
12932 <p><!--para 2 -->
12933 The lgamma functions compute the natural logarithm of the absolute value of gamma of
12934 x. A range error occurs if x is too large. A pole error may occur if x is a negative integer
12935 or zero.
12936 <p><b>Returns</b>
12937 <p><!--para 3 -->
12938 The lgamma functions return loge | (Gamma)(x) |.
12941 <p><b>Synopsis</b>
12942 <p><!--para 1 -->
12943 <pre>
12945 double tgamma(double x);
12946 float tgammaf(float x);
12947 long double tgammal(long double x);
12948 </pre>
12949 <p><b>Description</b>
12950 <p><!--para 2 -->
12951 The tgamma functions compute the gamma function of x. A domain error or pole error
12952 may occur if x is a negative integer or zero. A range error occurs if the magnitude of x is
12953 too large and may occur if the magnitude of x is too small.
12954 <p><b>Returns</b>
12955 <p><!--para 3 -->
12956 The tgamma functions return (Gamma)(x).
12957 <!--page 268 -->
12962 <p><b>Synopsis</b>
12963 <p><!--para 1 -->
12964 <pre>
12966 double ceil(double x);
12967 float ceilf(float x);
12968 long double ceill(long double x);
12969 </pre>
12970 <p><b>Description</b>
12971 <p><!--para 2 -->
12972 The ceil functions compute the smallest integer value not less than x.
12973 <p><b>Returns</b>
12974 <p><!--para 3 -->
12975 The ceil functions return [^x^], expressed as a floating-point number.
12978 <p><b>Synopsis</b>
12979 <p><!--para 1 -->
12980 <pre>
12982 double floor(double x);
12983 float floorf(float x);
12984 long double floorl(long double x);
12985 </pre>
12986 <p><b>Description</b>
12987 <p><!--para 2 -->
12988 The floor functions compute the largest integer value not greater than x.
12989 <p><b>Returns</b>
12990 <p><!--para 3 -->
12991 The floor functions return [_x_], expressed as a floating-point number.
12994 <p><b>Synopsis</b>
12995 <p><!--para 1 -->
12996 <pre>
12998 double nearbyint(double x);
12999 float nearbyintf(float x);
13000 long double nearbyintl(long double x);
13001 </pre>
13002 <p><b>Description</b>
13003 <p><!--para 2 -->
13004 The nearbyint functions round their argument to an integer value in floating-point
13005 format, using the current rounding direction and without raising the ''inexact'' floating-
13006 point exception.
13007 <!--page 269 -->
13008 <p><b>Returns</b>
13009 <p><!--para 3 -->
13010 The nearbyint functions return the rounded integer value.
13013 <p><b>Synopsis</b>
13014 <p><!--para 1 -->
13015 <pre>
13017 double rint(double x);
13018 float rintf(float x);
13019 long double rintl(long double x);
13020 </pre>
13021 <p><b>Description</b>
13022 <p><!--para 2 -->
13023 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
13024 rint functions may raise the ''inexact'' floating-point exception if the result differs in
13025 value from the argument.
13026 <p><b>Returns</b>
13027 <p><!--para 3 -->
13028 The rint functions return the rounded integer value.
13031 <p><b>Synopsis</b>
13032 <p><!--para 1 -->
13033 <pre>
13035 long int lrint(double x);
13036 long int lrintf(float x);
13037 long int lrintl(long double x);
13038 long long int llrint(double x);
13039 long long int llrintf(float x);
13040 long long int llrintl(long double x);
13041 </pre>
13042 <p><b>Description</b>
13043 <p><!--para 2 -->
13044 The lrint and llrint functions round their argument to the nearest integer value,
13045 rounding according to the current rounding direction. If the rounded value is outside the
13046 range of the return type, the numeric result is unspecified and a domain error or range
13047 error may occur.
13048 <p><b>Returns</b>
13049 <p><!--para 3 -->
13050 The lrint and llrint functions return the rounded integer value.
13051 <!--page 270 -->
13054 <p><b>Synopsis</b>
13055 <p><!--para 1 -->
13056 <pre>
13058 double round(double x);
13059 float roundf(float x);
13060 long double roundl(long double x);
13061 </pre>
13062 <p><b>Description</b>
13063 <p><!--para 2 -->
13064 The round functions round their argument to the nearest integer value in floating-point
13065 format, rounding halfway cases away from zero, regardless of the current rounding
13066 direction.
13067 <p><b>Returns</b>
13068 <p><!--para 3 -->
13069 The round functions return the rounded integer value.
13072 <p><b>Synopsis</b>
13073 <p><!--para 1 -->
13074 <pre>
13076 long int lround(double x);
13077 long int lroundf(float x);
13078 long int lroundl(long double x);
13079 long long int llround(double x);
13080 long long int llroundf(float x);
13081 long long int llroundl(long double x);
13082 </pre>
13083 <p><b>Description</b>
13084 <p><!--para 2 -->
13085 The lround and llround functions round their argument to the nearest integer value,
13086 rounding halfway cases away from zero, regardless of the current rounding direction. If
13087 the rounded value is outside the range of the return type, the numeric result is unspecified
13088 and a domain error or range error may occur.
13089 <p><b>Returns</b>
13090 <p><!--para 3 -->
13091 The lround and llround functions return the rounded integer value.
13094 <p><b>Synopsis</b>
13095 <p><!--para 1 -->
13096 <!--page 271 -->
13097 <pre>
13099 double trunc(double x);
13100 float truncf(float x);
13101 long double truncl(long double x);
13102 </pre>
13103 <p><b>Description</b>
13104 <p><!--para 2 -->
13105 The trunc functions round their argument to the integer value, in floating format,
13106 nearest to but no larger in magnitude than the argument.
13107 <p><b>Returns</b>
13108 <p><!--para 3 -->
13109 The trunc functions return the truncated integer value.
13114 <p><b>Synopsis</b>
13115 <p><!--para 1 -->
13116 <pre>
13118 double fmod(double x, double y);
13119 float fmodf(float x, float y);
13120 long double fmodl(long double x, long double y);
13121 </pre>
13122 <p><b>Description</b>
13123 <p><!--para 2 -->
13124 The fmod functions compute the floating-point remainder of x/y.
13125 <p><b>Returns</b>
13126 <p><!--para 3 -->
13127 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
13128 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
13129 whether a domain error occurs or the fmod functions return zero is implementation-
13130 defined.
13133 <p><b>Synopsis</b>
13134 <p><!--para 1 -->
13135 <pre>
13137 double remainder(double x, double y);
13138 float remainderf(float x, float y);
13139 long double remainderl(long double x, long double y);
13140 </pre>
13141 <p><b>Description</b>
13142 <p><!--para 2 -->
13143 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note236"><b>236)</b></a></sup>
13148 <!--page 272 -->
13149 <p><b>Returns</b>
13150 <p><!--para 3 -->
13151 The remainder functions return x REM y. If y is zero, whether a domain error occurs
13152 or the functions return zero is implementation defined.
13154 <p><b>Footnotes</b>
13155 <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
13156 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
13157 | n - x/y | = 1/2, then n is even. If r = 0, its sign shall be that of x.'' This definition is applicable for *
13158 all implementations.
13159 </small>
13162 <p><b>Synopsis</b>
13163 <p><!--para 1 -->
13164 <pre>
13166 double remquo(double x, double y, int *quo);
13167 float remquof(float x, float y, int *quo);
13168 long double remquol(long double x, long double y,
13169 int *quo);
13170 </pre>
13171 <p><b>Description</b>
13172 <p><!--para 2 -->
13173 The remquo functions compute the same remainder as the remainder functions. In
13174 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
13175 magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
13176 n is an implementation-defined integer greater than or equal to 3.
13177 <p><b>Returns</b>
13178 <p><!--para 3 -->
13179 The remquo functions return x REM y. If y is zero, the value stored in the object
13180 pointed to by quo is unspecified and whether a domain error occurs or the functions
13181 return zero is implementation defined.
13186 <p><b>Synopsis</b>
13187 <p><!--para 1 -->
13188 <pre>
13190 double copysign(double x, double y);
13191 float copysignf(float x, float y);
13192 long double copysignl(long double x, long double y);
13193 </pre>
13194 <p><b>Description</b>
13195 <p><!--para 2 -->
13196 The copysign functions produce a value with the magnitude of x and the sign of y.
13197 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
13198 represent a signed zero but do not treat negative zero consistently in arithmetic
13199 operations, the copysign functions regard the sign of zero as positive.
13200 <p><b>Returns</b>
13201 <p><!--para 3 -->
13202 The copysign functions return a value with the magnitude of x and the sign of y.
13203 <!--page 273 -->
13206 <p><b>Synopsis</b>
13207 <p><!--para 1 -->
13208 <pre>
13210 double nan(const char *tagp);
13211 float nanf(const char *tagp);
13212 long double nanl(const char *tagp);
13213 </pre>
13214 <p><b>Description</b>
13215 <p><!--para 2 -->
13220 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
13221 and strtold.
13222 <p><b>Returns</b>
13223 <p><!--para 3 -->
13224 The nan functions return a quiet NaN, if available, with content indicated through tagp.
13225 If the implementation does not support quiet NaNs, the functions return zero.
13226 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
13229 <p><b>Synopsis</b>
13230 <p><!--para 1 -->
13231 <pre>
13233 double nextafter(double x, double y);
13234 float nextafterf(float x, float y);
13235 long double nextafterl(long double x, long double y);
13236 </pre>
13237 <p><b>Description</b>
13238 <p><!--para 2 -->
13239 The nextafter functions determine the next representable value, in the type of the
13240 function, after x in the direction of y, where x and y are first converted to the type of the
13241 function.<sup><a href="#note237"><b>237)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
13242 if the magnitude of x is the largest finite value representable in the type and the result is
13243 infinite or not representable in the type.
13244 <p><b>Returns</b>
13245 <p><!--para 3 -->
13246 The nextafter functions return the next representable value in the specified format
13247 after x in the direction of y.
13250 <!--page 274 -->
13252 <p><b>Footnotes</b>
13253 <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
13254 function.
13255 </small>
13258 <p><b>Synopsis</b>
13259 <p><!--para 1 -->
13260 <pre>
13262 double nexttoward(double x, long double y);
13263 float nexttowardf(float x, long double y);
13264 long double nexttowardl(long double x, long double y);
13265 </pre>
13266 <p><b>Description</b>
13267 <p><!--para 2 -->
13268 The nexttoward functions are equivalent to the nextafter functions except that the
13269 second parameter has type long double and the functions return y converted to the
13272 <p><b>Footnotes</b>
13273 <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
13274 range or precision in a floating second argument.
13275 </small>
13277 <h4><a name="7.12.12" href="#7.12.12">7.12.12 Maximum, minimum, and positive difference functions</a></h4>
13280 <p><b>Synopsis</b>
13281 <p><!--para 1 -->
13282 <pre>
13284 double fdim(double x, double y);
13285 float fdimf(float x, float y);
13286 long double fdiml(long double x, long double y);
13287 </pre>
13288 <p><b>Description</b>
13289 <p><!--para 2 -->
13290 The fdim functions determine the positive difference between their arguments:
13291 <pre>
13292 {x - y if x > y
13293 {
13294 {+0 if x <= y
13295 </pre>
13296 A range error may occur.
13297 <p><b>Returns</b>
13298 <p><!--para 3 -->
13299 The fdim functions return the positive difference value.
13302 <p><b>Synopsis</b>
13303 <p><!--para 1 -->
13304 <pre>
13306 double fmax(double x, double y);
13307 float fmaxf(float x, float y);
13308 long double fmaxl(long double x, long double y);
13309 </pre>
13313 <!--page 275 -->
13314 <p><b>Description</b>
13315 <p><!--para 2 -->
13316 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note239"><b>239)</b></a></sup>
13317 <p><b>Returns</b>
13318 <p><!--para 3 -->
13319 The fmax functions return the maximum numeric value of their arguments.
13321 <p><b>Footnotes</b>
13322 <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
13324 </small>
13327 <p><b>Synopsis</b>
13328 <p><!--para 1 -->
13329 <pre>
13331 double fmin(double x, double y);
13332 float fminf(float x, float y);
13333 long double fminl(long double x, long double y);
13334 </pre>
13335 <p><b>Description</b>
13336 <p><!--para 2 -->
13337 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note240"><b>240)</b></a></sup>
13338 <p><b>Returns</b>
13339 <p><!--para 3 -->
13340 The fmin functions return the minimum numeric value of their arguments.
13342 <p><b>Footnotes</b>
13343 <p><small><a name="note240" href="#note240">240)</a> The fmin functions are analogous to the fmax functions in their treatment of NaNs.
13344 </small>
13349 <p><b>Synopsis</b>
13350 <p><!--para 1 -->
13351 <pre>
13353 double fma(double x, double y, double z);
13354 float fmaf(float x, float y, float z);
13355 long double fmal(long double x, long double y,
13356 long double z);
13357 </pre>
13358 <p><b>Description</b>
13359 <p><!--para 2 -->
13360 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
13361 the value (as if) to infinite precision and round once to the result format, according to the
13362 current rounding mode. A range error may occur.
13363 <p><b>Returns</b>
13364 <p><!--para 3 -->
13365 The fma functions return (x x y) + z, rounded as one ternary operation.
13370 <!--page 276 -->
13373 <p><!--para 1 -->
13374 The relational and equality operators support the usual mathematical relationships
13375 between numeric values. For any ordered pair of numeric values exactly one of the
13376 relationships -- less, greater, and equal -- is true. Relational operators may raise the
13377 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
13378 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note241"><b>241)</b></a></sup> The following
13379 subclauses provide macros that are quiet (non floating-point exception raising) versions
13380 of the relational operators, and other comparison macros that facilitate writing efficient
13381 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
13382 the synopses in this subclause, real-floating indicates that the argument shall be an
13383 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>
13385 <p><b>Footnotes</b>
13386 <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
13387 the operands compare unordered, as an error indicator for programs written without consideration of
13388 NaNs; the result in these cases is false.
13389 </small>
13390 <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
13391 undefined.
13392 </small>
13393 <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
13394 type is unspecified.
13395 </small>
13398 <p><b>Synopsis</b>
13399 <p><!--para 1 -->
13400 <pre>
13402 int isgreater(real-floating x, real-floating y);
13403 </pre>
13404 <p><b>Description</b>
13405 <p><!--para 2 -->
13406 The isgreater macro determines whether its first argument is greater than its second
13407 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
13408 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
13409 exception when x and y are unordered.
13410 <p><b>Returns</b>
13411 <p><!--para 3 -->
13412 The isgreater macro returns the value of (x) > (y).
13415 <p><b>Synopsis</b>
13416 <p><!--para 1 -->
13417 <pre>
13419 int isgreaterequal(real-floating x, real-floating y);
13420 </pre>
13425 <!--page 277 -->
13426 <p><b>Description</b>
13427 <p><!--para 2 -->
13428 The isgreaterequal macro determines whether its first argument is greater than or
13429 equal to its second argument. The value of isgreaterequal(x, y) is always equal
13430 to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
13431 not raise the ''invalid'' floating-point exception when x and y are unordered.
13432 <p><b>Returns</b>
13433 <p><!--para 3 -->
13434 The isgreaterequal macro returns the value of (x) >= (y).
13437 <p><b>Synopsis</b>
13438 <p><!--para 1 -->
13439 <pre>
13441 int isless(real-floating x, real-floating y);
13442 </pre>
13443 <p><b>Description</b>
13444 <p><!--para 2 -->
13445 The isless macro determines whether its first argument is less than its second
13446 argument. The value of isless(x, y) is always equal to (x) < (y); however,
13447 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
13448 exception when x and y are unordered.
13449 <p><b>Returns</b>
13450 <p><!--para 3 -->
13451 The isless macro returns the value of (x) < (y).
13454 <p><b>Synopsis</b>
13455 <p><!--para 1 -->
13456 <pre>
13458 int islessequal(real-floating x, real-floating y);
13459 </pre>
13460 <p><b>Description</b>
13461 <p><!--para 2 -->
13462 The islessequal macro determines whether its first argument is less than or equal to
13463 its second argument. The value of islessequal(x, y) is always equal to
13464 (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
13465 the ''invalid'' floating-point exception when x and y are unordered.
13466 <p><b>Returns</b>
13467 <p><!--para 3 -->
13468 The islessequal macro returns the value of (x) <= (y).
13469 <!--page 278 -->
13472 <p><b>Synopsis</b>
13473 <p><!--para 1 -->
13474 <pre>
13476 int islessgreater(real-floating x, real-floating y);
13477 </pre>
13478 <p><b>Description</b>
13479 <p><!--para 2 -->
13480 The islessgreater macro determines whether its first argument is less than or
13481 greater than its second argument. The islessgreater(x, y) macro is similar to
13482 (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
13483 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
13484 and y twice).
13485 <p><b>Returns</b>
13486 <p><!--para 3 -->
13487 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
13490 <p><b>Synopsis</b>
13491 <p><!--para 1 -->
13492 <pre>
13494 int isunordered(real-floating x, real-floating y);
13495 </pre>
13496 <p><b>Description</b>
13497 <p><!--para 2 -->
13498 The isunordered macro determines whether its arguments are unordered.
13499 <p><b>Returns</b>
13500 <p><!--para 3 -->
13501 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
13502 <!--page 279 -->
13505 <p><!--para 1 -->
13506 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
13507 one type, for bypassing the normal function call and return discipline.<sup><a href="#note244"><b>244)</b></a></sup>
13508 <p><!--para 2 -->
13509 The type declared is
13510 <pre>
13511 jmp_buf
13512 </pre>
13513 which is an array type suitable for holding the information needed to restore a calling
13514 environment. The environment of a call to the setjmp macro consists of information
13515 sufficient for a call to the longjmp function to return execution to the correct block and
13516 invocation of that block, were it called recursively. It does not include the state of the
13517 floating-point status flags, of open files, or of any other component of the abstract
13518 machine.
13519 <p><!--para 3 -->
13520 It is unspecified whether setjmp is a macro or an identifier declared with external
13521 linkage. If a macro definition is suppressed in order to access an actual function, or a
13522 program defines an external identifier with the name setjmp, the behavior is undefined.
13524 <p><b>Footnotes</b>
13525 <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
13526 a program.
13527 </small>
13532 <p><b>Synopsis</b>
13533 <p><!--para 1 -->
13534 <pre>
13536 int setjmp(jmp_buf env);
13537 </pre>
13538 <p><b>Description</b>
13539 <p><!--para 2 -->
13540 The setjmp macro saves its calling environment in its jmp_buf argument for later use
13541 by the longjmp function.
13542 <p><b>Returns</b>
13543 <p><!--para 3 -->
13544 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
13545 return is from a call to the longjmp function, the setjmp macro returns a nonzero
13546 value.
13547 <p><b>Environmental limits</b>
13548 <p><!--para 4 -->
13549 An invocation of the setjmp macro shall appear only in one of the following contexts:
13550 <ul>
13551 <li> the entire controlling expression of a selection or iteration statement;
13552 <li> one operand of a relational or equality operator with the other operand an integer
13553 constant expression, with the resulting expression being the entire controlling
13556 <!--page 280 -->
13557 expression of a selection or iteration statement;
13558 <li> the operand of a unary ! operator with the resulting expression being the entire
13559 controlling expression of a selection or iteration statement; or
13560 <li> the entire expression of an expression statement (possibly cast to void).
13561 </ul>
13562 <p><!--para 5 -->
13563 If the invocation appears in any other context, the behavior is undefined.
13568 <p><b>Synopsis</b>
13569 <p><!--para 1 -->
13570 <pre>
13572 _Noreturn void longjmp(jmp_buf env, int val);
13573 </pre>
13574 <p><b>Description</b>
13575 <p><!--para 2 -->
13576 The longjmp function restores the environment saved by the most recent invocation of
13577 the setjmp macro in the same invocation of the program with the corresponding
13578 jmp_buf argument. If there has been no such invocation, or if the function containing
13579 the invocation of the setjmp macro has terminated execution<sup><a href="#note245"><b>245)</b></a></sup> in the interim, or if the
13580 invocation of the setjmp macro was within the scope of an identifier with variably
13581 modified type and execution has left that scope in the interim, the behavior is undefined.
13582 <p><!--para 3 -->
13583 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note246"><b>246)</b></a></sup>
13584 have state, as of the time the longjmp function was called, except that the values of
13585 objects of automatic storage duration that are local to the function containing the
13586 invocation of the corresponding setjmp macro that do not have volatile-qualified type
13587 and have been changed between the setjmp invocation and longjmp call are
13588 indeterminate.
13589 <p><b>Returns</b>
13590 <p><!--para 4 -->
13591 After longjmp is completed, program execution continues as if the corresponding
13592 invocation of the setjmp macro had just returned the value specified by val. The
13593 longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
13594 the setjmp macro returns the value 1.
13595 <p><!--para 5 -->
13596 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
13597 might cause memory associated with a variable length array object to be squandered.
13602 <!--page 281 -->
13603 <!--page 282 -->
13604 <pre>
13606 jmp_buf buf;
13607 void g(int n);
13608 void h(int n);
13609 int n = 6;
13610 void f(void)
13611 {
13612 int x[n]; // valid: f is not terminated
13613 setjmp(buf);
13614 g(n);
13615 }
13616 void g(int n)
13617 {
13618 int a[n]; // a may remain allocated
13619 h(n);
13620 }
13621 void h(int n)
13622 {
13623 int b[n]; // b may remain allocated
13624 longjmp(buf, 2); // might cause memory loss
13625 }
13626 </pre>
13628 <p><b>Footnotes</b>
13629 <p><small><a name="note245" href="#note245">245)</a> For example, by executing a return statement or because another longjmp call has caused a
13630 transfer to a setjmp invocation in a function earlier in the set of nested calls.
13631 </small>
13632 <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.
13633 </small>
13636 <p><!--para 1 -->
13637 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
13638 for handling various signals (conditions that may be reported during program execution).
13639 <p><!--para 2 -->
13640 The type defined is
13641 <pre>
13642 sig_atomic_t
13643 </pre>
13644 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
13645 an atomic entity, even in the presence of asynchronous interrupts.
13646 <p><!--para 3 -->
13647 The macros defined are
13648 <pre>
13649 SIG_DFL
13650 SIG_ERR
13651 SIG_IGN
13652 </pre>
13653 which expand to constant expressions with distinct values that have type compatible with
13654 the second argument to, and the return value of, the signal function, and whose values
13655 compare unequal to the address of any declarable function; and the following, which
13656 expand to positive integer constant expressions with type int and distinct values that are
13657 the signal numbers, each corresponding to the specified condition:
13658 <pre>
13659 SIGABRT abnormal termination, such as is initiated by the abort function
13660 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
13661 resulting in overflow
13662 SIGILL detection of an invalid function image, such as an invalid instruction
13663 SIGINT receipt of an interactive attention signal
13664 SIGSEGV an invalid access to storage
13665 SIGTERM a termination request sent to the program
13666 </pre>
13667 <p><!--para 4 -->
13668 An implementation need not generate any of these signals, except as a result of explicit
13669 calls to the raise function. Additional signals and pointers to undeclarable functions,
13670 with macro definitions beginning, respectively, with the letters SIG and an uppercase
13671 letter or with SIG_ and an uppercase letter,<sup><a href="#note247"><b>247)</b></a></sup> may also be specified by the
13672 implementation. The complete set of signals, their semantics, and their default handling
13673 is implementation-defined; all signal numbers shall be positive.
13678 <!--page 283 -->
13680 <p><b>Footnotes</b>
13681 <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
13682 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
13683 and termination.
13684 </small>
13689 <p><b>Synopsis</b>
13690 <p><!--para 1 -->
13691 <pre>
13693 void (*signal(int sig, void (*func)(int)))(int);
13694 </pre>
13695 <p><b>Description</b>
13696 <p><!--para 2 -->
13697 The signal function chooses one of three ways in which receipt of the signal number
13698 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
13699 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
13700 Otherwise, func shall point to a function to be called when that signal occurs. An
13701 invocation of such a function because of a signal, or (recursively) of any further functions
13702 called by that invocation (other than functions in the standard library),<sup><a href="#note248"><b>248)</b></a></sup> is called a
13703 signal handler.
13704 <p><!--para 3 -->
13705 When a signal occurs and func points to a function, it is implementation-defined
13706 whether the equivalent of signal(sig, SIG_DFL); is executed or the
13707 implementation prevents some implementation-defined set of signals (at least including
13708 sig) from occurring until the current signal handling has completed; in the case of
13709 SIGILL, the implementation may alternatively define that no action is taken. Then the
13710 equivalent of (*func)(sig); is executed. If and when the function returns, if the
13711 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
13712 value corresponding to a computational exception, the behavior is undefined; otherwise
13713 the program will resume execution at the point it was interrupted.
13714 <p><!--para 4 -->
13715 If the signal occurs as the result of calling the abort or raise function, the signal
13716 handler shall not call the raise function.
13717 <p><!--para 5 -->
13718 If the signal occurs other than as the result of calling the abort or raise function, the
13719 behavior is undefined if the signal handler refers to any object with static or thread
13720 storage duration that is not a lock-free atomic object other than by assigning a value to an
13721 object declared as volatile sig_atomic_t, or the signal handler calls any function
13722 in the standard library other than the abort function, the _Exit function, the
13723 quick_exit function, or the signal function with the first argument equal to the
13724 signal number corresponding to the signal that caused the invocation of the handler.
13725 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
13729 <!--page 284 -->
13730 <p><!--para 6 -->
13731 At program startup, the equivalent of
13732 <pre>
13733 signal(sig, SIG_IGN);
13734 </pre>
13735 may be executed for some signals selected in an implementation-defined manner; the
13736 equivalent of
13737 <pre>
13738 signal(sig, SIG_DFL);
13739 </pre>
13740 is executed for all other signals defined by the implementation.
13741 <p><!--para 7 -->
13742 The implementation shall behave as if no library function calls the signal function.
13743 <p><b>Returns</b>
13744 <p><!--para 8 -->
13745 If the request can be honored, the signal function returns the value of func for the
13746 most recent successful call to signal for the specified signal sig. Otherwise, a value of
13747 SIG_ERR is returned and a positive value is stored in errno.
13748 <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
13749 _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>).
13751 <p><b>Footnotes</b>
13752 <p><small><a name="note248" href="#note248">248)</a> This includes functions called indirectly via standard library functions (e.g., a SIGABRT handler
13753 called via the abort function).
13754 </small>
13755 <p><small><a name="note249" href="#note249">249)</a> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
13756 </small>
13761 <p><b>Synopsis</b>
13762 <p><!--para 1 -->
13763 <pre>
13765 int raise(int sig);
13766 </pre>
13767 <p><b>Description</b>
13768 <p><!--para 2 -->
13769 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
13770 signal handler is called, the raise function shall not return until after the signal handler
13771 does.
13772 <p><b>Returns</b>
13773 <p><!--para 3 -->
13774 The raise function returns zero if successful, nonzero if unsuccessful.
13775 <!--page 285 -->
13778 <p><!--para 1 -->
13780 <p><!--para 2 -->
13781 The macro
13782 <pre>
13783 alignas
13784 </pre>
13785 expands to _Alignas.
13786 <p><!--para 3 -->
13787 The remaining macro is suitable for use in #if preprocessing directives. It is
13788 <pre>
13789 __alignas_is_defined
13790 </pre>
13791 which expands to the integer constant 1.
13792 <!--page 286 -->
13795 <p><!--para 1 -->
13796 The header <a href="#7.16"><stdarg.h></a> declares a type and defines four macros, for advancing
13797 through a list of arguments whose number and types are not known to the called function
13798 when it is translated.
13799 <p><!--para 2 -->
13800 A function may be called with a variable number of arguments of varying types. As
13801 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
13802 parameter plays a special role in the access mechanism, and will be designated parmN in
13803 this description.
13804 <p><!--para 3 -->
13805 The type declared is
13806 <pre>
13807 va_list
13808 </pre>
13809 which is a complete object type suitable for holding information needed by the macros
13810 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
13811 desired, the called function shall declare an object (generally referred to as ap in this
13812 subclause) having type va_list. The object ap may be passed as an argument to
13813 another function; if that function invokes the va_arg macro with parameter ap, the
13814 value of ap in the calling function is indeterminate and shall be passed to the va_end
13817 <p><b>Footnotes</b>
13818 <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
13819 case the original function may make further use of the original list after the other function returns.
13820 </small>
13823 <p><!--para 1 -->
13824 The va_start and va_arg macros described in this subclause shall be implemented
13825 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
13826 identifiers declared with external linkage. If a macro definition is suppressed in order to
13827 access an actual function, or a program defines an external identifier with the same name,
13828 the behavior is undefined. Each invocation of the va_start and va_copy macros
13829 shall be matched by a corresponding invocation of the va_end macro in the same
13830 function.
13833 <p><b>Synopsis</b>
13834 <p><!--para 1 -->
13835 <pre>
13837 type va_arg(va_list ap, type);
13838 </pre>
13839 <p><b>Description</b>
13840 <p><!--para 2 -->
13841 The va_arg macro expands to an expression that has the specified type and the value of
13842 the next argument in the call. The parameter ap shall have been initialized by the
13843 va_start or va_copy macro (without an intervening invocation of the va_end
13845 <!--page 287 -->
13846 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
13847 values of successive arguments are returned in turn. The parameter type shall be a type
13848 name specified such that the type of a pointer to an object that has the specified type can
13849 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
13850 type is not compatible with the type of the actual next argument (as promoted according
13851 to the default argument promotions), the behavior is undefined, except for the following
13852 cases:
13853 <ul>
13854 <li> one type is a signed integer type, the other type is the corresponding unsigned integer
13855 type, and the value is representable in both types;
13856 <li> one type is pointer to void and the other is a pointer to a character type.
13857 </ul>
13858 <p><b>Returns</b>
13859 <p><!--para 3 -->
13860 The first invocation of the va_arg macro after that of the va_start macro returns the
13861 value of the argument after that specified by parmN . Successive invocations return the
13862 values of the remaining arguments in succession.
13865 <p><b>Synopsis</b>
13866 <p><!--para 1 -->
13867 <pre>
13869 void va_copy(va_list dest, va_list src);
13870 </pre>
13871 <p><b>Description</b>
13872 <p><!--para 2 -->
13873 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
13874 been applied to dest followed by the same sequence of uses of the va_arg macro as
13875 had previously been used to reach the present state of src. Neither the va_copy nor
13876 va_start macro shall be invoked to reinitialize dest without an intervening
13877 invocation of the va_end macro for the same dest.
13878 <p><b>Returns</b>
13879 <p><!--para 3 -->
13880 The va_copy macro returns no value.
13883 <p><b>Synopsis</b>
13884 <p><!--para 1 -->
13885 <pre>
13887 void va_end(va_list ap);
13888 </pre>
13889 <p><b>Description</b>
13890 <p><!--para 2 -->
13891 The va_end macro facilitates a normal return from the function whose variable
13892 argument list was referred to by the expansion of the va_start macro, or the function
13893 containing the expansion of the va_copy macro, that initialized the va_list ap. The
13894 va_end macro may modify ap so that it is no longer usable (without being reinitialized
13895 <!--page 288 -->
13896 by the va_start or va_copy macro). If there is no corresponding invocation of the
13897 va_start or va_copy macro, or if the va_end macro is not invoked before the
13898 return, the behavior is undefined.
13899 <p><b>Returns</b>
13900 <p><!--para 3 -->
13901 The va_end macro returns no value.
13904 <p><b>Synopsis</b>
13905 <p><!--para 1 -->
13906 <pre>
13908 void va_start(va_list ap, parmN);
13909 </pre>
13910 <p><b>Description</b>
13911 <p><!--para 2 -->
13912 The va_start macro shall be invoked before any access to the unnamed arguments.
13913 <p><!--para 3 -->
13914 The va_start macro initializes ap for subsequent use by the va_arg and va_end
13915 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
13916 without an intervening invocation of the va_end macro for the same ap.
13917 <p><!--para 4 -->
13918 The parameter parmN is the identifier of the rightmost parameter in the variable
13919 parameter list in the function definition (the one just before the , ...). If the parameter
13920 parmN is declared with the register storage class, with a function or array type, or
13921 with a type that is not compatible with the type that results after application of the default
13922 argument promotions, the behavior is undefined.
13923 <p><b>Returns</b>
13924 <p><!--para 5 -->
13925 The va_start macro returns no value.
13926 <p><!--para 6 -->
13927 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
13928 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
13929 pointers is specified by the first argument to f1.
13930 <!--page 289 -->
13931 <pre>
13933 #define MAXARGS 31
13934 void f1(int n_ptrs, ...)
13935 {
13936 va_list ap;
13937 char *array[MAXARGS];
13938 int ptr_no = 0;
13939 if (n_ptrs > MAXARGS)
13940 n_ptrs = MAXARGS;
13941 va_start(ap, n_ptrs);
13942 while (ptr_no < n_ptrs)
13943 array[ptr_no++] = va_arg(ap, char *);
13944 va_end(ap);
13945 f2(n_ptrs, array);
13946 }
13947 </pre>
13948 Each call to f1 is required to have visible the definition of the function or a declaration such as
13949 <pre>
13950 void f1(int, ...);
13951 </pre>
13953 <p><!--para 7 -->
13954 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
13955 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
13956 is gathered again and passed to function f4.
13957 <!--page 290 -->
13958 <pre>
13960 #define MAXARGS 31
13961 void f3(int n_ptrs, int f4_after, ...)
13962 {
13963 va_list ap, ap_save;
13964 char *array[MAXARGS];
13965 int ptr_no = 0;
13966 if (n_ptrs > MAXARGS)
13967 n_ptrs = MAXARGS;
13968 va_start(ap, f4_after);
13969 while (ptr_no < n_ptrs) {
13970 array[ptr_no++] = va_arg(ap, char *);
13971 if (ptr_no == f4_after)
13972 va_copy(ap_save, ap);
13973 }
13974 va_end(ap);
13975 f2(n_ptrs, array);
13976 // Now process the saved copy.
13977 n_ptrs -= f4_after;
13978 ptr_no = 0;
13979 while (ptr_no < n_ptrs)
13980 array[ptr_no++] = va_arg(ap_save, char *);
13981 va_end(ap_save);
13982 f4(n_ptrs, array);
13983 }
13984 </pre>
13989 <p><!--para 1 -->
13990 The header <a href="#7.17"><stdatomic.h></a> defines several macros and declares several types and
13991 functions for performing atomic operations on data shared between threads.
13992 <p><!--para 2 -->
13993 Implementations that define the macro __STDC_NO_THREADS__ need not provide
13994 this header nor support any of its facilities.
13995 <p><!--para 3 -->
13996 The macros defined are the atomic lock-free macros
13997 <pre>
13998 ATOMIC_CHAR_LOCK_FREE
13999 ATOMIC_CHAR16_T_LOCK_FREE
14000 ATOMIC_CHAR32_T_LOCK_FREE
14001 ATOMIC_WCHAR_T_LOCK_FREE
14002 ATOMIC_SHORT_LOCK_FREE
14003 ATOMIC_INT_LOCK_FREE
14004 ATOMIC_LONG_LOCK_FREE
14005 ATOMIC_LLONG_LOCK_FREE
14006 ATOMIC_ADDRESS_LOCK_FREE
14007 </pre>
14008 which indicate the lock-free property of the corresponding atomic types (both signed and
14009 unsigned); and
14010 <pre>
14011 ATOMIC_FLAG_INIT
14012 </pre>
14013 which expands to an initializer for an object of type atomic_flag.
14014 <p><!--para 4 -->
14015 The types include
14016 <pre>
14017 memory_order
14018 </pre>
14019 which is an enumerated type whose enumerators identify memory ordering constraints;
14020 <pre>
14021 atomic_flag
14022 </pre>
14023 which is a structure type representing a lock-free, primitive atomic flag;
14024 <pre>
14025 atomic_bool
14026 </pre>
14027 which is a structure type representing the atomic analog of the type _Bool;
14028 <pre>
14029 atomic_address
14030 </pre>
14031 which is a structure type representing the atomic analog of a pointer type; and several
14032 atomic analogs of integer types.
14033 <p><!--para 5 -->
14034 In the following operation definitions:
14035 <ul>
14036 <li> An A refers to one of the atomic types.
14037 <!--page 291 -->
14038 <li> A C refers to its corresponding non-atomic type. The atomic_address atomic
14039 type corresponds to the void * non-atomic type.
14040 <li> An M refers to the type of the other argument for arithmetic operations. For atomic
14041 integer types, M is C. For atomic address types, M is ptrdiff_t.
14042 <li> The functions not ending in _explicit have the same semantics as the
14043 corresponding _explicit function with memory_order_seq_cst for the
14044 memory_order argument.
14045 </ul>
14046 <p><!--para 6 -->
14047 NOTE Many operations are volatile-qualified. The ''volatile as device register'' semantics have not
14048 changed in the standard. This qualification means that volatility is preserved when applying these
14049 operations to volatile objects.
14055 <p><b>Synopsis</b>
14056 <p><!--para 1 -->
14057 <pre>
14059 #define ATOMIC_VAR_INIT(C value)
14060 </pre>
14061 <p><b>Description</b>
14062 <p><!--para 2 -->
14063 The ATOMIC_VAR_INIT macro expands to a token sequence suitable for initializing an
14064 atomic object of a type that is initialization-compatible with value. An atomic object
14065 with automatic storage duration that is not explicitly initialized using
14066 ATOMIC_VAR_INIT is initially in an indeterminate state; however, the default (zero)
14067 initialization for objects with static or thread-local storage duration is guaranteed to
14068 produce a valid state.
14069 <p><!--para 3 -->
14070 Concurrent access to the variable being initialized, even via an atomic operation,
14071 constitutes a data race.
14072 <p><!--para 4 -->
14073 EXAMPLE
14074 <pre>
14075 atomic_int guide = ATOMIC_VAR_INIT(42);
14076 </pre>
14080 <p><b>Synopsis</b>
14081 <p><!--para 1 -->
14082 <pre>
14084 void atomic_init(volatile A *obj, C value);
14085 </pre>
14086 <p><b>Description</b>
14087 <p><!--para 2 -->
14088 The atomic_init generic function initializes the atomic object pointed to by obj to
14089 the value value, while also initializing any additional state that the implementation
14090 might need to carry for the atomic object.
14091 <!--page 292 -->
14092 <p><!--para 3 -->
14093 Although this function initializes an atomic object, it does not avoid data races;
14094 concurrent access to the variable being initialized, even via an atomic operation,
14095 constitutes a data race.
14096 <p><b>Returns</b>
14097 <p><!--para 4 -->
14098 The atomic_init generic function returns no value.
14099 <p><!--para 5 -->
14100 EXAMPLE
14101 <pre>
14102 atomic_int guide;
14103 atomic_init(&guide, 42);
14104 </pre>
14108 <p><!--para 1 -->
14109 The enumerated type memory_order specifies the detailed regular (non-atomic)
14110 memory synchronization operations as defined in <a href="#5.1.2.4">5.1.2.4</a> and may provide for operation
14111 ordering. Its enumeration constants are as follows:
14112 <pre>
14113 memory_order_relaxed
14114 memory_order_consume
14115 memory_order_acquire
14116 memory_order_release
14117 memory_order_acq_rel
14118 memory_order_seq_cst
14119 </pre>
14120 <p><!--para 2 -->
14121 For memory_order_relaxed, no operation orders memory.
14122 <p><!--para 3 -->
14123 For memory_order_release, memory_order_acq_rel, and
14124 memory_order_seq_cst, a store operation performs a release operation on the
14125 affected memory location.
14126 <p><!--para 4 -->
14127 For memory_order_acquire, memory_order_acq_rel, and
14128 memory_order_seq_cst, a load operation performs an acquire operation on the
14129 affected memory location.
14130 <p><!--para 5 -->
14131 For memory_order_consume, a load operation performs a consume operation on the
14132 affected memory location.
14133 <p><!--para 6 -->
14134 For memory_order_seq_cst, there shall be a single total order S on all operations,
14135 consistent with the ''happens before'' order and modification orders for all affected
14136 locations, such that each memory_order_seq_cst operation that loads a value
14137 observes either the last preceding modification according to this order S, or the result of
14138 an operation that is not memory_order_seq_cst.
14139 <p><!--para 7 -->
14140 NOTE 1 Although it is not explicitly required that S include lock operations, it can always be extended to
14141 an order that does include lock and unlock operations, since the ordering between those is already included
14142 in the ''happens before'' ordering.
14144 <p><!--para 8 -->
14145 NOTE 2 Atomic operations specifying memory_order_relaxed are relaxed only with respect to
14146 memory ordering. Implementations must still guarantee that any given atomic access to a particular atomic
14147 <!--page 293 -->
14148 object be indivisible with respect to all other atomic accesses to that object.
14150 <p><!--para 9 -->
14151 For an atomic operation B that reads the value of an atomic object M, if there is a
14152 memory_order_seq_cst fence X sequenced before B, then B observes either the
14153 last memory_order_seq_cst modification of M preceding X in the total order S or
14154 a later modification of M in its modification order.
14155 <p><!--para 10 -->
14156 For atomic operations A and B on an atomic object M, where A modifies M and B takes
14157 its value, if there is a memory_order_seq_cst fence X such that A is sequenced
14158 before X and B follows X in S, then B observes either the effects of A or a later
14159 modification of M in its modification order.
14160 <p><!--para 11 -->
14161 For atomic operations A and B on an atomic object M, where A modifies M and B takes
14162 its value, if there are memory_order_seq_cst fences X and Y such that A is
14163 sequenced before X, Y is sequenced before B, and X precedes Y in S, then B observes
14164 either the effects of A or a later modification of M in its modification order.
14165 <p><!--para 12 -->
14166 Atomic read-modify-write operations shall always read the last value (in the modification
14167 order) stored before the write associated with the read-modify-write operation.
14168 <p><!--para 13 -->
14169 An atomic store shall only store a value that has been computed from constants and
14170 program input values by a finite sequence of program evaluations, such that each
14171 evaluation observes the values of variables as computed by the last prior assignment in
14172 the sequence.<sup><a href="#note251"><b>251)</b></a></sup> The ordering of evaluations in this sequence shall be such that
14173 <ul>
14174 <li> If an evaluation B observes a value computed by A in a different thread, then B does
14175 not happen before A.
14176 <li> If an evaluation A is included in the sequence, then all evaluations that assign to the
14177 same variable and happen before A are also included.
14178 </ul>
14179 <p><!--para 14 -->
14180 NOTE 3 The second requirement disallows ''out-of-thin-air'', or ''speculative'' stores of atomics when
14181 relaxed atomics are used. Since unordered operations are involved, evaluations may appear in this
14182 sequence out of thread order. For example, with x and y initially zero,
14183 <pre>
14184 // Thread 1:
14185 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14186 atomic_store_explicit(&x, r1, memory_order_relaxed);
14187 </pre>
14189 <pre>
14190 // Thread 2:
14191 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14192 atomic_store_explicit(&y, 42, memory_order_relaxed);
14193 </pre>
14194 is allowed to produce r1 == 42 && r2 == 42. The sequence of evaluations justifying this consists of:
14199 <!--page 294 -->
14200 <pre>
14201 atomic_store_explicit(&y, 42, memory_order_relaxed);
14202 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14203 atomic_store_explicit(&x, r1, memory_order_relaxed);
14204 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14205 </pre>
14206 On the other hand,
14207 <pre>
14208 // Thread 1:
14209 r1 = atomic_load_explicit(&y, memory_order_relaxed);
14210 atomic_store_explicit(&x, r1, memory_order_relaxed);
14211 </pre>
14213 <pre>
14214 // Thread 2:
14215 r2 = atomic_load_explicit(&x, memory_order_relaxed);
14216 atomic_store_explicit(&y, r2, memory_order_relaxed);
14217 </pre>
14218 is not allowed to produce r1 == 42 && r2 = 42, since there is no sequence of evaluations that results
14219 in the computation of 42. In the absence of ''relaxed'' operations and read-modify-write operations with
14220 weaker than memory_order_acq_rel ordering, the second requirement has no impact.
14222 <p><b>Recommended practice</b>
14223 <p><!--para 15 -->
14224 The requirements do not forbid r1 == 42 && r2 == 42 in the following example,
14225 with x and y initially zero:
14226 <pre>
14227 // Thread 1:
14228 r1 = atomic_load_explicit(&x, memory_order_relaxed);
14229 if (r1 == 42)
14230 atomic_store_explicit(&y, r1, memory_order_relaxed);
14231 </pre>
14233 <pre>
14234 // Thread 2:
14235 r2 = atomic_load_explicit(&y, memory_order_relaxed);
14236 if (r2 == 42)
14237 atomic_store_explicit(&x, 42, memory_order_relaxed);
14238 </pre>
14239 However, this is not useful behavior, and implementations should not allow it.
14240 <p><!--para 16 -->
14241 Implementations should make atomic stores visible to atomic loads within a reasonable
14242 amount of time.
14244 <p><b>Footnotes</b>
14245 <p><small><a name="note251" href="#note251">251)</a> Among other implications, atomic variables shall not decay.
14246 </small>
14249 <p><b>Synopsis</b>
14250 <p><!--para 1 -->
14251 <pre>
14253 type kill_dependency(type y);
14254 </pre>
14255 <p><b>Description</b>
14256 <p><!--para 2 -->
14257 The kill_dependency macro terminates a dependency chain; the argument does not
14258 carry a dependency to the return value.
14259 <!--page 295 -->
14260 <p><b>Returns</b>
14261 <p><!--para 3 -->
14262 The kill_dependency macro returns the value of y.
14265 <p><!--para 1 -->
14266 This subclause introduces synchronization primitives called fences. Fences can have
14267 acquire semantics, release semantics, or both. A fence with acquire semantics is called
14268 an acquire fence; a fence with release semantics is called a release fence.
14269 <p><!--para 2 -->
14270 A release fence A synchronizes with an acquire fence B if there exist atomic operations
14271 X and Y , both operating on some atomic object M, such that A is sequenced before X, X
14272 modifies M, Y is sequenced before B, and Y reads the value written by X or a value
14273 written by any side effect in the hypothetical release sequence X would head if it were a
14274 release operation.
14275 <p><!--para 3 -->
14276 A release fence A synchronizes with an atomic operation B that performs an acquire
14277 operation on an atomic object M if there exists an atomic operation X such that A is
14278 sequenced before X, X modifies M, and B reads the value written by X or a value written
14279 by any side effect in the hypothetical release sequence X would head if it were a release
14280 operation.
14281 <p><!--para 4 -->
14282 An atomic operation A that is a release operation on an atomic object M synchronizes
14283 with an acquire fence B if there exists some atomic operation X on M such that X is
14284 sequenced before B and reads the value written by A or a value written by any side effect
14285 in the release sequence headed by A.
14288 <p><b>Synopsis</b>
14289 <p><!--para 1 -->
14290 <pre>
14292 void atomic_thread_fence(memory_order order);
14293 </pre>
14294 <p><b>Description</b>
14295 <p><!--para 2 -->
14296 Depending on the value of order, this operation:
14297 <ul>
14298 <li> has no effects, if order == memory_order_relaxed;
14299 <li> is an acquire fence, if order == memory_order_acquire or order ==
14300 memory_order_consume;
14301 <li> is a release fence, if order == memory_order_release;
14302 <li> is both an acquire fence and a release fence, if order ==
14303 memory_order_acq_rel;
14304 <li> is a sequentially consistent acquire and release fence, if order ==
14305 memory_order_seq_cst.
14306 <!--page 296 -->
14307 </ul>
14308 <p><b>Returns</b>
14309 <p><!--para 3 -->
14310 The atomic_thread_fence function returns no value.
14313 <p><b>Synopsis</b>
14314 <p><!--para 1 -->
14315 <pre>
14317 void atomic_signal_fence(memory_order order);
14318 </pre>
14319 <p><b>Description</b>
14320 <p><!--para 2 -->
14321 Equivalent to atomic_thread_fence(order), except that ''synchronizes with''
14322 relationships are established only between a thread and a signal handler executed in the
14323 same thread.
14324 <p><!--para 3 -->
14325 NOTE 1 The atomic_signal_fence function can be used to specify the order in which actions
14326 performed by the thread become visible to the signal handler.
14328 <p><!--para 4 -->
14329 NOTE 2 Compiler optimizations and reorderings of loads and stores are inhibited in the same way as with
14330 atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would
14331 have inserted are not emitted.
14333 <p><b>Returns</b>
14334 <p><!--para 5 -->
14335 The atomic_signal_fence function returns no value.
14338 <p><!--para 1 -->
14339 The atomic lock-free macros indicate the lock-free property of integer and address atomic
14340 types. A value of 0 indicates that the type is never lock-free; a value of 1 indicates that
14341 the type is sometimes lock-free; a value of 2 indicates that the type is always lock-free.
14342 <p><!--para 2 -->
14343 NOTE Operations that are lock-free should also be address-free. That is, atomic operations on the same
14344 memory location via two different addresses will communicate atomically. The implementation should not
14345 depend on any per-process state. This restriction enables communication via memory mapped into a
14346 process more than once and memory shared between two processes.
14349 <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>
14350 <p><b>Synopsis</b>
14351 <p><!--para 1 -->
14352 <pre>
14354 _Bool atomic_is_lock_free(atomic_type const volatile *obj);
14355 </pre>
14356 <p><b>Description</b>
14357 <p><!--para 2 -->
14358 The atomic_is_lock_free generic function indicates whether or not the object
14359 pointed to by obj is lock-free. atomic_type can be any atomic type.
14360 <p><b>Returns</b>
14361 <p><!--para 3 -->
14362 The atomic_is_lock_free generic function returns nonzero (true) if and only if the
14363 object's operations are lock-free. The result of a lock-free query on one object cannot be
14364 <!--page 297 -->
14365 inferred from the result of a lock-free query on another object.
14368 <p><!--para 1 -->
14369 For each line in the following table, the atomic type name is declared as the
14370 corresponding direct type.
14371 <!--page 298 -->
14372 <pre>
14373 Atomic type name Direct type
14374 atomic_char _Atomic char
14375 atomic_schar _Atomic signed char
14376 atomic_uchar _Atomic unsigned char
14377 atomic_short _Atomic short
14378 atomic_ushort _Atomic unsigned short
14379 atomic_int _Atomic int
14380 atomic_uint _Atomic unsigned int
14381 atomic_long _Atomic long
14382 atomic_ulong _Atomic unsigned long
14383 atomic_llong _Atomic long long
14384 atomic_ullong _Atomic unsigned long long
14385 atomic_char16_t _Atomic char16_t
14386 atomic_char32_t _Atomic char32_t
14387 atomic_wchar_t _Atomic wchar_t
14388 atomic_int_least8_t _Atomic int_least8_t
14389 atomic_uint_least8_t _Atomic uint_least8_t
14390 atomic_int_least16_t _Atomic int_least16_t
14391 atomic_uint_least16_t _Atomic uint_least16_t
14392 atomic_int_least32_t _Atomic int_least32_t
14393 atomic_uint_least32_t _Atomic uint_least32_t
14394 atomic_int_least64_t _Atomic int_least64_t
14395 atomic_uint_least64_t _Atomic uint_least64_t
14396 atomic_int_fast8_t _Atomic int_fast8_t
14397 atomic_uint_fast8_t _Atomic uint_fast8_t
14398 atomic_int_fast16_t _Atomic int_fast16_t
14399 atomic_uint_fast16_t _Atomic uint_fast16_t
14400 atomic_int_fast32_t _Atomic int_fast32_t
14401 atomic_uint_fast32_t _Atomic uint_fast32_t
14402 atomic_int_fast64_t _Atomic int_fast64_t
14403 atomic_uint_fast64_t _Atomic uint_fast64_t
14404 atomic_intptr_t _Atomic intptr_t
14405 atomic_uintptr_t _Atomic uintptr_t
14406 atomic_size_t _Atomic size_t
14407 atomic_ptrdiff_t _Atomic ptrdiff_t
14408 atomic_intmax_t _Atomic intmax_t
14409 atomic_uintmax_t _Atomic uintmax_t
14410 </pre>
14411 <p><!--para 2 -->
14413 <p><!--para 3 -->
14414 The atomic_bool type provides an atomic boolean.
14415 <!--page 299 -->
14416 <p><!--para 4 -->
14417 The atomic_address type provides atomic void * operations. The unit of
14418 addition/subtraction shall be one byte.
14419 <p><!--para 5 -->
14420 NOTE The representation of atomic integer and address types need not have the same size as their
14421 corresponding regular types. They should have the same size whenever possible, as it eases effort required
14422 to port existing code.
14426 <p><!--para 1 -->
14427 There are only a few kinds of operations on atomic types, though there are many
14428 instances of those kinds. This subclause specifies each general kind.
14431 <p><b>Synopsis</b>
14432 <p><!--para 1 -->
14433 <pre>
14435 void atomic_store(volatile A *object, C desired);
14436 void atomic_store_explicit(volatile A *object,
14437 C desired, memory_order order);
14438 </pre>
14439 <p><b>Description</b>
14440 <p><!--para 2 -->
14441 The order argument shall not be memory_order_acquire,
14442 memory_order_consume, nor memory_order_acq_rel. Atomically replace the
14443 value pointed to by object with the value of desired. Memory is affected according
14444 to the value of order.
14445 <p><b>Returns</b>
14446 <p><!--para 3 -->
14447 The atomic_store generic functions return no value.
14450 <p><b>Synopsis</b>
14451 <p><!--para 1 -->
14452 <pre>
14454 C atomic_load(volatile A *object);
14455 C atomic_load_explicit(volatile A *object,
14456 memory_order order);
14457 </pre>
14458 <p><b>Description</b>
14459 <p><!--para 2 -->
14460 The order argument shall not be memory_order_release nor
14461 memory_order_acq_rel. Memory is affected according to the value of order.
14462 <p><b>Returns</b>
14463 Atomically returns the value pointed to by object.
14464 <!--page 300 -->
14466 <h5><a name="7.17.7.3" href="#7.17.7.3">7.17.7.3 The atomic_exchange generic functions</a></h5>
14467 <p><b>Synopsis</b>
14468 <p><!--para 1 -->
14469 <pre>
14471 C atomic_exchange(volatile A *object, C desired);
14472 C atomic_exchange_explicit(volatile A *object,
14473 C desired, memory_order order);
14474 </pre>
14475 <p><b>Description</b>
14476 <p><!--para 2 -->
14477 Atomically replace the value pointed to by object with desired. Memory is affected
14478 according to the value of order. These operations are read-modify-write operations
14480 <p><b>Returns</b>
14481 <p><!--para 3 -->
14482 Atomically returns the value pointed to by object immediately before the effects.
14484 <h5><a name="7.17.7.4" href="#7.17.7.4">7.17.7.4 The atomic_compare_exchange generic functions</a></h5>
14485 <p><b>Synopsis</b>
14486 <p><!--para 1 -->
14487 <pre>
14489 _Bool atomic_compare_exchange_strong(volatile A *object,
14490 C *expected, C desired);
14491 _Bool atomic_compare_exchange_strong_explicit(
14492 volatile A *object, C *expected, C desired,
14493 memory_order success, memory_order failure);
14494 _Bool atomic_compare_exchange_weak(volatile A *object,
14495 C *expected, C desired);
14496 _Bool atomic_compare_exchange_weak_explicit(
14497 volatile A *object, C *expected, C desired,
14498 memory_order success, memory_order failure);
14499 </pre>
14500 <p><b>Description</b>
14501 <p><!--para 2 -->
14502 The failure argument shall not be memory_order_release nor
14503 memory_order_acq_rel. The failure argument shall be no stronger than the
14504 success argument. Atomically, compares the value pointed to by object for equality
14505 with that in expected, and if true, replaces the value pointed to by object with
14506 desired, and if false, updates the value in expected with the value pointed to by
14507 object. Further, if the comparison is true, memory is affected according to the value of
14508 success, and if the comparison is false, memory is affected according to the value of
14509 failure. These operations are atomic read-modify-write operations (<a href="#5.1.2.4">5.1.2.4</a>).
14510 <p><!--para 3 -->
14511 NOTE 1 The effect of the compare-and-exchange operations is
14512 <!--page 301 -->
14513 <pre>
14514 if (*object == *expected)
14515 *object = desired;
14516 else
14517 *expected = *object;
14518 </pre>
14520 <p><!--para 4 -->
14521 The weak compare-and-exchange operations may fail spuriously, that is, return zero
14522 while leaving the value pointed to by expected unchanged.
14523 <p><!--para 5 -->
14524 NOTE 2 This spurious failure enables implementation of compare-and-exchange on a broader class of
14525 machines, e.g. load-locked store-conditional machines.
14527 <p><!--para 6 -->
14528 EXAMPLE A consequence of spurious failure is that nearly all uses of weak compare-and-exchange will
14529 be in a loop.
14530 <pre>
14531 exp = atomic_load(&cur);
14532 do {
14533 des = function(exp);
14534 } while (!atomic_compare_exchange_weak(&cur, &exp, des));
14535 </pre>
14536 When a compare-and-exchange is in a loop, the weak version will yield better performance on some
14537 platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the
14538 strong one is preferable.
14540 <p><b>Returns</b>
14541 <p><!--para 7 -->
14542 The result of the comparison.
14544 <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>
14545 <p><!--para 1 -->
14546 The following operations perform arithmetic and bitwise computations. All of these
14547 operations are applicable to an object of any atomic integer type. Only addition and
14548 subtraction are applicable to atomic_address. None of these operations is applicable
14549 to atomic_bool. The key, operator, and computation correspondence is:
14550 key op computation
14551 add + addition
14552 sub - subtraction
14553 or | bitwise inclusive or
14554 xor ^ bitwise exclusive or
14555 and & bitwise and
14556 <p><b>Synopsis</b>
14557 <p><!--para 2 -->
14558 <pre>
14560 C atomic_fetch_key(volatile A *object, M operand);
14561 C atomic_fetch_key_explicit(volatile A *object,
14562 M operand, memory_order order);
14563 </pre>
14564 <p><b>Description</b>
14565 <p><!--para 3 -->
14566 Atomically replaces the value pointed to by object with the result of the computation
14567 applied to the value pointed to by object and the given operand. Memory is affected
14568 according to the value of order. These operations are atomic read-modify-write
14569 <!--page 302 -->
14570 operations (<a href="#5.1.2.4">5.1.2.4</a>). For signed integer types, arithmetic is defined to use two's
14571 complement representation with silent wrap-around on overflow; there are no undefined
14572 results. For address types, the result may be an undefined address, but the operations
14573 otherwise have no undefined behavior.
14574 <p><b>Returns</b>
14575 <p><!--para 4 -->
14576 Atomically, the value pointed to by object immediately before the effects.
14577 <p><!--para 5 -->
14578 NOTE The operation of the atomic_fetch and modify generic functions are nearly equivalent to the
14579 operation of the corresponding op= compound assignment operators. The only differences are that the
14580 compound assignment operators are not guaranteed to operate atomically, and the value yielded by a
14581 compound assignment operator is the updated value of the object, whereas the value returned by the
14582 atomic_fetch and modify generic functions is the previous value of the atomic object.
14586 <p><!--para 1 -->
14587 The atomic_flag type provides the classic test-and-set functionality. It has two
14588 states, set and clear.
14589 <p><!--para 2 -->
14590 Operations on an object of type atomic_flag shall be lock free.
14591 <p><!--para 3 -->
14592 NOTE Hence the operations should also be address-free. No other type requires lock-free operations, so
14593 the atomic_flag type is the minimum hardware-implemented type needed to conform to this
14594 International standard. The remaining types can be emulated with atomic_flag, though with less than
14595 ideal properties.
14597 <p><!--para 4 -->
14598 The macro ATOMIC_FLAG_INIT may be used to initialize an atomic_flag to the
14599 clear state. An atomic_flag that is not explicitly initialized with
14600 ATOMIC_FLAG_INIT is initially in an indeterminate state.
14601 <p><!--para 5 -->
14602 EXAMPLE
14603 <pre>
14604 atomic_flag guard = ATOMIC_FLAG_INIT;
14605 </pre>
14608 <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>
14609 <p><b>Synopsis</b>
14610 <p><!--para 1 -->
14611 <pre>
14613 bool atomic_flag_test_and_set(
14614 volatile atomic_flag *object);
14615 bool atomic_flag_test_and_set_explicit(
14616 volatile atomic_flag *object, memory_order order);
14617 </pre>
14618 <p><b>Description</b>
14619 <p><!--para 2 -->
14620 Atomically sets the value pointed to by object to true. Memory is affected according
14621 to the value of order. These operations are atomic read-modify-write operations
14623 <!--page 303 -->
14624 <p><b>Returns</b>
14625 <p><!--para 3 -->
14626 Atomically, the value of the object immediately before the effects.
14629 <p><b>Synopsis</b>
14630 <p><!--para 1 -->
14631 <pre>
14633 void atomic_flag_clear(volatile atomic_flag *object);
14634 void atomic_flag_clear_explicit(
14635 volatile atomic_flag *object, memory_order order);
14636 </pre>
14637 <p><b>Description</b>
14638 <p><!--para 2 -->
14639 The order argument shall not be memory_order_acquire nor
14640 memory_order_acq_rel. Atomically sets the value pointed to by object to false.
14641 Memory is affected according to the value of order.
14642 <p><b>Returns</b>
14643 <p><!--para 3 -->
14644 The atomic_flag_clear functions return no value.
14645 <!--page 304 -->
14648 <p><!--para 1 -->
14650 <p><!--para 2 -->
14651 The macro
14652 <pre>
14653 bool
14654 </pre>
14655 expands to _Bool.
14656 <p><!--para 3 -->
14657 The remaining three macros are suitable for use in #if preprocessing directives. They
14658 are
14659 <pre>
14660 true
14661 </pre>
14662 which expands to the integer constant 1,
14663 <pre>
14664 false
14665 </pre>
14666 which expands to the integer constant 0, and
14667 <pre>
14668 __bool_true_false_are_defined
14669 </pre>
14670 which expands to the integer constant 1.
14671 <p><!--para 4 -->
14672 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
14678 <!--page 305 -->
14680 <p><b>Footnotes</b>
14681 <p><small><a name="note252" href="#note252">252)</a> See ''future library directions'' (<a href="#7.30.7">7.30.7</a>).
14682 </small>
14685 <p><!--para 1 -->
14686 The header <a href="#7.19"><stddef.h></a> defines the following macros and declares the following types.
14687 Some are also defined in other headers, as noted in their respective subclauses.
14688 <p><!--para 2 -->
14689 The types are
14690 <pre>
14691 ptrdiff_t
14692 </pre>
14693 which is the signed integer type of the result of subtracting two pointers;
14694 <pre>
14695 size_t
14696 </pre>
14697 which is the unsigned integer type of the result of the sizeof operator;
14698 <pre>
14699 max_align_t
14700 </pre>
14701 which is an object type whose alignment is as great as is supported by the implementation
14702 in all contexts; and
14703 <pre>
14704 wchar_t
14705 </pre>
14706 which is an integer type whose range of values can represent distinct codes for all
14707 members of the largest extended character set specified among the supported locales; the
14708 null character shall have the code value zero. Each member of the basic character set
14709 shall have a code value equal to its value when used as the lone character in an integer
14710 character constant if an implementation does not define
14711 __STDC_MB_MIGHT_NEQ_WC__.
14712 <p><!--para 3 -->
14713 The macros are
14714 <pre>
14715 NULL
14716 </pre>
14717 which expands to an implementation-defined null pointer constant; and
14718 <pre>
14719 offsetof(type, member-designator)
14720 </pre>
14721 which expands to an integer constant expression that has type size_t, the value of
14722 which is the offset in bytes, to the structure member (designated by member-designator),
14723 from the beginning of its structure (designated by type). The type and member designator
14724 shall be such that given
14725 <pre>
14726 static type t;
14727 </pre>
14728 then the expression &(t.member-designator) evaluates to an address constant. (If the
14729 specified member is a bit-field, the behavior is undefined.)
14730 <p><b>Recommended practice</b>
14731 <p><!--para 4 -->
14732 The types used for size_t and ptrdiff_t should not have an integer conversion rank
14733 greater than that of signed long int unless the implementation supports objects
14734 large enough to make this necessary.
14735 <!--page 306 -->
14737 <!--page 307 -->
14740 <p><!--para 1 -->
14741 The header <a href="#7.20"><stdint.h></a> declares sets of integer types having specified widths, and
14742 defines corresponding sets of macros.<sup><a href="#note253"><b>253)</b></a></sup> It also defines macros that specify limits of
14743 integer types corresponding to types defined in other standard headers.
14744 <p><!--para 2 -->
14745 Types are defined in the following categories:
14746 <ul>
14747 <li> integer types having certain exact widths;
14748 <li> integer types having at least certain specified widths;
14749 <li> fastest integer types having at least certain specified widths;
14750 <li> integer types wide enough to hold pointers to objects;
14751 <li> integer types having greatest width.
14752 </ul>
14753 (Some of these types may denote the same type.)
14754 <p><!--para 3 -->
14755 Corresponding macros specify limits of the declared types and construct suitable
14756 constants.
14757 <p><!--para 4 -->
14758 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
14759 declare that typedef name and define the associated macros. Conversely, for each type
14760 described herein that the implementation does not provide, <a href="#7.20"><stdint.h></a> shall not
14761 declare that typedef name nor shall it define the associated macros. An implementation
14762 shall provide those types described as ''required'', but need not provide any of the others
14763 (described as ''optional'').
14765 <p><b>Footnotes</b>
14766 <p><small><a name="note253" href="#note253">253)</a> See ''future library directions'' (<a href="#7.30.8">7.30.8</a>).
14767 </small>
14768 <p><small><a name="note254" href="#note254">254)</a> Some of these types may denote implementation-defined extended integer types.
14769 </small>
14772 <p><!--para 1 -->
14773 When typedef names differing only in the absence or presence of the initial u are defined,
14774 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
14775 implementation providing one of these corresponding types shall also provide the other.
14776 <p><!--para 2 -->
14777 In the following descriptions, the symbol N represents an unsigned decimal integer with
14778 no leading zeros (e.g., 8 or 24, but not 04 or 048).
14783 <!--page 308 -->
14786 <p><!--para 1 -->
14787 The typedef name intN_t designates a signed integer type with width N , no padding
14788 bits, and a two's complement representation. Thus, int8_t denotes such a signed
14789 integer type with a width of exactly 8 bits.
14790 <p><!--para 2 -->
14791 The typedef name uintN_t designates an unsigned integer type with width N and no
14792 padding bits. Thus, uint24_t denotes such an unsigned integer type with a width of
14793 exactly 24 bits.
14794 <p><!--para 3 -->
14795 These types are optional. However, if an implementation provides integer types with
14796 widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
14797 two's complement representation, it shall define the corresponding typedef names.
14800 <p><!--para 1 -->
14801 The typedef name int_leastN_t designates a signed integer type with a width of at
14802 least N , such that no signed integer type with lesser size has at least the specified width.
14803 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
14804 <p><!--para 2 -->
14805 The typedef name uint_leastN_t designates an unsigned integer type with a width
14806 of at least N , such that no unsigned integer type with lesser size has at least the specified
14807 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
14808 least 16 bits.
14809 <p><!--para 3 -->
14810 The following types are required:
14811 <pre>
14812 int_least8_t uint_least8_t
14813 int_least16_t uint_least16_t
14814 int_least32_t uint_least32_t
14815 int_least64_t uint_least64_t
14816 </pre>
14817 All other types of this form are optional.
14820 <p><!--para 1 -->
14821 Each of the following types designates an integer type that is usually fastest<sup><a href="#note255"><b>255)</b></a></sup> to operate
14822 with among all integer types that have at least the specified width.
14823 <p><!--para 2 -->
14824 The typedef name int_fastN_t designates the fastest signed integer type with a width
14825 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
14826 type with a width of at least N .
14831 <!--page 309 -->
14832 <p><!--para 3 -->
14833 The following types are required:
14834 <pre>
14835 int_fast8_t uint_fast8_t
14836 int_fast16_t uint_fast16_t
14837 int_fast32_t uint_fast32_t
14838 int_fast64_t uint_fast64_t
14839 </pre>
14840 All other types of this form are optional.
14842 <p><b>Footnotes</b>
14843 <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
14844 grounds for choosing one type over another, it will simply pick some integer type satisfying the
14845 signedness and width requirements.
14846 </small>
14848 <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>
14849 <p><!--para 1 -->
14850 The following type designates a signed integer type with the property that any valid
14851 pointer to void can be converted to this type, then converted back to pointer to void,
14852 and the result will compare equal to the original pointer:
14853 <pre>
14854 intptr_t
14855 </pre>
14856 The following type designates an unsigned integer type with the property that any valid
14857 pointer to void can be converted to this type, then converted back to pointer to void,
14858 and the result will compare equal to the original pointer:
14859 <pre>
14860 uintptr_t
14861 </pre>
14862 These types are optional.
14865 <p><!--para 1 -->
14866 The following type designates a signed integer type capable of representing any value of
14867 any signed integer type:
14868 <pre>
14869 intmax_t
14870 </pre>
14871 The following type designates an unsigned integer type capable of representing any value
14872 of any unsigned integer type:
14873 <pre>
14874 uintmax_t
14875 </pre>
14876 These types are required.
14879 <p><!--para 1 -->
14880 The following object-like macros specify the minimum and maximum limits of the types *
14881 declared in <a href="#7.20"><stdint.h></a>. Each macro name corresponds to a similar type name in
14883 <p><!--para 2 -->
14884 Each instance of any defined macro shall be replaced by a constant expression suitable
14885 for use in #if preprocessing directives, and this expression shall have the same type as
14886 would an expression that is an object of the corresponding type converted according to
14887 the integer promotions. Its implementation-defined value shall be equal to or greater in
14888 magnitude (absolute value) than the corresponding value given below, with the same sign,
14889 except where stated to be exactly the given value.
14890 <!--page 310 -->
14893 <p><!--para 1 -->
14894 <ul>
14895 <li> minimum values of exact-width signed integer types
14896 <pre>
14897 INTN_MIN exactly -(2 N -1 )
14898 </pre>
14899 <li> maximum values of exact-width signed integer types
14900 <pre>
14901 INTN_MAX exactly 2 N -1 - 1
14902 </pre>
14903 <li> maximum values of exact-width unsigned integer types
14904 UINTN_MAX exactly 2 N - 1
14905 </ul>
14907 <h5><a name="7.20.2.2" href="#7.20.2.2">7.20.2.2 Limits of minimum-width integer types</a></h5>
14908 <p><!--para 1 -->
14909 <ul>
14910 <li> minimum values of minimum-width signed integer types
14911 <pre>
14912 INT_LEASTN_MIN -(2 N -1 - 1)
14913 </pre>
14914 <li> maximum values of minimum-width signed integer types
14915 <pre>
14916 INT_LEASTN_MAX 2 N -1 - 1
14917 </pre>
14918 <li> maximum values of minimum-width unsigned integer types
14919 UINT_LEASTN_MAX 2N - 1
14920 </ul>
14922 <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>
14923 <p><!--para 1 -->
14924 <ul>
14925 <li> minimum values of fastest minimum-width signed integer types
14926 <pre>
14927 INT_FASTN_MIN -(2 N -1 - 1)
14928 </pre>
14929 <li> maximum values of fastest minimum-width signed integer types
14930 INT_FASTN_MAX 2 N -1 - 1
14931 <li> maximum values of fastest minimum-width unsigned integer types
14932 UINT_FASTN_MAX 2N - 1
14933 </ul>
14935 <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>
14936 <p><!--para 1 -->
14937 <ul>
14938 <li> minimum value of pointer-holding signed integer type
14939 <pre>
14940 INTPTR_MIN -(215 - 1)
14941 </pre>
14942 <li> maximum value of pointer-holding signed integer type
14943 INTPTR_MAX 215 - 1
14944 <li> maximum value of pointer-holding unsigned integer type
14945 UINTPTR_MAX 216 - 1
14946 <!--page 311 -->
14947 </ul>
14949 <h5><a name="7.20.2.5" href="#7.20.2.5">7.20.2.5 Limits of greatest-width integer types</a></h5>
14950 <p><!--para 1 -->
14951 <ul>
14952 <li> minimum value of greatest-width signed integer type
14953 INTMAX_MIN -(263 - 1)
14954 <li> maximum value of greatest-width signed integer type
14955 INTMAX_MAX 263 - 1
14956 <li> maximum value of greatest-width unsigned integer type
14957 UINTMAX_MAX 264 - 1
14958 </ul>
14961 <p><!--para 1 -->
14962 The following object-like macros specify the minimum and maximum limits of integer *
14963 types corresponding to types defined in other standard headers.
14964 <p><!--para 2 -->
14965 Each instance of these macros shall be replaced by a constant expression suitable for use
14966 in #if preprocessing directives, and this expression shall have the same type as would an
14967 expression that is an object of the corresponding type converted according to the integer
14968 promotions. Its implementation-defined value shall be equal to or greater in magnitude
14969 (absolute value) than the corresponding value given below, with the same sign. An
14970 implementation shall define only the macros corresponding to those typedef names it
14972 <ul>
14973 <li> limits of ptrdiff_t
14974 PTRDIFF_MIN -65535
14975 PTRDIFF_MAX +65535
14976 <li> limits of sig_atomic_t
14977 SIG_ATOMIC_MIN see below
14978 SIG_ATOMIC_MAX see below
14979 <li> limit of size_t
14980 SIZE_MAX 65535
14981 <li> limits of wchar_t
14982 WCHAR_MIN see below
14983 WCHAR_MAX see below
14984 <li> limits of wint_t
14989 <!--page 312 -->
14990 WINT_MIN see below
14991 WINT_MAX see below
14992 </ul>
14993 <p><!--para 3 -->
14994 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
14995 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
14996 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
14997 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
14998 SIG_ATOMIC_MAX shall be no less than 255.
14999 <p><!--para 4 -->
15000 If wchar_t (see <a href="#7.19">7.19</a>) is defined as a signed integer type, the value of WCHAR_MIN
15001 shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
15002 otherwise, wchar_t is defined as an unsigned integer type, and the value of
15003 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>
15004 <p><!--para 5 -->
15005 If wint_t (see <a href="#7.28">7.28</a>) is defined as a signed integer type, the value of WINT_MIN shall
15006 be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
15007 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
15008 shall be 0 and the value of WINT_MAX shall be no less than 65535.
15010 <p><b>Footnotes</b>
15011 <p><small><a name="note256" href="#note256">256)</a> A freestanding implementation need not provide all of these types.
15012 </small>
15013 <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
15014 character set.
15015 </small>
15018 <p><!--para 1 -->
15019 The following function-like macros expand to integer constants suitable for initializing *
15020 objects that have integer types corresponding to types defined in <a href="#7.20"><stdint.h></a>. Each
15021 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>.
15022 <p><!--para 2 -->
15023 The argument in any instance of these macros shall be an unsuffixed integer constant (as
15024 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.
15025 <p><!--para 3 -->
15026 Each invocation of one of these macros shall expand to an integer constant expression
15027 suitable for use in #if preprocessing directives. The type of the expression shall have
15028 the same type as would an expression of the corresponding type converted according to
15029 the integer promotions. The value of the expression shall be that of the argument.
15031 <h5><a name="7.20.4.1" href="#7.20.4.1">7.20.4.1 Macros for minimum-width integer constants</a></h5>
15032 <p><!--para 1 -->
15033 The macro INTN_C(value) shall expand to an integer constant expression
15034 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
15035 to an integer constant expression corresponding to the type uint_leastN_t. For
15036 example, if uint_least64_t is a name for the type unsigned long long int,
15037 then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
15042 <!--page 313 -->
15044 <h5><a name="7.20.4.2" href="#7.20.4.2">7.20.4.2 Macros for greatest-width integer constants</a></h5>
15045 <p><!--para 1 -->
15046 The following macro expands to an integer constant expression having the value specified
15047 by its argument and the type intmax_t:
15048 <pre>
15049 INTMAX_C(value)
15050 </pre>
15051 The following macro expands to an integer constant expression having the value specified
15052 by its argument and the type uintmax_t:
15053 <!--page 314 -->
15054 <pre>
15055 UINTMAX_C(value)
15056 </pre>
15061 <p><!--para 1 -->
15062 The header <a href="#7.21"><stdio.h></a> defines several macros, and declares three types and many
15063 functions for performing input and output.
15064 <p><!--para 2 -->
15066 <pre>
15067 FILE
15068 </pre>
15069 which is an object type capable of recording all the information needed to control a
15070 stream, including its file position indicator, a pointer to its associated buffer (if any), an
15071 error indicator that records whether a read/write error has occurred, and an end-of-file
15072 indicator that records whether the end of the file has been reached; and
15073 <pre>
15074 fpos_t
15075 </pre>
15076 which is a complete object type other than an array type capable of recording all the
15077 information needed to specify uniquely every position within a file.
15078 <p><!--para 3 -->
15080 <pre>
15081 _IOFBF
15082 _IOLBF
15083 _IONBF
15084 </pre>
15085 which expand to integer constant expressions with distinct values, suitable for use as the
15086 third argument to the setvbuf function;
15087 <pre>
15088 BUFSIZ
15089 </pre>
15090 which expands to an integer constant expression that is the size of the buffer used by the
15091 setbuf function;
15092 <pre>
15093 EOF
15094 </pre>
15095 which expands to an integer constant expression, with type int and a negative value, that
15096 is returned by several functions to indicate end-of-file, that is, no more input from a
15097 stream;
15098 <pre>
15099 FOPEN_MAX
15100 </pre>
15101 which expands to an integer constant expression that is the minimum number of files that
15102 the implementation guarantees can be open simultaneously;
15103 <pre>
15104 FILENAME_MAX
15105 </pre>
15106 which expands to an integer constant expression that is the size needed for an array of
15107 char large enough to hold the longest file name string that the implementation
15108 <!--page 315 -->
15110 <pre>
15111 L_tmpnam
15112 </pre>
15113 which expands to an integer constant expression that is the size needed for an array of
15114 char large enough to hold a temporary file name string generated by the tmpnam
15115 function;
15116 <pre>
15117 SEEK_CUR
15118 SEEK_END
15119 SEEK_SET
15120 </pre>
15121 which expand to integer constant expressions with distinct values, suitable for use as the
15122 third argument to the fseek function;
15123 <pre>
15124 TMP_MAX
15125 </pre>
15126 which expands to an integer constant expression that is the minimum number of unique
15127 file names that can be generated by the tmpnam function;
15128 <pre>
15129 stderr
15130 stdin
15131 stdout
15132 </pre>
15133 which are expressions of type ''pointer to FILE'' that point to the FILE objects
15134 associated, respectively, with the standard error, input, and output streams.
15135 <p><!--para 4 -->
15136 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide character input
15137 and output. The wide character input/output functions described in that subclause
15138 provide operations analogous to most of those described here, except that the
15139 fundamental units internal to the program are wide characters. The external
15140 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
15142 <p><!--para 5 -->
15143 The input/output functions are given the following collective terms:
15144 <ul>
15145 <li> The wide character input functions -- those functions described in <a href="#7.28">7.28</a> that perform
15146 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
15147 fwscanf, wscanf, vfwscanf, and vwscanf.
15148 <li> The wide character output functions -- those functions described in <a href="#7.28">7.28</a> that perform
15149 output from wide characters and wide strings: fputwc, fputws, putwc,
15150 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
15153 <!--page 316 -->
15154 <li> The wide character input/output functions -- the union of the ungetwc function, the
15155 wide character input functions, and the wide character output functions.
15156 <li> The byte input/output functions -- those functions described in this subclause that
15157 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
15158 fscanf, fwrite, getc, getchar, printf, putc, putchar, puts, scanf, *
15159 ungetc, vfprintf, vfscanf, vprintf, and vscanf.
15160 </ul>
15161 <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
15162 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>).
15164 <p><b>Footnotes</b>
15165 <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
15166 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
15167 string. Of course, file name string contents are subject to other system-specific constraints; therefore
15168 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
15169 </small>
15172 <p><!--para 1 -->
15173 Input and output, whether to or from physical devices such as terminals and tape drives,
15174 or whether to or from files supported on structured storage devices, are mapped into
15175 logical data streams, whose properties are more uniform than their various inputs and
15176 outputs. Two forms of mapping are supported, for text streams and for binary
15178 <p><!--para 2 -->
15179 A text stream is an ordered sequence of characters composed into lines, each line
15180 consisting of zero or more characters plus a terminating new-line character. Whether the
15181 last line requires a terminating new-line character is implementation-defined. Characters
15182 may have to be added, altered, or deleted on input and output to conform to differing
15183 conventions for representing text in the host environment. Thus, there need not be a one-
15184 to-one correspondence between the characters in a stream and those in the external
15185 representation. Data read in from a text stream will necessarily compare equal to the data
15186 that were earlier written out to that stream only if: the data consist only of printing
15187 characters and the control characters horizontal tab and new-line; no new-line character is
15188 immediately preceded by space characters; and the last character is a new-line character.
15189 Whether space characters that are written out immediately before a new-line character
15190 appear when read in is implementation-defined.
15191 <p><!--para 3 -->
15192 A binary stream is an ordered sequence of characters that can transparently record
15193 internal data. Data read in from a binary stream shall compare equal to the data that were
15194 earlier written out to that stream, under the same implementation. Such a stream may,
15195 however, have an implementation-defined number of null characters appended to the end
15196 of the stream.
15197 <p><!--para 4 -->
15198 Each stream has an orientation. After a stream is associated with an external file, but
15199 before any operations are performed on it, the stream is without orientation. Once a wide
15200 character input/output function has been applied to a stream without orientation, the
15203 <!--page 317 -->
15204 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
15205 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
15206 Only a call to the freopen function or the fwide function can otherwise alter the
15207 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note260"><b>260)</b></a></sup>
15208 <p><!--para 5 -->
15209 Byte input/output functions shall not be applied to a wide-oriented stream and wide
15210 character input/output functions shall not be applied to a byte-oriented stream. The
15211 remaining stream operations do not affect, and are not affected by, a stream's orientation,
15212 except for the following additional restrictions:
15213 <ul>
15214 <li> Binary wide-oriented streams have the file-positioning restrictions ascribed to both
15215 text and binary streams.
15216 <li> For wide-oriented streams, after a successful call to a file-positioning function that
15217 leaves the file position indicator prior to the end-of-file, a wide character output
15218 function can overwrite a partial multibyte character; any file contents beyond the
15219 byte(s) written are henceforth indeterminate.
15220 </ul>
15221 <p><!--para 6 -->
15222 Each wide-oriented stream has an associated mbstate_t object that stores the current
15223 parse state of the stream. A successful call to fgetpos stores a representation of the
15224 value of this mbstate_t object as part of the value of the fpos_t object. A later
15225 successful call to fsetpos using the same stored fpos_t value restores the value of
15226 the associated mbstate_t object as well as the position within the controlled stream.
15227 <p><b>Environmental limits</b>
15228 <p><!--para 7 -->
15229 An implementation shall support text files with lines containing at least 254 characters,
15230 including the terminating new-line character. The value of the macro BUFSIZ shall be at
15231 least 256.
15232 <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>),
15233 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
15239 <!--page 318 -->
15241 <p><b>Footnotes</b>
15242 <p><small><a name="note259" href="#note259">259)</a> An implementation need not distinguish between text streams and binary streams. In such an
15243 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
15244 line.
15245 </small>
15246 <p><small><a name="note260" href="#note260">260)</a> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
15247 </small>
15250 <p><!--para 1 -->
15251 A stream is associated with an external file (which may be a physical device) by opening
15252 a file, which may involve creating a new file. Creating an existing file causes its former
15253 contents to be discarded, if necessary. If a file can support positioning requests (such as a
15254 disk file, as opposed to a terminal), then a file position indicator associated with the
15255 stream is positioned at the start (character number zero) of the file, unless the file is
15256 opened with append mode in which case it is implementation-defined whether the file
15257 position indicator is initially positioned at the beginning or the end of the file. The file
15258 position indicator is maintained by subsequent reads, writes, and positioning requests, to
15259 facilitate an orderly progression through the file.
15260 <p><!--para 2 -->
15261 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
15262 stream causes the associated file to be truncated beyond that point is implementation-
15263 defined.
15264 <p><!--para 3 -->
15265 When a stream is unbuffered, characters are intended to appear from the source or at the
15266 destination as soon as possible. Otherwise characters may be accumulated and
15267 transmitted to or from the host environment as a block. When a stream is fully buffered,
15268 characters are intended to be transmitted to or from the host environment as a block when
15269 a buffer is filled. When a stream is line buffered, characters are intended to be
15270 transmitted to or from the host environment as a block when a new-line character is
15271 encountered. Furthermore, characters are intended to be transmitted as a block to the host
15272 environment when a buffer is filled, when input is requested on an unbuffered stream, or
15273 when input is requested on a line buffered stream that requires the transmission of
15274 characters from the host environment. Support for these characteristics is
15275 implementation-defined, and may be affected via the setbuf and setvbuf functions.
15276 <p><!--para 4 -->
15277 A file may be disassociated from a controlling stream by closing the file. Output streams
15278 are flushed (any unwritten buffer contents are transmitted to the host environment) before
15279 the stream is disassociated from the file. The value of a pointer to a FILE object is
15280 indeterminate after the associated file is closed (including the standard text streams).
15281 Whether a file of zero length (on which no characters have been written by an output
15282 stream) actually exists is implementation-defined.
15283 <p><!--para 5 -->
15284 The file may be subsequently reopened, by the same or another program execution, and
15285 its contents reclaimed or modified (if it can be repositioned at its start). If the main
15286 function returns to its original caller, or if the exit function is called, all open files are
15287 closed (hence all output streams are flushed) before program termination. Other paths to
15288 program termination, such as calling the abort function, need not close all files
15289 properly.
15290 <p><!--para 6 -->
15291 The address of the FILE object used to control a stream may be significant; a copy of a
15292 FILE object need not serve in place of the original.
15293 <!--page 319 -->
15294 <p><!--para 7 -->
15295 At program startup, three text streams are predefined and need not be opened explicitly
15296 <ul>
15297 <li> standard input (for reading conventional input), standard output (for writing
15298 </ul>
15299 conventional output), and standard error (for writing diagnostic output). As initially
15300 opened, the standard error stream is not fully buffered; the standard input and standard
15301 output streams are fully buffered if and only if the stream can be determined not to refer
15302 to an interactive device.
15303 <p><!--para 8 -->
15304 Functions that open additional (nontemporary) files require a file name, which is a string.
15305 The rules for composing valid file names are implementation-defined. Whether the same
15306 file can be simultaneously open multiple times is also implementation-defined.
15307 <p><!--para 9 -->
15308 Although both text and binary wide-oriented streams are conceptually sequences of wide
15309 characters, the external file associated with a wide-oriented stream is a sequence of
15310 multibyte characters, generalized as follows:
15311 <ul>
15312 <li> Multibyte encodings within files may contain embedded null bytes (unlike multibyte
15313 encodings valid for use internal to the program).
15314 <li> A file need not begin nor end in the initial shift state.<sup><a href="#note261"><b>261)</b></a></sup>
15315 </ul>
15316 <p><!--para 10 -->
15317 Moreover, the encodings used for multibyte characters may differ among files. Both the
15318 nature and choice of such encodings are implementation-defined.
15319 <p><!--para 11 -->
15320 The wide character input functions read multibyte characters from the stream and convert
15321 them to wide characters as if they were read by successive calls to the fgetwc function.
15322 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
15323 described by the stream's own mbstate_t object. The byte input functions read
15324 characters from the stream as if by successive calls to the fgetc function.
15325 <p><!--para 12 -->
15326 The wide character output functions convert wide characters to multibyte characters and
15327 write them to the stream as if they were written by successive calls to the fputwc
15328 function. Each conversion occurs as if by a call to the wcrtomb function, with the
15329 conversion state described by the stream's own mbstate_t object. The byte output
15330 functions write characters to the stream as if by successive calls to the fputc function.
15331 <p><!--para 13 -->
15332 In some cases, some of the byte input/output functions also perform conversions between
15333 multibyte characters and wide characters. These conversions also occur as if by calls to
15334 the mbrtowc and wcrtomb functions.
15335 <p><!--para 14 -->
15336 An encoding error occurs if the character sequence presented to the underlying
15337 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
15338 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
15341 <!--page 320 -->
15342 multibyte character. The wide character input/output functions and the byte input/output
15343 functions store the value of the macro EILSEQ in errno if and only if an encoding error
15344 occurs.
15345 <p><b>Environmental limits</b>
15346 <p><!--para 15 -->
15347 The value of FOPEN_MAX shall be at least eight, including the three standard text
15348 streams.
15349 <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
15350 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
15351 (<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
15352 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
15353 (<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>).
15355 <p><b>Footnotes</b>
15356 <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
15357 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
15358 with state-dependent encoding that does not assuredly end in the initial shift state.
15359 </small>
15364 <p><b>Synopsis</b>
15365 <p><!--para 1 -->
15366 <pre>
15368 int remove(const char *filename);
15369 </pre>
15370 <p><b>Description</b>
15371 <p><!--para 2 -->
15372 The remove function causes the file whose name is the string pointed to by filename
15373 to be no longer accessible by that name. A subsequent attempt to open that file using that
15374 name will fail, unless it is created anew. If the file is open, the behavior of the remove
15375 function is implementation-defined.
15376 <p><b>Returns</b>
15377 <p><!--para 3 -->
15378 The remove function returns zero if the operation succeeds, nonzero if it fails.
15381 <p><b>Synopsis</b>
15382 <p><!--para 1 -->
15383 <pre>
15385 int rename(const char *old, const char *new);
15386 </pre>
15387 <p><b>Description</b>
15388 <p><!--para 2 -->
15389 The rename function causes the file whose name is the string pointed to by old to be
15390 henceforth known by the name given by the string pointed to by new. The file named
15391 old is no longer accessible by that name. If a file named by the string pointed to by new
15392 exists prior to the call to the rename function, the behavior is implementation-defined.
15393 <!--page 321 -->
15394 <p><b>Returns</b>
15395 <p><!--para 3 -->
15396 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note262"><b>262)</b></a></sup> in
15397 which case if the file existed previously it is still known by its original name.
15399 <p><b>Footnotes</b>
15400 <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
15401 or that it is necessary to copy its contents to effectuate its renaming.
15402 </small>
15405 <p><b>Synopsis</b>
15406 <p><!--para 1 -->
15407 <pre>
15409 FILE *tmpfile(void);
15410 </pre>
15411 <p><b>Description</b>
15412 <p><!--para 2 -->
15413 The tmpfile function creates a temporary binary file that is different from any other
15414 existing file and that will automatically be removed when it is closed or at program
15415 termination. If the program terminates abnormally, whether an open temporary file is
15417 <p><b>Recommended practice</b>
15418 <p><!--para 3 -->
15419 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
15420 program (this limit may be shared with tmpnam) and there should be no limit on the
15421 number simultaneously open other than this limit and any limit on the number of open
15422 files (FOPEN_MAX).
15423 <p><b>Returns</b>
15424 <p><!--para 4 -->
15425 The tmpfile function returns a pointer to the stream of the file that it created. If the file
15426 cannot be created, the tmpfile function returns a null pointer.
15430 <p><b>Synopsis</b>
15431 <p><!--para 1 -->
15432 <pre>
15434 char *tmpnam(char *s);
15435 </pre>
15436 <p><b>Description</b>
15437 <p><!--para 2 -->
15438 The tmpnam function generates a string that is a valid file name and that is not the same
15439 as the name of an existing file.<sup><a href="#note263"><b>263)</b></a></sup> The function is potentially capable of generating at
15442 <!--page 322 -->
15443 least TMP_MAX different strings, but any or all of them may already be in use by existing
15444 files and thus not be suitable return values.
15445 <p><!--para 3 -->
15446 The tmpnam function generates a different string each time it is called.
15447 <p><!--para 4 -->
15448 Calls to the tmpnam function with a null pointer argument may introduce data races with
15449 each other. The implementation shall behave as if no library function calls the tmpnam
15450 function.
15451 <p><b>Returns</b>
15452 <p><!--para 5 -->
15453 If no suitable string can be generated, the tmpnam function returns a null pointer.
15454 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
15455 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
15456 function may modify the same object). If the argument is not a null pointer, it is assumed
15457 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
15458 in that array and returns the argument as its value.
15459 <p><b>Environmental limits</b>
15460 <p><!--para 6 -->
15461 The value of the macro TMP_MAX shall be at least 25.
15463 <p><b>Footnotes</b>
15464 <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
15465 their names should not collide with those generated by conventional naming rules for the
15466 implementation. It is still necessary to use the remove function to remove such files when their use
15467 is ended, and before program termination.
15468 </small>
15473 <p><b>Synopsis</b>
15474 <p><!--para 1 -->
15475 <pre>
15477 int fclose(FILE *stream);
15478 </pre>
15479 <p><b>Description</b>
15480 <p><!--para 2 -->
15481 A successful call to the fclose function causes the stream pointed to by stream to be
15482 flushed and the associated file to be closed. Any unwritten buffered data for the stream
15483 are delivered to the host environment to be written to the file; any unread buffered data
15484 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
15485 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
15486 (and deallocated if it was automatically allocated).
15487 <p><b>Returns</b>
15488 <p><!--para 3 -->
15489 The fclose function returns zero if the stream was successfully closed, or EOF if any
15490 errors were detected.
15491 <!--page 323 -->
15494 <p><b>Synopsis</b>
15495 <p><!--para 1 -->
15496 <pre>
15498 int fflush(FILE *stream);
15499 </pre>
15500 <p><b>Description</b>
15501 <p><!--para 2 -->
15502 If stream points to an output stream or an update stream in which the most recent
15503 operation was not input, the fflush function causes any unwritten data for that stream
15504 to be delivered to the host environment to be written to the file; otherwise, the behavior is
15505 undefined.
15506 <p><!--para 3 -->
15507 If stream is a null pointer, the fflush function performs this flushing action on all
15508 streams for which the behavior is defined above.
15509 <p><b>Returns</b>
15510 <p><!--para 4 -->
15511 The fflush function sets the error indicator for the stream and returns EOF if a write
15512 error occurs, otherwise it returns zero.
15516 <p><b>Synopsis</b>
15517 <p><!--para 1 -->
15518 <pre>
15520 FILE *fopen(const char * restrict filename,
15521 const char * restrict mode);
15522 </pre>
15523 <p><b>Description</b>
15524 <p><!--para 2 -->
15525 The fopen function opens the file whose name is the string pointed to by filename,
15526 and associates a stream with it.
15527 <p><!--para 3 -->
15528 The argument mode points to a string. If the string is one of the following, the file is
15529 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note264"><b>264)</b></a></sup>
15530 r open text file for reading
15531 w truncate to zero length or create text file for writing
15532 wx create text file for writing
15533 a append; open or create text file for writing at end-of-file
15534 rb open binary file for reading
15535 wb truncate to zero length or create binary file for writing
15538 <!--page 324 -->
15539 wbx create binary file for writing
15540 ab append; open or create binary file for writing at end-of-file
15541 r+ open text file for update (reading and writing)
15542 w+ truncate to zero length or create text file for update
15543 w+x create text file for update
15544 a+ append; open or create text file for update, writing at end-of-file
15545 r+b or rb+ open binary file for update (reading and writing)
15546 w+b or wb+ truncate to zero length or create binary file for update
15547 w+bx or wb+x create binary file for update
15548 a+b or ab+ append; open or create binary file for update, writing at end-of-file
15549 <p><!--para 4 -->
15550 Opening a file with read mode ('r' as the first character in the mode argument) fails if
15551 the file does not exist or cannot be read.
15552 <p><!--para 5 -->
15553 Opening a file with exclusive mode ('x' as the last character in the mode argument)
15554 fails if the file already exists or cannot be created. Otherwise, the file is created with
15555 exclusive (also known as non-shared) access to the extent that the underlying system
15556 supports exclusive access.
15557 <p><!--para 6 -->
15558 Opening a file with append mode ('a' as the first character in the mode argument)
15559 causes all subsequent writes to the file to be forced to the then current end-of-file,
15560 regardless of intervening calls to the fseek function. In some implementations, opening
15561 a binary file with append mode ('b' as the second or third character in the above list of
15562 mode argument values) may initially position the file position indicator for the stream
15563 beyond the last data written, because of null character padding.
15564 <p><!--para 7 -->
15565 When a file is opened with update mode ('+' as the second or third character in the
15566 above list of mode argument values), both input and output may be performed on the
15567 associated stream. However, output shall not be directly followed by input without an
15568 intervening call to the fflush function or to a file positioning function (fseek,
15569 fsetpos, or rewind), and input shall not be directly followed by output without an
15570 intervening call to a file positioning function, unless the input operation encounters end-
15571 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
15572 binary stream in some implementations.
15573 <p><!--para 8 -->
15574 When opened, a stream is fully buffered if and only if it can be determined not to refer to
15575 an interactive device. The error and end-of-file indicators for the stream are cleared.
15576 <p><b>Returns</b>
15577 <p><!--para 9 -->
15578 The fopen function returns a pointer to the object controlling the stream. If the open
15579 operation fails, fopen returns a null pointer.
15581 <!--page 325 -->
15583 <p><b>Footnotes</b>
15584 <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
15585 remaining characters, or it might use them to select different kinds of a file (some of which might not
15587 </small>
15590 <p><b>Synopsis</b>
15591 <p><!--para 1 -->
15592 <pre>
15594 FILE *freopen(const char * restrict filename,
15595 const char * restrict mode,
15596 FILE * restrict stream);
15597 </pre>
15598 <p><b>Description</b>
15599 <p><!--para 2 -->
15600 The freopen function opens the file whose name is the string pointed to by filename
15601 and associates the stream pointed to by stream with it. The mode argument is used just
15603 <p><!--para 3 -->
15604 If filename is a null pointer, the freopen function attempts to change the mode of
15605 the stream to that specified by mode, as if the name of the file currently associated with
15606 the stream had been used. It is implementation-defined which changes of mode are
15607 permitted (if any), and under what circumstances.
15608 <p><!--para 4 -->
15609 The freopen function first attempts to close any file that is associated with the specified
15610 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
15611 stream are cleared.
15612 <p><b>Returns</b>
15613 <p><!--para 5 -->
15614 The freopen function returns a null pointer if the open operation fails. Otherwise,
15615 freopen returns the value of stream.
15617 <p><b>Footnotes</b>
15618 <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
15619 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
15620 returned by the fopen function may be assigned.
15621 </small>
15624 <p><b>Synopsis</b>
15625 <p><!--para 1 -->
15626 <pre>
15628 void setbuf(FILE * restrict stream,
15629 char * restrict buf);
15630 </pre>
15631 <p><b>Description</b>
15632 <p><!--para 2 -->
15633 Except that it returns no value, the setbuf function is equivalent to the setvbuf
15634 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
15635 is a null pointer), with the value _IONBF for mode.
15640 <!--page 326 -->
15641 <p><b>Returns</b>
15642 <p><!--para 3 -->
15643 The setbuf function returns no value.
15647 <p><b>Synopsis</b>
15648 <p><!--para 1 -->
15649 <pre>
15651 int setvbuf(FILE * restrict stream,
15652 char * restrict buf,
15653 int mode, size_t size);
15654 </pre>
15655 <p><b>Description</b>
15656 <p><!--para 2 -->
15657 The setvbuf function may be used only after the stream pointed to by stream has
15658 been associated with an open file and before any other operation (other than an
15659 unsuccessful call to setvbuf) is performed on the stream. The argument mode
15660 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
15661 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
15662 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
15663 used instead of a buffer allocated by the setvbuf function<sup><a href="#note266"><b>266)</b></a></sup> and the argument size
15664 specifies the size of the array; otherwise, size may determine the size of a buffer
15665 allocated by the setvbuf function. The contents of the array at any time are
15666 indeterminate.
15667 <p><b>Returns</b>
15668 <p><!--para 3 -->
15669 The setvbuf function returns zero on success, or nonzero if an invalid value is given
15670 for mode or if the request cannot be honored.
15675 <!--page 327 -->
15677 <p><b>Footnotes</b>
15678 <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
15679 before a buffer that has automatic storage duration is deallocated upon block exit.
15680 </small>
15683 <p><!--para 1 -->
15684 The formatted input/output functions shall behave as if there is a sequence point after the
15687 <p><b>Footnotes</b>
15688 <p><small><a name="note267" href="#note267">267)</a> The fprintf functions perform writes to memory for the %n specifier.
15689 </small>
15692 <p><b>Synopsis</b>
15693 <p><!--para 1 -->
15694 <pre>
15696 int fprintf(FILE * restrict stream,
15697 const char * restrict format, ...);
15698 </pre>
15699 <p><b>Description</b>
15700 <p><!--para 2 -->
15701 The fprintf function writes output to the stream pointed to by stream, under control
15702 of the string pointed to by format that specifies how subsequent arguments are
15703 converted for output. If there are insufficient arguments for the format, the behavior is
15704 undefined. If the format is exhausted while arguments remain, the excess arguments are
15705 evaluated (as always) but are otherwise ignored. The fprintf function returns when
15706 the end of the format string is encountered.
15707 <p><!--para 3 -->
15708 The format shall be a multibyte character sequence, beginning and ending in its initial
15709 shift state. The format is composed of zero or more directives: ordinary multibyte
15710 characters (not %), which are copied unchanged to the output stream; and conversion
15711 specifications, each of which results in fetching zero or more subsequent arguments,
15712 converting them, if applicable, according to the corresponding conversion specifier, and
15713 then writing the result to the output stream.
15714 <p><!--para 4 -->
15715 Each conversion specification is introduced by the character %. After the %, the following
15716 appear in sequence:
15717 <ul>
15718 <li> Zero or more flags (in any order) that modify the meaning of the conversion
15719 specification.
15720 <li> An optional minimum field width. If the converted value has fewer characters than the
15721 field width, it is padded with spaces (by default) on the left (or right, if the left
15722 adjustment flag, described later, has been given) to the field width. The field width
15723 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note268"><b>268)</b></a></sup>
15724 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
15725 o, u, x, and X conversions, the number of digits to appear after the decimal-point
15726 character for a, A, e, E, f, and F conversions, the maximum number of significant
15727 digits for the g and G conversions, or the maximum number of bytes to be written for
15730 <!--page 328 -->
15731 s conversions. The precision takes the form of a period (.) followed either by an
15732 asterisk * (described later) or by an optional decimal integer; if only the period is
15733 specified, the precision is taken as zero. If a precision appears with any other
15734 conversion specifier, the behavior is undefined.
15735 <li> An optional length modifier that specifies the size of the argument.
15736 <li> A conversion specifier character that specifies the type of conversion to be applied.
15737 </ul>
15738 <p><!--para 5 -->
15739 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
15740 this case, an int argument supplies the field width or precision. The arguments
15741 specifying field width, or precision, or both, shall appear (in that order) before the
15742 argument (if any) to be converted. A negative field width argument is taken as a - flag
15743 followed by a positive field width. A negative precision argument is taken as if the
15744 precision were omitted.
15745 <p><!--para 6 -->
15746 The flag characters and their meanings are:
15747 - The result of the conversion is left-justified within the field. (It is right-justified if
15748 <pre>
15749 this flag is not specified.)
15750 </pre>
15751 + The result of a signed conversion always begins with a plus or minus sign. (It
15752 <pre>
15753 begins with a sign only when a negative value is converted if this flag is not
15755 </pre>
15756 space If the first character of a signed conversion is not a sign, or if a signed conversion
15757 <pre>
15758 results in no characters, a space is prefixed to the result. If the space and + flags
15759 both appear, the space flag is ignored.
15760 </pre>
15761 # The result is converted to an ''alternative form''. For o conversion, it increases
15762 <pre>
15763 the precision, if and only if necessary, to force the first digit of the result to be a
15764 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
15765 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
15766 and G conversions, the result of converting a floating-point number always
15767 contains a decimal-point character, even if no digits follow it. (Normally, a
15768 decimal-point character appears in the result of these conversions only if a digit
15769 follows it.) For g and G conversions, trailing zeros are not removed from the
15770 result. For other conversions, the behavior is undefined.
15771 </pre>
15772 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
15773 <pre>
15774 (following any indication of sign or base) are used to pad to the field width rather
15775 than performing space padding, except when converting an infinity or NaN. If the
15776 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
15777 </pre>
15780 <!--page 329 -->
15781 <pre>
15782 conversions, if a precision is specified, the 0 flag is ignored. For other
15783 conversions, the behavior is undefined.
15784 </pre>
15785 <p><!--para 7 -->
15786 The length modifiers and their meanings are:
15787 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15788 <pre>
15789 signed char or unsigned char argument (the argument will have
15790 been promoted according to the integer promotions, but its value shall be
15791 converted to signed char or unsigned char before printing); or that
15792 a following n conversion specifier applies to a pointer to a signed char
15793 argument.
15794 </pre>
15795 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15796 <pre>
15797 short int or unsigned short int argument (the argument will
15798 have been promoted according to the integer promotions, but its value shall
15799 be converted to short int or unsigned short int before printing);
15800 or that a following n conversion specifier applies to a pointer to a short
15801 int argument.
15802 </pre>
15803 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15804 <pre>
15805 long int or unsigned long int argument; that a following n
15806 conversion specifier applies to a pointer to a long int argument; that a
15807 following c conversion specifier applies to a wint_t argument; that a
15808 following s conversion specifier applies to a pointer to a wchar_t
15809 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
15810 specifier.
15811 </pre>
15812 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15813 <pre>
15814 long long int or unsigned long long int argument; or that a
15815 following n conversion specifier applies to a pointer to a long long int
15816 argument.
15817 </pre>
15818 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
15819 <pre>
15820 an intmax_t or uintmax_t argument; or that a following n conversion
15821 specifier applies to a pointer to an intmax_t argument.
15822 </pre>
15823 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15824 <pre>
15825 size_t or the corresponding signed integer type argument; or that a
15826 following n conversion specifier applies to a pointer to a signed integer type
15827 corresponding to size_t argument.
15828 </pre>
15829 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15830 <!--page 330 -->
15831 <pre>
15832 ptrdiff_t or the corresponding unsigned integer type argument; or that a
15833 following n conversion specifier applies to a pointer to a ptrdiff_t
15834 argument.
15835 </pre>
15836 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
15837 <pre>
15838 applies to a long double argument.
15839 </pre>
15840 If a length modifier appears with any conversion specifier other than as specified above,
15841 the behavior is undefined.
15842 <p><!--para 8 -->
15843 The conversion specifiers and their meanings are:
15844 d,i The int argument is converted to signed decimal in the style [-]dddd. The
15845 <pre>
15846 precision specifies the minimum number of digits to appear; if the value
15847 being converted can be represented in fewer digits, it is expanded with
15848 leading zeros. The default precision is 1. The result of converting a zero
15849 value with a precision of zero is no characters.
15850 </pre>
15851 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
15852 <pre>
15853 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
15854 letters abcdef are used for x conversion and the letters ABCDEF for X
15855 conversion. The precision specifies the minimum number of digits to appear;
15856 if the value being converted can be represented in fewer digits, it is expanded
15857 with leading zeros. The default precision is 1. The result of converting a
15858 zero value with a precision of zero is no characters.
15859 </pre>
15860 f,F A double argument representing a floating-point number is converted to
15861 <pre>
15862 decimal notation in the style [-]ddd.ddd, where the number of digits after
15863 the decimal-point character is equal to the precision specification. If the
15864 precision is missing, it is taken as 6; if the precision is zero and the # flag is
15865 not specified, no decimal-point character appears. If a decimal-point
15866 character appears, at least one digit appears before it. The value is rounded to
15867 the appropriate number of digits.
15868 A double argument representing an infinity is converted in one of the styles
15869 [-]inf or [-]infinity -- which style is implementation-defined. A
15870 double argument representing a NaN is converted in one of the styles
15871 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
15872 any n-char-sequence, is implementation-defined. The F conversion specifier
15873 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
15875 </pre>
15876 e,E A double argument representing a floating-point number is converted in the
15877 <pre>
15878 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
15879 argument is nonzero) before the decimal-point character and the number of
15880 digits after it is equal to the precision; if the precision is missing, it is taken as
15881 </pre>
15884 <!--page 331 -->
15885 <pre>
15886 6; if the precision is zero and the # flag is not specified, no decimal-point
15887 character appears. The value is rounded to the appropriate number of digits.
15888 The E conversion specifier produces a number with E instead of e
15889 introducing the exponent. The exponent always contains at least two digits,
15890 and only as many more digits as necessary to represent the exponent. If the
15891 value is zero, the exponent is zero.
15892 A double argument representing an infinity or NaN is converted in the style
15893 of an f or F conversion specifier.
15894 </pre>
15895 g,G A double argument representing a floating-point number is converted in
15896 <pre>
15897 style f or e (or in style F or E in the case of a G conversion specifier),
15898 depending on the value converted and the precision. Let P equal the
15899 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
15900 Then, if a conversion with style E would have an exponent of X:
15901 -- if P > X >= -4, the conversion is with style f (or F) and precision
15902 P - (X + 1).
15903 -- otherwise, the conversion is with style e (or E) and precision P - 1.
15904 Finally, unless the # flag is used, any trailing zeros are removed from the
15905 fractional portion of the result and the decimal-point character is removed if
15906 there is no fractional portion remaining.
15907 A double argument representing an infinity or NaN is converted in the style
15908 of an f or F conversion specifier.
15909 </pre>
15910 a,A A double argument representing a floating-point number is converted in the
15911 <pre>
15912 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
15913 nonzero if the argument is a normalized floating-point number and is
15914 otherwise unspecified) before the decimal-point character<sup><a href="#note271"><b>271)</b></a></sup> and the number
15915 of hexadecimal digits after it is equal to the precision; if the precision is
15916 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
15917 an exact representation of the value; if the precision is missing and
15918 FLT_RADIX is not a power of 2, then the precision is sufficient to
15919 </pre>
15924 <!--page 332 -->
15925 <pre>
15926 distinguish<sup><a href="#note272"><b>272)</b></a></sup> values of type double, except that trailing zeros may be
15927 omitted; if the precision is zero and the # flag is not specified, no decimal-
15928 point character appears. The letters abcdef are used for a conversion and
15929 the letters ABCDEF for A conversion. The A conversion specifier produces a
15930 number with X and P instead of x and p. The exponent always contains at
15931 least one digit, and only as many more digits as necessary to represent the
15932 decimal exponent of 2. If the value is zero, the exponent is zero.
15933 A double argument representing an infinity or NaN is converted in the style
15934 of an f or F conversion specifier.
15935 </pre>
15936 c If no l length modifier is present, the int argument is converted to an
15937 <pre>
15938 unsigned char, and the resulting character is written.
15939 If an l length modifier is present, the wint_t argument is converted as if by
15940 an ls conversion specification with no precision and an argument that points
15941 to the initial element of a two-element array of wchar_t, the first element
15942 containing the wint_t argument to the lc conversion specification and the
15943 second a null wide character.
15944 </pre>
15945 s If no l length modifier is present, the argument shall be a pointer to the initial
15946 <pre>
15947 element of an array of character type.<sup><a href="#note273"><b>273)</b></a></sup> Characters from the array are
15948 written up to (but not including) the terminating null character. If the
15949 precision is specified, no more than that many bytes are written. If the
15950 precision is not specified or is greater than the size of the array, the array shall
15951 contain a null character.
15952 If an l length modifier is present, the argument shall be a pointer to the initial
15953 element of an array of wchar_t type. Wide characters from the array are
15954 converted to multibyte characters (each as if by a call to the wcrtomb
15955 function, with the conversion state described by an mbstate_t object
15956 initialized to zero before the first wide character is converted) up to and
15957 including a terminating null wide character. The resulting multibyte
15958 characters are written up to (but not including) the terminating null character
15959 (byte). If no precision is specified, the array shall contain a null wide
15960 character. If a precision is specified, no more than that many bytes are
15961 written (including shift sequences, if any), and the array shall contain a null
15962 wide character if, to equal the multibyte character sequence length given by
15963 </pre>
15965 <!--page 333 -->
15966 <pre>
15967 the precision, the function would need to access a wide character one past the
15968 end of the array. In no case is a partial multibyte character written.<sup><a href="#note274"><b>274)</b></a></sup>
15969 </pre>
15970 p The argument shall be a pointer to void. The value of the pointer is
15971 <pre>
15972 converted to a sequence of printing characters, in an implementation-defined
15973 manner.
15974 </pre>
15975 n The argument shall be a pointer to signed integer into which is written the
15976 <pre>
15977 number of characters written to the output stream so far by this call to
15978 fprintf. No argument is converted, but one is consumed. If the conversion
15979 specification includes any flags, a field width, or a precision, the behavior is
15980 undefined.
15981 </pre>
15982 % A % character is written. No argument is converted. The complete
15983 <pre>
15984 conversion specification shall be %%.
15985 </pre>
15986 <p><!--para 9 -->
15987 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note275"><b>275)</b></a></sup> If any argument is
15988 not the correct type for the corresponding conversion specification, the behavior is
15989 undefined.
15990 <p><!--para 10 -->
15991 In no case does a nonexistent or small field width cause truncation of a field; if the result
15992 of a conversion is wider than the field width, the field is expanded to contain the
15993 conversion result.
15994 <p><!--para 11 -->
15995 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
15996 to a hexadecimal floating number with the given precision.
15997 <p><b>Recommended practice</b>
15998 <p><!--para 12 -->
15999 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
16000 representable in the given precision, the result should be one of the two adjacent numbers
16001 in hexadecimal floating style with the given precision, with the extra stipulation that the
16002 error should have a correct sign for the current rounding direction.
16003 <p><!--para 13 -->
16004 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
16005 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note276"><b>276)</b></a></sup> If the number of
16006 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
16007 representable with DECIMAL_DIG digits, then the result should be an exact
16008 representation with trailing zeros. Otherwise, the source value is bounded by two
16009 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
16012 <!--page 334 -->
16013 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
16014 the error should have a correct sign for the current rounding direction.
16015 <p><b>Returns</b>
16016 <p><!--para 14 -->
16017 The fprintf function returns the number of characters transmitted, or a negative value
16018 if an output or encoding error occurred.
16019 <p><b>Environmental limits</b>
16020 <p><!--para 15 -->
16021 The number of characters that can be produced by any single conversion shall be at least
16022 4095.
16023 <p><!--para 16 -->
16024 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
16025 places:
16026 <pre>
16029 /* ... */
16030 char *weekday, *month; // pointers to strings
16031 int day, hour, min;
16033 weekday, month, day, hour, min);
16035 </pre>
16037 <p><!--para 17 -->
16038 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
16039 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
16040 the first of which is denoted here by a and the second by an uppercase letter.
16041 <p><!--para 18 -->
16042 Given the following wide string with length seven,
16043 <pre>
16045 </pre>
16046 the seven calls
16047 <pre>
16055 </pre>
16056 will print the following seven lines:
16057 <pre>
16058 |1234567890123|
16059 | X Yabc Z W|
16060 | X Yabc Z |
16061 | X Yabc Z|
16062 | X Yabc Z W|
16063 | abc Z W|
16064 | Z|
16065 </pre>
16067 <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>).
16068 <!--page 335 -->
16070 <p><b>Footnotes</b>
16071 <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.
16072 </small>
16073 <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,
16074 include a minus sign.
16075 </small>
16076 <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;
16077 the # and 0 flag characters have no effect.
16078 </small>
16079 <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
16080 that subsequent digits align to nibble (4-bit) boundaries.
16081 </small>
16082 <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
16083 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
16084 might suffice depending on the implementation's scheme for determining the digit to the left of the
16085 decimal-point character.
16086 </small>
16087 <p><small><a name="note273" href="#note273">273)</a> No special provisions are made for multibyte characters.
16088 </small>
16089 <p><small><a name="note274" href="#note274">274)</a> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
16090 </small>
16091 <p><small><a name="note275" href="#note275">275)</a> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
16092 </small>
16093 <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
16094 given format specifier. The number of significant digits is determined by the format specifier, and in
16095 the case of fixed-point conversion by the source value as well.
16096 </small>
16099 <p><b>Synopsis</b>
16100 <p><!--para 1 -->
16101 <pre>
16103 int fscanf(FILE * restrict stream,
16104 const char * restrict format, ...);
16105 </pre>
16106 <p><b>Description</b>
16107 <p><!--para 2 -->
16108 The fscanf function reads input from the stream pointed to by stream, under control
16109 of the string pointed to by format that specifies the admissible input sequences and how
16110 they are to be converted for assignment, using subsequent arguments as pointers to the
16111 objects to receive the converted input. If there are insufficient arguments for the format,
16112 the behavior is undefined. If the format is exhausted while arguments remain, the excess
16113 arguments are evaluated (as always) but are otherwise ignored.
16114 <p><!--para 3 -->
16115 The format shall be a multibyte character sequence, beginning and ending in its initial
16116 shift state. The format is composed of zero or more directives: one or more white-space
16117 characters, an ordinary multibyte character (neither % nor a white-space character), or a
16118 conversion specification. Each conversion specification is introduced by the character %.
16119 After the %, the following appear in sequence:
16120 <ul>
16121 <li> An optional assignment-suppressing character *.
16122 <li> An optional decimal integer greater than zero that specifies the maximum field width
16123 (in characters).
16124 <li> An optional length modifier that specifies the size of the receiving object.
16125 <li> A conversion specifier character that specifies the type of conversion to be applied.
16126 </ul>
16127 <p><!--para 4 -->
16128 The fscanf function executes each directive of the format in turn. When all directives
16129 have been executed, or if a directive fails (as detailed below), the function returns.
16130 Failures are described as input failures (due to the occurrence of an encoding error or the
16131 unavailability of input characters), or matching failures (due to inappropriate input).
16132 <p><!--para 5 -->
16133 A directive composed of white-space character(s) is executed by reading input up to the
16134 first non-white-space character (which remains unread), or until no more characters can
16135 be read.
16136 <p><!--para 6 -->
16137 A directive that is an ordinary multibyte character is executed by reading the next
16138 characters of the stream. If any of those characters differ from the ones composing the
16139 directive, the directive fails and the differing and subsequent characters remain unread.
16140 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
16141 read, the directive fails.
16142 <p><!--para 7 -->
16143 A directive that is a conversion specification defines a set of matching input sequences, as
16144 described below for each specifier. A conversion specification is executed in the
16145 <!--page 336 -->
16146 following steps:
16147 <p><!--para 8 -->
16148 Input white-space characters (as specified by the isspace function) are skipped, unless
16149 the specification includes a [, c, or n specifier.<sup><a href="#note277"><b>277)</b></a></sup>
16150 <p><!--para 9 -->
16151 An input item is read from the stream, unless the specification includes an n specifier. An
16152 input item is defined as the longest sequence of input characters which does not exceed
16153 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>
16154 The first character, if any, after the input item remains unread. If the length of the input
16155 item is zero, the execution of the directive fails; this condition is a matching failure unless
16156 end-of-file, an encoding error, or a read error prevented input from the stream, in which
16157 case it is an input failure.
16158 <p><!--para 10 -->
16159 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
16160 count of input characters) is converted to a type appropriate to the conversion specifier. If
16161 the input item is not a matching sequence, the execution of the directive fails: this
16162 condition is a matching failure. Unless assignment suppression was indicated by a *, the
16163 result of the conversion is placed in the object pointed to by the first argument following
16164 the format argument that has not already received a conversion result. If this object
16165 does not have an appropriate type, or if the result of the conversion cannot be represented
16166 in the object, the behavior is undefined.
16167 <p><!--para 11 -->
16168 The length modifiers and their meanings are:
16169 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16170 <pre>
16171 to an argument with type pointer to signed char or unsigned char.
16172 </pre>
16173 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16174 <pre>
16175 to an argument with type pointer to short int or unsigned short
16176 int.
16177 </pre>
16178 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16179 <pre>
16180 to an argument with type pointer to long int or unsigned long
16181 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
16182 an argument with type pointer to double; or that a following c, s, or [
16183 conversion specifier applies to an argument with type pointer to wchar_t.
16184 </pre>
16185 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16186 <pre>
16187 to an argument with type pointer to long long int or unsigned
16188 long long int.
16189 </pre>
16193 <!--page 337 -->
16194 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16195 <pre>
16196 to an argument with type pointer to intmax_t or uintmax_t.
16197 </pre>
16198 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16199 <pre>
16200 to an argument with type pointer to size_t or the corresponding signed
16201 integer type.
16202 </pre>
16203 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16204 <pre>
16205 to an argument with type pointer to ptrdiff_t or the corresponding
16206 unsigned integer type.
16207 </pre>
16208 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16209 <pre>
16210 applies to an argument with type pointer to long double.
16211 </pre>
16212 If a length modifier appears with any conversion specifier other than as specified above,
16213 the behavior is undefined.
16214 <p><!--para 12 -->
16215 The conversion specifiers and their meanings are:
16216 d Matches an optionally signed decimal integer, whose format is the same as
16217 <pre>
16218 expected for the subject sequence of the strtol function with the value 10
16219 for the base argument. The corresponding argument shall be a pointer to
16220 signed integer.
16221 </pre>
16222 i Matches an optionally signed integer, whose format is the same as expected
16223 <pre>
16224 for the subject sequence of the strtol function with the value 0 for the
16225 base argument. The corresponding argument shall be a pointer to signed
16226 integer.
16227 </pre>
16228 o Matches an optionally signed octal integer, whose format is the same as
16229 <pre>
16230 expected for the subject sequence of the strtoul function with the value 8
16231 for the base argument. The corresponding argument shall be a pointer to
16232 unsigned integer.
16233 </pre>
16234 u Matches an optionally signed decimal integer, whose format is the same as
16235 <pre>
16236 expected for the subject sequence of the strtoul function with the value 10
16237 for the base argument. The corresponding argument shall be a pointer to
16238 unsigned integer.
16239 </pre>
16240 x Matches an optionally signed hexadecimal integer, whose format is the same
16241 <pre>
16242 as expected for the subject sequence of the strtoul function with the value
16243 16 for the base argument. The corresponding argument shall be a pointer to
16244 unsigned integer.
16245 </pre>
16246 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
16247 <!--page 338 -->
16248 <pre>
16249 format is the same as expected for the subject sequence of the strtod
16250 function. The corresponding argument shall be a pointer to floating.
16251 </pre>
16252 c Matches a sequence of characters of exactly the number specified by the field
16253 <pre>
16254 width (1 if no field width is present in the directive).<sup><a href="#note279"><b>279)</b></a></sup>
16255 If no l length modifier is present, the corresponding argument shall be a
16256 pointer to the initial element of a character array large enough to accept the
16257 sequence. No null character is added.
16258 If an l length modifier is present, the input shall be a sequence of multibyte
16259 characters that begins in the initial shift state. Each multibyte character in the
16260 sequence is converted to a wide character as if by a call to the mbrtowc
16261 function, with the conversion state described by an mbstate_t object
16262 initialized to zero before the first multibyte character is converted. The
16263 corresponding argument shall be a pointer to the initial element of an array of
16264 wchar_t large enough to accept the resulting sequence of wide characters.
16265 No null wide character is added.
16266 </pre>
16267 s Matches a sequence of non-white-space characters.<sup><a href="#note279"><b>279)</b></a></sup>
16268 <pre>
16269 If no l length modifier is present, the corresponding argument shall be a
16270 pointer to the initial element of a character array large enough to accept the
16271 sequence and a terminating null character, which will be added automatically.
16272 If an l length modifier is present, the input shall be a sequence of multibyte
16273 characters that begins in the initial shift state. Each multibyte character is
16274 converted to a wide character as if by a call to the mbrtowc function, with
16275 the conversion state described by an mbstate_t object initialized to zero
16276 before the first multibyte character is converted. The corresponding argument
16277 shall be a pointer to the initial element of an array of wchar_t large enough
16278 to accept the sequence and the terminating null wide character, which will be
16279 added automatically.
16280 </pre>
16281 [ Matches a nonempty sequence of characters from a set of expected characters
16282 <pre>
16284 If no l length modifier is present, the corresponding argument shall be a
16285 pointer to the initial element of a character array large enough to accept the
16286 sequence and a terminating null character, which will be added automatically.
16287 If an l length modifier is present, the input shall be a sequence of multibyte
16288 characters that begins in the initial shift state. Each multibyte character is
16289 converted to a wide character as if by a call to the mbrtowc function, with
16290 the conversion state described by an mbstate_t object initialized to zero
16291 </pre>
16293 <!--page 339 -->
16294 <pre>
16295 before the first multibyte character is converted. The corresponding argument
16296 shall be a pointer to the initial element of an array of wchar_t large enough
16297 to accept the sequence and the terminating null wide character, which will be
16298 added automatically.
16299 The conversion specifier includes all subsequent characters in the format
16300 string, up to and including the matching right bracket (]). The characters
16301 between the brackets (the scanlist) compose the scanset, unless the character
16302 after the left bracket is a circumflex (^), in which case the scanset contains all
16303 characters that do not appear in the scanlist between the circumflex and the
16304 right bracket. If the conversion specifier begins with [] or [^], the right
16305 bracket character is in the scanlist and the next following right bracket
16306 character is the matching right bracket that ends the specification; otherwise
16307 the first following right bracket character is the one that ends the
16308 specification. If a - character is in the scanlist and is not the first, nor the
16309 second where the first character is a ^, nor the last character, the behavior is
16310 implementation-defined.
16311 </pre>
16312 p Matches an implementation-defined set of sequences, which should be the
16313 <pre>
16314 same as the set of sequences that may be produced by the %p conversion of
16315 the fprintf function. The corresponding argument shall be a pointer to a
16316 pointer to void. The input item is converted to a pointer value in an
16317 implementation-defined manner. If the input item is a value converted earlier
16318 during the same program execution, the pointer that results shall compare
16319 equal to that value; otherwise the behavior of the %p conversion is undefined.
16320 </pre>
16321 n No input is consumed. The corresponding argument shall be a pointer to
16322 <pre>
16323 signed integer into which is to be written the number of characters read from
16324 the input stream so far by this call to the fscanf function. Execution of a
16325 %n directive does not increment the assignment count returned at the
16326 completion of execution of the fscanf function. No argument is converted,
16327 but one is consumed. If the conversion specification includes an assignment-
16328 suppressing character or a field width, the behavior is undefined.
16329 </pre>
16330 % Matches a single % character; no conversion or assignment occurs. The
16331 <pre>
16332 complete conversion specification shall be %%.
16333 </pre>
16334 <p><!--para 13 -->
16335 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note280"><b>280)</b></a></sup>
16336 <p><!--para 14 -->
16337 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
16338 respectively, a, e, f, g, and x.
16342 <!--page 340 -->
16343 <p><!--para 15 -->
16344 Trailing white space (including new-line characters) is left unread unless matched by a
16345 directive. The success of literal matches and suppressed assignments is not directly
16346 determinable other than via the %n directive.
16347 <p><b>Returns</b>
16348 <p><!--para 16 -->
16349 The fscanf function returns the value of the macro EOF if an input failure occurs
16350 before the first conversion (if any) has completed. Otherwise, the function returns the
16351 number of input items assigned, which can be fewer than provided for, or even zero, in
16352 the event of an early matching failure.
16353 <p><!--para 17 -->
16354 EXAMPLE 1 The call:
16355 <pre>
16357 /* ... */
16358 int n, i; float x; char name[50];
16360 </pre>
16361 with the input line:
16362 <pre>
16363 25 54.32E-1 thompson
16364 </pre>
16365 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
16366 thompson\0.
16368 <p><!--para 18 -->
16369 EXAMPLE 2 The call:
16370 <pre>
16372 /* ... */
16373 int i; float x; char name[50];
16375 </pre>
16376 with input:
16377 <pre>
16378 56789 0123 56a72
16379 </pre>
16380 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
16381 sequence 56\0. The next character read from the input stream will be a.
16383 <p><!--para 19 -->
16384 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
16385 <pre>
16387 /* ... */
16388 int count; float quant; char units[21], item[21];
16389 do {
16392 } while (!feof(stdin) && !ferror(stdin));
16393 </pre>
16394 <p><!--para 20 -->
16395 If the stdin stream contains the following lines:
16396 <!--page 341 -->
16397 <pre>
16398 2 quarts of oil
16399 -12.8degrees Celsius
16400 lots of luck
16401 10.0LBS of
16402 dirt
16403 100ergs of energy
16404 </pre>
16405 the execution of the above example will be analogous to the following assignments:
16406 <pre>
16408 count = 3;
16413 count = 3;
16415 count = EOF;
16416 </pre>
16418 <p><!--para 21 -->
16419 EXAMPLE 4 In:
16420 <pre>
16422 /* ... */
16423 int d1, d2, n1, n2, i;
16425 </pre>
16426 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
16427 of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
16429 <p><!--para 22 -->
16430 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
16431 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
16432 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
16433 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
16434 entry into the alternate shift state.
16435 <p><!--para 23 -->
16436 After the call:
16437 <pre>
16439 /* ... */
16440 char str[50];
16442 </pre>
16443 with the input line:
16444 <pre>
16445 a(uparrow) X Y(downarrow) bc
16446 </pre>
16447 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
16448 characters, in the more general case) appears to be a single-byte white-space character.
16449 <p><!--para 24 -->
16450 In contrast, after the call:
16451 <pre>
16454 /* ... */
16455 wchar_t wstr[50];
16457 </pre>
16458 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
16459 terminating null wide character.
16460 <p><!--para 25 -->
16461 However, the call:
16462 <!--page 342 -->
16463 <pre>
16466 /* ... */
16467 wchar_t wstr[50];
16469 </pre>
16470 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
16471 string.
16472 <p><!--para 26 -->
16473 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
16474 character Y, after the call:
16475 <pre>
16478 /* ... */
16479 wchar_t wstr[50];
16481 </pre>
16482 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
16483 multibyte character.
16485 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>), the
16486 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.22.1.4">7.22.1.4</a>), conversion state
16489 <p><b>Footnotes</b>
16490 <p><small><a name="note277" href="#note277">277)</a> These white-space characters are not counted against a specified field width.
16491 </small>
16492 <p><small><a name="note278" href="#note278">278)</a> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
16493 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
16494 </small>
16495 <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 [
16496 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
16497 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
16498 </small>
16499 <p><small><a name="note280" href="#note280">280)</a> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
16500 </small>
16503 <p><b>Synopsis</b>
16504 <p><!--para 1 -->
16505 <pre>
16507 int printf(const char * restrict format, ...);
16508 </pre>
16509 <p><b>Description</b>
16510 <p><!--para 2 -->
16511 The printf function is equivalent to fprintf with the argument stdout interposed
16512 before the arguments to printf.
16513 <p><b>Returns</b>
16514 <p><!--para 3 -->
16515 The printf function returns the number of characters transmitted, or a negative value if
16516 an output or encoding error occurred.
16519 <p><b>Synopsis</b>
16520 <p><!--para 1 -->
16521 <pre>
16523 int scanf(const char * restrict format, ...);
16524 </pre>
16525 <p><b>Description</b>
16526 <p><!--para 2 -->
16527 The scanf function is equivalent to fscanf with the argument stdin interposed
16528 before the arguments to scanf.
16529 <!--page 343 -->
16530 <p><b>Returns</b>
16531 <p><!--para 3 -->
16532 The scanf function returns the value of the macro EOF if an input failure occurs before
16533 the first conversion (if any) has completed. Otherwise, the scanf function returns the
16534 number of input items assigned, which can be fewer than provided for, or even zero, in
16535 the event of an early matching failure.
16538 <p><b>Synopsis</b>
16539 <p><!--para 1 -->
16540 <pre>
16542 int snprintf(char * restrict s, size_t n,
16543 const char * restrict format, ...);
16544 </pre>
16545 <p><b>Description</b>
16546 <p><!--para 2 -->
16547 The snprintf function is equivalent to fprintf, except that the output is written into
16548 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
16549 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
16550 discarded rather than being written to the array, and a null character is written at the end
16551 of the characters actually written into the array. If copying takes place between objects
16552 that overlap, the behavior is undefined.
16553 <p><b>Returns</b>
16554 <p><!--para 3 -->
16555 The snprintf function returns the number of characters that would have been written
16556 had n been sufficiently large, not counting the terminating null character, or a negative
16557 value if an encoding error occurred. Thus, the null-terminated output has been
16558 completely written if and only if the returned value is nonnegative and less than n.
16561 <p><b>Synopsis</b>
16562 <p><!--para 1 -->
16563 <pre>
16565 int sprintf(char * restrict s,
16566 const char * restrict format, ...);
16567 </pre>
16568 <p><b>Description</b>
16569 <p><!--para 2 -->
16570 The sprintf function is equivalent to fprintf, except that the output is written into
16571 an array (specified by the argument s) rather than to a stream. A null character is written
16572 at the end of the characters written; it is not counted as part of the returned value. If
16573 copying takes place between objects that overlap, the behavior is undefined.
16574 <p><b>Returns</b>
16575 <p><!--para 3 -->
16576 The sprintf function returns the number of characters written in the array, not
16577 counting the terminating null character, or a negative value if an encoding error occurred.
16578 <!--page 344 -->
16581 <p><b>Synopsis</b>
16582 <p><!--para 1 -->
16583 <pre>
16585 int sscanf(const char * restrict s,
16586 const char * restrict format, ...);
16587 </pre>
16588 <p><b>Description</b>
16589 <p><!--para 2 -->
16590 The sscanf function is equivalent to fscanf, except that input is obtained from a
16591 string (specified by the argument s) rather than from a stream. Reaching the end of the
16592 string is equivalent to encountering end-of-file for the fscanf function. If copying
16593 takes place between objects that overlap, the behavior is undefined.
16594 <p><b>Returns</b>
16595 <p><!--para 3 -->
16596 The sscanf function returns the value of the macro EOF if an input failure occurs
16597 before the first conversion (if any) has completed. Otherwise, the sscanf function
16598 returns the number of input items assigned, which can be fewer than provided for, or even
16599 zero, in the event of an early matching failure.
16602 <p><b>Synopsis</b>
16603 <p><!--para 1 -->
16604 <pre>
16607 int vfprintf(FILE * restrict stream,
16608 const char * restrict format,
16609 va_list arg);
16610 </pre>
16611 <p><b>Description</b>
16612 <p><!--para 2 -->
16613 The vfprintf function is equivalent to fprintf, with the variable argument list
16614 replaced by arg, which shall have been initialized by the va_start macro (and
16615 possibly subsequent va_arg calls). The vfprintf function does not invoke the
16617 <p><b>Returns</b>
16618 <p><!--para 3 -->
16619 The vfprintf function returns the number of characters transmitted, or a negative
16620 value if an output or encoding error occurred.
16621 <p><!--para 4 -->
16622 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
16627 <!--page 345 -->
16628 <pre>
16631 void error(char *function_name, char *format, ...)
16632 {
16633 va_list args;
16634 va_start(args, format);
16635 // print out name of function causing error
16637 // print out remainder of message
16638 vfprintf(stderr, format, args);
16639 va_end(args);
16640 }
16641 </pre>
16644 <p><b>Footnotes</b>
16645 <p><small><a name="note281" href="#note281">281)</a> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
16646 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
16647 </small>
16650 <p><b>Synopsis</b>
16651 <p><!--para 1 -->
16652 <pre>
16655 int vfscanf(FILE * restrict stream,
16656 const char * restrict format,
16657 va_list arg);
16658 </pre>
16659 <p><b>Description</b>
16660 <p><!--para 2 -->
16661 The vfscanf function is equivalent to fscanf, with the variable argument list
16662 replaced by arg, which shall have been initialized by the va_start macro (and
16663 possibly subsequent va_arg calls). The vfscanf function does not invoke the
16665 <p><b>Returns</b>
16666 <p><!--para 3 -->
16667 The vfscanf function returns the value of the macro EOF if an input failure occurs
16668 before the first conversion (if any) has completed. Otherwise, the vfscanf function
16669 returns the number of input items assigned, which can be fewer than provided for, or even
16670 zero, in the event of an early matching failure.
16673 <p><b>Synopsis</b>
16674 <p><!--para 1 -->
16675 <pre>
16678 int vprintf(const char * restrict format,
16679 va_list arg);
16680 </pre>
16681 <p><b>Description</b>
16682 <p><!--para 2 -->
16683 The vprintf function is equivalent to printf, with the variable argument list
16684 replaced by arg, which shall have been initialized by the va_start macro (and
16685 <!--page 346 -->
16686 possibly subsequent va_arg calls). The vprintf function does not invoke the
16688 <p><b>Returns</b>
16689 <p><!--para 3 -->
16690 The vprintf function returns the number of characters transmitted, or a negative value
16691 if an output or encoding error occurred.
16694 <p><b>Synopsis</b>
16695 <p><!--para 1 -->
16696 <pre>
16699 int vscanf(const char * restrict format,
16700 va_list arg);
16701 </pre>
16702 <p><b>Description</b>
16703 <p><!--para 2 -->
16704 The vscanf function is equivalent to scanf, with the variable argument list replaced
16705 by arg, which shall have been initialized by the va_start macro (and possibly
16706 subsequent va_arg calls). The vscanf function does not invoke the va_end
16708 <p><b>Returns</b>
16709 <p><!--para 3 -->
16710 The vscanf function returns the value of the macro EOF if an input failure occurs
16711 before the first conversion (if any) has completed. Otherwise, the vscanf function
16712 returns the number of input items assigned, which can be fewer than provided for, or even
16713 zero, in the event of an early matching failure.
16716 <p><b>Synopsis</b>
16717 <p><!--para 1 -->
16718 <pre>
16721 int vsnprintf(char * restrict s, size_t n,
16722 const char * restrict format,
16723 va_list arg);
16724 </pre>
16725 <p><b>Description</b>
16726 <p><!--para 2 -->
16727 The vsnprintf function is equivalent to snprintf, with the variable argument list
16728 replaced by arg, which shall have been initialized by the va_start macro (and
16729 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
16730 va_end macro.<sup><a href="#note281"><b>281)</b></a></sup> If copying takes place between objects that overlap, the behavior is
16731 undefined.
16732 <!--page 347 -->
16733 <p><b>Returns</b>
16734 <p><!--para 3 -->
16735 The vsnprintf function returns the number of characters that would have been written
16736 had n been sufficiently large, not counting the terminating null character, or a negative
16737 value if an encoding error occurred. Thus, the null-terminated output has been
16738 completely written if and only if the returned value is nonnegative and less than n.
16741 <p><b>Synopsis</b>
16742 <p><!--para 1 -->
16743 <pre>
16746 int vsprintf(char * restrict s,
16747 const char * restrict format,
16748 va_list arg);
16749 </pre>
16750 <p><b>Description</b>
16751 <p><!--para 2 -->
16752 The vsprintf function is equivalent to sprintf, with the variable argument list
16753 replaced by arg, which shall have been initialized by the va_start macro (and
16754 possibly subsequent va_arg calls). The vsprintf function does not invoke the
16755 va_end macro.<sup><a href="#note281"><b>281)</b></a></sup> If copying takes place between objects that overlap, the behavior is
16756 undefined.
16757 <p><b>Returns</b>
16758 <p><!--para 3 -->
16759 The vsprintf function returns the number of characters written in the array, not
16760 counting the terminating null character, or a negative value if an encoding error occurred.
16763 <p><b>Synopsis</b>
16764 <p><!--para 1 -->
16765 <pre>
16768 int vsscanf(const char * restrict s,
16769 const char * restrict format,
16770 va_list arg);
16771 </pre>
16772 <p><b>Description</b>
16773 <p><!--para 2 -->
16774 The vsscanf function is equivalent to sscanf, with the variable argument list
16775 replaced by arg, which shall have been initialized by the va_start macro (and
16776 possibly subsequent va_arg calls). The vsscanf function does not invoke the
16778 <p><b>Returns</b>
16779 <p><!--para 3 -->
16780 The vsscanf function returns the value of the macro EOF if an input failure occurs
16781 before the first conversion (if any) has completed. Otherwise, the vsscanf function
16782 <!--page 348 -->
16783 returns the number of input items assigned, which can be fewer than provided for, or even
16784 zero, in the event of an early matching failure.
16789 <p><b>Synopsis</b>
16790 <p><!--para 1 -->
16791 <pre>
16793 int fgetc(FILE *stream);
16794 </pre>
16795 <p><b>Description</b>
16796 <p><!--para 2 -->
16797 If the end-of-file indicator for the input stream pointed to by stream is not set and a
16798 next character is present, the fgetc function obtains that character as an unsigned
16799 char converted to an int and advances the associated file position indicator for the
16800 stream (if defined).
16801 <p><b>Returns</b>
16802 <p><!--para 3 -->
16803 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
16804 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
16805 fgetc function returns the next character from the input stream pointed to by stream.
16806 If a read error occurs, the error indicator for the stream is set and the fgetc function
16809 <p><b>Footnotes</b>
16810 <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.
16811 </small>
16814 <p><b>Synopsis</b>
16815 <p><!--para 1 -->
16816 <pre>
16818 char *fgets(char * restrict s, int n,
16819 FILE * restrict stream);
16820 </pre>
16821 <p><b>Description</b>
16822 <p><!--para 2 -->
16823 The fgets function reads at most one less than the number of characters specified by n
16824 from the stream pointed to by stream into the array pointed to by s. No additional
16825 characters are read after a new-line character (which is retained) or after end-of-file. A
16826 null character is written immediately after the last character read into the array.
16827 <p><b>Returns</b>
16828 <p><!--para 3 -->
16829 The fgets function returns s if successful. If end-of-file is encountered and no
16830 characters have been read into the array, the contents of the array remain unchanged and a
16831 null pointer is returned. If a read error occurs during the operation, the array contents are
16832 indeterminate and a null pointer is returned.
16834 <!--page 349 -->
16837 <p><b>Synopsis</b>
16838 <p><!--para 1 -->
16839 <pre>
16841 int fputc(int c, FILE *stream);
16842 </pre>
16843 <p><b>Description</b>
16844 <p><!--para 2 -->
16845 The fputc function writes the character specified by c (converted to an unsigned
16846 char) to the output stream pointed to by stream, at the position indicated by the
16847 associated file position indicator for the stream (if defined), and advances the indicator
16848 appropriately. If the file cannot support positioning requests, or if the stream was opened
16849 with append mode, the character is appended to the output stream.
16850 <p><b>Returns</b>
16851 <p><!--para 3 -->
16852 The fputc function returns the character written. If a write error occurs, the error
16853 indicator for the stream is set and fputc returns EOF.
16856 <p><b>Synopsis</b>
16857 <p><!--para 1 -->
16858 <pre>
16860 int fputs(const char * restrict s,
16861 FILE * restrict stream);
16862 </pre>
16863 <p><b>Description</b>
16864 <p><!--para 2 -->
16865 The fputs function writes the string pointed to by s to the stream pointed to by
16866 stream. The terminating null character is not written.
16867 <p><b>Returns</b>
16868 <p><!--para 3 -->
16869 The fputs function returns EOF if a write error occurs; otherwise it returns a
16870 nonnegative value.
16873 <p><b>Synopsis</b>
16874 <p><!--para 1 -->
16875 <pre>
16877 int getc(FILE *stream);
16878 </pre>
16879 <p><b>Description</b>
16880 <p><!--para 2 -->
16881 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
16882 may evaluate stream more than once, so the argument should never be an expression
16883 with side effects.
16884 <!--page 350 -->
16885 <p><b>Returns</b>
16886 <p><!--para 3 -->
16887 The getc function returns the next character from the input stream pointed to by
16888 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
16889 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
16890 getc returns EOF.
16893 <p><b>Synopsis</b>
16894 <p><!--para 1 -->
16895 <pre>
16897 int getchar(void);
16898 </pre>
16899 <p><b>Description</b>
16900 <p><!--para 2 -->
16901 The getchar function is equivalent to getc with the argument stdin.
16902 <p><b>Returns</b>
16903 <p><!--para 3 -->
16904 The getchar function returns the next character from the input stream pointed to by
16905 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
16906 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
16907 getchar returns EOF. *
16910 <p><b>Synopsis</b>
16911 <p><!--para 1 -->
16912 <pre>
16914 int putc(int c, FILE *stream);
16915 </pre>
16916 <p><b>Description</b>
16917 <p><!--para 2 -->
16918 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
16919 may evaluate stream more than once, so that argument should never be an expression
16920 with side effects.
16921 <p><b>Returns</b>
16922 <p><!--para 3 -->
16923 The putc function returns the character written. If a write error occurs, the error
16924 indicator for the stream is set and putc returns EOF.
16927 <p><b>Synopsis</b>
16928 <p><!--para 1 -->
16929 <pre>
16931 int putchar(int c);
16932 </pre>
16933 <p><b>Description</b>
16934 <p><!--para 2 -->
16935 The putchar function is equivalent to putc with the second argument stdout.
16936 <!--page 351 -->
16937 <p><b>Returns</b>
16938 <p><!--para 3 -->
16939 The putchar function returns the character written. If a write error occurs, the error
16940 indicator for the stream is set and putchar returns EOF.
16943 <p><b>Synopsis</b>
16944 <p><!--para 1 -->
16945 <pre>
16947 int puts(const char *s);
16948 </pre>
16949 <p><b>Description</b>
16950 <p><!--para 2 -->
16951 The puts function writes the string pointed to by s to the stream pointed to by stdout,
16952 and appends a new-line character to the output. The terminating null character is not
16953 written.
16954 <p><b>Returns</b>
16955 <p><!--para 3 -->
16956 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
16957 value.
16960 <p><b>Synopsis</b>
16961 <p><!--para 1 -->
16962 <pre>
16964 int ungetc(int c, FILE *stream);
16965 </pre>
16966 <p><b>Description</b>
16967 <p><!--para 2 -->
16968 The ungetc function pushes the character specified by c (converted to an unsigned
16969 char) back onto the input stream pointed to by stream. Pushed-back characters will be
16970 returned by subsequent reads on that stream in the reverse order of their pushing. A
16971 successful intervening call (with the stream pointed to by stream) to a file positioning
16972 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
16973 stream. The external storage corresponding to the stream is unchanged.
16974 <p><!--para 3 -->
16975 One character of pushback is guaranteed. If the ungetc function is called too many
16976 times on the same stream without an intervening read or file positioning operation on that
16977 stream, the operation may fail.
16978 <p><!--para 4 -->
16979 If the value of c equals that of the macro EOF, the operation fails and the input stream is
16980 unchanged.
16981 <p><!--para 5 -->
16982 A successful call to the ungetc function clears the end-of-file indicator for the stream.
16983 The value of the file position indicator for the stream after reading or discarding all
16984 pushed-back characters shall be the same as it was before the characters were pushed
16985 back. For a text stream, the value of its file position indicator after a successful call to the
16986 ungetc function is unspecified until all pushed-back characters are read or discarded.
16987 <!--page 352 -->
16988 For a binary stream, its file position indicator is decremented by each successful call to
16989 the ungetc function; if its value was zero before a call, it is indeterminate after the
16991 <p><b>Returns</b>
16992 <p><!--para 6 -->
16993 The ungetc function returns the character pushed back after conversion, or EOF if the
16994 operation fails.
16997 <p><b>Footnotes</b>
16998 <p><small><a name="note283" href="#note283">283)</a> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
16999 </small>
17004 <p><b>Synopsis</b>
17005 <p><!--para 1 -->
17006 <pre>
17008 size_t fread(void * restrict ptr,
17009 size_t size, size_t nmemb,
17010 FILE * restrict stream);
17011 </pre>
17012 <p><b>Description</b>
17013 <p><!--para 2 -->
17014 The fread function reads, into the array pointed to by ptr, up to nmemb elements
17015 whose size is specified by size, from the stream pointed to by stream. For each
17016 object, size calls are made to the fgetc function and the results stored, in the order
17017 read, in an array of unsigned char exactly overlaying the object. The file position
17018 indicator for the stream (if defined) is advanced by the number of characters successfully
17019 read. If an error occurs, the resulting value of the file position indicator for the stream is
17020 indeterminate. If a partial element is read, its value is indeterminate.
17021 <p><b>Returns</b>
17022 <p><!--para 3 -->
17023 The fread function returns the number of elements successfully read, which may be
17024 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
17025 fread returns zero and the contents of the array and the state of the stream remain
17026 unchanged.
17031 <!--page 353 -->
17034 <p><b>Synopsis</b>
17035 <p><!--para 1 -->
17036 <pre>
17038 size_t fwrite(const void * restrict ptr,
17039 size_t size, size_t nmemb,
17040 FILE * restrict stream);
17041 </pre>
17042 <p><b>Description</b>
17043 <p><!--para 2 -->
17044 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
17045 whose size is specified by size, to the stream pointed to by stream. For each object,
17046 size calls are made to the fputc function, taking the values (in order) from an array of
17047 unsigned char exactly overlaying the object. The file position indicator for the
17048 stream (if defined) is advanced by the number of characters successfully written. If an
17049 error occurs, the resulting value of the file position indicator for the stream is
17050 indeterminate.
17051 <p><b>Returns</b>
17052 <p><!--para 3 -->
17053 The fwrite function returns the number of elements successfully written, which will be
17054 less than nmemb only if a write error is encountered. If size or nmemb is zero,
17055 fwrite returns zero and the state of the stream remains unchanged.
17060 <p><b>Synopsis</b>
17061 <p><!--para 1 -->
17062 <pre>
17064 int fgetpos(FILE * restrict stream,
17065 fpos_t * restrict pos);
17066 </pre>
17067 <p><b>Description</b>
17068 <p><!--para 2 -->
17069 The fgetpos function stores the current values of the parse state (if any) and file
17070 position indicator for the stream pointed to by stream in the object pointed to by pos.
17071 The values stored contain unspecified information usable by the fsetpos function for
17072 repositioning the stream to its position at the time of the call to the fgetpos function.
17073 <p><b>Returns</b>
17074 <p><!--para 3 -->
17075 If successful, the fgetpos function returns zero; on failure, the fgetpos function
17076 returns nonzero and stores an implementation-defined positive value in errno.
17078 <!--page 354 -->
17081 <p><b>Synopsis</b>
17082 <p><!--para 1 -->
17083 <pre>
17085 int fseek(FILE *stream, long int offset, int whence);
17086 </pre>
17087 <p><b>Description</b>
17088 <p><!--para 2 -->
17089 The fseek function sets the file position indicator for the stream pointed to by stream.
17090 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
17091 <p><!--para 3 -->
17092 For a binary stream, the new position, measured in characters from the beginning of the
17093 file, is obtained by adding offset to the position specified by whence. The specified
17094 position is the beginning of the file if whence is SEEK_SET, the current value of the file
17095 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
17096 meaningfully support fseek calls with a whence value of SEEK_END.
17097 <p><!--para 4 -->
17098 For a text stream, either offset shall be zero, or offset shall be a value returned by
17099 an earlier successful call to the ftell function on a stream associated with the same file
17100 and whence shall be SEEK_SET.
17101 <p><!--para 5 -->
17102 After determining the new position, a successful call to the fseek function undoes any
17103 effects of the ungetc function on the stream, clears the end-of-file indicator for the
17104 stream, and then establishes the new position. After a successful fseek call, the next
17105 operation on an update stream may be either input or output.
17106 <p><b>Returns</b>
17107 <p><!--para 6 -->
17108 The fseek function returns nonzero only for a request that cannot be satisfied.
17112 <p><b>Synopsis</b>
17113 <p><!--para 1 -->
17114 <pre>
17116 int fsetpos(FILE *stream, const fpos_t *pos);
17117 </pre>
17118 <p><b>Description</b>
17119 <p><!--para 2 -->
17120 The fsetpos function sets the mbstate_t object (if any) and file position indicator
17121 for the stream pointed to by stream according to the value of the object pointed to by
17122 pos, which shall be a value obtained from an earlier successful call to the fgetpos
17123 function on a stream associated with the same file. If a read or write error occurs, the
17124 error indicator for the stream is set and fsetpos fails.
17125 <p><!--para 3 -->
17126 A successful call to the fsetpos function undoes any effects of the ungetc function
17127 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
17128 parse state and position. After a successful fsetpos call, the next operation on an
17129 <!--page 355 -->
17130 update stream may be either input or output.
17131 <p><b>Returns</b>
17132 <p><!--para 4 -->
17133 If successful, the fsetpos function returns zero; on failure, the fsetpos function
17134 returns nonzero and stores an implementation-defined positive value in errno.
17137 <p><b>Synopsis</b>
17138 <p><!--para 1 -->
17139 <pre>
17141 long int ftell(FILE *stream);
17142 </pre>
17143 <p><b>Description</b>
17144 <p><!--para 2 -->
17145 The ftell function obtains the current value of the file position indicator for the stream
17146 pointed to by stream. For a binary stream, the value is the number of characters from
17147 the beginning of the file. For a text stream, its file position indicator contains unspecified
17148 information, usable by the fseek function for returning the file position indicator for the
17149 stream to its position at the time of the ftell call; the difference between two such
17150 return values is not necessarily a meaningful measure of the number of characters written
17151 or read.
17152 <p><b>Returns</b>
17153 <p><!--para 3 -->
17154 If successful, the ftell function returns the current value of the file position indicator
17155 for the stream. On failure, the ftell function returns -1L and stores an
17156 implementation-defined positive value in errno.
17159 <p><b>Synopsis</b>
17160 <p><!--para 1 -->
17161 <pre>
17163 void rewind(FILE *stream);
17164 </pre>
17165 <p><b>Description</b>
17166 <p><!--para 2 -->
17167 The rewind function sets the file position indicator for the stream pointed to by
17168 stream to the beginning of the file. It is equivalent to
17169 <pre>
17170 (void)fseek(stream, 0L, SEEK_SET)
17171 </pre>
17172 except that the error indicator for the stream is also cleared.
17173 <p><b>Returns</b>
17174 <p><!--para 3 -->
17175 The rewind function returns no value.
17176 <!--page 356 -->
17181 <p><b>Synopsis</b>
17182 <p><!--para 1 -->
17183 <pre>
17185 void clearerr(FILE *stream);
17186 </pre>
17187 <p><b>Description</b>
17188 <p><!--para 2 -->
17189 The clearerr function clears the end-of-file and error indicators for the stream pointed
17190 to by stream.
17191 <p><b>Returns</b>
17192 <p><!--para 3 -->
17193 The clearerr function returns no value.
17196 <p><b>Synopsis</b>
17197 <p><!--para 1 -->
17198 <pre>
17200 int feof(FILE *stream);
17201 </pre>
17202 <p><b>Description</b>
17203 <p><!--para 2 -->
17204 The feof function tests the end-of-file indicator for the stream pointed to by stream.
17205 <p><b>Returns</b>
17206 <p><!--para 3 -->
17207 The feof function returns nonzero if and only if the end-of-file indicator is set for
17208 stream.
17211 <p><b>Synopsis</b>
17212 <p><!--para 1 -->
17213 <pre>
17215 int ferror(FILE *stream);
17216 </pre>
17217 <p><b>Description</b>
17218 <p><!--para 2 -->
17219 The ferror function tests the error indicator for the stream pointed to by stream.
17220 <p><b>Returns</b>
17221 <p><!--para 3 -->
17222 The ferror function returns nonzero if and only if the error indicator is set for
17223 stream.
17224 <!--page 357 -->
17227 <p><b>Synopsis</b>
17228 <p><!--para 1 -->
17229 <pre>
17231 void perror(const char *s);
17232 </pre>
17233 <p><b>Description</b>
17234 <p><!--para 2 -->
17235 The perror function maps the error number in the integer expression errno to an
17236 error message. It writes a sequence of characters to the standard error stream thus: first
17237 (if s is not a null pointer and the character pointed to by s is not the null character), the
17238 string pointed to by s followed by a colon (:) and a space; then an appropriate error
17239 message string followed by a new-line character. The contents of the error message
17240 strings are the same as those returned by the strerror function with argument errno.
17241 <p><b>Returns</b>
17242 <p><!--para 3 -->
17243 The perror function returns no value.
17245 <!--page 358 -->
17248 <p><!--para 1 -->
17249 The header <a href="#7.22"><stdlib.h></a> declares five types and several functions of general utility, and
17251 <p><!--para 2 -->
17253 <pre>
17254 div_t
17255 </pre>
17256 which is a structure type that is the type of the value returned by the div function,
17257 <pre>
17258 ldiv_t
17259 </pre>
17260 which is a structure type that is the type of the value returned by the ldiv function, and
17261 <pre>
17262 lldiv_t
17263 </pre>
17264 which is a structure type that is the type of the value returned by the lldiv function.
17265 <p><!--para 3 -->
17267 <pre>
17268 EXIT_FAILURE
17269 </pre>
17270 and
17271 <pre>
17272 EXIT_SUCCESS
17273 </pre>
17274 which expand to integer constant expressions that can be used as the argument to the
17275 exit function to return unsuccessful or successful termination status, respectively, to the
17276 host environment;
17277 <pre>
17278 RAND_MAX
17279 </pre>
17280 which expands to an integer constant expression that is the maximum value returned by
17281 the rand function; and
17282 <pre>
17283 MB_CUR_MAX
17284 </pre>
17285 which expands to a positive integer expression with type size_t that is the maximum
17286 number of bytes in a multibyte character for the extended character set specified by the
17287 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
17292 <!--page 359 -->
17294 <p><b>Footnotes</b>
17295 <p><small><a name="note284" href="#note284">284)</a> See ''future library directions'' (<a href="#7.30.10">7.30.10</a>).
17296 </small>
17299 <p><!--para 1 -->
17300 The functions atof, atoi, atol, and atoll need not affect the value of the integer
17301 expression errno on an error. If the value of the result cannot be represented, the
17302 behavior is undefined.
17305 <p><b>Synopsis</b>
17306 <p><!--para 1 -->
17307 <pre>
17309 double atof(const char *nptr);
17310 </pre>
17311 <p><b>Description</b>
17312 <p><!--para 2 -->
17313 The atof function converts the initial portion of the string pointed to by nptr to
17314 double representation. Except for the behavior on error, it is equivalent to
17315 <pre>
17316 strtod(nptr, (char **)NULL)
17317 </pre>
17318 <p><b>Returns</b>
17319 <p><!--para 3 -->
17320 The atof function returns the converted value.
17321 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
17324 <p><b>Synopsis</b>
17325 <p><!--para 1 -->
17326 <pre>
17328 int atoi(const char *nptr);
17329 long int atol(const char *nptr);
17330 long long int atoll(const char *nptr);
17331 </pre>
17332 <p><b>Description</b>
17333 <p><!--para 2 -->
17334 The atoi, atol, and atoll functions convert the initial portion of the string pointed
17335 to by nptr to int, long int, and long long int representation, respectively.
17336 Except for the behavior on error, they are equivalent to
17337 <pre>
17338 atoi: (int)strtol(nptr, (char **)NULL, 10)
17339 atol: strtol(nptr, (char **)NULL, 10)
17340 atoll: strtoll(nptr, (char **)NULL, 10)
17341 </pre>
17342 <p><b>Returns</b>
17343 <p><!--para 3 -->
17344 The atoi, atol, and atoll functions return the converted value.
17345 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
17347 <!--page 360 -->
17349 <h5><a name="7.22.1.3" href="#7.22.1.3">7.22.1.3 The strtod, strtof, and strtold functions</a></h5>
17350 <p><b>Synopsis</b>
17351 <p><!--para 1 -->
17352 <pre>
17354 double strtod(const char * restrict nptr,
17355 char ** restrict endptr);
17356 float strtof(const char * restrict nptr,
17357 char ** restrict endptr);
17358 long double strtold(const char * restrict nptr,
17359 char ** restrict endptr);
17360 </pre>
17361 <p><b>Description</b>
17362 <p><!--para 2 -->
17363 The strtod, strtof, and strtold functions convert the initial portion of the string
17364 pointed to by nptr to double, float, and long double representation,
17365 respectively. First, they decompose the input string into three parts: an initial, possibly
17366 empty, sequence of white-space characters (as specified by the isspace function), a
17367 subject sequence resembling a floating-point constant or representing an infinity or NaN;
17368 and a final string of one or more unrecognized characters, including the terminating null
17369 character of the input string. Then, they attempt to convert the subject sequence to a
17370 floating-point number, and return the result.
17371 <p><!--para 3 -->
17372 The expected form of the subject sequence is an optional plus or minus sign, then one of
17373 the following:
17374 <ul>
17375 <li> a nonempty sequence of decimal digits optionally containing a decimal-point
17377 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
17378 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
17379 <li> INF or INFINITY, ignoring case
17380 <li> NAN or NAN(n-char-sequence<sub>opt</sub>), ignoring case in the NAN part, where:
17381 <pre>
17382 n-char-sequence:
17383 digit
17384 nondigit
17385 n-char-sequence digit
17386 n-char-sequence nondigit
17387 </pre>
17388 </ul>
17389 The subject sequence is defined as the longest initial subsequence of the input string,
17390 starting with the first non-white-space character, that is of the expected form. The subject
17391 sequence contains no characters if the input string is not of the expected form.
17392 <p><!--para 4 -->
17393 If the subject sequence has the expected form for a floating-point number, the sequence of
17394 characters starting with the first digit or the decimal-point character (whichever occurs
17395 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
17396 <!--page 361 -->
17397 decimal-point character is used in place of a period, and that if neither an exponent part
17398 nor a decimal-point character appears in a decimal floating point number, or if a binary
17399 exponent part does not appear in a hexadecimal floating point number, an exponent part
17400 of the appropriate type with value zero is assumed to follow the last digit in the string. If
17401 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note285"><b>285)</b></a></sup>
17402 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
17403 the return type, else like a floating constant that is too large for the range of the return
17404 type. A character sequence NAN or NAN(n-char-sequence<sub>opt</sub>), is interpreted as a quiet
17405 NaN, if supported in the return type, else like a subject sequence part that does not have
17406 the expected form; the meaning of the n-char sequences is implementation-defined.<sup><a href="#note286"><b>286)</b></a></sup> A
17407 pointer to the final string is stored in the object pointed to by endptr, provided that
17408 endptr is not a null pointer.
17409 <p><!--para 5 -->
17410 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
17411 value resulting from the conversion is correctly rounded.
17412 <p><!--para 6 -->
17414 accepted.
17415 <p><!--para 7 -->
17416 If the subject sequence is empty or does not have the expected form, no conversion is
17417 performed; the value of nptr is stored in the object pointed to by endptr, provided
17418 that endptr is not a null pointer.
17419 <p><b>Recommended practice</b>
17420 <p><!--para 8 -->
17421 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
17422 the result is not exactly representable, the result should be one of the two numbers in the
17423 appropriate internal format that are adjacent to the hexadecimal floating source value,
17424 with the extra stipulation that the error should have a correct sign for the current rounding
17425 direction.
17426 <p><!--para 9 -->
17427 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
17428 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
17429 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
17430 consider the two bounding, adjacent decimal strings L and U, both having
17431 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
17432 The result should be one of the (equal or adjacent) values that would be obtained by
17433 correctly rounding L and U according to the current rounding direction, with the extra
17435 <!--page 362 -->
17436 stipulation that the error with respect to D should have a correct sign for the current
17438 <p><b>Returns</b>
17439 <p><!--para 10 -->
17440 The functions return the converted value, if any. If no conversion could be performed,
17441 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
17442 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
17443 return type and sign of the value), and the value of the macro ERANGE is stored in
17444 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
17445 no greater than the smallest normalized positive number in the return type; whether
17446 errno acquires the value ERANGE is implementation-defined.
17448 <p><b>Footnotes</b>
17449 <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
17450 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
17451 methods may yield different results if rounding is toward positive or negative infinity. In either case,
17452 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
17453 </small>
17454 <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
17455 the NaN's significand.
17456 </small>
17457 <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
17458 to the same internal floating value, but if not will round to adjacent values.
17459 </small>
17461 <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>
17462 <p><b>Synopsis</b>
17463 <p><!--para 1 -->
17464 <pre>
17466 long int strtol(
17467 const char * restrict nptr,
17468 char ** restrict endptr,
17469 int base);
17470 long long int strtoll(
17471 const char * restrict nptr,
17472 char ** restrict endptr,
17473 int base);
17474 unsigned long int strtoul(
17475 const char * restrict nptr,
17476 char ** restrict endptr,
17477 int base);
17478 unsigned long long int strtoull(
17479 const char * restrict nptr,
17480 char ** restrict endptr,
17481 int base);
17482 </pre>
17483 <p><b>Description</b>
17484 <p><!--para 2 -->
17485 The strtol, strtoll, strtoul, and strtoull functions convert the initial
17486 portion of the string pointed to by nptr to long int, long long int, unsigned
17487 long int, and unsigned long long int representation, respectively. First,
17488 they decompose the input string into three parts: an initial, possibly empty, sequence of
17489 white-space characters (as specified by the isspace function), a subject sequence
17492 <!--page 363 -->
17493 resembling an integer represented in some radix determined by the value of base, and a
17494 final string of one or more unrecognized characters, including the terminating null
17495 character of the input string. Then, they attempt to convert the subject sequence to an
17496 integer, and return the result.
17497 <p><!--para 3 -->
17498 If the value of base is zero, the expected form of the subject sequence is that of an
17499 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
17500 not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
17501 expected form of the subject sequence is a sequence of letters and digits representing an
17502 integer with the radix specified by base, optionally preceded by a plus or minus sign,
17503 but not including an integer suffix. The letters from a (or A) through z (or Z) are
17504 ascribed the values 10 through 35; only letters and digits whose ascribed values are less
17505 than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
17506 optionally precede the sequence of letters and digits, following the sign if present.
17507 <p><!--para 4 -->
17508 The subject sequence is defined as the longest initial subsequence of the input string,
17509 starting with the first non-white-space character, that is of the expected form. The subject
17510 sequence contains no characters if the input string is empty or consists entirely of white
17511 space, or if the first non-white-space character is other than a sign or a permissible letter
17512 or digit.
17513 <p><!--para 5 -->
17514 If the subject sequence has the expected form and the value of base is zero, the sequence
17515 of characters starting with the first digit is interpreted as an integer constant according to
17516 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
17517 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
17518 as given above. If the subject sequence begins with a minus sign, the value resulting from
17519 the conversion is negated (in the return type). A pointer to the final string is stored in the
17520 object pointed to by endptr, provided that endptr is not a null pointer.
17521 <p><!--para 6 -->
17523 accepted.
17524 <p><!--para 7 -->
17525 If the subject sequence is empty or does not have the expected form, no conversion is
17526 performed; the value of nptr is stored in the object pointed to by endptr, provided
17527 that endptr is not a null pointer.
17528 <p><b>Returns</b>
17529 <p><!--para 8 -->
17530 The strtol, strtoll, strtoul, and strtoull functions return the converted
17531 value, if any. If no conversion could be performed, zero is returned. If the correct value
17532 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
17533 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
17534 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
17535 <!--page 364 -->
17537 <h4><a name="7.22.2" href="#7.22.2">7.22.2 Pseudo-random sequence generation functions</a></h4>
17540 <p><b>Synopsis</b>
17541 <p><!--para 1 -->
17542 <pre>
17544 int rand(void);
17545 </pre>
17546 <p><b>Description</b>
17547 <p><!--para 2 -->
17548 The rand function computes a sequence of pseudo-random integers in the range 0 to
17550 <p><!--para 3 -->
17551 The rand function is not required to avoid data races. The implementation shall behave
17552 as if no library function calls the rand function.
17553 <p><b>Returns</b>
17554 <p><!--para 4 -->
17555 The rand function returns a pseudo-random integer.
17556 <p><b>Environmental limits</b>
17557 <p><!--para 5 -->
17558 The value of the RAND_MAX macro shall be at least 32767.
17560 <p><b>Footnotes</b>
17561 <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
17562 are known to produce sequences with distressingly non-random low-order bits. Applications with
17563 particular requirements should use a generator that is known to be sufficient for their needs.
17564 </small>
17567 <p><b>Synopsis</b>
17568 <p><!--para 1 -->
17569 <pre>
17571 void srand(unsigned int seed);
17572 </pre>
17573 <p><b>Description</b>
17574 <p><!--para 2 -->
17575 The srand function uses the argument as a seed for a new sequence of pseudo-random
17576 numbers to be returned by subsequent calls to rand. If srand is then called with the
17577 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
17578 called before any calls to srand have been made, the same sequence shall be generated
17579 as when srand is first called with a seed value of 1.
17580 <p><!--para 3 -->
17581 The implementation shall behave as if no library function calls the srand function.
17582 <p><b>Returns</b>
17583 <p><!--para 4 -->
17584 The srand function returns no value.
17589 <!--page 365 -->
17590 <p><!--para 5 -->
17591 EXAMPLE The following functions define a portable implementation of rand and srand.
17592 <pre>
17593 static unsigned long int next = 1;
17594 int rand(void) // RAND_MAX assumed to be 32767
17595 {
17596 next = next * 1103515245 + 12345;
17597 return (unsigned int)(next/65536) % 32768;
17598 }
17599 void srand(unsigned int seed)
17600 {
17601 next = seed;
17602 }
17603 </pre>
17607 <p><!--para 1 -->
17608 The order and contiguity of storage allocated by successive calls to the
17609 aligned_alloc, calloc, malloc, and realloc functions is unspecified. The
17610 pointer returned if the allocation succeeds is suitably aligned so that it may be assigned to
17611 a pointer to any type of object with a fundamental alignment requirement and then used
17612 to access such an object or an array of such objects in the space allocated (until the space
17613 is explicitly deallocated). The lifetime of an allocated object extends from the allocation
17614 until the deallocation. Each such allocation shall yield a pointer to an object disjoint from
17615 any other object. The pointer returned points to the start (lowest byte address) of the
17616 allocated space. If the space cannot be allocated, a null pointer is returned. If the size of
17617 the space requested is zero, the behavior is implementation-defined: either a null pointer
17618 is returned, or the behavior is as if the size were some nonzero value, except that the
17619 returned pointer shall not be used to access an object.
17622 <p><b>Synopsis</b>
17623 <p><!--para 1 -->
17624 <pre>
17626 void *aligned_alloc(size_t alignment, size_t size);
17627 </pre>
17628 <p><b>Description</b>
17629 <p><!--para 2 -->
17630 The aligned_alloc function allocates space for an object whose alignment is
17631 specified by alignment, whose size is specified by size, and whose value is
17632 indeterminate. The value of alignment shall be a valid alignment supported by the
17633 implementation and the value of size shall be an integral multiple of alignment.
17634 <p><b>Returns</b>
17635 <p><!--para 3 -->
17636 The aligned_alloc function returns either a null pointer or a pointer to the allocated
17637 space.
17638 <!--page 366 -->
17641 <p><b>Synopsis</b>
17642 <p><!--para 1 -->
17643 <pre>
17645 void *calloc(size_t nmemb, size_t size);
17646 </pre>
17647 <p><b>Description</b>
17648 <p><!--para 2 -->
17649 The calloc function allocates space for an array of nmemb objects, each of whose size
17650 is size. The space is initialized to all bits zero.<sup><a href="#note289"><b>289)</b></a></sup>
17651 <p><b>Returns</b>
17652 <p><!--para 3 -->
17653 The calloc function returns either a null pointer or a pointer to the allocated space.
17655 <p><b>Footnotes</b>
17656 <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
17657 constant.
17658 </small>
17661 <p><b>Synopsis</b>
17662 <p><!--para 1 -->
17663 <pre>
17665 void free(void *ptr);
17666 </pre>
17667 <p><b>Description</b>
17668 <p><!--para 2 -->
17669 The free function causes the space pointed to by ptr to be deallocated, that is, made
17670 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
17671 the argument does not match a pointer earlier returned by a memory management
17672 function, or if the space has been deallocated by a call to free or realloc, the
17673 behavior is undefined.
17674 <p><b>Returns</b>
17675 <p><!--para 3 -->
17676 The free function returns no value.
17679 <p><b>Synopsis</b>
17680 <p><!--para 1 -->
17681 <pre>
17683 void *malloc(size_t size);
17684 </pre>
17685 <p><b>Description</b>
17686 <p><!--para 2 -->
17687 The malloc function allocates space for an object whose size is specified by size and
17688 whose value is indeterminate.
17693 <!--page 367 -->
17694 <p><b>Returns</b>
17695 <p><!--para 3 -->
17696 The malloc function returns either a null pointer or a pointer to the allocated space.
17699 <p><b>Synopsis</b>
17700 <p><!--para 1 -->
17701 <pre>
17703 void *realloc(void *ptr, size_t size);
17704 </pre>
17705 <p><b>Description</b>
17706 <p><!--para 2 -->
17707 The realloc function deallocates the old object pointed to by ptr and returns a
17708 pointer to a new object that has the size specified by size. The contents of the new
17709 object shall be the same as that of the old object prior to deallocation, up to the lesser of
17710 the new and old sizes. Any bytes in the new object beyond the size of the old object have
17711 indeterminate values.
17712 <p><!--para 3 -->
17713 If ptr is a null pointer, the realloc function behaves like the malloc function for the
17714 specified size. Otherwise, if ptr does not match a pointer earlier returned by a memory
17715 management function, or if the space has been deallocated by a call to the free or
17716 realloc function, the behavior is undefined. If memory for the new object cannot be
17717 allocated, the old object is not deallocated and its value is unchanged.
17718 <p><b>Returns</b>
17719 <p><!--para 4 -->
17720 The realloc function returns a pointer to the new object (which may have the same
17721 value as a pointer to the old object), or a null pointer if the new object could not be
17722 allocated.
17727 <p><b>Synopsis</b>
17728 <p><!--para 1 -->
17729 <pre>
17731 _Noreturn void abort(void);
17732 </pre>
17733 <p><b>Description</b>
17734 <p><!--para 2 -->
17735 The abort function causes abnormal program termination to occur, unless the signal
17736 SIGABRT is being caught and the signal handler does not return. Whether open streams
17737 with unwritten buffered data are flushed, open streams are closed, or temporary files are
17738 removed is implementation-defined. An implementation-defined form of the status
17739 unsuccessful termination is returned to the host environment by means of the function
17740 call raise(SIGABRT).
17741 <!--page 368 -->
17742 <p><b>Returns</b>
17743 <p><!--para 3 -->
17744 The abort function does not return to its caller.
17747 <p><b>Synopsis</b>
17748 <p><!--para 1 -->
17749 <pre>
17751 int atexit(void (*func)(void));
17752 </pre>
17753 <p><b>Description</b>
17754 <p><!--para 2 -->
17755 The atexit function registers the function pointed to by func, to be called without
17757 <p><b>Environmental limits</b>
17758 <p><!--para 3 -->
17759 The implementation shall support the registration of at least 32 functions.
17760 <p><b>Returns</b>
17761 <p><!--para 4 -->
17762 The atexit function returns zero if the registration succeeds, nonzero if it fails.
17763 <p><b> Forward references</b>: the at_quick_exit function (<a href="#7.22.4.3">7.22.4.3</a>), the exit function
17766 <p><b>Footnotes</b>
17767 <p><small><a name="note290" href="#note290">290)</a> The atexit function registrations are distinct from the at_quick_exit registrations, so
17768 applications may need to call both registration functions with the same argument.
17769 </small>
17772 <p><b>Synopsis</b>
17773 <p><!--para 1 -->
17774 <pre>
17776 int at_quick_exit(void (*func)(void));
17777 </pre>
17778 <p><b>Description</b>
17779 <p><!--para 2 -->
17780 The at_quick_exit function registers the function pointed to by func, to be called
17782 <p><b>Environmental limits</b>
17783 <p><!--para 3 -->
17784 The implementation shall support the registration of at least 32 functions.
17785 <p><b>Returns</b>
17786 <p><!--para 4 -->
17787 The at_quick_exit function returns zero if the registration succeeds, nonzero if it
17788 fails.
17792 <!--page 369 -->
17794 <p><b>Footnotes</b>
17795 <p><small><a name="note291" href="#note291">291)</a> The at_quick_exit function registrations are distinct from the atexit registrations, so
17796 applications may need to call both registration functions with the same argument.
17797 </small>
17800 <p><b>Synopsis</b>
17801 <p><!--para 1 -->
17802 <pre>
17804 _Noreturn void exit(int status);
17805 </pre>
17806 <p><b>Description</b>
17807 <p><!--para 2 -->
17808 The exit function causes normal program termination to occur. No functions registered
17809 by the at_quick_exit function are called. If a program calls the exit function
17810 more than once, or calls the quick_exit function in addition to the exit function, the
17811 behavior is undefined.
17812 <p><!--para 3 -->
17813 First, all functions registered by the atexit function are called, in the reverse order of
17814 their registration,<sup><a href="#note292"><b>292)</b></a></sup> except that a function is called after any previously registered
17815 functions that had already been called at the time it was registered. If, during the call to
17816 any such function, a call to the longjmp function is made that would terminate the call
17817 to the registered function, the behavior is undefined.
17818 <p><!--para 4 -->
17819 Next, all open streams with unwritten buffered data are flushed, all open streams are
17820 closed, and all files created by the tmpfile function are removed.
17821 <p><!--para 5 -->
17822 Finally, control is returned to the host environment. If the value of status is zero or
17823 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
17824 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
17825 of the status unsuccessful termination is returned. Otherwise the status returned is
17826 implementation-defined.
17827 <p><b>Returns</b>
17828 <p><!--para 6 -->
17829 The exit function cannot return to its caller.
17831 <p><b>Footnotes</b>
17832 <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
17833 other registered functions.
17834 </small>
17837 <p><b>Synopsis</b>
17838 <p><!--para 1 -->
17839 <pre>
17841 _Noreturn void _Exit(int status);
17842 </pre>
17843 <p><b>Description</b>
17844 <p><!--para 2 -->
17845 The _Exit function causes normal program termination to occur and control to be
17846 returned to the host environment. No functions registered by the atexit function, the
17847 at_quick_exit function, or signal handlers registered by the signal function are
17848 called. The status returned to the host environment is determined in the same way as for
17851 <!--page 370 -->
17852 the exit function (<a href="#7.22.4.4">7.22.4.4</a>). Whether open streams with unwritten buffered data are
17853 flushed, open streams are closed, or temporary files are removed is implementation-
17854 defined.
17855 <p><b>Returns</b>
17856 <p><!--para 3 -->
17857 The _Exit function cannot return to its caller.
17860 <p><b>Synopsis</b>
17861 <p><!--para 1 -->
17862 <pre>
17864 char *getenv(const char *name);
17865 </pre>
17866 <p><b>Description</b>
17867 <p><!--para 2 -->
17868 The getenv function searches an environment list, provided by the host environment,
17869 for a string that matches the string pointed to by name. The set of environment names
17870 and the method for altering the environment list are implementation-defined. The
17871 getenv function need not avoid data races with other threads of execution that modify
17873 <p><!--para 3 -->
17874 The implementation shall behave as if no library function calls the getenv function.
17875 <p><b>Returns</b>
17876 <p><!--para 4 -->
17877 The getenv function returns a pointer to a string associated with the matched list
17878 member. The string pointed to shall not be modified by the program, but may be
17879 overwritten by a subsequent call to the getenv function. If the specified name cannot
17880 be found, a null pointer is returned.
17882 <p><b>Footnotes</b>
17883 <p><small><a name="note293" href="#note293">293)</a> Many implementations provide non-standard functions that modify the environment list.
17884 </small>
17887 <p><b>Synopsis</b>
17888 <p><!--para 1 -->
17889 <pre>
17891 _Noreturn void quick_exit(int status);
17892 </pre>
17893 <p><b>Description</b>
17894 <p><!--para 2 -->
17895 The quick_exit function causes normal program termination to occur. No functions
17896 registered by the atexit function or signal handlers registered by the signal function
17897 are called. If a program calls the quick_exit function more than once, or calls the
17898 exit function in addition to the quick_exit function, the behavior is undefined.
17899 <p><!--para 3 -->
17900 The quick_exit function first calls all functions registered by the at_quick_exit
17901 function, in the reverse order of their registration,<sup><a href="#note294"><b>294)</b></a></sup> except that a function is called after
17904 <!--page 371 -->
17905 any previously registered functions that had already been called at the time it was
17906 registered. If, during the call to any such function, a call to the longjmp function is
17907 made that would terminate the call to the registered function, the behavior is undefined.
17908 <p><!--para 4 -->
17909 Then control is returned to the host environment by means of the function call
17910 _Exit(status).
17911 <p><b>Returns</b>
17912 <p><!--para 5 -->
17913 The quick_exit function cannot return to its caller.
17915 <p><b>Footnotes</b>
17916 <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
17917 other registered functions.
17918 </small>
17921 <p><b>Synopsis</b>
17922 <p><!--para 1 -->
17923 <pre>
17925 int system(const char *string);
17926 </pre>
17927 <p><b>Description</b>
17928 <p><!--para 2 -->
17929 If string is a null pointer, the system function determines whether the host
17930 environment has a command processor. If string is not a null pointer, the system
17931 function passes the string pointed to by string to that command processor to be
17932 executed in a manner which the implementation shall document; this might then cause the
17933 program calling system to behave in a non-conforming manner or to terminate.
17934 <p><b>Returns</b>
17935 <p><!--para 3 -->
17936 If the argument is a null pointer, the system function returns nonzero only if a
17937 command processor is available. If the argument is not a null pointer, and the system
17938 function does return, it returns an implementation-defined value.
17941 <p><!--para 1 -->
17942 These utilities make use of a comparison function to search or sort arrays of unspecified
17943 type. Where an argument declared as size_t nmemb specifies the length of the array
17944 for a function, nmemb can have the value zero on a call to that function; the comparison
17945 function is not called, a search finds no matching element, and sorting performs no
17946 rearrangement. Pointer arguments on such a call shall still have valid values, as described
17948 <p><!--para 2 -->
17949 The implementation shall ensure that the second argument of the comparison function
17950 (when called from bsearch), or both arguments (when called from qsort), are
17951 pointers to elements of the array.<sup><a href="#note295"><b>295)</b></a></sup> The first argument when called from bsearch
17952 shall equal key.
17956 <!--page 372 -->
17957 <p><!--para 3 -->
17958 The comparison function shall not alter the contents of the array. The implementation
17959 may reorder elements of the array between calls to the comparison function, but shall not
17960 alter the contents of any individual element.
17961 <p><!--para 4 -->
17962 When the same objects (consisting of size bytes, irrespective of their current positions
17963 in the array) are passed more than once to the comparison function, the results shall be
17964 consistent with one another. That is, for qsort they shall define a total ordering on the
17965 array, and for bsearch the same object shall always compare the same way with the
17966 key.
17967 <p><!--para 5 -->
17968 A sequence point occurs immediately before and immediately after each call to the
17969 comparison function, and also between any call to the comparison function and any
17970 movement of the objects passed as arguments to that call.
17972 <p><b>Footnotes</b>
17973 <p><small><a name="note295" href="#note295">295)</a> That is, if the value passed is p, then the following expressions are always nonzero:
17975 <pre>
17976 ((char *)p - (char *)base) % size == 0
17977 (char *)p >= (char *)base
17978 (char *)p < (char *)base + nmemb * size
17979 </pre>
17981 </small>
17984 <p><b>Synopsis</b>
17985 <p><!--para 1 -->
17986 <pre>
17988 void *bsearch(const void *key, const void *base,
17989 size_t nmemb, size_t size,
17990 int (*compar)(const void *, const void *));
17991 </pre>
17992 <p><b>Description</b>
17993 <p><!--para 2 -->
17994 The bsearch function searches an array of nmemb objects, the initial element of which
17995 is pointed to by base, for an element that matches the object pointed to by key. The
17996 size of each element of the array is specified by size.
17997 <p><!--para 3 -->
17998 The comparison function pointed to by compar is called with two arguments that point
17999 to the key object and to an array element, in that order. The function shall return an
18000 integer less than, equal to, or greater than zero if the key object is considered,
18001 respectively, to be less than, to match, or to be greater than the array element. The array
18002 shall consist of: all the elements that compare less than, all the elements that compare
18003 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>
18004 <p><b>Returns</b>
18005 <p><!--para 4 -->
18006 The bsearch function returns a pointer to a matching element of the array, or a null
18007 pointer if no match is found. If two elements compare as equal, which element is
18010 <!--page 373 -->
18011 matched is unspecified.
18013 <p><b>Footnotes</b>
18014 <p><small><a name="note296" href="#note296">296)</a> In practice, the entire array is sorted according to the comparison function.
18015 </small>
18018 <p><b>Synopsis</b>
18019 <p><!--para 1 -->
18020 <pre>
18022 void qsort(void *base, size_t nmemb, size_t size,
18023 int (*compar)(const void *, const void *));
18024 </pre>
18025 <p><b>Description</b>
18026 <p><!--para 2 -->
18027 The qsort function sorts an array of nmemb objects, the initial element of which is
18028 pointed to by base. The size of each object is specified by size.
18029 <p><!--para 3 -->
18030 The contents of the array are sorted into ascending order according to a comparison
18031 function pointed to by compar, which is called with two arguments that point to the
18032 objects being compared. The function shall return an integer less than, equal to, or
18033 greater than zero if the first argument is considered to be respectively less than, equal to,
18034 or greater than the second.
18035 <p><!--para 4 -->
18036 If two elements compare as equal, their order in the resulting sorted array is unspecified.
18037 <p><b>Returns</b>
18038 <p><!--para 5 -->
18039 The qsort function returns no value.
18044 <p><b>Synopsis</b>
18045 <p><!--para 1 -->
18046 <pre>
18048 int abs(int j);
18049 long int labs(long int j);
18050 long long int llabs(long long int j);
18051 </pre>
18052 <p><b>Description</b>
18053 <p><!--para 2 -->
18054 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
18055 result cannot be represented, the behavior is undefined.<sup><a href="#note297"><b>297)</b></a></sup>
18056 <p><b>Returns</b>
18057 <p><!--para 3 -->
18058 The abs, labs, and llabs, functions return the absolute value.
18063 <!--page 374 -->
18065 <p><b>Footnotes</b>
18066 <p><small><a name="note297" href="#note297">297)</a> The absolute value of the most negative number cannot be represented in two's complement.
18067 </small>
18070 <p><b>Synopsis</b>
18071 <p><!--para 1 -->
18072 <pre>
18074 div_t div(int numer, int denom);
18075 ldiv_t ldiv(long int numer, long int denom);
18076 lldiv_t lldiv(long long int numer, long long int denom);
18077 </pre>
18078 <p><b>Description</b>
18079 <p><!--para 2 -->
18080 The div, ldiv, and lldiv, functions compute numer / denom and numer %
18081 denom in a single operation.
18082 <p><b>Returns</b>
18083 <p><!--para 3 -->
18084 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
18085 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
18086 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
18087 each of which has the same type as the arguments numer and denom. If either part of
18088 the result cannot be represented, the behavior is undefined.
18090 <h4><a name="7.22.7" href="#7.22.7">7.22.7 Multibyte/wide character conversion functions</a></h4>
18091 <p><!--para 1 -->
18092 The behavior of the multibyte character functions is affected by the LC_CTYPE category
18093 of the current locale. For a state-dependent encoding, each function is placed into its
18094 initial conversion state at program startup and can be returned to that state by a call for
18095 which its character pointer argument, s, is a null pointer. Subsequent calls with s as
18096 other than a null pointer cause the internal conversion state of the function to be altered as
18097 necessary. A call with s as a null pointer causes these functions to return a nonzero value
18098 if encodings have state dependency, and zero otherwise.<sup><a href="#note298"><b>298)</b></a></sup> Changing the LC_CTYPE
18099 category causes the conversion state of these functions to be indeterminate.
18101 <p><b>Footnotes</b>
18102 <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
18103 character codes, but are grouped with an adjacent multibyte character.
18104 </small>
18107 <p><b>Synopsis</b>
18108 <p><!--para 1 -->
18109 <pre>
18111 int mblen(const char *s, size_t n);
18112 </pre>
18113 <p><b>Description</b>
18114 <p><!--para 2 -->
18115 If s is not a null pointer, the mblen function determines the number of bytes contained
18116 in the multibyte character pointed to by s. Except that the conversion state of the
18117 mbtowc function is not affected, it is equivalent to
18121 <!--page 375 -->
18122 <pre>
18123 mbtowc((wchar_t *)0, (const char *)0, 0);
18124 mbtowc((wchar_t *)0, s, n);
18125 </pre>
18126 <p><!--para 3 -->
18127 The implementation shall behave as if no library function calls the mblen function.
18128 <p><b>Returns</b>
18129 <p><!--para 4 -->
18130 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
18131 character encodings, respectively, do or do not have state-dependent encodings. If s is
18132 not a null pointer, the mblen function either returns 0 (if s points to the null character),
18133 or returns the number of bytes that are contained in the multibyte character (if the next n
18134 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
18135 multibyte character).
18139 <p><b>Synopsis</b>
18140 <p><!--para 1 -->
18141 <pre>
18143 int mbtowc(wchar_t * restrict pwc,
18144 const char * restrict s,
18145 size_t n);
18146 </pre>
18147 <p><b>Description</b>
18148 <p><!--para 2 -->
18149 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
18150 the byte pointed to by s to determine the number of bytes needed to complete the next
18151 multibyte character (including any shift sequences). If the function determines that the
18152 next multibyte character is complete and valid, it determines the value of the
18153 corresponding wide character and then, if pwc is not a null pointer, stores that value in
18154 the object pointed to by pwc. If the corresponding wide character is the null wide
18155 character, the function is left in the initial conversion state.
18156 <p><!--para 3 -->
18157 The implementation shall behave as if no library function calls the mbtowc function.
18158 <p><b>Returns</b>
18159 <p><!--para 4 -->
18160 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
18161 character encodings, respectively, do or do not have state-dependent encodings. If s is
18162 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
18163 or returns the number of bytes that are contained in the converted multibyte character (if
18164 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
18165 form a valid multibyte character).
18166 <p><!--para 5 -->
18167 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
18168 macro.
18169 <!--page 376 -->
18172 <p><b>Synopsis</b>
18173 <p><!--para 1 -->
18174 <pre>
18176 int wctomb(char *s, wchar_t wc);
18177 </pre>
18178 <p><b>Description</b>
18179 <p><!--para 2 -->
18180 The wctomb function determines the number of bytes needed to represent the multibyte
18181 character corresponding to the wide character given by wc (including any shift
18182 sequences), and stores the multibyte character representation in the array whose first
18183 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
18184 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
18185 sequence needed to restore the initial shift state, and the function is left in the initial
18186 conversion state.
18187 <p><!--para 3 -->
18188 The implementation shall behave as if no library function calls the wctomb function.
18189 <p><b>Returns</b>
18190 <p><!--para 4 -->
18191 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
18192 character encodings, respectively, do or do not have state-dependent encodings. If s is
18193 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
18194 to a valid multibyte character, or returns the number of bytes that are contained in the
18195 multibyte character corresponding to the value of wc.
18196 <p><!--para 5 -->
18197 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
18199 <h4><a name="7.22.8" href="#7.22.8">7.22.8 Multibyte/wide string conversion functions</a></h4>
18200 <p><!--para 1 -->
18201 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
18202 the current locale.
18205 <p><b>Synopsis</b>
18206 <p><!--para 1 -->
18207 <pre>
18209 size_t mbstowcs(wchar_t * restrict pwcs,
18210 const char * restrict s,
18211 size_t n);
18212 </pre>
18213 <p><b>Description</b>
18214 <p><!--para 2 -->
18215 The mbstowcs function converts a sequence of multibyte characters that begins in the
18216 initial shift state from the array pointed to by s into a sequence of corresponding wide
18217 characters and stores not more than n wide characters into the array pointed to by pwcs.
18218 No multibyte characters that follow a null character (which is converted into a null wide
18219 character) will be examined or converted. Each multibyte character is converted as if by
18220 a call to the mbtowc function, except that the conversion state of the mbtowc function is
18221 <!--page 377 -->
18222 not affected.
18223 <p><!--para 3 -->
18224 No more than n elements will be modified in the array pointed to by pwcs. If copying
18225 takes place between objects that overlap, the behavior is undefined.
18226 <p><b>Returns</b>
18227 <p><!--para 4 -->
18228 If an invalid multibyte character is encountered, the mbstowcs function returns
18229 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
18230 elements modified, not including a terminating null wide character, if any.<sup><a href="#note299"><b>299)</b></a></sup>
18232 <p><b>Footnotes</b>
18233 <p><small><a name="note299" href="#note299">299)</a> The array will not be null-terminated if the value returned is n.
18234 </small>
18237 <p><b>Synopsis</b>
18238 <p><!--para 1 -->
18239 <pre>
18241 size_t wcstombs(char * restrict s,
18242 const wchar_t * restrict pwcs,
18243 size_t n);
18244 </pre>
18245 <p><b>Description</b>
18246 <p><!--para 2 -->
18247 The wcstombs function converts a sequence of wide characters from the array pointed
18248 to by pwcs into a sequence of corresponding multibyte characters that begins in the
18249 initial shift state, and stores these multibyte characters into the array pointed to by s,
18250 stopping if a multibyte character would exceed the limit of n total bytes or if a null
18251 character is stored. Each wide character is converted as if by a call to the wctomb
18252 function, except that the conversion state of the wctomb function is not affected.
18253 <p><!--para 3 -->
18254 No more than n bytes will be modified in the array pointed to by s. If copying takes place
18255 between objects that overlap, the behavior is undefined.
18256 <p><b>Returns</b>
18257 <p><!--para 4 -->
18258 If a wide character is encountered that does not correspond to a valid multibyte character,
18259 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
18260 returns the number of bytes modified, not including a terminating null character, if
18266 <!--page 378 -->
18271 <p><!--para 1 -->
18272 The header <a href="#7.23"><string.h></a> declares one type and several functions, and defines one
18273 macro useful for manipulating arrays of character type and other objects treated as arrays
18274 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
18275 <a href="#7.19">7.19</a>). Various methods are used for determining the lengths of the arrays, but in all cases
18276 a char * or void * argument points to the initial (lowest addressed) character of the
18277 array. If an array is accessed beyond the end of an object, the behavior is undefined.
18278 <p><!--para 2 -->
18279 Where an argument declared as size_t n specifies the length of the array for a
18280 function, n can have the value zero on a call to that function. Unless explicitly stated
18281 otherwise in the description of a particular function in this subclause, pointer arguments
18282 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
18283 function that locates a character finds no occurrence, a function that compares two
18284 character sequences returns zero, and a function that copies characters copies zero
18285 characters.
18286 <p><!--para 3 -->
18287 For all functions in this subclause, each character shall be interpreted as if it had the type
18288 unsigned char (and therefore every possible object representation is valid and has a
18289 different value).
18291 <p><b>Footnotes</b>
18292 <p><small><a name="note300" href="#note300">300)</a> See ''future library directions'' (<a href="#7.30.11">7.30.11</a>).
18293 </small>
18298 <p><b>Synopsis</b>
18299 <p><!--para 1 -->
18300 <pre>
18302 void *memcpy(void * restrict s1,
18303 const void * restrict s2,
18304 size_t n);
18305 </pre>
18306 <p><b>Description</b>
18307 <p><!--para 2 -->
18308 The memcpy function copies n characters from the object pointed to by s2 into the
18309 object pointed to by s1. If copying takes place between objects that overlap, the behavior
18310 is undefined.
18311 <p><b>Returns</b>
18312 <p><!--para 3 -->
18313 The memcpy function returns the value of s1.
18318 <!--page 379 -->
18321 <p><b>Synopsis</b>
18322 <p><!--para 1 -->
18323 <pre>
18325 void *memmove(void *s1, const void *s2, size_t n);
18326 </pre>
18327 <p><b>Description</b>
18328 <p><!--para 2 -->
18329 The memmove function copies n characters from the object pointed to by s2 into the
18330 object pointed to by s1. Copying takes place as if the n characters from the object
18331 pointed to by s2 are first copied into a temporary array of n characters that does not
18332 overlap the objects pointed to by s1 and s2, and then the n characters from the
18333 temporary array are copied into the object pointed to by s1.
18334 <p><b>Returns</b>
18335 <p><!--para 3 -->
18336 The memmove function returns the value of s1.
18339 <p><b>Synopsis</b>
18340 <p><!--para 1 -->
18341 <pre>
18343 char *strcpy(char * restrict s1,
18344 const char * restrict s2);
18345 </pre>
18346 <p><b>Description</b>
18347 <p><!--para 2 -->
18348 The strcpy function copies the string pointed to by s2 (including the terminating null
18349 character) into the array pointed to by s1. If copying takes place between objects that
18350 overlap, the behavior is undefined.
18351 <p><b>Returns</b>
18352 <p><!--para 3 -->
18353 The strcpy function returns the value of s1.
18356 <p><b>Synopsis</b>
18357 <p><!--para 1 -->
18358 <pre>
18360 char *strncpy(char * restrict s1,
18361 const char * restrict s2,
18362 size_t n);
18363 </pre>
18364 <p><b>Description</b>
18365 <p><!--para 2 -->
18366 The strncpy function copies not more than n characters (characters that follow a null
18367 character are not copied) from the array pointed to by s2 to the array pointed to by
18368 <!--page 380 -->
18369 s1.<sup><a href="#note301"><b>301)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
18370 <p><!--para 3 -->
18371 If the array pointed to by s2 is a string that is shorter than n characters, null characters
18372 are appended to the copy in the array pointed to by s1, until n characters in all have been
18373 written.
18374 <p><b>Returns</b>
18375 <p><!--para 4 -->
18376 The strncpy function returns the value of s1.
18378 <p><b>Footnotes</b>
18379 <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
18380 not be null-terminated.
18381 </small>
18386 <p><b>Synopsis</b>
18387 <p><!--para 1 -->
18388 <pre>
18390 char *strcat(char * restrict s1,
18391 const char * restrict s2);
18392 </pre>
18393 <p><b>Description</b>
18394 <p><!--para 2 -->
18395 The strcat function appends a copy of the string pointed to by s2 (including the
18396 terminating null character) to the end of the string pointed to by s1. The initial character
18397 of s2 overwrites the null character at the end of s1. If copying takes place between
18398 objects that overlap, the behavior is undefined.
18399 <p><b>Returns</b>
18400 <p><!--para 3 -->
18401 The strcat function returns the value of s1.
18404 <p><b>Synopsis</b>
18405 <p><!--para 1 -->
18406 <pre>
18408 char *strncat(char * restrict s1,
18409 const char * restrict s2,
18410 size_t n);
18411 </pre>
18412 <p><b>Description</b>
18413 <p><!--para 2 -->
18414 The strncat function appends not more than n characters (a null character and
18415 characters that follow it are not appended) from the array pointed to by s2 to the end of
18416 the string pointed to by s1. The initial character of s2 overwrites the null character at the
18417 end of s1. A terminating null character is always appended to the result.<sup><a href="#note302"><b>302)</b></a></sup> If copying
18419 <!--page 381 -->
18420 takes place between objects that overlap, the behavior is undefined.
18421 <p><b>Returns</b>
18422 <p><!--para 3 -->
18423 The strncat function returns the value of s1.
18426 <p><b>Footnotes</b>
18427 <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
18428 strlen(s1)+n+1.
18429 </small>
18432 <p><!--para 1 -->
18433 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
18434 and strncmp is determined by the sign of the difference between the values of the first
18435 pair of characters (both interpreted as unsigned char) that differ in the objects being
18436 compared.
18439 <p><b>Synopsis</b>
18440 <p><!--para 1 -->
18441 <pre>
18443 int memcmp(const void *s1, const void *s2, size_t n);
18444 </pre>
18445 <p><b>Description</b>
18446 <p><!--para 2 -->
18447 The memcmp function compares the first n characters of the object pointed to by s1 to
18448 the first n characters of the object pointed to by s2.<sup><a href="#note303"><b>303)</b></a></sup>
18449 <p><b>Returns</b>
18450 <p><!--para 3 -->
18451 The memcmp function returns an integer greater than, equal to, or less than zero,
18452 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
18453 pointed to by s2.
18455 <p><b>Footnotes</b>
18456 <p><small><a name="note303" href="#note303">303)</a> The contents of ''holes'' used as padding for purposes of alignment within structure objects are
18457 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
18458 comparison.
18459 </small>
18462 <p><b>Synopsis</b>
18463 <p><!--para 1 -->
18464 <pre>
18466 int strcmp(const char *s1, const char *s2);
18467 </pre>
18468 <p><b>Description</b>
18469 <p><!--para 2 -->
18470 The strcmp function compares the string pointed to by s1 to the string pointed to by
18471 s2.
18472 <p><b>Returns</b>
18473 <p><!--para 3 -->
18474 The strcmp function returns an integer greater than, equal to, or less than zero,
18475 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
18477 <!--page 382 -->
18478 pointed to by s2.
18481 <p><b>Synopsis</b>
18482 <p><!--para 1 -->
18483 <pre>
18485 int strcoll(const char *s1, const char *s2);
18486 </pre>
18487 <p><b>Description</b>
18488 <p><!--para 2 -->
18489 The strcoll function compares the string pointed to by s1 to the string pointed to by
18490 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
18491 <p><b>Returns</b>
18492 <p><!--para 3 -->
18493 The strcoll function returns an integer greater than, equal to, or less than zero,
18494 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
18495 pointed to by s2 when both are interpreted as appropriate to the current locale.
18498 <p><b>Synopsis</b>
18499 <p><!--para 1 -->
18500 <pre>
18502 int strncmp(const char *s1, const char *s2, size_t n);
18503 </pre>
18504 <p><b>Description</b>
18505 <p><!--para 2 -->
18506 The strncmp function compares not more than n characters (characters that follow a
18507 null character are not compared) from the array pointed to by s1 to the array pointed to
18508 by s2.
18509 <p><b>Returns</b>
18510 <p><!--para 3 -->
18511 The strncmp function returns an integer greater than, equal to, or less than zero,
18512 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
18513 to, or less than the possibly null-terminated array pointed to by s2.
18516 <p><b>Synopsis</b>
18517 <p><!--para 1 -->
18518 <pre>
18520 size_t strxfrm(char * restrict s1,
18521 const char * restrict s2,
18522 size_t n);
18523 </pre>
18524 <p><b>Description</b>
18525 <p><!--para 2 -->
18526 The strxfrm function transforms the string pointed to by s2 and places the resulting
18527 string into the array pointed to by s1. The transformation is such that if the strcmp
18528 function is applied to two transformed strings, it returns a value greater than, equal to, or
18529 <!--page 383 -->
18530 less than zero, corresponding to the result of the strcoll function applied to the same
18531 two original strings. No more than n characters are placed into the resulting array
18532 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
18533 be a null pointer. If copying takes place between objects that overlap, the behavior is
18534 undefined.
18535 <p><b>Returns</b>
18536 <p><!--para 3 -->
18537 The strxfrm function returns the length of the transformed string (not including the
18538 terminating null character). If the value returned is n or more, the contents of the array
18539 pointed to by s1 are indeterminate.
18540 <p><!--para 4 -->
18541 EXAMPLE The value of the following expression is the size of the array needed to hold the
18542 transformation of the string pointed to by s.
18543 <pre>
18544 1 + strxfrm(NULL, s, 0)
18545 </pre>
18551 <p><b>Synopsis</b>
18552 <p><!--para 1 -->
18553 <pre>
18555 void *memchr(const void *s, int c, size_t n);
18556 </pre>
18557 <p><b>Description</b>
18558 <p><!--para 2 -->
18559 The memchr function locates the first occurrence of c (converted to an unsigned
18560 char) in the initial n characters (each interpreted as unsigned char) of the object
18561 pointed to by s. The implementation shall behave as if it reads the characters sequentially
18562 and stops as soon as a matching character is found.
18563 <p><b>Returns</b>
18564 <p><!--para 3 -->
18565 The memchr function returns a pointer to the located character, or a null pointer if the
18566 character does not occur in the object.
18569 <p><b>Synopsis</b>
18570 <p><!--para 1 -->
18571 <pre>
18573 char *strchr(const char *s, int c);
18574 </pre>
18575 <p><b>Description</b>
18576 <p><!--para 2 -->
18577 The strchr function locates the first occurrence of c (converted to a char) in the
18578 string pointed to by s. The terminating null character is considered to be part of the
18579 string.
18580 <!--page 384 -->
18581 <p><b>Returns</b>
18582 <p><!--para 3 -->
18583 The strchr function returns a pointer to the located character, or a null pointer if the
18584 character does not occur in the string.
18587 <p><b>Synopsis</b>
18588 <p><!--para 1 -->
18589 <pre>
18591 size_t strcspn(const char *s1, const char *s2);
18592 </pre>
18593 <p><b>Description</b>
18594 <p><!--para 2 -->
18595 The strcspn function computes the length of the maximum initial segment of the string
18596 pointed to by s1 which consists entirely of characters not from the string pointed to by
18597 s2.
18598 <p><b>Returns</b>
18599 <p><!--para 3 -->
18600 The strcspn function returns the length of the segment.
18603 <p><b>Synopsis</b>
18604 <p><!--para 1 -->
18605 <pre>
18607 char *strpbrk(const char *s1, const char *s2);
18608 </pre>
18609 <p><b>Description</b>
18610 <p><!--para 2 -->
18611 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
18612 character from the string pointed to by s2.
18613 <p><b>Returns</b>
18614 <p><!--para 3 -->
18615 The strpbrk function returns a pointer to the character, or a null pointer if no character
18616 from s2 occurs in s1.
18619 <p><b>Synopsis</b>
18620 <p><!--para 1 -->
18621 <pre>
18623 char *strrchr(const char *s, int c);
18624 </pre>
18625 <p><b>Description</b>
18626 <p><!--para 2 -->
18627 The strrchr function locates the last occurrence of c (converted to a char) in the
18628 string pointed to by s. The terminating null character is considered to be part of the
18629 string.
18630 <!--page 385 -->
18631 <p><b>Returns</b>
18632 <p><!--para 3 -->
18633 The strrchr function returns a pointer to the character, or a null pointer if c does not
18634 occur in the string.
18637 <p><b>Synopsis</b>
18638 <p><!--para 1 -->
18639 <pre>
18641 size_t strspn(const char *s1, const char *s2);
18642 </pre>
18643 <p><b>Description</b>
18644 <p><!--para 2 -->
18645 The strspn function computes the length of the maximum initial segment of the string
18646 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
18647 <p><b>Returns</b>
18648 <p><!--para 3 -->
18649 The strspn function returns the length of the segment.
18652 <p><b>Synopsis</b>
18653 <p><!--para 1 -->
18654 <pre>
18656 char *strstr(const char *s1, const char *s2);
18657 </pre>
18658 <p><b>Description</b>
18659 <p><!--para 2 -->
18660 The strstr function locates the first occurrence in the string pointed to by s1 of the
18661 sequence of characters (excluding the terminating null character) in the string pointed to
18662 by s2.
18663 <p><b>Returns</b>
18664 <p><!--para 3 -->
18665 The strstr function returns a pointer to the located string, or a null pointer if the string
18666 is not found. If s2 points to a string with zero length, the function returns s1.
18669 <p><b>Synopsis</b>
18670 <p><!--para 1 -->
18671 <pre>
18673 char *strtok(char * restrict s1,
18674 const char * restrict s2);
18675 </pre>
18676 <p><b>Description</b>
18677 <p><!--para 2 -->
18678 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
18679 sequence of tokens, each of which is delimited by a character from the string pointed to
18680 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
18681 sequence have a null first argument. The separator string pointed to by s2 may be
18682 different from call to call.
18683 <!--page 386 -->
18684 <p><!--para 3 -->
18685 The first call in the sequence searches the string pointed to by s1 for the first character
18686 that is not contained in the current separator string pointed to by s2. If no such character
18687 is found, then there are no tokens in the string pointed to by s1 and the strtok function
18688 returns a null pointer. If such a character is found, it is the start of the first token.
18689 <p><!--para 4 -->
18690 The strtok function then searches from there for a character that is contained in the
18691 current separator string. If no such character is found, the current token extends to the
18692 end of the string pointed to by s1, and subsequent searches for a token will return a null
18693 pointer. If such a character is found, it is overwritten by a null character, which
18694 terminates the current token. The strtok function saves a pointer to the following
18695 character, from which the next search for a token will start.
18696 <p><!--para 5 -->
18697 Each subsequent call, with a null pointer as the value of the first argument, starts
18698 searching from the saved pointer and behaves as described above.
18699 <p><!--para 6 -->
18700 The strtok function is not required to avoid data races. The implementation shall
18701 behave as if no library function calls the strtok function.
18702 <p><b>Returns</b>
18703 <p><!--para 7 -->
18704 The strtok function returns a pointer to the first character of a token, or a null pointer
18705 if there is no token.
18706 <p><!--para 8 -->
18707 EXAMPLE
18708 <pre>
18711 char *t;
18716 </pre>
18722 <p><b>Synopsis</b>
18723 <p><!--para 1 -->
18724 <pre>
18726 void *memset(void *s, int c, size_t n);
18727 </pre>
18728 <p><b>Description</b>
18729 <p><!--para 2 -->
18730 The memset function copies the value of c (converted to an unsigned char) into
18731 each of the first n characters of the object pointed to by s.
18732 <p><b>Returns</b>
18733 <p><!--para 3 -->
18734 The memset function returns the value of s.
18735 <!--page 387 -->
18738 <p><b>Synopsis</b>
18739 <p><!--para 1 -->
18740 <pre>
18742 char *strerror(int errnum);
18743 </pre>
18744 <p><b>Description</b>
18745 <p><!--para 2 -->
18746 The strerror function maps the number in errnum to a message string. Typically,
18747 the values for errnum come from errno, but strerror shall map any value of type
18748 int to a message.
18749 <p><!--para 3 -->
18750 The strerror function is not required to avoid data races. The implementation shall
18751 behave as if no library function calls the strerror function.
18752 <p><b>Returns</b>
18753 <p><!--para 4 -->
18754 The strerror function returns a pointer to the string, the contents of which are locale-
18755 specific. The array pointed to shall not be modified by the program, but may be
18756 overwritten by a subsequent call to the strerror function.
18759 <p><b>Synopsis</b>
18760 <p><!--para 1 -->
18761 <pre>
18763 size_t strlen(const char *s);
18764 </pre>
18765 <p><b>Description</b>
18766 <p><!--para 2 -->
18767 The strlen function computes the length of the string pointed to by s.
18768 <p><b>Returns</b>
18769 <p><!--para 3 -->
18770 The strlen function returns the number of characters that precede the terminating null
18771 character.
18772 <!--page 388 -->
18775 <p><!--para 1 -->
18776 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
18777 defines several type-generic macros.
18778 <p><!--para 2 -->
18779 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
18780 double) suffix, several have one or more parameters whose corresponding real type is
18781 double. For each such function, except modf, there is a corresponding type-generic
18782 macro.<sup><a href="#note304"><b>304)</b></a></sup> The parameters whose corresponding real type is double in the function
18783 synopsis are generic parameters. Use of the macro invokes a function whose
18784 corresponding real type and type domain are determined by the arguments for the generic
18786 <p><!--para 3 -->
18787 Use of the macro invokes a function whose generic parameters have the corresponding
18788 real type determined as follows:
18789 <ul>
18790 <li> First, if any argument for generic parameters has type long double, the type
18791 determined is long double.
18792 <li> Otherwise, if any argument for generic parameters has type double or is of integer
18793 type, the type determined is double.
18794 <li> Otherwise, the type determined is float.
18795 </ul>
18796 <p><!--para 4 -->
18797 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
18798 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
18799 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
18800 corresponding type-generic macro for fabs and cabs is fabs.
18805 <!--page 389 -->
18806 <pre>
18808 function function macro
18809 acos cacos acos
18810 asin casin asin
18811 atan catan atan
18812 acosh cacosh acosh
18813 asinh casinh asinh
18814 atanh catanh atanh
18815 cos ccos cos
18816 sin csin sin
18817 tan ctan tan
18818 cosh ccosh cosh
18819 sinh csinh sinh
18820 tanh ctanh tanh
18821 exp cexp exp
18822 log clog log
18823 pow cpow pow
18824 sqrt csqrt sqrt
18825 fabs cabs fabs
18826 </pre>
18827 If at least one argument for a generic parameter is complex, then use of the macro invokes
18828 a complex function; otherwise, use of the macro invokes a real function.
18829 <p><!--para 5 -->
18830 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
18831 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
18832 name as the function. These type-generic macros are:
18833 <pre>
18834 atan2 fma llround remainder
18835 cbrt fmax log10 remquo
18836 ceil fmin log1p rint
18837 copysign fmod log2 round
18838 erf frexp logb scalbn
18839 erfc hypot lrint scalbln
18840 exp2 ilogb lround tgamma
18841 expm1 ldexp nearbyint trunc
18842 fdim lgamma nextafter
18843 floor llrint nexttoward
18844 </pre>
18845 If all arguments for generic parameters are real, then use of the macro invokes a real
18846 function; otherwise, use of the macro results in undefined behavior.
18847 <!--page 390 -->
18848 <p><!--para 6 -->
18849 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
18850 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
18851 function. These type-generic macros are:
18852 <pre>
18853 carg conj creal
18854 cimag cproj
18855 </pre>
18856 Use of the macro with any real or complex argument invokes a complex function.
18857 <p><!--para 7 -->
18858 EXAMPLE With the declarations
18859 <pre>
18861 int n;
18862 float f;
18863 double d;
18864 long double ld;
18865 float complex fc;
18866 double complex dc;
18867 long double complex ldc;
18868 </pre>
18869 functions invoked by use of type-generic macros are shown in the following table:
18870 <!--page 391 -->
18871 <pre>
18872 macro use invokes
18873 exp(n) exp(n), the function
18874 acosh(f) acoshf(f)
18875 sin(d) sin(d), the function
18876 atan(ld) atanl(ld)
18877 log(fc) clogf(fc)
18878 sqrt(dc) csqrt(dc)
18879 pow(ldc, f) cpowl(ldc, f)
18880 remainder(n, n) remainder(n, n), the function
18881 nextafter(d, f) nextafter(d, f), the function
18882 nexttoward(f, ld) nexttowardf(f, ld)
18883 copysign(n, ld) copysignl(n, ld)
18884 ceil(fc) undefined behavior
18885 rint(dc) undefined behavior
18886 fmax(ldc, ld) undefined behavior
18887 carg(n) carg(n), the function
18888 cproj(f) cprojf(f)
18889 creal(d) creal(d), the function
18890 cimag(ld) cimagl(ld)
18891 fabs(fc) cabsf(fc)
18892 carg(dc) carg(dc), the function
18893 cproj(ldc) cprojl(ldc)
18894 </pre>
18896 <p><b>Footnotes</b>
18897 <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
18898 make available the corresponding ordinary function.
18899 </small>
18900 <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,
18901 the behavior is undefined.
18902 </small>
18907 <p><!--para 1 -->
18908 The header <a href="#7.25"><threads.h></a> defines macros, and declares types, enumeration constants,
18909 and functions that support multiple threads of execution.
18910 <p><!--para 2 -->
18911 Implementations that define the macro __STDC_NO_THREADS__ need not provide
18912 this header nor support any of its facilities.
18913 <p><!--para 3 -->
18914 The macros are
18915 <pre>
18916 ONCE_FLAG_INIT
18917 </pre>
18918 which expands to a value that can be used to initialize an object of type once_flag;
18919 and
18920 <pre>
18921 TSS_DTOR_ITERATIONS
18922 </pre>
18923 which expands to an integer constant expression representing the maximum number of
18924 times that destructors will be called when a thread terminates.
18925 <p><!--para 4 -->
18926 The types are
18927 <pre>
18928 cnd_t
18929 </pre>
18930 which is a complete object type that holds an identifier for a condition variable;
18931 <pre>
18932 thrd_t
18933 </pre>
18934 which is a complete object type that holds an identifier for a thread;
18935 <pre>
18936 tss_t
18937 </pre>
18938 which is a complete object type that holds an identifier for a thread-specific storage
18939 pointer;
18940 <pre>
18941 mtx_t
18942 </pre>
18943 which is a complete object type that holds an identifier for a mutex;
18944 <pre>
18945 tss_dtor_t
18946 </pre>
18947 which is the function pointer type void (*)(void*), used for a destructor for a
18948 thread-specific storage pointer;
18949 <pre>
18950 thrd_start_t
18951 </pre>
18952 which is the function pointer type int (*)(void*) that is passed to thrd_create
18953 to create a new thread;
18954 <pre>
18955 once_flag
18956 </pre>
18957 which is a complete object type that holds a flag for use by call_once; and
18958 <!--page 392 -->
18959 <pre>
18960 xtime
18961 </pre>
18962 which is a structure type that holds a time specified in seconds and nanoseconds. The
18963 structure shall contain at least the following members, in any order.
18964 <pre>
18965 time_t sec;
18966 long nsec;
18967 </pre>
18968 <p><!--para 5 -->
18969 The enumeration constants are
18970 <pre>
18971 mtx_plain
18972 </pre>
18973 which is passed to mtx_init to create a mutex object that supports neither timeout nor
18974 test and return;
18975 <pre>
18976 mtx_recursive
18977 </pre>
18978 which is passed to mtx_init to create a mutex object that supports recursive locking;
18979 <pre>
18980 mtx_timed
18981 </pre>
18982 which is passed to mtx_init to create a mutex object that supports timeout;
18983 <pre>
18984 mtx_try
18985 </pre>
18986 which is passed to mtx_init to create a mutex object that supports test and return;
18987 <pre>
18988 thrd_timeout
18989 </pre>
18990 which is returned by a timed wait function to indicate that the time specified in the call
18991 was reached without acquiring the requested resource;
18992 <pre>
18993 thrd_success
18994 </pre>
18995 which is returned by a function to indicate that the requested operation succeeded;
18996 <pre>
18997 thrd_busy
18998 </pre>
18999 which is returned by a function to indicate that the requested operation failed because a
19000 resource requested by a test and return function is already in use;
19001 <pre>
19002 thrd_error
19003 </pre>
19004 which is returned by a function to indicate that the requested operation failed; and
19005 <pre>
19006 thrd_nomem
19007 </pre>
19008 which is returned by a function to indicate that the requested operation failed because it
19009 was unable to allocate memory.
19010 <!--page 393 -->
19015 <p><b>Synopsis</b>
19016 <p><!--para 1 -->
19017 <pre>
19019 void call_once(once_flag *flag, void (*func)(void));
19020 </pre>
19021 <p><b>Description</b>
19022 <p><!--para 2 -->
19023 The call_once function uses the once_flag pointed to by flag to ensure that
19024 func is called exactly once, the first time the call_once function is called with that
19025 value of flag. Completion of an effective call to the call_once function synchronizes
19026 with all subsequent calls to the call_once function with the same value of flag.
19027 <p><b>Returns</b>
19028 <p><!--para 3 -->
19029 The call_once function returns no value.
19034 <p><b>Synopsis</b>
19035 <p><!--para 1 -->
19036 <pre>
19038 int cnd_broadcast(cnd_t *cond);
19039 </pre>
19040 <p><b>Description</b>
19041 <p><!--para 2 -->
19042 The cnd_broadcast function unblocks all of the threads that are blocked on the
19043 condition variable pointed to by cond at the time of the call. If no threads are blocked
19044 on the condition variable pointed to by cond at the time of the call, the function does
19045 nothing.
19046 <p><b>Returns</b>
19047 <p><!--para 3 -->
19048 The cnd_broadcast function returns thrd_success on success, or thrd_error
19049 if the request could not be honored.
19052 <p><b>Synopsis</b>
19053 <p><!--para 1 -->
19054 <pre>
19056 void cnd_destroy(cnd_t *cond);
19057 </pre>
19058 <p><b>Description</b>
19059 <p><!--para 2 -->
19060 The cnd_destroy function releases all resources used by the condition variable
19061 pointed to by cond. The cnd_destroy function requires that no threads be blocked
19062 waiting for the condition variable pointed to by cond.
19063 <!--page 394 -->
19064 <p><b>Returns</b>
19065 <p><!--para 3 -->
19066 The cnd_destroy function returns no value.
19069 <p><b>Synopsis</b>
19070 <p><!--para 1 -->
19071 <pre>
19073 int cnd_init(cnd_t *cond);
19074 </pre>
19075 <p><b>Description</b>
19076 <p><!--para 2 -->
19077 The cnd_init function creates a condition variable. If it succeeds it sets the variable
19078 pointed to by cond to a value that uniquely identifies the newly created condition
19079 variable. A thread that calls cnd_wait on a newly created condition variable will
19080 block.
19081 <p><b>Returns</b>
19082 <p><!--para 3 -->
19083 The cnd_init function returns thrd_success on success, or thrd_nomem if no
19084 memory could be allocated for the newly created condition, or thrd_error if the
19085 request could not be honored.
19088 <p><b>Synopsis</b>
19089 <p><!--para 1 -->
19090 <pre>
19092 int cnd_signal(cnd_t *cond);
19093 </pre>
19094 <p><b>Description</b>
19095 <p><!--para 2 -->
19096 The cnd_signal function unblocks one of the threads that are blocked on the
19097 condition variable pointed to by cond at the time of the call. If no threads are blocked
19098 on the condition variable at the time of the call, the function does nothing and return
19099 success.
19100 <p><b>Returns</b>
19101 <p><!--para 3 -->
19102 The cnd_signal function returns thrd_success on success or thrd_error if
19103 the request could not be honored.
19106 <p><b>Synopsis</b>
19107 <p><!--para 1 -->
19108 <!--page 395 -->
19109 <pre>
19111 int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
19112 const xtime *xt);
19113 </pre>
19114 <p><b>Description</b>
19115 <p><!--para 2 -->
19116 The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and
19117 endeavors to block until the condition variable pointed to by cond is signaled by a call to
19118 cnd_signal or to cnd_broadcast, or until after the time specified by the xtime
19119 object pointed to by xt. When the calling thread becomes unblocked it locks the variable
19120 pointed to by mtx before it returns. The cnd_timedwait function requires that the
19121 mutex pointed to by mtx be locked by the calling thread.
19122 <p><b>Returns</b>
19123 <p><!--para 3 -->
19124 The cnd_timedwait function returns thrd_success upon success, or
19125 thrd_timeout if the time specified in the call was reached without acquiring the
19126 requested resource, or thrd_error if the request could not be honored.
19129 <p><b>Synopsis</b>
19130 <p><!--para 1 -->
19131 <pre>
19133 int cnd_wait(cnd_t *cond, mtx_t *mtx);
19134 </pre>
19135 <p><b>Description</b>
19136 <p><!--para 2 -->
19137 The cnd_wait function atomically unlocks the mutex pointed to by mtx and endeavors
19138 to block until the condition variable pointed to by cond is signaled by a call to
19139 cnd_signal or to cnd_broadcast. When the calling thread becomes unblocked it
19140 locks the mutex pointed to by mtx before it returns. If the mutex pointed to by mtx is
19141 not locked by the calling thread, the cnd_wait function will act as if the abort
19142 function is called.
19143 <p><b>Returns</b>
19144 <p><!--para 3 -->
19145 The cnd_wait function returns thrd_success on success or thrd_error if the
19146 request could not be honored.
19151 <p><b>Synopsis</b>
19152 <p><!--para 1 -->
19153 <pre>
19155 void mtx_destroy(mtx_t *mtx);
19156 </pre>
19157 <p><b>Description</b>
19158 <p><!--para 2 -->
19159 The mtx_destroy function releases any resources used by the mutex pointed to by
19160 mtx. No threads can be blocked waiting for the mutex pointed to by mtx.
19161 <!--page 396 -->
19162 <p><b>Returns</b>
19163 <p><!--para 3 -->
19164 The mtx_destroy function returns no value.
19167 <p><b>Synopsis</b>
19168 <p><!--para 1 -->
19169 <pre>
19171 int mtx_init(mtx_t *mtx, int type);
19172 </pre>
19173 <p><b>Description</b>
19174 <p><!--para 2 -->
19175 The mtx_init function creates a mutex object with properties indicated by type,
19176 which must have one of the six values:
19177 mtx_plain for a simple non-recursive mutex,
19178 mtx_timed for a non-recursive mutex that supports timeout,
19179 mtx_try for a non-recursive mutex that supports test and return,
19180 mtx_plain | mtx_recursive for a simple recursive mutex,
19181 mtx_timed | mtx_recursive for a recursive mutex that supports timeout, or
19182 mtx_try | mtx_recursive for a recursive mutex that supports test and return.
19183 <p><!--para 3 -->
19184 If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that
19185 uniquely identifies the newly created mutex.
19186 <p><b>Returns</b>
19187 <p><!--para 4 -->
19188 The mtx_init function returns thrd_success on success, or thrd_error if the
19189 request could not be honored.
19192 <p><b>Synopsis</b>
19193 <p><!--para 1 -->
19194 <pre>
19196 int mtx_lock(mtx_t *mtx);
19197 </pre>
19198 <p><b>Description</b>
19199 <p><!--para 2 -->
19200 The mtx_lock function blocks until it locks the mutex pointed to by mtx. If the mutex
19201 is non-recursive, it shall not be locked by the calling thread. Prior calls to mtx_unlock
19202 on the same mutex shall synchronize with this operation.
19203 <p><b>Returns</b>
19204 <p><!--para 3 -->
19205 The mtx_lock function returns thrd_success on success, or thrd_busy if the
19206 resource requested is already in use, or thrd_error if the request could not be
19207 honored.
19208 <!--page 397 -->
19211 <p><b>Synopsis</b>
19212 <p><!--para 1 -->
19213 <pre>
19215 int mtx_timedlock(mtx_t *mtx, const xtime *xt);
19216 </pre>
19217 <p><b>Description</b>
19218 <p><!--para 2 -->
19219 The mtx_timedlock function endeavors to block until it locks the mutex pointed to by
19220 mtx or until the time specified by the xtime object xt has passed. The specified mutex
19221 shall support timeout. If the operation succeeds, prior calls to mtx_unlock on the same
19222 mutex shall synchronize with this operation.
19223 <p><b>Returns</b>
19224 <p><!--para 3 -->
19225 The mtx_timedlock function returns thrd_success on success, or thrd_busy
19226 if the resource requested is already in use, or thrd_timeout if the time specified was
19227 reached without acquiring the requested resource, or thrd_error if the request could
19228 not be honored.
19231 <p><b>Synopsis</b>
19232 <p><!--para 1 -->
19233 <pre>
19235 int mtx_trylock(mtx_t *mtx);
19236 </pre>
19237 <p><b>Description</b>
19238 <p><!--para 2 -->
19239 The mtx_trylock function endeavors to lock the mutex pointed to by mtx. The
19240 specified mutex shall support either test and return or timeout. If the mutex is already
19241 locked, the function returns without blocking. If the operation succeeds, prior calls to
19242 mtx_unlock on the same mutex shall synchronize with this operation.
19243 <p><b>Returns</b>
19244 <p><!--para 3 -->
19245 The mtx_trylock function returns thrd_success on success, or thrd_busy if
19246 the resource requested is already in use, or thrd_error if the request could not be
19247 honored.
19250 <p><b>Synopsis</b>
19251 <p><!--para 1 -->
19252 <pre>
19254 int mtx_unlock(mtx_t *mtx);
19255 </pre>
19256 <p><b>Description</b>
19257 <p><!--para 2 -->
19258 The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to
19259 by mtx shall be locked by the calling thread.
19260 <!--page 398 -->
19261 <p><b>Returns</b>
19262 <p><!--para 3 -->
19263 The mtx_unlock function returns thrd_success on success or thrd_error if
19264 the request could not be honored.
19269 <p><b>Synopsis</b>
19270 <p><!--para 1 -->
19271 <pre>
19273 int thrd_create(thrd_t *thr, thrd_start_t func,
19274 void *arg);
19275 </pre>
19276 <p><b>Description</b>
19277 <p><!--para 2 -->
19278 The thrd_create function creates a new thread executing func(arg). If the
19279 thrd_create function succeeds, it sets the object pointed to by thr to the identifier of
19280 the newly created thread. (A thread's identifier may be reused for a different thread once
19281 the original thread has exited and either been detached or joined to another thread.) The
19282 completion of the thrd_create function synchronizes with the beginning of the
19283 execution of the new thread.
19284 <p><b>Returns</b>
19285 <p><!--para 3 -->
19286 The thrd_create function returns thrd_success on success, or thrd_nomem if
19287 no memory could be allocated for the thread requested, or thrd_error if the request
19288 could not be honored.
19291 <p><b>Synopsis</b>
19292 <p><!--para 1 -->
19293 <pre>
19295 thrd_t thrd_current(void);
19296 </pre>
19297 <p><b>Description</b>
19298 <p><!--para 2 -->
19299 The thrd_current function identifies the thread that called it.
19300 <p><b>Returns</b>
19301 <p><!--para 3 -->
19302 The thrd_current function returns the identifier of the thread that called it.
19305 <p><b>Synopsis</b>
19306 <p><!--para 1 -->
19307 <!--page 399 -->
19308 <pre>
19310 int thrd_detach(thrd_t thr);
19311 </pre>
19312 <p><b>Description</b>
19313 <p><!--para 2 -->
19314 The thrd_detach function tells the operating system to dispose of any resources
19315 allocated to the thread identified by thr when that thread terminates. The thread
19316 identified by thr shall not have been previously detached or joined with another thread.
19317 <p><b>Returns</b>
19318 <p><!--para 3 -->
19319 The thrd_detach function returns thrd_success on success or thrd_error if
19320 the request could not be honored.
19323 <p><b>Synopsis</b>
19324 <p><!--para 1 -->
19325 <pre>
19327 int thrd_equal(thrd_t thr0, thrd_t thr1);
19328 </pre>
19329 <p><b>Description</b>
19330 <p><!--para 2 -->
19331 The thrd_equal function will determine whether the thread identified by thr0 refers
19332 to the thread identified by thr1.
19333 <p><b>Returns</b>
19334 <p><!--para 3 -->
19335 The thrd_equal function returns zero if the thread thr0 and the thread thr1 refer to
19336 different threads. Otherwise the thrd_equal function returns a nonzero value.
19339 <p><b>Synopsis</b>
19340 <p><!--para 1 -->
19341 <pre>
19343 void thrd_exit(int res);
19344 </pre>
19345 <p><b>Description</b>
19346 <p><!--para 2 -->
19347 The thrd_exit function terminates execution of the calling thread and sets its result
19348 code to res.
19349 <p><b>Returns</b>
19350 <p><!--para 3 -->
19351 The thrd_exit function returns no value.
19354 <p><b>Synopsis</b>
19355 <p><!--para 1 -->
19356 <pre>
19358 int thrd_join(thrd_t thr, int *res);
19359 </pre>
19360 <p><b>Description</b>
19361 <p><!--para 2 -->
19362 The thrd_join function joins the thread identified by thr with the current thread by
19363 blocking until the other thread has terminated. If the parameter res is not a null pointer,
19364 <!--page 400 -->
19365 it stores the thread's result code in the integer pointed to by res. The termination of the
19366 other thread synchronizes with the completion of the thrd_join function. The thread
19367 identified by thr shall not have been previously detached or joined with another thread.
19368 <p><b>Returns</b>
19369 <p><!--para 3 -->
19370 The thrd_join function returns thrd_success on success or thrd_error if the
19371 request could not be honored.
19374 <p><b>Synopsis</b>
19375 <p><!--para 1 -->
19376 <pre>
19378 void thrd_sleep(const xtime *xt);
19379 </pre>
19380 <p><b>Description</b>
19381 <p><!--para 2 -->
19382 The thrd_sleep function suspends execution of the calling thread until after the time
19383 specified by the xtime object pointed to by xt.
19384 <p><b>Returns</b>
19385 <p><!--para 3 -->
19386 The thrd_sleep function returns no value.
19389 <p><b>Synopsis</b>
19390 <p><!--para 1 -->
19391 <pre>
19393 void thrd_yield(void);
19394 </pre>
19395 <p><b>Description</b>
19396 <p><!--para 2 -->
19397 The thrd_yield function endeavors to permit other threads to run, even if the current
19398 thread would ordinarily continue to run.
19399 <p><b>Returns</b>
19400 <p><!--para 3 -->
19401 The thrd_yield function returns no value.
19406 <p><b>Synopsis</b>
19407 <p><!--para 1 -->
19408 <pre>
19410 int tss_create(tss_t *key, tss_dtor_t dtor);
19411 </pre>
19412 <p><b>Description</b>
19413 <p><!--para 2 -->
19414 The tss_create function creates a thread-specific storage pointer with destructor
19415 dtor, which may be null.
19416 <!--page 401 -->
19417 <p><b>Returns</b>
19418 <p><!--para 3 -->
19419 If the tss_create function is successful, it sets the thread-specific storage pointed to
19420 by key to a value that uniquely identifies the newly created pointer and returns
19421 thrd_success; otherwise, thrd_error is returned and the thread-specific storage
19422 pointed to by key is set to an undefined value.
19425 <p><b>Synopsis</b>
19426 <p><!--para 1 -->
19427 <pre>
19429 void tss_delete(tss_t key);
19430 </pre>
19431 <p><b>Description</b>
19432 <p><!--para 2 -->
19433 The tss_delete function releases any resources used by the thread-specific storage
19434 identified by key.
19435 <p><b>Returns</b>
19436 <p><!--para 3 -->
19437 The tss_delete function returns no value.
19440 <p><b>Synopsis</b>
19441 <p><!--para 1 -->
19442 <pre>
19444 void *tss_get(tss_t key);
19445 </pre>
19446 <p><b>Description</b>
19447 <p><!--para 2 -->
19448 The tss_get function returns the value for the current thread held in the thread-specific
19449 storage identified by key.
19450 <p><b>Returns</b>
19451 <p><!--para 3 -->
19452 The tss_get function returns the value for the current thread if successful, or zero if
19453 unsuccessful.
19456 <p><b>Synopsis</b>
19457 <p><!--para 1 -->
19458 <pre>
19460 int tss_set(tss_t key, void *val);
19461 </pre>
19462 <p><b>Description</b>
19463 <p><!--para 2 -->
19464 The tss_set function sets the value for the current thread held in the thread-specific
19465 storage identified by key to val.
19466 <!--page 402 -->
19467 <p><b>Returns</b>
19468 <p><!--para 3 -->
19469 The tss_set function returns thrd_success on success or thrd_error if the
19470 request could not be honored.
19475 <p><b>Synopsis</b>
19476 <p><!--para 1 -->
19477 <pre>
19479 int xtime_get(xtime *xt, int base);
19480 </pre>
19481 <p><b>Description</b>
19482 <p><!--para 2 -->
19483 The xtime_get function sets the xtime object pointed to by xt to hold the current
19484 time based on the time base base.
19485 <p><b>Returns</b>
19486 <p><!--para 3 -->
19487 If the xtime_get function is successful it returns the nonzero value base, which must
19493 <!--page 403 -->
19495 <p><b>Footnotes</b>
19496 <p><small><a name="note306" href="#note306">306)</a> Although an xtime object describes times with nanosecond resolution, the actual resolution in an
19497 xtime object is system dependent.
19498 </small>
19503 <p><!--para 1 -->
19504 The header <a href="#7.26"><time.h></a> defines two macros, and declares several types and functions for
19505 manipulating time. Many functions deal with a calendar time that represents the current
19506 date (according to the Gregorian calendar) and time. Some functions deal with local
19507 time, which is the calendar time expressed for some specific time zone, and with Daylight
19508 Saving Time, which is a temporary change in the algorithm for determining local time.
19509 The local time zone and Daylight Saving Time are implementation-defined.
19510 <p><!--para 2 -->
19512 <pre>
19513 CLOCKS_PER_SEC
19514 </pre>
19515 which expands to an expression with type clock_t (described below) that is the
19516 number per second of the value returned by the clock function.
19517 <p><!--para 3 -->
19519 <pre>
19520 clock_t
19521 </pre>
19522 and
19523 <pre>
19524 time_t
19525 </pre>
19526 which are arithmetic types capable of representing times; and
19527 <pre>
19528 struct tm
19529 </pre>
19530 which holds the components of a calendar time, called the broken-down time.
19531 <p><!--para 4 -->
19532 The range and precision of times representable in clock_t and time_t are
19533 implementation-defined. The tm structure shall contain at least the following members,
19534 in any order. The semantics of the members and their normal ranges are expressed in the
19536 <pre>
19537 int tm_sec; // seconds after the minute -- [0, 60]
19538 int tm_min; // minutes after the hour -- [0, 59]
19539 int tm_hour; // hours since midnight -- [0, 23]
19540 int tm_mday; // day of the month -- [1, 31]
19541 int tm_mon; // months since January -- [0, 11]
19542 int tm_year; // years since 1900
19543 int tm_wday; // days since Sunday -- [0, 6]
19544 int tm_yday; // days since January 1 -- [0, 365]
19545 int tm_isdst; // Daylight Saving Time flag
19546 </pre>
19550 <!--page 404 -->
19551 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
19552 Saving Time is not in effect, and negative if the information is not available.
19554 <p><b>Footnotes</b>
19555 <p><small><a name="note307" href="#note307">307)</a> The range [0, 60] for tm_sec allows for a positive leap second.
19556 </small>
19561 <p><b>Synopsis</b>
19562 <p><!--para 1 -->
19563 <pre>
19565 clock_t clock(void);
19566 </pre>
19567 <p><b>Description</b>
19568 <p><!--para 2 -->
19569 The clock function determines the processor time used.
19570 <p><b>Returns</b>
19571 <p><!--para 3 -->
19572 The clock function returns the implementation's best approximation to the processor
19573 time used by the program since the beginning of an implementation-defined era related
19574 only to the program invocation. To determine the time in seconds, the value returned by
19575 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
19576 the processor time used is not available or its value cannot be represented, the function
19579 <p><b>Footnotes</b>
19580 <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
19581 the program and its return value subtracted from the value returned by subsequent calls.
19582 </small>
19585 <p><b>Synopsis</b>
19586 <p><!--para 1 -->
19587 <pre>
19589 double difftime(time_t time1, time_t time0);
19590 </pre>
19591 <p><b>Description</b>
19592 <p><!--para 2 -->
19593 The difftime function computes the difference between two calendar times: time1 -
19594 time0.
19595 <p><b>Returns</b>
19596 <p><!--para 3 -->
19597 The difftime function returns the difference expressed in seconds as a double.
19602 <!--page 405 -->
19605 <p><b>Synopsis</b>
19606 <p><!--para 1 -->
19607 <pre>
19609 time_t mktime(struct tm *timeptr);
19610 </pre>
19611 <p><b>Description</b>
19612 <p><!--para 2 -->
19613 The mktime function converts the broken-down time, expressed as local time, in the
19614 structure pointed to by timeptr into a calendar time value with the same encoding as
19615 that of the values returned by the time function. The original values of the tm_wday
19616 and tm_yday components of the structure are ignored, and the original values of the
19617 other components are not restricted to the ranges indicated above.<sup><a href="#note309"><b>309)</b></a></sup> On successful
19618 completion, the values of the tm_wday and tm_yday components of the structure are
19619 set appropriately, and the other components are set to represent the specified calendar
19620 time, but with their values forced to the ranges indicated above; the final value of
19621 tm_mday is not set until tm_mon and tm_year are determined.
19622 <p><b>Returns</b>
19623 <p><!--para 3 -->
19624 The mktime function returns the specified calendar time encoded as a value of type
19625 time_t. If the calendar time cannot be represented, the function returns the value
19626 (time_t)(-1).
19627 <p><!--para 4 -->
19628 EXAMPLE What day of the week is July 4, 2001?
19629 <pre>
19632 static const char *const wday[] = {
19635 };
19636 struct tm time_str;
19637 /* ... */
19638 </pre>
19643 <!--page 406 -->
19644 <pre>
19645 time_str.tm_year = 2001 - 1900;
19646 time_str.tm_mon = 7 - 1;
19647 time_str.tm_mday = 4;
19648 time_str.tm_hour = 0;
19649 time_str.tm_min = 0;
19650 time_str.tm_sec = 1;
19651 time_str.tm_isdst = -1;
19652 if (mktime(&time_str) == (time_t)(-1))
19653 time_str.tm_wday = 7;
19655 </pre>
19658 <p><b>Footnotes</b>
19659 <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
19660 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
19661 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
19662 </small>
19665 <p><b>Synopsis</b>
19666 <p><!--para 1 -->
19667 <pre>
19669 time_t time(time_t *timer);
19670 </pre>
19671 <p><b>Description</b>
19672 <p><!--para 2 -->
19673 The time function determines the current calendar time. The encoding of the value is
19674 unspecified.
19675 <p><b>Returns</b>
19676 <p><!--para 3 -->
19677 The time function returns the implementation's best approximation to the current
19678 calendar time. The value (time_t)(-1) is returned if the calendar time is not
19679 available. If timer is not a null pointer, the return value is also assigned to the object it
19680 points to.
19683 <p><!--para 1 -->
19684 Except for the strftime function, these functions each return a pointer to one of two
19685 types of static objects: a broken-down time structure or an array of char. Execution of
19686 any of the functions that return a pointer to one of these object types may overwrite the
19687 information in any object of the same type pointed to by the value returned from any
19688 previous call to any of them and the functions are not required to avoid data races. The
19689 implementation shall behave as if no other library functions call these functions.
19692 <p><b>Synopsis</b>
19693 <p><!--para 1 -->
19694 <pre>
19696 char *asctime(const struct tm *timeptr);
19697 </pre>
19698 <p><b>Description</b>
19699 <p><!--para 2 -->
19700 The asctime function converts the broken-down time in the structure pointed to by
19701 timeptr into a string in the form
19702 <!--page 407 -->
19703 <pre>
19704 Sun Sep 16 01:03:52 1973\n\0
19705 </pre>
19706 using the equivalent of the following algorithm.
19707 char *asctime(const struct tm *timeptr)
19708 {
19709 <pre>
19710 static const char wday_name[7][3] = {
19712 };
19713 static const char mon_name[12][3] = {
19716 };
19717 static char result[26];
19719 wday_name[timeptr->tm_wday],
19720 mon_name[timeptr->tm_mon],
19721 timeptr->tm_mday, timeptr->tm_hour,
19722 timeptr->tm_min, timeptr->tm_sec,
19723 1900 + timeptr->tm_year);
19724 return result;
19725 </pre>
19726 }
19727 <p><!--para 3 -->
19728 If any of the fields of the broken-down time contain values that are outside their normal
19729 ranges,<sup><a href="#note310"><b>310)</b></a></sup> the behavior of the asctime function is undefined. Likewise, if the
19730 calculated year exceeds four digits or is less than the year 1000, the behavior is
19731 undefined.
19732 <p><b>Returns</b>
19733 <p><!--para 4 -->
19734 The asctime function returns a pointer to the string.
19736 <p><b>Footnotes</b>
19738 </small>
19741 <p><b>Synopsis</b>
19742 <p><!--para 1 -->
19743 <pre>
19745 char *ctime(const time_t *timer);
19746 </pre>
19747 <p><b>Description</b>
19748 <p><!--para 2 -->
19749 The ctime function converts the calendar time pointed to by timer to local time in the
19750 form of a string. It is equivalent to
19751 <pre>
19752 asctime(localtime(timer))
19753 </pre>
19757 <!--page 408 -->
19758 <p><b>Returns</b>
19759 <p><!--para 3 -->
19760 The ctime function returns the pointer returned by the asctime function with that
19761 broken-down time as argument.
19765 <p><b>Synopsis</b>
19766 <p><!--para 1 -->
19767 <pre>
19769 struct tm *gmtime(const time_t *timer);
19770 </pre>
19771 <p><b>Description</b>
19772 <p><!--para 2 -->
19773 The gmtime function converts the calendar time pointed to by timer into a broken-
19774 down time, expressed as UTC.
19775 <p><b>Returns</b>
19776 <p><!--para 3 -->
19777 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
19778 specified time cannot be converted to UTC.
19781 <p><b>Synopsis</b>
19782 <p><!--para 1 -->
19783 <pre>
19785 struct tm *localtime(const time_t *timer);
19786 </pre>
19787 <p><b>Description</b>
19788 <p><!--para 2 -->
19789 The localtime function converts the calendar time pointed to by timer into a
19790 broken-down time, expressed as local time.
19791 <p><b>Returns</b>
19792 <p><!--para 3 -->
19793 The localtime function returns a pointer to the broken-down time, or a null pointer if
19794 the specified time cannot be converted to local time.
19797 <p><b>Synopsis</b>
19798 <p><!--para 1 -->
19799 <!--page 409 -->
19800 <pre>
19802 size_t strftime(char * restrict s,
19803 size_t maxsize,
19804 const char * restrict format,
19805 const struct tm * restrict timeptr);
19806 </pre>
19807 <p><b>Description</b>
19808 <p><!--para 2 -->
19809 The strftime function places characters into the array pointed to by s as controlled by
19810 the string pointed to by format. The format shall be a multibyte character sequence,
19811 beginning and ending in its initial shift state. The format string consists of zero or
19812 more conversion specifiers and ordinary multibyte characters. A conversion specifier
19813 consists of a % character, possibly followed by an E or O modifier character (described
19814 below), followed by a character that determines the behavior of the conversion specifier.
19815 All ordinary multibyte characters (including the terminating null character) are copied
19816 unchanged into the array. If copying takes place between objects that overlap, the
19817 behavior is undefined. No more than maxsize characters are placed into the array.
19818 <p><!--para 3 -->
19819 Each conversion specifier is replaced by appropriate characters as described in the
19820 following list. The appropriate characters are determined using the LC_TIME category
19821 of the current locale and by the values of zero or more members of the broken-down time
19822 structure pointed to by timeptr, as specified in brackets in the description. If any of
19823 the specified values is outside the normal range, the characters stored are unspecified.
19824 %a is replaced by the locale's abbreviated weekday name. [tm_wday]
19825 %A is replaced by the locale's full weekday name. [tm_wday]
19826 %b is replaced by the locale's abbreviated month name. [tm_mon]
19827 %B is replaced by the locale's full month name. [tm_mon]
19828 %c is replaced by the locale's appropriate date and time representation. [all specified
19829 <pre>
19831 </pre>
19832 %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
19833 <pre>
19834 number (00-99). [tm_year]
19835 </pre>
19836 %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
19837 %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
19838 %e is replaced by the day of the month as a decimal number (1-31); a single digit is
19839 <pre>
19840 preceded by a space. [tm_mday]
19841 </pre>
19842 %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
19843 <pre>
19844 tm_mday]
19845 </pre>
19846 %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
19847 <pre>
19848 number (00-99). [tm_year, tm_wday, tm_yday]
19849 </pre>
19850 %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
19851 <pre>
19852 [tm_year, tm_wday, tm_yday]
19853 </pre>
19854 %h is equivalent to ''%b''. [tm_mon]
19855 %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
19856 %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
19857 %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
19858 %m is replaced by the month as a decimal number (01-12). [tm_mon]
19859 %M is replaced by the minute as a decimal number (00-59). [tm_min]
19860 %n is replaced by a new-line character.
19861 <!--page 410 -->
19862 %p is replaced by the locale's equivalent of the AM/PM designations associated with a
19863 <pre>
19864 12-hour clock. [tm_hour]
19865 </pre>
19866 %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
19867 %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
19868 %S is replaced by the second as a decimal number (00-60). [tm_sec]
19869 %t is replaced by a horizontal-tab character.
19870 %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
19871 <pre>
19872 tm_sec]
19873 </pre>
19874 %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
19875 <pre>
19876 is 1. [tm_wday]
19877 </pre>
19878 %U is replaced by the week number of the year (the first Sunday as the first day of week
19879 <pre>
19880 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
19881 </pre>
19882 %V is replaced by the ISO 8601 week number (see below) as a decimal number
19883 <pre>
19884 (01-53). [tm_year, tm_wday, tm_yday]
19885 </pre>
19886 %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
19887 <pre>
19888 [tm_wday]
19889 </pre>
19890 %W is replaced by the week number of the year (the first Monday as the first day of
19891 <pre>
19892 week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
19893 </pre>
19894 %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.26.1">7.26.1</a>]
19895 %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.26.1">7.26.1</a>]
19896 %y is replaced by the last 2 digits of the year as a decimal number (00-99).
19897 <pre>
19898 [tm_year]
19899 </pre>
19900 %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
19901 %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
19902 <pre>
19903 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
19904 zone is determinable. [tm_isdst]
19905 </pre>
19906 %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
19907 <pre>
19908 time zone is determinable. [tm_isdst]
19909 </pre>
19910 %% is replaced by %.
19911 <p><!--para 4 -->
19912 Some conversion specifiers can be modified by the inclusion of an E or O modifier
19913 character to indicate an alternative format or specification. If the alternative format or
19914 specification does not exist for the current locale, the modifier is ignored.
19915 %Ec is replaced by the locale's alternative date and time representation.
19916 %EC is replaced by the name of the base year (period) in the locale's alternative
19917 <pre>
19918 representation.
19919 </pre>
19920 %Ex is replaced by the locale's alternative date representation.
19921 %EX is replaced by the locale's alternative time representation.
19922 %Ey is replaced by the offset from %EC (year only) in the locale's alternative
19923 <pre>
19924 representation.
19925 </pre>
19926 %EY is replaced by the locale's full alternative year representation.
19927 <!--page 411 -->
19928 %Od is replaced by the day of the month, using the locale's alternative numeric symbols
19929 <pre>
19930 (filled as needed with leading zeros, or with leading spaces if there is no alternative
19931 symbol for zero).
19932 </pre>
19933 %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
19934 <pre>
19935 (filled as needed with leading spaces).
19936 </pre>
19937 %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
19938 <pre>
19939 symbols.
19940 </pre>
19941 %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
19942 <pre>
19943 symbols.
19944 </pre>
19945 %Om is replaced by the month, using the locale's alternative numeric symbols.
19946 %OM is replaced by the minutes, using the locale's alternative numeric symbols.
19947 %OS is replaced by the seconds, using the locale's alternative numeric symbols.
19948 %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
19949 <pre>
19950 representation, where Monday is 1.
19951 </pre>
19952 %OU is replaced by the week number, using the locale's alternative numeric symbols.
19953 %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
19954 <pre>
19955 symbols.
19956 </pre>
19957 %Ow is replaced by the weekday as a number, using the locale's alternative numeric
19958 <pre>
19959 symbols.
19960 </pre>
19961 %OW is replaced by the week number of the year, using the locale's alternative numeric
19962 <pre>
19963 symbols.
19964 </pre>
19965 %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
19966 <pre>
19967 symbols.
19968 </pre>
19969 <p><!--para 5 -->
19970 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
19971 weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
19972 which is also the week that includes the first Thursday of the year, and is also the first
19973 week that contains at least four days in the year. If the first Monday of January is the
19974 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
19975 for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
19976 December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
19977 the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
19978 %V is replaced by 01.
19979 <p><!--para 6 -->
19980 If a conversion specifier is not one of the above, the behavior is undefined.
19981 <p><!--para 7 -->
19983 following specifiers are:
19984 %a the first three characters of %A.
19985 %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
19986 %b the first three characters of %B.
19987 %B one of ''January'', ''February'', ... , ''December''.
19988 %c equivalent to ''%a %b %e %T %Y''.
19989 <!--page 412 -->
19990 %p one of ''AM'' or ''PM''.
19991 %r equivalent to ''%I:%M:%S %p''.
19992 %x equivalent to ''%m/%d/%y''.
19993 %X equivalent to %T.
19994 %Z implementation-defined.
19995 <p><b>Returns</b>
19996 <p><!--para 8 -->
19997 If the total number of resulting characters including the terminating null character is not
19998 more than maxsize, the strftime function returns the number of characters placed
19999 into the array pointed to by s not including the terminating null character. Otherwise,
20000 zero is returned and the contents of the array are indeterminate.
20001 <!--page 413 -->
20004 <p><!--para 1 -->
20005 The header <a href="#7.27"><uchar.h></a> declares types and functions for manipulating Unicode
20006 characters.
20007 <p><!--para 2 -->
20008 The types declared are mbstate_t (described in <a href="#7.29.1">7.29.1</a>) and size_t (described in
20010 <pre>
20011 char16_t
20012 </pre>
20013 which is an unsigned integer type used for 16-bit characters and is the same type as
20015 <pre>
20016 char32_t
20017 </pre>
20018 which is an unsigned integer type used for 32-bit characters and is the same type as
20021 <h4><a name="7.27.1" href="#7.27.1">7.27.1 Restartable multibyte/wide character conversion functions</a></h4>
20022 <p><!--para 1 -->
20023 These functions have a parameter, ps, of type pointer to mbstate_t that points to an
20024 object that can completely describe the current conversion state of the associated
20025 multibyte character sequence, which the functions alter as necessary. If ps is a null
20026 pointer, each function uses its own internal mbstate_t object instead, which is
20027 initialized at program startup to the initial conversion state; the functions are not required
20028 to avoid data races in this case. The implementation behaves as if no library function
20029 calls these functions with a null pointer for ps.
20032 <p><b>Synopsis</b>
20033 <p><!--para 1 -->
20034 <pre>
20036 size_t mbrtoc16(char16_t * restrict pc16,
20037 const char * restrict s, size_t n,
20038 mbstate_t * restrict ps);
20039 </pre>
20040 <p><b>Description</b>
20041 <p><!--para 2 -->
20042 If s is a null pointer, the mbrtoc16 function is equivalent to the call:
20043 <pre>
20045 </pre>
20046 In this case, the values of the parameters pc16 and n are ignored.
20047 <p><!--para 3 -->
20048 If s is not a null pointer, the mbrtoc16 function inspects at most n bytes beginning with
20049 the byte pointed to by s to determine the number of bytes needed to complete the next
20050 multibyte character (including any shift sequences). If the function determines that the
20051 next multibyte character is complete and valid, it determines the values of the
20052 corresponding wide characters and then, if pc16 is not a null pointer, stores the value of
20053 the first (or only) such character in the object pointed to by pc16. Subsequent calls will
20054 <!--page 414 -->
20055 store successive wide characters without consuming any additional input until all the
20056 characters have been stored. If the corresponding wide character is the null wide
20057 character, the resulting state described is the initial conversion state.
20058 <p><b>Returns</b>
20059 <p><!--para 4 -->
20060 The mbrtoc16 function returns the first of the following that applies (given the current
20061 conversion state):
20062 0 if the next n or fewer bytes complete the multibyte character that
20063 <pre>
20064 corresponds to the null wide character (which is the value stored).
20065 </pre>
20066 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
20067 <pre>
20068 character (which is the value stored); the value returned is the number
20069 of bytes that complete the multibyte character.
20070 </pre>
20071 (size_t)(-3) if the next character resulting from a previous call has been stored (no
20072 <pre>
20073 bytes from the input have been consumed by this call).
20074 </pre>
20075 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
20076 <pre>
20077 multibyte character, and all n bytes have been processed (no value is
20079 </pre>
20080 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
20081 <pre>
20082 do not contribute to a complete and valid multibyte character (no
20083 value is stored); the value of the macro EILSEQ is stored in errno,
20084 and the conversion state is unspecified.
20085 </pre>
20087 <p><b>Footnotes</b>
20088 <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
20089 sequence of redundant shift sequences (for implementations with state-dependent encodings).
20090 </small>
20093 <p><b>Synopsis</b>
20094 <p><!--para 1 -->
20095 <pre>
20097 size_t c16rtomb(char * restrict s, char16_t c16,
20098 mbstate_t * restrict ps);
20099 </pre>
20100 <p><b>Description</b>
20101 <p><!--para 2 -->
20102 If s is a null pointer, the c16rtomb function is equivalent to the call
20103 <pre>
20104 c16rtomb(buf, L'\0', ps)
20105 </pre>
20106 where buf is an internal buffer.
20107 <p><!--para 3 -->
20108 If s is not a null pointer, the c16rtomb function determines the number of bytes needed
20109 to represent the multibyte character that corresponds to the wide character given by c16
20110 (including any shift sequences), and stores the multibyte character representation in the
20113 <!--page 415 -->
20114 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
20115 c16 is a null wide character, a null byte is stored, preceded by any shift sequence needed
20116 to restore the initial shift state; the resulting state described is the initial conversion state.
20117 <p><b>Returns</b>
20118 <p><!--para 4 -->
20119 The c16rtomb function returns the number of bytes stored in the array object (including
20120 any shift sequences). When c16 is not a valid wide character, an encoding error occurs:
20121 the function stores the value of the macro EILSEQ in errno and returns
20122 (size_t)(-1); the conversion state is unspecified.
20125 <p><b>Synopsis</b>
20126 <p><!--para 1 -->
20127 <pre>
20129 size_t mbrtoc32(char32_t * restrict pc32,
20130 const char * restrict s, size_t n,
20131 mbstate_t * restrict ps);
20132 </pre>
20133 <p><b>Description</b>
20134 <p><!--para 2 -->
20135 If s is a null pointer, the mbrtoc32 function is equivalent to the call:
20136 <pre>
20138 </pre>
20139 In this case, the values of the parameters pc32 and n are ignored.
20140 <p><!--para 3 -->
20141 If s is not a null pointer, the mbrtoc32 function inspects at most n bytes beginning with
20142 the byte pointed to by s to determine the number of bytes needed to complete the next
20143 multibyte character (including any shift sequences). If the function determines that the
20144 next multibyte character is complete and valid, it determines the values of the
20145 corresponding wide characters and then, if pc32 is not a null pointer, stores the value of
20146 the first (or only) such character in the object pointed to by pc32. Subsequent calls will
20147 store successive wide characters without consuming any additional input until all the
20148 characters have been stored. If the corresponding wide character is the null wide
20149 character, the resulting state described is the initial conversion state.
20150 <p><b>Returns</b>
20151 <p><!--para 4 -->
20152 The mbrtoc32 function returns the first of the following that applies (given the current
20153 conversion state):
20154 0 if the next n or fewer bytes complete the multibyte character that
20155 <pre>
20156 corresponds to the null wide character (which is the value stored).
20157 </pre>
20158 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
20159 <!--page 416 -->
20160 <pre>
20161 character (which is the value stored); the value returned is the number
20162 of bytes that complete the multibyte character.
20163 </pre>
20164 (size_t)(-3) if the next character resulting from a previous call has been stored (no
20165 <pre>
20166 bytes from the input have been consumed by this call).
20167 </pre>
20168 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
20169 <pre>
20170 multibyte character, and all n bytes have been processed (no value is
20172 </pre>
20173 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
20174 <pre>
20175 do not contribute to a complete and valid multibyte character (no
20176 value is stored); the value of the macro EILSEQ is stored in errno,
20177 and the conversion state is unspecified.
20178 </pre>
20180 <p><b>Footnotes</b>
20181 <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
20182 sequence of redundant shift sequences (for implementations with state-dependent encodings).
20183 </small>
20186 <p><b>Synopsis</b>
20187 <p><!--para 1 -->
20188 <pre>
20190 size_t c32rtomb(char * restrict s, char32_t c32,
20191 mbstate_t * restrict ps);
20192 </pre>
20193 <p><b>Description</b>
20194 <p><!--para 2 -->
20195 If s is a null pointer, the c32rtomb function is equivalent to the call
20196 <pre>
20197 c32rtomb(buf, L'\0', ps)
20198 </pre>
20199 where buf is an internal buffer.
20200 <p><!--para 3 -->
20201 If s is not a null pointer, the c32rtomb function determines the number of bytes needed
20202 to represent the multibyte character that corresponds to the wide character given by c32
20203 (including any shift sequences), and stores the multibyte character representation in the
20204 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
20205 c32 is a null wide character, a null byte is stored, preceded by any shift sequence needed
20206 to restore the initial shift state; the resulting state described is the initial conversion state.
20207 <p><b>Returns</b>
20208 <p><!--para 4 -->
20209 The c32rtomb function returns the number of bytes stored in the array object (including
20210 any shift sequences). When c32 is not a valid wide character, an encoding error occurs:
20211 the function stores the value of the macro EILSEQ in errno and returns
20212 (size_t)(-1); the conversion state is unspecified.
20217 <!--page 417 -->
20219 <h3><a name="7.28" href="#7.28">7.28 Extended multibyte and wide character utilities <wchar.h></a></h3>
20222 <p><!--para 1 -->
20223 The header <a href="#7.28"><wchar.h></a> defines four macros, and declares four data types, one tag, and
20225 <p><!--para 2 -->
20227 <pre>
20228 mbstate_t
20229 </pre>
20230 which is a complete object type other than an array type that can hold the conversion state
20231 information necessary to convert between sequences of multibyte characters and wide
20232 characters;
20233 <pre>
20234 wint_t
20235 </pre>
20236 which is an integer type unchanged by default argument promotions that can hold any
20237 value corresponding to members of the extended character set, as well as at least one
20238 value that does not correspond to any member of the extended character set (see WEOF
20240 <pre>
20241 struct tm
20242 </pre>
20243 which is declared as an incomplete structure type (the contents are described in <a href="#7.26.1">7.26.1</a>).
20244 <p><!--para 3 -->
20247 <pre>
20248 WEOF
20249 </pre>
20250 which expands to a constant expression of type wint_t whose value does not
20251 correspond to any member of the extended character set.<sup><a href="#note315"><b>315)</b></a></sup> It is accepted (and returned)
20252 by several functions in this subclause to indicate end-of-file, that is, no more input from a
20253 stream. It is also used as a wide character value that does not correspond to any member
20254 of the extended character set.
20255 <p><!--para 4 -->
20256 The functions declared are grouped as follows:
20257 <ul>
20258 <li> Functions that perform input and output of wide characters, or multibyte characters,
20259 or both;
20260 <li> Functions that provide wide string numeric conversion;
20261 <li> Functions that perform general wide string manipulation;
20264 <!--page 418 -->
20265 <li> Functions for wide string date and time conversion; and
20266 <li> Functions that provide extended capabilities for conversion between multibyte and
20267 wide character sequences.
20268 </ul>
20269 <p><!--para 5 -->
20270 Unless explicitly stated otherwise, if the execution of a function described in this
20271 subclause causes copying to take place between objects that overlap, the behavior is
20272 undefined.
20274 <p><b>Footnotes</b>
20275 <p><small><a name="note313" href="#note313">313)</a> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
20276 </small>
20277 <p><small><a name="note314" href="#note314">314)</a> wchar_t and wint_t can be the same integer type.
20278 </small>
20279 <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.
20280 </small>
20282 <h4><a name="7.28.2" href="#7.28.2">7.28.2 Formatted wide character input/output functions</a></h4>
20283 <p><!--para 1 -->
20284 The formatted wide character input/output functions shall behave as if there is a sequence
20285 point after the actions associated with each specifier.<sup><a href="#note316"><b>316)</b></a></sup>
20287 <p><b>Footnotes</b>
20288 <p><small><a name="note316" href="#note316">316)</a> The fwprintf functions perform writes to memory for the %n specifier.
20289 </small>
20292 <p><b>Synopsis</b>
20293 <p><!--para 1 -->
20294 <pre>
20297 int fwprintf(FILE * restrict stream,
20298 const wchar_t * restrict format, ...);
20299 </pre>
20300 <p><b>Description</b>
20301 <p><!--para 2 -->
20302 The fwprintf function writes output to the stream pointed to by stream, under
20303 control of the wide string pointed to by format that specifies how subsequent arguments
20304 are converted for output. If there are insufficient arguments for the format, the behavior
20305 is undefined. If the format is exhausted while arguments remain, the excess arguments
20306 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
20307 when the end of the format string is encountered.
20308 <p><!--para 3 -->
20309 The format is composed of zero or more directives: ordinary wide characters (not %),
20310 which are copied unchanged to the output stream; and conversion specifications, each of
20311 which results in fetching zero or more subsequent arguments, converting them, if
20312 applicable, according to the corresponding conversion specifier, and then writing the
20313 result to the output stream.
20314 <p><!--para 4 -->
20315 Each conversion specification is introduced by the wide character %. After the %, the
20316 following appear in sequence:
20317 <ul>
20318 <li> Zero or more flags (in any order) that modify the meaning of the conversion
20319 specification.
20320 <li> An optional minimum field width. If the converted value has fewer wide characters
20321 than the field width, it is padded with spaces (by default) on the left (or right, if the
20324 <!--page 419 -->
20325 left adjustment flag, described later, has been given) to the field width. The field
20326 width takes the form of an asterisk * (described later) or a nonnegative decimal
20328 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
20329 o, u, x, and X conversions, the number of digits to appear after the decimal-point
20330 wide character for a, A, e, E, f, and F conversions, the maximum number of
20331 significant digits for the g and G conversions, or the maximum number of wide
20332 characters to be written for s conversions. The precision takes the form of a period
20333 (.) followed either by an asterisk * (described later) or by an optional decimal
20334 integer; if only the period is specified, the precision is taken as zero. If a precision
20335 appears with any other conversion specifier, the behavior is undefined.
20336 <li> An optional length modifier that specifies the size of the argument.
20337 <li> A conversion specifier wide character that specifies the type of conversion to be
20338 applied.
20339 </ul>
20340 <p><!--para 5 -->
20341 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
20342 this case, an int argument supplies the field width or precision. The arguments
20343 specifying field width, or precision, or both, shall appear (in that order) before the
20344 argument (if any) to be converted. A negative field width argument is taken as a - flag
20345 followed by a positive field width. A negative precision argument is taken as if the
20346 precision were omitted.
20347 <p><!--para 6 -->
20348 The flag wide characters and their meanings are:
20349 - The result of the conversion is left-justified within the field. (It is right-justified if
20350 <pre>
20351 this flag is not specified.)
20352 </pre>
20353 + The result of a signed conversion always begins with a plus or minus sign. (It
20354 <pre>
20355 begins with a sign only when a negative value is converted if this flag is not
20357 </pre>
20358 space If the first wide character of a signed conversion is not a sign, or if a signed
20359 <pre>
20360 conversion results in no wide characters, a space is prefixed to the result. If the
20361 space and + flags both appear, the space flag is ignored.
20362 </pre>
20363 # The result is converted to an ''alternative form''. For o conversion, it increases
20364 <pre>
20365 the precision, if and only if necessary, to force the first digit of the result to be a
20366 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
20367 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
20368 </pre>
20371 <!--page 420 -->
20372 <pre>
20373 and G conversions, the result of converting a floating-point number always
20374 contains a decimal-point wide character, even if no digits follow it. (Normally, a
20375 decimal-point wide character appears in the result of these conversions only if a
20376 digit follows it.) For g and G conversions, trailing zeros are not removed from the
20377 result. For other conversions, the behavior is undefined.
20378 </pre>
20379 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
20380 <pre>
20381 (following any indication of sign or base) are used to pad to the field width rather
20382 than performing space padding, except when converting an infinity or NaN. If the
20383 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
20384 conversions, if a precision is specified, the 0 flag is ignored. For other
20385 conversions, the behavior is undefined.
20386 </pre>
20387 <p><!--para 7 -->
20388 The length modifiers and their meanings are:
20389 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
20390 <pre>
20391 signed char or unsigned char argument (the argument will have
20392 been promoted according to the integer promotions, but its value shall be
20393 converted to signed char or unsigned char before printing); or that
20394 a following n conversion specifier applies to a pointer to a signed char
20395 argument.
20396 </pre>
20397 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
20398 <pre>
20399 short int or unsigned short int argument (the argument will
20400 have been promoted according to the integer promotions, but its value shall
20401 be converted to short int or unsigned short int before printing);
20402 or that a following n conversion specifier applies to a pointer to a short
20403 int argument.
20404 </pre>
20405 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
20406 <pre>
20407 long int or unsigned long int argument; that a following n
20408 conversion specifier applies to a pointer to a long int argument; that a
20409 following c conversion specifier applies to a wint_t argument; that a
20410 following s conversion specifier applies to a pointer to a wchar_t
20411 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
20412 specifier.
20413 </pre>
20414 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
20415 <pre>
20416 long long int or unsigned long long int argument; or that a
20417 following n conversion specifier applies to a pointer to a long long int
20418 argument.
20419 </pre>
20420 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
20421 <!--page 421 -->
20422 <pre>
20423 an intmax_t or uintmax_t argument; or that a following n conversion
20424 specifier applies to a pointer to an intmax_t argument.
20425 </pre>
20426 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
20427 <pre>
20428 size_t or the corresponding signed integer type argument; or that a
20429 following n conversion specifier applies to a pointer to a signed integer type
20430 corresponding to size_t argument.
20431 </pre>
20432 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
20433 <pre>
20434 ptrdiff_t or the corresponding unsigned integer type argument; or that a
20435 following n conversion specifier applies to a pointer to a ptrdiff_t
20436 argument.
20437 </pre>
20438 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
20439 <pre>
20440 applies to a long double argument.
20441 </pre>
20442 If a length modifier appears with any conversion specifier other than as specified above,
20443 the behavior is undefined.
20444 <p><!--para 8 -->
20445 The conversion specifiers and their meanings are:
20446 d,i The int argument is converted to signed decimal in the style [-]dddd. The
20447 <pre>
20448 precision specifies the minimum number of digits to appear; if the value
20449 being converted can be represented in fewer digits, it is expanded with
20450 leading zeros. The default precision is 1. The result of converting a zero
20451 value with a precision of zero is no wide characters.
20452 </pre>
20453 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
20454 <pre>
20455 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
20456 letters abcdef are used for x conversion and the letters ABCDEF for X
20457 conversion. The precision specifies the minimum number of digits to appear;
20458 if the value being converted can be represented in fewer digits, it is expanded
20459 with leading zeros. The default precision is 1. The result of converting a
20460 zero value with a precision of zero is no wide characters.
20461 </pre>
20462 f,F A double argument representing a floating-point number is converted to
20463 <!--page 422 -->
20464 <pre>
20465 decimal notation in the style [-]ddd.ddd, where the number of digits after
20466 the decimal-point wide character is equal to the precision specification. If the
20467 precision is missing, it is taken as 6; if the precision is zero and the # flag is
20468 not specified, no decimal-point wide character appears. If a decimal-point
20469 wide character appears, at least one digit appears before it. The value is
20470 rounded to the appropriate number of digits.
20471 A double argument representing an infinity is converted in one of the styles
20472 [-]inf or [-]infinity -- which style is implementation-defined. A
20473 double argument representing a NaN is converted in one of the styles
20474 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
20475 any n-wchar-sequence, is implementation-defined. The F conversion
20476 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
20478 </pre>
20479 e,E A double argument representing a floating-point number is converted in the
20480 <pre>
20481 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
20482 argument is nonzero) before the decimal-point wide character and the number
20483 of digits after it is equal to the precision; if the precision is missing, it is taken
20484 as 6; if the precision is zero and the # flag is not specified, no decimal-point
20485 wide character appears. The value is rounded to the appropriate number of
20486 digits. The E conversion specifier produces a number with E instead of e
20487 introducing the exponent. The exponent always contains at least two digits,
20488 and only as many more digits as necessary to represent the exponent. If the
20489 value is zero, the exponent is zero.
20490 A double argument representing an infinity or NaN is converted in the style
20491 of an f or F conversion specifier.
20492 </pre>
20493 g,G A double argument representing a floating-point number is converted in
20494 <pre>
20495 style f or e (or in style F or E in the case of a G conversion specifier),
20496 depending on the value converted and the precision. Let P equal the
20497 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
20498 Then, if a conversion with style E would have an exponent of X:
20499 -- if P > X >= -4, the conversion is with style f (or F) and precision
20500 P - (X + 1).
20501 -- otherwise, the conversion is with style e (or E) and precision P - 1.
20502 Finally, unless the # flag is used, any trailing zeros are removed from the
20503 fractional portion of the result and the decimal-point wide character is
20504 removed if there is no fractional portion remaining.
20505 A double argument representing an infinity or NaN is converted in the style
20506 of an f or F conversion specifier.
20507 </pre>
20508 a,A A double argument representing a floating-point number is converted in the
20509 <pre>
20510 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
20511 nonzero if the argument is a normalized floating-point number and is
20512 otherwise unspecified) before the decimal-point wide character<sup><a href="#note320"><b>320)</b></a></sup> and the
20513 number of hexadecimal digits after it is equal to the precision; if the precision
20514 is missing and FLT_RADIX is a power of 2, then the precision is sufficient
20515 </pre>
20518 <!--page 423 -->
20519 <pre>
20520 for an exact representation of the value; if the precision is missing and
20521 FLT_RADIX is not a power of 2, then the precision is sufficient to
20522 distinguish<sup><a href="#note321"><b>321)</b></a></sup> values of type double, except that trailing zeros may be
20523 omitted; if the precision is zero and the # flag is not specified, no decimal-
20524 point wide character appears. The letters abcdef are used for a conversion
20525 and the letters ABCDEF for A conversion. The A conversion specifier
20526 produces a number with X and P instead of x and p. The exponent always
20527 contains at least one digit, and only as many more digits as necessary to
20528 represent the decimal exponent of 2. If the value is zero, the exponent is
20529 zero.
20530 A double argument representing an infinity or NaN is converted in the style
20531 of an f or F conversion specifier.
20532 </pre>
20533 c If no l length modifier is present, the int argument is converted to a wide
20534 <pre>
20535 character as if by calling btowc and the resulting wide character is written.
20536 If an l length modifier is present, the wint_t argument is converted to
20537 wchar_t and written.
20538 </pre>
20539 s If no l length modifier is present, the argument shall be a pointer to the initial
20540 <pre>
20541 element of a character array containing a multibyte character sequence
20542 beginning in the initial shift state. Characters from the array are converted as
20543 if by repeated calls to the mbrtowc function, with the conversion state
20544 described by an mbstate_t object initialized to zero before the first
20545 multibyte character is converted, and written up to (but not including) the
20546 terminating null wide character. If the precision is specified, no more than
20547 that many wide characters are written. If the precision is not specified or is
20548 greater than the size of the converted array, the converted array shall contain a
20549 null wide character.
20550 If an l length modifier is present, the argument shall be a pointer to the initial
20551 element of an array of wchar_t type. Wide characters from the array are
20552 written up to (but not including) a terminating null wide character. If the
20553 precision is specified, no more than that many wide characters are written. If
20554 the precision is not specified or is greater than the size of the array, the array
20555 shall contain a null wide character.
20556 </pre>
20557 p The argument shall be a pointer to void. The value of the pointer is
20558 <pre>
20559 converted to a sequence of printing wide characters, in an implementation-
20560 </pre>
20562 <!--page 424 -->
20563 <pre>
20564 defined manner.
20565 </pre>
20566 n The argument shall be a pointer to signed integer into which is written the
20567 <pre>
20568 number of wide characters written to the output stream so far by this call to
20569 fwprintf. No argument is converted, but one is consumed. If the
20570 conversion specification includes any flags, a field width, or a precision, the
20571 behavior is undefined.
20572 </pre>
20573 % A % wide character is written. No argument is converted. The complete
20574 <pre>
20575 conversion specification shall be %%.
20576 </pre>
20577 <p><!--para 9 -->
20578 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note322"><b>322)</b></a></sup> If any argument is
20579 not the correct type for the corresponding conversion specification, the behavior is
20580 undefined.
20581 <p><!--para 10 -->
20582 In no case does a nonexistent or small field width cause truncation of a field; if the result
20583 of a conversion is wider than the field width, the field is expanded to contain the
20584 conversion result.
20585 <p><!--para 11 -->
20586 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
20587 to a hexadecimal floating number with the given precision.
20588 <p><b>Recommended practice</b>
20589 <p><!--para 12 -->
20590 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
20591 representable in the given precision, the result should be one of the two adjacent numbers
20592 in hexadecimal floating style with the given precision, with the extra stipulation that the
20593 error should have a correct sign for the current rounding direction.
20594 <p><!--para 13 -->
20595 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
20596 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note323"><b>323)</b></a></sup> If the number of
20597 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
20598 representable with DECIMAL_DIG digits, then the result should be an exact
20599 representation with trailing zeros. Otherwise, the source value is bounded by two
20600 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
20601 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
20602 the error should have a correct sign for the current rounding direction.
20603 <p><b>Returns</b>
20604 <p><!--para 14 -->
20605 The fwprintf function returns the number of wide characters transmitted, or a negative
20606 value if an output or encoding error occurred.
20608 <!--page 425 -->
20609 <p><b>Environmental limits</b>
20610 <p><!--para 15 -->
20611 The number of wide characters that can be produced by any single conversion shall be at
20612 least 4095.
20613 <p><!--para 16 -->
20614 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
20615 places:
20616 <pre>
20620 /* ... */
20621 wchar_t *weekday, *month; // pointers to wide strings
20622 int day, hour, min;
20624 weekday, month, day, hour, min);
20626 </pre>
20628 <p><b> Forward references</b>: the btowc function (<a href="#7.28.6.1.1">7.28.6.1.1</a>), the mbrtowc function
20631 <p><b>Footnotes</b>
20632 <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.
20633 </small>
20634 <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,
20635 include a minus sign.
20636 </small>
20637 <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
20638 meaning; the # and 0 flag wide characters have no effect.
20639 </small>
20640 <p><small><a name="note320" href="#note320">320)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
20641 character so that subsequent digits align to nibble (4-bit) boundaries.
20642 </small>
20643 <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
20644 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
20645 might suffice depending on the implementation's scheme for determining the digit to the left of the
20646 decimal-point wide character.
20647 </small>
20648 <p><small><a name="note322" href="#note322">322)</a> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
20649 </small>
20650 <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
20651 given format specifier. The number of significant digits is determined by the format specifier, and in
20652 the case of fixed-point conversion by the source value as well.
20653 </small>
20656 <p><b>Synopsis</b>
20657 <p><!--para 1 -->
20658 <pre>
20661 int fwscanf(FILE * restrict stream,
20662 const wchar_t * restrict format, ...);
20663 </pre>
20664 <p><b>Description</b>
20665 <p><!--para 2 -->
20666 The fwscanf function reads input from the stream pointed to by stream, under
20667 control of the wide string pointed to by format that specifies the admissible input
20668 sequences and how they are to be converted for assignment, using subsequent arguments
20669 as pointers to the objects to receive the converted input. If there are insufficient
20670 arguments for the format, the behavior is undefined. If the format is exhausted while
20671 arguments remain, the excess arguments are evaluated (as always) but are otherwise
20672 ignored.
20673 <p><!--para 3 -->
20674 The format is composed of zero or more directives: one or more white-space wide
20675 characters, an ordinary wide character (neither % nor a white-space wide character), or a
20676 conversion specification. Each conversion specification is introduced by the wide
20677 character %. After the %, the following appear in sequence:
20678 <ul>
20679 <li> An optional assignment-suppressing wide character *.
20680 <li> An optional decimal integer greater than zero that specifies the maximum field width
20681 (in wide characters).
20682 <!--page 426 -->
20683 <li> An optional length modifier that specifies the size of the receiving object.
20684 <li> A conversion specifier wide character that specifies the type of conversion to be
20685 applied.
20686 </ul>
20687 <p><!--para 4 -->
20688 The fwscanf function executes each directive of the format in turn. When all directives
20689 have been executed, or if a directive fails (as detailed below), the function returns.
20690 Failures are described as input failures (due to the occurrence of an encoding error or the
20691 unavailability of input characters), or matching failures (due to inappropriate input).
20692 <p><!--para 5 -->
20693 A directive composed of white-space wide character(s) is executed by reading input up to
20694 the first non-white-space wide character (which remains unread), or until no more wide
20695 characters can be read.
20696 <p><!--para 6 -->
20697 A directive that is an ordinary wide character is executed by reading the next wide
20698 character of the stream. If that wide character differs from the directive, the directive
20699 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
20700 of-file, an encoding error, or a read error prevents a wide character from being read, the
20701 directive fails.
20702 <p><!--para 7 -->
20703 A directive that is a conversion specification defines a set of matching input sequences, as
20704 described below for each specifier. A conversion specification is executed in the
20705 following steps:
20706 <p><!--para 8 -->
20707 Input white-space wide characters (as specified by the iswspace function) are skipped,
20708 unless the specification includes a [, c, or n specifier.<sup><a href="#note324"><b>324)</b></a></sup>
20709 <p><!--para 9 -->
20710 An input item is read from the stream, unless the specification includes an n specifier. An
20711 input item is defined as the longest sequence of input wide characters which does not
20712 exceed any specified field width and which is, or is a prefix of, a matching input
20713 sequence.<sup><a href="#note325"><b>325)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
20714 length of the input item is zero, the execution of the directive fails; this condition is a
20715 matching failure unless end-of-file, an encoding error, or a read error prevented input
20716 from the stream, in which case it is an input failure.
20717 <p><!--para 10 -->
20718 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
20719 count of input wide characters) is converted to a type appropriate to the conversion
20720 specifier. If the input item is not a matching sequence, the execution of the directive fails:
20721 this condition is a matching failure. Unless assignment suppression was indicated by a *,
20722 the result of the conversion is placed in the object pointed to by the first argument
20723 following the format argument that has not already received a conversion result. If this
20726 <!--page 427 -->
20727 object does not have an appropriate type, or if the result of the conversion cannot be
20728 represented in the object, the behavior is undefined.
20729 <p><!--para 11 -->
20730 The length modifiers and their meanings are:
20731 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
20732 <pre>
20733 to an argument with type pointer to signed char or unsigned char.
20734 </pre>
20735 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
20736 <pre>
20737 to an argument with type pointer to short int or unsigned short
20738 int.
20739 </pre>
20740 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
20741 <pre>
20742 to an argument with type pointer to long int or unsigned long
20743 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
20744 an argument with type pointer to double; or that a following c, s, or [
20745 conversion specifier applies to an argument with type pointer to wchar_t.
20746 </pre>
20747 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
20748 <pre>
20749 to an argument with type pointer to long long int or unsigned
20750 long long int.
20751 </pre>
20752 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
20753 <pre>
20754 to an argument with type pointer to intmax_t or uintmax_t.
20755 </pre>
20756 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
20757 <pre>
20758 to an argument with type pointer to size_t or the corresponding signed
20759 integer type.
20760 </pre>
20761 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
20762 <pre>
20763 to an argument with type pointer to ptrdiff_t or the corresponding
20764 unsigned integer type.
20765 </pre>
20766 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
20767 <pre>
20768 applies to an argument with type pointer to long double.
20769 </pre>
20770 If a length modifier appears with any conversion specifier other than as specified above,
20771 the behavior is undefined.
20772 <p><!--para 12 -->
20773 The conversion specifiers and their meanings are:
20774 d Matches an optionally signed decimal integer, whose format is the same as
20775 <pre>
20776 expected for the subject sequence of the wcstol function with the value 10
20777 for the base argument. The corresponding argument shall be a pointer to
20778 signed integer.
20779 </pre>
20780 i Matches an optionally signed integer, whose format is the same as expected
20781 <!--page 428 -->
20782 <pre>
20783 for the subject sequence of the wcstol function with the value 0 for the
20784 base argument. The corresponding argument shall be a pointer to signed
20785 integer.
20786 </pre>
20787 o Matches an optionally signed octal integer, whose format is the same as
20788 <pre>
20789 expected for the subject sequence of the wcstoul function with the value 8
20790 for the base argument. The corresponding argument shall be a pointer to
20791 unsigned integer.
20792 </pre>
20793 u Matches an optionally signed decimal integer, whose format is the same as
20794 <pre>
20795 expected for the subject sequence of the wcstoul function with the value 10
20796 for the base argument. The corresponding argument shall be a pointer to
20797 unsigned integer.
20798 </pre>
20799 x Matches an optionally signed hexadecimal integer, whose format is the same
20800 <pre>
20801 as expected for the subject sequence of the wcstoul function with the value
20802 16 for the base argument. The corresponding argument shall be a pointer to
20803 unsigned integer.
20804 </pre>
20805 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
20806 <pre>
20807 format is the same as expected for the subject sequence of the wcstod
20808 function. The corresponding argument shall be a pointer to floating.
20809 </pre>
20810 c Matches a sequence of wide characters of exactly the number specified by the
20811 <pre>
20812 field width (1 if no field width is present in the directive).
20813 If no l length modifier is present, characters from the input field are
20814 converted as if by repeated calls to the wcrtomb function, with the
20815 conversion state described by an mbstate_t object initialized to zero
20816 before the first wide character is converted. The corresponding argument
20817 shall be a pointer to the initial element of a character array large enough to
20818 accept the sequence. No null character is added.
20819 If an l length modifier is present, the corresponding argument shall be a
20820 pointer to the initial element of an array of wchar_t large enough to accept
20821 the sequence. No null wide character is added.
20822 </pre>
20823 s Matches a sequence of non-white-space wide characters.
20824 <!--page 429 -->
20825 <pre>
20826 If no l length modifier is present, characters from the input field are
20827 converted as if by repeated calls to the wcrtomb function, with the
20828 conversion state described by an mbstate_t object initialized to zero
20829 before the first wide character is converted. The corresponding argument
20830 shall be a pointer to the initial element of a character array large enough to
20831 accept the sequence and a terminating null character, which will be added
20832 automatically.
20833 If an l length modifier is present, the corresponding argument shall be a
20834 pointer to the initial element of an array of wchar_t large enough to accept
20835 the sequence and the terminating null wide character, which will be added
20836 automatically.
20837 </pre>
20838 [ Matches a nonempty sequence of wide characters from a set of expected
20839 <pre>
20840 characters (the scanset).
20841 If no l length modifier is present, characters from the input field are
20842 converted as if by repeated calls to the wcrtomb function, with the
20843 conversion state described by an mbstate_t object initialized to zero
20844 before the first wide character is converted. The corresponding argument
20845 shall be a pointer to the initial element of a character array large enough to
20846 accept the sequence and a terminating null character, which will be added
20847 automatically.
20848 If an l length modifier is present, the corresponding argument shall be a
20849 pointer to the initial element of an array of wchar_t large enough to accept
20850 the sequence and the terminating null wide character, which will be added
20851 automatically.
20852 The conversion specifier includes all subsequent wide characters in the
20853 format string, up to and including the matching right bracket (]). The wide
20854 characters between the brackets (the scanlist) compose the scanset, unless the
20855 wide character after the left bracket is a circumflex (^), in which case the
20856 scanset contains all wide characters that do not appear in the scanlist between
20857 the circumflex and the right bracket. If the conversion specifier begins with
20858 [] or [^], the right bracket wide character is in the scanlist and the next
20859 following right bracket wide character is the matching right bracket that ends
20860 the specification; otherwise the first following right bracket wide character is
20861 the one that ends the specification. If a - wide character is in the scanlist and
20862 is not the first, nor the second where the first wide character is a ^, nor the
20863 last character, the behavior is implementation-defined.
20864 </pre>
20865 p Matches an implementation-defined set of sequences, which should be the
20866 <pre>
20867 same as the set of sequences that may be produced by the %p conversion of
20868 the fwprintf function. The corresponding argument shall be a pointer to a
20869 pointer to void. The input item is converted to a pointer value in an
20870 implementation-defined manner. If the input item is a value converted earlier
20871 during the same program execution, the pointer that results shall compare
20872 equal to that value; otherwise the behavior of the %p conversion is undefined.
20873 </pre>
20874 n No input is consumed. The corresponding argument shall be a pointer to
20875 <!--page 430 -->
20876 <pre>
20877 signed integer into which is to be written the number of wide characters read
20878 from the input stream so far by this call to the fwscanf function. Execution
20879 of a %n directive does not increment the assignment count returned at the
20880 completion of execution of the fwscanf function. No argument is
20881 converted, but one is consumed. If the conversion specification includes an
20882 assignment-suppressing wide character or a field width, the behavior is
20883 undefined.
20884 </pre>
20885 % Matches a single % wide character; no conversion or assignment occurs. The
20886 <pre>
20887 complete conversion specification shall be %%.
20888 </pre>
20889 <p><!--para 13 -->
20890 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note326"><b>326)</b></a></sup>
20891 <p><!--para 14 -->
20892 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
20893 respectively, a, e, f, g, and x.
20894 <p><!--para 15 -->
20895 Trailing white space (including new-line wide characters) is left unread unless matched
20896 by a directive. The success of literal matches and suppressed assignments is not directly
20897 determinable other than via the %n directive.
20898 <p><b>Returns</b>
20899 <p><!--para 16 -->
20900 The fwscanf function returns the value of the macro EOF if an input failure occurs
20901 before the first conversion (if any) has completed. Otherwise, the function returns the
20902 number of input items assigned, which can be fewer than provided for, or even zero, in
20903 the event of an early matching failure.
20904 <p><!--para 17 -->
20905 EXAMPLE 1 The call:
20906 <pre>
20909 /* ... */
20910 int n, i; float x; wchar_t name[50];
20912 </pre>
20913 with the input line:
20914 <pre>
20915 25 54.32E-1 thompson
20916 </pre>
20917 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
20918 thompson\0.
20920 <p><!--para 18 -->
20921 EXAMPLE 2 The call:
20922 <pre>
20925 /* ... */
20926 int i; float x; double y;
20928 </pre>
20929 with input:
20930 <pre>
20931 56789 0123 56a72
20932 </pre>
20933 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
20934 56.0. The next wide character read from the input stream will be a.
20937 <!--page 431 -->
20938 <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
20939 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.28.4.1.2">7.28.4.1.2</a>), the wcrtomb
20942 <p><b>Footnotes</b>
20943 <p><small><a name="note324" href="#note324">324)</a> These white-space wide characters are not counted against a specified field width.
20944 </small>
20945 <p><small><a name="note325" href="#note325">325)</a> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
20946 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
20947 </small>
20948 <p><small><a name="note326" href="#note326">326)</a> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
20949 </small>
20952 <p><b>Synopsis</b>
20953 <p><!--para 1 -->
20954 <pre>
20956 int swprintf(wchar_t * restrict s,
20957 size_t n,
20958 const wchar_t * restrict format, ...);
20959 </pre>
20960 <p><b>Description</b>
20961 <p><!--para 2 -->
20962 The swprintf function is equivalent to fwprintf, except that the argument s
20963 specifies an array of wide characters into which the generated output is to be written,
20964 rather than written to a stream. No more than n wide characters are written, including a
20965 terminating null wide character, which is always added (unless n is zero).
20966 <p><b>Returns</b>
20967 <p><!--para 3 -->
20968 The swprintf function returns the number of wide characters written in the array, not
20969 counting the terminating null wide character, or a negative value if an encoding error
20970 occurred or if n or more wide characters were requested to be written.
20973 <p><b>Synopsis</b>
20974 <p><!--para 1 -->
20975 <pre>
20977 int swscanf(const wchar_t * restrict s,
20978 const wchar_t * restrict format, ...);
20979 </pre>
20980 <p><b>Description</b>
20981 <p><!--para 2 -->
20982 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
20983 wide string from which the input is to be obtained, rather than from a stream. Reaching
20984 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
20985 function.
20986 <p><b>Returns</b>
20987 <p><!--para 3 -->
20988 The swscanf function returns the value of the macro EOF if an input failure occurs
20989 before the first conversion (if any) has completed. Otherwise, the swscanf function
20990 returns the number of input items assigned, which can be fewer than provided for, or even
20991 zero, in the event of an early matching failure.
20992 <!--page 432 -->
20995 <p><b>Synopsis</b>
20996 <p><!--para 1 -->
20997 <pre>
21001 int vfwprintf(FILE * restrict stream,
21002 const wchar_t * restrict format,
21003 va_list arg);
21004 </pre>
21005 <p><b>Description</b>
21006 <p><!--para 2 -->
21007 The vfwprintf function is equivalent to fwprintf, with the variable argument list
21008 replaced by arg, which shall have been initialized by the va_start macro (and
21009 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
21011 <p><b>Returns</b>
21012 <p><!--para 3 -->
21013 The vfwprintf function returns the number of wide characters transmitted, or a
21014 negative value if an output or encoding error occurred.
21015 <p><!--para 4 -->
21016 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
21017 routine.
21018 <pre>
21022 void error(char *function_name, wchar_t *format, ...)
21023 {
21024 va_list args;
21025 va_start(args, format);
21026 // print out name of function causing error
21028 // print out remainder of message
21029 vfwprintf(stderr, format, args);
21030 va_end(args);
21031 }
21032 </pre>
21037 <!--page 433 -->
21039 <p><b>Footnotes</b>
21040 <p><small><a name="note327" href="#note327">327)</a> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
21041 invoke the va_arg macro, the value of arg after the return is indeterminate.
21042 </small>
21045 <p><b>Synopsis</b>
21046 <p><!--para 1 -->
21047 <pre>
21051 int vfwscanf(FILE * restrict stream,
21052 const wchar_t * restrict format,
21053 va_list arg);
21054 </pre>
21055 <p><b>Description</b>
21056 <p><!--para 2 -->
21057 The vfwscanf function is equivalent to fwscanf, with the variable argument list
21058 replaced by arg, which shall have been initialized by the va_start macro (and
21059 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
21061 <p><b>Returns</b>
21062 <p><!--para 3 -->
21063 The vfwscanf function returns the value of the macro EOF if an input failure occurs
21064 before the first conversion (if any) has completed. Otherwise, the vfwscanf function
21065 returns the number of input items assigned, which can be fewer than provided for, or even
21066 zero, in the event of an early matching failure.
21069 <p><b>Synopsis</b>
21070 <p><!--para 1 -->
21071 <pre>
21074 int vswprintf(wchar_t * restrict s,
21075 size_t n,
21076 const wchar_t * restrict format,
21077 va_list arg);
21078 </pre>
21079 <p><b>Description</b>
21080 <p><!--para 2 -->
21081 The vswprintf function is equivalent to swprintf, with the variable argument list
21082 replaced by arg, which shall have been initialized by the va_start macro (and
21083 possibly subsequent va_arg calls). The vswprintf function does not invoke the
21085 <p><b>Returns</b>
21086 <p><!--para 3 -->
21087 The vswprintf function returns the number of wide characters written in the array, not
21088 counting the terminating null wide character, or a negative value if an encoding error
21089 occurred or if n or more wide characters were requested to be generated.
21090 <!--page 434 -->
21093 <p><b>Synopsis</b>
21094 <p><!--para 1 -->
21095 <pre>
21098 int vswscanf(const wchar_t * restrict s,
21099 const wchar_t * restrict format,
21100 va_list arg);
21101 </pre>
21102 <p><b>Description</b>
21103 <p><!--para 2 -->
21104 The vswscanf function is equivalent to swscanf, with the variable argument list
21105 replaced by arg, which shall have been initialized by the va_start macro (and
21106 possibly subsequent va_arg calls). The vswscanf function does not invoke the
21108 <p><b>Returns</b>
21109 <p><!--para 3 -->
21110 The vswscanf function returns the value of the macro EOF if an input failure occurs
21111 before the first conversion (if any) has completed. Otherwise, the vswscanf function
21112 returns the number of input items assigned, which can be fewer than provided for, or even
21113 zero, in the event of an early matching failure.
21116 <p><b>Synopsis</b>
21117 <p><!--para 1 -->
21118 <pre>
21121 int vwprintf(const wchar_t * restrict format,
21122 va_list arg);
21123 </pre>
21124 <p><b>Description</b>
21125 <p><!--para 2 -->
21126 The vwprintf function is equivalent to wprintf, with the variable argument list
21127 replaced by arg, which shall have been initialized by the va_start macro (and
21128 possibly subsequent va_arg calls). The vwprintf function does not invoke the
21130 <p><b>Returns</b>
21131 <p><!--para 3 -->
21132 The vwprintf function returns the number of wide characters transmitted, or a negative
21133 value if an output or encoding error occurred.
21134 <!--page 435 -->
21137 <p><b>Synopsis</b>
21138 <p><!--para 1 -->
21139 <pre>
21142 int vwscanf(const wchar_t * restrict format,
21143 va_list arg);
21144 </pre>
21145 <p><b>Description</b>
21146 <p><!--para 2 -->
21147 The vwscanf function is equivalent to wscanf, with the variable argument list
21148 replaced by arg, which shall have been initialized by the va_start macro (and
21149 possibly subsequent va_arg calls). The vwscanf function does not invoke the
21151 <p><b>Returns</b>
21152 <p><!--para 3 -->
21153 The vwscanf function returns the value of the macro EOF if an input failure occurs
21154 before the first conversion (if any) has completed. Otherwise, the vwscanf function
21155 returns the number of input items assigned, which can be fewer than provided for, or even
21156 zero, in the event of an early matching failure.
21159 <p><b>Synopsis</b>
21160 <p><!--para 1 -->
21161 <pre>
21163 int wprintf(const wchar_t * restrict format, ...);
21164 </pre>
21165 <p><b>Description</b>
21166 <p><!--para 2 -->
21167 The wprintf function is equivalent to fwprintf with the argument stdout
21168 interposed before the arguments to wprintf.
21169 <p><b>Returns</b>
21170 <p><!--para 3 -->
21171 The wprintf function returns the number of wide characters transmitted, or a negative
21172 value if an output or encoding error occurred.
21175 <p><b>Synopsis</b>
21176 <p><!--para 1 -->
21177 <pre>
21179 int wscanf(const wchar_t * restrict format, ...);
21180 </pre>
21181 <p><b>Description</b>
21182 <p><!--para 2 -->
21183 The wscanf function is equivalent to fwscanf with the argument stdin interposed
21184 before the arguments to wscanf.
21185 <!--page 436 -->
21186 <p><b>Returns</b>
21187 <p><!--para 3 -->
21188 The wscanf function returns the value of the macro EOF if an input failure occurs
21189 before the first conversion (if any) has completed. Otherwise, the wscanf function
21190 returns the number of input items assigned, which can be fewer than provided for, or even
21191 zero, in the event of an early matching failure.
21196 <p><b>Synopsis</b>
21197 <p><!--para 1 -->
21198 <pre>
21201 wint_t fgetwc(FILE *stream);
21202 </pre>
21203 <p><b>Description</b>
21204 <p><!--para 2 -->
21205 If the end-of-file indicator for the input stream pointed to by stream is not set and a
21206 next wide character is present, the fgetwc function obtains that wide character as a
21207 wchar_t converted to a wint_t and advances the associated file position indicator for
21208 the stream (if defined).
21209 <p><b>Returns</b>
21210 <p><!--para 3 -->
21211 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
21212 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
21213 the fgetwc function returns the next wide character from the input stream pointed to by
21214 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
21215 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
21216 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note328"><b>328)</b></a></sup>
21218 <p><b>Footnotes</b>
21219 <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.
21220 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
21221 </small>
21224 <p><b>Synopsis</b>
21225 <p><!--para 1 -->
21226 <pre>
21229 wchar_t *fgetws(wchar_t * restrict s,
21230 int n, FILE * restrict stream);
21231 </pre>
21232 <p><b>Description</b>
21233 <p><!--para 2 -->
21234 The fgetws function reads at most one less than the number of wide characters
21235 specified by n from the stream pointed to by stream into the array pointed to by s. No
21238 <!--page 437 -->
21239 additional wide characters are read after a new-line wide character (which is retained) or
21240 after end-of-file. A null wide character is written immediately after the last wide
21241 character read into the array.
21242 <p><b>Returns</b>
21243 <p><!--para 3 -->
21244 The fgetws function returns s if successful. If end-of-file is encountered and no
21245 characters have been read into the array, the contents of the array remain unchanged and a
21246 null pointer is returned. If a read or encoding error occurs during the operation, the array
21247 contents are indeterminate and a null pointer is returned.
21250 <p><b>Synopsis</b>
21251 <p><!--para 1 -->
21252 <pre>
21255 wint_t fputwc(wchar_t c, FILE *stream);
21256 </pre>
21257 <p><b>Description</b>
21258 <p><!--para 2 -->
21259 The fputwc function writes the wide character specified by c to the output stream
21260 pointed to by stream, at the position indicated by the associated file position indicator
21261 for the stream (if defined), and advances the indicator appropriately. If the file cannot
21262 support positioning requests, or if the stream was opened with append mode, the
21263 character is appended to the output stream.
21264 <p><b>Returns</b>
21265 <p><!--para 3 -->
21266 The fputwc function returns the wide character written. If a write error occurs, the
21267 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
21268 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
21271 <p><b>Synopsis</b>
21272 <p><!--para 1 -->
21273 <pre>
21276 int fputws(const wchar_t * restrict s,
21277 FILE * restrict stream);
21278 </pre>
21279 <p><b>Description</b>
21280 <p><!--para 2 -->
21281 The fputws function writes the wide string pointed to by s to the stream pointed to by
21282 stream. The terminating null wide character is not written.
21283 <p><b>Returns</b>
21284 <p><!--para 3 -->
21285 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
21286 returns a nonnegative value.
21287 <!--page 438 -->
21290 <p><b>Synopsis</b>
21291 <p><!--para 1 -->
21292 <pre>
21295 int fwide(FILE *stream, int mode);
21296 </pre>
21297 <p><b>Description</b>
21298 <p><!--para 2 -->
21299 The fwide function determines the orientation of the stream pointed to by stream. If
21300 mode is greater than zero, the function first attempts to make the stream wide oriented. If
21301 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note329"><b>329)</b></a></sup>
21302 Otherwise, mode is zero and the function does not alter the orientation of the stream.
21303 <p><b>Returns</b>
21304 <p><!--para 3 -->
21305 The fwide function returns a value greater than zero if, after the call, the stream has
21306 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
21307 stream has no orientation.
21309 <p><b>Footnotes</b>
21310 <p><small><a name="note329" href="#note329">329)</a> If the orientation of the stream has already been determined, fwide does not change it.
21311 </small>
21314 <p><b>Synopsis</b>
21315 <p><!--para 1 -->
21316 <pre>
21319 wint_t getwc(FILE *stream);
21320 </pre>
21321 <p><b>Description</b>
21322 <p><!--para 2 -->
21323 The getwc function is equivalent to fgetwc, except that if it is implemented as a
21324 macro, it may evaluate stream more than once, so the argument should never be an
21325 expression with side effects.
21326 <p><b>Returns</b>
21327 <p><!--para 3 -->
21328 The getwc function returns the next wide character from the input stream pointed to by
21329 stream, or WEOF.
21332 <p><b>Synopsis</b>
21333 <p><!--para 1 -->
21334 <pre>
21336 wint_t getwchar(void);
21337 </pre>
21342 <!--page 439 -->
21343 <p><b>Description</b>
21344 <p><!--para 2 -->
21345 The getwchar function is equivalent to getwc with the argument stdin.
21346 <p><b>Returns</b>
21347 <p><!--para 3 -->
21348 The getwchar function returns the next wide character from the input stream pointed to
21349 by stdin, or WEOF.
21352 <p><b>Synopsis</b>
21353 <p><!--para 1 -->
21354 <pre>
21357 wint_t putwc(wchar_t c, FILE *stream);
21358 </pre>
21359 <p><b>Description</b>
21360 <p><!--para 2 -->
21361 The putwc function is equivalent to fputwc, except that if it is implemented as a
21362 macro, it may evaluate stream more than once, so that argument should never be an
21363 expression with side effects.
21364 <p><b>Returns</b>
21365 <p><!--para 3 -->
21366 The putwc function returns the wide character written, or WEOF.
21369 <p><b>Synopsis</b>
21370 <p><!--para 1 -->
21371 <pre>
21373 wint_t putwchar(wchar_t c);
21374 </pre>
21375 <p><b>Description</b>
21376 <p><!--para 2 -->
21377 The putwchar function is equivalent to putwc with the second argument stdout.
21378 <p><b>Returns</b>
21379 <p><!--para 3 -->
21380 The putwchar function returns the character written, or WEOF.
21383 <p><b>Synopsis</b>
21384 <p><!--para 1 -->
21385 <pre>
21388 wint_t ungetwc(wint_t c, FILE *stream);
21389 </pre>
21390 <p><b>Description</b>
21391 <p><!--para 2 -->
21392 The ungetwc function pushes the wide character specified by c back onto the input
21393 stream pointed to by stream. Pushed-back wide characters will be returned by
21394 subsequent reads on that stream in the reverse order of their pushing. A successful
21395 <!--page 440 -->
21396 intervening call (with the stream pointed to by stream) to a file positioning function
21397 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
21398 stream. The external storage corresponding to the stream is unchanged.
21399 <p><!--para 3 -->
21400 One wide character of pushback is guaranteed, even if the call to the ungetwc function
21401 follows just after a call to a formatted wide character input function fwscanf,
21402 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
21403 on the same stream without an intervening read or file positioning operation on that
21404 stream, the operation may fail.
21405 <p><!--para 4 -->
21406 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
21407 unchanged.
21408 <p><!--para 5 -->
21409 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
21410 The value of the file position indicator for the stream after reading or discarding all
21411 pushed-back wide characters is the same as it was before the wide characters were pushed
21412 back. For a text or binary stream, the value of its file position indicator after a successful
21413 call to the ungetwc function is unspecified until all pushed-back wide characters are
21414 read or discarded.
21415 <p><b>Returns</b>
21416 <p><!--para 6 -->
21417 The ungetwc function returns the wide character pushed back, or WEOF if the operation
21418 fails.
21421 <p><!--para 1 -->
21422 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide string
21423 manipulation. Various methods are used for determining the lengths of the arrays, but in
21424 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
21425 array. If an array is accessed beyond the end of an object, the behavior is undefined.
21426 <p><!--para 2 -->
21427 Where an argument declared as size_t n determines the length of the array for a
21428 function, n can have the value zero on a call to that function. Unless explicitly stated
21429 otherwise in the description of a particular function in this subclause, pointer arguments
21430 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
21431 function that locates a wide character finds no occurrence, a function that compares two
21432 wide character sequences returns zero, and a function that copies wide characters copies
21433 zero wide characters.
21434 <!--page 441 -->
21436 <h5><a name="7.28.4.1" href="#7.28.4.1">7.28.4.1 Wide string numeric conversion functions</a></h5>
21438 <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>
21439 <p><b>Synopsis</b>
21440 <p><!--para 1 -->
21441 <pre>
21443 double wcstod(const wchar_t * restrict nptr,
21444 wchar_t ** restrict endptr);
21445 float wcstof(const wchar_t * restrict nptr,
21446 wchar_t ** restrict endptr);
21447 long double wcstold(const wchar_t * restrict nptr,
21448 wchar_t ** restrict endptr);
21449 </pre>
21450 <p><b>Description</b>
21451 <p><!--para 2 -->
21452 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
21453 string pointed to by nptr to double, float, and long double representation,
21454 respectively. First, they decompose the input string into three parts: an initial, possibly
21455 empty, sequence of white-space wide characters (as specified by the iswspace
21456 function), a subject sequence resembling a floating-point constant or representing an
21457 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
21458 including the terminating null wide character of the input wide string. Then, they attempt
21459 to convert the subject sequence to a floating-point number, and return the result.
21460 <p><!--para 3 -->
21461 The expected form of the subject sequence is an optional plus or minus sign, then one of
21462 the following:
21463 <ul>
21464 <li> a nonempty sequence of decimal digits optionally containing a decimal-point wide
21465 character, then an optional exponent part as defined for the corresponding single-byte
21467 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
21468 decimal-point wide character, then an optional binary exponent part as defined in
21470 <li> INF or INFINITY, or any other wide string equivalent except for case
21471 <li> NAN or NAN(n-wchar-sequence<sub>opt</sub>), or any other wide string equivalent except for
21472 case in the NAN part, where:
21473 <pre>
21474 n-wchar-sequence:
21475 digit
21476 nondigit
21477 n-wchar-sequence digit
21478 n-wchar-sequence nondigit
21479 </pre>
21480 </ul>
21481 The subject sequence is defined as the longest initial subsequence of the input wide
21482 string, starting with the first non-white-space wide character, that is of the expected form.
21483 <!--page 442 -->
21484 The subject sequence contains no wide characters if the input wide string is not of the
21485 expected form.
21486 <p><!--para 4 -->
21487 If the subject sequence has the expected form for a floating-point number, the sequence of
21488 wide characters starting with the first digit or the decimal-point wide character
21489 (whichever occurs first) is interpreted as a floating constant according to the rules of
21490 <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
21491 if neither an exponent part nor a decimal-point wide character appears in a decimal
21492 floating point number, or if a binary exponent part does not appear in a hexadecimal
21493 floating point number, an exponent part of the appropriate type with value zero is
21494 assumed to follow the last digit in the string. If the subject sequence begins with a minus
21495 sign, the sequence is interpreted as negated.<sup><a href="#note330"><b>330)</b></a></sup> A wide character sequence INF or
21496 INFINITY is interpreted as an infinity, if representable in the return type, else like a
21497 floating constant that is too large for the range of the return type. A wide character
21498 sequence NAN or NAN(n-wchar-sequence<sub>opt</sub>) is interpreted as a quiet NaN, if supported
21499 in the return type, else like a subject sequence part that does not have the expected form;
21500 the meaning of the n-wchar sequences is implementation-defined.<sup><a href="#note331"><b>331)</b></a></sup> A pointer to the
21501 final wide string is stored in the object pointed to by endptr, provided that endptr is
21502 not a null pointer.
21503 <p><!--para 5 -->
21504 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
21505 value resulting from the conversion is correctly rounded.
21506 <p><!--para 6 -->
21508 accepted.
21509 <p><!--para 7 -->
21510 If the subject sequence is empty or does not have the expected form, no conversion is
21511 performed; the value of nptr is stored in the object pointed to by endptr, provided
21512 that endptr is not a null pointer.
21513 <p><b>Recommended practice</b>
21514 <p><!--para 8 -->
21515 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
21516 the result is not exactly representable, the result should be one of the two numbers in the
21517 appropriate internal format that are adjacent to the hexadecimal floating source value,
21518 with the extra stipulation that the error should have a correct sign for the current rounding
21519 direction.
21523 <!--page 443 -->
21524 <p><!--para 9 -->
21525 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
21526 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
21527 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
21528 consider the two bounding, adjacent decimal strings L and U, both having
21529 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
21530 The result should be one of the (equal or adjacent) values that would be obtained by
21531 correctly rounding L and U according to the current rounding direction, with the extra
21532 stipulation that the error with respect to D should have a correct sign for the current
21534 <p><b>Returns</b>
21535 <p><!--para 10 -->
21536 The functions return the converted value, if any. If no conversion could be performed,
21537 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
21538 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
21539 return type and sign of the value), and the value of the macro ERANGE is stored in
21540 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
21541 no greater than the smallest normalized positive number in the return type; whether
21542 errno acquires the value ERANGE is implementation-defined.
21547 <!--page 444 -->
21549 <p><b>Footnotes</b>
21550 <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
21551 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
21552 methods may yield different results if rounding is toward positive or negative infinity. In either case,
21553 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
21554 </small>
21555 <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
21556 the NaN's significand.
21557 </small>
21558 <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
21559 to the same internal floating value, but if not will round to adjacent values.
21560 </small>
21562 <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>
21563 <p><b>Synopsis</b>
21564 <p><!--para 1 -->
21565 <pre>
21567 long int wcstol(
21568 const wchar_t * restrict nptr,
21569 wchar_t ** restrict endptr,
21570 int base);
21571 long long int wcstoll(
21572 const wchar_t * restrict nptr,
21573 wchar_t ** restrict endptr,
21574 int base);
21575 unsigned long int wcstoul(
21576 const wchar_t * restrict nptr,
21577 wchar_t ** restrict endptr,
21578 int base);
21579 unsigned long long int wcstoull(
21580 const wchar_t * restrict nptr,
21581 wchar_t ** restrict endptr,
21582 int base);
21583 </pre>
21584 <p><b>Description</b>
21585 <p><!--para 2 -->
21586 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
21587 portion of the wide string pointed to by nptr to long int, long long int,
21588 unsigned long int, and unsigned long long int representation,
21589 respectively. First, they decompose the input string into three parts: an initial, possibly
21590 empty, sequence of white-space wide characters (as specified by the iswspace
21591 function), a subject sequence resembling an integer represented in some radix determined
21592 by the value of base, and a final wide string of one or more unrecognized wide
21593 characters, including the terminating null wide character of the input wide string. Then,
21594 they attempt to convert the subject sequence to an integer, and return the result.
21595 <p><!--para 3 -->
21596 If the value of base is zero, the expected form of the subject sequence is that of an
21597 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
21598 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
21599 value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
21600 is a sequence of letters and digits representing an integer with the radix specified by
21601 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
21602 The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
21603 letters and digits whose ascribed values are less than that of base are permitted. If the
21604 value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
21605 of letters and digits, following the sign if present.
21606 <!--page 445 -->
21607 <p><!--para 4 -->
21608 The subject sequence is defined as the longest initial subsequence of the input wide
21609 string, starting with the first non-white-space wide character, that is of the expected form.
21610 The subject sequence contains no wide characters if the input wide string is empty or
21611 consists entirely of white space, or if the first non-white-space wide character is other
21612 than a sign or a permissible letter or digit.
21613 <p><!--para 5 -->
21614 If the subject sequence has the expected form and the value of base is zero, the sequence
21615 of wide characters starting with the first digit is interpreted as an integer constant
21616 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
21617 value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
21618 letter its value as given above. If the subject sequence begins with a minus sign, the value
21619 resulting from the conversion is negated (in the return type). A pointer to the final wide
21620 string is stored in the object pointed to by endptr, provided that endptr is not a null
21621 pointer.
21622 <p><!--para 6 -->
21624 accepted.
21625 <p><!--para 7 -->
21626 If the subject sequence is empty or does not have the expected form, no conversion is
21627 performed; the value of nptr is stored in the object pointed to by endptr, provided
21628 that endptr is not a null pointer.
21629 <p><b>Returns</b>
21630 <p><!--para 8 -->
21631 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
21632 value, if any. If no conversion could be performed, zero is returned. If the correct value
21633 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
21634 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
21635 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
21640 <p><b>Synopsis</b>
21641 <p><!--para 1 -->
21642 <pre>
21644 wchar_t *wcscpy(wchar_t * restrict s1,
21645 const wchar_t * restrict s2);
21646 </pre>
21647 <p><b>Description</b>
21648 <p><!--para 2 -->
21649 The wcscpy function copies the wide string pointed to by s2 (including the terminating
21650 null wide character) into the array pointed to by s1.
21651 <p><b>Returns</b>
21652 <p><!--para 3 -->
21653 The wcscpy function returns the value of s1.
21654 <!--page 446 -->
21657 <p><b>Synopsis</b>
21658 <p><!--para 1 -->
21659 <pre>
21661 wchar_t *wcsncpy(wchar_t * restrict s1,
21662 const wchar_t * restrict s2,
21663 size_t n);
21664 </pre>
21665 <p><b>Description</b>
21666 <p><!--para 2 -->
21667 The wcsncpy function copies not more than n wide characters (those that follow a null
21668 wide character are not copied) from the array pointed to by s2 to the array pointed to by
21670 <p><!--para 3 -->
21671 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
21672 wide characters are appended to the copy in the array pointed to by s1, until n wide
21673 characters in all have been written.
21674 <p><b>Returns</b>
21675 <p><!--para 4 -->
21676 The wcsncpy function returns the value of s1.
21678 <p><b>Footnotes</b>
21679 <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
21680 result will not be null-terminated.
21681 </small>
21684 <p><b>Synopsis</b>
21685 <p><!--para 1 -->
21686 <pre>
21688 wchar_t *wmemcpy(wchar_t * restrict s1,
21689 const wchar_t * restrict s2,
21690 size_t n);
21691 </pre>
21692 <p><b>Description</b>
21693 <p><!--para 2 -->
21694 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
21695 object pointed to by s1.
21696 <p><b>Returns</b>
21697 <p><!--para 3 -->
21698 The wmemcpy function returns the value of s1.
21703 <!--page 447 -->
21706 <p><b>Synopsis</b>
21707 <p><!--para 1 -->
21708 <pre>
21710 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
21711 size_t n);
21712 </pre>
21713 <p><b>Description</b>
21714 <p><!--para 2 -->
21715 The wmemmove function copies n wide characters from the object pointed to by s2 to
21716 the object pointed to by s1. Copying takes place as if the n wide characters from the
21717 object pointed to by s2 are first copied into a temporary array of n wide characters that
21718 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
21719 the temporary array are copied into the object pointed to by s1.
21720 <p><b>Returns</b>
21721 <p><!--para 3 -->
21722 The wmemmove function returns the value of s1.
21727 <p><b>Synopsis</b>
21728 <p><!--para 1 -->
21729 <pre>
21731 wchar_t *wcscat(wchar_t * restrict s1,
21732 const wchar_t * restrict s2);
21733 </pre>
21734 <p><b>Description</b>
21735 <p><!--para 2 -->
21736 The wcscat function appends a copy of the wide string pointed to by s2 (including the
21737 terminating null wide character) to the end of the wide string pointed to by s1. The initial
21738 wide character of s2 overwrites the null wide character at the end of s1.
21739 <p><b>Returns</b>
21740 <p><!--para 3 -->
21741 The wcscat function returns the value of s1.
21744 <p><b>Synopsis</b>
21745 <p><!--para 1 -->
21746 <pre>
21748 wchar_t *wcsncat(wchar_t * restrict s1,
21749 const wchar_t * restrict s2,
21750 size_t n);
21751 </pre>
21752 <p><b>Description</b>
21753 <p><!--para 2 -->
21754 The wcsncat function appends not more than n wide characters (a null wide character
21755 and those that follow it are not appended) from the array pointed to by s2 to the end of
21756 <!--page 448 -->
21757 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
21758 wide character at the end of s1. A terminating null wide character is always appended to
21760 <p><b>Returns</b>
21761 <p><!--para 3 -->
21762 The wcsncat function returns the value of s1.
21764 <p><b>Footnotes</b>
21765 <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
21766 wcslen(s1)+n+1.
21767 </small>
21770 <p><!--para 1 -->
21771 Unless explicitly stated otherwise, the functions described in this subclause order two
21772 wide characters the same way as two integers of the underlying integer type designated
21773 by wchar_t.
21776 <p><b>Synopsis</b>
21777 <p><!--para 1 -->
21778 <pre>
21780 int wcscmp(const wchar_t *s1, const wchar_t *s2);
21781 </pre>
21782 <p><b>Description</b>
21783 <p><!--para 2 -->
21784 The wcscmp function compares the wide string pointed to by s1 to the wide string
21785 pointed to by s2.
21786 <p><b>Returns</b>
21787 <p><!--para 3 -->
21788 The wcscmp function returns an integer greater than, equal to, or less than zero,
21789 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
21790 wide string pointed to by s2.
21793 <p><b>Synopsis</b>
21794 <p><!--para 1 -->
21795 <pre>
21797 int wcscoll(const wchar_t *s1, const wchar_t *s2);
21798 </pre>
21799 <p><b>Description</b>
21800 <p><!--para 2 -->
21801 The wcscoll function compares the wide string pointed to by s1 to the wide string
21802 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
21803 current locale.
21804 <p><b>Returns</b>
21805 <p><!--para 3 -->
21806 The wcscoll function returns an integer greater than, equal to, or less than zero,
21807 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
21810 <!--page 449 -->
21811 wide string pointed to by s2 when both are interpreted as appropriate to the current
21812 locale.
21815 <p><b>Synopsis</b>
21816 <p><!--para 1 -->
21817 <pre>
21819 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
21820 size_t n);
21821 </pre>
21822 <p><b>Description</b>
21823 <p><!--para 2 -->
21824 The wcsncmp function compares not more than n wide characters (those that follow a
21825 null wide character are not compared) from the array pointed to by s1 to the array
21826 pointed to by s2.
21827 <p><b>Returns</b>
21828 <p><!--para 3 -->
21829 The wcsncmp function returns an integer greater than, equal to, or less than zero,
21830 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
21831 to, or less than the possibly null-terminated array pointed to by s2.
21834 <p><b>Synopsis</b>
21835 <p><!--para 1 -->
21836 <pre>
21838 size_t wcsxfrm(wchar_t * restrict s1,
21839 const wchar_t * restrict s2,
21840 size_t n);
21841 </pre>
21842 <p><b>Description</b>
21843 <p><!--para 2 -->
21844 The wcsxfrm function transforms the wide string pointed to by s2 and places the
21845 resulting wide string into the array pointed to by s1. The transformation is such that if
21846 the wcscmp function is applied to two transformed wide strings, it returns a value greater
21847 than, equal to, or less than zero, corresponding to the result of the wcscoll function
21848 applied to the same two original wide strings. No more than n wide characters are placed
21849 into the resulting array pointed to by s1, including the terminating null wide character. If
21850 n is zero, s1 is permitted to be a null pointer.
21851 <p><b>Returns</b>
21852 <p><!--para 3 -->
21853 The wcsxfrm function returns the length of the transformed wide string (not including
21854 the terminating null wide character). If the value returned is n or greater, the contents of
21855 the array pointed to by s1 are indeterminate.
21856 <p><!--para 4 -->
21857 EXAMPLE The value of the following expression is the length of the array needed to hold the
21858 transformation of the wide string pointed to by s:
21859 <!--page 450 -->
21860 <pre>
21861 1 + wcsxfrm(NULL, s, 0)
21862 </pre>
21866 <p><b>Synopsis</b>
21867 <p><!--para 1 -->
21868 <pre>
21870 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
21871 size_t n);
21872 </pre>
21873 <p><b>Description</b>
21874 <p><!--para 2 -->
21875 The wmemcmp function compares the first n wide characters of the object pointed to by
21876 s1 to the first n wide characters of the object pointed to by s2.
21877 <p><b>Returns</b>
21878 <p><!--para 3 -->
21879 The wmemcmp function returns an integer greater than, equal to, or less than zero,
21880 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
21881 pointed to by s2.
21886 <p><b>Synopsis</b>
21887 <p><!--para 1 -->
21888 <pre>
21890 wchar_t *wcschr(const wchar_t *s, wchar_t c);
21891 </pre>
21892 <p><b>Description</b>
21893 <p><!--para 2 -->
21894 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
21895 The terminating null wide character is considered to be part of the wide string.
21896 <p><b>Returns</b>
21897 <p><!--para 3 -->
21898 The wcschr function returns a pointer to the located wide character, or a null pointer if
21899 the wide character does not occur in the wide string.
21902 <p><b>Synopsis</b>
21903 <p><!--para 1 -->
21904 <pre>
21906 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
21907 </pre>
21908 <p><b>Description</b>
21909 <p><!--para 2 -->
21910 The wcscspn function computes the length of the maximum initial segment of the wide
21911 string pointed to by s1 which consists entirely of wide characters not from the wide
21912 string pointed to by s2.
21913 <!--page 451 -->
21914 <p><b>Returns</b>
21915 <p><!--para 3 -->
21916 The wcscspn function returns the length of the segment.
21919 <p><b>Synopsis</b>
21920 <p><!--para 1 -->
21921 <pre>
21923 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
21924 </pre>
21925 <p><b>Description</b>
21926 <p><!--para 2 -->
21927 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
21928 any wide character from the wide string pointed to by s2.
21929 <p><b>Returns</b>
21930 <p><!--para 3 -->
21931 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
21932 no wide character from s2 occurs in s1.
21935 <p><b>Synopsis</b>
21936 <p><!--para 1 -->
21937 <pre>
21939 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
21940 </pre>
21941 <p><b>Description</b>
21942 <p><!--para 2 -->
21943 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
21944 s. The terminating null wide character is considered to be part of the wide string.
21945 <p><b>Returns</b>
21946 <p><!--para 3 -->
21947 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
21948 not occur in the wide string.
21951 <p><b>Synopsis</b>
21952 <p><!--para 1 -->
21953 <pre>
21955 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
21956 </pre>
21957 <p><b>Description</b>
21958 <p><!--para 2 -->
21959 The wcsspn function computes the length of the maximum initial segment of the wide
21960 string pointed to by s1 which consists entirely of wide characters from the wide string
21961 pointed to by s2.
21962 <p><b>Returns</b>
21963 <p><!--para 3 -->
21964 The wcsspn function returns the length of the segment.
21965 <!--page 452 -->
21968 <p><b>Synopsis</b>
21969 <p><!--para 1 -->
21970 <pre>
21972 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
21973 </pre>
21974 <p><b>Description</b>
21975 <p><!--para 2 -->
21976 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
21977 the sequence of wide characters (excluding the terminating null wide character) in the
21978 wide string pointed to by s2.
21979 <p><b>Returns</b>
21980 <p><!--para 3 -->
21981 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
21982 wide string is not found. If s2 points to a wide string with zero length, the function
21983 returns s1.
21986 <p><b>Synopsis</b>
21987 <p><!--para 1 -->
21988 <pre>
21990 wchar_t *wcstok(wchar_t * restrict s1,
21991 const wchar_t * restrict s2,
21992 wchar_t ** restrict ptr);
21993 </pre>
21994 <p><b>Description</b>
21995 <p><!--para 2 -->
21996 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
21997 a sequence of tokens, each of which is delimited by a wide character from the wide string
21998 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
21999 which the wcstok function stores information necessary for it to continue scanning the
22000 same wide string.
22001 <p><!--para 3 -->
22002 The first call in a sequence has a non-null first argument and stores an initial value in the
22003 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
22004 the object pointed to by ptr is required to have the value stored by the previous call in
22005 the sequence, which is then updated. The separator wide string pointed to by s2 may be
22006 different from call to call.
22007 <p><!--para 4 -->
22008 The first call in the sequence searches the wide string pointed to by s1 for the first wide
22009 character that is not contained in the current separator wide string pointed to by s2. If no
22010 such wide character is found, then there are no tokens in the wide string pointed to by s1
22011 and the wcstok function returns a null pointer. If such a wide character is found, it is
22012 the start of the first token.
22013 <p><!--para 5 -->
22014 The wcstok function then searches from there for a wide character that is contained in
22015 the current separator wide string. If no such wide character is found, the current token
22016 <!--page 453 -->
22017 extends to the end of the wide string pointed to by s1, and subsequent searches in the
22018 same wide string for a token return a null pointer. If such a wide character is found, it is
22019 overwritten by a null wide character, which terminates the current token.
22020 <p><!--para 6 -->
22021 In all cases, the wcstok function stores sufficient information in the pointer pointed to
22022 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
22023 value for ptr, shall start searching just past the element overwritten by a null wide
22024 character (if any).
22025 <p><b>Returns</b>
22026 <p><!--para 7 -->
22027 The wcstok function returns a pointer to the first wide character of a token, or a null
22028 pointer if there is no token.
22029 <p><!--para 8 -->
22030 EXAMPLE
22031 <pre>
22035 wchar_t *t, *ptr1, *ptr2;
22041 </pre>
22045 <p><b>Synopsis</b>
22046 <p><!--para 1 -->
22047 <pre>
22049 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
22050 size_t n);
22051 </pre>
22052 <p><b>Description</b>
22053 <p><!--para 2 -->
22054 The wmemchr function locates the first occurrence of c in the initial n wide characters of
22055 the object pointed to by s.
22056 <p><b>Returns</b>
22057 <p><!--para 3 -->
22058 The wmemchr function returns a pointer to the located wide character, or a null pointer if
22059 the wide character does not occur in the object.
22060 <!--page 454 -->
22065 <p><b>Synopsis</b>
22066 <p><!--para 1 -->
22067 <pre>
22069 size_t wcslen(const wchar_t *s);
22070 </pre>
22071 <p><b>Description</b>
22072 <p><!--para 2 -->
22073 The wcslen function computes the length of the wide string pointed to by s.
22074 <p><b>Returns</b>
22075 <p><!--para 3 -->
22076 The wcslen function returns the number of wide characters that precede the terminating
22077 null wide character.
22080 <p><b>Synopsis</b>
22081 <p><!--para 1 -->
22082 <pre>
22084 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
22085 </pre>
22086 <p><b>Description</b>
22087 <p><!--para 2 -->
22088 The wmemset function copies the value of c into each of the first n wide characters of
22089 the object pointed to by s.
22090 <p><b>Returns</b>
22091 <p><!--para 3 -->
22092 The wmemset function returns the value of s.
22097 <p><b>Synopsis</b>
22098 <p><!--para 1 -->
22099 <pre>
22102 size_t wcsftime(wchar_t * restrict s,
22103 size_t maxsize,
22104 const wchar_t * restrict format,
22105 const struct tm * restrict timeptr);
22106 </pre>
22107 <p><b>Description</b>
22108 <p><!--para 2 -->
22109 The wcsftime function is equivalent to the strftime function, except that:
22110 <ul>
22111 <li> The argument s points to the initial element of an array of wide characters into which
22112 the generated output is to be placed.
22113 <!--page 455 -->
22114 <li> The argument maxsize indicates the limiting number of wide characters.
22115 <li> The argument format is a wide string and the conversion specifiers are replaced by
22116 corresponding sequences of wide characters.
22117 <li> The return value indicates the number of wide characters.
22118 </ul>
22119 <p><b>Returns</b>
22120 <p><!--para 3 -->
22121 If the total number of resulting wide characters including the terminating null wide
22122 character is not more than maxsize, the wcsftime function returns the number of
22123 wide characters placed into the array pointed to by s not including the terminating null
22124 wide character. Otherwise, zero is returned and the contents of the array are
22125 indeterminate.
22127 <h4><a name="7.28.6" href="#7.28.6">7.28.6 Extended multibyte/wide character conversion utilities</a></h4>
22128 <p><!--para 1 -->
22129 The header <a href="#7.28"><wchar.h></a> declares an extended set of functions useful for conversion
22130 between multibyte characters and wide characters.
22131 <p><!--para 2 -->
22132 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.28.6.3">7.28.6.3</a> and
22133 <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
22134 to describe the current conversion state from a particular multibyte character sequence to
22135 a wide character sequence (or the reverse) under the rules of a particular setting for the
22136 LC_CTYPE category of the current locale.
22137 <p><!--para 3 -->
22138 The initial conversion state corresponds, for a conversion in either direction, to the
22139 beginning of a new multibyte character in the initial shift state. A zero-valued
22140 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
22141 valued mbstate_t object can be used to initiate conversion involving any multibyte
22142 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
22143 been altered by any of the functions described in this subclause, and is then used with a
22144 different multibyte character sequence, or in the other conversion direction, or with a
22145 different LC_CTYPE category setting than on earlier function calls, the behavior is
22147 <p><!--para 4 -->
22148 On entry, each function takes the described conversion state (either internal or pointed to
22149 by an argument) as current. The conversion state described by the referenced object is
22150 altered as needed to track the shift state, and the position within a multibyte character, for
22151 the associated multibyte character sequence.
22156 <!--page 456 -->
22158 <p><b>Footnotes</b>
22159 <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
22160 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
22161 character string.
22162 </small>
22164 <h5><a name="7.28.6.1" href="#7.28.6.1">7.28.6.1 Single-byte/wide character conversion functions</a></h5>
22167 <p><b>Synopsis</b>
22168 <p><!--para 1 -->
22169 <pre>
22171 wint_t btowc(int c);
22172 </pre>
22173 <p><b>Description</b>
22174 <p><!--para 2 -->
22175 The btowc function determines whether c constitutes a valid single-byte character in the
22176 initial shift state.
22177 <p><b>Returns</b>
22178 <p><!--para 3 -->
22179 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
22180 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
22181 returns the wide character representation of that character.
22184 <p><b>Synopsis</b>
22185 <p><!--para 1 -->
22186 <pre>
22188 int wctob(wint_t c);
22189 </pre>
22190 <p><b>Description</b>
22191 <p><!--para 2 -->
22192 The wctob function determines whether c corresponds to a member of the extended
22193 character set whose multibyte character representation is a single byte when in the initial
22194 shift state.
22195 <p><b>Returns</b>
22196 <p><!--para 3 -->
22197 The wctob function returns EOF if c does not correspond to a multibyte character with
22198 length one in the initial shift state. Otherwise, it returns the single-byte representation of
22199 that character as an unsigned char converted to an int.
22204 <p><b>Synopsis</b>
22205 <p><!--para 1 -->
22206 <pre>
22208 int mbsinit(const mbstate_t *ps);
22209 </pre>
22210 <p><b>Description</b>
22211 <p><!--para 2 -->
22212 If ps is not a null pointer, the mbsinit function determines whether the referenced
22213 mbstate_t object describes an initial conversion state.
22214 <!--page 457 -->
22215 <p><b>Returns</b>
22216 <p><!--para 3 -->
22217 The mbsinit function returns nonzero if ps is a null pointer or if the referenced object
22218 describes an initial conversion state; otherwise, it returns zero.
22220 <h5><a name="7.28.6.3" href="#7.28.6.3">7.28.6.3 Restartable multibyte/wide character conversion functions</a></h5>
22221 <p><!--para 1 -->
22222 These functions differ from the corresponding multibyte character functions of <a href="#7.22.7">7.22.7</a>
22223 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
22224 pointer to mbstate_t that points to an object that can completely describe the current
22225 conversion state of the associated multibyte character sequence. If ps is a null pointer,
22226 each function uses its own internal mbstate_t object instead, which is initialized at
22227 program startup to the initial conversion state; the functions are not required to avoid data
22228 races in this case. The implementation behaves as if no library function calls these
22229 functions with a null pointer for ps.
22230 <p><!--para 2 -->
22231 Also unlike their corresponding functions, the return value does not represent whether the
22232 encoding is state-dependent.
22235 <p><b>Synopsis</b>
22236 <p><!--para 1 -->
22237 <pre>
22239 size_t mbrlen(const char * restrict s,
22240 size_t n,
22241 mbstate_t * restrict ps);
22242 </pre>
22243 <p><b>Description</b>
22244 <p><!--para 2 -->
22245 The mbrlen function is equivalent to the call:
22246 <pre>
22247 mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)
22248 </pre>
22249 where internal is the mbstate_t object for the mbrlen function, except that the
22250 expression designated by ps is evaluated only once.
22251 <p><b>Returns</b>
22252 <p><!--para 3 -->
22253 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
22254 or (size_t)(-1).
22256 <!--page 458 -->
22259 <p><b>Synopsis</b>
22260 <p><!--para 1 -->
22261 <pre>
22263 size_t mbrtowc(wchar_t * restrict pwc,
22264 const char * restrict s,
22265 size_t n,
22266 mbstate_t * restrict ps);
22267 </pre>
22268 <p><b>Description</b>
22269 <p><!--para 2 -->
22270 If s is a null pointer, the mbrtowc function is equivalent to the call:
22271 <pre>
22273 </pre>
22274 In this case, the values of the parameters pwc and n are ignored.
22275 <p><!--para 3 -->
22276 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
22277 the byte pointed to by s to determine the number of bytes needed to complete the next
22278 multibyte character (including any shift sequences). If the function determines that the
22279 next multibyte character is complete and valid, it determines the value of the
22280 corresponding wide character and then, if pwc is not a null pointer, stores that value in
22281 the object pointed to by pwc. If the corresponding wide character is the null wide
22282 character, the resulting state described is the initial conversion state.
22283 <p><b>Returns</b>
22284 <p><!--para 4 -->
22285 The mbrtowc function returns the first of the following that applies (given the current
22286 conversion state):
22287 0 if the next n or fewer bytes complete the multibyte character that
22288 <pre>
22289 corresponds to the null wide character (which is the value stored).
22290 </pre>
22291 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
22292 <pre>
22293 character (which is the value stored); the value returned is the number
22294 of bytes that complete the multibyte character.
22295 </pre>
22296 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
22297 <pre>
22298 multibyte character, and all n bytes have been processed (no value is
22300 </pre>
22301 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
22302 <pre>
22303 do not contribute to a complete and valid multibyte character (no
22304 value is stored); the value of the macro EILSEQ is stored in errno,
22305 and the conversion state is unspecified.
22306 </pre>
22308 <!--page 459 -->
22310 <p><b>Footnotes</b>
22311 <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
22312 sequence of redundant shift sequences (for implementations with state-dependent encodings).
22313 </small>
22316 <p><b>Synopsis</b>
22317 <p><!--para 1 -->
22318 <pre>
22320 size_t wcrtomb(char * restrict s,
22321 wchar_t wc,
22322 mbstate_t * restrict ps);
22323 </pre>
22324 <p><b>Description</b>
22325 <p><!--para 2 -->
22326 If s is a null pointer, the wcrtomb function is equivalent to the call
22327 <pre>
22328 wcrtomb(buf, L'\0', ps)
22329 </pre>
22330 where buf is an internal buffer.
22331 <p><!--para 3 -->
22332 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
22333 to represent the multibyte character that corresponds to the wide character given by wc
22334 (including any shift sequences), and stores the multibyte character representation in the
22335 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
22336 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
22337 to restore the initial shift state; the resulting state described is the initial conversion state.
22338 <p><b>Returns</b>
22339 <p><!--para 4 -->
22340 The wcrtomb function returns the number of bytes stored in the array object (including
22341 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
22342 the function stores the value of the macro EILSEQ in errno and returns
22343 (size_t)(-1); the conversion state is unspecified.
22345 <h5><a name="7.28.6.4" href="#7.28.6.4">7.28.6.4 Restartable multibyte/wide string conversion functions</a></h5>
22346 <p><!--para 1 -->
22347 These functions differ from the corresponding multibyte string functions of <a href="#7.22.8">7.22.8</a>
22348 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
22349 mbstate_t that points to an object that can completely describe the current conversion
22350 state of the associated multibyte character sequence. If ps is a null pointer, each function
22351 uses its own internal mbstate_t object instead, which is initialized at program startup
22352 to the initial conversion state; the functions are not required to avoid data races in this
22353 case. The implementation behaves as if no library function calls these functions with a
22354 null pointer for ps.
22355 <p><!--para 2 -->
22356 Also unlike their corresponding functions, the conversion source parameter, src, has a
22357 pointer-to-pointer type. When the function is storing the results of conversions (that is,
22358 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
22359 to reflect the amount of the source processed by that invocation.
22360 <!--page 460 -->
22363 <p><b>Synopsis</b>
22364 <p><!--para 1 -->
22365 <pre>
22367 size_t mbsrtowcs(wchar_t * restrict dst,
22368 const char ** restrict src,
22369 size_t len,
22370 mbstate_t * restrict ps);
22371 </pre>
22372 <p><b>Description</b>
22373 <p><!--para 2 -->
22374 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
22375 conversion state described by the object pointed to by ps, from the array indirectly
22376 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
22377 pointer, the converted characters are stored into the array pointed to by dst. Conversion
22378 continues up to and including a terminating null character, which is also stored.
22379 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
22380 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
22381 characters have been stored into the array pointed to by dst.<sup><a href="#note337"><b>337)</b></a></sup> Each conversion takes
22382 place as if by a call to the mbrtowc function.
22383 <p><!--para 3 -->
22384 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
22385 pointer (if conversion stopped due to reaching a terminating null character) or the address
22386 just past the last multibyte character converted (if any). If conversion stopped due to
22387 reaching a terminating null character and if dst is not a null pointer, the resulting state
22388 described is the initial conversion state.
22389 <p><b>Returns</b>
22390 <p><!--para 4 -->
22391 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
22392 character, an encoding error occurs: the mbsrtowcs function stores the value of the
22393 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
22394 unspecified. Otherwise, it returns the number of multibyte characters successfully
22395 converted, not including the terminating null character (if any).
22400 <!--page 461 -->
22402 <p><b>Footnotes</b>
22403 <p><small><a name="note337" href="#note337">337)</a> Thus, the value of len is ignored if dst is a null pointer.
22404 </small>
22407 <p><b>Synopsis</b>
22408 <p><!--para 1 -->
22409 <pre>
22411 size_t wcsrtombs(char * restrict dst,
22412 const wchar_t ** restrict src,
22413 size_t len,
22414 mbstate_t * restrict ps);
22415 </pre>
22416 <p><b>Description</b>
22417 <p><!--para 2 -->
22418 The wcsrtombs function converts a sequence of wide characters from the array
22419 indirectly pointed to by src into a sequence of corresponding multibyte characters that
22420 begins in the conversion state described by the object pointed to by ps. If dst is not a
22421 null pointer, the converted characters are then stored into the array pointed to by dst.
22422 Conversion continues up to and including a terminating null wide character, which is also
22423 stored. Conversion stops earlier in two cases: when a wide character is reached that does
22424 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
22425 next multibyte character would exceed the limit of len total bytes to be stored into the
22426 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
22428 <p><!--para 3 -->
22429 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
22430 pointer (if conversion stopped due to reaching a terminating null wide character) or the
22431 address just past the last wide character converted (if any). If conversion stopped due to
22432 reaching a terminating null wide character, the resulting state described is the initial
22433 conversion state.
22434 <p><b>Returns</b>
22435 <p><!--para 4 -->
22436 If conversion stops because a wide character is reached that does not correspond to a
22437 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
22438 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
22439 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
22440 character sequence, not including the terminating null character (if any).
22445 <!--page 462 -->
22447 <p><b>Footnotes</b>
22448 <p><small><a name="note338" href="#note338">338)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
22449 include those necessary to reach the initial shift state immediately before the null byte.
22450 </small>
22452 <h3><a name="7.29" href="#7.29">7.29 Wide character classification and mapping utilities <wctype.h></a></h3>
22455 <p><!--para 1 -->
22456 The header <a href="#7.29"><wctype.h></a> defines one macro, and declares three data types and many
22458 <p><!--para 2 -->
22459 The types declared are
22460 <pre>
22461 wint_t
22462 </pre>
22464 <pre>
22465 wctrans_t
22466 </pre>
22467 which is a scalar type that can hold values which represent locale-specific character
22468 mappings; and
22469 <pre>
22470 wctype_t
22471 </pre>
22472 which is a scalar type that can hold values which represent locale-specific character
22473 classifications.
22474 <p><!--para 3 -->
22476 <p><!--para 4 -->
22477 The functions declared are grouped as follows:
22478 <ul>
22479 <li> Functions that provide wide character classification;
22480 <li> Extensible functions that provide wide character classification;
22481 <li> Functions that provide wide character case mapping;
22482 <li> Extensible functions that provide wide character mapping.
22483 </ul>
22484 <p><!--para 5 -->
22485 For all functions described in this subclause that accept an argument of type wint_t, the
22486 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
22487 this argument has any other value, the behavior is undefined.
22488 <p><!--para 6 -->
22489 The behavior of these functions is affected by the LC_CTYPE category of the current
22490 locale.
22495 <!--page 463 -->
22497 <p><b>Footnotes</b>
22498 <p><small><a name="note339" href="#note339">339)</a> See ''future library directions'' (<a href="#7.30.13">7.30.13</a>).
22499 </small>
22502 <p><!--para 1 -->
22503 The header <a href="#7.29"><wctype.h></a> declares several functions useful for classifying wide
22504 characters.
22505 <p><!--para 2 -->
22506 The term printing wide character refers to a member of a locale-specific set of wide
22507 characters, each of which occupies at least one printing position on a display device. The
22508 term control wide character refers to a member of a locale-specific set of wide characters
22509 that are not printing wide characters.
22511 <h5><a name="7.29.2.1" href="#7.29.2.1">7.29.2.1 Wide character classification functions</a></h5>
22512 <p><!--para 1 -->
22513 The functions in this subclause return nonzero (true) if and only if the value of the
22514 argument wc conforms to that in the description of the function.
22515 <p><!--para 2 -->
22516 Each of the following functions returns true for each wide character that corresponds (as
22517 if by a call to the wctob function) to a single-byte character for which the corresponding
22518 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
22519 iswpunct functions may differ with respect to wide characters other than L' ' that are
22523 <p><b>Footnotes</b>
22524 <p><small><a name="note340" href="#note340">340)</a> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
22525 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
22526 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
22527 && iswspace(wc) is true, but not both.
22528 </small>
22531 <p><b>Synopsis</b>
22532 <p><!--para 1 -->
22533 <pre>
22535 int iswalnum(wint_t wc);
22536 </pre>
22537 <p><b>Description</b>
22538 <p><!--para 2 -->
22539 The iswalnum function tests for any wide character for which iswalpha or
22540 iswdigit is true.
22543 <p><b>Synopsis</b>
22544 <p><!--para 1 -->
22545 <pre>
22547 int iswalpha(wint_t wc);
22548 </pre>
22549 <p><b>Description</b>
22550 <p><!--para 2 -->
22551 The iswalpha function tests for any wide character for which iswupper or
22552 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
22554 <!--page 464 -->
22555 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
22558 <p><b>Footnotes</b>
22559 <p><small><a name="note341" href="#note341">341)</a> The functions iswlower and iswupper test true or false separately for each of these additional
22560 wide characters; all four combinations are possible.
22561 </small>
22564 <p><b>Synopsis</b>
22565 <p><!--para 1 -->
22566 <pre>
22568 int iswblank(wint_t wc);
22569 </pre>
22570 <p><b>Description</b>
22571 <p><!--para 2 -->
22572 The iswblank function tests for any wide character that is a standard blank wide
22573 character or is one of a locale-specific set of wide characters for which iswspace is true
22574 and that is used to separate words within a line of text. The standard blank wide
22576 locale, iswblank returns true only for the standard blank characters.
22579 <p><b>Synopsis</b>
22580 <p><!--para 1 -->
22581 <pre>
22583 int iswcntrl(wint_t wc);
22584 </pre>
22585 <p><b>Description</b>
22586 <p><!--para 2 -->
22587 The iswcntrl function tests for any control wide character.
22590 <p><b>Synopsis</b>
22591 <p><!--para 1 -->
22592 <pre>
22594 int iswdigit(wint_t wc);
22595 </pre>
22596 <p><b>Description</b>
22597 <p><!--para 2 -->
22598 The iswdigit function tests for any wide character that corresponds to a decimal-digit
22602 <p><b>Synopsis</b>
22603 <p><!--para 1 -->
22604 <pre>
22606 int iswgraph(wint_t wc);
22607 </pre>
22612 <!--page 465 -->
22613 <p><b>Description</b>
22614 <p><!--para 2 -->
22615 The iswgraph function tests for any wide character for which iswprint is true and
22618 <p><b>Footnotes</b>
22619 <p><small><a name="note342" href="#note342">342)</a> Note that the behavior of the iswgraph and iswpunct functions may differ from their
22620 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
22621 characters other than ' '.
22622 </small>
22625 <p><b>Synopsis</b>
22626 <p><!--para 1 -->
22627 <pre>
22629 int iswlower(wint_t wc);
22630 </pre>
22631 <p><b>Description</b>
22632 <p><!--para 2 -->
22633 The iswlower function tests for any wide character that corresponds to a lowercase
22634 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
22635 iswdigit, iswpunct, or iswspace is true.
22638 <p><b>Synopsis</b>
22639 <p><!--para 1 -->
22640 <pre>
22642 int iswprint(wint_t wc);
22643 </pre>
22644 <p><b>Description</b>
22645 <p><!--para 2 -->
22646 The iswprint function tests for any printing wide character.
22649 <p><b>Synopsis</b>
22650 <p><!--para 1 -->
22651 <pre>
22653 int iswpunct(wint_t wc);
22654 </pre>
22655 <p><b>Description</b>
22656 <p><!--para 2 -->
22657 The iswpunct function tests for any printing wide character that is one of a locale-
22658 specific set of punctuation wide characters for which neither iswspace nor iswalnum
22662 <p><b>Synopsis</b>
22663 <p><!--para 1 -->
22664 <pre>
22666 int iswspace(wint_t wc);
22667 </pre>
22671 <!--page 466 -->
22672 <p><b>Description</b>
22673 <p><!--para 2 -->
22674 The iswspace function tests for any wide character that corresponds to a locale-specific
22675 set of white-space wide characters for which none of iswalnum, iswgraph, or
22676 iswpunct is true.
22679 <p><b>Synopsis</b>
22680 <p><!--para 1 -->
22681 <pre>
22683 int iswupper(wint_t wc);
22684 </pre>
22685 <p><b>Description</b>
22686 <p><!--para 2 -->
22687 The iswupper function tests for any wide character that corresponds to an uppercase
22688 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
22689 iswdigit, iswpunct, or iswspace is true.
22692 <p><b>Synopsis</b>
22693 <p><!--para 1 -->
22694 <pre>
22696 int iswxdigit(wint_t wc);
22697 </pre>
22698 <p><b>Description</b>
22699 <p><!--para 2 -->
22700 The iswxdigit function tests for any wide character that corresponds to a
22703 <h5><a name="7.29.2.2" href="#7.29.2.2">7.29.2.2 Extensible wide character classification functions</a></h5>
22704 <p><!--para 1 -->
22705 The functions wctype and iswctype provide extensible wide character classification
22706 as well as testing equivalent to that performed by the functions described in the previous
22710 <p><b>Synopsis</b>
22711 <p><!--para 1 -->
22712 <pre>
22714 int iswctype(wint_t wc, wctype_t desc);
22715 </pre>
22716 <p><b>Description</b>
22717 <p><!--para 2 -->
22718 The iswctype function determines whether the wide character wc has the property
22719 described by desc. The current setting of the LC_CTYPE category shall be the same as
22720 during the call to wctype that returned the value desc.
22721 <p><!--para 3 -->
22722 Each of the following expressions has a truth-value equivalent to the call to the wide
22723 character classification function (<a href="#7.29.2.1">7.29.2.1</a>) in the comment that follows the expression:
22724 <!--page 467 -->
22725 <pre>
22738 </pre>
22739 <p><b>Returns</b>
22740 <p><!--para 4 -->
22741 The iswctype function returns nonzero (true) if and only if the value of the wide
22742 character wc has the property described by desc. If desc is zero, the iswctype
22743 function returns zero (false).
22747 <p><b>Synopsis</b>
22748 <p><!--para 1 -->
22749 <pre>
22751 wctype_t wctype(const char *property);
22752 </pre>
22753 <p><b>Description</b>
22754 <p><!--para 2 -->
22755 The wctype function constructs a value with type wctype_t that describes a class of
22756 wide characters identified by the string argument property.
22757 <p><!--para 3 -->
22758 The strings listed in the description of the iswctype function shall be valid in all
22759 locales as property arguments to the wctype function.
22760 <p><b>Returns</b>
22761 <p><!--para 4 -->
22762 If property identifies a valid class of wide characters according to the LC_CTYPE
22763 category of the current locale, the wctype function returns a nonzero value that is valid
22764 as the second argument to the iswctype function; otherwise, it returns zero.
22765 <!--page 468 -->
22768 <p><!--para 1 -->
22769 The header <a href="#7.29"><wctype.h></a> declares several functions useful for mapping wide characters.
22771 <h5><a name="7.29.3.1" href="#7.29.3.1">7.29.3.1 Wide character case mapping functions</a></h5>
22774 <p><b>Synopsis</b>
22775 <p><!--para 1 -->
22776 <pre>
22778 wint_t towlower(wint_t wc);
22779 </pre>
22780 <p><b>Description</b>
22781 <p><!--para 2 -->
22782 The towlower function converts an uppercase letter to a corresponding lowercase letter.
22783 <p><b>Returns</b>
22784 <p><!--para 3 -->
22785 If the argument is a wide character for which iswupper is true and there are one or
22786 more corresponding wide characters, as specified by the current locale, for which
22787 iswlower is true, the towlower function returns one of the corresponding wide
22788 characters (always the same one for any given locale); otherwise, the argument is
22789 returned unchanged.
22792 <p><b>Synopsis</b>
22793 <p><!--para 1 -->
22794 <pre>
22796 wint_t towupper(wint_t wc);
22797 </pre>
22798 <p><b>Description</b>
22799 <p><!--para 2 -->
22800 The towupper function converts a lowercase letter to a corresponding uppercase letter.
22801 <p><b>Returns</b>
22802 <p><!--para 3 -->
22803 If the argument is a wide character for which iswlower is true and there are one or
22804 more corresponding wide characters, as specified by the current locale, for which
22805 iswupper is true, the towupper function returns one of the corresponding wide
22806 characters (always the same one for any given locale); otherwise, the argument is
22807 returned unchanged.
22809 <h5><a name="7.29.3.2" href="#7.29.3.2">7.29.3.2 Extensible wide character case mapping functions</a></h5>
22810 <p><!--para 1 -->
22811 The functions wctrans and towctrans provide extensible wide character mapping as
22812 well as case mapping equivalent to that performed by the functions described in the
22814 <!--page 469 -->
22817 <p><b>Synopsis</b>
22818 <p><!--para 1 -->
22819 <pre>
22821 wint_t towctrans(wint_t wc, wctrans_t desc);
22822 </pre>
22823 <p><b>Description</b>
22824 <p><!--para 2 -->
22825 The towctrans function maps the wide character wc using the mapping described by
22826 desc. The current setting of the LC_CTYPE category shall be the same as during the call
22827 to wctrans that returned the value desc.
22828 <p><!--para 3 -->
22829 Each of the following expressions behaves the same as the call to the wide character case
22830 mapping function (<a href="#7.29.3.1">7.29.3.1</a>) in the comment that follows the expression:
22831 <pre>
22834 </pre>
22835 <p><b>Returns</b>
22836 <p><!--para 4 -->
22837 The towctrans function returns the mapped value of wc using the mapping described
22838 by desc. If desc is zero, the towctrans function returns the value of wc.
22841 <p><b>Synopsis</b>
22842 <p><!--para 1 -->
22843 <pre>
22845 wctrans_t wctrans(const char *property);
22846 </pre>
22847 <p><b>Description</b>
22848 <p><!--para 2 -->
22849 The wctrans function constructs a value with type wctrans_t that describes a
22850 mapping between wide characters identified by the string argument property.
22851 <p><!--para 3 -->
22852 The strings listed in the description of the towctrans function shall be valid in all
22853 locales as property arguments to the wctrans function.
22854 <p><b>Returns</b>
22855 <p><!--para 4 -->
22856 If property identifies a valid mapping of wide characters according to the LC_CTYPE
22857 category of the current locale, the wctrans function returns a nonzero value that is valid
22858 as the second argument to the towctrans function; otherwise, it returns zero.
22859 <!--page 470 -->
22862 <p><!--para 1 -->
22863 The following names are grouped under individual headers for convenience. All external
22864 names described below are reserved no matter what headers are included by the program.
22867 <p><!--para 1 -->
22868 The function names
22869 <pre>
22870 cerf cexpm1 clog2
22871 cerfc clog10 clgamma
22872 cexp2 clog1p ctgamma
22873 </pre>
22874 and the same names suffixed with f or l may be added to the declarations in the
22878 <p><!--para 1 -->
22879 Function names that begin with either is or to, and a lowercase letter may be added to
22883 <p><!--para 1 -->
22884 Macros that begin with E and a digit or E and an uppercase letter may be added to the
22887 <h4><a name="7.30.4" href="#7.30.4">7.30.4 Format conversion of integer types <inttypes.h></a></h4>
22888 <p><!--para 1 -->
22889 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
22893 <p><!--para 1 -->
22894 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
22898 <p><!--para 1 -->
22899 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
22903 <p><!--para 1 -->
22904 The ability to undefine and perhaps then redefine the macros bool, true, and false is
22905 an obsolescent feature.
22908 <p><!--para 1 -->
22909 Typedef names beginning with int or uint and ending with _t may be added to the
22910 types defined in the <a href="#7.20"><stdint.h></a> header. Macro names beginning with INT or UINT
22911 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
22913 <!--page 471 -->
22916 <p><!--para 1 -->
22917 Lowercase letters may be added to the conversion specifiers and length modifiers in
22918 fprintf and fscanf. Other characters may be used in extensions.
22919 <p><!--para 2 -->
22920 The use of ungetc on a binary stream where the file position indicator is zero prior to *
22921 the call is an obsolescent feature.
22924 <p><!--para 1 -->
22925 Function names that begin with str and a lowercase letter may be added to the
22929 <p><!--para 1 -->
22930 Function names that begin with str, mem, or wcs and a lowercase letter may be added
22933 <h4><a name="7.30.12" href="#7.30.12">7.30.12 Extended multibyte and wide character utilities <wchar.h></a></h4>
22934 <p><!--para 1 -->
22935 Function names that begin with wcs and a lowercase letter may be added to the
22937 <p><!--para 2 -->
22938 Lowercase letters may be added to the conversion specifiers and length modifiers in
22939 fwprintf and fwscanf. Other characters may be used in extensions.
22941 <h4><a name="7.30.13" href="#7.30.13">7.30.13 Wide character classification and mapping utilities</a></h4>
22943 <p><!--para 1 -->
22944 Function names that begin with is or to and a lowercase letter may be added to the
22946 <!--page 472 -->
22949 <pre>
22950 (informative)
22951 Language syntax summary
22952 </pre>
22953 <p><!--para 1 -->
22961 <pre>
22962 keyword
22963 identifier
22964 constant
22965 string-literal
22966 punctuator
22967 </pre>
22969 <!--page 473 -->
22970 <pre>
22971 header-name
22972 identifier
22973 pp-number
22974 character-constant
22975 string-literal
22976 punctuator
22977 each non-white-space character that cannot be one of the above
22978 </pre>
22982 <pre>
22983 alignof goto union
22984 auto if unsigned
22985 break inline void
22986 case int volatile
22987 char long while
22988 const register _Alignas
22989 continue restrict _Atomic
22990 default return _Bool
22991 do short _Complex
22992 double signed _Generic
22993 else sizeof _Imaginary
22994 enum static _Noreturn
22995 extern struct _Static_assert
22996 float switch _Thread_local
22997 for typedef
22998 </pre>
23002 <pre>
23003 identifier-nondigit
23004 identifier identifier-nondigit
23005 identifier digit
23006 </pre>
23008 <pre>
23009 nondigit
23010 universal-character-name
23011 other implementation-defined characters
23012 </pre>
23014 <pre>
23015 _ a b c d e f g h i j k l m
23016 n o p q r s t u v w x y z
23017 A B C D E F G H I J K L M
23018 N O P Q R S T U V W X Y Z
23019 </pre>
23021 <!--page 474 -->
23022 <pre>
23023 0 1 2 3 4 5 6 7 8 9
23024 </pre>
23028 <pre>
23029 \u hex-quad
23030 \U hex-quad hex-quad
23031 </pre>
23033 <pre>
23034 hexadecimal-digit hexadecimal-digit
23035 hexadecimal-digit hexadecimal-digit
23036 </pre>
23040 <pre>
23041 integer-constant
23042 floating-constant
23043 enumeration-constant
23044 character-constant
23045 </pre>
23047 <pre>
23048 decimal-constant integer-suffix<sub>opt</sub>
23049 octal-constant integer-suffix<sub>opt</sub>
23050 hexadecimal-constant integer-suffix<sub>opt</sub>
23051 </pre>
23053 <pre>
23054 nonzero-digit
23055 decimal-constant digit
23056 </pre>
23058 <pre>
23059 0
23060 octal-constant octal-digit
23061 </pre>
23063 <pre>
23064 hexadecimal-prefix hexadecimal-digit
23065 hexadecimal-constant hexadecimal-digit
23066 </pre>
23068 <pre>
23069 0x 0X
23070 </pre>
23072 <pre>
23073 1 2 3 4 5 6 7 8 9
23074 </pre>
23076 <!--page 475 -->
23077 <pre>
23078 0 1 2 3 4 5 6 7
23079 </pre>
23081 <pre>
23082 0 1 2 3 4 5 6 7 8 9
23083 a b c d e f
23084 A B C D E F
23085 </pre>
23087 <pre>
23088 unsigned-suffix long-suffix<sub>opt</sub>
23089 unsigned-suffix long-long-suffix
23090 long-suffix unsigned-suffix<sub>opt</sub>
23091 long-long-suffix unsigned-suffix<sub>opt</sub>
23092 </pre>
23094 <pre>
23095 u U
23096 </pre>
23098 <pre>
23099 l L
23100 </pre>
23102 <pre>
23103 ll LL
23104 </pre>
23106 <pre>
23107 decimal-floating-constant
23108 hexadecimal-floating-constant
23109 </pre>
23111 <pre>
23112 fractional-constant exponent-part<sub>opt</sub> floating-suffix<sub>opt</sub>
23113 digit-sequence exponent-part floating-suffix<sub>opt</sub>
23114 </pre>
23116 <pre>
23117 hexadecimal-prefix hexadecimal-fractional-constant
23118 binary-exponent-part floating-suffix<sub>opt</sub>
23119 hexadecimal-prefix hexadecimal-digit-sequence
23120 binary-exponent-part floating-suffix<sub>opt</sub>
23121 </pre>
23123 <pre>
23124 digit-sequence<sub>opt</sub> . digit-sequence
23125 digit-sequence .
23126 </pre>
23128 <pre>
23129 e sign<sub>opt</sub> digit-sequence
23130 E sign<sub>opt</sub> digit-sequence
23131 </pre>
23133 <!--page 476 -->
23134 <pre>
23135 + -
23136 </pre>
23138 <pre>
23139 digit
23140 digit-sequence digit
23141 </pre>
23143 <pre>
23144 hexadecimal-digit-sequence<sub>opt</sub> .
23145 hexadecimal-digit-sequence
23146 hexadecimal-digit-sequence .
23147 </pre>
23149 <pre>
23150 p sign<sub>opt</sub> digit-sequence
23151 P sign<sub>opt</sub> digit-sequence
23152 </pre>
23154 <pre>
23155 hexadecimal-digit
23156 hexadecimal-digit-sequence hexadecimal-digit
23157 </pre>
23159 <pre>
23160 f l F L
23161 </pre>
23163 <pre>
23164 identifier
23165 </pre>
23167 <pre>
23168 ' c-char-sequence '
23169 L' c-char-sequence '
23170 u' c-char-sequence '
23171 U' c-char-sequence '
23172 </pre>
23174 <pre>
23175 c-char
23176 c-char-sequence c-char
23177 </pre>
23179 <pre>
23180 any member of the source character set except
23181 the single-quote ', backslash \, or new-line character
23182 escape-sequence
23183 </pre>
23185 <!--page 477 -->
23186 <pre>
23187 simple-escape-sequence
23188 octal-escape-sequence
23189 hexadecimal-escape-sequence
23190 universal-character-name
23191 </pre>
23193 <pre>
23194 \' \" \? \\
23195 \a \b \f \n \r \t \v
23196 </pre>
23198 <pre>
23199 \ octal-digit
23200 \ octal-digit octal-digit
23201 \ octal-digit octal-digit octal-digit
23202 </pre>
23204 <pre>
23205 \x hexadecimal-digit
23206 hexadecimal-escape-sequence hexadecimal-digit
23207 </pre>
23211 <pre>
23213 </pre>
23215 <pre>
23216 u8
23217 u
23218 U
23219 L
23220 </pre>
23222 <pre>
23223 s-char
23224 s-char-sequence s-char
23225 </pre>
23227 <pre>
23228 any member of the source character set except
23229 the double-quote ", backslash \, or new-line character
23230 escape-sequence
23231 </pre>
23235 <!--page 478 -->
23236 <pre>
23237 [ ] ( ) { } . ->
23238 ++ -- & * + - ~ !
23239 / % << >> < > <= >= == != ^ | && ||
23240 ? : ; ...
23241 = *= /= %= += -= <<= >>= &= ^= |=
23242 , # ##
23243 <: :> <% %> %: %:%:
23244 </pre>
23248 <pre>
23249 < h-char-sequence >
23251 </pre>
23253 <pre>
23254 h-char
23255 h-char-sequence h-char
23256 </pre>
23258 <pre>
23259 any member of the source character set except
23260 the new-line character and >
23261 </pre>
23263 <pre>
23264 q-char
23265 q-char-sequence q-char
23266 </pre>
23268 <pre>
23269 any member of the source character set except
23270 the new-line character and "
23271 </pre>
23275 <!--page 479 -->
23276 <pre>
23277 digit
23278 . digit
23279 pp-number digit
23280 pp-number identifier-nondigit
23281 pp-number e sign
23282 pp-number E sign
23283 pp-number p sign
23284 pp-number P sign
23285 pp-number .
23286 </pre>
23292 <pre>
23293 identifier
23294 constant
23295 string-literal
23296 ( expression )
23297 generic-selection
23298 </pre>
23300 <pre>
23301 _Generic ( assignment-expression , generic-assoc-list )
23302 </pre>
23304 <pre>
23305 generic-association
23306 generic-assoc-list , generic-association
23307 </pre>
23309 <pre>
23310 type-name : assignment-expression
23311 default : assignment-expression
23312 </pre>
23314 <pre>
23315 primary-expression
23316 postfix-expression [ expression ]
23318 postfix-expression . identifier
23319 postfix-expression -> identifier
23320 postfix-expression ++
23321 postfix-expression --
23322 ( type-name ) { initializer-list }
23323 ( type-name ) { initializer-list , }
23324 </pre>
23326 <pre>
23327 assignment-expression
23328 argument-expression-list , assignment-expression
23329 </pre>
23331 <!--page 480 -->
23332 <pre>
23333 postfix-expression
23334 ++ unary-expression
23335 -- unary-expression
23336 unary-operator cast-expression
23337 sizeof unary-expression
23338 sizeof ( type-name )
23339 alignof ( type-name )
23340 </pre>
23342 <pre>
23343 & * + - ~ !
23344 </pre>
23346 <pre>
23347 unary-expression
23348 ( type-name ) cast-expression
23349 </pre>
23351 <pre>
23352 cast-expression
23353 multiplicative-expression * cast-expression
23354 multiplicative-expression / cast-expression
23355 multiplicative-expression % cast-expression
23356 </pre>
23358 <pre>
23359 multiplicative-expression
23360 additive-expression + multiplicative-expression
23361 additive-expression - multiplicative-expression
23362 </pre>
23364 <pre>
23365 additive-expression
23366 shift-expression << additive-expression
23367 shift-expression >> additive-expression
23368 </pre>
23370 <pre>
23371 shift-expression
23372 relational-expression < shift-expression
23373 relational-expression > shift-expression
23374 relational-expression <= shift-expression
23375 relational-expression >= shift-expression
23376 </pre>
23378 <pre>
23379 relational-expression
23380 equality-expression == relational-expression
23381 equality-expression != relational-expression
23382 </pre>
23384 <pre>
23385 equality-expression
23386 AND-expression & equality-expression
23387 </pre>
23389 <!--page 481 -->
23390 <pre>
23391 AND-expression
23392 exclusive-OR-expression ^ AND-expression
23393 </pre>
23395 <pre>
23396 exclusive-OR-expression
23397 inclusive-OR-expression | exclusive-OR-expression
23398 </pre>
23400 <pre>
23401 inclusive-OR-expression
23402 logical-AND-expression && inclusive-OR-expression
23403 </pre>
23405 <pre>
23406 logical-AND-expression
23407 logical-OR-expression || logical-AND-expression
23408 </pre>
23410 <pre>
23411 logical-OR-expression
23412 logical-OR-expression ? expression : conditional-expression
23413 </pre>
23415 <pre>
23416 conditional-expression
23417 unary-expression assignment-operator assignment-expression
23418 </pre>
23420 <pre>
23422 </pre>
23424 <pre>
23425 assignment-expression
23426 expression , assignment-expression
23427 </pre>
23429 <pre>
23430 conditional-expression
23431 </pre>
23435 <pre>
23437 static_assert-declaration
23438 </pre>
23440 <pre>
23446 </pre>
23448 <!--page 482 -->
23449 <pre>
23450 init-declarator
23451 init-declarator-list , init-declarator
23452 </pre>
23454 <pre>
23455 declarator
23456 declarator = initializer
23457 </pre>
23459 <pre>
23460 typedef
23461 extern
23462 static
23463 _Thread_local
23464 auto
23465 register
23466 </pre>
23468 <pre>
23469 void
23470 char
23471 short
23472 int
23473 long
23474 float
23475 double
23476 signed
23477 unsigned
23478 _Bool
23479 _Complex
23480 atomic-type-specifier
23481 struct-or-union-specifier
23482 enum-specifier
23483 typedef-name
23484 </pre>
23486 <pre>
23488 struct-or-union identifier
23489 </pre>
23491 <pre>
23492 struct
23493 union
23494 </pre>
23496 <pre>
23497 struct-declaration
23498 struct-declaration-list struct-declaration
23499 </pre>
23501 <!--page 483 -->
23502 <pre>
23504 static_assert-declaration
23505 </pre>
23507 <pre>
23510 </pre>
23512 <pre>
23513 struct-declarator
23514 struct-declarator-list , struct-declarator
23515 </pre>
23517 <pre>
23518 declarator
23520 </pre>
23522 <pre>
23525 enum identifier
23526 </pre>
23528 <pre>
23529 enumerator
23530 enumerator-list , enumerator
23531 </pre>
23533 <pre>
23534 enumeration-constant
23535 enumeration-constant = constant-expression
23536 </pre>
23538 <pre>
23539 _Atomic ( type-name )
23540 </pre>
23542 <pre>
23543 const
23544 restrict
23545 volatile
23546 _Atomic
23547 </pre>
23549 <pre>
23550 inline
23551 _Noreturn
23552 </pre>
23554 <pre>
23555 _Alignas ( type-name )
23556 _Alignas ( constant-expression )
23557 </pre>
23559 <!--page 484 -->
23560 <pre>
23562 </pre>
23564 <pre>
23565 identifier
23566 ( declarator )
23569 direct-declarator [ type-qualifier-list static assignment-expression ]
23571 direct-declarator ( parameter-type-list )
23573 </pre>
23575 <pre>
23578 </pre>
23580 <pre>
23581 type-qualifier
23582 type-qualifier-list type-qualifier
23583 </pre>
23585 <pre>
23586 parameter-list
23587 parameter-list , ...
23588 </pre>
23590 <pre>
23591 parameter-declaration
23592 parameter-list , parameter-declaration
23593 </pre>
23595 <pre>
23596 declaration-specifiers declarator
23598 </pre>
23600 <pre>
23601 identifier
23602 identifier-list , identifier
23603 </pre>
23605 <pre>
23607 </pre>
23609 <!--page 485 -->
23610 <pre>
23611 pointer
23613 </pre>
23615 <pre>
23616 ( abstract-declarator )
23620 assignment-expression ]
23622 assignment-expression ]
23625 </pre>
23627 <pre>
23628 identifier
23629 </pre>
23631 <pre>
23632 assignment-expression
23633 { initializer-list }
23634 { initializer-list , }
23635 </pre>
23637 <pre>
23640 </pre>
23642 <pre>
23643 designator-list =
23644 </pre>
23646 <pre>
23647 designator
23648 designator-list designator
23649 </pre>
23651 <pre>
23652 [ constant-expression ]
23653 . identifier
23654 </pre>
23656 <!--page 486 -->
23657 <pre>
23658 _Static_assert ( constant-expression , string-literal ) ;
23659 </pre>
23663 <pre>
23664 labeled-statement
23665 compound-statement
23666 expression-statement
23667 selection-statement
23668 iteration-statement
23669 jump-statement
23670 </pre>
23672 <pre>
23673 identifier : statement
23674 case constant-expression : statement
23675 default : statement
23676 </pre>
23678 <pre>
23680 </pre>
23682 <pre>
23683 block-item
23684 block-item-list block-item
23685 </pre>
23687 <pre>
23688 declaration
23689 statement
23690 </pre>
23692 <pre>
23694 </pre>
23696 <pre>
23697 if ( expression ) statement
23698 if ( expression ) statement else statement
23699 switch ( expression ) statement
23700 </pre>
23702 <pre>
23703 while ( expression ) statement
23704 do statement while ( expression ) ;
23705 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
23707 </pre>
23709 <!--page 487 -->
23710 <pre>
23711 goto identifier ;
23712 continue ;
23713 break ;
23715 </pre>
23719 <pre>
23720 external-declaration
23721 translation-unit external-declaration
23722 </pre>
23724 <pre>
23725 function-definition
23726 declaration
23727 </pre>
23729 <pre>
23731 </pre>
23733 <pre>
23734 declaration
23735 declaration-list declaration
23736 </pre>
23740 <pre>
23742 </pre>
23744 <pre>
23745 group-part
23746 group group-part
23747 </pre>
23749 <pre>
23750 if-section
23751 control-line
23752 text-line
23753 # non-directive
23754 </pre>
23756 <pre>
23758 </pre>
23760 <pre>
23764 </pre>
23766 <pre>
23767 elif-group
23768 elif-groups elif-group
23769 </pre>
23771 <!--page 488 -->
23772 <pre>
23774 </pre>
23776 <pre>
23778 </pre>
23780 <pre>
23781 # endif new-line
23782 </pre>
23784 <pre>
23785 # include pp-tokens new-line
23786 # define identifier replacement-list new-line
23788 replacement-list new-line
23789 # define identifier lparen ... ) replacement-list new-line
23790 # define identifier lparen identifier-list , ... )
23791 replacement-list new-line
23792 # undef identifier new-line
23793 # line pp-tokens new-line
23796 # new-line
23797 </pre>
23799 <pre>
23801 </pre>
23803 <pre>
23804 pp-tokens new-line
23805 </pre>
23807 <pre>
23808 a ( character not immediately preceded by white-space
23809 </pre>
23811 <pre>
23813 </pre>
23815 <pre>
23816 preprocessing-token
23817 pp-tokens preprocessing-token
23818 </pre>
23820 <!--page 489 -->
23821 <pre>
23822 the new-line character
23823 </pre>
23826 <pre>
23827 (informative)
23828 Library summary
23829 </pre>
23832 <pre>
23833 NDEBUG
23834 static_assert
23835 void assert(scalar expression);
23836 </pre>
23839 <!--page 490 -->
23840 <!--page 491 -->
23841 <pre>
23842 __STDC_NO_COMPLEX__ imaginary
23843 complex _Imaginary_I
23844 _Complex_I I
23845 #pragma STDC CX_LIMITED_RANGE on-off-switch
23846 double complex cacos(double complex z);
23847 float complex cacosf(float complex z);
23848 long double complex cacosl(long double complex z);
23849 double complex casin(double complex z);
23850 float complex casinf(float complex z);
23851 long double complex casinl(long double complex z);
23852 double complex catan(double complex z);
23853 float complex catanf(float complex z);
23854 long double complex catanl(long double complex z);
23855 double complex ccos(double complex z);
23856 float complex ccosf(float complex z);
23857 long double complex ccosl(long double complex z);
23858 double complex csin(double complex z);
23859 float complex csinf(float complex z);
23860 long double complex csinl(long double complex z);
23861 double complex ctan(double complex z);
23862 float complex ctanf(float complex z);
23863 long double complex ctanl(long double complex z);
23864 double complex cacosh(double complex z);
23865 float complex cacoshf(float complex z);
23866 long double complex cacoshl(long double complex z);
23867 double complex casinh(double complex z);
23868 float complex casinhf(float complex z);
23869 long double complex casinhl(long double complex z);
23870 double complex catanh(double complex z);
23871 float complex catanhf(float complex z);
23872 long double complex catanhl(long double complex z);
23873 double complex ccosh(double complex z);
23874 float complex ccoshf(float complex z);
23875 long double complex ccoshl(long double complex z);
23876 double complex csinh(double complex z);
23877 float complex csinhf(float complex z);
23878 long double complex csinhl(long double complex z);
23879 double complex ctanh(double complex z);
23880 float complex ctanhf(float complex z);
23881 long double complex ctanhl(long double complex z);
23882 double complex cexp(double complex z);
23883 float complex cexpf(float complex z);
23884 long double complex cexpl(long double complex z);
23885 double complex clog(double complex z);
23886 float complex clogf(float complex z);
23887 long double complex clogl(long double complex z);
23888 double cabs(double complex z);
23889 float cabsf(float complex z);
23890 long double cabsl(long double complex z);
23891 double complex cpow(double complex x, double complex y);
23892 float complex cpowf(float complex x, float complex y);
23893 long double complex cpowl(long double complex x,
23894 long double complex y);
23895 double complex csqrt(double complex z);
23896 float complex csqrtf(float complex z);
23897 long double complex csqrtl(long double complex z);
23898 double carg(double complex z);
23899 float cargf(float complex z);
23900 long double cargl(long double complex z);
23901 double cimag(double complex z);
23902 float cimagf(float complex z);
23903 long double cimagl(long double complex z);
23904 double complex CMPLX(double x, double y);
23905 float complex CMPLXF(float x, float y);
23906 long double complex CMPLXL(long double x, long double y);
23907 double complex conj(double complex z);
23908 float complex conjf(float complex z);
23909 long double complex conjl(long double complex z);
23910 double complex cproj(double complex z);
23911 float complex cprojf(float complex z);
23912 long double complex cprojl(long double complex z);
23913 double creal(double complex z);
23914 float crealf(float complex z);
23915 long double creall(long double complex z);
23916 </pre>
23919 <pre>
23920 int isalnum(int c);
23921 int isalpha(int c);
23922 int isblank(int c);
23923 int iscntrl(int c);
23924 int isdigit(int c);
23925 int isgraph(int c);
23926 int islower(int c);
23927 int isprint(int c);
23928 int ispunct(int c);
23929 int isspace(int c);
23930 int isupper(int c);
23931 int isxdigit(int c);
23932 int tolower(int c);
23933 int toupper(int c);
23934 </pre>
23937 <pre>
23938 EDOM EILSEQ ERANGE errno
23939 __STDC_WANT_LIB_EXT1__
23940 errno_t
23941 </pre>
23944 <!--page 492 -->
23945 <pre>
23946 fenv_t FE_OVERFLOW FE_TOWARDZERO
23947 fexcept_t FE_UNDERFLOW FE_UPWARD
23948 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
23949 FE_INEXACT FE_DOWNWARD
23950 FE_INVALID FE_TONEAREST
23951 #pragma STDC FENV_ACCESS on-off-switch
23952 int feclearexcept(int excepts);
23953 int fegetexceptflag(fexcept_t *flagp, int excepts);
23954 int feraiseexcept(int excepts);
23955 int fesetexceptflag(const fexcept_t *flagp,
23956 int excepts);
23957 int fetestexcept(int excepts);
23958 int fegetround(void);
23959 int fesetround(int round);
23960 int fegetenv(fenv_t *envp);
23961 int feholdexcept(fenv_t *envp);
23962 int fesetenv(const fenv_t *envp);
23963 int feupdateenv(const fenv_t *envp);
23964 </pre>
23967 <pre>
23968 FLT_ROUNDS DBL_DIG FLT_MAX
23969 FLT_EVAL_METHOD LDBL_DIG DBL_MAX
23970 FLT_HAS_SUBNORM FLT_MIN_EXP LDBL_MAX
23971 DBL_HAS_SUBNORM DBL_MIN_EXP FLT_EPSILON
23972 LDBL_HAS_SUBNORM LDBL_MIN_EXP DBL_EPSILON
23973 FLT_RADIX FLT_MIN_10_EXP LDBL_EPSILON
23974 FLT_MANT_DIG DBL_MIN_10_EXP FLT_MIN
23975 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_MIN
23976 LDBL_MANT_DIG FLT_MAX_EXP LDBL_MIN
23977 FLT_DECIMAL_DIG DBL_MAX_EXP FLT_TRUE_MIN
23978 DBL_DECIMAL_DIG LDBL_MAX_EXP DBL_TRUE_MIN
23979 LDBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_TRUE_MIN
23980 DECIMAL_DIG DBL_MAX_10_EXP
23981 FLT_DIG LDBL_MAX_10_EXP
23982 </pre>
23984 <h3><a name="B.7" href="#B.7">B.7 Format conversion of integer types <inttypes.h></a></h3>
23985 <!--page 493 -->
23986 <pre>
23987 imaxdiv_t
23988 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
23989 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
23990 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
23991 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
23992 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
23993 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
23994 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
23995 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
23996 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
23997 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
23998 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
23999 intmax_t imaxabs(intmax_t j);
24000 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
24001 intmax_t strtoimax(const char * restrict nptr,
24002 char ** restrict endptr, int base);
24003 uintmax_t strtoumax(const char * restrict nptr,
24004 char ** restrict endptr, int base);
24005 intmax_t wcstoimax(const wchar_t * restrict nptr,
24006 wchar_t ** restrict endptr, int base);
24007 uintmax_t wcstoumax(const wchar_t * restrict nptr,
24008 wchar_t ** restrict endptr, int base);
24009 </pre>
24012 <pre>
24013 and bitor not_eq xor
24014 and_eq compl or xor_eq
24015 bitand not or_eq
24016 </pre>
24019 <pre>
24020 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
24021 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
24022 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
24023 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
24024 CHAR_MIN USHRT_MAX LONG_MAX
24025 </pre>
24028 <pre>
24029 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
24030 NULL LC_COLLATE LC_MONETARY LC_TIME
24031 char *setlocale(int category, const char *locale);
24032 struct lconv *localeconv(void);
24033 </pre>
24036 <!--page 494 -->
24037 <!--page 495 -->
24038 <!--page 496 -->
24039 <!--page 497 -->
24040 <!--page 498 -->
24041 <pre>
24042 float_t FP_INFINITE FP_FAST_FMAL
24043 double_t FP_NAN FP_ILOGB0
24044 HUGE_VAL FP_NORMAL FP_ILOGBNAN
24045 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
24046 HUGE_VALL FP_ZERO MATH_ERREXCEPT
24047 INFINITY FP_FAST_FMA math_errhandling
24048 NAN FP_FAST_FMAF
24049 #pragma STDC FP_CONTRACT on-off-switch
24050 int fpclassify(real-floating x);
24051 int isfinite(real-floating x);
24052 int isinf(real-floating x);
24053 int isnan(real-floating x);
24054 int isnormal(real-floating x);
24055 int signbit(real-floating x);
24056 double acos(double x);
24057 float acosf(float x);
24058 long double acosl(long double x);
24059 double asin(double x);
24060 float asinf(float x);
24061 long double asinl(long double x);
24062 double atan(double x);
24063 float atanf(float x);
24064 long double atanl(long double x);
24065 double atan2(double y, double x);
24066 float atan2f(float y, float x);
24067 long double atan2l(long double y, long double x);
24068 double cos(double x);
24069 float cosf(float x);
24070 long double cosl(long double x);
24071 double sin(double x);
24072 float sinf(float x);
24073 long double sinl(long double x);
24074 double tan(double x);
24075 float tanf(float x);
24076 long double tanl(long double x);
24077 double acosh(double x);
24078 float acoshf(float x);
24079 long double acoshl(long double x);
24080 double asinh(double x);
24081 float asinhf(float x);
24082 long double asinhl(long double x);
24083 double atanh(double x);
24084 float atanhf(float x);
24085 long double atanhl(long double x);
24086 double cosh(double x);
24087 float coshf(float x);
24088 long double coshl(long double x);
24089 double sinh(double x);
24090 float sinhf(float x);
24091 long double sinhl(long double x);
24092 double tanh(double x);
24093 float tanhf(float x);
24094 long double tanhl(long double x);
24095 double exp(double x);
24096 float expf(float x);
24097 long double expl(long double x);
24098 double exp2(double x);
24099 float exp2f(float x);
24100 long double exp2l(long double x);
24101 double expm1(double x);
24102 float expm1f(float x);
24103 long double expm1l(long double x);
24104 double frexp(double value, int *exp);
24105 float frexpf(float value, int *exp);
24106 long double frexpl(long double value, int *exp);
24107 int ilogb(double x);
24108 int ilogbf(float x);
24109 int ilogbl(long double x);
24110 double ldexp(double x, int exp);
24111 float ldexpf(float x, int exp);
24112 long double ldexpl(long double x, int exp);
24113 double log(double x);
24114 float logf(float x);
24115 long double logl(long double x);
24116 double log10(double x);
24117 float log10f(float x);
24118 long double log10l(long double x);
24119 double log1p(double x);
24120 float log1pf(float x);
24121 long double log1pl(long double x);
24122 double log2(double x);
24123 float log2f(float x);
24124 long double log2l(long double x);
24125 double logb(double x);
24126 float logbf(float x);
24127 long double logbl(long double x);
24128 double modf(double value, double *iptr);
24129 float modff(float value, float *iptr);
24130 long double modfl(long double value, long double *iptr);
24131 double scalbn(double x, int n);
24132 float scalbnf(float x, int n);
24133 long double scalbnl(long double x, int n);
24134 double scalbln(double x, long int n);
24135 float scalblnf(float x, long int n);
24136 long double scalblnl(long double x, long int n);
24137 double cbrt(double x);
24138 float cbrtf(float x);
24139 long double cbrtl(long double x);
24140 double fabs(double x);
24141 float fabsf(float x);
24142 long double fabsl(long double x);
24143 double hypot(double x, double y);
24144 float hypotf(float x, float y);
24145 long double hypotl(long double x, long double y);
24146 double pow(double x, double y);
24147 float powf(float x, float y);
24148 long double powl(long double x, long double y);
24149 double sqrt(double x);
24150 float sqrtf(float x);
24151 long double sqrtl(long double x);
24152 double erf(double x);
24153 float erff(float x);
24154 long double erfl(long double x);
24155 double erfc(double x);
24156 float erfcf(float x);
24157 long double erfcl(long double x);
24158 double lgamma(double x);
24159 float lgammaf(float x);
24160 long double lgammal(long double x);
24161 double tgamma(double x);
24162 float tgammaf(float x);
24163 long double tgammal(long double x);
24164 double ceil(double x);
24165 float ceilf(float x);
24166 long double ceill(long double x);
24167 double floor(double x);
24168 float floorf(float x);
24169 long double floorl(long double x);
24170 double nearbyint(double x);
24171 float nearbyintf(float x);
24172 long double nearbyintl(long double x);
24173 double rint(double x);
24174 float rintf(float x);
24175 long double rintl(long double x);
24176 long int lrint(double x);
24177 long int lrintf(float x);
24178 long int lrintl(long double x);
24179 long long int llrint(double x);
24180 long long int llrintf(float x);
24181 long long int llrintl(long double x);
24182 double round(double x);
24183 float roundf(float x);
24184 long double roundl(long double x);
24185 long int lround(double x);
24186 long int lroundf(float x);
24187 long int lroundl(long double x);
24188 long long int llround(double x);
24189 long long int llroundf(float x);
24190 long long int llroundl(long double x);
24191 double trunc(double x);
24192 float truncf(float x);
24193 long double truncl(long double x);
24194 double fmod(double x, double y);
24195 float fmodf(float x, float y);
24196 long double fmodl(long double x, long double y);
24197 double remainder(double x, double y);
24198 float remainderf(float x, float y);
24199 long double remainderl(long double x, long double y);
24200 double remquo(double x, double y, int *quo);
24201 float remquof(float x, float y, int *quo);
24202 long double remquol(long double x, long double y,
24203 int *quo);
24204 double copysign(double x, double y);
24205 float copysignf(float x, float y);
24206 long double copysignl(long double x, long double y);
24207 double nan(const char *tagp);
24208 float nanf(const char *tagp);
24209 long double nanl(const char *tagp);
24210 double nextafter(double x, double y);
24211 float nextafterf(float x, float y);
24212 long double nextafterl(long double x, long double y);
24213 double nexttoward(double x, long double y);
24214 float nexttowardf(float x, long double y);
24215 long double nexttowardl(long double x, long double y);
24216 double fdim(double x, double y);
24217 float fdimf(float x, float y);
24218 long double fdiml(long double x, long double y);
24219 double fmax(double x, double y);
24220 float fmaxf(float x, float y);
24221 long double fmaxl(long double x, long double y);
24222 double fmin(double x, double y);
24223 float fminf(float x, float y);
24224 long double fminl(long double x, long double y);
24225 double fma(double x, double y, double z);
24226 float fmaf(float x, float y, float z);
24227 long double fmal(long double x, long double y,
24228 long double z);
24229 int isgreater(real-floating x, real-floating y);
24230 int isgreaterequal(real-floating x, real-floating y);
24231 int isless(real-floating x, real-floating y);
24232 int islessequal(real-floating x, real-floating y);
24233 int islessgreater(real-floating x, real-floating y);
24234 int isunordered(real-floating x, real-floating y);
24235 </pre>
24238 <pre>
24239 jmp_buf
24240 int setjmp(jmp_buf env);
24241 _Noreturn void longjmp(jmp_buf env, int val);
24242 </pre>
24245 <!--page 499 -->
24246 <pre>
24247 sig_atomic_t SIG_IGN SIGILL SIGTERM
24248 SIG_DFL SIGABRT SIGINT
24249 SIG_ERR SIGFPE SIGSEGV
24250 void (*signal(int sig, void (*func)(int)))(int);
24251 int raise(int sig);
24252 </pre>
24255 <pre>
24256 alignas
24257 __alignas_is_defined
24258 </pre>
24261 <pre>
24262 va_list
24263 type va_arg(va_list ap, type);
24264 void va_copy(va_list dest, va_list src);
24265 void va_end(va_list ap);
24266 void va_start(va_list ap, parmN);
24267 </pre>
24270 <!--page 500 -->
24271 <!--page 501 -->
24272 <pre>
24273 ATOMIC_CHAR_LOCK_FREE atomic_uint
24274 ATOMIC_CHAR16_T_LOCK_FREE atomic_long
24275 ATOMIC_CHAR32_T_LOCK_FREE atomic_ulong
24276 ATOMIC_WCHAR_T_LOCK_FREE atomic_llong
24277 ATOMIC_SHORT_LOCK_FREE atomic_ullong
24278 ATOMIC_INT_LOCK_FREE atomic_char16_t
24279 ATOMIC_LONG_LOCK_FREE atomic_char32_t
24280 ATOMIC_LLONG_LOCK_FREE atomic_wchar_t
24281 ATOMIC_ADDRESS_LOCK_FREE atomic_int_least8_t
24282 ATOMIC_FLAG_INIT atomic_uint_least8_t
24283 memory_order atomic_int_least16_t
24284 atomic_flag atomic_uint_least16_t
24285 atomic_bool atomic_int_least32_t
24286 atomic_address atomic_uint_least32_t
24287 memory_order_relaxed atomic_int_least64_t
24288 memory_order_consume atomic_uint_least64_t
24289 memory_order_acquire atomic_int_fast8_t
24290 memory_order_release atomic_uint_fast8_t
24291 memory_order_acq_rel atomic_int_fast16_t
24292 memory_order_seq_cst atomic_uint_fast16_t
24293 atomic_char atomic_int_fast32_t
24294 atomic_schar atomic_uint_fast32_t
24295 atomic_uchar atomic_int_fast64_t
24296 atomic_short atomic_uint_fast64_t
24297 atomic_ushort atomic_intptr_t
24298 atomic_int atomic_uintptr_t
24299 atomic_size_t atomic_intmax_t
24300 atomic_ptrdiff_t atomic_uintmax_t
24301 #define ATOMIC_VAR_INIT(C value)
24302 void atomic_init(volatile A *obj, C value);
24303 type kill_dependency(type y);
24304 void atomic_thread_fence(memory_order order);
24305 void atomic_signal_fence(memory_order order);
24306 _Bool atomic_is_lock_free(atomic_type const volatile *obj);
24307 void atomic_store(volatile A *object, C desired);
24308 void atomic_store_explicit(volatile A *object,
24309 C desired, memory_order order);
24310 C atomic_load(volatile A *object);
24311 C atomic_load_explicit(volatile A *object,
24312 memory_order order);
24313 C atomic_exchange(volatile A *object, C desired);
24314 C atomic_exchange_explicit(volatile A *object,
24315 C desired, memory_order order);
24316 _Bool atomic_compare_exchange_strong(volatile A *object,
24317 C *expected, C desired);
24318 _Bool atomic_compare_exchange_strong_explicit(
24319 volatile A *object, C *expected, C desired,
24320 memory_order success, memory_order failure);
24321 _Bool atomic_compare_exchange_weak(volatile A *object,
24322 C *expected, C desired);
24323 _Bool atomic_compare_exchange_weak_explicit(
24324 volatile A *object, C *expected, C desired,
24325 memory_order success, memory_order failure);
24326 C atomic_fetch_key(volatile A *object, M operand);
24327 C atomic_fetch_key_explicit(volatile A *object,
24328 M operand, memory_order order);
24329 bool atomic_flag_test_and_set(
24330 volatile atomic_flag *object);
24331 bool atomic_flag_test_and_set_explicit(
24332 volatile atomic_flag *object, memory_order order);
24333 void atomic_flag_clear(volatile atomic_flag *object);
24334 void atomic_flag_clear_explicit(
24335 volatile atomic_flag *object, memory_order order);
24336 </pre>
24339 <pre>
24340 bool
24341 true
24342 false
24343 __bool_true_false_are_defined
24344 </pre>
24347 <pre>
24348 ptrdiff_t max_align_t NULL
24349 size_t wchar_t
24350 offsetof(type, member-designator)
24351 __STDC_WANT_LIB_EXT1__
24352 rsize_t
24353 </pre>
24356 <!--page 502 -->
24357 <pre>
24358 intN_t INT_LEASTN_MIN PTRDIFF_MAX
24359 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
24360 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
24361 uint_leastN_t INT_FASTN_MIN SIZE_MAX
24362 int_fastN_t INT_FASTN_MAX WCHAR_MIN
24363 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
24364 intptr_t INTPTR_MIN WINT_MIN
24365 uintptr_t INTPTR_MAX WINT_MAX
24366 intmax_t UINTPTR_MAX INTN_C(value)
24367 uintmax_t INTMAX_MIN UINTN_C(value)
24368 INTN_MIN INTMAX_MAX INTMAX_C(value)
24369 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
24370 UINTN_MAX PTRDIFF_MIN
24371 __STDC_WANT_LIB_EXT1__
24372 RSIZE_MAX
24373 </pre>
24376 <!--page 503 -->
24377 <!--page 504 -->
24378 <!--page 505 -->
24379 <pre>
24380 size_t _IOLBF FILENAME_MAX TMP_MAX
24381 FILE _IONBF L_tmpnam stderr
24382 fpos_t BUFSIZ SEEK_CUR stdin
24383 NULL EOF SEEK_END stdout
24384 _IOFBF FOPEN_MAX SEEK_SET
24385 int remove(const char *filename);
24386 int rename(const char *old, const char *new);
24387 FILE *tmpfile(void);
24388 char *tmpnam(char *s);
24389 int fclose(FILE *stream);
24390 int fflush(FILE *stream);
24391 FILE *fopen(const char * restrict filename,
24392 const char * restrict mode);
24393 FILE *freopen(const char * restrict filename,
24394 const char * restrict mode,
24395 FILE * restrict stream);
24396 void setbuf(FILE * restrict stream,
24397 char * restrict buf);
24398 int setvbuf(FILE * restrict stream,
24399 char * restrict buf,
24400 int mode, size_t size);
24401 int fprintf(FILE * restrict stream,
24402 const char * restrict format, ...);
24403 int fscanf(FILE * restrict stream,
24404 const char * restrict format, ...);
24405 int printf(const char * restrict format, ...);
24406 int scanf(const char * restrict format, ...);
24407 int snprintf(char * restrict s, size_t n,
24408 const char * restrict format, ...);
24409 int sprintf(char * restrict s,
24410 const char * restrict format, ...);
24411 int sscanf(const char * restrict s,
24412 const char * restrict format, ...);
24413 int vfprintf(FILE * restrict stream,
24414 const char * restrict format, va_list arg);
24415 int vfscanf(FILE * restrict stream,
24416 const char * restrict format, va_list arg);
24417 int vprintf(const char * restrict format, va_list arg);
24418 int vscanf(const char * restrict format, va_list arg);
24419 int vsnprintf(char * restrict s, size_t n,
24420 const char * restrict format, va_list arg);
24421 int vsprintf(char * restrict s,
24422 const char * restrict format, va_list arg);
24423 int vsscanf(const char * restrict s,
24424 const char * restrict format, va_list arg);
24425 int fgetc(FILE *stream);
24426 char *fgets(char * restrict s, int n,
24427 FILE * restrict stream);
24428 int fputc(int c, FILE *stream);
24429 int fputs(const char * restrict s,
24430 FILE * restrict stream);
24431 int getc(FILE *stream);
24432 int getchar(void);
24433 int putc(int c, FILE *stream); *
24434 int putchar(int c);
24435 int puts(const char *s);
24436 int ungetc(int c, FILE *stream);
24437 size_t fread(void * restrict ptr,
24438 size_t size, size_t nmemb,
24439 FILE * restrict stream);
24440 size_t fwrite(const void * restrict ptr,
24441 size_t size, size_t nmemb,
24442 FILE * restrict stream);
24443 int fgetpos(FILE * restrict stream,
24444 fpos_t * restrict pos);
24445 int fseek(FILE *stream, long int offset, int whence);
24446 int fsetpos(FILE *stream, const fpos_t *pos);
24447 long int ftell(FILE *stream);
24448 void rewind(FILE *stream);
24449 void clearerr(FILE *stream);
24450 int feof(FILE *stream);
24451 int ferror(FILE *stream);
24452 void perror(const char *s);
24453 __STDC_WANT_LIB_EXT1__
24454 L_tmpnam_s TMP_MAX_S errno_t rsize_t
24455 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
24456 errno_t tmpnam_s(char *s, rsize_t maxsize);
24457 errno_t fopen_s(FILE * restrict * restrict streamptr,
24458 const char * restrict filename,
24459 const char * restrict mode);
24460 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
24461 const char * restrict filename,
24462 const char * restrict mode,
24463 FILE * restrict stream);
24464 int fprintf_s(FILE * restrict stream,
24465 const char * restrict format, ...);
24466 int fscanf_s(FILE * restrict stream,
24467 const char * restrict format, ...);
24468 int printf_s(const char * restrict format, ...);
24469 int scanf_s(const char * restrict format, ...);
24470 int snprintf_s(char * restrict s, rsize_t n,
24471 const char * restrict format, ...);
24472 int sprintf_s(char * restrict s, rsize_t n,
24473 const char * restrict format, ...);
24474 int sscanf_s(const char * restrict s,
24475 const char * restrict format, ...);
24476 int vfprintf_s(FILE * restrict stream,
24477 const char * restrict format,
24478 va_list arg);
24479 int vfscanf_s(FILE * restrict stream,
24480 const char * restrict format,
24481 va_list arg);
24482 int vprintf_s(const char * restrict format,
24483 va_list arg);
24484 int vscanf_s(const char * restrict format,
24485 va_list arg);
24486 int vsnprintf_s(char * restrict s, rsize_t n,
24487 const char * restrict format,
24488 va_list arg);
24489 int vsprintf_s(char * restrict s, rsize_t n,
24490 const char * restrict format,
24491 va_list arg);
24492 int vsscanf_s(const char * restrict s,
24493 const char * restrict format,
24494 va_list arg);
24495 char *gets_s(char *s, rsize_t n);
24496 </pre>
24499 <!--page 506 -->
24500 <!--page 507 -->
24501 <pre>
24502 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
24503 wchar_t lldiv_t EXIT_SUCCESS
24504 div_t NULL RAND_MAX
24505 double atof(const char *nptr);
24506 int atoi(const char *nptr);
24507 long int atol(const char *nptr);
24508 long long int atoll(const char *nptr);
24509 double strtod(const char * restrict nptr,
24510 char ** restrict endptr);
24511 float strtof(const char * restrict nptr,
24512 char ** restrict endptr);
24513 long double strtold(const char * restrict nptr,
24514 char ** restrict endptr);
24515 long int strtol(const char * restrict nptr,
24516 char ** restrict endptr, int base);
24517 long long int strtoll(const char * restrict nptr,
24518 char ** restrict endptr, int base);
24519 unsigned long int strtoul(
24520 const char * restrict nptr,
24521 char ** restrict endptr, int base);
24522 unsigned long long int strtoull(
24523 const char * restrict nptr,
24524 char ** restrict endptr, int base);
24525 int rand(void);
24526 void srand(unsigned int seed);
24527 void *aligned_alloc(size_t alignment, size_t size);
24528 void *calloc(size_t nmemb, size_t size);
24529 void free(void *ptr);
24530 void *malloc(size_t size);
24531 void *realloc(void *ptr, size_t size);
24532 _Noreturn void abort(void);
24533 int atexit(void (*func)(void));
24534 int at_quick_exit(void (*func)(void));
24535 _Noreturn void exit(int status);
24536 _Noreturn void _Exit(int status);
24537 char *getenv(const char *name);
24538 _Noreturn void quick_exit(int status);
24539 int system(const char *string);
24540 void *bsearch(const void *key, const void *base,
24541 size_t nmemb, size_t size,
24542 int (*compar)(const void *, const void *));
24543 void qsort(void *base, size_t nmemb, size_t size,
24544 int (*compar)(const void *, const void *));
24545 int abs(int j);
24546 long int labs(long int j);
24547 long long int llabs(long long int j);
24548 div_t div(int numer, int denom);
24549 ldiv_t ldiv(long int numer, long int denom);
24550 lldiv_t lldiv(long long int numer,
24551 long long int denom);
24552 int mblen(const char *s, size_t n);
24553 int mbtowc(wchar_t * restrict pwc,
24554 const char * restrict s, size_t n);
24555 int wctomb(char *s, wchar_t wchar);
24556 size_t mbstowcs(wchar_t * restrict pwcs,
24557 const char * restrict s, size_t n);
24558 size_t wcstombs(char * restrict s,
24559 const wchar_t * restrict pwcs, size_t n);
24560 __STDC_WANT_LIB_EXT1__
24561 errno_t
24562 rsize_t
24563 constraint_handler_t
24564 constraint_handler_t set_constraint_handler_s(
24565 constraint_handler_t handler);
24566 void abort_handler_s(
24567 const char * restrict msg,
24568 void * restrict ptr,
24569 errno_t error);
24570 void ignore_handler_s(
24571 const char * restrict msg,
24572 void * restrict ptr,
24573 errno_t error);
24574 errno_t getenv_s(size_t * restrict len,
24575 char * restrict value, rsize_t maxsize,
24576 const char * restrict name);
24577 void *bsearch_s(const void *key, const void *base,
24578 rsize_t nmemb, rsize_t size,
24579 int (*compar)(const void *k, const void *y,
24580 void *context),
24581 void *context);
24582 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
24583 int (*compar)(const void *x, const void *y,
24584 void *context),
24585 void *context);
24586 errno_t wctomb_s(int * restrict status,
24587 char * restrict s,
24588 rsize_t smax,
24589 wchar_t wc);
24590 errno_t mbstowcs_s(size_t * restrict retval,
24591 wchar_t * restrict dst, rsize_t dstmax,
24592 const char * restrict src, rsize_t len);
24593 errno_t wcstombs_s(size_t * restrict retval,
24594 char * restrict dst, rsize_t dstmax,
24595 const wchar_t * restrict src, rsize_t len);
24596 </pre>
24599 <!--page 508 -->
24600 <!--page 509 -->
24601 <pre>
24602 size_t
24603 NULL
24604 void *memcpy(void * restrict s1,
24605 const void * restrict s2, size_t n);
24606 void *memmove(void *s1, const void *s2, size_t n);
24607 char *strcpy(char * restrict s1,
24608 const char * restrict s2);
24609 char *strncpy(char * restrict s1,
24610 const char * restrict s2, size_t n);
24611 char *strcat(char * restrict s1,
24612 const char * restrict s2);
24613 char *strncat(char * restrict s1,
24614 const char * restrict s2, size_t n);
24615 int memcmp(const void *s1, const void *s2, size_t n);
24616 int strcmp(const char *s1, const char *s2);
24617 int strcoll(const char *s1, const char *s2);
24618 int strncmp(const char *s1, const char *s2, size_t n);
24619 size_t strxfrm(char * restrict s1,
24620 const char * restrict s2, size_t n);
24621 void *memchr(const void *s, int c, size_t n);
24622 char *strchr(const char *s, int c);
24623 size_t strcspn(const char *s1, const char *s2);
24624 char *strpbrk(const char *s1, const char *s2);
24625 char *strrchr(const char *s, int c);
24626 size_t strspn(const char *s1, const char *s2);
24627 char *strstr(const char *s1, const char *s2);
24628 char *strtok(char * restrict s1,
24629 const char * restrict s2);
24630 void *memset(void *s, int c, size_t n);
24631 char *strerror(int errnum);
24632 size_t strlen(const char *s);
24633 __STDC_WANT_LIB_EXT1__
24634 errno_t
24635 rsize_t
24636 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
24637 const void * restrict s2, rsize_t n);
24638 errno_t memmove_s(void *s1, rsize_t s1max,
24639 const void *s2, rsize_t n);
24640 errno_t strcpy_s(char * restrict s1,
24641 rsize_t s1max,
24642 const char * restrict s2);
24643 errno_t strncpy_s(char * restrict s1,
24644 rsize_t s1max,
24645 const char * restrict s2,
24646 rsize_t n);
24647 errno_t strcat_s(char * restrict s1,
24648 rsize_t s1max,
24649 const char * restrict s2);
24650 errno_t strncat_s(char * restrict s1,
24651 rsize_t s1max,
24652 const char * restrict s2,
24653 rsize_t n);
24654 char *strtok_s(char * restrict s1,
24655 rsize_t * restrict s1max,
24656 const char * restrict s2,
24657 char ** restrict ptr);
24658 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
24659 errno_t strerror_s(char *s, rsize_t maxsize,
24660 errno_t errnum);
24661 size_t strerrorlen_s(errno_t errnum);
24662 size_t strnlen_s(const char *s, size_t maxsize);
24663 </pre>
24666 <pre>
24667 acos sqrt fmod nextafter
24668 asin fabs frexp nexttoward
24669 atan atan2 hypot remainder
24670 acosh cbrt ilogb remquo
24671 asinh ceil ldexp rint
24672 atanh copysign lgamma round
24673 cos erf llrint scalbn
24674 sin erfc llround scalbln
24675 tan exp2 log10 tgamma
24676 cosh expm1 log1p trunc
24677 sinh fdim log2 carg
24678 tanh floor logb cimag
24679 exp fma lrint conj
24680 log fmax lround cproj
24681 pow fmin nearbyint creal
24682 </pre>
24685 <!--page 510 -->
24686 <pre>
24687 ONCE_FLAG_INIT mtx_plain
24688 TSS_DTOR_ITERATIONS mtx_recursive
24689 cnd_t mtx_timed
24690 thrd_t mtx_try
24691 tss_t thrd_timeout
24692 mtx_t thrd_success
24693 tss_dtor_t thrd_busy
24694 thrd_start_t thrd_error
24695 once_flag thrd_nomem
24696 xtime
24697 void call_once(once_flag *flag, void (*func)(void));
24698 int cnd_broadcast(cnd_t *cond);
24699 void cnd_destroy(cnd_t *cond);
24700 int cnd_init(cnd_t *cond);
24701 int cnd_signal(cnd_t *cond);
24702 int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
24703 const xtime *xt);
24704 int cnd_wait(cnd_t *cond, mtx_t *mtx);
24705 void mtx_destroy(mtx_t *mtx);
24706 int mtx_init(mtx_t *mtx, int type);
24707 int mtx_lock(mtx_t *mtx);
24708 int mtx_timedlock(mtx_t *mtx, const xtime *xt);
24709 int mtx_trylock(mtx_t *mtx);
24710 int mtx_unlock(mtx_t *mtx);
24711 int thrd_create(thrd_t *thr, thrd_start_t func,
24712 void *arg);
24713 thrd_t thrd_current(void);
24714 int thrd_detach(thrd_t thr);
24715 int thrd_equal(thrd_t thr0, thrd_t thr1);
24716 void thrd_exit(int res);
24717 int thrd_join(thrd_t thr, int *res);
24718 void thrd_sleep(const xtime *xt);
24719 void thrd_yield(void);
24720 int tss_create(tss_t *key, tss_dtor_t dtor);
24721 void tss_delete(tss_t key);
24722 void *tss_get(tss_t key);
24723 int tss_set(tss_t key, void *val);
24724 int xtime_get(xtime *xt, int base);
24725 </pre>
24728 <!--page 511 -->
24729 <pre>
24730 NULL size_t time_t
24731 CLOCKS_PER_SEC clock_t struct tm
24732 clock_t clock(void);
24733 double difftime(time_t time1, time_t time0);
24734 time_t mktime(struct tm *timeptr);
24735 time_t time(time_t *timer);
24736 char *asctime(const struct tm *timeptr);
24737 char *ctime(const time_t *timer);
24738 struct tm *gmtime(const time_t *timer);
24739 struct tm *localtime(const time_t *timer);
24740 size_t strftime(char * restrict s,
24741 size_t maxsize,
24742 const char * restrict format,
24743 const struct tm * restrict timeptr);
24744 __STDC_WANT_LIB_EXT1__
24745 errno_t
24746 rsize_t
24747 errno_t asctime_s(char *s, rsize_t maxsize,
24748 const struct tm *timeptr);
24749 errno_t ctime_s(char *s, rsize_t maxsize,
24750 const time_t *timer);
24751 struct tm *gmtime_s(const time_t * restrict timer,
24752 struct tm * restrict result);
24753 struct tm *localtime_s(const time_t * restrict timer,
24754 struct tm * restrict result);
24755 </pre>
24758 <pre>
24759 mbstate_t size_t char16_t char32_t
24760 size_t mbrtoc16(char16_t * restrict pc16,
24761 const char * restrict s, size_t n,
24762 mbstate_t * restrict ps);
24763 size_t c16rtomb(char * restrict s, char16_t c16,
24764 mbstate_t * restrict ps);
24765 size_t mbrtoc32(char32_t * restrict pc32,
24766 const char * restrict s, size_t n,
24767 mbstate_t * restrict ps);
24768 size_t c32rtomb(char * restrict s, char32_t c32,
24769 mbstate_t * restrict ps);
24770 </pre>
24772 <h3><a name="B.27" href="#B.27">B.27 Extended multibyte/wide character utilities <wchar.h></a></h3>
24773 <!--page 512 -->
24774 <!--page 513 -->
24775 <!--page 514 -->
24776 <!--page 515 -->
24777 <!--page 516 -->
24778 <pre>
24779 wchar_t wint_t WCHAR_MAX
24780 size_t struct tm WCHAR_MIN
24781 mbstate_t NULL WEOF
24782 int fwprintf(FILE * restrict stream,
24783 const wchar_t * restrict format, ...);
24784 int fwscanf(FILE * restrict stream,
24785 const wchar_t * restrict format, ...);
24786 int swprintf(wchar_t * restrict s, size_t n,
24787 const wchar_t * restrict format, ...);
24788 int swscanf(const wchar_t * restrict s,
24789 const wchar_t * restrict format, ...);
24790 int vfwprintf(FILE * restrict stream,
24791 const wchar_t * restrict format, va_list arg);
24792 int vfwscanf(FILE * restrict stream,
24793 const wchar_t * restrict format, va_list arg);
24794 int vswprintf(wchar_t * restrict s, size_t n,
24795 const wchar_t * restrict format, va_list arg);
24796 int vswscanf(const wchar_t * restrict s,
24797 const wchar_t * restrict format, va_list arg);
24798 int vwprintf(const wchar_t * restrict format,
24799 va_list arg);
24800 int vwscanf(const wchar_t * restrict format,
24801 va_list arg);
24802 int wprintf(const wchar_t * restrict format, ...);
24803 int wscanf(const wchar_t * restrict format, ...);
24804 wint_t fgetwc(FILE *stream);
24805 wchar_t *fgetws(wchar_t * restrict s, int n,
24806 FILE * restrict stream);
24807 wint_t fputwc(wchar_t c, FILE *stream);
24808 int fputws(const wchar_t * restrict s,
24809 FILE * restrict stream);
24810 int fwide(FILE *stream, int mode);
24811 wint_t getwc(FILE *stream);
24812 wint_t getwchar(void);
24813 wint_t putwc(wchar_t c, FILE *stream);
24814 wint_t putwchar(wchar_t c);
24815 wint_t ungetwc(wint_t c, FILE *stream);
24816 double wcstod(const wchar_t * restrict nptr,
24817 wchar_t ** restrict endptr);
24818 float wcstof(const wchar_t * restrict nptr,
24819 wchar_t ** restrict endptr);
24820 long double wcstold(const wchar_t * restrict nptr,
24821 wchar_t ** restrict endptr);
24822 long int wcstol(const wchar_t * restrict nptr,
24823 wchar_t ** restrict endptr, int base);
24824 long long int wcstoll(const wchar_t * restrict nptr,
24825 wchar_t ** restrict endptr, int base);
24826 unsigned long int wcstoul(const wchar_t * restrict nptr,
24827 wchar_t ** restrict endptr, int base);
24828 unsigned long long int wcstoull(
24829 const wchar_t * restrict nptr,
24830 wchar_t ** restrict endptr, int base);
24831 wchar_t *wcscpy(wchar_t * restrict s1,
24832 const wchar_t * restrict s2);
24833 wchar_t *wcsncpy(wchar_t * restrict s1,
24834 const wchar_t * restrict s2, size_t n);
24835 wchar_t *wmemcpy(wchar_t * restrict s1,
24836 const wchar_t * restrict s2, size_t n);
24837 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
24838 size_t n);
24839 wchar_t *wcscat(wchar_t * restrict s1,
24840 const wchar_t * restrict s2);
24841 wchar_t *wcsncat(wchar_t * restrict s1,
24842 const wchar_t * restrict s2, size_t n);
24843 int wcscmp(const wchar_t *s1, const wchar_t *s2);
24844 int wcscoll(const wchar_t *s1, const wchar_t *s2);
24845 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
24846 size_t n);
24847 size_t wcsxfrm(wchar_t * restrict s1,
24848 const wchar_t * restrict s2, size_t n);
24849 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
24850 size_t n);
24851 wchar_t *wcschr(const wchar_t *s, wchar_t c);
24852 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
24853 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
24854 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
24855 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
24856 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
24857 wchar_t *wcstok(wchar_t * restrict s1,
24858 const wchar_t * restrict s2,
24859 wchar_t ** restrict ptr);
24860 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
24861 size_t wcslen(const wchar_t *s);
24862 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
24863 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
24864 const wchar_t * restrict format,
24865 const struct tm * restrict timeptr);
24866 wint_t btowc(int c);
24867 int wctob(wint_t c);
24868 int mbsinit(const mbstate_t *ps);
24869 size_t mbrlen(const char * restrict s, size_t n,
24870 mbstate_t * restrict ps);
24871 size_t mbrtowc(wchar_t * restrict pwc,
24872 const char * restrict s, size_t n,
24873 mbstate_t * restrict ps);
24874 size_t wcrtomb(char * restrict s, wchar_t wc,
24875 mbstate_t * restrict ps);
24876 size_t mbsrtowcs(wchar_t * restrict dst,
24877 const char ** restrict src, size_t len,
24878 mbstate_t * restrict ps);
24879 size_t wcsrtombs(char * restrict dst,
24880 const wchar_t ** restrict src, size_t len,
24881 mbstate_t * restrict ps);
24882 __STDC_WANT_LIB_EXT1__
24883 errno_t
24884 rsize_t
24885 int fwprintf_s(FILE * restrict stream,
24886 const wchar_t * restrict format, ...);
24887 int fwscanf_s(FILE * restrict stream,
24888 const wchar_t * restrict format, ...);
24889 int snwprintf_s(wchar_t * restrict s,
24890 rsize_t n,
24891 const wchar_t * restrict format, ...);
24892 int swprintf_s(wchar_t * restrict s, rsize_t n,
24893 const wchar_t * restrict format, ...);
24894 int swscanf_s(const wchar_t * restrict s,
24895 const wchar_t * restrict format, ...);
24896 int vfwprintf_s(FILE * restrict stream,
24897 const wchar_t * restrict format,
24898 va_list arg);
24899 int vfwscanf_s(FILE * restrict stream,
24900 const wchar_t * restrict format, va_list arg);
24901 int vsnwprintf_s(wchar_t * restrict s,
24902 rsize_t n,
24903 const wchar_t * restrict format,
24904 va_list arg);
24905 int vswprintf_s(wchar_t * restrict s,
24906 rsize_t n,
24907 const wchar_t * restrict format,
24908 va_list arg);
24909 int vswscanf_s(const wchar_t * restrict s,
24910 const wchar_t * restrict format,
24911 va_list arg);
24912 int vwprintf_s(const wchar_t * restrict format,
24913 va_list arg);
24914 int vwscanf_s(const wchar_t * restrict format,
24915 va_list arg);
24916 int wprintf_s(const wchar_t * restrict format, ...);
24917 int wscanf_s(const wchar_t * restrict format, ...);
24918 errno_t wcscpy_s(wchar_t * restrict s1,
24919 rsize_t s1max,
24920 const wchar_t * restrict s2);
24921 errno_t wcsncpy_s(wchar_t * restrict s1,
24922 rsize_t s1max,
24923 const wchar_t * restrict s2,
24924 rsize_t n);
24925 errno_t wmemcpy_s(wchar_t * restrict s1,
24926 rsize_t s1max,
24927 const wchar_t * restrict s2,
24928 rsize_t n);
24929 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
24930 const wchar_t *s2, rsize_t n);
24931 errno_t wcscat_s(wchar_t * restrict s1,
24932 rsize_t s1max,
24933 const wchar_t * restrict s2);
24934 errno_t wcsncat_s(wchar_t * restrict s1,
24935 rsize_t s1max,
24936 const wchar_t * restrict s2,
24937 rsize_t n);
24938 wchar_t *wcstok_s(wchar_t * restrict s1,
24939 rsize_t * restrict s1max,
24940 const wchar_t * restrict s2,
24941 wchar_t ** restrict ptr);
24942 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
24943 errno_t wcrtomb_s(size_t * restrict retval,
24944 char * restrict s, rsize_t smax,
24945 wchar_t wc, mbstate_t * restrict ps);
24946 errno_t mbsrtowcs_s(size_t * restrict retval,
24947 wchar_t * restrict dst, rsize_t dstmax,
24948 const char ** restrict src, rsize_t len,
24949 mbstate_t * restrict ps);
24950 errno_t wcsrtombs_s(size_t * restrict retval,
24951 char * restrict dst, rsize_t dstmax,
24952 const wchar_t ** restrict src, rsize_t len,
24953 mbstate_t * restrict ps);
24954 </pre>
24956 <h3><a name="B.28" href="#B.28">B.28 Wide character classification and mapping utilities <wctype.h></a></h3>
24957 <!--page 517 -->
24958 <pre>
24959 wint_t wctrans_t wctype_t WEOF
24960 int iswalnum(wint_t wc);
24961 int iswalpha(wint_t wc);
24962 int iswblank(wint_t wc);
24963 int iswcntrl(wint_t wc);
24964 int iswdigit(wint_t wc);
24965 int iswgraph(wint_t wc);
24966 int iswlower(wint_t wc);
24967 int iswprint(wint_t wc);
24968 int iswpunct(wint_t wc);
24969 int iswspace(wint_t wc);
24970 int iswupper(wint_t wc);
24971 int iswxdigit(wint_t wc);
24972 int iswctype(wint_t wc, wctype_t desc);
24973 wctype_t wctype(const char *property);
24974 wint_t towlower(wint_t wc);
24975 wint_t towupper(wint_t wc);
24976 wint_t towctrans(wint_t wc, wctrans_t desc);
24977 wctrans_t wctrans(const char *property);
24978 </pre>
24981 <pre>
24982 (informative)
24983 Sequence points
24984 </pre>
24987 <ul>
24988 <li> Between the evaluations of the function designator and actual arguments in a function
24990 <li> Between the evaluations of the first and second operands of the following operators:
24991 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>). *
24992 <li> Between the evaluations of the first operand of the conditional ? : operator and
24995 <li> Between the evaluation of a full expression and the next full expression to be
24996 evaluated. The following are full expressions: an initializer that is not part of a
24997 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
24998 controlling expression of a selection statement (if or switch) (<a href="#6.8.4">6.8.4</a>); the
24999 controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the (optional)
25000 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the (optional) expression in a return
25003 <li> After the actions associated with each formatted input/output function conversion
25005 <li> Immediately before and immediately after each call to a comparison function, and
25006 also between any call to a comparison function and any movement of the objects
25008 <!--page 518 -->
25009 </ul>
25012 <pre>
25013 (normative)
25014 Universal character names for identifiers
25015 </pre>
25017 This clause lists the hexadecimal code values that are valid in universal character names
25018 in identifiers.
25033 3040-D7FF
25035 F900-FD3D, FD40-FDCF, FDF0-FE44, FE47-FFFD
25039 B0000-BFFFD, C0000-CFFFD, D0000-DFFFD, E0000-EFFFD
25044 <!--page 519 -->
25047 <pre>
25048 (informative)
25049 Implementation limits
25050 </pre>
25052 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
25053 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
25054 with the same sign. The values shall all be constant expressions suitable for use in #if
25055 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
25056 <pre>
25057 #define CHAR_BIT 8
25058 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
25059 #define CHAR_MIN 0 or SCHAR_MIN
25060 #define INT_MAX +32767
25061 #define INT_MIN -32767
25062 #define LONG_MAX +2147483647
25063 #define LONG_MIN -2147483647
25064 #define LLONG_MAX +9223372036854775807
25065 #define LLONG_MIN -9223372036854775807
25066 #define MB_LEN_MAX 1
25067 #define SCHAR_MAX +127
25068 #define SCHAR_MIN -127
25069 #define SHRT_MAX +32767
25070 #define SHRT_MIN -32767
25071 #define UCHAR_MAX 255
25072 #define USHRT_MAX 65535
25073 #define UINT_MAX 65535
25074 #define ULONG_MAX 4294967295
25075 #define ULLONG_MAX 18446744073709551615
25076 </pre>
25078 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
25079 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
25080 directives; all floating values shall be constant expressions. The components are
25083 The values given in the following list shall be replaced by implementation-defined
25084 expressions:
25085 <pre>
25086 #define FLT_EVAL_METHOD
25087 #define FLT_ROUNDS
25088 </pre>
25090 The values given in the following list shall be replaced by implementation-defined
25091 constant expressions that are greater or equal in magnitude (absolute value) to those
25092 shown, with the same sign:
25093 <!--page 520 -->
25094 <pre>
25095 #define DLB_DECIMAL_DIG 10
25096 #define DBL_DIG 10
25097 #define DBL_MANT_DIG
25098 #define DBL_MAX_10_EXP +37
25099 #define DBL_MAX_EXP
25100 #define DBL_MIN_10_EXP -37
25101 #define DBL_MIN_EXP
25102 #define DECIMAL_DIG 10
25103 #define FLT_DECIMAL_DIG 6
25104 #define FLT_DIG 6
25105 #define FLT_MANT_DIG
25106 #define FLT_MAX_10_EXP +37
25107 #define FLT_MAX_EXP
25108 #define FLT_MIN_10_EXP -37
25109 #define FLT_MIN_EXP
25110 #define FLT_RADIX 2
25111 #define LDLB_DECIMAL_DIG 10
25112 #define LDBL_DIG 10
25113 #define LDBL_MANT_DIG
25114 #define LDBL_MAX_10_EXP +37
25115 #define LDBL_MAX_EXP
25116 #define LDBL_MIN_10_EXP -37
25117 #define LDBL_MIN_EXP
25118 </pre>
25120 The values given in the following list shall be replaced by implementation-defined
25121 constant expressions with values that are greater than or equal to those shown:
25122 <pre>
25123 #define DBL_MAX 1E+37
25124 #define FLT_MAX 1E+37
25125 #define LDBL_MAX 1E+37
25126 </pre>
25128 The values given in the following list shall be replaced by implementation-defined
25129 constant expressions with (positive) values that are less than or equal to those shown:
25130 <!--page 521 -->
25131 <pre>
25132 #define DBL_EPSILON 1E-9
25133 #define DBL_MIN 1E-37
25134 #define FLT_EPSILON 1E-5
25135 #define FLT_MIN 1E-37
25136 #define LDBL_EPSILON 1E-9
25137 #define LDBL_MIN 1E-37
25138 </pre>
25141 <pre>
25142 (normative)
25143 IEC 60559 floating-point arithmetic
25144 </pre>
25148 This annex specifies C language support for the IEC 60559 floating-point standard. The
25149 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
25154 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
25156 defines __STDC_IEC_559__ shall conform to the specifications in this annex.<sup><a href="#note343"><b>343)</b></a></sup>
25157 Where a binding between the C language and IEC 60559 is indicated, the
25158 IEC 60559-specified behavior is adopted by reference, unless stated otherwise. Since
25159 negative and positive infinity are representable in IEC 60559 formats, all real numbers lie
25160 within the range of representable values.
25163 <p><small><a name="note343" href="#note343">343)</a> Implementations that do not define __STDC_IEC_559__ are not required to conform to these
25164 specifications.
25165 </small>
25169 The C floating types match the IEC 60559 formats as follows:
25170 <ul>
25173 <li> The long double type matches an IEC 60559 extended format,<sup><a href="#note344"><b>344)</b></a></sup> else a
25175 </ul>
25176 Any non-IEC 60559 extended format used for the long double type shall have more
25177 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note345"><b>345)</b></a></sup>
25182 <!--page 522 -->
25185 The long double type should match an IEC 60559 extended format.
25188 <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
25190 </small>
25191 <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
25192 all double values.
25193 </small>
25197 This specification does not define the behavior of signaling NaNs.<sup><a href="#note346"><b>346)</b></a></sup> It generally uses
25198 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
25199 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
25202 <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
25203 sufficient for closure of the arithmetic.
25204 </small>
25208 C operators and functions provide IEC 60559 required and recommended facilities as
25209 listed below.
25210 <ul>
25212 divide operations.
25213 <li> The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
25214 <li> The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
25215 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
25216 with additional information.
25217 <li> The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
25218 floating-point number to an integer value (in the same precision). The nearbyint
25219 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
25220 Appendix to ANSI/IEEE 854.
25222 floating-point precisions.
25224 from integer to floating point.
25226 but always round toward zero.
25227 <li> The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
25228 conversions, which honor the directed rounding mode, from floating point to the
25229 long int and long long int integer formats. The lrint and llrint
25230 functions can be used to implement IEC 60559 conversions from floating to other
25231 integer formats.
25232 <li> The translation time conversion of floating constants and the strtod, strtof,
25233 strtold, fprintf, fscanf, and related library functions in <a href="#7.22"><stdlib.h></a>,
25236 <!--page 523 -->
25237 <a href="#7.21"><stdio.h></a>, and <a href="#7.28"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
25238 strtold function in <a href="#7.22"><stdlib.h></a> provides the conv function recommended in the
25239 Appendix to ANSI/IEEE 854.
25241 identifies a need for additional comparison predicates to facilitate writing code that
25242 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
25244 supplement the language operators to address this need. The islessgreater and
25245 isunordered macros provide respectively a quiet version of the <> predicate and
25246 the unordered predicate recommended in the Appendix to IEC 60559.
25247 <li> The feclearexcept, feraiseexcept, and fetestexcept functions in
25248 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
25249 exception status flags. The fegetexceptflag and fesetexceptflag
25250 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
25251 one time. These functions are used in conjunction with the type fexcept_t and the
25252 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
25254 <li> The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
25255 to select among the IEC 60559 directed rounding modes represented by the rounding
25258 IEC 60559 directed rounding modes.
25259 <li> The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
25260 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
25261 the IEC 60559 status flags and control modes.
25262 <li> The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
25263 recommended in the Appendix to IEC 60559.
25264 <li> The fabs functions in <a href="#7.12"><math.h></a> provide the abs function recommended in the
25265 Appendix to IEC 60559.
25266 <li> The unary minus (-) operator provides the unary minus (-) operation recommended
25267 in the Appendix to IEC 60559.
25268 <li> The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
25269 recommended in the Appendix to IEC 60559.
25270 <li> The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
25272 <li> The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
25273 function recommended in the Appendix to IEC 60559 (but with a minor change to
25274 <!--page 524 -->
25275 better handle signed zeros).
25276 <li> The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
25277 the Appendix to IEC 60559.
25278 <li> The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
25279 Appendix to IEC 60559.
25280 <li> The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
25281 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
25282 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
25283 function recommended in the Appendix to IEC 60559 (except that the classification
25285 </ul>
25289 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
25290 (even for NaN). Otherwise, if the floating value is infinite or NaN or if the integral part
25291 of the floating value exceeds the range of the integer type, then the ''invalid'' floating-
25292 point exception is raised and the resulting value is unspecified. Otherwise, the resulting
25293 value is determined by <a href="#6.3.1.4">6.3.1.4</a>. Conversion of an integral floating value that does not
25294 exceed the range of the integer type raises no floating-point exceptions; whether
25295 conversion of a non-integral floating value raises the ''inexact'' floating-point exception is
25299 <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
25300 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
25301 cases where it matters, library functions can be used to effect such conversions with or without raising
25302 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
25304 </small>
25308 Conversion from the widest supported IEC 60559 format to decimal with
25309 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note348"><b>348)</b></a></sup>
25311 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
25312 particular, conversion between any supported IEC 60559 format and decimal with
25313 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
25314 rounding mode), which assures that conversion from the widest supported IEC 60559
25315 format to decimal with DECIMAL_DIG digits and back is the identity function.
25319 <!--page 525 -->
25321 Functions such as strtod that convert character sequences to floating types honor the
25322 rounding direction. Hence, if the rounding direction might be upward or downward, the
25323 implementation cannot convert a minus-signed sequence by negating the converted
25324 unsigned sequence.
25327 <p><small><a name="note348" href="#note348">348)</a> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
25331 </small>
25334 If the return expression is evaluated in a floating-point format different from the return
25335 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
25336 and the resulting value is returned to the caller.
25339 <p><small><a name="note349" href="#note349">349)</a> Assignment removes any extra range and precision.
25340 </small>
25344 A contracted expression is correctly rounded (once) and treats infinities, NaNs, signed
25345 zeros, subnormals, and the rounding directions in a manner consistent with the basic
25346 arithmetic operations covered by IEC 60559.
25349 A contracted expression should raise floating-point exceptions in a manner generally
25350 consistent with the basic arithmetic operations. *
25354 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
25355 point exception status flags and directed-rounding control modes. It includes also
25356 IEC 60559 dynamic rounding precision and trap enablement modes, if the
25360 <p><small><a name="note350" href="#note350">350)</a> This specification does not require dynamic rounding precision nor trap enablement modes.
25361 </small>
25365 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
25366 status flags, and that rounding control modes can be set explicitly to affect result values of
25367 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
25368 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
25374 <!--page 526 -->
25377 <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-
25378 point control modes will be the default ones and the floating-point status flags will not be tested,
25380 </small>
25384 During translation the IEC 60559 default modes are in effect:
25385 <ul>
25386 <li> The rounding direction mode is rounding to nearest.
25387 <li> The rounding precision mode (if supported) is set so that results are not shortened.
25388 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
25389 </ul>
25392 The implementation should produce a diagnostic message for each translation-time
25393 floating-point exception, other than ''inexact'';<sup><a href="#note352"><b>352)</b></a></sup> the implementation should then
25394 proceed with the translation of the program.
25397 <p><small><a name="note352" href="#note352">352)</a> As floating constants are converted to appropriate internal representations at translation time, their
25398 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
25399 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
25400 strtod, provide execution-time conversion of numeric strings.
25401 </small>
25405 At program startup the floating-point environment is initialized as prescribed by
25406 IEC 60559:
25407 <ul>
25408 <li> All floating-point exception status flags are cleared.
25409 <li> The rounding direction mode is rounding to nearest.
25410 <li> The dynamic rounding precision mode (if supported) is set so that results are not
25411 shortened.
25412 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
25413 </ul>
25417 An arithmetic constant expression of floating type, other than one in an initializer for an
25418 object that has static or thread storage duration, is evaluated (as if) during execution; thus,
25419 it is affected by any operative floating-point control modes and raises floating-point
25420 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
25423 EXAMPLE
25427 <!--page 527 -->
25428 <pre>
25430 #pragma STDC FENV_ACCESS ON
25431 void f(void)
25432 {
25437 /* ... */
25438 }
25439 </pre>
25441 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
25442 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
25443 execution time.
25447 <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
25450 efficiency of translation-time evaluation through static initialization, such as
25452 <pre>
25454 </pre>
25455 </small>
25459 All computation for automatic initialization is done (as if) at execution time; thus, it is
25460 affected by any operative modes and raises floating-point exceptions as required by
25461 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
25462 for initialization of objects that have static or thread storage duration is done (as if) at
25463 translation time.
25465 EXAMPLE
25466 <pre>
25468 #pragma STDC FENV_ACCESS ON
25469 void f(void)
25470 {
25471 float u[] = { 1.1e75 }; // raises exceptions
25472 static float v = 1.1e75; // does not raise exceptions
25473 float w = 1.1e75; // raises exceptions
25474 double x = 1.1e75; // may raise exceptions
25475 float y = 1.1e75f; // may raise exceptions
25476 long double z = 1.1e75; // does not raise exceptions
25477 /* ... */
25478 }
25479 </pre>
25481 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
25482 done at translation time. The automatic initialization of u and w require an execution-time conversion to
25483 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
25484 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
25485 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
25486 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
25487 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
25491 <!--page 528 -->
25492 their internal representations occur at translation time in all cases.
25496 <p><small><a name="note354" href="#note354">354)</a> Use of float_t and double_t variables increases the likelihood of translation-time computation.
25497 For example, the automatic initialization
25499 <pre>
25500 double_t x = 1.1e75;
25501 </pre>
25502 could be done at translation time, regardless of the expression evaluation method.
25503 </small>
25507 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
25508 change floating-point status flags and control modes just as indicated by their
25509 specifications (including conformance to IEC 60559). They do not change flags or modes
25510 (so as to be detectable by the user) in any other cases.
25512 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
25513 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
25514 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
25515 before ''inexact''.
25519 This section identifies code transformations that might subvert IEC 60559-specified
25520 behavior, and others that do not.
25524 Floating-point arithmetic operations and external function calls may entail side effects
25525 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
25526 ''on''. The flags and modes in the floating-point environment may be regarded as global
25527 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
25528 flags.
25530 Concern about side effects may inhibit code motion and removal of seemingly useless
25531 code. For example, in
25532 <pre>
25534 #pragma STDC FENV_ACCESS ON
25535 void f(double x)
25536 {
25537 /* ... */
25539 /* ... */
25540 }
25541 </pre>
25542 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
25544 course these optimizations are valid if the implementation can rule out the nettlesome
25545 cases.)
25547 This specification does not require support for trap handlers that maintain information
25548 about the order or count of floating-point exceptions. Therefore, between function calls,
25549 floating-point exceptions need not be precise: the actual order and number of occurrences
25551 <!--page 529 -->
25552 the preceding loop could be treated as
25553 <pre>
25555 </pre>
25560 <pre>
25561 generally do not yield numerically equivalent expressions, if the
25562 constants are exact then such transformations can be made on
25563 IEC 60559 machines and others that round perfectly.
25564 </pre>
25566 <pre>
25568 </pre>
25570 <pre>
25571 infinite, or NaN.
25572 </pre>
25574 <pre>
25575 IEC 60559 machines, among others).
25576 </pre>
25578 <pre>
25579 is +0 but -(1 - 1) is -0 (in the default rounding direction).<sup><a href="#note356"><b>356)</b></a></sup>
25580 </pre>
25582 <pre>
25583 infinite.
25584 </pre>
25586 <pre>
25587 infinite, or -0.
25588 </pre>
25590 <pre>
25592 </pre>
25594 <pre>
25596 FENV_ACCESS pragma is ''off'', promising default rounding, then
25597 the implementation can replace x - 0 by x, even if x might be zero.
25598 </pre>
25600 <pre>
25602 downward).
25603 </pre>
25605 <!--page 530 -->
25608 <p><small><a name="note355" href="#note355">355)</a> Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
25609 other transformations that remove arithmetic operators.
25610 </small>
25611 <p><small><a name="note356" href="#note356">356)</a> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
25612 Examples include:
25614 <pre>
25616 </pre>
25617 and
25619 <pre>
25620 conj(csqrt(z)) is csqrt(conj(z)),
25621 </pre>
25622 for complex z.
25623 </small>
25627 x != x -> false The expression x != x is true if x is a NaN.
25628 x = x -> true The expression x = x is false if x is a NaN.
25629 x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically equal, these
25630 <pre>
25631 expressions are not equivalent because of side effects when x or y is a
25632 NaN and the state of the FENV_ACCESS pragma is ''on''. This
25633 transformation, which would be desirable if extra code were required
25634 to cause the ''invalid'' floating-point exception for unordered cases,
25635 could be performed provided the state of the FENV_ACCESS pragma
25636 is ''off''.
25637 </pre>
25638 The sense of relational operators shall be maintained. This includes handling unordered
25639 cases as expressed by the source code.
25641 EXAMPLE
25642 <pre>
25643 // calls g and raises ''invalid'' if a and b are unordered
25644 if (a < b)
25645 f();
25646 else
25647 g();
25648 </pre>
25649 is not equivalent to
25650 <pre>
25651 // calls f and raises ''invalid'' if a and b are unordered
25652 if (a >= b)
25653 g();
25654 else
25655 f();
25656 </pre>
25657 nor to
25658 <pre>
25659 // calls f without raising ''invalid'' if a and b are unordered
25660 if (isgreaterequal(a,b))
25661 g();
25662 else
25663 f();
25664 </pre>
25665 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
25666 <pre>
25667 // calls g without raising ''invalid'' if a and b are unordered
25668 if (isless(a,b))
25669 f();
25670 else
25671 g();
25672 </pre>
25673 but is equivalent to
25674 <!--page 531 -->
25675 <pre>
25676 if (!(a < b))
25677 g();
25678 else
25679 f();
25680 </pre>
25685 The implementation shall honor floating-point exceptions raised by execution-time
25686 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.8.4">F.8.4</a>
25687 and <a href="#F.8.5">F.8.5</a>.) An operation on constants that raises no floating-point exception can be
25688 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
25689 further check is required to assure that changing the rounding direction to downward does
25690 not alter the sign of the result,<sup><a href="#note357"><b>357)</b></a></sup> and implementations that support dynamic rounding
25691 precision modes shall assure further that the result of the operation raises no floating-
25692 point exception when converted to the semantic type of the operation.
25695 <p><small><a name="note357" href="#note357">357)</a> 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
25696 </small>
25700 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
25701 for IEC 60559 implementations.
25703 The Standard C macro HUGE_VAL and its float and long double analogs,
25704 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
25705 infinities.
25707 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
25708 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
25709 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
25710 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
25711 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
25713 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
25714 nonzero value.
25716 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
25717 subsequent subclauses of this annex.
25719 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
25720 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
25721 whose magnitude is too large.
25723 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
25727 <!--page 532 -->
25729 Whether or when library functions raise the ''inexact'' floating-point exception is
25730 unspecified, unless explicitly specified otherwise.
25732 Whether or when library functions raise an undeserved ''underflow'' floating-point
25733 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
25734 not raise spurious floating-point exceptions (detectable by the user), other than the
25735 ''inexact'' floating-point exception.
25737 Whether the functions honor the rounding direction mode is implementation-defined,
25738 unless explicitly specified otherwise.
25740 Functions with a NaN argument return a NaN result and raise no floating-point exception,
25741 except where stated otherwise.
25743 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
25744 For families of functions, the specifications apply to all of the functions even though only
25745 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
25746 occurs in both an argument and the result, the result has the same sign as the argument.
25749 If a function with one or more NaN arguments returns a NaN result, the result should be
25750 the same as one of the NaN arguments (after possible type conversion), except perhaps
25751 for the sign.
25754 <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
25755 when the floating-point exception is raised.
25756 </small>
25757 <p><small><a name="note359" href="#note359">359)</a> It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
25758 avoiding them would be too costly.
25759 </small>
25765 <ul>
25767 <li> acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
25769 </ul>
25773 <ul>
25775 <li> asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
25781 <!--page 533 -->
25782 </ul>
25786 <ul>
25789 </ul>
25793 <ul>
25805 </ul>
25808 <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
25809 the ''divide-by-zero'' floating-point exception.
25810 </small>
25814 <ul>
25816 <li> cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
25817 </ul>
25821 <ul>
25823 <li> sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
25824 </ul>
25828 <ul>
25830 <li> tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
25835 <!--page 534 -->
25836 </ul>
25842 <ul>
25845 <li> acosh(+(inf)) returns +(inf).
25846 </ul>
25850 <ul>
25852 <li> asinh((+-)(inf)) returns (+-)(inf).
25853 </ul>
25857 <ul>
25859 <li> atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
25860 <li> atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
25862 </ul>
25866 <ul>
25868 <li> cosh((+-)(inf)) returns +(inf).
25869 </ul>
25873 <ul>
25875 <li> sinh((+-)(inf)) returns (+-)(inf).
25876 </ul>
25880 <ul>
25883 </ul>
25889 <ul>
25892 <li> exp(+(inf)) returns +(inf).
25893 <!--page 535 -->
25894 </ul>
25898 <ul>
25901 <li> exp2(+(inf)) returns +(inf).
25902 </ul>
25906 <ul>
25909 <li> expm1(+(inf)) returns +(inf).
25910 </ul>
25914 <ul>
25916 <li> frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
25917 pointed to by exp.
25918 <li> frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
25919 (and returns a NaN).
25920 </ul>
25922 frexp raises no floating-point exceptions.
25924 When the radix of the argument is a power of 2, the returned value is exact and is
25925 independent of the current rounding direction mode.
25927 On a binary system, the body of the frexp function might be
25928 <pre>
25929 {
25931 return scalbn(value, -(*exp));
25932 }
25933 </pre>
25937 When the correct result is representable in the range of the return type, the returned value
25938 is exact and is independent of the current rounding direction mode.
25940 If the correct result is outside the range of the return type, the numeric result is
25941 unspecified and the ''invalid'' floating-point exception is raised.
25942 <!--page 536 -->
25946 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
25950 <ul>
25954 <li> log(+(inf)) returns +(inf).
25955 </ul>
25959 <ul>
25963 <li> log10(+(inf)) returns +(inf).
25964 </ul>
25968 <ul>
25971 <li> log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
25973 <li> log1p(+(inf)) returns +(inf).
25974 </ul>
25978 <ul>
25982 <li> log2(+(inf)) returns +(inf).
25983 </ul>
25987 <ul>
25989 <li> logb((+-)(inf)) returns +(inf).
25990 </ul>
25992 The returned value is exact and is independent of the current rounding direction mode.
25993 <!--page 537 -->
25997 <ul>
25998 <li> modf((+-)x, iptr) returns a result with the same sign as x.
25999 <li> modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
26000 <li> modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
26001 NaN).
26002 </ul>
26004 The returned values are exact and are independent of the current rounding direction
26005 mode.
26007 modf behaves as though implemented by
26008 <pre>
26011 #pragma STDC FENV_ACCESS ON
26012 double modf(double value, double *iptr)
26013 {
26014 int save_round = fegetround();
26015 fesetround(FE_TOWARDZERO);
26016 *iptr = nearbyint(value);
26017 fesetround(save_round);
26018 return copysign(
26019 isinf(value) ? 0.0 :
26020 value - (*iptr), value);
26021 }
26022 </pre>
26026 <ul>
26029 <li> scalbn((+-)(inf), n) returns (+-)(inf).
26030 </ul>
26032 If the calculation does not overflow or underflow, the returned value is exact and
26033 independent of the current rounding direction mode.
26034 <!--page 538 -->
26040 <ul>
26042 <li> cbrt((+-)(inf)) returns (+-)(inf).
26043 </ul>
26047 <ul>
26049 <li> fabs((+-)(inf)) returns +(inf).
26050 </ul>
26052 The returned value is exact and is independent of the current rounding direction mode.
26056 <ul>
26057 <li> hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
26059 <li> hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
26060 </ul>
26064 <ul>
26065 <li> pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
26070 exception.
26076 <li> pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
26082 <!--page 539 -->
26089 </ul>
26093 sqrt is fully specified as a basic arithmetic operation in IEC 60559. The returned value
26094 is dependent on the current rounding direction mode.
26100 <ul>
26103 </ul>
26107 <ul>
26110 </ul>
26114 <ul>
26117 <li> lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
26118 x a negative integer or zero.
26119 <li> lgamma(-(inf)) returns +(inf).
26120 <li> lgamma(+(inf)) returns +(inf).
26121 </ul>
26125 <ul>
26126 <li> tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
26127 <li> tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
26128 negative integer.
26129 <li> tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
26130 <li> tgamma(+(inf)) returns +(inf).
26131 <!--page 540 -->
26132 </ul>
26138 <ul>
26140 <li> ceil((+-)(inf)) returns (+-)(inf).
26141 </ul>
26143 The returned value is independent of the current rounding direction mode.
26145 The double version of ceil behaves as though implemented by
26146 <pre>
26149 #pragma STDC FENV_ACCESS ON
26150 double ceil(double x)
26151 {
26152 double result;
26153 int save_round = fegetround();
26154 fesetround(FE_UPWARD);
26155 result = rint(x); // or nearbyint instead of rint
26156 fesetround(save_round);
26157 return result;
26158 }
26159 </pre>
26161 The ceil functions may, but are not required to, raise the ''inexact'' floating-point
26162 exception for finite non-integer arguments, as this implementation does.
26166 <ul>
26168 <li> floor((+-)(inf)) returns (+-)(inf).
26169 </ul>
26171 The returned value and is independent of the current rounding direction mode.
26173 See the sample implementation for ceil in <a href="#F.10.6.1">F.10.6.1</a>. The floor functions may, but are
26174 not required to, raise the ''inexact'' floating-point exception for finite non-integer
26175 arguments, as that implementation does.
26179 The nearbyint functions use IEC 60559 rounding according to the current rounding
26180 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
26181 value from the argument.
26182 <ul>
26184 <li> nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
26185 <!--page 541 -->
26186 </ul>
26190 The rint functions differ from the nearbyint functions only in that they do raise the
26191 ''inexact'' floating-point exception if the result differs in value from the argument.
26195 The lrint and llrint functions provide floating-to-integer conversion as prescribed
26196 by IEC 60559. They round according to the current rounding direction. If the rounded
26197 value is outside the range of the return type, the numeric result is unspecified and the
26198 ''invalid'' floating-point exception is raised. When they raise no other floating-point
26199 exception and the result differs from the argument, they raise the ''inexact'' floating-point
26200 exception.
26204 <ul>
26206 <li> round((+-)(inf)) returns (+-)(inf).
26207 </ul>
26209 The returned value is independent of the current rounding direction mode.
26211 The double version of round behaves as though implemented by
26212 <pre>
26215 #pragma STDC FENV_ACCESS ON
26216 double round(double x)
26217 {
26218 double result;
26219 fenv_t save_env;
26220 feholdexcept(&save_env);
26221 result = rint(x);
26222 if (fetestexcept(FE_INEXACT)) {
26223 fesetround(FE_TOWARDZERO);
26224 result = rint(copysign(0.5 + fabs(x), x));
26225 }
26226 feupdateenv(&save_env);
26227 return result;
26228 }
26229 </pre>
26230 The round functions may, but are not required to, raise the ''inexact'' floating-point
26231 exception for finite non-integer numeric arguments, as this implementation does.
26232 <!--page 542 -->
26236 The lround and llround functions differ from the lrint and llrint functions
26237 with the default rounding direction just in that the lround and llround functions
26238 round halfway cases away from zero and need not raise the ''inexact'' floating-point
26239 exception for non-integer arguments that round to within the range of the return type.
26243 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
26244 rounding direction). The returned value is exact.
26245 <ul>
26247 <li> trunc((+-)(inf)) returns (+-)(inf).
26248 </ul>
26250 The returned value is independent of the current rounding direction mode. The trunc
26251 functions may, but are not required to, raise the ''inexact'' floating-point exception for
26252 finite non-integer arguments.
26258 <ul>
26260 <li> fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
26261 infinite or y zero (and neither is a NaN).
26262 <li> fmod(x, (+-)(inf)) returns x for x not infinite.
26263 </ul>
26265 When subnormal results are supported, the returned value is exact and is independent of
26266 the current rounding direction mode.
26268 The double version of fmod behaves as though implemented by
26269 <!--page 543 -->
26270 <pre>
26273 #pragma STDC FENV_ACCESS ON
26274 double fmod(double x, double y)
26275 {
26276 double result;
26277 result = remainder(fabs(x), (y = fabs(y)));
26278 if (signbit(result)) result += y;
26279 return copysign(result, x);
26280 }
26281 </pre>
26285 The remainder functions are fully specified as a basic arithmetic operation in
26286 IEC 60559.
26288 When subnormal results are supported, the returned value is exact and is independent of
26289 the current rounding direction mode.
26293 The remquo functions follow the specifications for the remainder functions. They
26294 have no further specifications special to IEC 60559 implementations.
26296 When subnormal results are supported, the returned value is exact and is independent of
26297 the current rounding direction mode.
26303 copysign is specified in the Appendix to IEC 60559.
26305 The returned value is exact and is independent of the current rounding direction mode.
26309 All IEC 60559 implementations support quiet NaNs, in all floating formats.
26311 The returned value is exact and is independent of the current rounding direction mode.
26315 <ul>
26316 <li> nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
26317 for x finite and the function value infinite.
26318 <li> nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
26319 exceptions for the function value subnormal or zero and x != y.
26320 </ul>
26322 Even though underflow or overflow can occur, the returned value is independent of the
26323 current rounding direction mode.
26327 No additional requirements beyond those on nextafter.
26329 Even though underflow or overflow can occur, the returned value is independent of the
26330 current rounding direction mode.
26331 <!--page 544 -->
26333 <h4><a name="F.10.9" href="#F.10.9">F.10.9 Maximum, minimum, and positive difference functions</a></h4>
26337 No additional requirements.
26341 If just one argument is a NaN, the fmax functions return the other argument (if both
26342 arguments are NaNs, the functions return a NaN).
26344 The returned value is exact and is independent of the current rounding direction mode.
26347 <pre>
26348 { return (isgreaterequal(x, y) ||
26349 isnan(y)) ? x : y; }
26350 </pre>
26353 <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
26354 return +0; however, implementation in software might be impractical.
26355 </small>
26359 The fmin functions are analogous to the fmax functions (see <a href="#F.10.9.2">F.10.9.2</a>).
26361 The returned value is exact and is independent of the current rounding direction mode.
26367 <ul>
26368 <li> fma(x, y, z) computes xy + z, correctly rounded once.
26369 <li> fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
26370 exception if one of x and y is infinite, the other is zero, and z is a NaN.
26371 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
26372 one of x and y is infinite, the other is zero, and z is not a NaN.
26373 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
26374 times y is an exact infinity and z is also an infinity but with the opposite sign.
26379 <!--page 545 -->
26380 </ul>
26384 Relational operators and their corresponding comparison macros (<a href="#7.12.14">7.12.14</a>) produce
26385 equivalent result values, even if argument values are represented in wider formats. Thus,
26386 comparison macro arguments represented in formats wider than their semantic types are
26387 not converted to the semantic types, unless the wide evaluation method converts operands
26388 of relational operators to their semantic types. The standard wide evaluation methods
26389 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
26390 operands of relational operators to their semantic types.
26391 <!--page 546 -->
26394 <pre>
26395 (normative)
26396 IEC 60559-compatible complex arithmetic
26397 </pre>
26401 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
26402 IEC 60559 real floating-point arithmetic. An implementation that defines *
26403 __STDC_IEC_559_COMPLEX__ shall conform to the specifications in this annex.<sup><a href="#note362"><b>362)</b></a></sup>
26406 <p><small><a name="note362" href="#note362">362)</a> Implementations that do not define __STDC_IEC_559_COMPLEX__ are not required to conform
26407 to these specifications.
26408 </small>
26412 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
26413 used as a type specifier within declaration specifiers in the same way as _Complex is
26414 (thus, _Imaginary float is a valid type name).
26416 There are three imaginary types, designated as float _Imaginary, double
26417 _Imaginary, and long double _Imaginary. The imaginary types (along with
26418 the real floating and complex types) are floating types.
26420 For imaginary types, the corresponding real type is given by deleting the keyword
26421 _Imaginary from the type name.
26423 Each imaginary type has the same representation and alignment requirements as the
26424 corresponding real type. The value of an object of imaginary type is the value of the real
26425 representation times the imaginary unit.
26427 The imaginary type domain comprises the imaginary types.
26431 A complex or imaginary value with at least one infinite part is regarded as an infinity
26432 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
26433 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
26434 a zero if each of its parts is a zero.
26439 <!--page 547 -->
26445 Conversions among imaginary types follow rules analogous to those for real floating
26446 types.
26450 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
26451 result is a positive zero.
26453 When a value of real type is converted to an imaginary type, the result is a positive
26454 imaginary zero.
26458 </small>
26462 When a value of imaginary type is converted to a complex type, the real part of the
26463 complex result value is a positive zero and the imaginary part of the complex result value
26464 is determined by the conversion rules for the corresponding real types.
26466 When a value of complex type is converted to an imaginary type, the real part of the
26467 complex value is discarded and the value of the imaginary part is converted according to
26468 the conversion rules for the corresponding real types.
26472 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
26473 operation with an imaginary operand.
26475 For most operand types, the value of the result of a binary operator with an imaginary or
26476 complex operand is completely determined, with reference to real arithmetic, by the usual
26477 mathematical formula. For some operand types, the usual mathematical formula is
26478 problematic because of its treatment of infinities and because of undue overflow or
26479 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
26480 not completely determined.
26485 <!--page 548 -->
26490 If one operand has real type and the other operand has imaginary type, then the result has
26491 imaginary type. If both operands have imaginary type, then the result has real type. (If
26492 either operand has complex type, then the result has complex type.)
26494 If the operands are not both complex, then the result and floating-point exception
26495 behavior of the * operator is defined by the usual mathematical formula:
26496 <pre>
26497 * u iv u + iv
26498 </pre>
26500 <pre>
26501 x xu i(xv) (xu) + i(xv)
26502 </pre>
26504 <pre>
26505 iy i(yu) -yv (-yv) + i(yu)
26506 </pre>
26508 <pre>
26509 x + iy (xu) + i(yu) (-yv) + i(xv)
26510 </pre>
26512 If the second operand is not complex, then the result and floating-point exception
26513 behavior of the / operator is defined by the usual mathematical formula:
26514 <pre>
26515 / u iv
26516 </pre>
26518 <pre>
26519 x x/u i(-x/v)
26520 </pre>
26522 <pre>
26523 iy i(y/u) y/v
26524 </pre>
26526 <pre>
26527 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)
26528 </pre>
26530 The * and / operators satisfy the following infinity properties for all real, imaginary, and
26532 <ul>
26533 <li> if one operand is an infinity and the other operand is a nonzero finite number or an
26534 infinity, then the result of the * operator is an infinity;
26535 <li> if the first operand is an infinity and the second operand is a finite number, then the
26536 result of the / operator is an infinity;
26537 <li> if the first operand is a finite number and the second operand is an infinity, then the
26538 result of the / operator is a zero;
26543 <!--page 549 -->
26544 <li> if the first operand is a nonzero finite number or an infinity and the second operand is
26545 a zero, then the result of the / operator is an infinity.
26546 </ul>
26548 If both operands of the * operator are complex or if the second operand of the / operator
26549 is complex, the operator raises floating-point exceptions if appropriate for the calculation
26550 of the parts of the result, and may raise spurious floating-point exceptions.
26552 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
26554 <!--page 550 -->
26555 <pre>
26558 /* Multiply z * w ... */
26559 double complex _Cmultd(double complex z, double complex w)
26560 {
26561 #pragma STDC FP_CONTRACT OFF
26562 double a, b, c, d, ac, bd, ad, bc, x, y;
26563 a = creal(z); b = cimag(z);
26564 c = creal(w); d = cimag(w);
26565 ac = a * c; bd = b * d;
26566 ad = a * d; bc = b * c;
26567 x = ac - bd; y = ad + bc;
26568 if (isnan(x) && isnan(y)) {
26569 /* Recover infinities that computed as NaN+iNaN ... */
26570 int recalc = 0;
26571 if ( isinf(a) || isinf(b) ) { // z is infinite
26575 if (isnan(c)) c = copysign(0.0, c);
26576 if (isnan(d)) d = copysign(0.0, d);
26577 recalc = 1;
26578 }
26579 if ( isinf(c) || isinf(d) ) { // w is infinite
26583 if (isnan(a)) a = copysign(0.0, a);
26584 if (isnan(b)) b = copysign(0.0, b);
26585 recalc = 1;
26586 }
26587 if (!recalc && (isinf(ac) || isinf(bd) ||
26588 isinf(ad) || isinf(bc))) {
26589 /* Recover infinities from overflow by changing NaNs to 0 ... */
26590 if (isnan(a)) a = copysign(0.0, a);
26591 if (isnan(b)) b = copysign(0.0, b);
26592 if (isnan(c)) c = copysign(0.0, c);
26593 if (isnan(d)) d = copysign(0.0, d);
26594 recalc = 1;
26595 }
26596 if (recalc) {
26597 x = INFINITY * ( a * c - b * d );
26598 y = INFINITY * ( a * d + b * c );
26599 }
26600 }
26601 return x + I * y;
26602 }
26603 </pre>
26605 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
26606 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
26609 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
26610 <!--page 551 -->
26611 <pre>
26614 /* Divide z / w ... */
26615 double complex _Cdivd(double complex z, double complex w)
26616 {
26617 #pragma STDC FP_CONTRACT OFF
26618 double a, b, c, d, logbw, denom, x, y;
26619 int ilogbw = 0;
26620 a = creal(z); b = cimag(z);
26621 c = creal(w); d = cimag(w);
26622 logbw = logb(fmax(fabs(c), fabs(d)));
26623 if (logbw == INFINITY) {
26624 ilogbw = (int)logbw;
26625 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
26626 }
26627 denom = c * c + d * d;
26628 x = scalbn((a * c + b * d) / denom, -ilogbw);
26629 y = scalbn((b * c - a * d) / denom, -ilogbw);
26630 /* Recover infinities and zeros that computed as NaN+iNaN; */
26631 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
26632 if (isnan(x) && isnan(y)) {
26634 (!isnan(a) || !isnan(b))) {
26635 x = copysign(INFINITY, c) * a;
26636 y = copysign(INFINITY, c) * b;
26637 }
26638 else if ((isinf(a) || isinf(b)) &&
26639 isfinite(c) && isfinite(d)) {
26642 x = INFINITY * ( a * c + b * d );
26643 y = INFINITY * ( b * c - a * d );
26644 }
26645 else if (isinf(logbw) &&
26646 isfinite(a) && isfinite(b)) {
26649 x = 0.0 * ( a * c + b * d );
26650 y = 0.0 * ( b * c - a * d );
26651 }
26652 }
26653 return x + I * y;
26654 }
26655 </pre>
26657 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
26658 for multiplication. In the spirit of the multiplication example above, this code does not defend against
26659 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
26660 with division, provides better roundoff characteristics.
26664 <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
26665 (at least where the state for CX_LIMITED_RANGE is ''off'').
26666 </small>
26671 If both operands have imaginary type, then the result has imaginary type. (If one operand
26672 has real type and the other operand has imaginary type, or if either operand has complex
26673 type, then the result has complex type.)
26675 In all cases the result and floating-point exception behavior of a + or - operator is defined
26676 by the usual mathematical formula:
26677 <pre>
26678 + or - u iv u + iv
26679 </pre>
26681 <pre>
26682 x x(+-)u x (+-) iv (x (+-) u) (+-) iv
26683 </pre>
26685 <pre>
26686 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)
26687 </pre>
26689 <pre>
26690 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)
26691 </pre>
26695 The macros
26696 <pre>
26697 imaginary
26698 </pre>
26699 and
26700 <pre>
26701 _Imaginary_I
26702 </pre>
26703 are defined, respectively, as _Imaginary and a constant expression of type const
26704 float _Imaginary with the value of the imaginary unit. The macro
26705 <pre>
26706 I
26707 </pre>
26708 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
26709 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
26710 imaginary.
26712 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
26713 particularly suited to IEC 60559 implementations. For families of functions, the
26714 specifications apply to all of the functions even though only the principal function is
26715 <!--page 552 -->
26716 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
26717 and the result, the result has the same sign as the argument.
26719 The functions are continuous onto both sides of their branch cuts, taking into account the
26722 Since complex and imaginary values are composed of real values, each function may be
26723 regarded as computing real values from real values. Except as noted, the functions treat
26724 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
26725 manner consistent with the specifications for real functions in F.10.<sup><a href="#note365"><b>365)</b></a></sup>
26727 The functions cimag, conj, cproj, and creal are fully specified for all
26728 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
26729 point exceptions.
26731 Each of the functions cabs and carg is specified by a formula in terms of a real
26733 <pre>
26734 cabs(x + iy) = hypot(x, y)
26735 carg(x + iy) = atan2(y, x)
26736 </pre>
26738 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
26739 a formula in terms of other complex functions (whose special cases are specified below):
26740 <pre>
26741 casin(z) = -i casinh(iz)
26742 catan(z) = -i catanh(iz)
26743 ccos(z) = ccosh(iz)
26744 csin(z) = -i csinh(iz)
26745 ctan(z) = -i ctanh(iz)
26746 </pre>
26748 For the other functions, the following subclauses specify behavior for special cases,
26749 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
26750 families of functions, the specifications apply to all of the functions even though only the
26751 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
26752 specifications for the upper half-plane imply the specifications for the lower half-plane; if
26753 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
26754 specifications for the first quadrant imply the specifications for the other three quadrants.
26756 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
26761 <!--page 553 -->
26764 <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
26765 other part is a NaN.
26766 </small>
26772 <ul>
26773 <li> cacos(conj(z)) = conj(cacos(z)).
26777 <li> cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26778 point exception, for nonzero finite x.
26779 <li> cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
26783 <li> cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
26784 result is unspecified).
26785 <li> cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26786 point exception, for finite y.
26787 <li> cacos(NaN + i (inf)) returns NaN - i (inf).
26788 <li> cacos(NaN + iNaN) returns NaN + iNaN.
26789 </ul>
26795 <ul>
26796 <li> cacosh(conj(z)) = conj(cacosh(z)).
26799 <li> cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
26800 floating-point exception, for finite x.
26801 <li> cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
26802 <li> cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
26805 <li> cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
26806 <!--page 554 -->
26807 <li> cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
26808 floating-point exception, for finite y.
26809 <li> cacosh(NaN + i (inf)) returns +(inf) + iNaN.
26810 <li> cacosh(NaN + iNaN) returns NaN + iNaN.
26811 </ul>
26815 <ul>
26816 <li> casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
26819 <li> casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
26820 floating-point exception, for finite x.
26821 <li> casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
26823 <li> casinh(+(inf) + iNaN) returns +(inf) + iNaN.
26824 <li> casinh(NaN + i0) returns NaN + i0.
26825 <li> casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
26826 floating-point exception, for finite nonzero y.
26827 <li> casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
26828 is unspecified).
26829 <li> casinh(NaN + iNaN) returns NaN + iNaN.
26830 </ul>
26834 <ul>
26835 <li> catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
26839 exception.
26841 <li> catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
26842 floating-point exception, for nonzero finite x.
26846 <!--page 555 -->
26847 <li> catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
26848 floating-point exception, for finite y.
26849 <li> catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
26850 unspecified).
26851 <li> catanh(NaN + iNaN) returns NaN + iNaN.
26852 </ul>
26856 <ul>
26857 <li> ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
26860 result is unspecified) and raises the ''invalid'' floating-point exception.
26862 result is unspecified).
26863 <li> ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
26864 exception, for finite nonzero x.
26865 <li> ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26866 point exception, for finite nonzero x.
26867 <li> ccosh(+(inf) + i0) returns +(inf) + i0.
26868 <li> ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
26869 <li> ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
26870 unspecified) and raises the ''invalid'' floating-point exception.
26871 <li> ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
26872 <li> ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
26873 result is unspecified).
26874 <li> ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26875 point exception, for all nonzero numbers y.
26876 <li> ccosh(NaN + iNaN) returns NaN + iNaN.
26877 </ul>
26881 <ul>
26882 <li> csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
26884 <li> csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
26885 unspecified) and raises the ''invalid'' floating-point exception.
26887 unspecified).
26888 <!--page 556 -->
26889 <li> csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
26890 exception, for positive finite x.
26891 <li> csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26892 point exception, for finite nonzero x.
26893 <li> csinh(+(inf) + i0) returns +(inf) + i0.
26894 <li> csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
26895 <li> csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
26896 unspecified) and raises the ''invalid'' floating-point exception.
26897 <li> csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
26898 is unspecified).
26899 <li> csinh(NaN + i0) returns NaN + i0.
26900 <li> csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26901 point exception, for all nonzero numbers y.
26902 <li> csinh(NaN + iNaN) returns NaN + iNaN.
26903 </ul>
26907 <ul>
26908 <li> ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
26910 <li> ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
26911 exception, for finite x.
26912 <li> ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26913 point exception, for finite x.
26915 <li> ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
26916 is unspecified).
26918 result is unspecified).
26919 <li> ctanh(NaN + i0) returns NaN + i0.
26920 <li> ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26921 point exception, for all nonzero numbers y.
26922 <li> ctanh(NaN + iNaN) returns NaN + iNaN.
26923 <!--page 557 -->
26924 </ul>
26930 <ul>
26931 <li> cexp(conj(z)) = conj(cexp(z)).
26933 <li> cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
26934 exception, for finite x.
26935 <li> cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26936 point exception, for finite x.
26937 <li> cexp(+(inf) + i0) returns +(inf) + i0.
26939 <li> cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
26940 <li> cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
26941 the result are unspecified).
26942 <li> cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
26943 exception (where the sign of the real part of the result is unspecified).
26944 <li> cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
26945 of the result are unspecified).
26946 <li> cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
26947 is unspecified).
26948 <li> cexp(NaN + i0) returns NaN + i0.
26949 <li> cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26950 point exception, for all nonzero numbers y.
26951 <li> cexp(NaN + iNaN) returns NaN + iNaN.
26952 </ul>
26956 <ul>
26957 <li> clog(conj(z)) = conj(clog(z)).
26959 exception.
26961 exception.
26963 <li> clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26964 point exception, for finite x.
26965 <!--page 558 -->
26966 <li> clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
26967 <li> clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
26970 <li> clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
26971 <li> clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26972 point exception, for finite y.
26973 <li> clog(NaN + i (inf)) returns +(inf) + iNaN.
26974 <li> clog(NaN + iNaN) returns NaN + iNaN.
26975 </ul>
26981 The cpow functions raise floating-point exceptions if appropriate for the calculation of
26982 the parts of the result, and may also raise spurious floating-point exceptions.<sup><a href="#note366"><b>366)</b></a></sup>
26985 <p><small><a name="note366" href="#note366">366)</a> This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
26986 implementations that treat special cases more carefully.
26987 </small>
26991 <ul>
26992 <li> csqrt(conj(z)) = conj(csqrt(z)).
26994 <li> csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
26995 <li> csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
26996 point exception, for finite x.
26998 <li> csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
26999 <li> csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
27000 result is unspecified).
27001 <li> csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
27002 <li> csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
27003 point exception, for finite y.
27004 <li> csqrt(NaN + iNaN) returns NaN + iNaN.
27009 <!--page 559 -->
27010 </ul>
27014 Type-generic macros that accept complex arguments also accept imaginary arguments. If
27015 an argument is imaginary, the macro expands to an expression whose type is real,
27016 imaginary, or complex, as appropriate for the particular function: if the argument is
27017 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
27018 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
27019 the types of the others are complex.
27021 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
27022 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
27023 functions:
27024 <!--page 560 -->
27025 <pre>
27026 cos(iy) = cosh(y)
27027 sin(iy) = i sinh(y)
27028 tan(iy) = i tanh(y)
27029 cosh(iy) = cos(y)
27030 sinh(iy) = i sin(y)
27031 tanh(iy) = i tan(y)
27032 asin(iy) = i asinh(y)
27033 atan(iy) = i atanh(y)
27034 asinh(iy) = i asin(y)
27035 atanh(iy) = i atan(y)
27036 </pre>
27039 <pre>
27040 (informative)
27041 Language independent arithmetic
27042 </pre>
27048 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
27052 The relevant C arithmetic types meet the requirements of LIA-1 types if an
27053 implementation adds notification of exceptional arithmetic operations and meets the 1
27054 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
27058 The LIA-1 data type Boolean is implemented by the C data type bool with values of
27063 The signed C integer types int, long int, long long int, and the corresponding
27064 unsigned types are compatible with LIA-1. If an implementation adds support for the
27065 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
27067 in that overflows or out-of-bounds results silently wrap. An implementation that defines
27068 signed integer types as also being modulo need not detect integer overflow, in which case,
27069 only integer divide-by-zero need be detected.
27071 The parameters for the integer data types can be accessed by the following:
27072 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
27073 <pre>
27074 ULLONG_MAX
27075 </pre>
27076 minint INT_MIN, LONG_MIN, LLONG_MIN
27078 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
27079 is always 0 for the unsigned types, and is not provided for those types.
27080 <!--page 561 -->
27084 The integer operations on integer types are the following:
27085 addI x + y
27086 subI x - y
27087 mulI x * y
27088 divI, divtI x / y
27089 remI, remtI x % y
27090 negI -x
27091 absI abs(x), labs(x), llabs(x)
27092 eqI x == y
27093 neqI x != y
27094 lssI x < y
27095 leqI x <= y
27096 gtrI x > y
27097 geqI x >= y
27098 where x and y are expressions of the same integer type.
27102 The C floating-point types float, double, and long double are compatible with
27104 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
27105 with LIA-1. An implementation that uses IEC 60559 floating-point formats and
27106 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
27107 conformant types.
27110 <p><!--para 1 -->
27111 The parameters for a floating point data type can be accessed by the following:
27112 r FLT_RADIX
27113 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
27114 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
27115 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
27116 <p><!--para 2 -->
27117 The derived constants for the floating point types are accessed by the following:
27118 <!--page 562 -->
27119 fmax FLT_MAX, DBL_MAX, LDBL_MAX
27120 fminN FLT_MIN, DBL_MIN, LDBL_MIN
27121 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
27122 rnd_style FLT_ROUNDS
27125 <p><!--para 1 -->
27126 The floating-point operations on floating-point types are the following:
27127 addF x + y
27128 subF x - y
27129 mulF x * y
27130 divF x / y
27131 negF -x
27132 absF fabsf(x), fabs(x), fabsl(x)
27133 exponentF 1.f+logbf(x), 1.0+logb(x), 1.L+logbl(x)
27134 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
27135 <pre>
27136 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)
27137 </pre>
27138 intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
27139 fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
27140 eqF x == y
27141 neqF x != y
27142 lssF x < y
27143 leqF x <= y
27144 gtrF x > y
27145 geqF x >= y
27146 where x and y are expressions of the same floating point type, n is of type int, and li
27147 is of type long int.
27150 <p><!--para 1 -->
27151 The C Standard requires all floating types to use the same radix and rounding style, so
27152 that only one identifier for each is provided to map to LIA-1.
27153 <p><!--para 2 -->
27154 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
27155 truncate FLT_ROUNDS == 0
27156 <!--page 563 -->
27157 nearest FLT_ROUNDS == 1
27158 other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
27159 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
27160 in all relevant LIA-1 operations, not just addition as in C.
27163 <p><!--para 1 -->
27164 The LIA-1 type conversions are the following type casts:
27165 cvtI' -> I (int)i, (long int)i, (long long int)i,
27166 <pre>
27167 (unsigned int)i, (unsigned long int)i,
27168 (unsigned long long int)i
27169 </pre>
27170 cvtF -> I (int)x, (long int)x, (long long int)x,
27171 <pre>
27172 (unsigned int)x, (unsigned long int)x,
27173 (unsigned long long int)x
27174 </pre>
27175 cvtI -> F (float)i, (double)i, (long double)i
27176 cvtF' -> F (float)x, (double)x, (long double)x
27177 <p><!--para 2 -->
27178 In the above conversions from floating to integer, the use of (cast)x can be replaced with
27179 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
27180 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
27181 conversion functions, lrint(), llrint(), lround(), and llround(), can be
27182 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
27183 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
27184 <p><!--para 3 -->
27185 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
27186 fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
27187 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
27188 to 65535.0 which can then be cast to unsigned short int. But, the
27189 remainder() function is not useful for doing silent wrapping to signed integer types,
27190 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
27191 range -32767.0 to +32768.0 which is not, in general, in the range of signed short
27192 int.
27193 <p><!--para 4 -->
27194 C's conversions (casts) from floating-point to floating-point can meet LIA-1
27195 requirements if an implementation uses round-to-nearest (IEC 60559 default).
27196 <p><!--para 5 -->
27197 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
27198 implementation uses round-to-nearest.
27199 <!--page 564 -->
27202 <p><!--para 1 -->
27203 Notification is the process by which a user or program is informed that an exceptional
27204 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
27205 allows an implementation to cause a notification to occur when any arithmetic operation
27206 returns an exceptional value as defined in LIA-1 clause 5.
27209 <p><!--para 1 -->
27210 LIA-1 requires at least the following two alternatives for handling of notifications:
27211 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
27212 resume.
27213 <p><!--para 2 -->
27214 An implementation need only support a given notification alternative for the entire
27215 program. An implementation may support the ability to switch between notification
27216 alternatives during execution, but is not required to do so. An implementation can
27217 provide separate selection for each kind of notification, but this is not required.
27218 <p><!--para 3 -->
27219 C allows an implementation to provide notification. C's SIGFPE (for traps) and
27220 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
27221 can provide LIA-1 notification.
27222 <p><!--para 4 -->
27223 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
27224 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
27225 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
27226 and-resume behavior with the same constraint.
27229 <p><!--para 1 -->
27231 <p><!--para 2 -->
27232 The following mapping is for floating-point types:
27233 undefined FE_INVALID, FE_DIVBYZERO
27234 floating_overflow FE_OVERFLOW
27235 underflow FE_UNDERFLOW
27236 <p><!--para 3 -->
27237 The floating-point indicator interrogation and manipulation operations are:
27238 set_indicators feraiseexcept(i)
27239 clear_indicators feclearexcept(i)
27240 test_indicators fetestexcept(i)
27241 current_indicators fetestexcept(FE_ALL_EXCEPT)
27242 where i is an expression of type int representing a subset of the LIA-1 indicators.
27243 <p><!--para 4 -->
27244 C allows an implementation to provide the following LIA-1 required behavior: at
27245 program termination if any indicator is set the implementation shall send an unambiguous
27246 <!--page 565 -->
27248 <p><!--para 5 -->
27249 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
27250 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
27251 point indicators.
27254 <p><!--para 1 -->
27255 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
27256 math library functions (which are not permitted to invoke a user's signal handler for
27257 SIGFPE). An implementation can provide an alternative of notification through
27258 termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
27259 <p><!--para 2 -->
27260 LIA-1 does not require that traps be precise.
27261 <p><!--para 3 -->
27262 C does require that SIGFPE be the signal corresponding to LIA-1 arithmetic exceptions,
27263 if there is any signal raised for them.
27264 <p><!--para 4 -->
27265 C supports signal handlers for SIGFPE and allows trapping of LIA-1 arithmetic
27266 exceptions. When LIA-1 arithmetic exceptions do trap, C's signal-handler mechanism
27267 allows trap-and-terminate (either default implementation behavior or user replacement for
27268 it) or trap-and-resume, at the programmer's option.
27269 <!--page 566 -->
27272 <pre>
27273 (informative)
27274 Common warnings
27275 </pre>
27276 <p><!--para 1 -->
27277 An implementation may generate warnings in many situations, none of which are
27278 specified as part of this International Standard. The following are a few of the more
27279 common situations.
27280 <p><!--para 2 -->
27281 <ul>
27282 <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>).
27283 <li> A block with initialization of an object that has automatic storage duration is jumped
27285 <li> An implicit narrowing conversion is encountered, such as the assignment of a long
27286 int or a double to an int, or a pointer to void to a pointer to any type other than
27288 <li> A hexadecimal floating constant cannot be represented exactly in its evaluation format
27290 <li> An integer character constant includes more than one character or a wide character
27293 <li> An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
27294 lvalue in one operand, and a side effect to, or an access to the value of, the identical
27296 <li> A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
27297 <li> The arguments in a function call do not agree in number and type with those of the
27300 <li> A value is given to an object of an enumerated type other than by assignment of an
27301 enumeration constant that is a member of that type, or an enumeration object that has
27302 the same type, or the value of a function that returns the same enumerated type
27307 <li> A constant expression is used as the controlling expression of a selection statement
27309 <!--page 567 -->
27310 <li> An incorrectly formed preprocessing group is encountered while skipping a
27313 <!--page 568 -->
27314 </ul>
27317 <pre>
27318 (informative)
27319 Portability issues
27320 </pre>
27321 <p><!--para 1 -->
27322 This annex collects some information about portability that appears in this International
27323 Standard.
27326 <p><!--para 1 -->
27327 The following are unspecified:
27328 <ul>
27330 <li> The termination status returned to the hosted environment if the return type of main
27332 <li> The behavior of the display device if a printing character is written when the active
27334 <li> The behavior of the display device if a backspace character is written when the active
27336 <li> The behavior of the display device if a horizontal tab character is written when the
27337 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
27338 <li> The behavior of the display device if a vertical tab character is written when the active
27339 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
27340 <li> How an extended source character that does not correspond to a universal character
27341 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
27343 <li> The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
27344 <li> The values of bytes that correspond to union members other than the one last stored
27346 <li> The representation used when storing a value in an object that has more than one
27348 <li> The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
27349 <li> Whether certain operators can generate negative zeros and whether a negative zero
27352 <li> The order in which subexpressions are evaluated and the order in which side effects
27353 take place, except as specified for the function-call (), &&, ||, ? :, and comma
27354 <!--page 569 -->
27356 <li> The order in which the function designator, arguments, and subexpressions within the
27358 <li> The order of side effects among compound literal initialization list expressions
27360 <li> The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
27361 <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>).
27362 <li> Whether a call to an inline function uses the inline definition or the external definition
27364 <li> Whether or not a size expression is evaluated when it is part of the operand of a
27365 sizeof operator and changing the value of the size expression would not affect the
27367 <li> The order in which any side effects occur among the initialization list expressions in
27370 <li> When a fully expanded macro replacement list contains a function-like macro name
27371 as its last preprocessing token and the next preprocessing token from the source file is
27372 a (, and the fully expanded replacement of that macro ends with the name of the first
27373 macro and the next preprocessing token from the source file is again a (, whether that
27375 <li> The order in which # and ## operations are evaluated during macro substitution
27377 <li> The state of the floating-point status flags when execution passes from a part of the *
27378 program translated with FENV_ACCESS ''off'' to a part translated with
27380 <li> The order in which feraiseexcept raises floating-point exceptions, except as
27382 <li> Whether math_errhandling is a macro or an identifier with external linkage
27384 <li> The results of the frexp functions when the specified value is not a floating-point
27386 <li> The numeric result of the ilogb functions when the correct value is outside the
27387 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>).
27388 <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>).
27389 <!--page 570 -->
27390 <li> The value stored by the remquo functions in the object pointed to by quo when y is
27392 <li> Whether a comparison macro argument that is represented in a format wider than its
27394 <li> Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
27395 <li> Whether va_copy and va_end are macros or identifiers with external linkage
27397 <li> The hexadecimal digit before the decimal point when a non-normalized floating-point
27398 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>).
27399 <li> The value of the file position indicator after a successful call to the ungetc function
27400 for a text stream, or the ungetwc function for any stream, until all pushed-back
27401 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>).
27402 <li> The details of the value stored by the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>).
27403 <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>).
27404 <li> Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
27405 functions convert a minus-signed sequence to a negative number directly or by
27406 negating the value resulting from converting the corresponding unsigned sequence
27408 <li> The order and contiguity of storage allocated by successive calls to the calloc,
27410 <li> The amount of storage allocated by a successful call to the calloc, malloc, or
27412 <li> Which of two elements that compare as equal is matched by the bsearch function
27414 <li> The order of two elements that compare as equal in an array sorted by the qsort
27416 <li> The encoding of the calendar time returned by the time function (<a href="#7.26.2.4">7.26.2.4</a>).
27417 <li> The characters stored by the strftime or wcsftime function if any of the time
27418 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>).
27419 <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>,
27421 <li> The resulting value when the ''invalid'' floating-point exception is raised during
27423 <!--page 571 -->
27424 <li> Whether conversion of non-integer IEC 60559 floating values to integer raises the
27426 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
27428 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
27429 floating-point exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
27430 <li> The exponent value stored by frexp for a NaN or infinity (<a href="#F.10.3.4">F.10.3.4</a>).
27431 <li> The numeric result returned by the lrint, llrint, lround, and llround
27432 functions if the rounded value is outside the range of the return type (<a href="#F.10.6.5">F.10.6.5</a>,
27434 <li> The sign of one part of the complex result of several math functions for certain
27435 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>,
27436 <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>).
27437 </ul>
27440 <p><!--para 1 -->
27441 The behavior is undefined in the following circumstances:
27442 <ul>
27443 <li> A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
27444 (clause 4).
27445 <li> A nonempty source file does not end in a new-line character which is not immediately
27446 preceded by a backslash character or ends in a partial preprocessing token or
27448 <li> Token concatenation produces a character sequence matching the syntax of a
27450 <li> A program in a hosted environment does not define a function named main using one
27453 <li> A character not in the basic source character set is encountered in a source file, except
27454 in an identifier, a character constant, a string literal, a header name, a comment, or a
27456 <li> An identifier, comment, string literal, character constant, or header name contains an
27457 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>).
27458 <li> The same identifier has both internal and external linkage in the same translation unit
27461 <!--page 572 -->
27462 <li> The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
27463 <li> The value of an object with automatic storage duration is used while it is
27464 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>).
27465 <li> A trap representation is read by an lvalue expression that does not have character type
27467 <li> A trap representation is produced by a side effect that modifies any part of the object
27468 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
27469 <li> The operands to certain operators are such that they could produce a negative zero
27470 result, but the implementation does not support negative zeros (<a href="#6.2.6.2">6.2.6.2</a>).
27471 <li> Two declarations of the same object or function specify types that are not compatible
27473 <li> A program requires the formation of a composite type from a variable length array
27474 type whose size is specified by an expression that is not evaluated (<a href="#6.2.7">6.2.7</a>).
27475 <li> Conversion to or from an integer type produces a value outside the range that can be
27477 <li> Demotion of one real floating type to another produces a value outside the range that
27480 <li> A non-array lvalue with an incomplete type is used in a context that requires the value
27482 <li> An lvalue designating an object of automatic storage duration that could have been
27483 declared with the register storage class is used in a context that requires the value
27485 <li> An lvalue having array type is converted to a pointer to the initial element of the
27487 <li> An attempt is made to use the value of a void expression, or an implicit or explicit
27489 <li> Conversion of a pointer to an integer type produces a value outside the range that can
27491 <li> Conversion between two pointer types produces a result that is incorrectly aligned
27493 <li> A pointer is used to call a function whose type is not compatible with the referenced
27495 <!--page 573 -->
27496 <li> An unmatched ' or " character is encountered on a logical source line during
27500 <li> A universal character name in an identifier does not designate a character whose
27502 <li> The initial character of an identifier is a universal character name designating a digit
27504 <li> Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
27508 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
27510 <li> A side effect on a scalar object is unsequenced relative to either a different side effect
27511 on the same scalar object or a value computation using the value of the same scalar
27513 <li> An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
27514 <li> An object has its stored value accessed other than by an lvalue of an allowable type
27516 <li> For a call to a function without a function prototype in scope, the number of *
27518 <li> For call to a function without a function prototype in scope where the function is
27519 defined with a function prototype, either the prototype ends with an ellipsis or the
27520 types of the arguments after promotion are not compatible with the types of the
27522 <li> For a call to a function without a function prototype in scope where the function is not
27523 defined with a function prototype, the types of the arguments after promotion are not
27524 compatible with those of the parameters after promotion (with certain exceptions)
27526 <li> A function is defined with a type that is not compatible with the type (of the
27527 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
27529 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
27530 <!--page 574 -->
27531 <li> A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
27532 <li> The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
27533 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
27534 integer type produces a result that does not point into, or just beyond, the same array
27536 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
27537 integer type produces a result that points just beyond the array object and is used as
27539 <li> Pointers that do not point into, or just beyond, the same array object are subtracted
27541 <li> An array subscript is out of range, even if an object is apparently accessible with the
27544 <li> The result of subtracting two pointers is not representable in an object of type
27546 <li> An expression is shifted by a negative number or by an amount greater than or equal
27548 <li> An expression having signed promoted type is left-shifted and either the value of the
27549 expression is negative or the result of shifting would be not be representable in the
27551 <li> Pointers that do not point to the same aggregate or union (nor just beyond the same
27553 <li> An object is assigned to an inexactly overlapping object or to an exactly overlapping
27555 <li> An expression that is required to be an integer constant expression does not have an
27556 integer type; has operands that are not integer constants, enumeration constants,
27557 character constants, sizeof expressions whose results are integer constants, or
27558 immediately-cast floating constants; or contains casts (outside operands to sizeof
27559 operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
27560 <li> A constant expression in an initializer is not, or does not evaluate to, one of the
27561 following: an arithmetic constant expression, a null pointer constant, an address
27562 constant, or an address constant for a complete object type plus or minus an integer
27564 <li> An arithmetic constant expression does not have arithmetic type; has operands that
27565 are not integer constants, floating constants, enumeration constants, character
27566 constants, or sizeof expressions; or contains casts (outside operands to sizeof
27567 <!--page 575 -->
27568 operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
27570 address &, or indirection * operator or a pointer cast in creating an address constant
27572 <li> An identifier for an object is declared with no linkage and the type of the object is
27573 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
27574 <li> A function is declared at block scope with an explicit storage-class specifier other
27576 <li> A structure or union is defined as containing no named members, no anonymous
27578 <li> An attempt is made to access, or generate a pointer to just past, a flexible array
27579 member of a structure when the referenced object provides no elements for that array
27581 <li> When the complete type is needed, an incomplete structure or union type is not
27582 completed in the same scope by another declaration of the tag that defines the content
27584 <li> An attempt is made to modify an object defined with a const-qualified type through
27586 <li> An attempt is made to refer to an object defined with a volatile-qualified type through
27588 <li> The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>). *
27589 <li> Two qualified types that are required to be compatible do not have the identically
27591 <li> An object which has been modified is accessed through a restrict-qualified pointer to
27592 a const-qualified type, or through a restrict-qualified pointer and another pointer that
27594 <li> A restrict-qualified pointer is assigned a value based on another restricted pointer
27595 whose associated block neither began execution before the block associated with this
27597 <li> A function with external linkage is declared with an inline function specifier, but is
27599 <li> A function declared with a _Noreturn function specifier returns to its caller (<a href="#6.7.4">6.7.4</a>).
27600 <li> The definition of an object has an alignment specifier and another declaration of that
27602 <!--page 576 -->
27603 <li> Declarations of an object in different translation units have different alignment
27605 <li> Two pointer types that are required to be compatible are not identically qualified, or
27607 <li> The size expression in an array declaration is not a constant expression and evaluates
27609 <li> In a context requiring two array types to be compatible, they do not have compatible
27610 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.6.2">6.7.6.2</a>).
27611 <li> A declaration of an array parameter includes the keyword static within the [ and
27612 ] and the corresponding argument does not provide access to the first element of an
27614 <li> A storage-class specifier or type qualifier modifies the keyword void as a function
27616 <li> In a context requiring two function types to be compatible, they do not have
27617 compatible return types, or their parameters disagree in use of the ellipsis terminator
27618 or the number and type of parameters (after default argument promotion, when there
27619 is no parameter type list or when one type is specified by a function definition with an
27621 <li> The value of an unnamed member of a structure or union is used (<a href="#6.7.9">6.7.9</a>).
27622 <li> The initializer for a scalar is neither a single expression nor a single expression
27624 <li> The initializer for a structure or union object that has automatic storage duration is
27625 neither an initializer list nor a single expression that has compatible structure or union
27627 <li> The initializer for an aggregate or union, other than an array initialized by a string
27628 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.9">6.7.9</a>).
27629 <li> An identifier with external linkage is used, but in the program there does not exist
27630 exactly one external definition for the identifier, or the identifier is not used and there
27632 <li> A function definition includes an identifier list, but the types of the parameters are not
27634 <li> An adjusted parameter type in a function definition is not a complete object type
27636 <li> A function that accepts a variable number of arguments is defined without a
27638 <!--page 577 -->
27639 <li> The } that terminates a function is reached, and the value of the function call is used
27641 <li> An identifier for an object with internal linkage and an incomplete type is declared
27643 <li> The token defined is generated during the expansion of a #if or #elif
27644 preprocessing directive, or the use of the defined unary operator does not match
27646 <li> The #include preprocessing directive that results after expansion does not match
27648 <li> The character sequence in an #include preprocessing directive does not start with a
27650 <li> There are sequences of preprocessing tokens within the list of macro arguments that
27652 <li> The result of the preprocessing operator # is not a valid character string literal
27654 <li> The result of the preprocessing operator ## is not a valid preprocessing token
27656 <li> The #line preprocessing directive that results after expansion does not match one of
27657 the two well-defined forms, or its digit sequence specifies zero or a number greater
27659 <li> A non-STDC #pragma preprocessing directive that is documented as causing
27660 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
27661 <li> A #pragma STDC preprocessing directive does not match one of the well-defined
27663 <li> The name of a predefined macro, or the identifier defined, is the subject of a
27665 <li> An attempt is made to copy an object to an overlapping object by use of a library
27666 function, other than as explicitly allowed (e.g., memmove) (clause 7).
27667 <li> A file with the same name as one of the standard headers, not provided as part of the
27668 implementation, is placed in any of the standard places that are searched for included
27670 <li> A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
27671 <li> A function, object, type, or macro that is specified as being declared or defined by
27672 some standard header is used before any header that declares or defines it is included
27674 <!--page 578 -->
27675 <li> A standard header is included while a macro is defined with the same name as a
27677 <li> The program attempts to declare a library function itself, rather than via a standard
27679 <li> The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
27681 <li> The program removes the definition of a macro whose name begins with an
27683 <li> An argument to a library function has an invalid value or a type not expected by a
27685 <li> The pointer passed to a library function array parameter does not have a value such
27687 <li> The macro definition of assert is suppressed in order to access an actual function
27690 <li> The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
27691 any context other than outside all external declarations or preceding all explicit
27692 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>).
27693 <li> The value of an argument to a character handling function is neither equal to the value
27695 <li> A macro definition of errno is suppressed in order to access an actual object, or the
27697 <li> Part of the program tests floating-point status flags, sets floating-point control modes,
27698 or runs under non-default mode settings, but was translated with the state for the
27700 <li> The exception-mask argument for one of the functions that provide access to the
27701 floating-point status flags has a nonzero value not obtained by bitwise OR of the
27703 <li> The fesetexceptflag function is used to set floating-point status flags that were
27704 not specified in the call to the fegetexceptflag function that provided the value
27706 <li> The argument to fesetenv or feupdateenv is neither an object set by a call to
27707 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>).
27708 <li> The value of the result of an integer arithmetic or conversion function cannot be
27709 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>).
27710 <!--page 579 -->
27711 <li> The program modifies the string pointed to by the value returned by the setlocale
27713 <li> The program modifies the structure pointed to by the value returned by the
27715 <li> A macro definition of math_errhandling is suppressed or the program defines
27717 <li> An argument to a floating-point classification or comparison macro is not of real
27719 <li> A macro definition of setjmp is suppressed in order to access an actual function, or
27721 <li> An invocation of the setjmp macro occurs other than in an allowed context
27723 <li> The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
27724 <li> After a longjmp, there is an attempt to access the value of an object of automatic
27725 storage duration that does not have volatile-qualified type, local to the function
27726 containing the invocation of the corresponding setjmp macro, that was changed
27728 <li> The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
27729 <li> A signal handler returns when the signal corresponded to a computational exception
27731 <li> A signal occurs as the result of calling the abort or raise function, and the signal
27733 <li> A signal occurs other than as the result of calling the abort or raise function, and
27734 the signal handler refers to an object with static or thread storage duration that is not a
27735 lock-free atomic object other than by assigning a value to an object declared as
27736 volatile sig_atomic_t, or calls any function in the standard library other
27737 than the abort function, the _Exit function, the quick_exit function, or the
27739 <li> The value of errno is referred to after a signal occurred other than as the result of
27740 calling the abort or raise function and the corresponding signal handler obtained
27742 <li> A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
27743 <li> A function with a variable number of arguments attempts to access its varying
27744 arguments other than through a properly declared and initialized va_list object, or
27745 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>).
27746 <!--page 580 -->
27747 <li> The macro va_arg is invoked using the parameter ap that was passed to a function
27749 <li> A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
27750 order to access an actual function, or the program defines an external identifier with
27752 <li> The va_start or va_copy macro is invoked without a corresponding invocation
27753 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>,
27755 <li> The type parameter to the va_arg macro is not such that a pointer to an object of
27757 <li> The va_arg macro is invoked when there is no actual next argument, or with a
27758 specified type that is not compatible with the promoted type of the actual next
27760 <li> The va_copy or va_start macro is called to initialize a va_list that was
27761 previously initialized by either macro without an intervening invocation of the
27762 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>).
27763 <li> The parameter parmN of a va_start macro is declared with the register
27764 storage class, with a function or array type, or with a type that is not compatible with
27765 the type that results after application of the default argument promotions (<a href="#7.16.1.4">7.16.1.4</a>).
27766 <li> The member designator parameter of an offsetof macro is an invalid right
27767 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.19">7.19</a>).
27768 <li> The argument in an instance of one of the integer-constant macros is not a decimal,
27769 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
27771 <li> A byte input/output function is applied to a wide-oriented stream, or a wide character
27773 <li> Use is made of any portion of a file beyond the most recent wide character written to
27775 <li> The value of a pointer to a FILE object is used after the associated file is closed
27777 <li> The stream for the fflush function points to an input stream or to an update stream
27779 <li> The string pointed to by the mode argument in a call to the fopen function does not
27781 <li> An output operation on an update stream is followed by an input operation without an
27782 intervening call to the fflush function or a file positioning function, or an input
27783 <!--page 581 -->
27784 operation on an update stream is followed by an output operation with an intervening
27786 <li> An attempt is made to use the contents of the array that was supplied in a call to the
27788 <li> There are insufficient arguments for the format in a call to one of the formatted
27789 input/output functions, or an argument does not have an appropriate type (<a href="#7.21.6.1">7.21.6.1</a>,
27790 <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>).
27791 <li> The format in a call to one of the formatted input/output functions or to the
27792 strftime or wcsftime function is not a valid multibyte character sequence that
27793 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>,
27795 <li> In a call to one of the formatted output functions, a precision appears with a
27796 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>).
27797 <li> A conversion specification for a formatted output function uses an asterisk to denote
27798 an argument-supplied field width or precision, but the corresponding argument is not
27801 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>).
27802 <li> A conversion specification for one of the formatted input/output functions uses a
27803 length modifier with a conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>,
27804 <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>).
27805 <li> An s conversion specifier is encountered by one of the formatted output functions,
27806 and the argument is missing the null terminator (unless a precision is specified that
27807 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>).
27808 <li> An n conversion specification for one of the formatted input/output functions includes
27809 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.21.6.1">7.21.6.1</a>,
27810 <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>).
27811 <li> A % conversion specifier is encountered by one of the formatted input/output
27812 functions, but the complete conversion specification is not exactly %% (<a href="#7.21.6.1">7.21.6.1</a>,
27813 <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>).
27814 <li> An invalid conversion specification is found in the format for one of the formatted
27815 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>,
27816 <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>).
27817 <li> The number of characters transmitted by a formatted output function is greater than
27818 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>).
27819 <!--page 582 -->
27820 <li> The result of a conversion by one of the formatted input functions cannot be
27821 represented in the corresponding object, or the receiving object does not have an
27823 <li> A c, s, or [ conversion specifier is encountered by one of the formatted input
27824 functions, and the array pointed to by the corresponding argument is not large enough
27825 to accept the input sequence (and a null terminator if the conversion specifier is s or
27827 <li> A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
27828 formatted input functions, but the input is not a valid multibyte character sequence
27829 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>).
27830 <li> The input item for a %p conversion by one of the formatted input functions is not a
27831 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>).
27832 <li> The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
27833 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
27834 vwscanf function is called with an improperly initialized va_list argument, or
27835 the argument is used (other than in an invocation of va_end) after the function
27836 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>,
27837 <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>).
27838 <li> The contents of the array supplied in a call to the fgets or fgetws function are
27839 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>).
27840 <li> The file position indicator for a binary stream is used after a call to the ungetc
27842 <li> The file position indicator for a stream is used after an error occurred during a call to
27843 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>).
27844 <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>).
27845 <li> The fseek function is called for a text stream with a nonzero offset and either the
27846 offset was not returned by a previous successful call to the ftell function on a
27847 stream associated with the same file or whence is not SEEK_SET (<a href="#7.21.9.2">7.21.9.2</a>).
27848 <li> The fsetpos function is called to set a position that was not returned by a previous
27849 successful call to the fgetpos function on a stream associated with the same file
27851 <li> A non-null pointer returned by a call to the calloc, malloc, or realloc function
27853 <li> The value of a pointer that refers to space deallocated by a call to the free or
27855 <!--page 583 -->
27856 <li> The alignment requested of the aligned_alloc function is not valid or not
27857 supported by the implementation, or the size requested is not an integral multiple of
27859 <li> The pointer argument to the free or realloc function does not match a pointer
27860 earlier returned by a memory management function, or the space has been deallocated
27861 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>).
27862 <li> The value of the object allocated by the malloc function is used (<a href="#7.22.3.4">7.22.3.4</a>).
27863 <li> The value of any bytes in a new object allocated by the realloc function beyond
27865 <li> The program calls the exit or quick_exit function more than once, or calls both
27867 <li> During the call to a function registered with the atexit or at_quick_exit
27868 function, a call is made to the longjmp function that would terminate the call to the
27870 <li> The string set up by the getenv or strerror function is modified by the program
27872 <li> A command is executed through the system function in a way that is documented as
27873 causing termination or some other form of undefined behavior (<a href="#7.22.4.8">7.22.4.8</a>).
27874 <li> A searching or sorting utility function is called with an invalid pointer argument, even
27876 <li> The comparison function called by a searching or sorting utility function alters the
27877 contents of the array being searched or sorted, or returns ordering values
27879 <li> The array being searched by the bsearch function does not have its elements in
27881 <li> The current conversion state is used by a multibyte/wide character conversion
27883 <li> A string or wide string utility function is instructed to access an array beyond the end
27885 <li> A string or wide string utility function is called with an invalid pointer argument, even
27887 <li> The contents of the destination array are used after a call to the strxfrm,
27888 strftime, wcsxfrm, or wcsftime function in which the specified length was
27889 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>,
27891 <!--page 584 -->
27892 <li> The first argument in the very first call to the strtok or wcstok is a null pointer
27894 <li> The type of an argument to a type-generic macro is not compatible with the type of
27896 <li> A complex argument is supplied for a generic parameter of a type-generic macro that
27898 <li> At least one field of the broken-down time passed to asctime contains a value
27899 outside its normal range, or the calculated year exceeds four digits or is less than the
27901 <li> The argument corresponding to an s specifier without an l qualifier in a call to the
27902 fwprintf function does not point to a valid multibyte character sequence that
27904 <li> In a call to the wcstok function, the object pointed to by ptr does not have the
27905 value stored by the previous call for the same wide string (<a href="#7.28.4.5.7">7.28.4.5.7</a>).
27907 <li> The value of an argument of type wint_t to a wide character classification or case
27908 mapping function is neither equal to the value of WEOF nor representable as a
27910 <li> The iswctype function is called using a different LC_CTYPE category from the
27911 one in effect for the call to the wctype function that returned the description
27913 <li> The towctrans function is called using a different LC_CTYPE category from the
27914 one in effect for the call to the wctrans function that returned the description
27916 </ul>
27920 A conforming implementation is required to document its choice of behavior in each of
27921 the areas listed in this subclause. The following are implementation-defined:
27922 <!--page 585 -->
27926 <ul>
27927 <li> How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
27928 <li> Whether each nonempty sequence of white-space characters other than new-line is
27929 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
27930 </ul>
27934 <ul>
27935 <li> The mapping between physical source file multibyte characters and the source
27937 <li> The name and type of the function called at program startup in a freestanding
27939 <li> The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
27940 <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>).
27941 <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>).
27943 <li> Whether a program can have more than one thread of execution in a freestanding
27945 <li> The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
27946 <li> Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
27948 <li> Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
27950 <li> The set of environment names and the method for altering the environment list used
27952 <li> The manner of execution of the string by the system function (<a href="#7.22.4.8">7.22.4.8</a>).
27953 </ul>
27957 <ul>
27958 <li> Which additional multibyte characters may appear in identifiers and their
27960 <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>).
27961 <!--page 586 -->
27962 </ul>
27966 <ul>
27969 <li> The unique value of the member of the execution character set produced for each of
27971 <li> The value of a char object into which has been stored any character other than a
27973 <li> Which of signed char or unsigned char has the same range, representation,
27975 <li> The mapping of members of the source character set (in character constants and string
27976 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>).
27977 <li> The value of an integer character constant containing more than one character or
27978 containing a character or escape sequence that does not map to a single-byte
27980 <li> The value of a wide character constant containing more than one multibyte character
27981 or a single multibyte character that maps to multiple members of the extended
27982 execution character set, or containing a multibyte character or escape sequence not
27984 <li> The current locale used to convert a wide character constant consisting of a single
27985 multibyte character that maps to a member of the extended execution character set
27987 <li> Whether differently-prefixed wide string literal tokens can be concatenated and, if so,
27989 <li> The current locale used to convert a wide string literal into corresponding wide
27991 <li> The value of a string literal containing a multibyte character or escape sequence not
27993 <li> The encoding of any of wchar_t, char16_t, and char32_t where the
27994 corresponding standard encoding macro (__STDC_ISO_10646__,
27996 <!--page 587 -->
27997 </ul>
28001 <ul>
28002 <li> Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
28003 <li> Whether signed integer types are represented using sign and magnitude, two's
28004 complement, or ones' complement, and whether the extraordinary value is a trap
28006 <li> The rank of any extended integer type relative to another extended integer type with
28008 <li> The result of, or the signal raised by, converting an integer to a signed integer type
28009 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
28011 </ul>
28015 <ul>
28016 <li> The accuracy of the floating-point operations and of the library functions in
28017 <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>).
28018 <li> The accuracy of the conversions between floating-point internal representations and
28019 string representations performed by the library functions in <a href="#7.21"><stdio.h></a>,
28020 <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>).
28021 <li> The rounding behaviors characterized by non-standard values of FLT_ROUNDS
28023 <li> The evaluation methods characterized by non-standard negative values of
28025 <li> The direction of rounding when an integer is converted to a floating-point number that
28027 <li> The direction of rounding when a floating-point number is converted to a narrower
28029 <li> How the nearest representable value or the larger or smaller representable value
28030 immediately adjacent to the nearest representable value is chosen for certain floating
28032 <li> Whether and how floating expressions are contracted when not disallowed by the
28035 <li> Additional floating-point exceptions, rounding modes, environments, and
28038 <!--page 588 -->
28039 </ul>
28043 <ul>
28044 <li> The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
28045 <li> The size of the result of subtracting two pointers to elements of the same array
28047 </ul>
28051 <ul>
28052 <li> The extent to which suggestions made by using the register storage-class
28054 <li> The extent to which suggestions made by using the inline function specifier are
28056 </ul>
28058 <h4><a name="J.3.9" href="#J.3.9">J.3.9 Structures, unions, enumerations, and bit-fields</a></h4>
28060 <ul>
28061 <li> Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
28063 <li> Allowable bit-field types other than _Bool, signed int, and unsigned int
28066 <li> Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
28068 <li> The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
28069 no problem unless binary data written by one implementation is read by another.
28071 </ul>
28075 <ul>
28076 <li> What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
28077 </ul>
28081 <ul>
28082 <li> The locations within #pragma directives where header name preprocessing tokens
28084 <li> How sequences in both forms of header names are mapped to headers or external
28086 <li> Whether the value of a character constant in a constant expression that controls
28087 conditional inclusion matches the value of the same character constant in the
28089 <li> Whether the value of a single-character character constant in a constant expression
28091 <!--page 589 -->
28092 <li> The places that are searched for an included < > delimited header, and how the places
28096 <li> The method by which preprocessing tokens (possibly resulting from macro
28097 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
28099 <li> Whether the # operator inserts a \ character before the \ character that begins a
28100 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
28101 <li> The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
28102 <li> The definitions for __DATE__ and __TIME__ when respectively, the date and
28104 </ul>
28108 <ul>
28109 <li> Any library facilities available to a freestanding program, other than the minimal set
28111 <li> The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
28112 <li> The representation of the floating-point status flags stored by the
28114 <li> Whether the feraiseexcept function raises the ''inexact'' floating-point
28115 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
28119 <li> The types defined for float_t and double_t when the value of the
28121 <li> Domain errors for the mathematics functions, other than those required by this
28123 <li> The values returned by the mathematics functions on domain errors or pole errors
28125 <li> The values returned by the mathematics functions on underflow range errors, whether
28126 errno is set to the value of the macro ERANGE when the integer expression
28127 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
28128 floating-point exception is raised when the integer expression math_errhandling
28130 <!--page 590 -->
28131 <li> Whether a domain error occurs or zero is returned when an fmod function has a
28133 <li> Whether a domain error occurs or zero is returned when a remainder function has
28137 <li> Whether a domain error occurs or zero is returned when a remquo function has a
28139 <li> Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
28140 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>).
28142 <li> Whether the last line of a text stream requires a terminating new-line character
28144 <li> Whether space characters that are written out to a text stream immediately before a
28146 <li> The number of null characters that may be appended to data written to a binary
28148 <li> Whether the file position indicator of an append-mode stream is initially positioned at
28150 <li> Whether a write on a text stream causes the associated file to be truncated beyond that
28155 <li> Whether the same file can be simultaneously open multiple times (<a href="#7.21.3">7.21.3</a>).
28156 <li> The nature and choice of encodings used for multibyte characters in files (<a href="#7.21.3">7.21.3</a>).
28158 <li> The effect if a file with the new name exists prior to a call to the rename function
28160 <li> Whether an open temporary file is removed upon abnormal program termination
28162 <li> Which changes of mode are permitted (if any), and under what circumstances
28164 <!--page 591 -->
28165 <li> The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
28166 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>).
28167 <li> The output for %p conversion in the fprintf or fwprintf function (<a href="#7.21.6.1">7.21.6.1</a>,
28169 <li> The interpretation of a - character that is neither the first nor the last character, nor
28170 the second where a ^ character is the first, in the scanlist for %[ conversion in the
28171 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>).
28172 <li> The set of sequences matched by a %p conversion and the interpretation of the
28173 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>).
28174 <li> The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
28175 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>).
28176 <li> The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
28177 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
28179 <li> Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
28180 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>).
28181 <li> Whether the calloc, malloc, and realloc functions return a null pointer or a
28182 pointer to an allocated object when the size requested is zero (<a href="#7.22.3">7.22.3</a>).
28183 <li> Whether open streams with unwritten buffered data are flushed, open streams are
28184 closed, or temporary files are removed when the abort or _Exit function is called
28186 <li> The termination status returned to the host environment by the abort, exit,
28187 _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>).
28188 <li> The value returned by the system function when its argument is not a null pointer
28191 <li> The range and precision of times representable in clock_t and time_t (<a href="#7.26">7.26</a>).
28193 <li> The replacement string for the %Z specifier to the strftime, and wcsftime
28194 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>).
28195 <li> Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
28196 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.10">F.10</a>).
28197 <!--page 592 -->
28198 </ul>
28202 <ul>
28203 <li> The values or expressions assigned to the macros specified in the headers
28204 <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>).
28205 <li> The result of attempting to indirectly access an object with automatic or thread
28206 storage duration from a thread other than the one with which it is associated (<a href="#6.2.4">6.2.4</a>).
28207 <li> The number, order, and encoding of bytes in any object (when not explicitly specified
28209 <li> Whether any extended alignments are supported and the contexts in which they are
28211 <li> Valid alignment values other than those returned by an alignof expression for
28213 <li> The value of the result of the sizeof and alignof operators (<a href="#6.5.3.4">6.5.3.4</a>).
28214 </ul>
28218 The following characteristics of a hosted environment are locale-specific and are required
28219 to be documented by the implementation:
28220 <ul>
28221 <li> Additional members of the source and execution character sets beyond the basic
28223 <li> The presence, meaning, and representation of additional multibyte characters in the
28225 <li> The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
28230 <li> The sets of characters tested for by the isalpha, isblank, islower, ispunct,
28231 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
28232 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>,
28233 <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>).
28235 <li> Additional subject sequences accepted by the numeric conversion functions (<a href="#7.22.1">7.22.1</a>,
28237 <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>).
28238 <!--page 593 -->
28239 <li> The contents of the error message strings set up by the strerror function
28241 <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>).
28242 <li> Character mappings that are supported by the towctrans function (<a href="#7.29.1">7.29.1</a>).
28243 <li> Character classifications that are supported by the iswctype function (<a href="#7.29.1">7.29.1</a>).
28244 </ul>
28248 The following extensions are widely used in many systems, but are not portable to all
28249 implementations. The inclusion of any extension that may cause a strictly conforming
28250 program to become invalid renders an implementation nonconforming. Examples of such
28251 extensions are new keywords, extra library functions declared in standard headers, or
28252 predefined macros with names that do not begin with an underscore.
28256 In a hosted environment, the main function receives a third argument, char *envp[],
28257 that points to a null-terminated array of pointers to char, each of which points to a string
28258 that provides information about the environment for this execution of the program
28263 Characters other than the underscore _, letters, and digits, that are not part of the basic
28264 source character set (such as the dollar sign $, or characters in national character sets)
28269 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
28273 A function identifier, or the identifier of an object the declaration of which contains the
28278 String literals are modifiable (in which case, identical string literals should denote distinct
28280 <!--page 594 -->
28284 Additional arithmetic types, such as __int128 or double double, and their
28285 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
28286 more range or precision than long double, may be used for evaluating expressions of
28287 other floating types, and may be used to define float_t or double_t.
28291 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
28294 A pointer to a function may be cast to a pointer to an object or to void, allowing a
28295 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
28299 A bit-field may be declared with a type other than _Bool, unsigned int, or
28304 The fortran function specifier may be used in a function declaration to indicate that
28305 calls suitable for FORTRAN should be generated, or that a different representation for the
28310 The asm keyword may be used to insert assembly language directly into the translator
28311 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
28312 <pre>
28313 asm ( character-string-literal );
28314 </pre>
28318 There may be more than one external definition for the identifier of an object, with or
28319 without the explicit use of the keyword extern; if the definitions disagree, or more than
28324 Macro names that do not begin with an underscore, describing the translation and
28325 execution environments, are defined by the implementation before translation begins
28327 <!--page 595 -->
28331 If any floating-point status flags are set on normal termination after all calls to functions
28332 registered by the atexit function have been made (see <a href="#7.22.4.4">7.22.4.4</a>), the implementation
28333 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
28337 Handlers for specific signals are called with extra arguments in addition to the signal
28340 <h4><a name="J.5.15" href="#J.5.15">J.5.15 Additional stream types and file-opening modes</a></h4>
28344 Additional file-opening modes may be specified by characters appended to the mode
28349 The file position indicator is decremented by each successful call to the ungetc or
28350 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>,
28355 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
28356 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
28358 <!--page 596 -->
28361 <pre>
28362 (normative)
28363 Bounds-checking interfaces
28364 </pre>
28368 Traditionally, the C Library has contained many functions that trust the programmer to
28369 provide output character arrays big enough to hold the result being produced. Not only
28370 do these functions not check that the arrays are big enough, they frequently lack the
28371 information needed to perform such checks. While it is possible to write safe, robust, and
28372 error-free code using the existing library, the library tends to promote programming styles
28373 that lead to mysterious failures if a result is too big for the provided array.
28375 A common programming style is to declare character arrays large enough to handle most
28376 practical cases. However, if these arrays are not large enough to handle the resulting
28377 strings, data can be written past the end of the array overwriting other data and program
28378 structures. The program never gets any indication that a problem exists, and so never has
28379 a chance to recover or to fail gracefully.
28381 Worse, this style of programming has compromised the security of computers and
28382 networks. Buffer overflows can often be exploited to run arbitrary code with the
28383 permissions of the vulnerable (defective) program.
28385 If the programmer writes runtime checks to verify lengths before calling library
28386 functions, then those runtime checks frequently duplicate work done inside the library
28387 functions, which discover string lengths as a side effect of doing their job.
28389 This annex provides alternative library functions that promote safer, more secure
28390 programming. The alternative functions verify that output buffers are large enough for
28391 the intended result and return a failure indicator if they are not. Data is never written past
28392 the end of an array. All string results are null terminated.
28394 This annex also addresses another problem that complicates writing robust code:
28395 functions that are not reentrant because they return pointers to static objects owned by the
28396 function. Such functions can be troublesome since a previously returned result can
28397 change if the function is called again, perhaps by another thread.
28398 <!--page 597 -->
28402 This annex specifies a series of optional extensions that can be useful in the mitigation of
28403 security vulnerabilities in programs, and comprise new functions, macros, and types
28404 declared or defined in existing standard headers.
28406 An implementation that defines __STDC_LIB_EXT1__ shall conform to the
28409 Subclause <a href="#K.3">K.3</a> should be read as if it were merged into the parallel structure of named
28410 subclauses of clause 7.
28413 <p><small><a name="note367" href="#note367">367)</a> Implementations that do not define __STDC_LIB_EXT1__ are not required to conform to these
28414 specifications.
28415 </small>
28423 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are not
28424 declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
28425 defined as a macro which expands to the integer constant 0 at the point in the source file
28426 where the appropriate header is first included.
28428 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are
28429 declared and defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
28430 defined as a macro which expands to the integer constant 1 at the point in the source file
28433 It is implementation-defined whether the functions, macros, and types declared or defined
28434 in <a href="#K.3">K.3</a> and its subclauses are declared or defined by their respective headers if
28435 __STDC_WANT_LIB_EXT1__ is not defined as a macro at the point in the source file
28438 Within a preprocessing translation unit, __STDC_WANT_LIB_EXT1__ shall be
28439 defined identically for all inclusions of any headers from subclause <a href="#K.3">K.3</a>. If
28440 __STDC_WANT_LIB_EXT1__ is defined differently for any such inclusion, the
28441 implementation shall issue a diagnostic as if a preprocessor error directive were used.
28444 <!--page 598 -->
28447 <p><small><a name="note368" href="#note368">368)</a> Future revisions of this International Standard may define meanings for other values of
28448 __STDC_WANT_LIB_EXT1__.
28449 </small>
28450 <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
28451 headers. All other names are not reserved, and a conforming implementation is not permitted to use
28452 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
28453 unreserved name is defined in a header when __STDC_WANT_LIB_EXT1__ is defined as 0, the
28454 implementation is not conforming.
28455 </small>
28459 Each macro name in any of the following subclauses is reserved for use as specified if it
28460 is defined by any of its associated headers when included; unless explicitly stated
28463 All identifiers with external linkage in any of the following subclauses are reserved for
28464 use as identifiers with external linkage if any of them are used by the program. None of
28465 them are reserved if none of them are used.
28467 Each identifier with file scope listed in any of the following subclauses is reserved for use
28468 as a macro name and as an identifier with file scope in the same name space if it is
28469 defined by any of its associated headers when included.
28473 An implementation may set errno for the functions defined in this annex, but is not
28474 required to.
28478 Most functions in this annex include as part of their specification a list of runtime-
28479 constraints. These runtime-constraints are requirements on the program using the
28482 Implementations shall verify that the runtime-constraints for a function are not violated
28483 by the program. If a runtime-constraint is violated, the implementation shall call the
28484 currently registered runtime-constraint handler (see set_constraint_handler_s
28485 in <a href="#7.22"><stdlib.h></a>). Multiple runtime-constraint violations in the same call to a library
28486 function result in only one call to the runtime-constraint handler. It is unspecified which
28487 one of the multiple runtime-constraint violations cause the handler to be called.
28489 If the runtime-constraints section for a function states an action to be performed when a
28490 runtime-constraint violation occurs, the function shall perform the action before calling
28491 the runtime-constraint handler. If the runtime-constraints section lists actions that are
28492 prohibited when a runtime-constraint violation occurs, then such actions are prohibited to
28493 the function both before calling the handler and after the handler returns.
28495 The runtime-constraint handler might not return. If the handler does return, the library
28496 function whose runtime-constraint was violated shall return some indication of failure as
28497 given by the returns section in the function's specification.
28501 <!--page 599 -->
28504 <p><small><a name="note370" href="#note370">370)</a> Although runtime-constraints replace many cases of undefined behavior, undefined behavior still
28505 exists in this annex. Implementations are free to detect any case of undefined behavior and treat it as a
28506 runtime-constraint violation by calling the runtime-constraint handler. This license comes directly
28507 from the definition of undefined behavior.
28508 </small>
28514 The type is
28515 <pre>
28516 errno_t
28517 </pre>
28521 <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
28522 with the values that might be found in errno. For example, a function which returns the value of
28523 errno might be declared as having the return type errno_t.
28524 </small>
28530 The type is
28531 <pre>
28532 rsize_t
28533 </pre>
28537 <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>.
28538 </small>
28544 The macro is
28545 <pre>
28546 RSIZE_MAX
28547 </pre>
28548 which expands to a value<sup><a href="#note373"><b>373)</b></a></sup> of type size_t. Functions that have parameters of type
28549 rsize_t consider it a runtime-constraint violation if the values of those parameters are
28550 greater than RSIZE_MAX.
28553 Extremely large object sizes are frequently a sign that an object's size was calculated
28554 incorrectly. For example, negative numbers appear as very large positive numbers when
28555 converted to an unsigned type like size_t. Also, some implementations do not support
28556 objects as large as the maximum value that can be represented by type size_t.
28558 For those reasons, it is sometimes beneficial to restrict the range of object sizes to detect
28559 programming errors. For implementations targeting machines with large address spaces,
28560 it is recommended that RSIZE_MAX be defined as the smaller of the size of the largest
28562 some legitimate, but very large, objects. Implementations targeting machines with small
28563 address spaces may wish to define RSIZE_MAX as SIZE_MAX, which means that there
28565 <!--page 600 -->
28566 is no object size that is considered a runtime-constraint violation.
28569 <p><small><a name="note373" href="#note373">373)</a> The macro RSIZE_MAX need not expand to a constant expression.
28570 </small>
28576 The macros are
28577 <pre>
28578 L_tmpnam_s
28579 </pre>
28580 which expands to an integer constant expression that is the size needed for an array of
28581 char large enough to hold a temporary file name string generated by the tmpnam_s
28582 function;
28583 <pre>
28584 TMP_MAX_S
28585 </pre>
28586 which expands to an integer constant expression that is the maximum number of unique
28587 file names that can be generated by the tmpnam_s function.
28589 The types are
28590 <pre>
28591 errno_t
28592 </pre>
28593 which is type int; and
28594 <pre>
28595 rsize_t
28596 </pre>
28597 which is the type size_t.
28604 <pre>
28605 #define __STDC_WANT_LIB_EXT1__ 1
28607 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
28608 </pre>
28609 Runtime-constraints
28611 streamptr shall not be a null pointer.
28613 If there is a runtime-constraint violation, tmpfile_s does not attempt to create a file.
28616 The tmpfile_s function creates a temporary binary file that is different from any other
28617 existing file and that will automatically be removed when it is closed or at program
28618 termination. If the program terminates abnormally, whether an open temporary file is
28619 removed is implementation-defined. The file is opened for update with "wb+" mode
28620 with the meaning that mode has in the fopen_s function (including the mode's effect
28621 on exclusive access and file permissions).
28622 <!--page 601 -->
28624 If the file was created successfully, then the pointer to FILE pointed to by streamptr
28625 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
28626 to FILE pointed to by streamptr will be set to a null pointer.
28628 It should be possible to open at least TMP_MAX_S temporary files during the lifetime of
28629 the program (this limit may be shared with tmpnam_s) and there should be no limit on
28630 the number simultaneously open other than this limit and any limit on the number of open
28631 files (FOPEN_MAX).
28634 The tmpfile_s function returns zero if it created the file. If it did not create the file or
28635 there was a runtime-constraint violation, tmpfile_s returns a nonzero value.
28640 <pre>
28641 #define __STDC_WANT_LIB_EXT1__ 1
28643 errno_t tmpnam_s(char *s, rsize_t maxsize);
28644 </pre>
28645 Runtime-constraints
28647 s shall not be a null pointer. maxsize shall be less than or equal to RSIZE_MAX.
28648 maxsize shall be greater than the length of the generated file name string.
28651 The tmpnam_s function generates a string that is a valid file name and that is not the
28652 same as the name of an existing file.<sup><a href="#note374"><b>374)</b></a></sup> The function is potentially capable of generating
28653 TMP_MAX_S different strings, but any or all of them may already be in use by existing
28654 files and thus not be suitable return values. The lengths of these strings shall be less than
28655 the value of the L_tmpnam_s macro.
28657 The tmpnam_s function generates a different string each time it is called.
28659 It is assumed that s points to an array of at least maxsize characters. This array will be
28660 set to generated string, as specified below.
28664 <!--page 602 -->
28666 The implementation shall behave as if no library function except tmpnam calls the
28670 After a program obtains a file name using the tmpnam_s function and before the
28671 program creates a file with that name, the possibility exists that someone else may create
28672 a file with that same name. To avoid this race condition, the tmpfile_s function
28673 should be used instead of tmpnam_s when possible. One situation that requires the use
28674 of the tmpnam_s function is when the program needs to create a temporary directory
28675 rather than a temporary file.
28678 If no suitable string can be generated, or if there is a runtime-constraint violation, the
28679 tmpnam_s function writes a null character to s[0] (only if s is not null and maxsize
28680 is greater than zero) and returns a nonzero value.
28682 Otherwise, the tmpnam_s function writes the string in the array pointed to by s and
28683 returns zero.
28686 The value of the macro TMP_MAX_S shall be at least 25.
28689 <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
28690 their names should not collide with those generated by conventional naming rules for the
28691 implementation. It is still necessary to use the remove function to remove such files when their use
28692 is ended, and before program termination. Implementations should take care in choosing the patterns
28693 used for names returned by tmpnam_s. For example, making a thread id part of the names avoids the
28694 race condition and possible conflict when multiple programs run simultaneously by the same user
28695 generate the same temporary file names.
28696 </small>
28697 <p><small><a name="note375" href="#note375">375)</a> An implementation may have tmpnam call tmpnam_s (perhaps so there is only one naming
28698 convention for temporary files), but this is not required.
28699 </small>
28706 <pre>
28707 #define __STDC_WANT_LIB_EXT1__ 1
28709 errno_t fopen_s(FILE * restrict * restrict streamptr,
28710 const char * restrict filename,
28711 const char * restrict mode);
28712 </pre>
28713 Runtime-constraints
28715 None of streamptr, filename, or mode shall be a null pointer.
28717 If there is a runtime-constraint violation, fopen_s does not attempt to open a file.
28718 Furthermore, if streamptr is not a null pointer, fopen_s sets *streamptr to the
28719 null pointer.
28724 <!--page 603 -->
28727 The fopen_s function opens the file whose name is the string pointed to by
28728 filename, and associates a stream with it.
28730 The mode string shall be as described for fopen, with the addition that modes starting
28731 with the character 'w' or 'a' may be preceded by the character 'u', see below:
28732 uw truncate to zero length or create text file for writing, default
28733 <pre>
28734 permissions
28735 </pre>
28736 uwx create text file for writing, default permissions
28737 ua append; open or create text file for writing at end-of-file, default
28738 <pre>
28739 permissions
28740 </pre>
28741 uwb truncate to zero length or create binary file for writing, default
28742 <pre>
28743 permissions
28744 </pre>
28745 uwbx create binary file for writing, default permissions
28746 uab append; open or create binary file for writing at end-of-file, default
28747 <pre>
28748 permissions
28749 </pre>
28750 uw+ truncate to zero length or create text file for update, default
28751 <pre>
28752 permissions
28753 </pre>
28754 uw+x create text file for update, default permissions
28755 ua+ append; open or create text file for update, writing at end-of-file,
28756 <pre>
28757 default permissions
28758 </pre>
28759 uw+b or uwb+ truncate to zero length or create binary file for update, default
28760 <pre>
28761 permissions
28762 </pre>
28763 uw+bx or uwb+x create binary file for update, default permissions
28764 ua+b or uab+ append; open or create binary file for update, writing at end-of-file,
28765 <pre>
28766 default permissions
28767 </pre>
28769 Opening a file with exclusive mode ('x' as the last character in the mode argument)
28770 fails if the file already exists or cannot be created.
28772 To the extent that the underlying system supports the concepts, files opened for writing
28773 shall be opened with exclusive (also known as non-shared) access. If the file is being
28774 created, and the first character of the mode string is not 'u', to the extent that the
28775 underlying system supports it, the file shall have a file permission that prevents other
28776 users on the system from accessing the file. If the file is being created and first character
28777 of the mode string is 'u', then by the time the file has been closed, it shall have the
28780 If the file was opened successfully, then the pointer to FILE pointed to by streamptr
28781 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
28784 <!--page 604 -->
28785 to FILE pointed to by streamptr will be set to a null pointer.
28788 The fopen_s function returns zero if it opened the file. If it did not open the file or if
28789 there was a runtime-constraint violation, fopen_s returns a nonzero value.
28792 <p><small><a name="note376" href="#note376">376)</a> These are the same permissions that the file would have been created with by fopen.
28793 </small>
28798 <pre>
28799 #define __STDC_WANT_LIB_EXT1__ 1
28801 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
28802 const char * restrict filename,
28803 const char * restrict mode,
28804 FILE * restrict stream);
28805 </pre>
28806 Runtime-constraints
28808 None of newstreamptr, mode, and stream shall be a null pointer.
28810 If there is a runtime-constraint violation, freopen_s neither attempts to close any file
28811 associated with stream nor attempts to open a file. Furthermore, if newstreamptr is
28812 not a null pointer, fopen_s sets *newstreamptr to the null pointer.
28815 The freopen_s function opens the file whose name is the string pointed to by
28816 filename and associates the stream pointed to by stream with it. The mode
28817 argument has the same meaning as in the fopen_s function (including the mode's effect
28818 on exclusive access and file permissions).
28820 If filename is a null pointer, the freopen_s function attempts to change the mode of
28821 the stream to that specified by mode, as if the name of the file currently associated with
28822 the stream had been used. It is implementation-defined which changes of mode are
28823 permitted (if any), and under what circumstances.
28825 The freopen_s function first attempts to close any file that is associated with stream.
28826 Failure to close the file is ignored. The error and end-of-file indicators for the stream are
28827 cleared.
28829 If the file was opened successfully, then the pointer to FILE pointed to by
28830 newstreamptr will be set to the value of stream. Otherwise, the pointer to FILE
28831 pointed to by newstreamptr will be set to a null pointer.
28834 The freopen_s function returns zero if it opened the file. If it did not open the file or
28835 there was a runtime-constraint violation, freopen_s returns a nonzero value.
28836 <!--page 605 -->
28840 Unless explicitly stated otherwise, if the execution of a function described in this
28841 subclause causes copying to take place between objects that overlap, the objects take on
28842 unspecified values.
28847 <pre>
28848 #define __STDC_WANT_LIB_EXT1__ 1
28850 int fprintf_s(FILE * restrict stream,
28851 const char * restrict format, ...);
28852 </pre>
28853 Runtime-constraints
28855 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note377"><b>377)</b></a></sup> (modified or
28856 not by flags, field width, or precision) shall not appear in the string pointed to by
28857 format. Any argument to fprintf_s corresponding to a %s specifier shall not be a
28858 null pointer.
28860 If there is a runtime-constraint violation,<sup><a href="#note378"><b>378)</b></a></sup> the fprintf_s function does not attempt
28861 to produce further output, and it is unspecified to what extent fprintf_s produced
28862 output before discovering the runtime-constraint violation.
28865 The fprintf_s function is equivalent to the fprintf function except for the explicit
28866 runtime-constraints listed above.
28869 The fprintf_s function returns the number of characters transmitted, or a negative
28870 value if an output error, encoding error, or runtime-constraint violation occurred.
28875 <!--page 606 -->
28878 <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
28879 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
28880 format string was %%n.
28881 </small>
28882 <p><small><a name="note378" href="#note378">378)</a> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
28883 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
28884 constraint violation.
28885 </small>
28890 <pre>
28891 #define __STDC_WANT_LIB_EXT1__ 1
28893 int fscanf_s(FILE * restrict stream,
28894 const char * restrict format, ...);
28895 </pre>
28896 Runtime-constraints
28898 Neither stream nor format shall be a null pointer. Any argument indirected though in
28899 order to store converted input shall not be a null pointer.
28901 If there is a runtime-constraint violation,<sup><a href="#note379"><b>379)</b></a></sup> the fscanf_s function does not attempt to
28902 perform further input, and it is unspecified to what extent fscanf_s performed input
28903 before discovering the runtime-constraint violation.
28906 The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion
28907 specifiers apply to a pair of arguments (unless assignment suppression is indicated by a
28908 *). The first of these arguments is the same as for fscanf. That argument is
28909 immediately followed in the argument list by the second argument, which has type
28910 rsize_t and gives the number of elements in the array pointed to by the first argument
28911 of the pair. If the first argument points to a scalar object, it is considered to be an array of
28914 A matching failure occurs if the number of elements in a receiving object is insufficient to
28915 hold the converted input (including any trailing null character).
28918 The fscanf_s function returns the value of the macro EOF if an input failure occurs
28919 before any conversion or if there is a runtime-constraint violation. Otherwise, the
28921 <!--page 607 -->
28922 fscanf_s function returns the number of input items assigned, which can be fewer than
28923 provided for, or even zero, in the event of an early matching failure.
28925 EXAMPLE 1 The call:
28926 <pre>
28927 #define __STDC_WANT_LIB_EXT1__ 1
28929 /* ... */
28930 int n, i; float x; char name[50];
28932 </pre>
28933 with the input line:
28934 <pre>
28935 25 54.32E-1 thompson
28936 </pre>
28937 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
28938 thompson\0.
28941 EXAMPLE 2 The call:
28942 <pre>
28943 #define __STDC_WANT_LIB_EXT1__ 1
28945 /* ... */
28946 int n; char s[5];
28947 n = fscanf_s(stdin, "%s", s, sizeof s);
28948 </pre>
28949 with the input line:
28950 <pre>
28951 hello
28952 </pre>
28953 will assign to n the value 0 since a matching failure occurred because the sequence hello\0 requires an
28954 array of six characters to store it.
28958 <p><small><a name="note379" href="#note379">379)</a> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
28959 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
28960 constraint violation.
28961 </small>
28962 <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
28963 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
28964 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
28965 the format is not known at translation time. For example, an implementation may issue a diagnostic
28966 for each argument after format that has of type pointer to one of char, signed char,
28967 unsigned char, or void that is not followed by an argument of a type compatible with
28968 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
28969 using the hh length modifier, a length argument must follow the pointer argument. Another useful
28970 diagnostic could flag any non-pointer argument following format that did not have a type
28971 compatible with rsize_t.
28972 </small>
28977 <pre>
28978 #define __STDC_WANT_LIB_EXT1__ 1
28980 int printf_s(const char * restrict format, ...);
28981 </pre>
28982 Runtime-constraints
28984 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
28985 width, or precision) shall not appear in the string pointed to by format. Any argument
28986 to printf_s corresponding to a %s specifier shall not be a null pointer.
28988 If there is a runtime-constraint violation, the printf_s function does not attempt to
28989 produce further output, and it is unspecified to what extent printf_s produced output
28990 before discovering the runtime-constraint violation.
28993 <!--page 608 -->
28996 The printf_s function is equivalent to the printf function except for the explicit
28997 runtime-constraints listed above.
29000 The printf_s function returns the number of characters transmitted, or a negative
29001 value if an output error, encoding error, or runtime-constraint violation occurred.
29004 <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
29005 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
29006 format string was %%n.
29007 </small>
29012 <pre>
29013 #define __STDC_WANT_LIB_EXT1__ 1
29015 int scanf_s(const char * restrict format, ...);
29016 </pre>
29017 Runtime-constraints
29019 format shall not be a null pointer. Any argument indirected though in order to store
29020 converted input shall not be a null pointer.
29022 If there is a runtime-constraint violation, the scanf_s function does not attempt to
29023 perform further input, and it is unspecified to what extent scanf_s performed input
29024 before discovering the runtime-constraint violation.
29027 The scanf_s function is equivalent to fscanf_s with the argument stdin
29028 interposed before the arguments to scanf_s.
29031 The scanf_s function returns the value of the macro EOF if an input failure occurs
29032 before any conversion or if there is a runtime-constraint violation. Otherwise, the
29033 scanf_s function returns the number of input items assigned, which can be fewer than
29034 provided for, or even zero, in the event of an early matching failure.
29039 <pre>
29040 #define __STDC_WANT_LIB_EXT1__ 1
29042 int snprintf_s(char * restrict s, rsize_t n,
29043 const char * restrict format, ...);
29044 </pre>
29045 Runtime-constraints
29047 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
29048 than RSIZE_MAX. The %n specifier<sup><a href="#note382"><b>382)</b></a></sup> (modified or not by flags, field width, or
29049 precision) shall not appear in the string pointed to by format. Any argument to
29050 <!--page 609 -->
29051 snprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
29052 error shall occur.
29054 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
29055 than zero and less than RSIZE_MAX, then the snprintf_s function sets s[0] to the
29056 null character.
29059 The snprintf_s function is equivalent to the snprintf function except for the
29060 explicit runtime-constraints listed above.
29062 The snprintf_s function, unlike sprintf_s, will truncate the result to fit within the
29063 array pointed to by s.
29066 The snprintf_s function returns the number of characters that would have been
29067 written had n been sufficiently large, not counting the terminating null character, or a
29068 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
29069 output has been completely written if and only if the returned value is nonnegative and
29070 less than n.
29073 <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
29074 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
29075 format string was %%n.
29076 </small>
29081 <pre>
29082 #define __STDC_WANT_LIB_EXT1__ 1
29084 int sprintf_s(char * restrict s, rsize_t n,
29085 const char * restrict format, ...);
29086 </pre>
29087 Runtime-constraints
29089 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
29090 than RSIZE_MAX. The number of characters (including the trailing null) required for the
29091 result to be written to the array pointed to by s shall not be greater than n. The %n
29092 specifier<sup><a href="#note383"><b>383)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
29093 string pointed to by format. Any argument to sprintf_s corresponding to a %s
29094 specifier shall not be a null pointer. No encoding error shall occur.
29098 <!--page 610 -->
29100 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
29101 than zero and less than RSIZE_MAX, then the sprintf_s function sets s[0] to the
29102 null character.
29105 The sprintf_s function is equivalent to the sprintf function except for the
29106 parameter n and the explicit runtime-constraints listed above.
29108 The sprintf_s function, unlike snprintf_s, treats a result too big for the array
29109 pointed to by s as a runtime-constraint violation.
29112 If no runtime-constraint violation occurred, the sprintf_s function returns the number
29113 of characters written in the array, not counting the terminating null character. If an
29114 encoding error occurred, sprintf_s returns a negative value. If any other runtime-
29115 constraint violation occurred, sprintf_s returns zero.
29118 <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
29119 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
29120 format string was %%n.
29121 </small>
29126 <pre>
29127 #define __STDC_WANT_LIB_EXT1__ 1
29129 int sscanf_s(const char * restrict s,
29130 const char * restrict format, ...);
29131 </pre>
29132 Runtime-constraints
29134 Neither s nor format shall be a null pointer. Any argument indirected though in order
29135 to store converted input shall not be a null pointer.
29137 If there is a runtime-constraint violation, the sscanf_s function does not attempt to
29138 perform further input, and it is unspecified to what extent sscanf_s performed input
29139 before discovering the runtime-constraint violation.
29142 The sscanf_s function is equivalent to fscanf_s, except that input is obtained from
29143 a string (specified by the argument s) rather than from a stream. Reaching the end of the
29144 string is equivalent to encountering end-of-file for the fscanf_s function. If copying
29145 takes place between objects that overlap, the objects take on unspecified values.
29148 The sscanf_s function returns the value of the macro EOF if an input failure occurs
29149 before any conversion or if there is a runtime-constraint violation. Otherwise, the
29150 sscanf_s function returns the number of input items assigned, which can be fewer than
29151 provided for, or even zero, in the event of an early matching failure.
29152 <!--page 611 -->
29157 <pre>
29158 #define __STDC_WANT_LIB_EXT1__ 1
29161 int vfprintf_s(FILE * restrict stream,
29162 const char * restrict format,
29163 va_list arg);
29164 </pre>
29165 Runtime-constraints
29167 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note384"><b>384)</b></a></sup> (modified or
29168 not by flags, field width, or precision) shall not appear in the string pointed to by
29169 format. Any argument to vfprintf_s corresponding to a %s specifier shall not be a
29170 null pointer.
29172 If there is a runtime-constraint violation, the vfprintf_s function does not attempt to
29173 produce further output, and it is unspecified to what extent vfprintf_s produced
29174 output before discovering the runtime-constraint violation.
29177 The vfprintf_s function is equivalent to the vfprintf function except for the
29178 explicit runtime-constraints listed above.
29181 The vfprintf_s function returns the number of characters transmitted, or a negative
29182 value if an output error, encoding error, or runtime-constraint violation occurred.
29185 <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
29186 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
29187 format string was %%n.
29188 </small>
29193 <pre>
29194 #define __STDC_WANT_LIB_EXT1__ 1
29197 int vfscanf_s(FILE * restrict stream,
29198 const char * restrict format,
29199 va_list arg);
29200 </pre>
29205 <!--page 612 -->
29206 Runtime-constraints
29208 Neither stream nor format shall be a null pointer. Any argument indirected though in
29209 order to store converted input shall not be a null pointer.
29211 If there is a runtime-constraint violation, the vfscanf_s function does not attempt to
29212 perform further input, and it is unspecified to what extent vfscanf_s performed input
29213 before discovering the runtime-constraint violation.
29216 The vfscanf_s function is equivalent to fscanf_s, with the variable argument list
29217 replaced by arg, which shall have been initialized by the va_start macro (and
29218 possibly subsequent va_arg calls). The vfscanf_s function does not invoke the
29222 The vfscanf_s function returns the value of the macro EOF if an input failure occurs
29223 before any conversion or if there is a runtime-constraint violation. Otherwise, the
29224 vfscanf_s function returns the number of input items assigned, which can be fewer
29225 than provided for, or even zero, in the event of an early matching failure.
29228 <p><small><a name="note385" href="#note385">385)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
29229 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
29230 indeterminate.
29231 </small>
29236 <pre>
29237 #define __STDC_WANT_LIB_EXT1__ 1
29240 int vprintf_s(const char * restrict format,
29241 va_list arg);
29242 </pre>
29243 Runtime-constraints
29245 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
29246 width, or precision) shall not appear in the string pointed to by format. Any argument
29247 to vprintf_s corresponding to a %s specifier shall not be a null pointer.
29249 If there is a runtime-constraint violation, the vprintf_s function does not attempt to
29250 produce further output, and it is unspecified to what extent vprintf_s produced output
29251 before discovering the runtime-constraint violation.
29253 <!--page 613 -->
29256 The vprintf_s function is equivalent to the vprintf function except for the explicit
29257 runtime-constraints listed above.
29260 The vprintf_s function returns the number of characters transmitted, or a negative
29261 value if an output error, encoding error, or runtime-constraint violation occurred.
29264 <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
29265 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
29266 format string was %%n.
29267 </small>
29272 <pre>
29273 #define __STDC_WANT_LIB_EXT1__ 1
29276 int vscanf_s(const char * restrict format,
29277 va_list arg);
29278 </pre>
29279 Runtime-constraints
29281 format shall not be a null pointer. Any argument indirected though in order to store
29282 converted input shall not be a null pointer.
29284 If there is a runtime-constraint violation, the vscanf_s function does not attempt to
29285 perform further input, and it is unspecified to what extent vscanf_s performed input
29286 before discovering the runtime-constraint violation.
29289 The vscanf_s function is equivalent to scanf_s, with the variable argument list
29290 replaced by arg, which shall have been initialized by the va_start macro (and
29291 possibly subsequent va_arg calls). The vscanf_s function does not invoke the
29295 The vscanf_s function returns the value of the macro EOF if an input failure occurs
29296 before any conversion or if there is a runtime-constraint violation. Otherwise, the
29297 vscanf_s function returns the number of input items assigned, which can be fewer than
29298 provided for, or even zero, in the event of an early matching failure.
29303 <!--page 614 -->
29306 <p><small><a name="note387" href="#note387">387)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
29307 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
29308 indeterminate.
29309 </small>
29314 <pre>
29315 #define __STDC_WANT_LIB_EXT1__ 1
29318 int vsnprintf_s(char * restrict s, rsize_t n,
29319 const char * restrict format,
29320 va_list arg);
29321 </pre>
29322 Runtime-constraints
29324 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
29325 than RSIZE_MAX. The %n specifier<sup><a href="#note388"><b>388)</b></a></sup> (modified or not by flags, field width, or
29326 precision) shall not appear in the string pointed to by format. Any argument to
29327 vsnprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
29328 error shall occur.
29330 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
29331 than zero and less than RSIZE_MAX, then the vsnprintf_s function sets s[0] to the
29332 null character.
29335 The vsnprintf_s function is equivalent to the vsnprintf function except for the
29336 explicit runtime-constraints listed above.
29338 The vsnprintf_s function, unlike vsprintf_s, will truncate the result to fit within
29339 the array pointed to by s.
29342 The vsnprintf_s function returns the number of characters that would have been
29343 written had n been sufficiently large, not counting the terminating null character, or a
29344 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
29345 output has been completely written if and only if the returned value is nonnegative and
29346 less than n.
29351 <!--page 615 -->
29354 <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
29355 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
29356 format string was %%n.
29357 </small>
29362 <pre>
29363 #define __STDC_WANT_LIB_EXT1__ 1
29366 int vsprintf_s(char * restrict s, rsize_t n,
29367 const char * restrict format,
29368 va_list arg);
29369 </pre>
29370 Runtime-constraints
29372 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
29373 than RSIZE_MAX. The number of characters (including the trailing null) required for the
29374 result to be written to the array pointed to by s shall not be greater than n. The %n
29375 specifier<sup><a href="#note389"><b>389)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
29376 string pointed to by format. Any argument to vsprintf_s corresponding to a %s
29377 specifier shall not be a null pointer. No encoding error shall occur.
29379 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
29380 than zero and less than RSIZE_MAX, then the vsprintf_s function sets s[0] to the
29381 null character.
29384 The vsprintf_s function is equivalent to the vsprintf function except for the
29385 parameter n and the explicit runtime-constraints listed above.
29387 The vsprintf_s function, unlike vsnprintf_s, treats a result too big for the array
29388 pointed to by s as a runtime-constraint violation.
29391 If no runtime-constraint violation occurred, the vsprintf_s function returns the
29392 number of characters written in the array, not counting the terminating null character. If
29393 an encoding error occurred, vsprintf_s returns a negative value. If any other
29394 runtime-constraint violation occurred, vsprintf_s returns zero.
29399 <!--page 616 -->
29402 <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
29403 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
29404 format string was %%n.
29405 </small>
29410 <pre>
29411 #define __STDC_WANT_LIB_EXT1__ 1
29414 int vsscanf_s(const char * restrict s,
29415 const char * restrict format,
29416 va_list arg);
29417 </pre>
29418 Runtime-constraints
29420 Neither s nor format shall be a null pointer. Any argument indirected though in order
29421 to store converted input shall not be a null pointer.
29423 If there is a runtime-constraint violation, the vsscanf_s function does not attempt to
29424 perform further input, and it is unspecified to what extent vsscanf_s performed input
29425 before discovering the runtime-constraint violation.
29428 The vsscanf_s function is equivalent to sscanf_s, with the variable argument list
29429 replaced by arg, which shall have been initialized by the va_start macro (and
29430 possibly subsequent va_arg calls). The vsscanf_s function does not invoke the
29434 The vsscanf_s function returns the value of the macro EOF if an input failure occurs
29435 before any conversion or if there is a runtime-constraint violation. Otherwise, the
29436 vscanf_s function returns the number of input items assigned, which can be fewer than
29437 provided for, or even zero, in the event of an early matching failure.
29440 <p><small><a name="note390" href="#note390">390)</a> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
29441 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
29442 indeterminate.
29443 </small>
29450 <pre>
29451 #define __STDC_WANT_LIB_EXT1__ 1
29453 char *gets_s(char *s, rsize_t n);
29454 </pre>
29459 <!--page 617 -->
29460 Runtime-constraints
29462 s shall not be a null pointer. n shall neither be equal to zero nor be greater than
29463 RSIZE_MAX. A new-line character, end-of-file, or read error shall occur within reading
29466 If there is a runtime-constraint violation, s[0] is set to the null character, and characters
29467 are read and discarded from stdin until a new-line character is read, or end-of-file or a
29468 read error occurs.
29471 The gets_s function reads at most one less than the number of characters specified by n
29472 from the stream pointed to by stdin, into the array pointed to by s. No additional
29473 characters are read after a new-line character (which is discarded) or after end-of-file.
29474 The discarded new-line character does not count towards number of characters read. A
29475 null character is written immediately after the last character read into the array.
29477 If end-of-file is encountered and no characters have been read into the array, or if a read
29478 error occurs during the operation, then s[0] is set to the null character, and the other
29479 elements of s take unspecified values.
29482 The fgets function allows properly-written programs to safely process input lines too
29483 long to store in the result array. In general this requires that callers of fgets pay
29484 attention to the presence or absence of a new-line character in the result array. Consider
29485 using fgets (along with any needed processing based on new-line characters) instead of
29486 gets_s.
29489 The gets_s function returns s if successful. If there was a runtime-constraint violation,
29490 or if end-of-file is encountered and no characters have been read into the array, or if a
29491 read error occurs during the operation, then a null pointer is returned.
29496 <!--page 618 -->
29499 <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
29500 a line of input to overflow the buffer to store it. Unlike the fgets function, gets_s maintains a
29501 one-to-one relationship between input lines and successful calls to gets_s. Programs that use gets
29502 expect such a relationship.
29503 </small>
29509 The types are
29510 <pre>
29511 errno_t
29512 </pre>
29513 which is type int; and
29514 <pre>
29515 rsize_t
29516 </pre>
29517 which is the type size_t; and
29518 <pre>
29519 constraint_handler_t
29520 </pre>
29521 which has the following definition
29522 <pre>
29523 typedef void (*constraint_handler_t)(
29524 const char * restrict msg,
29525 void * restrict ptr,
29526 errno_t error);
29527 </pre>
29531 <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>
29534 <pre>
29535 #define __STDC_WANT_LIB_EXT1__ 1
29537 constraint_handler_t set_constraint_handler_s(
29538 constraint_handler_t handler);
29539 </pre>
29542 The set_constraint_handler_s function sets the runtime-constraint handler to
29543 be handler. The runtime-constraint handler is the function to be called when a library
29544 function detects a runtime-constraint violation. Only the most recent handler registered
29545 with set_constraint_handler_s is called when a runtime-constraint violation
29546 occurs.
29548 When the handler is called, it is passed the following arguments in the following order:
29549 <ol>
29550 <li> A pointer to a character string describing the runtime-constraint violation.
29551 <li> A null pointer or a pointer to an implementation defined object.
29552 <li> If the function calling the handler has a return type declared as errno_t, the
29553 return value of the function is passed. Otherwise, a positive value of type
29554 errno_t is passed.
29555 <!--page 619 -->
29556 </ol>
29558 The implementation has a default constraint handler that is used if no calls to the
29559 set_constraint_handler_s function have been made. The behavior of the
29560 default handler is implementation-defined, and it may cause the program to exit or abort.
29562 If the handler argument to set_constraint_handler_s is a null pointer, the
29563 implementation default handler becomes the current constraint handler.
29566 The set_constraint_handler_s function returns a pointer to the previously
29570 <p><small><a name="note392" href="#note392">392)</a> If the previous handler was registered by calling set_constraint_handler_s with a null
29571 pointer argument, a pointer to the implementation default handler is returned (not NULL).
29572 </small>
29577 <pre>
29578 #define __STDC_WANT_LIB_EXT1__ 1
29580 void abort_handler_s(
29581 const char * restrict msg,
29582 void * restrict ptr,
29583 errno_t error);
29584 </pre>
29587 A pointer to the abort_handler_s function shall be a suitable argument to the
29588 set_constraint_handler_s function.
29590 The abort_handler_s function writes a message on the standard error stream in an
29591 implementation-defined format. The message shall include the string pointed to by msg.
29592 The abort_handler_s function then calls the abort function.<sup><a href="#note393"><b>393)</b></a></sup>
29595 The abort_handler_s function does not return to its caller.
29600 <!--page 620 -->
29603 <p><small><a name="note393" href="#note393">393)</a> Many implementations invoke a debugger when the abort function is called.
29604 </small>
29609 <pre>
29610 #define __STDC_WANT_LIB_EXT1__ 1
29612 void ignore_handler_s(
29613 const char * restrict msg,
29614 void * restrict ptr,
29615 errno_t error);
29616 </pre>
29619 A pointer to the ignore_handler_s function shall be a suitable argument to the
29620 set_constraint_handler_s function.
29622 The ignore_handler_s function simply returns to its caller.<sup><a href="#note394"><b>394)</b></a></sup>
29625 The ignore_handler_s function returns no value.
29628 <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
29629 which a runtime-constraint violation occurs will return to its caller. The caller can determine whether
29630 a runtime-constraint violation occurred based on the library function's specification (usually, the
29631 library function returns a nonzero errno_t).
29632 </small>
29639 <pre>
29640 #define __STDC_WANT_LIB_EXT1__ 1
29642 errno_t getenv_s(size_t * restrict len,
29643 char * restrict value, rsize_t maxsize,
29644 const char * restrict name);
29645 </pre>
29646 Runtime-constraints
29648 name shall not be a null pointer. maxsize shall neither equal zero nor be greater than
29649 RSIZE_MAX. If maxsize is not equal to zero, then value shall not be a null pointer.
29651 If there is a runtime-constraint violation, the integer pointed to by len is set to 0 (if len
29652 is not null), and the environment list is not searched.
29655 The getenv_s function searches an environment list, provided by the host environment,
29656 for a string that matches the string pointed to by name.
29659 <!--page 621 -->
29661 If that name is found then getenv_s performs the following actions. If len is not a
29662 null pointer, the length of the string associated with the matched list member is stored in
29663 the integer pointed to by len. If the length of the associated string is less than maxsize,
29664 then the associated string is copied to the array pointed to by value.
29666 If that name is not found then getenv_s performs the following actions. If len is not
29667 a null pointer, zero is stored in the integer pointed to by len. If maxsize is greater than
29668 zero, then value[0] is set to the null character.
29670 The set of environment names and the method for altering the environment list are
29671 implementation-defined.
29674 The getenv_s function returns zero if the specified name is found and the associated
29675 string was successfully stored in value. Otherwise, a nonzero value is returned.
29679 These utilities make use of a comparison function to search or sort arrays of unspecified
29680 type. Where an argument declared as size_t nmemb specifies the length of the array
29681 for a function, if nmemb has the value zero on a call to that function, then the comparison
29682 function is not called, a search finds no matching element, sorting performs no
29683 rearrangement, and the pointer to the array may be null.
29685 The implementation shall ensure that the second argument of the comparison function
29686 (when called from bsearch_s), or both arguments (when called from qsort_s), are
29687 pointers to elements of the array.<sup><a href="#note395"><b>395)</b></a></sup> The first argument when called from bsearch_s
29688 shall equal key.
29690 The comparison function shall not alter the contents of either the array or search key. The
29691 implementation may reorder elements of the array between calls to the comparison
29692 function, but shall not otherwise alter the contents of any individual element.
29694 When the same objects (consisting of size bytes, irrespective of their current positions
29695 in the array) are passed more than once to the comparison function, the results shall be
29696 consistent with one another. That is, for qsort_s they shall define a total ordering on
29697 the array, and for bsearch_s the same object shall always compare the same way with
29698 the key.
29703 <!--page 622 -->
29705 A sequence point occurs immediately before and immediately after each call to the
29706 comparison function, and also between any call to the comparison function and any
29707 movement of the objects passed as arguments to that call.
29710 <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:
29712 <pre>
29713 ((char *)p - (char *)base) % size == 0
29714 (char *)p >= (char *)base
29715 (char *)p < (char *)base + nmemb * size
29716 </pre>
29717 </small>
29722 <pre>
29723 #define __STDC_WANT_LIB_EXT1__ 1
29725 void *bsearch_s(const void *key, const void *base,
29726 rsize_t nmemb, rsize_t size,
29727 int (*compar)(const void *k, const void *y,
29728 void *context),
29729 void *context);
29730 </pre>
29731 Runtime-constraints
29733 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
29734 zero, then none of key, base, or compar shall be a null pointer.
29736 If there is a runtime-constraint violation, the bsearch_s function does not search the
29737 array.
29740 The bsearch_s function searches an array of nmemb objects, the initial element of
29741 which is pointed to by base, for an element that matches the object pointed to by key.
29742 The size of each element of the array is specified by size.
29744 The comparison function pointed to by compar is called with three arguments. The first
29745 two point to the key object and to an array element, in that order. The function shall
29746 return an integer less than, equal to, or greater than zero if the key object is considered,
29747 respectively, to be less than, to match, or to be greater than the array element. The array
29748 shall consist of: all the elements that compare less than, all the elements that compare
29749 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>
29750 The third argument to the comparison function is the context argument passed to
29751 bsearch_s. The sole use of context by bsearch_s is to pass it to the comparison
29757 <!--page 623 -->
29760 The bsearch_s function returns a pointer to a matching element of the array, or a null
29761 pointer if no match is found or there is a runtime-constraint violation. If two elements
29762 compare as equal, which element is matched is unspecified.
29765 <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.
29766 </small>
29767 <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
29768 example, it might specify a collating sequence used by the comparison function.
29769 </small>
29774 <pre>
29775 #define __STDC_WANT_LIB_EXT1__ 1
29777 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
29778 int (*compar)(const void *x, const void *y,
29779 void *context),
29780 void *context);
29781 </pre>
29782 Runtime-constraints
29784 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
29785 zero, then neither base nor compar shall be a null pointer.
29787 If there is a runtime-constraint violation, the qsort_s function does not sort the array.
29790 The qsort_s function sorts an array of nmemb objects, the initial element of which is
29791 pointed to by base. The size of each object is specified by size.
29793 The contents of the array are sorted into ascending order according to a comparison
29794 function pointed to by compar, which is called with three arguments. The first two
29795 point to the objects being compared. The function shall return an integer less than, equal
29796 to, or greater than zero if the first argument is considered to be respectively less than,
29797 equal to, or greater than the second. The third argument to the comparison function is the
29798 context argument passed to qsort_s. The sole use of context by qsort_s is to
29801 If two elements compare as equal, their relative order in the resulting sorted array is
29802 unspecified.
29805 The qsort_s function returns zero if there was no runtime-constraint violation.
29806 Otherwise, a nonzero value is returned.
29811 <!--page 624 -->
29814 <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
29815 example, it might specify a collating sequence used by the comparison function.
29816 </small>
29818 <h5><a name="K.3.6.4" href="#K.3.6.4">K.3.6.4 Multibyte/wide character conversion functions</a></h5>
29820 The behavior of the multibyte character functions is affected by the LC_CTYPE category
29821 of the current locale. For a state-dependent encoding, each function is placed into its
29822 initial conversion state by a call for which its character pointer argument, s, is a null
29823 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
29824 state of the function to be altered as necessary. A call with s as a null pointer causes
29825 these functions to set the int pointed to by their status argument to a nonzero value if
29826 encodings have state dependency, and zero otherwise.<sup><a href="#note399"><b>399)</b></a></sup> Changing the LC_CTYPE
29827 category causes the conversion state of these functions to be indeterminate.
29830 <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
29831 character codes, but are grouped with an adjacent multibyte character.
29832 </small>
29837 <pre>
29838 #define __STDC_WANT_LIB_EXT1__ 1
29840 errno_t wctomb_s(int * restrict status,
29841 char * restrict s,
29842 rsize_t smax,
29843 wchar_t wc);
29844 </pre>
29845 Runtime-constraints
29847 Let n denote the number of bytes needed to represent the multibyte character
29848 corresponding to the wide character given by wc (including any shift sequences).
29850 If s is not a null pointer, then smax shall not be less than n, and smax shall not be
29851 greater than RSIZE_MAX. If s is a null pointer, then smax shall equal zero.
29853 If there is a runtime-constraint violation, wctomb_s does not modify the int pointed to
29854 by status, and if s is not a null pointer, no more than smax elements in the array
29855 pointed to by s will be accessed.
29858 The wctomb_s function determines n and stores the multibyte character representation
29859 of wc in the array whose first element is pointed to by s (if s is not a null pointer). The
29860 number of characters stored never exceeds MB_CUR_MAX or smax. If wc is a null wide
29861 character, a null byte is stored, preceded by any shift sequence needed to restore the
29862 initial shift state, and the function is left in the initial conversion state.
29864 The implementation shall behave as if no library function calls the wctomb_s function.
29869 <!--page 625 -->
29871 If s is a null pointer, the wctomb_s function stores into the int pointed to by status a
29872 nonzero or zero value, if multibyte character encodings, respectively, do or do not have
29873 state-dependent encodings.
29875 If s is not a null pointer, the wctomb_s function stores into the int pointed to by
29876 status either n or -1 if wc, respectively, does or does not correspond to a valid
29877 multibyte character.
29879 In no case will the int pointed to by status be set to a value greater than the
29880 MB_CUR_MAX macro.
29883 The wctomb_s function returns zero if successful, and a nonzero value if there was a
29884 runtime-constraint violation or wc did not correspond to a valid multibyte character.
29886 <h5><a name="K.3.6.5" href="#K.3.6.5">K.3.6.5 Multibyte/wide string conversion functions</a></h5>
29888 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
29889 the current locale.
29894 <pre>
29896 errno_t mbstowcs_s(size_t * restrict retval,
29897 wchar_t * restrict dst, rsize_t dstmax,
29898 const char * restrict src, rsize_t len);
29899 </pre>
29900 Runtime-constraints
29902 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
29903 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
29904 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
29905 zero. If dst is not a null pointer and len is not less than dstmax, then a null character
29906 shall occur within the first dstmax multibyte characters of the array pointed to by src.
29908 If there is a runtime-constraint violation, then mbstowcs_s does the following. If
29909 retval is not a null pointer, then mbstowcs_s sets *retval to (size_t)(-1). If
29910 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
29911 then mbstowcs_s sets dst[0] to the null wide character.
29914 The mbstowcs_s function converts a sequence of multibyte characters that begins in
29915 the initial shift state from the array pointed to by src into a sequence of corresponding
29916 wide characters. If dst is not a null pointer, the converted characters are stored into the
29917 array pointed to by dst. Conversion continues up to and including a terminating null
29918 character, which is also stored. Conversion stops earlier in two cases: when a sequence of
29919 <!--page 626 -->
29920 bytes is encountered that does not form a valid multibyte character, or (if dst is not a
29921 null pointer) when len wide characters have been stored into the array pointed to by
29922 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
29923 pointed to by dst, then dst[len] is set to the null wide character. Each conversion
29924 takes place as if by a call to the mbrtowc function.
29926 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
29927 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
29928 the mbstowcs_s function stores the value (size_t)(-1) into *retval.
29929 Otherwise, the mbstowcs_s function stores into *retval the number of multibyte
29930 characters successfully converted, not including the terminating null character (if any).
29932 All elements following the terminating null wide character (if any) written by
29933 mbstowcs_s in the array of dstmax wide characters pointed to by dst take
29936 If copying takes place between objects that overlap, the objects take on unspecified
29937 values.
29940 The mbstowcs_s function returns zero if no runtime-constraint violation and no
29941 encoding error occurred. Otherwise, a nonzero value is returned.
29944 <p><small><a name="note400" href="#note400">400)</a> Thus, the value of len is ignored if dst is a null pointer.
29945 </small>
29946 <p><small><a name="note401" href="#note401">401)</a> This allows an implementation to attempt converting the multibyte string before discovering a
29947 terminating null character did not occur where required.
29948 </small>
29953 <pre>
29955 errno_t wcstombs_s(size_t * restrict retval,
29956 char * restrict dst, rsize_t dstmax,
29957 const wchar_t * restrict src, rsize_t len);
29958 </pre>
29959 Runtime-constraints
29961 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
29962 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
29963 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
29964 zero. If dst is not a null pointer and len is not less than dstmax, then the conversion
29965 shall have been stopped (see below) because a terminating null wide character was
29966 reached or because an encoding error occurred.
29971 <!--page 627 -->
29973 If there is a runtime-constraint violation, then wcstombs_s does the following. If
29974 retval is not a null pointer, then wcstombs_s sets *retval to (size_t)(-1). If
29975 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
29976 then wcstombs_s sets dst[0] to the null character.
29979 The wcstombs_s function converts a sequence of wide characters from the array
29980 pointed to by src into a sequence of corresponding multibyte characters that begins in
29981 the initial shift state. If dst is not a null pointer, the converted characters are then stored
29982 into the array pointed to by dst. Conversion continues up to and including a terminating
29983 null wide character, which is also stored. Conversion stops earlier in two cases:
29984 <ul>
29985 <li> when a wide character is reached that does not correspond to a valid multibyte
29986 character;
29987 <li> (if dst is not a null pointer) when the next multibyte character would exceed the
29988 limit of n total bytes to be stored into the array pointed to by dst. If the wide
29989 character being converted is the null wide character, then n is the lesser of len or
29990 dstmax. Otherwise, n is the lesser of len or dstmax-1.
29991 </ul>
29992 If the conversion stops without converting a null wide character and dst is not a null
29993 pointer, then a null character is stored into the array pointed to by dst immediately
29994 following any multibyte characters already stored. Each conversion takes place as if by a
29997 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
29998 wide character that does not correspond to a valid multibyte character, an encoding error
29999 occurs: the wcstombs_s function stores the value (size_t)(-1) into *retval.
30000 Otherwise, the wcstombs_s function stores into *retval the number of bytes in the
30001 resulting multibyte character sequence, not including the terminating null character (if
30002 any).
30004 All elements following the terminating null character (if any) written by wcstombs_s
30005 in the array of dstmax elements pointed to by dst take unspecified values when
30008 If copying takes place between objects that overlap, the objects take on unspecified
30009 values.
30012 <!--page 628 -->
30015 The wcstombs_s function returns zero if no runtime-constraint violation and no
30016 encoding error occurred. Otherwise, a nonzero value is returned.
30019 <p><small><a name="note402" href="#note402">402)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
30020 include those necessary to reach the initial shift state immediately before the null byte. However, if
30021 the conversion stops before a terminating null wide character has been reached, the result will be null
30022 terminated, but might not end in the initial shift state.
30023 </small>
30024 <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
30025 runtime-constraint violation.
30026 </small>
30032 The types are
30033 <pre>
30034 errno_t
30035 </pre>
30036 which is type int; and
30037 <pre>
30038 rsize_t
30039 </pre>
30040 which is the type size_t.
30047 <pre>
30048 #define __STDC_WANT_LIB_EXT1__ 1
30050 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
30051 const void * restrict s2, rsize_t n);
30052 </pre>
30053 Runtime-constraints
30055 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
30056 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
30057 objects that overlap.
30059 If there is a runtime-constraint violation, the memcpy_s function stores zeros in the first
30060 s1max characters of the object pointed to by s1 if s1 is not a null pointer and s1max is
30061 not greater than RSIZE_MAX.
30064 The memcpy_s function copies n characters from the object pointed to by s2 into the
30065 object pointed to by s1.
30068 The memcpy_s function returns zero if there was no runtime-constraint violation.
30069 Otherwise, a nonzero value is returned.
30070 <!--page 629 -->
30075 <pre>
30076 #define __STDC_WANT_LIB_EXT1__ 1
30078 errno_t memmove_s(void *s1, rsize_t s1max,
30079 const void *s2, rsize_t n);
30080 </pre>
30081 Runtime-constraints
30083 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
30084 RSIZE_MAX. n shall not be greater than s1max.
30086 If there is a runtime-constraint violation, the memmove_s function stores zeros in the
30087 first s1max characters of the object pointed to by s1 if s1 is not a null pointer and
30088 s1max is not greater than RSIZE_MAX.
30091 The memmove_s function copies n characters from the object pointed to by s2 into the
30092 object pointed to by s1. This copying takes place as if the n characters from the object
30093 pointed to by s2 are first copied into a temporary array of n characters that does not
30094 overlap the objects pointed to by s1 or s2, and then the n characters from the temporary
30095 array are copied into the object pointed to by s1.
30098 The memmove_s function returns zero if there was no runtime-constraint violation.
30099 Otherwise, a nonzero value is returned.
30104 <pre>
30105 #define __STDC_WANT_LIB_EXT1__ 1
30107 errno_t strcpy_s(char * restrict s1,
30108 rsize_t s1max,
30109 const char * restrict s2);
30110 </pre>
30111 Runtime-constraints
30113 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
30114 s1max shall not equal zero. s1max shall be greater than strnlen_s(s2, s1max).
30115 Copying shall not take place between objects that overlap.
30117 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
30118 greater than zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the
30119 null character.
30120 <!--page 630 -->
30123 The strcpy_s function copies the string pointed to by s2 (including the terminating
30124 null character) into the array pointed to by s1.
30126 All elements following the terminating null character (if any) written by strcpy_s in
30127 the array of s1max characters pointed to by s1 take unspecified values when
30131 The strcpy_s function returns zero<sup><a href="#note405"><b>405)</b></a></sup> if there was no runtime-constraint violation.
30132 Otherwise, a nonzero value is returned.
30135 <p><small><a name="note404" href="#note404">404)</a> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
30136 any of those characters are null. Such an approach might write a character to every element of s1
30137 before discovering that the first element should be set to the null character.
30138 </small>
30139 <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
30140 within the array pointed to by s1 and that the result in s1 is null terminated.
30141 </small>
30146 <pre>
30147 #define __STDC_WANT_LIB_EXT1__ 1
30149 errno_t strncpy_s(char * restrict s1,
30150 rsize_t s1max,
30151 const char * restrict s2,
30152 rsize_t n);
30153 </pre>
30154 Runtime-constraints
30156 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
30157 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
30158 shall be greater than strnlen_s(s2, s1max). Copying shall not take place between
30159 objects that overlap.
30161 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
30162 greater than zero and not greater than RSIZE_MAX, then strncpy_s sets s1[0] to the
30163 null character.
30166 The strncpy_s function copies not more than n successive characters (characters that
30167 follow a null character are not copied) from the array pointed to by s2 to the array
30168 pointed to by s1. If no null character was copied from s2, then s1[n] is set to a null
30169 character.
30172 <!--page 631 -->
30174 All elements following the terminating null character (if any) written by strncpy_s in
30175 the array of s1max characters pointed to by s1 take unspecified values when
30179 The strncpy_s function returns zero<sup><a href="#note407"><b>407)</b></a></sup> if there was no runtime-constraint violation.
30180 Otherwise, a nonzero value is returned.
30182 EXAMPLE 1 The strncpy_s function can be used to copy a string without the danger that the result
30183 will not be null terminated or that characters will be written past the end of the destination array.
30184 <pre>
30185 #define __STDC_WANT_LIB_EXT1__ 1
30187 /* ... */
30189 char src2[7] = {'g', 'o', 'o', 'd', 'b', 'y', 'e'};
30191 int r1, r2, r3;
30195 </pre>
30196 The first call will assign to r1 the value zero and to dst1 the sequence hello\0.
30197 The second call will assign to r2 a nonzero value and to dst2 the sequence \0.
30198 The third call will assign to r3 the value zero and to dst3 the sequence good\0.
30202 <p><small><a name="note406" href="#note406">406)</a> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
30203 any of those characters are null. Such an approach might write a character to every element of s1
30204 before discovering that the first element should be set to the null character.
30205 </small>
30206 <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
30207 within the array pointed to by s1 and that the result in s1 is null terminated.
30208 </small>
30215 <pre>
30216 #define __STDC_WANT_LIB_EXT1__ 1
30218 errno_t strcat_s(char * restrict s1,
30219 rsize_t s1max,
30220 const char * restrict s2);
30221 </pre>
30222 Runtime-constraints
30224 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
30225 strcat_s.
30230 <!--page 632 -->
30232 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
30233 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note408"><b>408)</b></a></sup> m shall be greater than
30234 strnlen_s(s2, m). Copying shall not take place between objects that overlap.
30236 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
30237 greater than zero and not greater than RSIZE_MAX, then strcat_s sets s1[0] to the
30238 null character.
30241 The strcat_s function appends a copy of the string pointed to by s2 (including the
30242 terminating null character) to the end of the string pointed to by s1. The initial character
30243 from s2 overwrites the null character at the end of s1.
30245 All elements following the terminating null character (if any) written by strcat_s in
30246 the array of s1max characters pointed to by s1 take unspecified values when
30250 The strcat_s function returns zero<sup><a href="#note410"><b>410)</b></a></sup> if there was no runtime-constraint violation.
30251 Otherwise, a nonzero value is returned.
30254 <p><small><a name="note408" href="#note408">408)</a> Zero means that s1 was not null terminated upon entry to strcat_s.
30255 </small>
30256 <p><small><a name="note409" href="#note409">409)</a> This allows an implementation to append characters from s2 to s1 while simultaneously checking if
30257 any of those characters are null. Such an approach might write a character to every element of s1
30258 before discovering that the first element should be set to the null character.
30259 </small>
30260 <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
30261 appended to the string pointed to by s1 and that the result in s1 is null terminated.
30262 </small>
30267 <pre>
30268 #define __STDC_WANT_LIB_EXT1__ 1
30270 errno_t strncat_s(char * restrict s1,
30271 rsize_t s1max,
30272 const char * restrict s2,
30273 rsize_t n);
30274 </pre>
30275 Runtime-constraints
30277 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
30278 strncat_s.
30280 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
30281 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
30284 <!--page 633 -->
30285 than m, then m shall be greater than strnlen_s(s2, m). Copying shall not take
30286 place between objects that overlap.
30288 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
30289 greater than zero and not greater than RSIZE_MAX, then strncat_s sets s1[0] to the
30290 null character.
30293 The strncat_s function appends not more than n successive characters (characters
30294 that follow a null character are not copied) from the array pointed to by s2 to the end of
30295 the string pointed to by s1. The initial character from s2 overwrites the null character at
30296 the end of s1. If no null character was copied from s2, then s1[s1max-m+n] is set to
30297 a null character.
30299 All elements following the terminating null character (if any) written by strncat_s in
30300 the array of s1max characters pointed to by s1 take unspecified values when
30304 The strncat_s function returns zero<sup><a href="#note413"><b>413)</b></a></sup> if there was no runtime-constraint violation.
30305 Otherwise, a nonzero value is returned.
30307 EXAMPLE 1 The strncat_s function can be used to copy a string without the danger that the result
30308 will not be null terminated or that characters will be written past the end of the destination array.
30309 <pre>
30310 #define __STDC_WANT_LIB_EXT1__ 1
30312 /* ... */
30318 int r1, r2, r3, r4;
30323 </pre>
30324 After the first call r1 will have the value zero and s1 will contain the sequence goodbye\0.
30328 <!--page 634 -->
30329 After the second call r2 will have the value zero and s2 will contain the sequence hello\0.
30330 After the third call r3 will have a nonzero value and s3 will contain the sequence \0.
30331 After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0.
30335 <p><small><a name="note411" href="#note411">411)</a> Zero means that s1 was not null terminated upon entry to strncat_s.
30336 </small>
30337 <p><small><a name="note412" href="#note412">412)</a> This allows an implementation to append characters from s2 to s1 while simultaneously checking if
30338 any of those characters are null. Such an approach might write a character to every element of s1
30339 before discovering that the first element should be set to the null character.
30340 </small>
30341 <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
30342 appended to the string pointed to by s1 and that the result in s1 is null terminated.
30343 </small>
30350 <pre>
30351 #define __STDC_WANT_LIB_EXT1__ 1
30353 char *strtok_s(char * restrict s1,
30354 rsize_t * restrict s1max,
30355 const char * restrict s2,
30356 char ** restrict ptr);
30357 </pre>
30358 Runtime-constraints
30360 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
30361 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
30362 The end of the token found shall occur within the first *s1max characters of s1 for the
30363 first call, and shall occur within the first *s1max characters of where searching resumes
30364 on subsequent calls.
30366 If there is a runtime-constraint violation, the strtok_s function does not indirect
30367 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
30370 A sequence of calls to the strtok_s function breaks the string pointed to by s1 into a
30371 sequence of tokens, each of which is delimited by a character from the string pointed to
30372 by s2. The fourth argument points to a caller-provided char pointer into which the
30373 strtok_s function stores information necessary for it to continue scanning the same
30374 string.
30376 The first call in a sequence has a non-null first argument and s1max points to an object
30377 whose value is the number of elements in the character array pointed to by the first
30378 argument. The first call stores an initial value in the object pointed to by ptr and
30379 updates the value pointed to by s1max to reflect the number of elements that remain in
30380 relation to ptr. Subsequent calls in the sequence have a null first argument and the
30381 objects pointed to by s1max and ptr are required to have the values stored by the
30382 previous call in the sequence, which are then updated. The separator string pointed to by
30383 s2 may be different from call to call.
30385 The first call in the sequence searches the string pointed to by s1 for the first character
30386 that is not contained in the current separator string pointed to by s2. If no such character
30387 is found, then there are no tokens in the string pointed to by s1 and the strtok_s
30388 function returns a null pointer. If such a character is found, it is the start of the first token.
30389 <!--page 635 -->
30391 The strtok_s function then searches from there for the first character in s1 that is
30392 contained in the current separator string. If no such character is found, the current token
30393 extends to the end of the string pointed to by s1, and subsequent searches in the same
30394 string for a token return a null pointer. If such a character is found, it is overwritten by a
30395 null character, which terminates the current token.
30397 In all cases, the strtok_s function stores sufficient information in the pointer pointed
30398 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
30399 value for ptr, shall start searching just past the element overwritten by a null character
30400 (if any).
30403 The strtok_s function returns a pointer to the first character of a token, or a null
30404 pointer if there is no token or there is a runtime-constraint violation.
30406 EXAMPLE
30407 <pre>
30408 #define __STDC_WANT_LIB_EXT1__ 1
30410 static char str1[] = "?a???b,,,#c";
30411 static char str2[] = "\t \t";
30412 char *t, *ptr1, *ptr2;
30413 rsize_t max1 = sizeof(str1);
30414 rsize_t max2 = sizeof(str2);
30420 </pre>
30428 <pre>
30429 #define __STDC_WANT_LIB_EXT1__ 1
30431 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
30432 </pre>
30433 Runtime-constraints
30435 s shall not be a null pointer. Neither smax nor n shall be greater than RSIZE_MAX. n
30436 shall not be greater than smax.
30438 If there is a runtime-constraint violation, then if s is not a null pointer and smax is not
30439 greater than RSIZE_MAX, the memset_s function stores the value of c (converted to an
30440 unsigned char) into each of the first smax characters of the object pointed to by s.
30441 <!--page 636 -->
30444 The memset_s function copies the value of c (converted to an unsigned char) into
30445 each of the first n characters of the object pointed to by s. Unlike memset, any call to
30446 the memset_s function shall be evaluated strictly according to the rules of the abstract
30447 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
30448 assume that the memory indicated by s and n may be accessible in the future and thus
30449 must contain the values indicated by c.
30452 The memset_s function returns zero if there was no runtime-constraint violation.
30453 Otherwise, a nonzero value is returned.
30458 <pre>
30459 #define __STDC_WANT_LIB_EXT1__ 1
30461 errno_t strerror_s(char *s, rsize_t maxsize,
30462 errno_t errnum);
30463 </pre>
30464 Runtime-constraints
30466 s shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX.
30467 maxsize shall not equal zero.
30469 If there is a runtime-constraint violation, then the array (if any) pointed to by s is not
30470 modified.
30473 The strerror_s function maps the number in errnum to a locale-specific message
30474 string. Typically, the values for errnum come from errno, but strerror_s shall
30475 map any value of type int to a message.
30477 If the length of the desired string is less than maxsize, then the string is copied to the
30478 array pointed to by s.
30480 Otherwise, if maxsize is greater than zero, then maxsize-1 characters are copied
30481 from the string to the array pointed to by s and then s[maxsize-1] is set to the null
30486 The strerror_s function returns zero if the length of the desired string was less than
30487 maxsize and there was no runtime-constraint violation. Otherwise, the strerror_s
30488 function returns a nonzero value.
30489 <!--page 637 -->
30494 <pre>
30495 #define __STDC_WANT_LIB_EXT1__ 1
30497 size_t strerrorlen_s(errno_t errnum);
30498 </pre>
30501 The strerrorlen_s function calculates the length of the (untruncated) locale-specific
30502 message string that the strerror_s function maps to errnum.
30505 The strerrorlen_s function returns the number of characters (not including the null
30506 character) in the full message string.
30511 <pre>
30512 #define __STDC_WANT_LIB_EXT1__ 1
30514 size_t strnlen_s(const char *s, size_t maxsize);
30515 </pre>
30518 The strnlen_s function computes the length of the string pointed to by s.
30521 If s is a null pointer,<sup><a href="#note414"><b>414)</b></a></sup> then the strnlen_s function returns zero.
30523 Otherwise, the strnlen_s function returns the number of characters that precede the
30524 terminating null character. If there is no null character in the first maxsize characters of
30525 s then strnlen_s returns maxsize. At most the first maxsize characters of s shall
30526 be accessed by strnlen_s.
30531 <!--page 638 -->
30534 <p><small><a name="note414" href="#note414">414)</a> Note that the strnlen_s function has no runtime-constraints. This lack of runtime-constraints
30535 along with the values returned for a null pointer or an unterminated string argument make
30536 strnlen_s useful in algorithms that gracefully handle such exceptional data.
30537 </small>
30543 The types are
30544 <pre>
30545 errno_t
30546 </pre>
30547 which is type int; and
30548 <pre>
30549 rsize_t
30550 </pre>
30551 which is the type size_t.
30555 A broken-down time is normalized if the values of the members of the tm structure are in
30559 <p><small><a name="note415" href="#note415">415)</a> The normal ranges are defined in <a href="#7.26.1">7.26.1</a>.
30560 </small>
30564 Like the strftime function, the asctime_s and ctime_s functions do not return a
30565 pointer to a static object, and other library functions are permitted to call them.
30570 <pre>
30571 #define __STDC_WANT_LIB_EXT1__ 1
30573 errno_t asctime_s(char *s, rsize_t maxsize,
30574 const struct tm *timeptr);
30575 </pre>
30576 Runtime-constraints
30578 Neither s nor timeptr shall be a null pointer. maxsize shall not be less than 26 and
30579 shall not be greater than RSIZE_MAX. The broken-down time pointed to by timeptr
30580 shall be normalized. The calendar year represented by the broken-down time pointed to
30581 by timeptr shall not be less than calendar year 0 and shall not be greater than calendar
30582 year 9999.
30584 If there is a runtime-constraint violation, there is no attempt to convert the time, and
30585 s[0] is set to a null character if s is not a null pointer and maxsize is not zero and is
30586 not greater than RSIZE_MAX.
30589 The asctime_s function converts the normalized broken-down time in the structure
30590 pointed to by timeptr into a 26 character (including the null character) string in the
30593 <!--page 639 -->
30594 form
30595 <pre>
30597 </pre>
30598 The fields making up this string are (in order):
30599 <ol>
30601 following three character weekday names: Sun, Mon, Tue, Wed, Thu, Fri, and Sat.
30602 <li> The character space.
30604 three character month names: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct,
30605 Nov, and Dec.
30606 <li> The character space.
30608 "%2d".
30609 <li> The character space.
30611 "%.2d".
30612 <li> The character colon.
30614 "%.2d".
30615 <li> The character colon.
30617 "%.2d".
30618 <li> The character space.
30620 format "%4d".
30621 <li> The character new line.
30622 <li> The null character.
30623 </ol>
30625 The strftime function allows more flexible formatting and supports locale-specific
30626 behavior. If you do not require the exact form of the result string produced by the
30627 asctime_s function, consider using the strftime function instead.
30630 The asctime_s function returns zero if the time was successfully converted and stored
30631 into the array pointed to by s. Otherwise, it returns a nonzero value.
30632 <!--page 640 -->
30637 <pre>
30638 #define __STDC_WANT_LIB_EXT1__ 1
30640 errno_t ctime_s(char *s, rsize_t maxsize,
30641 const time_t *timer);
30642 </pre>
30643 Runtime-constraints
30645 Neither s nor timer shall be a null pointer. maxsize shall not be less than 26 and
30646 shall not be greater than RSIZE_MAX.
30648 If there is a runtime-constraint violation, s[0] is set to a null character if s is not a null
30649 pointer and maxsize is not equal zero and is not greater than RSIZE_MAX.
30652 The ctime_s function converts the calendar time pointed to by timer to local time in
30653 the form of a string. It is equivalent to
30654 <pre>
30655 asctime_s(s, maxsize, localtime_s(timer))
30656 </pre>
30658 The strftime function allows more flexible formatting and supports locale-specific
30659 behavior. If you do not require the exact form of the result string produced by the
30660 ctime_s function, consider using the strftime function instead.
30663 The ctime_s function returns zero if the time was successfully converted and stored
30664 into the array pointed to by s. Otherwise, it returns a nonzero value.
30669 <pre>
30670 #define __STDC_WANT_LIB_EXT1__ 1
30672 struct tm *gmtime_s(const time_t * restrict timer,
30673 struct tm * restrict result);
30674 </pre>
30675 Runtime-constraints
30677 Neither timer nor result shall be a null pointer.
30679 If there is a runtime-constraint violation, there is no attempt to convert the time.
30682 The gmtime_s function converts the calendar time pointed to by timer into a broken-
30683 down time, expressed as UTC. The broken-down time is stored in the structure pointed
30684 <!--page 641 -->
30685 to by result.
30688 The gmtime_s function returns result, or a null pointer if the specified time cannot
30689 be converted to UTC or there is a runtime-constraint violation.
30694 <pre>
30695 #define __STDC_WANT_LIB_EXT1__ 1
30697 struct tm *localtime_s(const time_t * restrict timer,
30698 struct tm * restrict result);
30699 </pre>
30700 Runtime-constraints
30702 Neither timer nor result shall be a null pointer.
30704 If there is a runtime-constraint violation, there is no attempt to convert the time.
30707 The localtime_s function converts the calendar time pointed to by timer into a
30708 broken-down time, expressed as local time. The broken-down time is stored in the
30709 structure pointed to by result.
30712 The localtime_s function returns result, or a null pointer if the specified time
30713 cannot be converted to local time or there is a runtime-constraint violation.
30715 <h4><a name="K.3.9" href="#K.3.9">K.3.9 Extended multibyte and wide character utilities <wchar.h></a></h4>
30719 The types are
30720 <pre>
30721 errno_t
30722 </pre>
30723 which is type int; and
30724 <pre>
30725 rsize_t
30726 </pre>
30727 which is the type size_t.
30729 Unless explicitly stated otherwise, if the execution of a function described in this
30730 subclause causes copying to take place between objects that overlap, the objects take on
30731 unspecified values.
30732 <!--page 642 -->
30734 <h5><a name="K.3.9.1" href="#K.3.9.1">K.3.9.1 Formatted wide character input/output functions</a></h5>
30739 <pre>
30740 #define __STDC_WANT_LIB_EXT1__ 1
30742 int fwprintf_s(FILE * restrict stream,
30743 const wchar_t * restrict format, ...);
30744 </pre>
30745 Runtime-constraints
30747 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note416"><b>416)</b></a></sup> (modified or
30748 not by flags, field width, or precision) shall not appear in the wide string pointed to by
30749 format. Any argument to fwprintf_s corresponding to a %s specifier shall not be a
30750 null pointer.
30752 If there is a runtime-constraint violation, the fwprintf_s function does not attempt to
30753 produce further output, and it is unspecified to what extent fwprintf_s produced
30754 output before discovering the runtime-constraint violation.
30757 The fwprintf_s function is equivalent to the fwprintf function except for the
30758 explicit runtime-constraints listed above.
30761 The fwprintf_s function returns the number of wide characters transmitted, or a
30762 negative value if an output error, encoding error, or runtime-constraint violation occurred.
30765 <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
30766 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
30767 example, if the entire format string was L"%%n".
30768 </small>
30773 <pre>
30774 #define __STDC_WANT_LIB_EXT1__ 1
30777 int fwscanf_s(FILE * restrict stream,
30778 const wchar_t * restrict format, ...);
30779 </pre>
30780 Runtime-constraints
30782 Neither stream nor format shall be a null pointer. Any argument indirected though in
30783 order to store converted input shall not be a null pointer.
30786 <!--page 643 -->
30788 If there is a runtime-constraint violation, the fwscanf_s function does not attempt to
30789 perform further input, and it is unspecified to what extent fwscanf_s performed input
30790 before discovering the runtime-constraint violation.
30793 The fwscanf_s function is equivalent to fwscanf except that the c, s, and [
30794 conversion specifiers apply to a pair of arguments (unless assignment suppression is
30795 indicated by a *). The first of these arguments is the same as for fwscanf. That
30796 argument is immediately followed in the argument list by the second argument, which has
30797 type size_t and gives the number of elements in the array pointed to by the first
30798 argument of the pair. If the first argument points to a scalar object, it is considered to be
30801 A matching failure occurs if the number of elements in a receiving object is insufficient to
30802 hold the converted input (including any trailing null character).
30805 The fwscanf_s function returns the value of the macro EOF if an input failure occurs
30806 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30807 fwscanf_s function returns the number of input items assigned, which can be fewer
30808 than provided for, or even zero, in the event of an early matching failure.
30811 <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
30812 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
30813 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
30814 the format is not known at translation time. For example, an implementation may issue a diagnostic
30815 for each argument after format that has of type pointer to one of char, signed char,
30816 unsigned char, or void that is not followed by an argument of a type compatible with
30817 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
30818 using the hh length modifier, a length argument must follow the pointer argument. Another useful
30819 diagnostic could flag any non-pointer argument following format that did not have a type
30820 compatible with rsize_t.
30821 </small>
30826 <pre>
30827 #define __STDC_WANT_LIB_EXT1__ 1
30829 int snwprintf_s(wchar_t * restrict s,
30830 rsize_t n,
30831 const wchar_t * restrict format, ...);
30832 </pre>
30833 Runtime-constraints
30835 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30836 than RSIZE_MAX. The %n specifier<sup><a href="#note418"><b>418)</b></a></sup> (modified or not by flags, field width, or
30838 <!--page 644 -->
30839 precision) shall not appear in the wide string pointed to by format. Any argument to
30840 snwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
30841 error shall occur.
30843 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30844 than zero and less than RSIZE_MAX, then the snwprintf_s function sets s[0] to the
30845 null wide character.
30848 The snwprintf_s function is equivalent to the swprintf function except for the
30849 explicit runtime-constraints listed above.
30851 The snwprintf_s function, unlike swprintf_s, will truncate the result to fit within
30852 the array pointed to by s.
30855 The snwprintf_s function returns the number of wide characters that would have
30856 been written had n been sufficiently large, not counting the terminating wide null
30857 character, or a negative value if a runtime-constraint violation occurred. Thus, the null-
30858 terminated output has been completely written if and only if the returned value is
30859 nonnegative and less than n.
30862 <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
30863 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
30864 example, if the entire format string was L"%%n".
30865 </small>
30870 <pre>
30871 #define __STDC_WANT_LIB_EXT1__ 1
30873 int swprintf_s(wchar_t * restrict s, rsize_t n,
30874 const wchar_t * restrict format, ...);
30875 </pre>
30876 Runtime-constraints
30878 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
30879 than RSIZE_MAX. The number of wide characters (including the trailing null) required
30880 for the result to be written to the array pointed to by s shall not be greater than n. The %n
30881 specifier<sup><a href="#note419"><b>419)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
30882 wide string pointed to by format. Any argument to swprintf_s corresponding to a
30883 %s specifier shall not be a null pointer. No encoding error shall occur.
30886 <!--page 645 -->
30888 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
30889 than zero and less than RSIZE_MAX, then the swprintf_s function sets s[0] to the
30890 null wide character.
30893 The swprintf_s function is equivalent to the swprintf function except for the
30894 explicit runtime-constraints listed above.
30896 The swprintf_s function, unlike snwprintf_s, treats a result too big for the array
30897 pointed to by s as a runtime-constraint violation.
30900 If no runtime-constraint violation occurred, the swprintf_s function returns the
30901 number of wide characters written in the array, not counting the terminating null wide
30902 character. If an encoding error occurred or if n or more wide characters are requested to
30903 be written, swprintf_s returns a negative value. If any other runtime-constraint
30904 violation occurred, swprintf_s returns zero.
30907 <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
30908 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
30909 example, if the entire format string was L"%%n".
30910 </small>
30915 <pre>
30916 #define __STDC_WANT_LIB_EXT1__ 1
30918 int swscanf_s(const wchar_t * restrict s,
30919 const wchar_t * restrict format, ...);
30920 </pre>
30921 Runtime-constraints
30923 Neither s nor format shall be a null pointer. Any argument indirected though in order
30924 to store converted input shall not be a null pointer.
30926 If there is a runtime-constraint violation, the swscanf_s function does not attempt to
30927 perform further input, and it is unspecified to what extent swscanf_s performed input
30928 before discovering the runtime-constraint violation.
30931 The swscanf_s function is equivalent to fwscanf_s, except that the argument s
30932 specifies a wide string from which the input is to be obtained, rather than from a stream.
30933 Reaching the end of the wide string is equivalent to encountering end-of-file for the
30934 fwscanf_s function.
30937 The swscanf_s function returns the value of the macro EOF if an input failure occurs
30938 before any conversion or if there is a runtime-constraint violation. Otherwise, the
30939 swscanf_s function returns the number of input items assigned, which can be fewer
30940 than provided for, or even zero, in the event of an early matching failure.
30941 <!--page 646 -->
30946 <pre>
30947 #define __STDC_WANT_LIB_EXT1__ 1
30951 int vfwprintf_s(FILE * restrict stream,
30952 const wchar_t * restrict format,
30953 va_list arg);
30954 </pre>
30955 Runtime-constraints
30957 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note420"><b>420)</b></a></sup> (modified or
30958 not by flags, field width, or precision) shall not appear in the wide string pointed to by
30959 format. Any argument to vfwprintf_s corresponding to a %s specifier shall not be
30960 a null pointer.
30962 If there is a runtime-constraint violation, the vfwprintf_s function does not attempt
30963 to produce further output, and it is unspecified to what extent vfwprintf_s produced
30964 output before discovering the runtime-constraint violation.
30967 The vfwprintf_s function is equivalent to the vfwprintf function except for the
30968 explicit runtime-constraints listed above.
30971 The vfwprintf_s function returns the number of wide characters transmitted, or a
30972 negative value if an output error, encoding error, or runtime-constraint violation occurred.
30975 <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
30976 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
30977 example, if the entire format string was L"%%n".
30978 </small>
30983 <pre>
30984 #define __STDC_WANT_LIB_EXT1__ 1
30988 int vfwscanf_s(FILE * restrict stream,
30989 const wchar_t * restrict format, va_list arg);
30990 </pre>
30994 <!--page 647 -->
30995 Runtime-constraints
30997 Neither stream nor format shall be a null pointer. Any argument indirected though in
30998 order to store converted input shall not be a null pointer.
31000 If there is a runtime-constraint violation, the vfwscanf_s function does not attempt to
31001 perform further input, and it is unspecified to what extent vfwscanf_s performed input
31002 before discovering the runtime-constraint violation.
31005 The vfwscanf_s function is equivalent to fwscanf_s, with the variable argument
31006 list replaced by arg, which shall have been initialized by the va_start macro (and
31007 possibly subsequent va_arg calls). The vfwscanf_s function does not invoke the
31011 The vfwscanf_s function returns the value of the macro EOF if an input failure occurs
31012 before any conversion or if there is a runtime-constraint violation. Otherwise, the
31013 vfwscanf_s function returns the number of input items assigned, which can be fewer
31014 than provided for, or even zero, in the event of an early matching failure.
31017 <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
31018 value of arg after the return is indeterminate.
31019 </small>
31024 <pre>
31025 #define __STDC_WANT_LIB_EXT1__ 1
31028 int vsnwprintf_s(wchar_t * restrict s,
31029 rsize_t n,
31030 const wchar_t * restrict format,
31031 va_list arg);
31032 </pre>
31033 Runtime-constraints
31035 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
31036 than RSIZE_MAX. The %n specifier<sup><a href="#note422"><b>422)</b></a></sup> (modified or not by flags, field width, or
31037 precision) shall not appear in the wide string pointed to by format. Any argument to
31038 vsnwprintf_s corresponding to a %s specifier shall not be a null pointer. No
31039 encoding error shall occur.
31041 <!--page 648 -->
31043 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
31044 than zero and less than RSIZE_MAX, then the vsnwprintf_s function sets s[0] to
31045 the null wide character.
31048 The vsnwprintf_s function is equivalent to the vswprintf function except for the
31049 explicit runtime-constraints listed above.
31051 The vsnwprintf_s function, unlike vswprintf_s, will truncate the result to fit
31052 within the array pointed to by s.
31055 The vsnwprintf_s function returns the number of wide characters that would have
31056 been written had n been sufficiently large, not counting the terminating null character, or
31057 a negative value if a runtime-constraint violation occurred. Thus, the null-terminated
31058 output has been completely written if and only if the returned value is nonnegative and
31059 less than n.
31062 <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
31063 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
31064 example, if the entire format string was L"%%n".
31065 </small>
31070 <pre>
31071 #define __STDC_WANT_LIB_EXT1__ 1
31074 int vswprintf_s(wchar_t * restrict s,
31075 rsize_t n,
31076 const wchar_t * restrict format,
31077 va_list arg);
31078 </pre>
31079 Runtime-constraints
31081 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
31082 than RSIZE_MAX. The number of wide characters (including the trailing null) required
31083 for the result to be written to the array pointed to by s shall not be greater than n. The %n
31084 specifier<sup><a href="#note423"><b>423)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
31085 wide string pointed to by format. Any argument to vswprintf_s corresponding to a
31086 %s specifier shall not be a null pointer. No encoding error shall occur.
31088 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
31089 than zero and less than RSIZE_MAX, then the vswprintf_s function sets s[0] to the
31090 null wide character.
31092 <!--page 649 -->
31095 The vswprintf_s function is equivalent to the vswprintf function except for the
31096 explicit runtime-constraints listed above.
31098 The vswprintf_s function, unlike vsnwprintf_s, treats a result too big for the
31099 array pointed to by s as a runtime-constraint violation.
31102 If no runtime-constraint violation occurred, the vswprintf_s function returns the
31103 number of wide characters written in the array, not counting the terminating null wide
31104 character. If an encoding error occurred or if n or more wide characters are requested to
31105 be written, vswprintf_s returns a negative value. If any other runtime-constraint
31106 violation occurred, vswprintf_s returns zero.
31109 <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
31110 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
31111 example, if the entire format string was L"%%n".
31112 </small>
31117 <pre>
31118 #define __STDC_WANT_LIB_EXT1__ 1
31121 int vswscanf_s(const wchar_t * restrict s,
31122 const wchar_t * restrict format,
31123 va_list arg);
31124 </pre>
31125 Runtime-constraints
31127 Neither s nor format shall be a null pointer. Any argument indirected though in order
31128 to store converted input shall not be a null pointer.
31130 If there is a runtime-constraint violation, the vswscanf_s function does not attempt to
31131 perform further input, and it is unspecified to what extent vswscanf_s performed input
31132 before discovering the runtime-constraint violation.
31135 The vswscanf_s function is equivalent to swscanf_s, with the variable argument
31136 list replaced by arg, which shall have been initialized by the va_start macro (and
31137 possibly subsequent va_arg calls). The vswscanf_s function does not invoke the
31143 <!--page 650 -->
31146 The vswscanf_s function returns the value of the macro EOF if an input failure occurs
31147 before any conversion or if there is a runtime-constraint violation. Otherwise, the
31148 vswscanf_s function returns the number of input items assigned, which can be fewer
31149 than provided for, or even zero, in the event of an early matching failure.
31152 <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
31153 value of arg after the return is indeterminate.
31154 </small>
31159 <pre>
31160 #define __STDC_WANT_LIB_EXT1__ 1
31163 int vwprintf_s(const wchar_t * restrict format,
31164 va_list arg);
31165 </pre>
31166 Runtime-constraints
31168 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
31169 width, or precision) shall not appear in the wide string pointed to by format. Any
31170 argument to vwprintf_s corresponding to a %s specifier shall not be a null pointer.
31172 If there is a runtime-constraint violation, the vwprintf_s function does not attempt to
31173 produce further output, and it is unspecified to what extent vwprintf_s produced
31174 output before discovering the runtime-constraint violation.
31177 The vwprintf_s function is equivalent to the vwprintf function except for the
31178 explicit runtime-constraints listed above.
31181 The vwprintf_s function returns the number of wide characters transmitted, or a
31182 negative value if an output error, encoding error, or runtime-constraint violation occurred.
31187 <!--page 651 -->
31190 <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
31191 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
31192 example, if the entire format string was L"%%n".
31193 </small>
31198 <pre>
31199 #define __STDC_WANT_LIB_EXT1__ 1
31202 int vwscanf_s(const wchar_t * restrict format,
31203 va_list arg);
31204 </pre>
31205 Runtime-constraints
31207 format shall not be a null pointer. Any argument indirected though in order to store
31208 converted input shall not be a null pointer.
31210 If there is a runtime-constraint violation, the vwscanf_s function does not attempt to
31211 perform further input, and it is unspecified to what extent vwscanf_s performed input
31212 before discovering the runtime-constraint violation.
31215 The vwscanf_s function is equivalent to wscanf_s, with the variable argument list
31216 replaced by arg, which shall have been initialized by the va_start macro (and
31217 possibly subsequent va_arg calls). The vwscanf_s function does not invoke the
31221 The vwscanf_s function returns the value of the macro EOF if an input failure occurs
31222 before any conversion or if there is a runtime-constraint violation. Otherwise, the
31223 vwscanf_s function returns the number of input items assigned, which can be fewer
31224 than provided for, or even zero, in the event of an early matching failure.
31227 <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
31228 value of arg after the return is indeterminate.
31229 </small>
31234 <pre>
31235 #define __STDC_WANT_LIB_EXT1__ 1
31237 int wprintf_s(const wchar_t * restrict format, ...);
31238 </pre>
31239 Runtime-constraints
31241 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
31243 <!--page 652 -->
31244 width, or precision) shall not appear in the wide string pointed to by format. Any
31245 argument to wprintf_s corresponding to a %s specifier shall not be a null pointer.
31247 If there is a runtime-constraint violation, the wprintf_s function does not attempt to
31248 produce further output, and it is unspecified to what extent wprintf_s produced output
31249 before discovering the runtime-constraint violation.
31252 The wprintf_s function is equivalent to the wprintf function except for the explicit
31253 runtime-constraints listed above.
31256 The wprintf_s function returns the number of wide characters transmitted, or a
31257 negative value if an output error, encoding error, or runtime-constraint violation occurred.
31260 <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
31261 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
31262 example, if the entire format string was L"%%n".
31263 </small>
31268 <pre>
31269 #define __STDC_WANT_LIB_EXT1__ 1
31271 int wscanf_s(const wchar_t * restrict format, ...);
31272 </pre>
31273 Runtime-constraints
31275 format shall not be a null pointer. Any argument indirected though in order to store
31276 converted input shall not be a null pointer.
31278 If there is a runtime-constraint violation, the wscanf_s function does not attempt to
31279 perform further input, and it is unspecified to what extent wscanf_s performed input
31280 before discovering the runtime-constraint violation.
31283 The wscanf_s function is equivalent to fwscanf_s with the argument stdin
31284 interposed before the arguments to wscanf_s.
31287 The wscanf_s function returns the value of the macro EOF if an input failure occurs
31288 before any conversion or if there is a runtime-constraint violation. Otherwise, the
31289 wscanf_s function returns the number of input items assigned, which can be fewer than
31290 provided for, or even zero, in the event of an early matching failure.
31291 <!--page 653 -->
31300 <pre>
31301 #define __STDC_WANT_LIB_EXT1__ 1
31303 errno_t wcscpy_s(wchar_t * restrict s1,
31304 rsize_t s1max,
31305 const wchar_t * restrict s2);
31306 </pre>
31307 Runtime-constraints
31309 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
31310 s1max shall not equal zero. s1max shall be greater than wcsnlen_s(s2, s1max).
31311 Copying shall not take place between objects that overlap.
31313 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31314 greater than zero and not greater than RSIZE_MAX, then wcscpy_s sets s1[0] to the
31315 null wide character.
31318 The wcscpy_s function copies the wide string pointed to by s2 (including the
31319 terminating null wide character) into the array pointed to by s1.
31321 All elements following the terminating null wide character (if any) written by
31322 wcscpy_s in the array of s1max wide characters pointed to by s1 take unspecified
31326 The wcscpy_s function returns zero<sup><a href="#note429"><b>429)</b></a></sup> if there was no runtime-constraint violation.
31327 Otherwise, a nonzero value is returned.
31332 <!--page 654 -->
31335 <p><small><a name="note428" href="#note428">428)</a> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
31336 if any of those wide characters are null. Such an approach might write a wide character to every
31337 element of s1 before discovering that the first element should be set to the null wide character.
31338 </small>
31339 <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
31340 fit within the array pointed to by s1 and that the result in s1 is null terminated.
31341 </small>
31346 <pre>
31347 #define __STDC_WANT_LIB_EXT1__ 1
31349 errno_t wcsncpy_s(wchar_t * restrict s1,
31350 rsize_t s1max,
31351 const wchar_t * restrict s2,
31352 rsize_t n);
31353 </pre>
31354 Runtime-constraints
31356 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31357 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
31358 shall be greater than wcsnlen_s(s2, s1max). Copying shall not take place between
31359 objects that overlap.
31361 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31362 greater than zero and not greater than RSIZE_MAX, then wcsncpy_s sets s1[0] to the
31363 null wide character.
31366 The wcsncpy_s function copies not more than n successive wide characters (wide
31367 characters that follow a null wide character are not copied) from the array pointed to by
31368 s2 to the array pointed to by s1. If no null wide character was copied from s2, then
31369 s1[n] is set to a null wide character.
31371 All elements following the terminating null wide character (if any) written by
31372 wcsncpy_s in the array of s1max wide characters pointed to by s1 take unspecified
31376 The wcsncpy_s function returns zero<sup><a href="#note431"><b>431)</b></a></sup> if there was no runtime-constraint violation.
31377 Otherwise, a nonzero value is returned.
31379 EXAMPLE 1 The wcsncpy_s function can be used to copy a wide string without the danger that the
31380 result will not be null terminated or that wide characters will be written past the end of the destination
31381 array.
31386 <!--page 655 -->
31387 <pre>
31388 #define __STDC_WANT_LIB_EXT1__ 1
31390 /* ... */
31392 wchar_t src2[7] = {L'g', L'o', L'o', L'd', L'b', L'y', L'e'};
31394 int r1, r2, r3;
31398 </pre>
31399 The first call will assign to r1 the value zero and to dst1 the sequence of wide characters hello\0.
31400 The second call will assign to r2 a nonzero value and to dst2 the sequence of wide characters \0.
31401 The third call will assign to r3 the value zero and to dst3 the sequence of wide characters good\0.
31405 <p><small><a name="note430" href="#note430">430)</a> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
31406 if any of those wide characters are null. Such an approach might write a wide character to every
31407 element of s1 before discovering that the first element should be set to the null wide character.
31408 </small>
31409 <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
31410 fit within the array pointed to by s1 and that the result in s1 is null terminated.
31411 </small>
31416 <pre>
31417 #define __STDC_WANT_LIB_EXT1__ 1
31419 errno_t wmemcpy_s(wchar_t * restrict s1,
31420 rsize_t s1max,
31421 const wchar_t * restrict s2,
31422 rsize_t n);
31423 </pre>
31424 Runtime-constraints
31426 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31427 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
31428 objects that overlap.
31430 If there is a runtime-constraint violation, the wmemcpy_s function stores zeros in the
31431 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
31432 s1max is not greater than RSIZE_MAX.
31435 The wmemcpy_s function copies n successive wide characters from the object pointed
31436 to by s2 into the object pointed to by s1.
31439 The wmemcpy_s function returns zero if there was no runtime-constraint violation.
31440 Otherwise, a nonzero value is returned.
31441 <!--page 656 -->
31446 <pre>
31447 #define __STDC_WANT_LIB_EXT1__ 1
31449 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
31450 const wchar_t *s2, rsize_t n);
31451 </pre>
31452 Runtime-constraints
31454 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31455 RSIZE_MAX. n shall not be greater than s1max.
31457 If there is a runtime-constraint violation, the wmemmove_s function stores zeros in the
31458 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
31459 s1max is not greater than RSIZE_MAX.
31462 The wmemmove_s function copies n successive wide characters from the object pointed
31463 to by s2 into the object pointed to by s1. This copying takes place as if the n wide
31464 characters from the object pointed to by s2 are first copied into a temporary array of n
31465 wide characters that does not overlap the objects pointed to by s1 or s2, and then the n
31466 wide characters from the temporary array are copied into the object pointed to by s1.
31469 The wmemmove_s function returns zero if there was no runtime-constraint violation.
31470 Otherwise, a nonzero value is returned.
31472 <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>
31477 <pre>
31478 #define __STDC_WANT_LIB_EXT1__ 1
31480 errno_t wcscat_s(wchar_t * restrict s1,
31481 rsize_t s1max,
31482 const wchar_t * restrict s2);
31483 </pre>
31484 Runtime-constraints
31486 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
31487 wcscat_s.
31489 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
31490 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note432"><b>432)</b></a></sup> m shall be greater than
31491 wcsnlen_s(s2, m). Copying shall not take place between objects that overlap.
31492 <!--page 657 -->
31494 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31495 greater than zero and not greater than RSIZE_MAX, then wcscat_s sets s1[0] to the
31496 null wide character.
31499 The wcscat_s function appends a copy of the wide string pointed to by s2 (including
31500 the terminating null wide character) to the end of the wide string pointed to by s1. The
31501 initial wide character from s2 overwrites the null wide character at the end of s1.
31503 All elements following the terminating null wide character (if any) written by
31504 wcscat_s in the array of s1max wide characters pointed to by s1 take unspecified
31508 The wcscat_s function returns zero<sup><a href="#note434"><b>434)</b></a></sup> if there was no runtime-constraint violation.
31509 Otherwise, a nonzero value is returned.
31512 <p><small><a name="note432" href="#note432">432)</a> Zero means that s1 was not null terminated upon entry to wcscat_s.
31513 </small>
31514 <p><small><a name="note433" href="#note433">433)</a> This allows an implementation to append wide characters from s2 to s1 while simultaneously
31515 checking if any of those wide characters are null. Such an approach might write a wide character to
31516 every element of s1 before discovering that the first element should be set to the null wide character.
31517 </small>
31518 <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
31519 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
31520 </small>
31525 <pre>
31526 #define __STDC_WANT_LIB_EXT1__ 1
31528 errno_t wcsncat_s(wchar_t * restrict s1,
31529 rsize_t s1max,
31530 const wchar_t * restrict s2,
31531 rsize_t n);
31532 </pre>
31533 Runtime-constraints
31535 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
31536 wcsncat_s.
31538 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
31539 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
31540 than m, then m shall be greater than wcsnlen_s(s2, m). Copying shall not take
31541 place between objects that overlap.
31544 <!--page 658 -->
31546 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
31547 greater than zero and not greater than RSIZE_MAX, then wcsncat_s sets s1[0] to the
31548 null wide character.
31551 The wcsncat_s function appends not more than n successive wide characters (wide
31552 characters that follow a null wide character are not copied) from the array pointed to by
31553 s2 to the end of the wide string pointed to by s1. The initial wide character from s2
31554 overwrites the null wide character at the end of s1. If no null wide character was copied
31555 from s2, then s1[s1max-m+n] is set to a null wide character.
31557 All elements following the terminating null wide character (if any) written by
31558 wcsncat_s in the array of s1max wide characters pointed to by s1 take unspecified
31562 The wcsncat_s function returns zero<sup><a href="#note437"><b>437)</b></a></sup> if there was no runtime-constraint violation.
31563 Otherwise, a nonzero value is returned.
31565 EXAMPLE 1 The wcsncat_s function can be used to copy a wide string without the danger that the
31566 result will not be null terminated or that wide characters will be written past the end of the destination
31567 array.
31568 <pre>
31569 #define __STDC_WANT_LIB_EXT1__ 1
31571 /* ... */
31577 int r1, r2, r3, r4;
31582 </pre>
31583 After the first call r1 will have the value zero and s1 will be the wide character sequence goodbye\0.
31584 After the second call r2 will have the value zero and s2 will be the wide character sequence hello\0.
31585 After the third call r3 will have a nonzero value and s3 will be the wide character sequence \0.
31586 After the fourth call r4 will have the value zero and s4 will be the wide character sequence abcdef\0.
31591 <!--page 659 -->
31594 <p><small><a name="note435" href="#note435">435)</a> Zero means that s1 was not null terminated upon entry to wcsncat_s.
31595 </small>
31596 <p><small><a name="note436" href="#note436">436)</a> This allows an implementation to append wide characters from s2 to s1 while simultaneously
31597 checking if any of those wide characters are null. Such an approach might write a wide character to
31598 every element of s1 before discovering that the first element should be set to the null wide character.
31599 </small>
31600 <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
31601 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
31602 </small>
31609 <pre>
31610 #define __STDC_WANT_LIB_EXT1__ 1
31612 wchar_t *wcstok_s(wchar_t * restrict s1,
31613 rsize_t * restrict s1max,
31614 const wchar_t * restrict s2,
31615 wchar_t ** restrict ptr);
31616 </pre>
31617 Runtime-constraints
31619 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
31620 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
31621 The end of the token found shall occur within the first *s1max wide characters of s1 for
31622 the first call, and shall occur within the first *s1max wide characters of where searching
31623 resumes on subsequent calls.
31625 If there is a runtime-constraint violation, the wcstok_s function does not indirect
31626 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
31629 A sequence of calls to the wcstok_s function breaks the wide string pointed to by s1
31630 into a sequence of tokens, each of which is delimited by a wide character from the wide
31631 string pointed to by s2. The fourth argument points to a caller-provided wchar_t
31632 pointer into which the wcstok_s function stores information necessary for it to
31633 continue scanning the same wide string.
31635 The first call in a sequence has a non-null first argument and s1max points to an object
31636 whose value is the number of elements in the wide character array pointed to by the first
31637 argument. The first call stores an initial value in the object pointed to by ptr and
31638 updates the value pointed to by s1max to reflect the number of elements that remain in
31639 relation to ptr. Subsequent calls in the sequence have a null first argument and the
31640 objects pointed to by s1max and ptr are required to have the values stored by the
31641 previous call in the sequence, which are then updated. The separator wide string pointed
31642 to by s2 may be different from call to call.
31644 The first call in the sequence searches the wide string pointed to by s1 for the first wide
31645 character that is not contained in the current separator wide string pointed to by s2. If no
31646 such wide character is found, then there are no tokens in the wide string pointed to by s1
31647 and the wcstok_s function returns a null pointer. If such a wide character is found, it is
31648 the start of the first token.
31649 <!--page 660 -->
31651 The wcstok_s function then searches from there for the first wide character in s1 that
31652 is contained in the current separator wide string. If no such wide character is found, the
31653 current token extends to the end of the wide string pointed to by s1, and subsequent
31654 searches in the same wide string for a token return a null pointer. If such a wide character
31655 is found, it is overwritten by a null wide character, which terminates the current token.
31657 In all cases, the wcstok_s function stores sufficient information in the pointer pointed
31658 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
31659 value for ptr, shall start searching just past the element overwritten by a null wide
31660 character (if any).
31663 The wcstok_s function returns a pointer to the first wide character of a token, or a null
31664 pointer if there is no token or there is a runtime-constraint violation.
31666 EXAMPLE
31667 <pre>
31668 #define __STDC_WANT_LIB_EXT1__ 1
31670 static wchar_t str1[] = L"?a???b,,,#c";
31671 static wchar_t str2[] = L"\t \t";
31672 wchar_t *t, *ptr1, *ptr2;
31673 rsize_t max1 = wcslen(str1)+1;
31674 rsize_t max2 = wcslen(str2)+1;
31680 </pre>
31688 <pre>
31689 #define __STDC_WANT_LIB_EXT1__ 1
31691 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
31692 </pre>
31695 The wcsnlen_s function computes the length of the wide string pointed to by s.
31698 If s is a null pointer,<sup><a href="#note438"><b>438)</b></a></sup> then the wcsnlen_s function returns zero.
31700 Otherwise, the wcsnlen_s function returns the number of wide characters that precede
31701 the terminating null wide character. If there is no null wide character in the first
31702 maxsize wide characters of s then wcsnlen_s returns maxsize. At most the first
31703 <!--page 661 -->
31704 maxsize wide characters of s shall be accessed by wcsnlen_s.
31707 <p><small><a name="note438" href="#note438">438)</a> Note that the wcsnlen_s function has no runtime-constraints. This lack of runtime-constraints
31708 along with the values returned for a null pointer or an unterminated wide string argument make
31709 wcsnlen_s useful in algorithms that gracefully handle such exceptional data.
31710 </small>
31712 <h5><a name="K.3.9.3" href="#K.3.9.3">K.3.9.3 Extended multibyte/wide character conversion utilities</a></h5>
31714 <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>
31716 Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the
31717 conversion state) to be a null pointer.
31722 <pre>
31724 errno_t wcrtomb_s(size_t * restrict retval,
31725 char * restrict s, rsize_t smax,
31726 wchar_t wc, mbstate_t * restrict ps);
31727 </pre>
31728 Runtime-constraints
31730 Neither retval nor ps shall be a null pointer. If s is not a null pointer, then smax
31731 shall not equal zero and shall not be greater than RSIZE_MAX. If s is not a null pointer,
31732 then smax shall be not be less than the number of bytes to be stored in the array pointed
31733 to by s. If s is a null pointer, then smax shall equal zero.
31735 If there is a runtime-constraint violation, then wcrtomb_s does the following. If s is
31736 not a null pointer and smax is greater than zero and not greater than RSIZE_MAX, then
31737 wcrtomb_s sets s[0] to the null character. If retval is not a null pointer, then
31738 wcrtomb_s sets *retval to (size_t)(-1).
31741 If s is a null pointer, the wcrtomb_s function is equivalent to the call
31742 <pre>
31744 </pre>
31745 where retval and buf are internal variables of the appropriate types, and the size of
31746 buf is greater than MB_CUR_MAX.
31748 If s is not a null pointer, the wcrtomb_s function determines the number of bytes
31749 needed to represent the multibyte character that corresponds to the wide character given
31750 by wc (including any shift sequences), and stores the multibyte character representation
31751 in the array whose first element is pointed to by s. At most MB_CUR_MAX bytes are
31752 stored. If wc is a null wide character, a null byte is stored, preceded by any shift
31753 sequence needed to restore the initial shift state; the resulting state described is the initial
31754 conversion state.
31756 <!--page 662 -->
31758 If wc does not correspond to a valid multibyte character, an encoding error occurs: the
31759 wcrtomb_s function stores the value (size_t)(-1) into *retval and the
31760 conversion state is unspecified. Otherwise, the wcrtomb_s function stores into
31761 *retval the number of bytes (including any shift sequences) stored in the array pointed
31762 to by s.
31765 The wcrtomb_s function returns zero if no runtime-constraint violation and no
31766 encoding error occurred. Otherwise, a nonzero value is returned.
31768 <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>
31770 Unlike mbsrtowcs and wcsrtombs, mbsrtowcs_s and wcsrtombs_s do not
31771 permit the ps parameter (the pointer to the conversion state) to be a null pointer.
31776 <pre>
31778 errno_t mbsrtowcs_s(size_t * restrict retval,
31779 wchar_t * restrict dst, rsize_t dstmax,
31780 const char ** restrict src, rsize_t len,
31781 mbstate_t * restrict ps);
31782 </pre>
31783 Runtime-constraints
31785 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
31786 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
31787 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
31788 not equal zero. If dst is not a null pointer and len is not less than dstmax, then a null
31789 character shall occur within the first dstmax multibyte characters of the array pointed to
31790 by *src.
31792 If there is a runtime-constraint violation, then mbsrtowcs_s does the following. If
31793 retval is not a null pointer, then mbsrtowcs_s sets *retval to (size_t)(-1).
31794 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
31795 then mbsrtowcs_s sets dst[0] to the null wide character.
31798 The mbsrtowcs_s function converts a sequence of multibyte characters that begins in
31799 the conversion state described by the object pointed to by ps, from the array indirectly
31800 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
31801 pointer, the converted characters are stored into the array pointed to by dst. Conversion
31802 continues up to and including a terminating null character, which is also stored.
31803 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
31804 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
31805 <!--page 663 -->
31806 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
31807 pointer and no null wide character was stored into the array pointed to by dst, then
31808 dst[len] is set to the null wide character. Each conversion takes place as if by a call
31809 to the mbrtowc function.
31811 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
31812 pointer (if conversion stopped due to reaching a terminating null character) or the address
31813 just past the last multibyte character converted (if any). If conversion stopped due to
31814 reaching a terminating null character and if dst is not a null pointer, the resulting state
31815 described is the initial conversion state.
31817 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
31818 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
31819 the mbsrtowcs_s function stores the value (size_t)(-1) into *retval and the
31820 conversion state is unspecified. Otherwise, the mbsrtowcs_s function stores into
31821 *retval the number of multibyte characters successfully converted, not including the
31822 terminating null character (if any).
31824 All elements following the terminating null wide character (if any) written by
31825 mbsrtowcs_s in the array of dstmax wide characters pointed to by dst take
31828 If copying takes place between objects that overlap, the objects take on unspecified
31829 values.
31832 The mbsrtowcs_s function returns zero if no runtime-constraint violation and no
31833 encoding error occurred. Otherwise, a nonzero value is returned.
31836 <p><small><a name="note439" href="#note439">439)</a> Thus, the value of len is ignored if dst is a null pointer.
31837 </small>
31838 <p><small><a name="note440" href="#note440">440)</a> This allows an implementation to attempt converting the multibyte string before discovering a
31839 terminating null character did not occur where required.
31840 </small>
31845 <pre>
31847 errno_t wcsrtombs_s(size_t * restrict retval,
31848 char * restrict dst, rsize_t dstmax,
31849 const wchar_t ** restrict src, rsize_t len,
31850 mbstate_t * restrict ps);
31851 </pre>
31856 <!--page 664 -->
31857 Runtime-constraints
31859 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
31860 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
31861 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
31862 not equal zero. If dst is not a null pointer and len is not less than dstmax, then the
31863 conversion shall have been stopped (see below) because a terminating null wide character
31864 was reached or because an encoding error occurred.
31866 If there is a runtime-constraint violation, then wcsrtombs_s does the following. If
31867 retval is not a null pointer, then wcsrtombs_s sets *retval to (size_t)(-1).
31868 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
31869 then wcsrtombs_s sets dst[0] to the null character.
31872 The wcsrtombs_s function converts a sequence of wide characters from the array
31873 indirectly pointed to by src into a sequence of corresponding multibyte characters that
31874 begins in the conversion state described by the object pointed to by ps. If dst is not a
31875 null pointer, the converted characters are then stored into the array pointed to by dst.
31876 Conversion continues up to and including a terminating null wide character, which is also
31877 stored. Conversion stops earlier in two cases:
31878 <ul>
31879 <li> when a wide character is reached that does not correspond to a valid multibyte
31880 character;
31881 <li> (if dst is not a null pointer) when the next multibyte character would exceed the
31882 limit of n total bytes to be stored into the array pointed to by dst. If the wide
31883 character being converted is the null wide character, then n is the lesser of len or
31884 dstmax. Otherwise, n is the lesser of len or dstmax-1.
31885 </ul>
31886 If the conversion stops without converting a null wide character and dst is not a null
31887 pointer, then a null character is stored into the array pointed to by dst immediately
31888 following any multibyte characters already stored. Each conversion takes place as if by a
31891 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
31892 pointer (if conversion stopped due to reaching a terminating null wide character) or the
31893 address just past the last wide character converted (if any). If conversion stopped due to
31894 reaching a terminating null wide character, the resulting state described is the initial
31895 conversion state.
31898 <!--page 665 -->
31900 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
31901 wide character that does not correspond to a valid multibyte character, an encoding error
31902 occurs: the wcsrtombs_s function stores the value (size_t)(-1) into *retval
31903 and the conversion state is unspecified. Otherwise, the wcsrtombs_s function stores
31904 into *retval the number of bytes in the resulting multibyte character sequence, not
31905 including the terminating null character (if any).
31907 All elements following the terminating null character (if any) written by wcsrtombs_s
31908 in the array of dstmax elements pointed to by dst take unspecified values when
31911 If copying takes place between objects that overlap, the objects take on unspecified
31912 values.
31915 The wcsrtombs_s function returns zero if no runtime-constraint violation and no
31916 encoding error occurred. Otherwise, a nonzero value is returned.
31921 <!--page 666 -->
31924 <p><small><a name="note441" href="#note441">441)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
31925 include those necessary to reach the initial shift state immediately before the null byte. However, if
31926 the conversion stops before a terminating null wide character has been reached, the result will be null
31927 terminated, but might not end in the initial shift state.
31928 </small>
31929 <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
31930 runtime-constraint violation.
31931 </small>
31934 <pre>
31935 (normative)
31936 Analyzability
31937 </pre>
31941 This annex specifies optional behavior that can aid in the analyzability of C programs.
31943 An implementation that defines __STDC_ANALYZABLE__ shall conform to the
31947 <p><small><a name="note443" href="#note443">443)</a> Implementations that do not define __STDC_ANALYZABLE__ are not required to conform to these
31948 specifications.
31949 </small>
31955 out-of-bounds store
31956 an (attempted) access (<a href="#3.1">3.1</a>) that, at run time, for a given computational state, would
31957 modify (or, for an object declared volatile, fetch) one or more bytes that lie outside
31958 the bounds permitted by this Standard.
31962 bounded undefined behavior
31965 NOTE 1 The behavior might perform a trap.
31968 NOTE 2 Any values produced or stored might be indeterminate values.
31973 critical undefined behavior
31974 undefined behavior that is not bounded undefined behavior.
31976 NOTE The behavior might perform an out-of-bounds store or perform a trap.
31981 <!--page 667 -->
31985 If the program performs a trap (<a href="#3.19.5">3.19.5</a>), the implementation is permitted to invoke a
31986 runtime-constraint handler. Any such semantics are implementation-defined.
31988 All undefined behavior shall be limited to bounded undefined behavior, except for the
31989 following which are permitted to result in critical undefined behavior:
31990 <ul>
31993 <li> A pointer is used to call a function whose type is not compatible with the referenced
31995 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
31996 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
31997 integer type produces a result that points just beyond the array object and is used as
31999 <li> An argument to a library function has an invalid value or a type not expected by a
32001 <li> The value of a pointer that refers to space deallocated by a call to the free or realloc
32003 <li> A string or wide string utility function is instructed to access an array beyond the end
32005 <!--page 668 -->
32006 </ul>
32009 <ol>
32010 <li> ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
32011 published in The C Programming Language by Brian W. Kernighan and Dennis
32014 California, USA, November 1984.
32016 Processing Systems, Information Processing Systems Technical Report.
32018 Arithmetic.
32020 Floating-Point Arithmetic.
32024 symbols for use in the physical sciences and technology.
32026 information interchange.
32028 Fundamental terms.
32031 interchange -- Representation of dates and times.
32040 <!--page 669 -->
32042 Interface (POSIX) -- Part 2: Shell and Utilities.
32044 preparation of programming language standards.
32046 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
32058 syllables.
32060 Tibetan.
32062 additional characters.
32065 Identifiers for characters.
32067 Ethiopic.
32069 Unified Canadian Aboriginal Syllabics.
32071 Cherokee.
32073 arithmetic -- Part 1: Integer and floating point arithmetic.
32074 <!--page 670 -->
32076 their environments and system software interfaces -- Extensions for the
32077 programming language C to support new character data types.
32079 their environments and system software interfaces -- Extensions to the C library
32080 -- Part 1: Bounds-checking interfaces.
32081 <!--page 671 -->
32082 </ol>
32085 <pre>
32086 [^ 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>
32087 , (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>,
32089 ! (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>
32090 != (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>
32091 # 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>
32092 # 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>
32093 # punctuator, <a href="#6.10">6.10</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
32094 ## 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>
32095 #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>,
32097 #else preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.9">6.7.9</a>
32098 #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>
32099 #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>
32100 #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>
32101 <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>
32102 #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>
32103 #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>
32104 #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>
32105 <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>,
32106 #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>
32107 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
32108 #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>
32110 % (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>
32111 %: (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>
32112 %:%: (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>
32113 %= (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>
32114 %> (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>,
32115 & (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>
32116 & (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>
32117 && (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>
32118 &= (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>,
32119 ' ' (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>
32120 <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>,
32122 ( ) (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>
32123 ( ) (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>
32124 ( ){ } (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>
32125 * (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>
32126 * (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>,
32127 * (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>
32128 <a href="#G.5.1">G.5.1</a> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
32129 *= (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>
32130 + (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>
32131 <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>
32132 + (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>
32133 ++ (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>
32134 ++ (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>,
32136 <!--page 672 -->
32137 <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
32138 <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>
32139 <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>
32140 <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),
32142 <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>
32144 <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>
32145 <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>
32146 <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>
32147 <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>
32148 <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>
32149 <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>
32150 <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>
32151 <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>
32152 = (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>
32153 = (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>
32154 == (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>
32156 >= (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>
32157 >> (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>
32158 >>= (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>
32159 ? : (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,
32160 ?? (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>
32161 [ ] (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>,
32162 [ ] (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>
32163 \ (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>,
32164 \ (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>
32165 \" (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>
32166 <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>
32167 \\ (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>
32168 \' (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>
32169 \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>
32170 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>
32171 \? (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>
32172 \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>
32173 \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>
32174 \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>,
32176 \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>
32177 <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>
32179 <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>
32180 \r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, _Imaginary keyword, <a href="#G.2">G.2</a>
32181 <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>
32182 \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>
32183 <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>
32184 \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>
32185 \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>
32186 \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>
32187 <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>
32188 <!--page 673 -->
32189 _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>
32190 _Thread_local storage-class specifier, <a href="#6.2.4">6.2.4</a>, and macro, <a href="#7.9">7.9</a>
32192 { } (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>
32194 { } (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>
32195 | (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>
32196 |= (bitwise inclusive OR assignment operator), anonymous structure, <a href="#6.7.2.1">6.7.2.1</a>
32198 || (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>
32199 ~ (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>
32201 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>
32202 <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>
32203 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>
32204 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>
32206 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>
32207 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>
32208 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>
32209 abstract declarator, <a href="#6.7.7">6.7.7</a> arithmetic conversions, usual, see usual arithmetic
32211 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
32212 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>
32213 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>
32214 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>
32215 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>
32216 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>
32218 acquire operation, <a href="#5.1.2.4">5.1.2.4</a> arithmetic types, <a href="#6.2.5">6.2.5</a>
32222 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>
32223 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>
32224 <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>
32225 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>
32227 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>
32231 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>
32234 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>
32235 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>
32236 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>
32237 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>
32238 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>
32239 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>
32240 <!--page 674 -->
32241 asinh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> atomic_is_lock_free generic function,
32243 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>
32244 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>
32246 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>
32247 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>
32248 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>
32249 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>
32250 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>
32251 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>
32252 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>
32253 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>
32254 <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>
32256 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>
32257 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>
32258 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>
32259 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>
32260 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>
32261 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>
32262 <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>,
32263 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>
32264 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>
32265 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>
32266 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>
32267 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>
32269 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>
32270 <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>
32271 <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>
32272 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>
32273 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>
32274 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>
32275 ATOMIC_CHAR16_T_LOCK_FREE macro, exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
32276 <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>
32277 ATOMIC_CHAR32_T_LOCK_FREE macro, inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
32278 <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>
32279 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>
32280 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>
32282 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>
32285 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>
32286 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>
32287 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>
32288 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>,
32290 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>
32291 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>
32292 <!--page 675 -->
32294 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>
32295 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>
32296 <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>
32297 <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>
32298 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>
32299 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>
32300 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>
32301 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>
32302 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>
32303 byte input/output functions, <a href="#7.21.1">7.21.1</a> cexpm1 function, <a href="#7.30.1">7.30.1</a>
32304 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>,
32306 <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>,
32308 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>
32309 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>
32310 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>
32311 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>
32312 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>
32313 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>
32314 type-generic macro for, <a href="#7.24">7.24</a> character array initialization, <a href="#6.7.9">6.7.9</a>
32315 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>
32316 <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>
32317 <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>
32318 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>
32319 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>
32320 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>
32321 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>
32322 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>
32323 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>
32324 <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>
32325 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>
32326 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>
32327 case mapping functions character string literal, see string literal
32328 character, <a href="#7.4.2">7.4.2</a> character type conversion, <a href="#6.3.1.1">6.3.1.1</a>
32329 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>
32330 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>
32331 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>
32333 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
32336 cast operator (( )), <a href="#6.5.4">6.5.4</a> wide character, <a href="#7.29.2.1">7.29.2.1</a>
32337 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>
32338 type-generic macro for, <a href="#7.24">7.24</a> clearerr function, <a href="#7.21.10.1">7.21.10.1</a>
32339 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>
32340 type-generic macro for, <a href="#7.24">7.24</a> clock function, <a href="#7.26.2.1">7.26.2.1</a>
32341 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>
32342 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>
32343 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>
32344 <!--page 676 -->
32345 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>
32346 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>
32350 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>,
32351 <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>
32352 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>
32353 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>
32354 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>
32356 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>
32357 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>
32358 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>
32359 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>
32360 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>
32361 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>
32362 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>
32363 <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>
32364 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>
32365 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> floating, <a href="#6.4.4.2">6.4.4.2</a>
32366 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>
32369 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>
32371 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>
32372 <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>
32373 string, <a href="#7.23.4">7.23.4</a> contiguity of allocated storage, <a href="#7.22.3">7.22.3</a>
32374 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>
32375 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>
32376 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>
32377 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>
32379 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>
32382 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>
32383 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>
32384 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>
32385 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>
32386 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>
32387 <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>
32389 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>
32390 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>
32391 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>
32392 compound literals, <a href="#6.5.2.5">6.5.2.5</a> function parameter, <a href="#6.9.1">6.9.1</a>
32394 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>
32396 <!--page 677 -->
32397 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>
32398 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>
32399 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>
32400 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.24">7.24</a>
32401 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>
32402 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>
32403 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>
32407 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>
32408 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>
32409 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>
32410 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>
32412 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>,
32413 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>,
32414 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>
32416 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>
32417 wide character, <a href="#7.28.5">7.28.5</a> Daylight Saving Time, <a href="#7.26.1">7.26.1</a>
32418 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>
32420 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>
32421 <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>
32422 <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>
32423 <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>
32424 <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>
32426 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>
32428 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>
32429 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>
32430 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>
32432 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>
32433 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>,
32434 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>
32435 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>
32436 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>
32437 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>
32438 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>
32439 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>
32441 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>
32443 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>
32444 creal type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
32446 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>
32447 type-generic macro for, <a href="#7.24">7.24</a> default initialization, <a href="#6.7.9">6.7.9</a>
32448 <!--page 678 -->
32449 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>
32450 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>
32451 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>
32454 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>,
32455 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>,
32456 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>,
32457 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>,
32460 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>,
32461 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>,
32462 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>,
32466 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>
32467 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>
32469 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>
32470 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>
32471 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>
32472 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>
32473 documentation of implementation, <a href="#4">4</a> enumeration specifiers, <a href="#6.7.2.2">6.7.2.2</a>
32474 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>
32475 <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>
32476 <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>
32477 <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>
32478 <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>
32479 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> environmental considerations, <a href="#5.2">5.2</a>
32480 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>,
32481 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>,
32482 <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>
32483 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>,
32484 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>,
32485 <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>,
32486 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>,
32487 <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>,
32488 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>,
32489 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>,
32490 <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>,
32491 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>,
32493 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>
32495 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>
32496 <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>
32497 <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>,
32498 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
32500 <!--page 679 -->
32501 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>
32502 erf type-generic macro, <a href="#7.24">7.24</a> exp2 type-generic macro, <a href="#7.24">7.24</a>
32503 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>
32504 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>
32505 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>
32506 <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>
32507 <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
32508 <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>
32509 <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>
32510 <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>
32511 <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>
32512 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>
32513 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>
32514 <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>
32516 domain, see domain error order of evaluation, see order of evaluation
32520 error conditions, <a href="#7.12.1">7.12.1</a> expression statement, <a href="#6.8.3">6.8.3</a>
32521 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>
32522 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>
32523 <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>
32524 <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>,
32526 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> extended multibyte/wide character conversion
32527 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>
32528 <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,
32530 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,
32531 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>
32532 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>
32533 evaluation of expression, <a href="#5.1.2.3">5.1.2.3</a> external definition, <a href="#6.9">6.9</a>
32534 evaluation order, see order of evaluation external identifiers, underscore, <a href="#7.1.3">7.1.3</a>
32536 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>
32537 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>
32538 exclusive OR operators
32539 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>
32540 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>
32542 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>
32543 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>
32545 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>
32546 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>
32547 <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>
32548 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>
32549 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>
32550 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>
32551 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>
32552 <!--page 680 -->
32553 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>,
32554 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>
32555 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>
32556 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>
32557 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>,
32558 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>
32559 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>,
32560 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>
32561 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>
32562 <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>
32563 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>
32564 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>,
32565 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>
32566 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>
32567 <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>,
32568 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
32569 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>
32570 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>
32571 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>
32572 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>
32573 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>
32574 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>
32575 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>
32576 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>
32577 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>
32578 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>
32579 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>
32580 <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>
32581 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>
32582 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>,
32583 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>
32585 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>
32586 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>
32588 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>
32590 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>
32591 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>
32592 <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>,
32593 <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>
32594 <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>
32595 <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>
32596 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>
32597 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>
32598 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>
32599 FILENAME_MAX macro, <a href="#7.21.1">7.21.1</a> fmax type-generic macro, <a href="#7.24">7.24</a>
32600 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>
32602 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>
32603 float _Complex type, <a href="#6.2.5">6.2.5</a> fmod type-generic macro, <a href="#7.24">7.24</a>
32604 <!--page 681 -->
32605 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>
32606 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>,
32607 <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>
32608 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>,
32609 <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>
32610 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>
32611 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>
32612 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>
32615 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>
32616 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>
32618 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>
32619 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>
32620 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>
32621 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>
32624 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>
32625 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>
32626 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>
32627 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>
32628 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>,
32629 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>
32630 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>
32631 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>
32632 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>
32633 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>
32634 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>
32635 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>
32636 <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>
32637 <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>
32638 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>
32639 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>
32640 <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>
32641 fputs function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.4">7.21.7.4</a> future directions
32642 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>
32644 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>
32645 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>,
32646 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>,
32647 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>
32649 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>
32650 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>,
32651 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>,
32653 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>,
32654 <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>
32656 <!--page 682 -->
32657 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>
32658 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>
32659 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>
32660 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>
32662 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>
32663 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>
32664 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>,
32665 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>,
32669 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
32670 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,
32672 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>,
32673 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>
32675 greater-than operator (>), <a href="#6.5.8">6.5.8</a> ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a>
32676 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>
32678 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>
32679 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>
32680 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>
32682 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>
32685 (\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>
32687 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>
32688 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>,
32689 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
32690 <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
32691 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>
32692 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>
32693 <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>
32694 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>
32695 <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>
32696 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
32697 <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>
32699 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>
32700 real, <a href="#7.12.5">7.12.5</a>, <a href="#F.10.2">F.10.2</a> increment operators, see arithmetic operators,
32701 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
32702 hypot type-generic macro, <a href="#7.24">7.24</a> indeterminate value, <a href="#3.19.2">3.19.2</a>
32704 <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,
32706 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>
32707 maximum length, <a href="#6.4.2.1">6.4.2.1</a> inequality operator (!=), <a href="#6.5.9">6.5.9</a>
32708 <!--page 683 -->
32709 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>
32710 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>
32711 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>
32712 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>
32713 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>
32716 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>
32717 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>
32718 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>,
32719 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>
32721 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>
32722 <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>
32723 <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>
32724 <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>
32726 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>
32727 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>
32728 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>
32729 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>
32731 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>,
32732 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>
32733 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>,
32734 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>
32735 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>
32737 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>
32738 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>
32739 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>
32740 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>
32741 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>
32742 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>
32743 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>,
32744 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>
32745 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>
32747 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>
32748 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>
32749 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>
32750 <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>
32752 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>
32753 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>
32754 <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>
32755 <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> *
32756 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>
32757 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>,
32759 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>,
32760 <!--page 684 -->
32761 <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>
32762 <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>,
32763 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>
32764 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>,
32765 <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>,
32766 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>
32767 <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>
32768 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>
32769 <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>
32770 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>
32771 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>
32772 <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>
32773 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>
32774 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>
32775 <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>
32776 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>
32777 <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>
32778 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>
32779 <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>
32780 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>
32782 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>
32783 <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>
32784 <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>
32785 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>
32786 <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>
32787 <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>
32788 <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>
32789 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>
32790 <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
32791 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>
32792 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>
32793 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>
32794 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>
32795 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>,
32796 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>
32797 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>,
32799 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>
32800 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>
32801 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>
32803 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>
32804 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>
32805 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>
32812 <!--page 685 -->
32813 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>
32815 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>
32816 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>,
32817 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>
32818 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>,
32819 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>
32820 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>,
32821 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>
32822 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>,
32823 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>
32824 <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>
32825 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>,
32826 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>
32827 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>,
32828 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>
32829 <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>
32830 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>
32831 <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>
32832 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>,
32834 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>
32837 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>
32838 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>
32839 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>
32840 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>
32841 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>,
32843 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>,
32844 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>
32846 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>
32848 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>
32849 log1p type-generic macro, <a href="#7.24">7.24</a> macro invocation, <a href="#6.10.3">6.10.3</a>
32850 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>
32853 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>
32854 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>
32855 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>
32856 logb type-generic macro, <a href="#7.24">7.24</a> macro preprocessor, <a href="#6.10">6.10</a>
32858 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>
32859 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>,
32860 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>
32861 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>
32864 <!--page 686 -->
32865 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>
32866 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>
32867 <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>
32868 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>
32869 <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>
32870 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>
32871 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>
32872 MATH_ERRNO macro, <a href="#7.12">7.12</a> mtx_lock function, <a href="#7.25.4.3">7.25.4.3</a>
32874 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>
32875 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>
32876 <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>,
32877 <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>
32878 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>
32879 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
32880 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>
32881 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>
32882 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>
32883 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>
32884 <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>
32885 <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>
32886 mbsinit function, <a href="#7.28.6.2.1">7.28.6.2.1</a> multibyte/wide character conversion functions,
32887 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>
32888 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>
32889 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>
32890 <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,
32891 <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>
32892 <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>
32893 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>
32894 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>
32895 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>,
32897 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>
32899 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>
32900 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>
32902 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>
32904 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>
32906 memory management functions, <a href="#7.22.3">7.22.3</a> structure/union member, <a href="#6.2.3">6.2.3</a>
32907 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>
32908 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>
32910 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>
32911 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>
32913 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>,
32914 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>
32915 mktime function, <a href="#7.26.2.3">7.26.2.3</a> nearbyint type-generic macro, <a href="#7.24">7.24</a>
32916 <!--page 687 -->
32917 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>
32918 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>
32919 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>
32920 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>
32921 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>
32923 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>
32926 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>
32929 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>
32930 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>
32931 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>
32934 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>
32938 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>
32939 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>
32940 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>
32941 <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>
32942 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>
32944 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>
32945 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>,
32947 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>
32948 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>
32949 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>
32955 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>
32956 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>
32957 obsolescence, <a href="#6.11">6.11</a>, <a href="#7.30">7.30</a> parameter, <a href="#3.16">3.16</a>
32959 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>
32960 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>
32964 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>
32965 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>
32966 ones' complement, <a href="#6.2.6.2">6.2.6.2</a> parenthesized expression, <a href="#6.5.1">6.5.1</a>
32967 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>
32968 <!--page 688 -->
32970 permitted form of initializer, <a href="#6.6">6.6</a> PRIcFASTN macros, <a href="#7.8.1">7.8.1</a>
32971 perror function, <a href="#7.21.10.4">7.21.10.4</a> PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a>
32972 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>
32973 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>
32975 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>
32976 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>,
32978 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>
32979 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>
32980 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>
32982 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>
32984 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>
32985 <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>
32986 <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>
32987 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>
32988 position indicator, file, see file position indicator program structure, <a href="#5.1.1.1">5.1.1.1</a>
32989 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>,
32990 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>
32991 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>
32992 postfix expressions, <a href="#6.5.2">6.5.2</a> program, strictly conforming, <a href="#4">4</a>
32993 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
32994 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>
32995 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>
32996 power functions prototype, see function prototype
32997 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>
32998 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>
33000 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>,
33001 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>
33003 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>
33004 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>
33005 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>
33006 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>
33007 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>
33008 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>
33009 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>
33010 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>
33011 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>
33012 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>
33014 #, <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>,
33016 _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>
33018 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>
33019 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>
33020 <!--page 689 -->
33021 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>
33023 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>,
33024 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>
33025 <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>
33026 <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>
33027 <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>
33028 <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>
33029 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>
33030 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>
33031 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>
33032 <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>,
33033 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>,
33034 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>,
33035 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>,
33036 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>,
33037 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>,
33038 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>,
33039 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>,
33040 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>,
33041 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>,
33042 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>
33043 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>,
33044 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>
33045 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>
33046 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>
33047 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>
33050 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>
33051 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>
33052 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>
33053 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>
33054 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>
33056 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>
33057 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>
33058 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>
33059 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>
33060 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>
33061 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>
33062 representations of types, <a href="#6.2.6">6.2.6</a> SCNcFASTN macros, <a href="#7.8.1">7.8.1</a>
33064 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>
33065 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>
33067 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>
33068 restartable multibyte/wide string conversion search functions
33069 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>
33070 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>
33071 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>
33072 <!--page 690 -->
33073 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>
33074 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>
33075 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>
33076 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>
33077 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>
33078 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>
33079 <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>
33080 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>
33081 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>
33082 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>,
33083 <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>
33084 <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>
33085 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>
33086 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>,
33087 <a href="#6.5.16">6.5.16</a>, see also indeterminately sequenced, <a href="#6.3.1.8">6.3.1.8</a>
33089 sequencing of statements, <a href="#6.8">6.8</a> significand part, <a href="#6.4.4.2">6.4.4.2</a>
33090 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>
33091 <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>
33092 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>
33093 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>
33094 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>
33095 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>
33096 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,
33097 <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>
33099 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>
33101 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>
33102 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>
33103 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>
33104 <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>,
33105 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>,
33106 <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>,
33107 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>
33108 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>
33109 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>,
33110 <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>
33111 <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>
33112 <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>
33113 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>
33114 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>
33115 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>
33116 <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>
33117 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>
33118 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>
33119 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>
33120 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>,
33121 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>
33122 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>
33123 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>
33124 <!--page 691 -->
33125 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>
33128 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>
33129 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>
33130 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>
33131 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>
33133 <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>
33134 <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>
33135 <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>
33136 <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>
33137 <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>
33138 <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>
33140 <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>
33141 <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>
33142 <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>
33143 <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>
33144 <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>
33146 <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>
33147 <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>
33148 <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>
33149 <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>
33150 <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>
33151 <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>,
33152 <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>
33153 <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>
33154 <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>,
33155 <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>,
33156 <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>
33157 <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>,
33158 <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>
33159 <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>
33160 <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>,
33161 <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>
33162 <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>,
33163 <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>
33164 <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>
33165 <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>
33166 <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>
33167 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>
33168 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>
33169 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>
33170 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>
33171 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>
33172 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>
33176 <!--page 692 -->
33177 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>
33178 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>
33179 line buffered, <a href="#7.21.3">7.21.3</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
33181 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>
33182 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>
33184 unbuffered, <a href="#7.21.3">7.21.3</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
33185 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>
33186 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>
33187 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>
33188 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>
33189 <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>
33190 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>
33191 strictly conforming program, <a href="#4">4</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
33193 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>
33194 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>
33195 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>
33196 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>
33197 library function conventions, <a href="#7.23.1">7.23.1</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
33198 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>
33199 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>
33200 numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> suffix
33201 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>
33202 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>
33203 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>
33204 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>
33205 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>
33206 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>
33207 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>,
33208 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>
33209 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>
33210 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>
33211 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>
33213 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>
33214 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>
33215 strspn function, <a href="#7.23.5.6">7.23.5.6</a> syntactic categories, <a href="#6.1">6.1</a>
33217 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>
33218 <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>
33219 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>
33221 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>
33222 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>
33223 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>
33224 <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>
33225 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>
33226 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>
33227 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>
33228 <!--page 693 -->
33229 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>
33230 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>
33231 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>
33232 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>
33233 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>
33234 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>
33235 tgamma type-generic macro, <a href="#7.24">7.24</a> translation phases, <a href="#5.1.1.2">5.1.1.2</a>
33236 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>
33237 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
33238 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>,
33239 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>
33241 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>
33242 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>
33243 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>
33245 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>
33246 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>
33247 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>
33248 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>
33249 threads header, <a href="#7.25">7.25</a> tss_create function, <a href="#7.25.6.1">7.25.6.1</a>
33250 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>
33252 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>
33253 <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>
33254 <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>
33255 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>
33256 <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>
33257 <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>
33258 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>
33259 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>
33260 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>
33262 manipulation functions, <a href="#7.26.2">7.26.2</a> type punning, <a href="#6.5.2.3">6.5.2.3</a>
33263 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>
33265 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>
33267 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>
33268 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>
33269 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>,
33270 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>
33271 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>
33272 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>
33273 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>
33275 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>
33276 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>
33278 token pasting, <a href="#6.10.3.3">6.10.3.3</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
33279 tolower function, <a href="#7.4.2.1">7.4.2.1</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
33280 <!--page 694 -->
33281 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>
33282 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>
33283 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>
33284 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>
33285 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
33288 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>
33289 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>
33290 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>
33291 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>,
33292 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>
33293 <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>,
33294 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>
33295 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>
33296 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>
33297 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>
33298 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>
33299 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>
33300 <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>,
33301 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>
33303 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>
33305 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>
33306 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>
33308 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>,
33309 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>,
33310 <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>,
33311 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>,
33312 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>,
33313 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>
33314 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>,
33315 <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>
33316 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>,
33317 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>,
33318 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>,
33319 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>,
33320 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>,
33321 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>
33322 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>
33323 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>,
33324 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>,
33325 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>,
33326 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>,
33327 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>,
33328 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>,
33329 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>
33330 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>
33331 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>
33332 <!--page 695 -->
33333 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>
33334 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>
33335 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>
33336 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>
33337 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>
33338 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>
33340 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>
33341 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>,
33342 <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>
33343 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>
33344 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>
33345 <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>,
33346 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>,
33347 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>
33348 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>,
33349 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>,
33351 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>
33352 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>
33354 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>
33355 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>
33356 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>
33358 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>
33359 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>
33360 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>
33361 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>
33362 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>
33363 <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>
33364 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>
33365 <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>
33366 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>
33367 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>
33369 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>
33370 <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>
33371 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>
33372 <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>
33373 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>
33374 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>
33376 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>
33377 <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>
33378 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>
33379 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>
33380 <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>,
33381 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>
33383 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>
33384 <!--page 696 -->
33385 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>
33386 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>
33387 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>
33389 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>
33390 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>
33391 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>
33392 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>
33393 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>,
33395 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>
33396 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>,
33397 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>
33398 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>
33401 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>
33402 <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>,
33403 <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>
33404 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>
33405 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>,
33424 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>
33425 wide string literal, see string literal
33430 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>
33435 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>,
33436 </pre>
33437 </body></html>