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6 </pre>
9 <ul>
17 <ul>
19 <ul>
22 </ul>
24 <ul>
29 </ul>
30 </ul>
32 <ul>
35 <ul>
43 </ul>
45 <ul>
48 </ul>
50 <ul>
60 </ul>
62 <!--page 2 -->
63 <ul>
81 </ul>
84 <ul>
93 </ul>
95 <ul>
102 </ul>
104 <ul>
107 </ul>
109 <ul>
116 <!--page 3 -->
120 </ul>
122 <ul>
132 </ul>
133 </ul>
135 <ul>
137 <ul>
142 </ul>
144 <ul>
146 </ul>
148 <ul>
158 </ul>
160 <ul>
163 </ul>
166 <ul>
171 </ul>
174 <ul>
177 <!--page 4 -->
178 </ul>
182 <ul>
185 </ul>
187 <ul>
202 </ul>
204 <ul>
207 </ul>
209 <ul>
212 </ul>
214 <ul>
216 </ul>
220 <ul>
225 </ul>
227 <ul>
236 <!--page 5 -->
239 </ul>
241 <ul>
250 </ul>
252 <ul>
259 </ul>
262 <ul>
266 </ul>
268 <ul>
275 </ul>
276 <li><a href="#7.25"> 7.25 Wide character classification and mapping utilities <wctype.h></a>
277 <ul>
281 </ul>
283 <ul>
293 <!--page 6 -->
297 <li><a href="#7.26.13"> 7.26.13 Wide character classification and mapping utilities <wctype.h></a>
298 </ul>
299 </ul>
301 <ul>
305 </ul>
307 <ul>
331 <li><a href="#B.24"> B.24 Wide character classification and mapping utilities <wctype.h></a>
332 </ul>
337 <ul>
341 <!--page 7 -->
348 </ul>
350 <ul>
358 </ul>
360 <ul>
364 </ul>
367 <ul>
373 </ul>
376 <!--page 8 -->
377 <!--page 9 -->
378 </ul>
382 ISO (the International Organization for Standardization) and IEC (the International
383 Electrotechnical Commission) form the specialized system for worldwide
384 standardization. National bodies that are member of ISO or IEC participate in the
385 development of International Standards through technical committees established by the
386 respective organization to deal with particular fields of technical activity. ISO and IEC
387 technical committees collaborate in fields of mutual interest. Other international
388 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
389 take part in the work.
391 International Standards are drafted in accordance with the rules given in the ISO/IEC
392 Directives, Part 3.
394 In the field of information technology, ISO and IEC have established a joint technical
395 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
396 committee are circulated to national bodies for voting. Publication as an International
397 Standard requires approval by at least 75% of the national bodies casting a vote.
399 International Standard ISO/IEC 9899 was prepared by Joint Technical Committee
401 their environments and system software interfaces. The Working Group responsible for
402 this standard (WG 14) maintains a site on the World Wide Web at
403 http://www.open-std.org/JTC1/SC22/WG14/ containing additional
404 information relevant to this standard such as a Rationale for many of the decisions made
405 during its preparation and a log of Defect Reports and Responses.
410 <ul>
411 <li> restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
412 in AMD1)
413 <li> wide character library support in <a href="#7.24"><wchar.h></a> and <a href="#7.25"><wctype.h></a> (originally
414 specified in AMD1)
415 <li> more precise aliasing rules via effective type
416 <li> restricted pointers
417 <li> variable length arrays
418 <li> flexible array members
419 <li> static and type qualifiers in parameter array declarators
422 <li> the long long int type and library functions
423 <!--page 10 -->
424 <li> increased minimum translation limits
426 <li> remove implicit int
427 <li> reliable integer division
428 <li> universal character names (\u and \U)
429 <li> extended identifiers
430 <li> hexadecimal floating-point constants and %a and %A printf/scanf conversion
431 specifiers
432 <li> compound literals
433 <li> designated initializers
434 <li> // comments
435 <li> extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.18"><stdint.h></a>
436 <li> remove implicit function declaration
437 <li> preprocessor arithmetic done in intmax_t/uintmax_t
438 <li> mixed declarations and code
439 <li> new block scopes for selection and iteration statements
440 <li> integer constant type rules
441 <li> integer promotion rules
442 <li> macros with a variable number of arguments
443 <li> the vscanf family of functions in <a href="#7.19"><stdio.h></a> and <a href="#7.24"><wchar.h></a>
445 <li> treatment of error conditions by math library functions (math_errhandling)
448 <li> trailing comma allowed in enum declaration
449 <li> %lf conversion specifier allowed in printf
450 <li> inline functions
453 <li> idempotent type qualifiers
454 <li> empty macro arguments
455 <!--page 11 -->
456 <li> new structure type compatibility rules (tag compatibility)
457 <li> additional predefined macro names
458 <li> _Pragma preprocessing operator
459 <li> standard pragmas
460 <li> __func__ predefined identifier
461 <li> va_copy macro
462 <li> additional strftime conversion specifiers
463 <li> LIA compatibility annex
464 <li> deprecate ungetc at the beginning of a binary file
465 <li> remove deprecation of aliased array parameters
466 <li> conversion of array to pointer not limited to lvalues
467 <li> relaxed constraints on aggregate and union initialization
468 <li> relaxed restrictions on portable header names
469 <li> return without expression not permitted in function that returns a value (and vice
470 versa)
471 </ul>
473 Annexes D and F form a normative part of this standard; annexes A, B, C, E, G, H, I, J,
474 the bibliography, and the index are for information only. In accordance with Part 3 of the
475 ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples are
476 also for information only.
477 <!--page 12 -->
481 With the introduction of new devices and extended character sets, new features may be
482 added to this International Standard. Subclauses in the language and library clauses warn
483 implementors and programmers of usages which, though valid in themselves, may
484 conflict with future additions.
486 Certain features are obsolescent, which means that they may be considered for
487 withdrawal in future revisions of this International Standard. They are retained because
488 of their widespread use, but their use in new implementations (for implementation
489 features) or new programs (for language [<a href="#6.11">6.11</a>] or library features [<a href="#7.26">7.26</a>]) is discouraged.
491 This International Standard is divided into four major subdivisions:
492 <ul>
497 </ul>
499 Examples are provided to illustrate possible forms of the constructions described.
500 Footnotes are provided to emphasize consequences of the rules described in that
501 subclause or elsewhere in this International Standard. References are used to refer to
502 other related subclauses. Recommendations are provided to give advice or guidance to
503 implementors. Annexes provide additional information and summarize the information
504 contained in this International Standard. A bibliography lists documents that were
505 referred to during the preparation of the standard.
507 The language clause (clause 6) is derived from ''The C Reference Manual''.
510 <!--page 13 -->
520 This International Standard specifies the form and establishes the interpretation of
521 programs written in the C programming language.<sup><a href="#note1"><b>1)</b></a></sup> It specifies
522 <ul>
523 <li> the representation of C programs;
524 <li> the syntax and constraints of the C language;
525 <li> the semantic rules for interpreting C programs;
526 <li> the representation of input data to be processed by C programs;
527 <li> the representation of output data produced by C programs;
528 <li> the restrictions and limits imposed by a conforming implementation of C.
529 </ul>
531 This International Standard does not specify
532 <ul>
533 <li> the mechanism by which C programs are transformed for use by a data-processing
534 system;
535 <li> the mechanism by which C programs are invoked for use by a data-processing
536 system;
537 <li> the mechanism by which input data are transformed for use by a C program;
538 <li> the mechanism by which output data are transformed after being produced by a C
539 program;
540 <li> the size or complexity of a program and its data that will exceed the capacity of any
541 specific data-processing system or the capacity of a particular processor;
544 <!--page 14 -->
545 <li> all minimal requirements of a data-processing system that is capable of supporting a
546 conforming implementation.
548 </ul>
551 <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
552 data-processing systems. It is intended for use by implementors and programmers.
553 </small>
557 The following normative documents contain provisions which, through reference in this
558 text, constitute provisions of this International Standard. For dated references,
559 subsequent amendments to, or revisions of, any of these publications do not apply.
560 However, parties to agreements based on this International Standard are encouraged to
561 investigate the possibility of applying the most recent editions of the normative
562 documents indicated below. For undated references, the latest edition of the normative
563 document referred to applies. Members of ISO and IEC maintain registers of currently
564 valid International Standards.
567 use in the physical sciences and technology.
570 interchange.
573 terms.
575 ISO 4217, Codes for the representation of currencies and funds.
577 ISO 8601, Data elements and interchange formats -- Information interchange --
578 Representation of dates and times.
580 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
581 Character Set (UCS).
585 <!--page 15 -->
589 For the purposes of this International Standard, the following definitions apply. Other
590 terms are defined where they appear in italic type or on the left side of a syntax rule.
591 Terms explicitly defined in this International Standard are not to be presumed to refer
592 implicitly to similar terms defined elsewhere. Terms not defined in this International
601 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
604 NOTE 2 "Modify'' includes the case where the new value being stored is the same as the previous value.
606 <p><!--para 4 -->
607 NOTE 3 Expressions that are not evaluated do not access objects.
611 <p><!--para 1 -->
612 <b> alignment</b><br>
613 requirement that objects of a particular type be located on storage boundaries with
614 addresses that are particular multiples of a byte address
617 <p><!--para 1 -->
618 <b> argument</b><br>
619 actual argument<br>
620 actual parameter (deprecated)<br>
621 expression in the comma-separated list bounded by the parentheses in a function call
622 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
623 by the parentheses in a function-like macro invocation
626 <p><!--para 1 -->
627 <b> behavior</b><br>
628 external appearance or action
631 <p><!--para 1 -->
632 <b> implementation-defined behavior</b><br>
633 unspecified behavior where each implementation documents how the choice is made
634 <p><!--para 2 -->
635 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
636 when a signed integer is shifted right.
640 <p><!--para 1 -->
641 <b> locale-specific behavior</b><br>
642 behavior that depends on local conventions of nationality, culture, and language that each
643 implementation documents
644 <!--page 16 -->
645 <p><!--para 2 -->
646 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
647 characters other than the 26 lowercase Latin letters.
651 <p><!--para 1 -->
652 <b> undefined behavior</b><br>
653 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
654 for which this International Standard imposes no requirements
655 <p><!--para 2 -->
656 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
657 results, to behaving during translation or program execution in a documented manner characteristic of the
658 environment (with or without the issuance of a diagnostic message), to terminating a translation or
659 execution (with the issuance of a diagnostic message).
661 <p><!--para 3 -->
662 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
666 <p><!--para 1 -->
667 <b> unspecified behavior</b><br>
668 use of an unspecified value, or other behavior where this International Standard provides
669 two or more possibilities and imposes no further requirements on which is chosen in any
670 instance
671 <p><!--para 2 -->
672 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
673 evaluated.
677 <p><!--para 1 -->
678 <b> bit</b><br>
679 unit of data storage in the execution environment large enough to hold an object that may
680 have one of two values
681 <p><!--para 2 -->
682 NOTE It need not be possible to express the address of each individual bit of an object.
686 <p><!--para 1 -->
687 <b> byte</b><br>
688 addressable unit of data storage large enough to hold any member of the basic character
689 set of the execution environment
690 <p><!--para 2 -->
691 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
693 <p><!--para 3 -->
694 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
695 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
696 bit.
700 <p><!--para 1 -->
701 <b> character</b><br>
702 <abstract> member of a set of elements used for the organization, control, or
703 representation of data
706 <p><!--para 1 -->
707 <b> character</b><br>
708 single-byte character
709 <C> bit representation that fits in a byte
710 <!--page 17 -->
713 <p><!--para 1 -->
714 <b> multibyte character</b><br>
715 sequence of one or more bytes representing a member of the extended character set of
716 either the source or the execution environment
717 <p><!--para 2 -->
718 NOTE The extended character set is a superset of the basic character set.
722 <p><!--para 1 -->
723 <b> wide character</b><br>
724 bit representation that fits in an object of type wchar_t, capable of representing any
725 character in the current locale
728 <p><!--para 1 -->
729 <b> constraint</b><br>
730 restriction, either syntactic or semantic, by which the exposition of language elements is
731 to be interpreted
734 <p><!--para 1 -->
735 <b> correctly rounded result</b><br>
736 representation in the result format that is nearest in value, subject to the current rounding
737 mode, to what the result would be given unlimited range and precision
740 <p><!--para 1 -->
741 <b> diagnostic message</b><br>
742 message belonging to an implementation-defined subset of the implementation's message
743 output
746 <p><!--para 1 -->
747 <b> forward reference</b><br>
748 reference to a later subclause of this International Standard that contains additional
749 information relevant to this subclause
752 <p><!--para 1 -->
753 <b> implementation</b><br>
754 particular set of software, running in a particular translation environment under particular
755 control options, that performs translation of programs for, and supports execution of
756 functions in, a particular execution environment
759 <p><!--para 1 -->
760 <b> implementation limit</b><br>
761 restriction imposed upon programs by the implementation
764 <p><!--para 1 -->
765 <b> object</b><br>
766 region of data storage in the execution environment, the contents of which can represent
767 values
768 <!--page 18 -->
769 <p><!--para 2 -->
770 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>.
774 <p><!--para 1 -->
775 <b> parameter</b><br>
776 formal parameter
777 formal argument (deprecated)
778 object declared as part of a function declaration or definition that acquires a value on
779 entry to the function, or an identifier from the comma-separated list bounded by the
780 parentheses immediately following the macro name in a function-like macro definition
783 <p><!--para 1 -->
784 <b> recommended practice</b><br>
785 specification that is strongly recommended as being in keeping with the intent of the
786 standard, but that may be impractical for some implementations
789 <p><!--para 1 -->
790 <b> value</b><br>
791 precise meaning of the contents of an object when interpreted as having a specific type
794 <p><!--para 1 -->
795 <b> implementation-defined value</b><br>
796 unspecified value where each implementation documents how the choice is made
799 <p><!--para 1 -->
800 <b> indeterminate value</b><br>
801 either an unspecified value or a trap representation
804 <p><!--para 1 -->
805 <b> unspecified value</b><br>
806 valid value of the relevant type where this International Standard imposes no
807 requirements on which value is chosen in any instance
808 <p><!--para 2 -->
809 NOTE An unspecified value cannot be a trap representation.
813 <p><!--para 1 -->
814 <b> [^ x ^]</b><br>
815 ceiling of x: the least integer greater than or equal to x
816 <p><!--para 2 -->
817 EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
821 <p><!--para 1 -->
822 <b> [_ x _]</b><br>
823 floor of x: the greatest integer less than or equal to x
824 <p><!--para 2 -->
825 EXAMPLE [_2.4_] is 2, [_-2.4_] is -3.
826 <!--page 19 -->
829 <p><!--para 1 -->
830 In this International Standard, ''shall'' is to be interpreted as a requirement on an
831 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
832 prohibition.
833 <p><!--para 2 -->
834 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated, the
835 behavior is undefined. Undefined behavior is otherwise indicated in this International
836 Standard by the words ''undefined behavior'' or by the omission of any explicit definition
837 of behavior. There is no difference in emphasis among these three; they all describe
838 ''behavior that is undefined''.
839 <p><!--para 3 -->
840 A program that is correct in all other aspects, operating on correct data, containing
841 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
842 <p><!--para 4 -->
843 The implementation shall not successfully translate a preprocessing translation unit
844 containing a #error preprocessing directive unless it is part of a group skipped by
845 conditional inclusion.
846 <p><!--para 5 -->
847 A strictly conforming program shall use only those features of the language and library
848 specified in this International Standard.<sup><a href="#note2"><b>2)</b></a></sup> It shall not produce output dependent on any
849 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
850 minimum implementation limit.
851 <p><!--para 6 -->
852 The two forms of conforming implementation are hosted and freestanding. A conforming
853 hosted implementation shall accept any strictly conforming program. A conforming
854 freestanding implementation shall accept any strictly conforming program that does not
855 use complex types and in which the use of the features specified in the library clause
856 (clause 7) is confined to the contents of the standard headers <a href="#7.7"><float.h></a>,
857 <a href="#7.9"><iso646.h></a>, <a href="#7.10"><limits.h></a>, <a href="#7.15"><stdarg.h></a>, <a href="#7.16"><stdbool.h></a>, <a href="#7.17"><stddef.h></a>, and
858 <a href="#7.18"><stdint.h></a>. A conforming implementation may have extensions (including additional
859 library functions), provided they do not alter the behavior of any strictly conforming
864 <!--page 20 -->
865 <p><!--para 7 -->
866 A conforming program is one that is acceptable to a conforming implementation.<sup><a href="#note4"><b>4)</b></a></sup>
867 <p><!--para 8 -->
868 An implementation shall be accompanied by a document that defines all implementation-
869 defined and locale-specific characteristics and all extensions.
870 <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>),
871 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>
872 (<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>), variable arguments <a href="#7.15"><stdarg.h></a>
873 (<a href="#7.15">7.15</a>), boolean type and values <a href="#7.16"><stdbool.h></a> (<a href="#7.16">7.16</a>), common definitions
874 <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>).
879 <!--page 21 -->
881 <p><b>Footnotes</b>
882 <p><small><a name="note2" href="#note2">2)</a> A strictly conforming program can use conditional features (such as those in <a href="#F">annex F</a>) provided the
883 use is guarded by a #ifdef directive with the appropriate macro. For example:
885 <pre>
886 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
887 /* ... */
888 fesetround(FE_UPWARD);
889 /* ... */
890 #endif
891 </pre>
893 </small>
894 <p><small><a name="note3" href="#note3">3)</a> This implies that a conforming implementation reserves no identifiers other than those explicitly
895 reserved in this International Standard.
896 </small>
897 <p><small><a name="note4" href="#note4">4)</a> Strictly conforming programs are intended to be maximally portable among conforming
898 implementations. Conforming programs may depend upon nonportable features of a conforming
899 implementation.
900 </small>
903 <p><!--para 1 -->
904 An implementation translates C source files and executes C programs in two data-
905 processing-system environments, which will be called the translation environment and
906 the execution environment in this International Standard. Their characteristics define and
907 constrain the results of executing conforming C programs constructed according to the
908 syntactic and semantic rules for conforming implementations.
909 <p><b> Forward references</b>: In this clause, only a few of many possible forward references
910 have been noted.
917 <p><!--para 1 -->
918 A C program need not all be translated at the same time. The text of the program is kept
919 in units called source files, (or preprocessing files) in this International Standard. A
920 source file together with all the headers and source files included via the preprocessing
921 directive #include is known as a preprocessing translation unit. After preprocessing, a
922 preprocessing translation unit is called a translation unit. Previously translated translation
923 units may be preserved individually or in libraries. The separate translation units of a
924 program communicate by (for example) calls to functions whose identifiers have external
925 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
926 of data files. Translation units may be separately translated and then later linked to
927 produce an executable program.
928 <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>),
932 <p><!--para 1 -->
933 The precedence among the syntax rules of translation is specified by the following
935 <ol>
936 <li> Physical source file multibyte characters are mapped, in an implementation-
937 defined manner, to the source character set (introducing new-line characters for
938 end-of-line indicators) if necessary. Trigraph sequences are replaced by
939 corresponding single-character internal representations.
943 <!--page 22 -->
944 <li> Each instance of a backslash character (\) immediately followed by a new-line
945 character is deleted, splicing physical source lines to form logical source lines.
946 Only the last backslash on any physical source line shall be eligible for being part
947 of such a splice. A source file that is not empty shall end in a new-line character,
948 which shall not be immediately preceded by a backslash character before any such
949 splicing takes place.
950 <li> The source file is decomposed into preprocessing tokens<sup><a href="#note6"><b>6)</b></a></sup> and sequences of
951 white-space characters (including comments). A source file shall not end in a
952 partial preprocessing token or in a partial comment. Each comment is replaced by
953 one space character. New-line characters are retained. Whether each nonempty
954 sequence of white-space characters other than new-line is retained or replaced by
955 one space character is implementation-defined.
956 <li> Preprocessing directives are executed, macro invocations are expanded, and
957 _Pragma unary operator expressions are executed. If a character sequence that
958 matches the syntax of a universal character name is produced by token
959 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
960 directive causes the named header or source file to be processed from phase 1
961 through phase 4, recursively. All preprocessing directives are then deleted.
962 <li> Each source character set member and escape sequence in character constants and
963 string literals is converted to the corresponding member of the execution character
964 set; if there is no corresponding member, it is converted to an implementation-
966 <li> Adjacent string literal tokens are concatenated.
967 <li> White-space characters separating tokens are no longer significant. Each
968 preprocessing token is converted into a token. The resulting tokens are
969 syntactically and semantically analyzed and translated as a translation unit.
970 <li> All external object and function references are resolved. Library components are
971 linked to satisfy external references to functions and objects not defined in the
972 current translation. All such translator output is collected into a program image
973 which contains information needed for execution in its execution environment.
974 </ol>
975 <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>),
976 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>).
980 <!--page 23 -->
982 <p><b>Footnotes</b>
983 <p><small><a name="note5" href="#note5">5)</a> Implementations shall behave as if these separate phases occur, even though many are typically folded
984 together in practice. Source files, translation units, and translated translation units need not
985 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
986 and any external representation. The description is conceptual only, and does not specify any
987 particular implementation.
988 </small>
989 <p><small><a name="note6" href="#note6">6)</a> As described in <a href="#6.4">6.4</a>, the process of dividing a source file's characters into preprocessing tokens is
990 context-dependent. For example, see the handling of < within a #include preprocessing directive.
991 </small>
992 <p><small><a name="note7" href="#note7">7)</a> An implementation need not convert all non-corresponding source characters to the same execution
993 character.
994 </small>
997 <p><!--para 1 -->
998 A conforming implementation shall produce at least one diagnostic message (identified in
999 an implementation-defined manner) if a preprocessing translation unit or translation unit
1000 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1001 specified as undefined or implementation-defined. Diagnostic messages need not be
1003 <p><!--para 2 -->
1004 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1005 <pre>
1006 char i;
1007 int i;
1008 </pre>
1009 because in those cases where wording in this International Standard describes the behavior for a construct
1010 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1013 <p><b>Footnotes</b>
1014 <p><small><a name="note8" href="#note8">8)</a> The intent is that an implementation should identify the nature of, and where possible localize, each
1015 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1016 valid program is still correctly translated. It may also successfully translate an invalid program.
1017 </small>
1020 <p><!--para 1 -->
1021 Two execution environments are defined: freestanding and hosted. In both cases,
1022 program startup occurs when a designated C function is called by the execution
1023 environment. All objects with static storage duration shall be initialized (set to their
1024 initial values) before program startup. The manner and timing of such initialization are
1025 otherwise unspecified. Program termination returns control to the execution
1026 environment.
1027 <p><b> Forward references</b>: storage durations of objects (<a href="#6.2.4">6.2.4</a>), initialization (<a href="#6.7.8">6.7.8</a>).
1030 <p><!--para 1 -->
1031 In a freestanding environment (in which C program execution may take place without any
1032 benefit of an operating system), the name and type of the function called at program
1033 startup are implementation-defined. Any library facilities available to a freestanding
1034 program, other than the minimal set required by clause 4, are implementation-defined.
1035 <p><!--para 2 -->
1036 The effect of program termination in a freestanding environment is implementation-
1037 defined.
1040 <p><!--para 1 -->
1041 A hosted environment need not be provided, but shall conform to the following
1042 specifications if present.
1047 <!--page 24 -->
1050 <p><!--para 1 -->
1051 The function called at program startup is named main. The implementation declares no
1052 prototype for this function. It shall be defined with a return type of int and with no
1053 parameters:
1054 <pre>
1055 int main(void) { /* ... */ }
1056 </pre>
1057 or with two parameters (referred to here as argc and argv, though any names may be
1058 used, as they are local to the function in which they are declared):
1059 <pre>
1060 int main(int argc, char *argv[]) { /* ... */ }
1061 </pre>
1062 or equivalent;<sup><a href="#note9"><b>9)</b></a></sup> or in some other implementation-defined manner.
1063 <p><!--para 2 -->
1064 If they are declared, the parameters to the main function shall obey the following
1065 constraints:
1066 <ul>
1067 <li> The value of argc shall be nonnegative.
1068 <li> argv[argc] shall be a null pointer.
1069 <li> If the value of argc is greater than zero, the array members argv[0] through
1070 argv[argc-1] inclusive shall contain pointers to strings, which are given
1071 implementation-defined values by the host environment prior to program startup. The
1072 intent is to supply to the program information determined prior to program startup
1073 from elsewhere in the hosted environment. If the host environment is not capable of
1074 supplying strings with letters in both uppercase and lowercase, the implementation
1075 shall ensure that the strings are received in lowercase.
1076 <li> If the value of argc is greater than zero, the string pointed to by argv[0]
1077 represents the program name; argv[0][0] shall be the null character if the
1078 program name is not available from the host environment. If the value of argc is
1079 greater than one, the strings pointed to by argv[1] through argv[argc-1]
1080 represent the program parameters.
1081 <li> The parameters argc and argv and the strings pointed to by the argv array shall
1082 be modifiable by the program, and retain their last-stored values between program
1083 startup and program termination.
1084 </ul>
1086 <p><b>Footnotes</b>
1087 <p><small><a name="note9" href="#note9">9)</a> Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as
1088 char ** argv, and so on.
1089 </small>
1092 <p><!--para 1 -->
1093 In a hosted environment, a program may use all the functions, macros, type definitions,
1094 and objects described in the library clause (clause 7).
1098 <!--page 25 -->
1101 <p><!--para 1 -->
1102 If the return type of the main function is a type compatible with int, a return from the
1103 initial call to the main function is equivalent to calling the exit function with the value
1104 returned by the main function as its argument;<sup><a href="#note10"><b>10)</b></a></sup> reaching the } that terminates the
1105 main function returns a value of 0. If the return type is not compatible with int, the
1106 termination status returned to the host environment is unspecified.
1107 <p><b> Forward references</b>: definition of terms (<a href="#7.1.1">7.1.1</a>), the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
1109 <p><b>Footnotes</b>
1110 <p><small><a name="note10" href="#note10">10)</a> In accordance with <a href="#6.2.4">6.2.4</a>, the lifetimes of objects with automatic storage duration declared in main
1111 will have ended in the former case, even where they would not have in the latter.
1112 </small>
1115 <p><!--para 1 -->
1116 The semantic descriptions in this International Standard describe the behavior of an
1117 abstract machine in which issues of optimization are irrelevant.
1118 <p><!--para 2 -->
1119 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1120 that does any of those operations are all side effects,<sup><a href="#note11"><b>11)</b></a></sup> which are changes in the state of
1121 the execution environment. Evaluation of an expression may produce side effects. At
1122 certain specified points in the execution sequence called sequence points, all side effects
1123 of previous evaluations shall be complete and no side effects of subsequent evaluations
1124 shall have taken place. (A summary of the sequence points is given in <a href="#C">annex C</a>.)
1125 <p><!--para 3 -->
1126 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1127 actual implementation need not evaluate part of an expression if it can deduce that its
1128 value is not used and that no needed side effects are produced (including any caused by
1129 calling a function or accessing a volatile object).
1130 <p><!--para 4 -->
1131 When the processing of the abstract machine is interrupted by receipt of a signal, only the
1132 values of objects as of the previous sequence point may be relied on. Objects that may be
1133 modified between the previous sequence point and the next sequence point need not have
1134 received their correct values yet.
1135 <p><!--para 5 -->
1136 The least requirements on a conforming implementation are:
1137 <ul>
1138 <li> At sequence points, volatile objects are stable in the sense that previous accesses are
1139 complete and subsequent accesses have not yet occurred.
1144 <!--page 26 -->
1145 <li> At program termination, all data written into files shall be identical to the result that
1146 execution of the program according to the abstract semantics would have produced.
1147 <li> The input and output dynamics of interactive devices shall take place as specified in
1148 <a href="#7.19.3">7.19.3</a>. The intent of these requirements is that unbuffered or line-buffered output
1149 appear as soon as possible, to ensure that prompting messages actually appear prior to
1150 a program waiting for input.
1151 </ul>
1152 <p><!--para 6 -->
1153 What constitutes an interactive device is implementation-defined.
1154 <p><!--para 7 -->
1155 More stringent correspondences between abstract and actual semantics may be defined by
1156 each implementation.
1157 <p><!--para 8 -->
1158 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1159 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1160 abstract semantics. The keyword volatile would then be redundant.
1161 <p><!--para 9 -->
1162 Alternatively, an implementation might perform various optimizations within each translation unit, such
1163 that the actual semantics would agree with the abstract semantics only when making function calls across
1164 translation unit boundaries. In such an implementation, at the time of each function entry and function
1165 return where the calling function and the called function are in different translation units, the values of all
1166 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1167 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1168 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1169 type of implementation, objects referred to by interrupt service routines activated by the signal function
1170 would require explicit specification of volatile storage, as well as other implementation-defined
1171 restrictions.
1173 <p><!--para 10 -->
1174 EXAMPLE 2 In executing the fragment
1175 <pre>
1176 char c1, c2;
1177 /* ... */
1178 c1 = c1 + c2;
1179 </pre>
1180 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1181 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1182 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1183 produce the same result, possibly omitting the promotions.
1185 <p><!--para 11 -->
1186 EXAMPLE 3 Similarly, in the fragment
1187 <pre>
1188 float f1, f2;
1189 double d;
1190 /* ... */
1191 f1 = f2 * d;
1192 </pre>
1193 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1194 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1195 were replaced by the constant 2.0, which has type double).
1196 <!--page 27 -->
1197 <p><!--para 12 -->
1198 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1199 semantics. Values are independent of whether they are represented in a register or in memory. For
1200 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1201 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1202 perform their specified conversion. For the fragment
1203 <pre>
1204 double d1, d2;
1205 float f;
1206 d1 = f = expression;
1207 d2 = (float) expression;
1208 </pre>
1209 the values assigned to d1 and d2 are required to have been converted to float.
1211 <p><!--para 13 -->
1212 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1213 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1214 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1215 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1216 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1218 <pre>
1219 double x, y, z;
1220 /* ... */
1221 x = (x * y) * z; // not equivalent to x *= y * z;
1222 z = (x - y) + y ; // not equivalent to z = x;
1223 z = x + x * y; // not equivalent to z = x * (1.0 + y);
1224 y = x / 5.0; // not equivalent to y = x * 0.2;
1225 </pre>
1227 <p><!--para 14 -->
1228 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1229 <pre>
1230 int a, b;
1231 /* ... */
1232 a = a + 32760 + b + 5;
1233 </pre>
1234 the expression statement behaves exactly the same as
1235 <pre>
1236 a = (((a + 32760) + b) + 5);
1237 </pre>
1238 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1239 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1240 which overflows produce an explicit trap and in which the range of values representable by an int is
1241 [-32768, +32767], the implementation cannot rewrite this expression as
1242 <pre>
1243 a = ((a + b) + 32765);
1244 </pre>
1245 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1246 while the original expression would not; nor can the expression be rewritten either as
1247 <pre>
1248 a = ((a + 32765) + b);
1249 </pre>
1250 or
1251 <pre>
1252 a = (a + (b + 32765));
1253 </pre>
1254 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1255 in which overflow silently generates some value and where positive and negative overflows cancel, the
1256 above expression statement can be rewritten by the implementation in any of the above ways because the
1257 same result will occur.
1258 <!--page 28 -->
1259 <p><!--para 15 -->
1260 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1261 following fragment
1262 <pre>
1264 int sum;
1265 char *p;
1266 /* ... */
1267 sum = sum * 10 - '0' + (*p++ = getchar());
1268 </pre>
1269 the expression statement is grouped as if it were written as
1270 <pre>
1271 sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));
1272 </pre>
1273 but the actual increment of p can occur at any time between the previous sequence point and the next
1274 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1275 value.
1277 <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
1279 <!--page 29 -->
1281 <p><b>Footnotes</b>
1282 <p><small><a name="note11" href="#note11">11)</a> The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
1283 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1284 values of floating-point operations. Implementations that support such floating-point state are
1285 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1286 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1287 effects matter, freeing the implementations in other cases.
1288 </small>
1293 <p><!--para 1 -->
1294 Two sets of characters and their associated collating sequences shall be defined: the set in
1295 which source files are written (the source character set), and the set interpreted in the
1296 execution environment (the execution character set). Each set is further divided into a
1297 basic character set, whose contents are given by this subclause, and a set of zero or more
1298 locale-specific members (which are not members of the basic character set) called
1299 extended characters. The combined set is also called the extended character set. The
1300 values of the members of the execution character set are implementation-defined.
1301 <p><!--para 2 -->
1302 In a character constant or string literal, members of the execution character set shall be
1303 represented by corresponding members of the source character set or by escape
1304 sequences consisting of the backslash \ followed by one or more characters. A byte with
1305 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1306 is used to terminate a character string.
1307 <p><!--para 3 -->
1308 Both the basic source and basic execution character sets shall have the following
1309 members: the 26 uppercase letters of the Latin alphabet
1310 <pre>
1311 A B C D E F G H I J K L M
1312 N O P Q R S T U V W X Y Z
1313 </pre>
1314 the 26 lowercase letters of the Latin alphabet
1315 <pre>
1316 a b c d e f g h i j k l m
1317 n o p q r s t u v w x y z
1318 </pre>
1319 the 10 decimal digits
1320 <pre>
1321 0 1 2 3 4 5 6 7 8 9
1322 </pre>
1323 the following 29 graphic characters
1324 <pre>
1327 </pre>
1328 the space character, and control characters representing horizontal tab, vertical tab, and
1329 form feed. The representation of each member of the source and execution basic
1330 character sets shall fit in a byte. In both the source and execution basic character sets, the
1331 value of each character after 0 in the above list of decimal digits shall be one greater than
1332 the value of the previous. In source files, there shall be some way of indicating the end of
1333 each line of text; this International Standard treats such an end-of-line indicator as if it
1334 were a single new-line character. In the basic execution character set, there shall be
1335 control characters representing alert, backspace, carriage return, and new line. If any
1336 other characters are encountered in a source file (except in an identifier, a character
1337 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1338 <!--page 30 -->
1339 converted to a token), the behavior is undefined.
1341 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1342 Standard the term does not include other characters that are letters in other alphabets.
1344 The universal character name construct provides a way to name other characters.
1345 <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>),
1346 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>).
1350 Before any other processing takes place, each occurrence of one of the following
1351 sequences of three characters (called trigraph sequences<sup><a href="#note12"><b>12)</b></a></sup>) is replaced with the
1352 corresponding single character.
1353 <pre>
1354 ??= # ??) ] ??! |
1355 ??( [ ??' ^ ??> }
1356 ??/ \ ??< { ??- ~
1357 </pre>
1358 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1359 above is not changed.
1361 EXAMPLE 1
1362 <pre>
1363 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
1364 </pre>
1365 becomes
1366 <pre>
1367 #define arraycheck(a, b) a[b] || b[a]
1368 </pre>
1371 EXAMPLE 2 The following source line
1372 <pre>
1373 printf("Eh???/n");
1374 </pre>
1375 becomes (after replacement of the trigraph sequence ??/)
1376 <pre>
1377 printf("Eh?\n");
1378 </pre>
1382 <p><small><a name="note12" href="#note12">12)</a> The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
1383 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1384 </small>
1388 The source character set may contain multibyte characters, used to represent members of
1389 the extended character set. The execution character set may also contain multibyte
1390 characters, which need not have the same encoding as for the source character set. For
1391 both character sets, the following shall hold:
1392 <ul>
1393 <li> The basic character set shall be present and each character shall be encoded as a
1394 single byte.
1395 <li> The presence, meaning, and representation of any additional members is locale-
1396 specific.
1398 <!--page 31 -->
1399 <li> A multibyte character set may have a state-dependent encoding, wherein each
1400 sequence of multibyte characters begins in an initial shift state and enters other
1401 locale-specific shift states when specific multibyte characters are encountered in the
1402 sequence. While in the initial shift state, all single-byte characters retain their usual
1403 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1404 in the sequence is a function of the current shift state.
1405 <li> A byte with all bits zero shall be interpreted as a null character independent of shift
1406 state. Such a byte shall not occur as part of any other multibyte character.
1407 </ul>
1409 For source files, the following shall hold:
1410 <ul>
1411 <li> An identifier, comment, string literal, character constant, or header name shall begin
1412 and end in the initial shift state.
1413 <li> An identifier, comment, string literal, character constant, or header name shall consist
1414 of a sequence of valid multibyte characters.
1415 </ul>
1419 The active position is that location on a display device where the next character output by
1420 the fputc function would appear. The intent of writing a printing character (as defined
1421 by the isprint function) to a display device is to display a graphic representation of
1422 that character at the active position and then advance the active position to the next
1423 position on the current line. The direction of writing is locale-specific. If the active
1424 position is at the final position of a line (if there is one), the behavior of the display device
1425 is unspecified.
1427 Alphabetic escape sequences representing nongraphic characters in the execution
1428 character set are intended to produce actions on display devices as follows:
1429 <dl>
1431 <dt> \b <dd>(backspace) Moves the active position to the previous position on the current line. If
1432 the active position is at the initial position of a line, the behavior of the display
1433 device is unspecified.
1434 <dt> \f <dd>( form feed) Moves the active position to the initial position at the start of the next
1435 logical page.
1437 <dt> \r <dd>(carriage return) Moves the active position to the initial position of the current line.
1438 <dt> \t <dd>(horizontal tab) Moves the active position to the next horizontal tabulation position
1439 on the current line. If the active position is at or past the last defined horizontal
1440 tabulation position, the behavior of the display device is unspecified.
1441 <dt> \v <dd>(vertical tab) Moves the active position to the initial position of the next vertical
1442 <!--page 32 -->
1443 tabulation position. If the active position is at or past the last defined vertical
1444 tabulation position, the behavior of the display device is unspecified.
1445 </dl>
1447 Each of these escape sequences shall produce a unique implementation-defined value
1448 which can be stored in a single char object. The external representations in a text file
1449 need not be identical to the internal representations, and are outside the scope of this
1450 International Standard.
1451 <p><b> Forward references</b>: the isprint function (<a href="#7.4.1.8">7.4.1.8</a>), the fputc function (<a href="#7.19.7.3">7.19.7.3</a>).
1455 Functions shall be implemented such that they may be interrupted at any time by a signal,
1456 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
1457 invocations' control flow (after the interruption), function return values, or objects with
1458 automatic storage duration. All such objects shall be maintained outside the function
1459 image (the instructions that compose the executable representation of a function) on a
1460 per-invocation basis.
1464 Both the translation and execution environments constrain the implementation of
1465 language translators and libraries. The following summarizes the language-related
1466 environmental limits on a conforming implementation; the library-related limits are
1467 discussed in clause 7.
1471 The implementation shall be able to translate and execute at least one program that
1472 contains at least one instance of every one of the following limits:<sup><a href="#note13"><b>13)</b></a></sup>
1473 <ul>
1477 arithmetic, structure, union, or incomplete type in a declaration
1481 universal character name or extended source character is considered a single
1482 character)
1483 <li> 31 significant initial characters in an external identifier (each universal character name
1487 <!--page 33 -->
1488 universal character name specifying a short identifier of 00010000 or more is
1489 considered 10 characters, and each extended source character is considered the same
1490 number of characters as the corresponding universal character name, if any)<sup><a href="#note14"><b>14)</b></a></sup>
1499 <li> 4095 characters in a character string literal or wide string literal (after concatenation)
1503 statements)
1507 </ul>
1510 <p><small><a name="note13" href="#note13">13)</a> Implementations should avoid imposing fixed translation limits whenever possible.
1511 </small>
1512 <p><small><a name="note14" href="#note14">14)</a> See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
1513 </small>
1517 An implementation is required to document all the limits specified in this subclause,
1518 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
1520 <p><b> Forward references</b>: integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>).
1524 The values given below shall be replaced by constant expressions suitable for use in #if
1525 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
1526 following shall be replaced by expressions that have the same type as would an
1527 expression that is an object of the corresponding type converted according to the integer
1528 promotions. Their implementation-defined values shall be equal or greater in magnitude
1531 <!--page 34 -->
1532 (absolute value) to those shown, with the same sign.
1533 <ul>
1534 <li> number of bits for smallest object that is not a bit-field (byte)
1535 <pre>
1536 CHAR_BIT 8
1537 </pre>
1538 <li> minimum value for an object of type signed char
1539 <pre>
1541 </pre>
1542 <li> maximum value for an object of type signed char
1543 <pre>
1545 </pre>
1546 <li> maximum value for an object of type unsigned char
1547 <pre>
1549 </pre>
1550 <li> minimum value for an object of type char
1551 <pre>
1552 CHAR_MIN see below
1553 </pre>
1554 <li> maximum value for an object of type char
1555 <pre>
1556 CHAR_MAX see below
1557 </pre>
1558 <li> maximum number of bytes in a multibyte character, for any supported locale
1559 <pre>
1560 MB_LEN_MAX 1
1561 </pre>
1562 <li> minimum value for an object of type short int
1563 <pre>
1565 </pre>
1566 <li> maximum value for an object of type short int
1567 <pre>
1569 </pre>
1570 <li> maximum value for an object of type unsigned short int
1571 <pre>
1573 </pre>
1574 <li> minimum value for an object of type int
1575 <pre>
1577 </pre>
1578 <li> maximum value for an object of type int
1579 <pre>
1581 </pre>
1582 <li> maximum value for an object of type unsigned int
1583 <pre>
1585 </pre>
1586 <li> minimum value for an object of type long int
1587 <pre>
1589 </pre>
1590 <li> maximum value for an object of type long int
1591 <pre>
1593 </pre>
1594 <li> maximum value for an object of type unsigned long int
1595 <pre>
1597 </pre>
1598 <!--page 35 -->
1599 <li> minimum value for an object of type long long int
1600 <pre>
1602 </pre>
1603 <li> maximum value for an object of type long long int
1604 <pre>
1606 </pre>
1607 <li> maximum value for an object of type unsigned long long int
1608 <pre>
1610 </pre>
1611 </ul>
1613 If the value of an object of type char is treated as a signed integer when used in an
1614 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
1615 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
1616 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
1617 UCHAR_MAX.<sup><a href="#note15"><b>15)</b></a></sup> The value UCHAR_MAX shall equal 2<sup>CHAR_BIT</sup> - 1.
1618 <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>).
1622 </small>
1624 <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>
1626 The characteristics of floating types are defined in terms of a model that describes a
1627 representation of floating-point numbers and values that provide information about an
1628 implementation's floating-point arithmetic.<sup><a href="#note16"><b>16)</b></a></sup> The following parameters are used to
1629 define the model for each floating-point type:
1630 <pre>
1631 s sign ((+-)1)
1633 e exponent (an integer between a minimum emin and a maximum emax )
1634 p precision (the number of base-b digits in the significand)
1636 </pre>
1638 A floating-point number (x) is defined by the following model:
1639 <pre>
1640 p
1642 k=1
1643 </pre>
1646 In addition to normalized floating-point numbers ( f<sub>1</sub> > 0 if x != 0), floating types may be
1647 able to contain other kinds of floating-point numbers, such as subnormal floating-point
1648 numbers (x != 0, e = emin , f<sub>1</sub> = 0) and unnormalized floating-point numbers (x != 0,
1649 e > emin , f<sub>1</sub> = 0), and values that are not floating-point numbers, such as infinities and
1650 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
1651 through almost every arithmetic operation without raising a floating-point exception; a
1652 signaling NaN generally raises a floating-point exception when occurring as an
1655 <!--page 36 -->
1658 An implementation may give zero and non-numeric values (such as infinities and NaNs) a
1659 sign or may leave them unsigned. Wherever such values are unsigned, any requirement
1660 in this International Standard to retrieve the sign shall produce an unspecified sign, and
1661 any requirement to set the sign shall be ignored.
1663 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
1664 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
1665 defined, as is the accuracy of the conversion between floating-point internal
1666 representations and string representations performed by the library functions in
1667 <a href="#7.19"><stdio.h></a>, <a href="#7.20"><stdlib.h></a>, and <a href="#7.24"><wchar.h></a>. The implementation may state that the
1668 accuracy is unknown.
1670 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
1671 expressions suitable for use in #if preprocessing directives; all floating values shall be
1672 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
1673 and FLT_ROUNDS have separate names for all three floating-point types. The floating-point
1674 model representation is provided for all values except FLT_EVAL_METHOD and
1675 FLT_ROUNDS.
1677 The rounding mode for floating-point addition is characterized by the implementation-
1679 <pre>
1680 -1 indeterminable
1681 0 toward zero
1682 1 to nearest
1683 2 toward positive infinity
1684 3 toward negative infinity
1685 </pre>
1686 All other values for FLT_ROUNDS characterize implementation-defined rounding
1687 behavior.
1689 Except for assignment and cast (which remove all extra range and precision), the values
1690 of operations with floating operands and values subject to the usual arithmetic
1691 conversions and of floating constants are evaluated to a format whose range and precision
1692 may be greater than required by the type. The use of evaluation formats is characterized
1693 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note19"><b>19)</b></a></sup>
1697 <!--page 37 -->
1698 <pre>
1699 -1 indeterminable;
1700 0 evaluate all operations and constants just to the range and precision of the
1701 type;
1702 1 evaluate operations and constants of type float and double to the
1703 range and precision of the double type, evaluate long double
1704 operations and constants to the range and precision of the long double
1705 type;
1706 2 evaluate all operations and constants to the range and precision of the
1707 long double type.
1708 </pre>
1709 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
1710 behavior.
1712 The values given in the following list shall be replaced by constant expressions with
1713 implementation-defined values that are greater or equal in magnitude (absolute value) to
1714 those shown, with the same sign:
1715 <ul>
1716 <li> radix of exponent representation, b
1717 <pre>
1718 FLT_RADIX 2
1719 </pre>
1720 <li> number of base-FLT_RADIX digits in the floating-point significand, p
1721 <pre>
1722 FLT_MANT_DIG
1723 DBL_MANT_DIG
1724 LDBL_MANT_DIG
1725 </pre>
1726 <li> number of decimal digits, n, such that any floating-point number in the widest
1727 supported floating type with pmax radix b digits can be rounded to a floating-point
1728 number with n decimal digits and back again without change to the value,
1729 <pre>
1730 { pmax log10 b if b is a power of 10
1731 {
1732 { [^1 + pmax log10 b^] otherwise
1733 </pre>
1734 <pre>
1735 DECIMAL_DIG 10
1736 </pre>
1737 <li> number of decimal digits, q, such that any floating-point number with q decimal digits
1738 can be rounded into a floating-point number with p radix b digits and back again
1739 without change to the q decimal digits,
1744 <!--page 38 -->
1745 <pre>
1746 { p log10 b if b is a power of 10
1747 {
1748 { [_( p - 1) log10 b_] otherwise
1749 </pre>
1750 <pre>
1751 FLT_DIG 6
1752 DBL_DIG 10
1753 LDBL_DIG 10
1754 </pre>
1755 <li> minimum negative integer such that FLT_RADIX raised to one less than that power is
1756 a normalized floating-point number, emin
1757 <pre>
1758 FLT_MIN_EXP
1759 DBL_MIN_EXP
1760 LDBL_MIN_EXP
1761 </pre>
1764 <pre>
1765 FLT_MIN_10_EXP -37
1766 DBL_MIN_10_EXP -37
1767 LDBL_MIN_10_EXP -37
1768 </pre>
1769 <li> maximum integer such that FLT_RADIX raised to one less than that power is a
1770 representable finite floating-point number, emax
1771 <pre>
1772 FLT_MAX_EXP
1773 DBL_MAX_EXP
1774 LDBL_MAX_EXP
1775 </pre>
1778 <pre>
1779 FLT_MAX_10_EXP +37
1780 DBL_MAX_10_EXP +37
1781 LDBL_MAX_10_EXP +37
1782 </pre>
1783 </ul>
1785 The values given in the following list shall be replaced by constant expressions with
1786 implementation-defined values that are greater than or equal to those shown:
1787 <ul>
1789 <pre>
1790 FLT_MAX 1E+37
1791 DBL_MAX 1E+37
1792 LDBL_MAX 1E+37
1793 </pre>
1794 </ul>
1796 The values given in the following list shall be replaced by constant expressions with
1797 implementation-defined (positive) values that are less than or equal to those shown:
1798 <ul>
1801 <!--page 39 -->
1802 <pre>
1803 FLT_EPSILON 1E-5
1804 DBL_EPSILON 1E-9
1805 LDBL_EPSILON 1E-9
1806 </pre>
1808 <pre>
1809 FLT_MIN 1E-37
1810 DBL_MIN 1E-37
1811 LDBL_MIN 1E-37
1812 </pre>
1813 </ul>
1816 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
1817 should be the identity function.
1819 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
1820 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
1821 float:
1822 <pre>
1823 6
1825 k=1
1826 </pre>
1828 <pre>
1829 FLT_RADIX 16
1830 FLT_MANT_DIG 6
1831 FLT_EPSILON 9.53674316E-07F
1832 FLT_DIG 6
1833 FLT_MIN_EXP -31
1834 FLT_MIN 2.93873588E-39F
1835 FLT_MIN_10_EXP -38
1836 FLT_MAX_EXP +32
1837 FLT_MAX 3.40282347E+38F
1838 FLT_MAX_10_EXP +38
1839 </pre>
1842 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
1843 single-precision and double-precision normalized numbers in IEC 60559,<sup><a href="#note20"><b>20)</b></a></sup> and the appropriate values in a
1845 <pre>
1846 24
1848 k=1
1849 </pre>
1851 <pre>
1852 53
1854 k=1
1855 </pre>
1858 <pre>
1859 FLT_RADIX 2
1860 DECIMAL_DIG 17
1861 FLT_MANT_DIG 24
1862 FLT_EPSILON 1.19209290E-07F // decimal constant
1864 </pre>
1867 <!--page 40 -->
1868 <pre>
1869 FLT_DIG 6
1870 FLT_MIN_EXP -125
1871 FLT_MIN 1.17549435E-38F // decimal constant
1873 FLT_MIN_10_EXP -37
1874 FLT_MAX_EXP +128
1875 FLT_MAX 3.40282347E+38F // decimal constant
1876 FLT_MAX 0X1.fffffeP127F // hex constant
1877 FLT_MAX_10_EXP +38
1878 DBL_MANT_DIG 53
1879 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
1881 DBL_DIG 15
1882 DBL_MIN_EXP -1021
1883 DBL_MIN 2.2250738585072014E-308 // decimal constant
1885 DBL_MIN_10_EXP -307
1886 DBL_MAX_EXP +1024
1887 DBL_MAX 1.7976931348623157E+308 // decimal constant
1888 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
1889 DBL_MAX_10_EXP +308
1890 </pre>
1891 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
1892 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
1893 precision), then DECIMAL_DIG would be 21.
1895 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
1896 <a href="#7.3"><complex.h></a> (<a href="#7.3">7.3</a>), extended multibyte and wide character utilities <a href="#7.24"><wchar.h></a>
1897 (<a href="#7.24">7.24</a>), floating-point environment <a href="#7.6"><fenv.h></a> (<a href="#7.6">7.6</a>), general utilities <a href="#7.20"><stdlib.h></a>
1898 (<a href="#7.20">7.20</a>), input/output <a href="#7.19"><stdio.h></a> (<a href="#7.19">7.19</a>), mathematics <a href="#7.12"><math.h></a> (<a href="#7.12">7.12</a>).
1899 <!--page 41 -->
1902 <p><small><a name="note16" href="#note16">16)</a> The floating-point model is intended to clarify the description of each floating-point characteristic and
1903 does not require the floating-point arithmetic of the implementation to be identical.
1904 </small>
1905 <p><small><a name="note17" href="#note17">17)</a> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
1907 similar behavior.
1908 </small>
1909 <p><small><a name="note18" href="#note18">18)</a> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
1911 </small>
1912 <p><small><a name="note19" href="#note19">19)</a> The evaluation method determines evaluation formats of expressions involving all floating types, not
1913 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
1914 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
1915 double.
1916 </small>
1917 <p><small><a name="note20" href="#note20">20)</a> The floating-point model in that standard sums powers of b from zero, so the values of the exponent
1918 limits are one less than shown here.
1919 </small>
1925 In the syntax notation used in this clause, syntactic categories (nonterminals) are
1926 indicated by italic type, and literal words and character set members (terminals) by bold
1927 type. A colon (:) following a nonterminal introduces its definition. Alternative
1928 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
1929 optional symbol is indicated by the subscript ''opt'', so that
1930 <pre>
1932 </pre>
1933 indicates an optional expression enclosed in braces.
1935 When syntactic categories are referred to in the main text, they are not italicized and
1936 words are separated by spaces instead of hyphens.
1944 An identifier can denote an object; a function; a tag or a member of a structure, union, or
1945 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
1946 same identifier can denote different entities at different points in the program. A member
1947 of an enumeration is called an enumeration constant. Macro names and macro
1948 parameters are not considered further here, because prior to the semantic phase of
1949 program translation any occurrences of macro names in the source file are replaced by the
1950 preprocessing token sequences that constitute their macro definitions.
1952 For each different entity that an identifier designates, the identifier is visible (i.e., can be
1953 used) only within a region of program text called its scope. Different entities designated
1954 by the same identifier either have different scopes, or are in different name spaces. There
1955 are four kinds of scopes: function, file, block, and function prototype. (A function
1956 prototype is a declaration of a function that declares the types of its parameters.)
1958 A label name is the only kind of identifier that has function scope. It can be used (in a
1959 goto statement) anywhere in the function in which it appears, and is declared implicitly
1960 by its syntactic appearance (followed by a : and a statement).
1962 Every other identifier has scope determined by the placement of its declaration (in a
1963 declarator or type specifier). If the declarator or type specifier that declares the identifier
1964 appears outside of any block or list of parameters, the identifier has file scope, which
1965 terminates at the end of the translation unit. If the declarator or type specifier that
1966 declares the identifier appears inside a block or within the list of parameter declarations in
1967 a function definition, the identifier has block scope, which terminates at the end of the
1968 associated block. If the declarator or type specifier that declares the identifier appears
1969 <!--page 42 -->
1970 within the list of parameter declarations in a function prototype (not part of a function
1971 definition), the identifier has function prototype scope, which terminates at the end of the
1972 function declarator. If an identifier designates two different entities in the same name
1973 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will be a
1974 strict subset of the scope of the other entity (the outer scope). Within the inner scope, the
1975 identifier designates the entity declared in the inner scope; the entity declared in the outer
1976 scope is hidden (and not visible) within the inner scope.
1978 Unless explicitly stated otherwise, where this International Standard uses the term
1979 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
1980 entity in the relevant name space whose declaration is visible at the point the identifier
1981 occurs.
1983 Two identifiers have the same scope if and only if their scopes terminate at the same
1984 point.
1986 Structure, union, and enumeration tags have scope that begins just after the appearance of
1987 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
1988 begins just after the appearance of its defining enumerator in an enumerator list. Any
1989 other identifier has scope that begins just after the completion of its declarator.
1990 <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
1991 (<a href="#6.9.1">6.9.1</a>), identifiers (<a href="#6.4.2">6.4.2</a>), name spaces of identifiers (<a href="#6.2.3">6.2.3</a>), macro replacement (<a href="#6.10.3">6.10.3</a>),
1996 An identifier declared in different scopes or in the same scope more than once can be
1997 made to refer to the same object or function by a process called linkage.<sup><a href="#note21"><b>21)</b></a></sup> There are
1998 three kinds of linkage: external, internal, and none.
2000 In the set of translation units and libraries that constitutes an entire program, each
2001 declaration of a particular identifier with external linkage denotes the same object or
2002 function. Within one translation unit, each declaration of an identifier with internal
2003 linkage denotes the same object or function. Each declaration of an identifier with no
2004 linkage denotes a unique entity.
2006 If the declaration of a file scope identifier for an object or a function contains the storage-
2007 class specifier static, the identifier has internal linkage.<sup><a href="#note22"><b>22)</b></a></sup>
2009 For an identifier declared with the storage-class specifier extern in a scope in which a
2013 <!--page 43 -->
2014 prior declaration of that identifier is visible,<sup><a href="#note23"><b>23)</b></a></sup> if the prior declaration specifies internal or
2015 external linkage, the linkage of the identifier at the later declaration is the same as the
2016 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
2017 declaration specifies no linkage, then the identifier has external linkage.
2019 If the declaration of an identifier for a function has no storage-class specifier, its linkage
2020 is determined exactly as if it were declared with the storage-class specifier extern. If
2021 the declaration of an identifier for an object has file scope and no storage-class specifier,
2022 its linkage is external.
2024 The following identifiers have no linkage: an identifier declared to be anything other than
2025 an object or a function; an identifier declared to be a function parameter; a block scope
2026 identifier for an object declared without the storage-class specifier extern.
2028 If, within a translation unit, the same identifier appears with both internal and external
2029 linkage, the behavior is undefined.
2030 <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>),
2034 <p><small><a name="note21" href="#note21">21)</a> There is no linkage between different identifiers.
2035 </small>
2036 <p><small><a name="note22" href="#note22">22)</a> A function declaration can contain the storage-class specifier static only if it is at file scope; see
2038 </small>
2039 <p><small><a name="note23" href="#note23">23)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2040 </small>
2044 If more than one declaration of a particular identifier is visible at any point in a
2045 translation unit, the syntactic context disambiguates uses that refer to different entities.
2046 Thus, there are separate name spaces for various categories of identifiers, as follows:
2047 <ul>
2048 <li> label names (disambiguated by the syntax of the label declaration and use);
2049 <li> the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note24"><b>24)</b></a></sup>
2050 of the keywords struct, union, or enum);
2051 <li> the members of structures or unions; each structure or union has a separate name
2052 space for its members (disambiguated by the type of the expression used to access the
2053 member via the . or -> operator);
2054 <li> all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
2055 enumeration constants).
2056 </ul>
2057 <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>),
2058 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
2064 <!--page 44 -->
2067 <p><small><a name="note24" href="#note24">24)</a> There is only one name space for tags even though three are possible.
2068 </small>
2072 An object has a storage duration that determines its lifetime. There are three storage
2073 durations: static, automatic, and allocated. Allocated storage is described in <a href="#7.20.3">7.20.3</a>.
2075 The lifetime of an object is the portion of program execution during which storage is
2076 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note25"><b>25)</b></a></sup> and retains
2077 its last-stored value throughout its lifetime.<sup><a href="#note26"><b>26)</b></a></sup> If an object is referred to outside of its
2078 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
2079 the object it points to reaches the end of its lifetime.
2081 An object whose identifier is declared with external or internal linkage, or with the
2082 storage-class specifier static has static storage duration. Its lifetime is the entire
2083 execution of the program and its stored value is initialized only once, prior to program
2084 startup.
2086 An object whose identifier is declared with no linkage and without the storage-class
2087 specifier static has automatic storage duration.
2089 For such an object that does not have a variable length array type, its lifetime extends
2090 from entry into the block with which it is associated until execution of that block ends in
2091 any way. (Entering an enclosed block or calling a function suspends, but does not end,
2092 execution of the current block.) If the block is entered recursively, a new instance of the
2093 object is created each time. The initial value of the object is indeterminate. If an
2094 initialization is specified for the object, it is performed each time the declaration is
2095 reached in the execution of the block; otherwise, the value becomes indeterminate each
2096 time the declaration is reached.
2098 For such an object that does have a variable length array type, its lifetime extends from
2099 the declaration of the object until execution of the program leaves the scope of the
2100 declaration.<sup><a href="#note27"><b>27)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2101 each time. The initial value of the object is indeterminate.
2102 <p><b> Forward references</b>: statements (<a href="#6.8">6.8</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), declarators (<a href="#6.7.5">6.7.5</a>), array
2108 <!--page 45 -->
2111 <p><small><a name="note25" href="#note25">25)</a> The term ''constant address'' means that two pointers to the object constructed at possibly different
2112 times will compare equal. The address may be different during two different executions of the same
2113 program.
2114 </small>
2115 <p><small><a name="note26" href="#note26">26)</a> In the case of a volatile object, the last store need not be explicit in the program.
2116 </small>
2117 <p><small><a name="note27" href="#note27">27)</a> Leaving the innermost block containing the declaration, or jumping to a point in that block or an
2118 embedded block prior to the declaration, leaves the scope of the declaration.
2119 </small>
2123 The meaning of a value stored in an object or returned by a function is determined by the
2124 type of the expression used to access it. (An identifier declared to be an object is the
2125 simplest such expression; the type is specified in the declaration of the identifier.) Types
2126 are partitioned into object types (types that fully describe objects), function types (types
2127 that describe functions), and incomplete types (types that describe objects but lack
2128 information needed to determine their sizes).
2132 An object declared as type char is large enough to store any member of the basic
2133 execution character set. If a member of the basic execution character set is stored in a
2134 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2135 a char object, the resulting value is implementation-defined but shall be within the range
2136 of values that can be represented in that type.
2138 There are five standard signed integer types, designated as signed char, short
2139 int, int, long int, and long long int. (These and other types may be
2140 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2141 implementation-defined extended signed integer types.<sup><a href="#note28"><b>28)</b></a></sup> The standard and extended
2142 signed integer types are collectively called signed integer types.<sup><a href="#note29"><b>29)</b></a></sup>
2144 An object declared as type signed char occupies the same amount of storage as a
2145 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2146 architecture of the execution environment (large enough to contain any value in the range
2149 For each of the signed integer types, there is a corresponding (but different) unsigned
2150 integer type (designated with the keyword unsigned) that uses the same amount of
2151 storage (including sign information) and has the same alignment requirements. The type
2152 _Bool and the unsigned integer types that correspond to the standard signed integer
2153 types are the standard unsigned integer types. The unsigned integer types that
2154 correspond to the extended signed integer types are the extended unsigned integer types.
2155 The standard and extended unsigned integer types are collectively called unsigned integer
2160 <!--page 46 -->
2162 The standard signed integer types and standard unsigned integer types are collectively
2163 called the standard integer types, the extended signed integer types and extended
2164 unsigned integer types are collectively called the extended integer types.
2166 For any two integer types with the same signedness and different integer conversion rank
2167 (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
2168 subrange of the values of the other type.
2170 The range of nonnegative values of a signed integer type is a subrange of the
2171 corresponding unsigned integer type, and the representation of the same value in each
2172 type is the same.<sup><a href="#note31"><b>31)</b></a></sup> A computation involving unsigned operands can never overflow,
2173 because a result that cannot be represented by the resulting unsigned integer type is
2174 reduced modulo the number that is one greater than the largest value that can be
2175 represented by the resulting type.
2177 There are three real floating types, designated as float, double, and long
2178 double.<sup><a href="#note32"><b>32)</b></a></sup> The set of values of the type float is a subset of the set of values of the
2179 type double; the set of values of the type double is a subset of the set of values of the
2180 type long double.
2182 There are three complex types, designated as float _Complex, double
2183 _Complex, and long double _Complex.<sup><a href="#note33"><b>33)</b></a></sup> The real floating and complex types
2184 are collectively called the floating types.
2186 For each floating type there is a corresponding real type, which is always a real floating
2187 type. For real floating types, it is the same type. For complex types, it is the type given
2188 by deleting the keyword _Complex from the type name.
2190 Each complex type has the same representation and alignment requirements as an array
2191 type containing exactly two elements of the corresponding real type; the first element is
2192 equal to the real part, and the second element to the imaginary part, of the complex
2193 number.
2195 The type char, the signed and unsigned integer types, and the floating types are
2196 collectively called the basic types. Even if the implementation defines two or more basic
2197 types to have the same representation, they are nevertheless different types.<sup><a href="#note34"><b>34)</b></a></sup>
2199 <!--page 47 -->
2201 The three types char, signed char, and unsigned char are collectively called
2202 the character types. The implementation shall define char to have the same range,
2203 representation, and behavior as either signed char or unsigned char.<sup><a href="#note35"><b>35)</b></a></sup>
2205 An enumeration comprises a set of named integer constant values. Each distinct
2206 enumeration constitutes a different enumerated type.
2208 The type char, the signed and unsigned integer types, and the enumerated types are
2209 collectively called integer types. The integer and real floating types are collectively called
2210 real types.
2212 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2213 belongs to one type domain: the real type domain comprises the real types, the complex
2214 type domain comprises the complex types.
2216 The void type comprises an empty set of values; it is an incomplete type that cannot be
2217 completed.
2219 Any number of derived types can be constructed from the object, function, and
2220 incomplete types, as follows:
2221 <ul>
2222 <li> An array type describes a contiguously allocated nonempty set of objects with a
2223 particular member object type, called the element type.<sup><a href="#note36"><b>36)</b></a></sup> Array types are
2224 characterized by their element type and by the number of elements in the array. An
2225 array type is said to be derived from its element type, and if its element type is T , the
2226 array type is sometimes called ''array of T ''. The construction of an array type from
2227 an element type is called ''array type derivation''.
2228 <li> A structure type describes a sequentially allocated nonempty set of member objects
2229 (and, in certain circumstances, an incomplete array), each of which has an optionally
2230 specified name and possibly distinct type.
2231 <li> A union type describes an overlapping nonempty set of member objects, each of
2232 which has an optionally specified name and possibly distinct type.
2233 <li> A function type describes a function with specified return type. A function type is
2234 characterized by its return type and the number and types of its parameters. A
2235 function type is said to be derived from its return type, and if its return type is T , the
2236 function type is sometimes called ''function returning T ''. The construction of a
2237 function type from a return type is called ''function type derivation''.
2241 <!--page 48 -->
2242 <li> A pointer type may be derived from a function type, an object type, or an incomplete
2243 type, called the referenced type. A pointer type describes an object whose value
2244 provides a reference to an entity of the referenced type. A pointer type derived from
2245 the referenced type T is sometimes called ''pointer to T ''. The construction of a
2246 pointer type from a referenced type is called ''pointer type derivation''.
2247 </ul>
2248 These methods of constructing derived types can be applied recursively.
2250 Arithmetic types and pointer types are collectively called scalar types. Array and
2251 structure types are collectively called aggregate types.<sup><a href="#note37"><b>37)</b></a></sup>
2253 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2254 that type, by specifying the size in a later declaration (with internal or external linkage).
2255 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
2256 type. It is completed, for all declarations of that type, by declaring the same structure or
2257 union tag with its defining content later in the same scope.
2259 A type has known constant size if the type is not incomplete and is not a variable length
2260 array type.
2262 Array, function, and pointer types are collectively called derived declarator types. A
2263 declarator type derivation from a type T is the construction of a derived declarator type
2264 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2265 T.
2267 A type is characterized by its type category, which is either the outermost derivation of a
2268 derived type (as noted above in the construction of derived types), or the type itself if the
2269 type consists of no derived types.
2271 Any type so far mentioned is an unqualified type. Each unqualified type has several
2272 qualified versions of its type,<sup><a href="#note38"><b>38)</b></a></sup> corresponding to the combinations of one, two, or all
2273 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2274 versions of a type are distinct types that belong to the same type category and have the
2275 same representation and alignment requirements.<sup><a href="#note39"><b>39)</b></a></sup> A derived type is not qualified by the
2276 qualifiers (if any) of the type from which it is derived.
2278 A pointer to void shall have the same representation and alignment requirements as a
2279 pointer to a character type.<sup><a href="#note39"><b>39)</b></a></sup> Similarly, pointers to qualified or unqualified versions of
2280 compatible types shall have the same representation and alignment requirements. All
2283 <!--page 49 -->
2284 pointers to structure types shall have the same representation and alignment requirements
2285 as each other. All pointers to union types shall have the same representation and
2286 alignment requirements as each other. Pointers to other types need not have the same
2287 representation or alignment requirements.
2289 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2290 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2291 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2292 qualified float'' and is a pointer to a qualified type.
2296 function returning struct tag''. The array has length five and the function has a single parameter of type
2297 float. Its type category is array.
2299 <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>).
2302 <p><small><a name="note28" href="#note28">28)</a> Implementation-defined keywords shall have the form of an identifier reserved for any use as
2304 </small>
2305 <p><small><a name="note29" href="#note29">29)</a> Therefore, any statement in this Standard about signed integer types also applies to the extended
2306 signed integer types.
2307 </small>
2308 <p><small><a name="note30" href="#note30">30)</a> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2309 unsigned integer types.
2310 </small>
2311 <p><small><a name="note31" href="#note31">31)</a> The same representation and alignment requirements are meant to imply interchangeability as
2312 arguments to functions, return values from functions, and members of unions.
2313 </small>
2314 <p><small><a name="note32" href="#note32">32)</a> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2315 </small>
2316 <p><small><a name="note33" href="#note33">33)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
2317 </small>
2318 <p><small><a name="note34" href="#note34">34)</a> An implementation may define new keywords that provide alternative ways to designate a basic (or
2319 any other) type; this does not violate the requirement that all basic types be different.
2320 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2322 </small>
2323 <p><small><a name="note35" href="#note35">35)</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
2324 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2325 other two and is not compatible with either.
2326 </small>
2327 <p><small><a name="note36" href="#note36">36)</a> Since object types do not include incomplete types, an array of incomplete type cannot be constructed.
2328 </small>
2329 <p><small><a name="note37" href="#note37">37)</a> Note that aggregate type does not include union type because an object with union type can only
2330 contain one member at a time.
2331 </small>
2332 <p><small><a name="note38" href="#note38">38)</a> See <a href="#6.7.3">6.7.3</a> regarding qualified array and function types.
2333 </small>
2334 <p><small><a name="note39" href="#note39">39)</a> The same representation and alignment requirements are meant to imply interchangeability as
2335 arguments to functions, return values from functions, and members of unions.
2336 </small>
2342 The representations of all types are unspecified except as stated in this subclause.
2344 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2345 the number, order, and encoding of which are either explicitly specified or
2346 implementation-defined.
2348 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2351 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2352 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2353 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
2354 called the object representation of the value. Values stored in bit-fields consist of m bits,
2355 where m is the size specified for the bit-field. The object representation is the set of m
2356 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
2357 than NaNs) with the same object representation compare equal, but values that compare
2358 equal may have different object representations.
2360 Certain object representations need not represent a value of the object type. If the stored
2361 value of an object has such a representation and is read by an lvalue expression that does
2362 not have character type, the behavior is undefined. If such a representation is produced
2363 by a side effect that modifies all or any part of the object by an lvalue expression that
2364 does not have character type, the behavior is undefined.<sup><a href="#note41"><b>41)</b></a></sup> Such a representation is called
2366 <!--page 50 -->
2367 a trap representation.
2369 When a value is stored in an object of structure or union type, including in a member
2370 object, the bytes of the object representation that correspond to any padding bytes take
2371 unspecified values.<sup><a href="#note42"><b>42)</b></a></sup> The value of a structure or union object is never a trap
2372 representation, even though the value of a member of the structure or union object may be
2373 a trap representation.
2375 When a value is stored in a member of an object of union type, the bytes of the object
2376 representation that do not correspond to that member but do correspond to other members
2377 take unspecified values.
2379 Where an operator is applied to a value that has more than one object representation,
2380 which object representation is used shall not affect the value of the result.<sup><a href="#note43"><b>43)</b></a></sup> Where a
2381 value is stored in an object using a type that has more than one object representation for
2382 that value, it is unspecified which representation is used, but a trap representation shall
2383 not be generated.
2384 <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
2388 <p><small><a name="note40" href="#note40">40)</a> A positional representation for integers that uses the binary digits 0 and 1, in which the values
2389 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
2390 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
2391 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
2393 </small>
2394 <p><small><a name="note41" href="#note41">41)</a> Thus, an automatic variable can be initialized to a trap representation without causing undefined
2395 behavior, but the value of the variable cannot be used until a proper value is stored in it.
2396 </small>
2397 <p><small><a name="note42" href="#note42">42)</a> Thus, for example, structure assignment need not copy any padding bits.
2398 </small>
2399 <p><small><a name="note43" href="#note43">43)</a> It is possible for objects x and y with the same effective type T to have the same value when they are
2400 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
2402 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
2403 on values of type T may distinguish between them.
2404 </small>
2408 For unsigned integer types other than unsigned char, the bits of the object
2409 representation shall be divided into two groups: value bits and padding bits (there need
2410 not be any of the latter). If there are N value bits, each bit shall represent a different
2412 representing values from 0 to 2<sup>N</sup> - 1 using a pure binary representation; this shall be
2413 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note44"><b>44)</b></a></sup>
2415 For signed integer types, the bits of the object representation shall be divided into three
2416 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
2418 <!--page 51 -->
2419 there shall be exactly one sign bit. Each bit that is a value bit shall have the same value as
2420 the same bit in the object representation of the corresponding unsigned type (if there are
2421 M value bits in the signed type and N in the unsigned type, then M <= N ). If the sign bit
2422 is zero, it shall not affect the resulting value. If the sign bit is one, the value shall be
2423 modified in one of the following ways:
2424 <ul>
2428 </ul>
2429 Which of these applies is implementation-defined, as is whether the value with sign bit 1
2430 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
2431 complement), is a trap representation or a normal value. In the case of sign and
2432 magnitude and ones' complement, if this representation is a normal value it is called a
2433 negative zero.
2435 If the implementation supports negative zeros, they shall be generated only by:
2436 <ul>
2437 <li> the &, |, ^, ~, <<, and >> operators with arguments that produce such a value;
2438 <li> the +, -, *, /, and % operators where one argument is a negative zero and the result is
2439 zero;
2440 <li> compound assignment operators based on the above cases.
2441 </ul>
2442 It is unspecified whether these cases actually generate a negative zero or a normal zero,
2443 and whether a negative zero becomes a normal zero when stored in an object.
2445 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
2446 and >> operators with arguments that would produce such a value is undefined.
2448 The values of any padding bits are unspecified.<sup><a href="#note45"><b>45)</b></a></sup> A valid (non-trap) object representation
2449 of a signed integer type where the sign bit is zero is a valid object representation of the
2450 corresponding unsigned type, and shall represent the same value. For any integer type,
2451 the object representation where all the bits are zero shall be a representation of the value
2452 zero in that type.
2454 The precision of an integer type is the number of bits it uses to represent values,
2455 excluding any sign and padding bits. The width of an integer type is the same but
2456 including any sign bit; thus for unsigned integer types the two values are the same, while
2459 <!--page 52 -->
2460 for signed integer types the width is one greater than the precision.
2463 <p><small><a name="note44" href="#note44">44)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2464 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2465 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
2466 with unsigned types. All other combinations of padding bits are alternative object representations of
2467 the value specified by the value bits.
2468 </small>
2469 <p><small><a name="note45" href="#note45">45)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2470 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2471 representation other than as part of an exceptional condition such as an overflow. All other
2472 combinations of padding bits are alternative object representations of the value specified by the value
2473 bits.
2474 </small>
2478 Two types have compatible type if their types are the same. Additional rules for
2479 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
2480 in <a href="#6.7.3">6.7.3</a> for type qualifiers, and in <a href="#6.7.5">6.7.5</a> for declarators.<sup><a href="#note46"><b>46)</b></a></sup> Moreover, two structure,
2481 union, or enumerated types declared in separate translation units are compatible if their
2482 tags and members satisfy the following requirements: If one is declared with a tag, the
2483 other shall be declared with the same tag. If both are complete types, then the following
2484 additional requirements apply: there shall be a one-to-one correspondence between their
2485 members such that each pair of corresponding members are declared with compatible
2486 types, and such that if one member of a corresponding pair is declared with a name, the
2487 other member is declared with the same name. For two structures, corresponding
2488 members shall be declared in the same order. For two structures or unions, corresponding
2489 bit-fields shall have the same widths. For two enumerations, corresponding members
2490 shall have the same values.
2492 All declarations that refer to the same object or function shall have compatible type;
2493 otherwise, the behavior is undefined.
2495 A composite type can be constructed from two types that are compatible; it is a type that
2496 is compatible with both of the two types and satisfies the following conditions:
2497 <ul>
2498 <li> If one type is an array of known constant size, the composite type is an array of that
2499 size; otherwise, if one type is a variable length array, the composite type is that type.
2500 <li> If only one type is a function type with a parameter type list (a function prototype),
2501 the composite type is a function prototype with the parameter type list.
2502 <li> If both types are function types with parameter type lists, the type of each parameter
2503 in the composite parameter type list is the composite type of the corresponding
2504 parameters.
2505 </ul>
2506 These rules apply recursively to the types from which the two types are derived.
2508 For an identifier with internal or external linkage declared in a scope in which a prior
2509 declaration of that identifier is visible,<sup><a href="#note47"><b>47)</b></a></sup> if the prior declaration specifies internal or
2510 external linkage, the type of the identifier at the later declaration becomes the composite
2511 type.
2516 <!--page 53 -->
2518 EXAMPLE Given the following two file scope declarations:
2519 <pre>
2520 int f(int (*)(), double (*)[3]);
2521 int f(int (*)(char *), double (*)[]);
2522 </pre>
2523 The resulting composite type for the function is:
2524 <!--page 54 -->
2525 <pre>
2526 int f(int (*)(char *), double (*)[3]);
2527 </pre>
2530 <p><small><a name="note46" href="#note46">46)</a> Two types need not be identical to be compatible.
2531 </small>
2532 <p><small><a name="note47" href="#note47">47)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2533 </small>
2537 Several operators convert operand values from one type to another automatically. This
2538 subclause specifies the result required from such an implicit conversion, as well as those
2539 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
2540 the conversions performed by most ordinary operators; it is supplemented as required by
2543 Conversion of an operand value to a compatible type causes no change to the value or the
2544 representation.
2551 Every integer type has an integer conversion rank defined as follows:
2552 <ul>
2553 <li> No two signed integer types shall have the same rank, even if they have the same
2554 representation.
2555 <li> The rank of a signed integer type shall be greater than the rank of any signed integer
2556 type with less precision.
2557 <li> The rank of long long int shall be greater than the rank of long int, which
2558 shall be greater than the rank of int, which shall be greater than the rank of short
2559 int, which shall be greater than the rank of signed char.
2560 <li> The rank of any unsigned integer type shall equal the rank of the corresponding
2561 signed integer type, if any.
2562 <li> The rank of any standard integer type shall be greater than the rank of any extended
2563 integer type with the same width.
2564 <li> The rank of char shall equal the rank of signed char and unsigned char.
2565 <li> The rank of _Bool shall be less than the rank of all other standard integer types.
2566 <li> The rank of any enumerated type shall equal the rank of the compatible integer type
2568 <li> The rank of any extended signed integer type relative to another extended signed
2569 integer type with the same precision is implementation-defined, but still subject to the
2570 other rules for determining the integer conversion rank.
2571 <li> For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
2572 greater rank than T3, then T1 has greater rank than T3.
2573 </ul>
2575 The following may be used in an expression wherever an int or unsigned int may
2576 be used:
2577 <!--page 55 -->
2578 <ul>
2579 <li> An object or expression with an integer type whose integer conversion rank is less
2580 than or equal to the rank of int and unsigned int.
2581 <li> A bit-field of type _Bool, int, signed int, or unsigned int.
2582 </ul>
2583 If an int can represent all values of the original type, the value is converted to an int;
2584 otherwise, it is converted to an unsigned int. These are called the integer
2585 promotions.<sup><a href="#note48"><b>48)</b></a></sup> All other types are unchanged by the integer promotions.
2587 The integer promotions preserve value including sign. As discussed earlier, whether a
2588 ''plain'' char is treated as signed is implementation-defined.
2589 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
2593 <p><small><a name="note48" href="#note48">48)</a> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
2594 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
2595 shift operators, as specified by their respective subclauses.
2596 </small>
2600 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
2605 When a value with integer type is converted to another integer type other than _Bool, if
2606 the value can be represented by the new type, it is unchanged.
2608 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
2609 subtracting one more than the maximum value that can be represented in the new type
2612 Otherwise, the new type is signed and the value cannot be represented in it; either the
2613 result is implementation-defined or an implementation-defined signal is raised.
2616 <p><small><a name="note49" href="#note49">49)</a> The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
2617 </small>
2621 When a finite value of real floating type is converted to an integer type other than _Bool,
2622 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
2623 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup>
2625 When a value of integer type is converted to a real floating type, if the value being
2626 converted can be represented exactly in the new type, it is unchanged. If the value being
2627 converted is in the range of values that can be represented but cannot be represented
2629 <!--page 56 -->
2630 exactly, the result is either the nearest higher or nearest lower representable value, chosen
2631 in an implementation-defined manner. If the value being converted is outside the range of
2632 values that can be represented, the behavior is undefined.
2635 <p><small><a name="note50" href="#note50">50)</a> The remaindering operation performed when a value of integer type is converted to unsigned type
2636 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
2638 </small>
2642 When a float is promoted to double or long double, or a double is promoted
2643 to long double, its value is unchanged (if the source value is represented in the
2644 precision and range of its type).
2646 When a double is demoted to float, a long double is demoted to double or
2647 float, or a value being represented in greater precision and range than required by its
2648 semantic type (see <a href="#6.3.1.8">6.3.1.8</a>) is explicitly converted (including to its own type), if the value
2649 being converted can be represented exactly in the new type, it is unchanged. If the value
2650 being converted is in the range of values that can be represented but cannot be
2651 represented exactly, the result is either the nearest higher or nearest lower representable
2652 value, chosen in an implementation-defined manner. If the value being converted is
2653 outside the range of values that can be represented, the behavior is undefined.
2657 When a value of complex type is converted to another complex type, both the real and
2658 imaginary parts follow the conversion rules for the corresponding real types.
2662 When a value of real type is converted to a complex type, the real part of the complex
2663 result value is determined by the rules of conversion to the corresponding real type and
2664 the imaginary part of the complex result value is a positive zero or an unsigned zero.
2666 When a value of complex type is converted to a real type, the imaginary part of the
2667 complex value is discarded and the value of the real part is converted according to the
2668 conversion rules for the corresponding real type.
2672 Many operators that expect operands of arithmetic type cause conversions and yield result
2673 types in a similar way. The purpose is to determine a common real type for the operands
2674 and result. For the specified operands, each operand is converted, without change of type
2675 domain, to a type whose corresponding real type is the common real type. Unless
2676 explicitly stated otherwise, the common real type is also the corresponding real type of
2677 the result, whose type domain is the type domain of the operands if they are the same,
2678 and complex otherwise. This pattern is called the usual arithmetic conversions:
2679 <!--page 57 -->
2680 <ul>
2681 <li> First, if the corresponding real type of either operand is long double, the other
2682 operand is converted, without change of type domain, to a type whose
2683 corresponding real type is long double.
2684 <li> Otherwise, if the corresponding real type of either operand is double, the other
2685 operand is converted, without change of type domain, to a type whose
2686 corresponding real type is double.
2687 <li> Otherwise, if the corresponding real type of either operand is float, the other
2688 operand is converted, without change of type domain, to a type whose
2690 <li> Otherwise, the integer promotions are performed on both operands. Then the
2691 following rules are applied to the promoted operands:
2692 <ul>
2693 <li> If both operands have the same type, then no further conversion is needed.
2694 <li> Otherwise, if both operands have signed integer types or both have unsigned
2695 integer types, the operand with the type of lesser integer conversion rank is
2696 converted to the type of the operand with greater rank.
2697 <li> Otherwise, if the operand that has unsigned integer type has rank greater or
2698 equal to the rank of the type of the other operand, then the operand with
2699 signed integer type is converted to the type of the operand with unsigned
2700 integer type.
2701 <li> Otherwise, if the type of the operand with signed integer type can represent
2702 all of the values of the type of the operand with unsigned integer type, then
2703 the operand with unsigned integer type is converted to the type of the
2704 operand with signed integer type.
2705 <li> Otherwise, both operands are converted to the unsigned integer type
2706 corresponding to the type of the operand with signed integer type.
2707 </ul>
2708 </ul>
2710 The values of floating operands and of the results of floating expressions may be
2711 represented in greater precision and range than that required by the type; the types are not
2717 <!--page 58 -->
2720 <p><small><a name="note51" href="#note51">51)</a> For example, addition of a double _Complex and a float entails just the conversion of the
2721 float operand to double (and yields a double _Complex result).
2722 </small>
2723 <p><small><a name="note52" href="#note52">52)</a> The cast and assignment operators are still required to perform their specified conversions as
2725 </small>
2729 <h5><a name="6.3.2.1" href="#6.3.2.1">6.3.2.1 Lvalues, arrays, and function designators</a></h5>
2731 An lvalue is an expression with an object type or an incomplete type other than void;<sup><a href="#note53"><b>53)</b></a></sup>
2732 if an lvalue does not designate an object when it is evaluated, the behavior is undefined.
2733 When an object is said to have a particular type, the type is specified by the lvalue used to
2734 designate the object. A modifiable lvalue is an lvalue that does not have array type, does
2735 not have an incomplete type, does not have a const-qualified type, and if it is a structure
2736 or union, does not have any member (including, recursively, any member or element of
2737 all contained aggregates or unions) with a const-qualified type.
2739 Except when it is the operand of the sizeof operator, the unary & operator, the ++
2740 operator, the -- operator, or the left operand of the . operator or an assignment operator,
2741 an lvalue that does not have array type is converted to the value stored in the designated
2742 object (and is no longer an lvalue). If the lvalue has qualified type, the value has the
2743 unqualified version of the type of the lvalue; otherwise, the value has the type of the
2744 lvalue. If the lvalue has an incomplete type and does not have array type, the behavior is
2745 undefined.
2747 Except when it is the operand of the sizeof operator or the unary & operator, or is a
2748 string literal used to initialize an array, an expression that has type ''array of type'' is
2749 converted to an expression with type ''pointer to type'' that points to the initial element of
2750 the array object and is not an lvalue. If the array object has register storage class, the
2751 behavior is undefined.
2753 A function designator is an expression that has function type. Except when it is the
2754 operand of the sizeof operator<sup><a href="#note54"><b>54)</b></a></sup> or the unary & operator, a function designator with
2755 type ''function returning type'' is converted to an expression that has type ''pointer to
2756 function returning type''.
2757 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
2758 (<a href="#6.5.16">6.5.16</a>), common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), initialization (<a href="#6.7.8">6.7.8</a>), postfix
2759 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2760 (<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>).
2763 <!--page 59 -->
2766 <p><small><a name="note53" href="#note53">53)</a> The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
2767 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
2768 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
2769 as the ''value of an expression''.
2770 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
2771 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
2772 </small>
2773 <p><small><a name="note54" href="#note54">54)</a> Because this conversion does not occur, the operand of the sizeof operator remains a function
2775 </small>
2779 The (nonexistent) value of a void expression (an expression that has type void) shall not
2780 be used in any way, and implicit or explicit conversions (except to void) shall not be
2781 applied to such an expression. If an expression of any other type is evaluated as a void
2782 expression, its value or designator is discarded. (A void expression is evaluated for its
2783 side effects.)
2787 A pointer to void may be converted to or from a pointer to any incomplete or object
2788 type. A pointer to any incomplete or object type may be converted to a pointer to void
2789 and back again; the result shall compare equal to the original pointer.
2791 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
2792 the q-qualified version of the type; the values stored in the original and converted pointers
2793 shall compare equal.
2795 An integer constant expression with the value 0, or such an expression cast to type
2796 void *, is called a null pointer constant.<sup><a href="#note55"><b>55)</b></a></sup> If a null pointer constant is converted to a
2797 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
2798 to a pointer to any object or function.
2800 Conversion of a null pointer to another pointer type yields a null pointer of that type.
2801 Any two null pointers shall compare equal.
2803 An integer may be converted to any pointer type. Except as previously specified, the
2804 result is implementation-defined, might not be correctly aligned, might not point to an
2805 entity of the referenced type, and might be a trap representation.<sup><a href="#note56"><b>56)</b></a></sup>
2807 Any pointer type may be converted to an integer type. Except as previously specified, the
2808 result is implementation-defined. If the result cannot be represented in the integer type,
2809 the behavior is undefined. The result need not be in the range of values of any integer
2810 type.
2812 A pointer to an object or incomplete type may be converted to a pointer to a different
2813 object or incomplete type. If the resulting pointer is not correctly aligned<sup><a href="#note57"><b>57)</b></a></sup> for the
2814 pointed-to type, the behavior is undefined. Otherwise, when converted back again, the
2815 result shall compare equal to the original pointer. When a pointer to an object is
2818 <!--page 60 -->
2819 converted to a pointer to a character type, the result points to the lowest addressed byte of
2820 the object. Successive increments of the result, up to the size of the object, yield pointers
2821 to the remaining bytes of the object.
2823 A pointer to a function of one type may be converted to a pointer to a function of another
2824 type and back again; the result shall compare equal to the original pointer. If a converted
2825 pointer is used to call a function whose type is not compatible with the pointed-to type,
2826 the behavior is undefined.
2827 <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
2828 capable of holding object pointers (<a href="#7.18.1.4">7.18.1.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
2829 <!--page 61 -->
2832 <p><small><a name="note55" href="#note55">55)</a> The macro NULL is defined in <a href="#7.17"><stddef.h></a> (and other headers) as a null pointer constant; see <a href="#7.17">7.17</a>.
2833 </small>
2834 <p><small><a name="note56" href="#note56">56)</a> The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to
2835 be consistent with the addressing structure of the execution environment.
2836 </small>
2837 <p><small><a name="note57" href="#note57">57)</a> In general, the concept ''correctly aligned'' is transitive: if a pointer to type A is correctly aligned for a
2838 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
2839 correctly aligned for a pointer to type C.
2840 </small>
2845 <pre>
2846 token:
2847 keyword
2848 identifier
2849 constant
2850 string-literal
2851 punctuator
2852 preprocessing-token:
2853 header-name
2854 identifier
2855 pp-number
2856 character-constant
2857 string-literal
2858 punctuator
2859 each non-white-space character that cannot be one of the above
2860 </pre>
2863 Each preprocessing token that is converted to a token shall have the lexical form of a
2864 keyword, an identifier, a constant, a string literal, or a punctuator.
2868 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
2869 A preprocessing token is the minimal lexical element of the language in translation
2871 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
2872 single non-white-space characters that do not lexically match the other preprocessing
2873 token categories.<sup><a href="#note58"><b>58)</b></a></sup> If a ' or a " character matches the last category, the behavior is
2874 undefined. Preprocessing tokens can be separated by white space; this consists of
2875 comments (described later), or white-space characters (space, horizontal tab, new-line,
2876 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
2877 during translation phase 4, white space (or the absence thereof) serves as more than
2878 preprocessing token separation. White space may appear within a preprocessing token
2879 only as part of a header name or between the quotation characters in a character constant
2880 or string literal.
2884 <!--page 62 -->
2885 <p><!--para 4 -->
2886 If the input stream has been parsed into preprocessing tokens up to a given character, the
2887 next preprocessing token is the longest sequence of characters that could constitute a
2888 preprocessing token. There is one exception to this rule: header name preprocessing
2889 tokens are recognized only within #include preprocessing directives and in
2890 implementation-defined locations within #pragma directives. In such contexts, a
2891 sequence of characters that could be either a header name or a string literal is recognized
2892 as the former.
2893 <p><!--para 5 -->
2894 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
2895 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
2896 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
2897 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
2898 not E is a macro name.
2900 <p><!--para 6 -->
2901 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
2902 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
2904 <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>),
2905 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
2906 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2907 (<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
2910 <p><b>Footnotes</b>
2911 <p><small><a name="note58" href="#note58">58)</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
2912 occur in source files.
2913 </small>
2916 <p><b>Syntax</b>
2917 <p><!--para 1 -->
2918 <pre>
2919 keyword: one of
2920 auto enum restrict unsigned
2921 break extern return void
2922 case float short volatile
2923 char for signed while
2924 const goto sizeof _Bool
2925 continue if static _Complex
2926 default inline struct _Imaginary
2927 do int switch
2928 double long typedef
2929 else register union
2930 </pre>
2931 <p><b>Semantics</b>
2932 <p><!--para 2 -->
2933 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
2934 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
2939 <!--page 63 -->
2941 <p><b>Footnotes</b>
2942 <p><small><a name="note59" href="#note59">59)</a> One possible specification for imaginary types appears in <a href="#G">annex G</a>.
2943 </small>
2948 <p><b>Syntax</b>
2949 <p><!--para 1 -->
2950 <pre>
2951 identifier:
2952 identifier-nondigit
2953 identifier identifier-nondigit
2954 identifier digit
2955 identifier-nondigit:
2956 nondigit
2957 universal-character-name
2958 other implementation-defined characters
2959 nondigit: one of
2960 _ a b c d e f g h i j k l m
2961 n o p q r s t u v w x y z
2962 A B C D E F G H I J K L M
2963 N O P Q R S T U V W X Y Z
2964 digit: one of
2965 0 1 2 3 4 5 6 7 8 9
2966 </pre>
2967 <p><b>Semantics</b>
2968 <p><!--para 2 -->
2969 An identifier is a sequence of nondigit characters (including the underscore _, the
2970 lowercase and uppercase Latin letters, and other characters) and digits, which designates
2971 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
2972 There is no specific limit on the maximum length of an identifier.
2973 <p><!--para 3 -->
2974 Each universal character name in an identifier shall designate a character whose encoding
2975 in ISO/IEC 10646 falls into one of the ranges specified in <a href="#D">annex D</a>.<sup><a href="#note60"><b>60)</b></a></sup> The initial
2976 character shall not be a universal character name designating a digit. An implementation
2977 may allow multibyte characters that are not part of the basic source character set to
2978 appear in identifiers; which characters and their correspondence to universal character
2979 names is implementation-defined.
2980 <p><!--para 4 -->
2981 When preprocessing tokens are converted to tokens during translation phase 7, if a
2982 preprocessing token could be converted to either a keyword or an identifier, it is converted
2983 to a keyword.
2986 <!--page 64 -->
2987 <p><b>Implementation limits</b>
2988 <p><!--para 5 -->
2989 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
2990 characters in an identifier; the limit for an external name (an identifier that has external
2991 linkage) may be more restrictive than that for an internal name (a macro name or an
2992 identifier that does not have external linkage). The number of significant characters in an
2993 identifier is implementation-defined.
2994 <p><!--para 6 -->
2995 Any identifiers that differ in a significant character are different identifiers. If two
2996 identifiers differ only in nonsignificant characters, the behavior is undefined.
2997 <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>).
2999 <p><b>Footnotes</b>
3000 <p><small><a name="note60" href="#note60">60)</a> On systems in which linkers cannot accept extended characters, an encoding of the universal character
3001 name may be used in forming valid external identifiers. For example, some otherwise unused
3002 character or sequence of characters may be used to encode the \u in a universal character name.
3003 Extended characters may produce a long external identifier.
3004 </small>
3007 <p><b>Semantics</b>
3008 <p><!--para 1 -->
3009 The identifier __func__ shall be implicitly declared by the translator as if,
3010 immediately following the opening brace of each function definition, the declaration
3011 <pre>
3013 </pre>
3014 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note61"><b>61)</b></a></sup>
3015 <p><!--para 2 -->
3016 This name is encoded as if the implicit declaration had been written in the source
3017 character set and then translated into the execution character set as indicated in translation
3018 phase 5.
3019 <p><!--para 3 -->
3020 EXAMPLE Consider the code fragment:
3021 <pre>
3023 void myfunc(void)
3024 {
3026 /* ... */
3027 }
3028 </pre>
3029 Each time the function is called, it will print to the standard output stream:
3030 <pre>
3031 myfunc
3032 </pre>
3039 <!--page 65 -->
3041 <p><b>Footnotes</b>
3042 <p><small><a name="note61" href="#note61">61)</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
3043 identifier is explicitly declared using the name __func__, the behavior is undefined.
3044 </small>
3047 <p><b>Syntax</b>
3048 <p><!--para 1 -->
3049 <pre>
3050 universal-character-name:
3051 \u hex-quad
3052 \U hex-quad hex-quad
3053 hex-quad:
3054 hexadecimal-digit hexadecimal-digit
3055 hexadecimal-digit hexadecimal-digit
3056 </pre>
3057 <p><b>Constraints</b>
3058 <p><!--para 2 -->
3059 A universal character name shall not specify a character whose short identifier is less than
3060 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
3062 <p><b>Description</b>
3063 <p><!--para 3 -->
3064 Universal character names may be used in identifiers, character constants, and string
3065 literals to designate characters that are not in the basic character set.
3066 <p><b>Semantics</b>
3067 <p><!--para 4 -->
3068 The universal character name \Unnnnnnnn designates the character whose eight-digit
3069 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note63"><b>63)</b></a></sup> Similarly, the universal
3070 character name \unnnn designates the character whose four-digit short identifier is nnnn
3071 (and whose eight-digit short identifier is 0000nnnn).
3076 <!--page 66 -->
3078 <p><b>Footnotes</b>
3079 <p><small><a name="note62" href="#note62">62)</a> The disallowed characters are the characters in the basic character set and the code positions reserved
3080 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
3081 UTF-16).
3082 </small>
3083 <p><small><a name="note63" href="#note63">63)</a> Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
3084 </small>
3087 <p><b>Syntax</b>
3088 <p><!--para 1 -->
3089 <pre>
3090 constant:
3091 integer-constant
3092 floating-constant
3093 enumeration-constant
3094 character-constant
3095 </pre>
3096 <p><b>Constraints</b>
3097 <p><!--para 2 -->
3098 Each constant shall have a type and the value of a constant shall be in the range of
3099 representable values for its type.
3100 <p><b>Semantics</b>
3101 <p><!--para 3 -->
3102 Each constant has a type, determined by its form and value, as detailed later.
3105 <p><b>Syntax</b>
3106 <p><!--para 1 -->
3107 <!--page 67 -->
3108 <pre>
3109 integer-constant:
3110 decimal-constant integer-suffix<sub>opt</sub>
3111 octal-constant integer-suffix<sub>opt</sub>
3112 hexadecimal-constant integer-suffix<sub>opt</sub>
3113 decimal-constant:
3114 nonzero-digit
3115 decimal-constant digit
3116 octal-constant:
3117 0
3118 octal-constant octal-digit
3119 hexadecimal-constant:
3120 hexadecimal-prefix hexadecimal-digit
3121 hexadecimal-constant hexadecimal-digit
3122 hexadecimal-prefix: one of
3123 0x 0X
3124 nonzero-digit: one of
3125 1 2 3 4 5 6 7 8 9
3126 octal-digit: one of
3127 0 1 2 3 4 5 6 7
3128 hexadecimal-digit: one of
3129 0 1 2 3 4 5 6 7 8 9
3130 a b c d e f
3131 A B C D E F
3132 integer-suffix:
3133 unsigned-suffix long-suffix<sub>opt</sub>
3134 unsigned-suffix long-long-suffix
3135 long-suffix unsigned-suffix<sub>opt</sub>
3136 long-long-suffix unsigned-suffix<sub>opt</sub>
3137 unsigned-suffix: one of
3138 u U
3139 long-suffix: one of
3140 l L
3141 long-long-suffix: one of
3142 ll LL
3143 </pre>
3144 <p><b>Description</b>
3145 <p><!--para 2 -->
3146 An integer constant begins with a digit, but has no period or exponent part. It may have a
3147 prefix that specifies its base and a suffix that specifies its type.
3148 <p><!--para 3 -->
3149 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3150 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3151 digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
3152 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3153 10 through 15 respectively.
3154 <p><b>Semantics</b>
3155 <p><!--para 4 -->
3156 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
3157 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3158 <p><!--para 5 -->
3159 The type of an integer constant is the first of the corresponding list in which its value can
3160 be represented.
3161 <!--page 68 -->
3162 <table border=1>
3163 <tr><th> Suffix <th>Decimal Constant <th>Octal or Hexadecimal Constant
3164 <tr><td> none
3165 <td><pre>
3166 int
3167 long int
3168 long long int
3169 </pre>
3170 <td><pre>
3171 int
3172 unsigned int
3173 long int
3174 unsigned long int
3175 long long int
3176 unsigned long long int
3177 </pre>
3178 <tr><td> u or U
3179 <td><pre>
3180 unsigned int
3181 unsigned long int
3182 unsigned long long int
3183 </pre>
3184 <td><pre>
3185 unsigned int
3186 unsigned long int
3187 unsigned long long int
3188 </pre>
3189 <tr><td> l or L
3190 <td><pre>
3191 long int
3192 long long int
3193 </pre>
3194 <td><pre>
3195 long int
3196 unsigned long int
3197 long long int
3198 unsigned long long int
3199 </pre>
3200 <tr><td> Both u or U and l or L
3201 <td><pre>
3202 unsigned long int
3203 unsigned long long int
3204 </pre>
3205 <td><pre>
3206 unsigned long int
3207 unsigned long long int
3208 </pre>
3209 <tr><td> ll or LL
3210 <td><pre>
3211 long long int
3212 </pre>
3213 <td><pre>
3214 long long int
3215 unsigned long long int
3216 </pre>
3217 <tr><td> Both u or U and ll or LL
3218 <td><pre>
3219 unsigned long long int
3220 </pre>
3221 <td><pre>
3222 unsigned long long int
3223 </pre>
3224 </table>
3225 <p><!--para 6 -->
3226 If an integer constant cannot be represented by any type in its list, it may have an
3227 extended integer type, if the extended integer type can represent its value. If all of the
3228 types in the list for the constant are signed, the extended integer type shall be signed. If
3229 all of the types in the list for the constant are unsigned, the extended integer type shall be
3230 unsigned. If the list contains both signed and unsigned types, the extended integer type
3231 may be signed or unsigned. If an integer constant cannot be represented by any type in
3232 its list and has no extended integer type, then the integer constant has no type.
3233 <!--page 69 -->
3236 <p><b>Syntax</b>
3237 <p><!--para 1 -->
3238 <!--page 70 -->
3239 <pre>
3240 floating-constant:
3241 decimal-floating-constant
3242 hexadecimal-floating-constant
3243 decimal-floating-constant:
3244 fractional-constant exponent-part<sub>opt</sub> floating-suffix<sub>opt</sub>
3245 digit-sequence exponent-part floating-suffix<sub>opt</sub>
3246 hexadecimal-floating-constant:
3247 hexadecimal-prefix hexadecimal-fractional-constant
3248 binary-exponent-part floating-suffix<sub>opt</sub>
3249 hexadecimal-prefix hexadecimal-digit-sequence
3250 binary-exponent-part floating-suffix<sub>opt</sub>
3251 fractional-constant:
3252 digit-sequence<sub>opt</sub> . digit-sequence
3253 digit-sequence .
3254 exponent-part:
3255 e sign<sub>opt</sub> digit-sequence
3256 E sign<sub>opt</sub> digit-sequence
3257 sign: one of
3258 + -
3259 digit-sequence:
3260 digit
3261 digit-sequence digit
3262 hexadecimal-fractional-constant:
3263 hexadecimal-digit-sequence<sub>opt</sub> .
3264 hexadecimal-digit-sequence
3265 hexadecimal-digit-sequence .
3266 binary-exponent-part:
3267 p sign<sub>opt</sub> digit-sequence
3268 P sign<sub>opt</sub> digit-sequence
3269 hexadecimal-digit-sequence:
3270 hexadecimal-digit
3271 hexadecimal-digit-sequence hexadecimal-digit
3272 floating-suffix: one of
3273 f l F L
3274 </pre>
3275 <p><b>Description</b>
3276 <p><!--para 2 -->
3277 A floating constant has a significand part that may be followed by an exponent part and a
3278 suffix that specifies its type. The components of the significand part may include a digit
3279 sequence representing the whole-number part, followed by a period (.), followed by a
3280 digit sequence representing the fraction part. The components of the exponent part are an
3281 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
3282 Either the whole-number part or the fraction part has to be present; for decimal floating
3283 constants, either the period or the exponent part has to be present.
3284 <p><b>Semantics</b>
3285 <p><!--para 3 -->
3286 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
3287 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
3288 floating constants, the exponent indicates the power of 10 by which the significand part is
3289 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
3290 by which the significand part is to be scaled. For decimal floating constants, and also for
3291 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
3292 the nearest representable value, or the larger or smaller representable value immediately
3293 adjacent to the nearest representable value, chosen in an implementation-defined manner.
3294 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
3295 correctly rounded.
3296 <p><!--para 4 -->
3297 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
3298 type float. If suffixed by the letter l or L, it has type long double.
3299 <p><!--para 5 -->
3300 Floating constants are converted to internal format as if at translation-time. The
3301 conversion of a floating constant shall not raise an exceptional condition or a floating-
3302 point exception at execution time.
3303 <p><b>Recommended practice</b>
3304 <p><!--para 6 -->
3305 The implementation should produce a diagnostic message if a hexadecimal constant
3306 cannot be represented exactly in its evaluation format; the implementation should then
3307 proceed with the translation of the program.
3308 <p><!--para 7 -->
3309 The translation-time conversion of floating constants should match the execution-time
3310 conversion of character strings by library functions, such as strtod, given matching
3311 inputs suitable for both conversions, the same result format, and default execution-time
3317 <!--page 71 -->
3319 <p><b>Footnotes</b>
3320 <p><small><a name="note64" href="#note64">64)</a> The specification for the library functions recommends more accurate conversion than required for
3322 </small>
3325 <p><b>Syntax</b>
3326 <p><!--para 1 -->
3327 <pre>
3328 enumeration-constant:
3329 identifier
3330 </pre>
3331 <p><b>Semantics</b>
3332 <p><!--para 2 -->
3333 An identifier declared as an enumeration constant has type int.
3337 <p><b>Syntax</b>
3338 <p><!--para 1 -->
3339 <!--page 72 -->
3340 <pre>
3341 character-constant:
3342 ' c-char-sequence '
3343 L' c-char-sequence '
3344 c-char-sequence:
3345 c-char
3346 c-char-sequence c-char
3347 c-char:
3348 any member of the source character set except
3349 the single-quote ', backslash \, or new-line character
3350 escape-sequence
3351 escape-sequence:
3352 simple-escape-sequence
3353 octal-escape-sequence
3354 hexadecimal-escape-sequence
3355 universal-character-name
3356 simple-escape-sequence: one of
3357 \' \" \? \\
3358 \a \b \f \n \r \t \v
3359 octal-escape-sequence:
3360 \ octal-digit
3361 \ octal-digit octal-digit
3362 \ octal-digit octal-digit octal-digit
3363 hexadecimal-escape-sequence:
3364 \x hexadecimal-digit
3365 hexadecimal-escape-sequence hexadecimal-digit
3366 </pre>
3369 An integer character constant is a sequence of one or more multibyte characters enclosed
3370 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
3371 letter L. With a few exceptions detailed later, the elements of the sequence are any
3372 members of the source character set; they are mapped in an implementation-defined
3373 manner to members of the execution character set.
3375 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
3376 arbitrary integer values are representable according to the following table of escape
3377 sequences:
3378 <pre>
3379 single quote ' \'
3381 question mark ? \?
3382 backslash \ \\
3383 octal character \octal digits
3384 hexadecimal character \x hexadecimal digits
3385 </pre>
3386 <p><!--para 4 -->
3387 The double-quote " and question-mark ? are representable either by themselves or by the
3388 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
3389 shall be represented, respectively, by the escape sequences \' and \\.
3390 <p><!--para 5 -->
3391 The octal digits that follow the backslash in an octal escape sequence are taken to be part
3392 of the construction of a single character for an integer character constant or of a single
3393 wide character for a wide character constant. The numerical value of the octal integer so
3394 formed specifies the value of the desired character or wide character.
3395 <p><!--para 6 -->
3396 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
3397 sequence are taken to be part of the construction of a single character for an integer
3398 character constant or of a single wide character for a wide character constant. The
3399 numerical value of the hexadecimal integer so formed specifies the value of the desired
3400 character or wide character.
3401 <p><!--para 7 -->
3402 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
3403 constitute the escape sequence.
3404 <p><!--para 8 -->
3405 In addition, characters not in the basic character set are representable by universal
3406 character names and certain nongraphic characters are representable by escape sequences
3407 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
3413 <!--page 73 -->
3414 <p><b>Constraints</b>
3415 <p><!--para 9 -->
3416 The value of an octal or hexadecimal escape sequence shall be in the range of
3417 representable values for the type unsigned char for an integer character constant, or
3418 the unsigned type corresponding to wchar_t for a wide character constant.
3419 <p><b>Semantics</b>
3420 <p><!--para 10 -->
3421 An integer character constant has type int. The value of an integer character constant
3422 containing a single character that maps to a single-byte execution character is the
3423 numerical value of the representation of the mapped character interpreted as an integer.
3424 The value of an integer character constant containing more than one character (e.g.,
3425 'ab'), or containing a character or escape sequence that does not map to a single-byte
3426 execution character, is implementation-defined. If an integer character constant contains
3427 a single character or escape sequence, its value is the one that results when an object with
3428 type char whose value is that of the single character or escape sequence is converted to
3429 type int.
3430 <p><!--para 11 -->
3431 A wide character constant has type wchar_t, an integer type defined in the
3432 <a href="#7.17"><stddef.h></a> header. The value of a wide character constant containing a single
3433 multibyte character that maps to a member of the extended execution character set is the
3434 wide character corresponding to that multibyte character, as defined by the mbtowc
3435 function, with an implementation-defined current locale. The value of a wide character
3436 constant containing more than one multibyte character, or containing a multibyte
3437 character or escape sequence not represented in the extended execution character set, is
3438 implementation-defined.
3439 <p><!--para 12 -->
3440 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
3442 <p><!--para 13 -->
3443 EXAMPLE 2 Consider implementations that use two's-complement representation for integers and eight
3444 bits for objects that have type char. In an implementation in which type char has the same range of
3445 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
3446 same range of values as unsigned char, the character constant '\xFF' has the value +255.
3448 <p><!--para 14 -->
3449 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
3450 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
3451 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
3452 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
3453 escape sequence is terminated after three octal digits. (The value of this two-character integer character
3454 constant is implementation-defined.)
3456 <p><!--para 15 -->
3457 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
3458 L'\1234' specifies the implementation-defined value that results from the combination of the values
3459 0123 and '4'.
3461 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbtowc function
3463 <!--page 74 -->
3465 <p><b>Footnotes</b>
3466 <p><small><a name="note65" href="#note65">65)</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,
3467 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
3468 </small>
3471 <p><b>Syntax</b>
3472 <p><!--para 1 -->
3473 <pre>
3474 string-literal:
3477 s-char-sequence:
3478 s-char
3479 s-char-sequence s-char
3480 s-char:
3481 any member of the source character set except
3482 the double-quote ", backslash \, or new-line character
3483 escape-sequence
3484 </pre>
3487 A character string literal is a sequence of zero or more multibyte characters enclosed in
3488 double-quotes, as in "xyz". A wide string literal is the same, except prefixed by the
3489 letter L.
3491 The same considerations apply to each element of the sequence in a character string
3492 literal or a wide string literal as if it were in an integer character constant or a wide
3493 character constant, except that the single-quote ' is representable either by itself or by the
3494 escape sequence \', but the double-quote " shall be represented by the escape sequence
3495 \".
3498 In translation phase 6, the multibyte character sequences specified by any sequence of
3499 adjacent character and wide string literal tokens are concatenated into a single multibyte
3500 character sequence. If any of the tokens are wide string literal tokens, the resulting
3501 multibyte character sequence is treated as a wide string literal; otherwise, it is treated as a
3502 character string literal.
3504 In translation phase 7, a byte or code of value zero is appended to each multibyte
3505 character sequence that results from a string literal or literals.<sup><a href="#note66"><b>66)</b></a></sup> The multibyte character
3506 sequence is then used to initialize an array of static storage duration and length just
3507 sufficient to contain the sequence. For character string literals, the array elements have
3508 type char, and are initialized with the individual bytes of the multibyte character
3509 sequence; for wide string literals, the array elements have type wchar_t, and are
3510 initialized with the sequence of wide characters corresponding to the multibyte character
3512 <!--page 75 -->
3513 sequence, as defined by the mbstowcs function with an implementation-defined current
3514 locale. The value of a string literal containing a multibyte character or escape sequence
3515 not represented in the execution character set is implementation-defined.
3517 It is unspecified whether these arrays are distinct provided their elements have the
3518 appropriate values. If the program attempts to modify such an array, the behavior is
3519 undefined.
3521 EXAMPLE This pair of adjacent character string literals
3522 <pre>
3524 </pre>
3525 produces a single character string literal containing the two characters whose values are '\x12' and '3',
3526 because escape sequences are converted into single members of the execution character set just prior to
3527 adjacent string literal concatenation.
3529 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbstowcs
3533 <p><small><a name="note66" href="#note66">66)</a> A character 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
3534 it by a \0 escape sequence.
3535 </small>
3540 <pre>
3541 punctuator: one of
3542 [ ] ( ) { } . ->
3543 ++ -- & * + - ~ !
3545 ? : ; ...
3547 , # ##
3549 </pre>
3552 A punctuator is a symbol that has independent syntactic and semantic significance.
3553 Depending on context, it may specify an operation to be performed (which in turn may
3554 yield a value or a function designator, produce a side effect, or some combination thereof)
3555 in which case it is known as an operator (other forms of operator also exist in some
3556 contexts). An operand is an entity on which an operator acts.
3557 <!--page 76 -->
3560 <pre>
3562 </pre>
3563 behave, respectively, the same as the six tokens
3564 <pre>
3565 [ ] { } # ##
3566 </pre>
3568 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
3572 <p><small><a name="note67" href="#note67">67)</a> These tokens are sometimes called ''digraphs''.
3573 </small>
3574 <p><small><a name="note68" href="#note68">68)</a> Thus [ and <: behave differently when ''stringized'' (see <a href="#6.10.3.2">6.10.3.2</a>), but can otherwise be freely
3575 interchanged.
3576 </small>
3581 <pre>
3582 header-name:
3584 " q-char-sequence "
3585 h-char-sequence:
3586 h-char
3587 h-char-sequence h-char
3588 h-char:
3589 any member of the source character set except
3590 the new-line character and >
3591 q-char-sequence:
3592 q-char
3593 q-char-sequence q-char
3594 q-char:
3595 any member of the source character set except
3596 the new-line character and "
3597 </pre>
3598 <p><b>Semantics</b>
3599 <p><!--para 2 -->
3600 The sequences in both forms of header names are mapped in an implementation-defined
3602 <p><!--para 3 -->
3603 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
3604 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
3609 <!--page 77 -->
3610 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note69"><b>69)</b></a></sup> Header name
3611 preprocessing tokens are recognized only within #include preprocessing directives and
3612 in implementation-defined locations within #pragma directives.<sup><a href="#note70"><b>70)</b></a></sup>
3613 <p><!--para 4 -->
3614 EXAMPLE The following sequence of characters:
3615 <pre>
3616 0x3<1/a.h>1e2
3617 #include <1/a.h>
3618 #define const.member@$
3619 </pre>
3620 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
3621 by a { on the left and a } on the right).
3622 <pre>
3623 {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
3624 {#}{include} {<1/a.h>}
3625 {#}{define} {const}{.}{member}{@}{$}
3626 </pre>
3630 <p><b>Footnotes</b>
3631 <p><small><a name="note69" href="#note69">69)</a> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
3632 </small>
3633 <p><small><a name="note70" href="#note70">70)</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>.
3634 </small>
3637 <p><b>Syntax</b>
3638 <p><!--para 1 -->
3639 <pre>
3640 pp-number:
3641 digit
3642 . digit
3643 pp-number digit
3644 pp-number identifier-nondigit
3645 pp-number e sign
3646 pp-number E sign
3647 pp-number p sign
3648 pp-number P sign
3649 pp-number .
3650 </pre>
3651 <p><b>Description</b>
3652 <p><!--para 2 -->
3653 A preprocessing number begins with a digit optionally preceded by a period (.) and may
3654 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
3655 p+, p-, P+, or P-.
3656 <p><!--para 3 -->
3657 Preprocessing number tokens lexically include all floating and integer constant tokens.
3658 <p><b>Semantics</b>
3659 <p><!--para 4 -->
3660 A preprocessing number does not have type or a value; it acquires both after a successful
3661 conversion (as part of translation phase 7) to a floating constant token or an integer
3662 constant token.
3665 <!--page 78 -->
3668 <p><!--para 1 -->
3669 Except within a character constant, a string literal, or a comment, the characters /*
3670 introduce a comment. The contents of such a comment are examined only to identify
3671 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note71"><b>71)</b></a></sup>
3672 <p><!--para 2 -->
3673 Except within a character constant, a string literal, or a comment, the characters //
3674 introduce a comment that includes all multibyte characters up to, but not including, the
3675 next new-line character. The contents of such a comment are examined only to identify
3676 multibyte characters and to find the terminating new-line character.
3677 <p><!--para 3 -->
3678 EXAMPLE
3679 <pre>
3682 // */ // comment, not syntax error
3683 f = g/**//h; // equivalent to f = g / h;
3684 //\
3685 i(); // part of a two-line comment
3686 /\
3687 / j(); // part of a two-line comment
3688 #define glue(x,y) x##y
3689 glue(/,/) k(); // syntax error, not comment
3690 /*//*/ l(); // equivalent to l();
3691 m = n//**/o
3692 + p; // equivalent to m = n + p;
3693 </pre>
3698 <!--page 79 -->
3700 <p><b>Footnotes</b>
3702 </small>
3705 <p><!--para 1 -->
3706 An expression is a sequence of operators and operands that specifies computation of a
3707 value, or that designates an object or a function, or that generates side effects, or that
3708 performs a combination thereof.
3709 <p><!--para 2 -->
3710 Between the previous and next sequence point an object shall have its stored value
3711 modified at most once by the evaluation of an expression.<sup><a href="#note72"><b>72)</b></a></sup> Furthermore, the prior value
3712 shall be read only to determine the value to be stored.<sup><a href="#note73"><b>73)</b></a></sup>
3713 <p><!--para 3 -->
3714 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note74"><b>74)</b></a></sup> Except as specified
3715 later (for the function-call (), &&, ||, ?:, and comma operators), the order of evaluation
3716 of subexpressions and the order in which side effects take place are both unspecified.
3717 <p><!--para 4 -->
3718 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
3719 collectively described as bitwise operators) are required to have operands that have
3720 integer type. These operators yield values that depend on the internal representations of
3721 integers, and have implementation-defined and undefined aspects for signed types.
3722 <p><!--para 5 -->
3723 If an exceptional condition occurs during the evaluation of an expression (that is, if the
3724 result is not mathematically defined or not in the range of representable values for its
3725 type), the behavior is undefined.
3726 <p><!--para 6 -->
3727 The effective type of an object for an access to its stored value is the declared type of the
3728 object, if any.<sup><a href="#note75"><b>75)</b></a></sup> If a value is stored into an object having no declared type through an
3729 lvalue having a type that is not a character type, then the type of the lvalue becomes the
3732 <!--page 80 -->
3733 effective type of the object for that access and for subsequent accesses that do not modify
3734 the stored value. If a value is copied into an object having no declared type using
3735 memcpy or memmove, or is copied as an array of character type, then the effective type
3736 of the modified object for that access and for subsequent accesses that do not modify the
3737 value is the effective type of the object from which the value is copied, if it has one. For
3738 all other accesses to an object having no declared type, the effective type of the object is
3739 simply the type of the lvalue used for the access.
3740 <p><!--para 7 -->
3741 An object shall have its stored value accessed only by an lvalue expression that has one of
3743 <ul>
3744 <li> a type compatible with the effective type of the object,
3745 <li> a qualified version of a type compatible with the effective type of the object,
3746 <li> a type that is the signed or unsigned type corresponding to the effective type of the
3747 object,
3748 <li> a type that is the signed or unsigned type corresponding to a qualified version of the
3749 effective type of the object,
3750 <li> an aggregate or union type that includes one of the aforementioned types among its
3751 members (including, recursively, a member of a subaggregate or contained union), or
3752 <li> a character type.
3753 </ul>
3754 <p><!--para 8 -->
3755 A floating expression may be contracted, that is, evaluated as though it were an atomic
3756 operation, thereby omitting rounding errors implied by the source code and the
3757 expression evaluation method.<sup><a href="#note77"><b>77)</b></a></sup> The FP_CONTRACT pragma in <a href="#7.12"><math.h></a> provides a
3758 way to disallow contracted expressions. Otherwise, whether and how expressions are
3760 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), copying functions (<a href="#7.21.2">7.21.2</a>).
3765 <!--page 81 -->
3767 <p><b>Footnotes</b>
3768 <p><small><a name="note72" href="#note72">72)</a> A floating-point status flag is not an object and can be set more than once within an expression.
3769 </small>
3770 <p><small><a name="note73" href="#note73">73)</a> This paragraph renders undefined statement expressions such as
3772 <pre>
3773 i = ++i + 1;
3774 a[i++] = i;
3775 </pre>
3776 while allowing
3777 <pre>
3778 i = i + 1;
3779 a[i] = i;
3780 </pre>
3782 </small>
3783 <p><small><a name="note74" href="#note74">74)</a> The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
3784 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
3785 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
3786 <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
3787 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
3788 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
3791 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
3792 indicated in each subclause by the syntax for the expressions discussed therein.
3793 </small>
3795 </small>
3796 <p><small><a name="note76" href="#note76">76)</a> The intent of this list is to specify those circumstances in which an object may or may not be aliased.
3797 </small>
3798 <p><small><a name="note77" href="#note77">77)</a> A contracted expression might also omit the raising of floating-point exceptions.
3799 </small>
3800 <p><small><a name="note78" href="#note78">78)</a> This license is specifically intended to allow implementations to exploit fast machine instructions that
3801 combine multiple C operators. As contractions potentially undermine predictability, and can even
3802 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
3803 documented.
3804 </small>
3807 <p><b>Syntax</b>
3808 <p><!--para 1 -->
3809 <pre>
3810 primary-expression:
3811 identifier
3812 constant
3813 string-literal
3814 ( expression )
3815 </pre>
3816 <p><b>Semantics</b>
3817 <p><!--para 2 -->
3818 An identifier is a primary expression, provided it has been declared as designating an
3819 object (in which case it is an lvalue) or a function (in which case it is a function
3821 <p><!--para 3 -->
3822 A constant is a primary expression. Its type depends on its form and value, as detailed in
3824 <p><!--para 4 -->
3825 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>.
3826 <p><!--para 5 -->
3827 A parenthesized expression is a primary expression. Its type and value are identical to
3828 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
3829 expression if the unparenthesized expression is, respectively, an lvalue, a function
3830 designator, or a void expression.
3833 <p><b>Footnotes</b>
3834 <p><small><a name="note79" href="#note79">79)</a> Thus, an undeclared identifier is a violation of the syntax.
3835 </small>
3838 <p><b>Syntax</b>
3839 <p><!--para 1 -->
3840 <pre>
3841 postfix-expression:
3842 primary-expression
3843 postfix-expression [ expression ]
3844 postfix-expression ( argument-expression-list<sub>opt</sub> )
3845 postfix-expression . identifier
3846 postfix-expression -> identifier
3847 postfix-expression ++
3848 postfix-expression --
3849 ( type-name ) { initializer-list }
3850 ( type-name ) { initializer-list , }
3851 </pre>
3856 <!--page 82 -->
3857 <pre>
3858 argument-expression-list:
3859 assignment-expression
3860 argument-expression-list , assignment-expression
3861 </pre>
3864 <p><b>Constraints</b>
3865 <p><!--para 1 -->
3866 One of the expressions shall have type ''pointer to object type'', the other expression shall
3867 have integer type, and the result has type ''type''.
3868 <p><b>Semantics</b>
3869 <p><!--para 2 -->
3870 A postfix expression followed by an expression in square brackets [] is a subscripted
3871 designation of an element of an array object. The definition of the subscript operator []
3872 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
3873 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
3874 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
3875 element of E1 (counting from zero).
3876 <p><!--para 3 -->
3877 Successive subscript operators designate an element of a multidimensional array object.
3878 If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
3879 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
3880 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
3881 implicitly as a result of subscripting, the result is the pointed-to (n - 1)-dimensional array,
3882 which itself is converted into a pointer if used as other than an lvalue. It follows from this
3883 that arrays are stored in row-major order (last subscript varies fastest).
3884 <p><!--para 4 -->
3885 EXAMPLE Consider the array object defined by the declaration
3886 <pre>
3887 int x[3][5];
3888 </pre>
3889 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
3890 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
3891 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
3892 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
3893 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
3894 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
3895 yields an int.
3897 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
3899 <!--page 83 -->
3902 <p><b>Constraints</b>
3903 <p><!--para 1 -->
3904 The expression that denotes the called function<sup><a href="#note80"><b>80)</b></a></sup> shall have type pointer to function
3905 returning void or returning an object type other than an array type.
3906 <p><!--para 2 -->
3907 If the expression that denotes the called function has a type that includes a prototype, the
3908 number of arguments shall agree with the number of parameters. Each argument shall
3909 have a type such that its value may be assigned to an object with the unqualified version
3910 of the type of its corresponding parameter.
3911 <p><b>Semantics</b>
3912 <p><!--para 3 -->
3913 A postfix expression followed by parentheses () containing a possibly empty, comma-
3914 separated list of expressions is a function call. The postfix expression denotes the called
3915 function. The list of expressions specifies the arguments to the function.
3916 <p><!--para 4 -->
3917 An argument may be an expression of any object type. In preparing for the call to a
3918 function, the arguments are evaluated, and each parameter is assigned the value of the
3920 <p><!--para 5 -->
3921 If the expression that denotes the called function has type pointer to function returning an
3922 object type, the function call expression has the same type as that object type, and has the
3923 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void. If
3924 an attempt is made to modify the result of a function call or to access it after the next
3925 sequence point, the behavior is undefined.
3926 <p><!--para 6 -->
3927 If the expression that denotes the called function has a type that does not include a
3928 prototype, the integer promotions are performed on each argument, and arguments that
3929 have type float are promoted to double. These are called the default argument
3930 promotions. If the number of arguments does not equal the number of parameters, the
3931 behavior is undefined. If the function is defined with a type that includes a prototype, and
3932 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
3933 promotion are not compatible with the types of the parameters, the behavior is undefined.
3934 If the function is defined with a type that does not include a prototype, and the types of
3935 the arguments after promotion are not compatible with those of the parameters after
3936 promotion, the behavior is undefined, except for the following cases:
3941 <!--page 84 -->
3942 <ul>
3943 <li> one promoted type is a signed integer type, the other promoted type is the
3944 corresponding unsigned integer type, and the value is representable in both types;
3945 <li> both types are pointers to qualified or unqualified versions of a character type or
3946 void.
3947 </ul>
3948 <p><!--para 7 -->
3949 If the expression that denotes the called function has a type that does include a prototype,
3950 the arguments are implicitly converted, as if by assignment, to the types of the
3951 corresponding parameters, taking the type of each parameter to be the unqualified version
3952 of its declared type. The ellipsis notation in a function prototype declarator causes
3953 argument type conversion to stop after the last declared parameter. The default argument
3954 promotions are performed on trailing arguments.
3955 <p><!--para 8 -->
3956 No other conversions are performed implicitly; in particular, the number and types of
3957 arguments are not compared with those of the parameters in a function definition that
3958 does not include a function prototype declarator.
3959 <p><!--para 9 -->
3960 If the function is defined with a type that is not compatible with the type (of the
3961 expression) pointed to by the expression that denotes the called function, the behavior is
3962 undefined.
3963 <p><!--para 10 -->
3964 The order of evaluation of the function designator, the actual arguments, and
3965 subexpressions within the actual arguments is unspecified, but there is a sequence point
3966 before the actual call.
3967 <p><!--para 11 -->
3968 Recursive function calls shall be permitted, both directly and indirectly through any chain
3969 of other functions.
3970 <p><!--para 12 -->
3971 EXAMPLE In the function call
3972 <pre>
3973 (*pf[f1()]) (f2(), f3() + f4())
3974 </pre>
3975 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
3976 the function pointed to by pf[f1()] is called.
3978 <p><b> Forward references</b>: function declarators (including prototypes) (<a href="#6.7.5.3">6.7.5.3</a>), function
3979 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>).
3981 <p><b>Footnotes</b>
3982 <p><small><a name="note80" href="#note80">80)</a> Most often, this is the result of converting an identifier that is a function designator.
3983 </small>
3984 <p><small><a name="note81" href="#note81">81)</a> A function may change the values of its parameters, but these changes cannot affect the values of the
3985 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
3986 change the value of the object pointed to. A parameter declared to have array or function type is
3988 </small>
3991 <p><b>Constraints</b>
3992 <p><!--para 1 -->
3993 The first operand of the . operator shall have a qualified or unqualified structure or union
3994 type, and the second operand shall name a member of that type.
3995 <p><!--para 2 -->
3996 The first operand of the -> operator shall have type ''pointer to qualified or unqualified
3997 structure'' or ''pointer to qualified or unqualified union'', and the second operand shall
3998 name a member of the type pointed to.
3999 <!--page 85 -->
4000 <p><b>Semantics</b>
4001 <p><!--para 3 -->
4002 A postfix expression followed by the . operator and an identifier designates a member of
4003 a structure or union object. The value is that of the named member,<sup><a href="#note82"><b>82)</b></a></sup> and is an lvalue if
4004 the first expression is an lvalue. If the first expression has qualified type, the result has
4005 the so-qualified version of the type of the designated member.
4006 <p><!--para 4 -->
4007 A postfix expression followed by the -> operator and an identifier designates a member
4008 of a structure or union object. The value is that of the named member of the object to
4009 which the first expression points, and is an lvalue.<sup><a href="#note83"><b>83)</b></a></sup> If the first expression is a pointer to
4010 a qualified type, the result has the so-qualified version of the type of the designated
4011 member.
4012 <p><!--para 5 -->
4013 One special guarantee is made in order to simplify the use of unions: if a union contains
4014 several structures that share a common initial sequence (see below), and if the union
4015 object currently contains one of these structures, it is permitted to inspect the common
4016 initial part of any of them anywhere that a declaration of the complete type of the union is
4017 visible. Two structures share a common initial sequence if corresponding members have
4018 compatible types (and, for bit-fields, the same widths) for a sequence of one or more
4019 initial members.
4020 <p><!--para 6 -->
4021 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
4022 union, f().x is a valid postfix expression but is not an lvalue.
4024 <p><!--para 7 -->
4025 EXAMPLE 2 In:
4026 <pre>
4027 struct s { int i; const int ci; };
4028 struct s s;
4029 const struct s cs;
4030 volatile struct s vs;
4031 </pre>
4032 the various members have the types:
4033 <pre>
4034 s.i int
4035 s.ci const int
4036 cs.i const int
4037 cs.ci const int
4038 vs.i volatile int
4039 vs.ci volatile const int
4040 </pre>
4045 <!--page 86 -->
4046 <p><!--para 8 -->
4047 EXAMPLE 3 The following is a valid fragment:
4048 <pre>
4049 union {
4050 struct {
4051 int alltypes;
4052 } n;
4053 struct {
4054 int type;
4055 int intnode;
4056 } ni;
4057 struct {
4058 int type;
4059 double doublenode;
4060 } nf;
4061 } u;
4062 u.nf.type = 1;
4064 /* ... */
4065 if (u.n.alltypes == 1)
4066 if (sin(u.nf.doublenode) == 0.0)
4067 /* ... */
4068 </pre>
4069 The following is not a valid fragment (because the union type is not visible within function f):
4070 <pre>
4071 struct t1 { int m; };
4072 struct t2 { int m; };
4073 int f(struct t1 *p1, struct t2 *p2)
4074 {
4075 if (p1->m < 0)
4076 p2->m = -p2->m;
4077 return p1->m;
4078 }
4079 int g()
4080 {
4081 union {
4082 struct t1 s1;
4083 struct t2 s2;
4084 } u;
4085 /* ... */
4086 return f(&u.s1, &u.s2);
4087 }
4088 </pre>
4090 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
4092 <!--page 87 -->
4094 <p><b>Footnotes</b>
4095 <p><small><a name="note82" href="#note82">82)</a> If the member used to access the contents of a union object is not the same as the member last used to
4096 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
4097 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
4098 punning"). This might be a trap representation.
4099 </small>
4100 <p><small><a name="note83" href="#note83">83)</a> If &E is a valid pointer expression (where & is the ''address-of '' operator, which generates a pointer to
4101 its operand), the expression (&E)->MOS is the same as E.MOS.
4102 </small>
4104 <h5><a name="6.5.2.4" href="#6.5.2.4">6.5.2.4 Postfix increment and decrement operators</a></h5>
4105 <p><b>Constraints</b>
4106 <p><!--para 1 -->
4107 The operand of the postfix increment or decrement operator shall have qualified or
4108 unqualified real or pointer type and shall be a modifiable lvalue.
4109 <p><b>Semantics</b>
4110 <p><!--para 2 -->
4111 The result of the postfix ++ operator is the value of the operand. After the result is
4112 obtained, the value of the operand is incremented. (That is, the value 1 of the appropriate
4113 type is added to it.) See the discussions of additive operators and compound assignment
4114 for information on constraints, types, and conversions and the effects of operations on
4115 pointers. The side effect of updating the stored value of the operand shall occur between
4116 the previous and the next sequence point.
4117 <p><!--para 3 -->
4118 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
4119 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
4120 it).
4121 <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>).
4124 <p><b>Constraints</b>
4125 <p><!--para 1 -->
4126 The type name shall specify an object type or an array of unknown size, but not a variable
4127 length array type.
4128 <p><!--para 2 -->
4129 No initializer shall attempt to provide a value for an object not contained within the entire
4130 unnamed object specified by the compound literal.
4131 <p><!--para 3 -->
4132 If the compound literal occurs outside the body of a function, the initializer list shall
4133 consist of constant expressions.
4134 <p><b>Semantics</b>
4135 <p><!--para 4 -->
4136 A postfix expression that consists of a parenthesized type name followed by a brace-
4137 enclosed list of initializers is a compound literal. It provides an unnamed object whose
4139 <p><!--para 5 -->
4140 If the type name specifies an array of unknown size, the size is determined by the
4141 initializer list as specified in <a href="#6.7.8">6.7.8</a>, and the type of the compound literal is that of the
4142 completed array type. Otherwise (when the type name specifies an object type), the type
4143 of the compound literal is that specified by the type name. In either case, the result is an
4144 lvalue.
4147 <!--page 88 -->
4148 <p><!--para 6 -->
4149 The value of the compound literal is that of an unnamed object initialized by the
4150 initializer list. If the compound literal occurs outside the body of a function, the object
4151 has static storage duration; otherwise, it has automatic storage duration associated with
4152 the enclosing block.
4153 <p><!--para 7 -->
4154 All the semantic rules and constraints for initializer lists in <a href="#6.7.8">6.7.8</a> are applicable to
4156 <p><!--para 8 -->
4157 String literals, and compound literals with const-qualified types, need not designate
4159 <p><!--para 9 -->
4160 EXAMPLE 1 The file scope definition
4161 <pre>
4162 int *p = (int []){2, 4};
4163 </pre>
4164 initializes p to point to the first element of an array of two ints, the first having the value two and the
4165 second, four. The expressions in this compound literal are required to be constant. The unnamed object
4166 has static storage duration.
4168 <p><!--para 10 -->
4169 EXAMPLE 2 In contrast, in
4170 <pre>
4171 void f(void)
4172 {
4173 int *p;
4174 /*...*/
4175 p = (int [2]){*p};
4176 /*...*/
4177 }
4178 </pre>
4179 p is assigned the address of the first element of an array of two ints, the first having the value previously
4180 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
4181 unnamed object has automatic storage duration.
4183 <p><!--para 11 -->
4184 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
4185 created using compound literals can be passed to functions without depending on member order:
4186 <pre>
4187 drawline((struct point){.x=1, .y=1},
4188 (struct point){.x=3, .y=4});
4189 </pre>
4190 Or, if drawline instead expected pointers to struct point:
4191 <pre>
4192 drawline(&(struct point){.x=1, .y=1},
4193 &(struct point){.x=3, .y=4});
4194 </pre>
4196 <p><!--para 12 -->
4197 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
4198 <pre>
4199 (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
4200 </pre>
4205 <!--page 89 -->
4206 <p><!--para 13 -->
4207 EXAMPLE 5 The following three expressions have different meanings:
4208 <pre>
4212 </pre>
4213 The first always has static storage duration and has type array of char, but need not be modifiable; the last
4214 two have automatic storage duration when they occur within the body of a function, and the first of these
4215 two is modifiable.
4217 <p><!--para 14 -->
4218 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
4219 and can even be shared. For example,
4220 <pre>
4222 </pre>
4223 might yield 1 if the literals' storage is shared.
4225 <p><!--para 15 -->
4226 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
4227 linked object. For example, there is no way to write a self-referential compound literal that could be used
4228 as the function argument in place of the named object endless_zeros below:
4229 <pre>
4230 struct int_list { int car; struct int_list *cdr; };
4231 struct int_list endless_zeros = {0, &endless_zeros};
4232 eval(endless_zeros);
4233 </pre>
4235 <p><!--para 16 -->
4236 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
4237 <pre>
4238 struct s { int i; };
4239 int f (void)
4240 {
4241 struct s *p = 0, *q;
4242 int j = 0;
4243 again:
4244 q = p, p = &((struct s){ j++ });
4245 if (j < 2) goto again;
4246 return p == q && q->i == 1;
4247 }
4248 </pre>
4249 The function f() always returns the value 1.
4250 <p><!--para 17 -->
4251 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
4252 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
4253 have an indeterminate value, which would result in undefined behavior.
4255 <p><b> Forward references</b>: type names (<a href="#6.7.6">6.7.6</a>), initialization (<a href="#6.7.8">6.7.8</a>).
4256 <!--page 90 -->
4258 <p><b>Footnotes</b>
4259 <p><small><a name="note84" href="#note84">84)</a> Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
4260 or void only, and the result of a cast expression is not an lvalue.
4261 </small>
4262 <p><small><a name="note85" href="#note85">85)</a> For example, subobjects without explicit initializers are initialized to zero.
4263 </small>
4264 <p><small><a name="note86" href="#note86">86)</a> This allows implementations to share storage for string literals and constant compound literals with
4265 the same or overlapping representations.
4266 </small>
4269 <p><b>Syntax</b>
4270 <p><!--para 1 -->
4271 <pre>
4272 unary-expression:
4273 postfix-expression
4274 ++ unary-expression
4275 -- unary-expression
4276 unary-operator cast-expression
4277 sizeof unary-expression
4278 sizeof ( type-name )
4279 unary-operator: one of
4280 & * + - ~ !
4281 </pre>
4283 <h5><a name="6.5.3.1" href="#6.5.3.1">6.5.3.1 Prefix increment and decrement operators</a></h5>
4284 <p><b>Constraints</b>
4285 <p><!--para 1 -->
4286 The operand of the prefix increment or decrement operator shall have qualified or
4287 unqualified real or pointer type and shall be a modifiable lvalue.
4288 <p><b>Semantics</b>
4289 <p><!--para 2 -->
4290 The value of the operand of the prefix ++ operator is incremented. The result is the new
4291 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
4292 See the discussions of additive operators and compound assignment for information on
4293 constraints, types, side effects, and conversions and the effects of operations on pointers.
4294 <p><!--para 3 -->
4295 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
4296 operand is decremented.
4297 <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>).
4300 <p><b>Constraints</b>
4301 <p><!--para 1 -->
4302 The operand of the unary & operator shall be either a function designator, the result of a
4303 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
4304 not declared with the register storage-class specifier.
4305 <p><!--para 2 -->
4306 The operand of the unary * operator shall have pointer type.
4307 <p><b>Semantics</b>
4308 <p><!--para 3 -->
4309 The unary & operator yields the address of its operand. If the operand has type ''type'',
4310 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
4311 neither that operator nor the & operator is evaluated and the result is as if both were
4312 omitted, except that the constraints on the operators still apply and the result is not an
4313 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
4314 <!--page 91 -->
4315 the unary * that is implied by the [] is evaluated and the result is as if the & operator
4316 were removed and the [] operator were changed to a + operator. Otherwise, the result is
4317 a pointer to the object or function designated by its operand.
4318 <p><!--para 4 -->
4319 The unary * operator denotes indirection. If the operand points to a function, the result is
4320 a function designator; if it points to an object, the result is an lvalue designating the
4321 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
4322 invalid value has been assigned to the pointer, the behavior of the unary * operator is
4324 <p><b> Forward references</b>: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
4327 <p><b>Footnotes</b>
4328 <p><small><a name="note87" href="#note87">87)</a> Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is
4329 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
4330 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
4331 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
4332 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
4333 address inappropriately aligned for the type of object pointed to, and the address of an object after the
4334 end of its lifetime.
4335 </small>
4338 <p><b>Constraints</b>
4339 <p><!--para 1 -->
4340 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
4341 integer type; of the ! operator, scalar type.
4342 <p><b>Semantics</b>
4343 <p><!--para 2 -->
4344 The result of the unary + operator is the value of its (promoted) operand. The integer
4345 promotions are performed on the operand, and the result has the promoted type.
4346 <p><!--para 3 -->
4347 The result of the unary - operator is the negative of its (promoted) operand. The integer
4348 promotions are performed on the operand, and the result has the promoted type.
4349 <p><!--para 4 -->
4350 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
4351 each bit in the result is set if and only if the corresponding bit in the converted operand is
4352 not set). The integer promotions are performed on the operand, and the result has the
4353 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
4354 to the maximum value representable in that type minus E.
4355 <p><!--para 5 -->
4356 The result of the logical negation operator ! is 0 if the value of its operand compares
4357 unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
4358 The expression !E is equivalent to (0==E).
4363 <!--page 92 -->
4366 <p><b>Constraints</b>
4367 <p><!--para 1 -->
4368 The sizeof operator shall not be applied to an expression that has function type or an
4369 incomplete type, to the parenthesized name of such a type, or to an expression that
4370 designates a bit-field member.
4371 <p><b>Semantics</b>
4372 <p><!--para 2 -->
4373 The sizeof operator yields the size (in bytes) of its operand, which may be an
4374 expression or the parenthesized name of a type. The size is determined from the type of
4375 the operand. The result is an integer. If the type of the operand is a variable length array
4376 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
4377 integer constant.
4378 <p><!--para 3 -->
4379 When applied to an operand that has type char, unsigned char, or signed char,
4380 (or a qualified version thereof) the result is 1. When applied to an operand that has array
4381 type, the result is the total number of bytes in the array.<sup><a href="#note88"><b>88)</b></a></sup> When applied to an operand
4382 that has structure or union type, the result is the total number of bytes in such an object,
4383 including internal and trailing padding.
4384 <p><!--para 4 -->
4385 The value of the result is implementation-defined, and its type (an unsigned integer type)
4387 <p><!--para 5 -->
4388 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
4389 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
4390 allocate and return a pointer to void. For example:
4391 <pre>
4392 extern void *alloc(size_t);
4393 double *dp = alloc(sizeof *dp);
4394 </pre>
4395 The implementation of the alloc function should ensure that its return value is aligned suitably for
4396 conversion to a pointer to double.
4398 <p><!--para 6 -->
4399 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
4400 <pre>
4401 sizeof array / sizeof array[0]
4402 </pre>
4404 <p><!--para 7 -->
4405 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
4406 function:
4407 <pre>
4409 size_t fsize3(int n)
4410 {
4411 char b[n+3]; // variable length array
4412 return sizeof b; // execution time sizeof
4413 }
4414 </pre>
4418 <!--page 93 -->
4419 <pre>
4420 int main()
4421 {
4422 size_t size;
4423 size = fsize3(10); // fsize3 returns 13
4424 return 0;
4425 }
4426 </pre>
4428 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), declarations (<a href="#6.7">6.7</a>),
4429 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), type names (<a href="#6.7.6">6.7.6</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>).
4431 <p><b>Footnotes</b>
4432 <p><small><a name="note88" href="#note88">88)</a> When applied to a parameter declared to have array or function type, the sizeof operator yields the
4434 </small>
4437 <p><b>Syntax</b>
4438 <p><!--para 1 -->
4439 <pre>
4440 cast-expression:
4441 unary-expression
4442 ( type-name ) cast-expression
4443 </pre>
4444 <p><b>Constraints</b>
4445 <p><!--para 2 -->
4446 Unless the type name specifies a void type, the type name shall specify qualified or
4447 unqualified scalar type and the operand shall have scalar type.
4448 <p><!--para 3 -->
4449 Conversions that involve pointers, other than where permitted by the constraints of
4451 <p><b>Semantics</b>
4452 <p><!--para 4 -->
4453 Preceding an expression by a parenthesized type name converts the value of the
4454 expression to the named type. This construction is called a cast.<sup><a href="#note89"><b>89)</b></a></sup> A cast that specifies
4455 no conversion has no effect on the type or value of an expression.
4456 <p><!--para 5 -->
4457 If the value of the expression is represented with greater precision or range than required
4458 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
4459 type of the expression is the same as the named type.
4460 <p><b> Forward references</b>: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
4461 prototypes) (<a href="#6.7.5.3">6.7.5.3</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>), type names (<a href="#6.7.6">6.7.6</a>).
4466 <!--page 94 -->
4468 <p><b>Footnotes</b>
4469 <p><small><a name="note89" href="#note89">89)</a> A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
4470 unqualified version of the type.
4471 </small>
4474 <p><b>Syntax</b>
4475 <p><!--para 1 -->
4476 <pre>
4477 multiplicative-expression:
4478 cast-expression
4479 multiplicative-expression * cast-expression
4480 multiplicative-expression / cast-expression
4481 multiplicative-expression % cast-expression
4482 </pre>
4483 <p><b>Constraints</b>
4484 <p><!--para 2 -->
4485 Each of the operands shall have arithmetic type. The operands of the % operator shall
4486 have integer type.
4487 <p><b>Semantics</b>
4488 <p><!--para 3 -->
4489 The usual arithmetic conversions are performed on the operands.
4490 <p><!--para 4 -->
4491 The result of the binary * operator is the product of the operands.
4492 <p><!--para 5 -->
4493 The result of the / operator is the quotient from the division of the first operand by the
4494 second; the result of the % operator is the remainder. In both operations, if the value of
4495 the second operand is zero, the behavior is undefined.
4496 <p><!--para 6 -->
4497 When integers are divided, the result of the / operator is the algebraic quotient with any
4498 fractional part discarded.<sup><a href="#note90"><b>90)</b></a></sup> If the quotient a/b is representable, the expression
4499 (a/b)*b + a%b shall equal a.
4501 <p><b>Footnotes</b>
4502 <p><small><a name="note90" href="#note90">90)</a> This is often called ''truncation toward zero''.
4503 </small>
4506 <p><b>Syntax</b>
4507 <p><!--para 1 -->
4508 <pre>
4509 additive-expression:
4510 multiplicative-expression
4511 additive-expression + multiplicative-expression
4512 additive-expression - multiplicative-expression
4513 </pre>
4514 <p><b>Constraints</b>
4515 <p><!--para 2 -->
4516 For addition, either both operands shall have arithmetic type, or one operand shall be a
4517 pointer to an object type and the other shall have integer type. (Incrementing is
4518 equivalent to adding 1.)
4519 <p><!--para 3 -->
4520 For subtraction, one of the following shall hold:
4521 <ul>
4522 <li> both operands have arithmetic type;
4526 <!--page 95 -->
4527 <li> both operands are pointers to qualified or unqualified versions of compatible object
4528 types; or
4529 <li> the left operand is a pointer to an object type and the right operand has integer type.
4530 </ul>
4531 (Decrementing is equivalent to subtracting 1.)
4532 <p><b>Semantics</b>
4533 <p><!--para 4 -->
4534 If both operands have arithmetic type, the usual arithmetic conversions are performed on
4535 them.
4536 <p><!--para 5 -->
4537 The result of the binary + operator is the sum of the operands.
4538 <p><!--para 6 -->
4539 The result of the binary - operator is the difference resulting from the subtraction of the
4540 second operand from the first.
4541 <p><!--para 7 -->
4542 For the purposes of these operators, a pointer to an object that is not an element of an
4543 array behaves the same as a pointer to the first element of an array of length one with the
4544 type of the object as its element type.
4545 <p><!--para 8 -->
4546 When an expression that has integer type is added to or subtracted from a pointer, the
4547 result has the type of the pointer operand. If the pointer operand points to an element of
4548 an array object, and the array is large enough, the result points to an element offset from
4549 the original element such that the difference of the subscripts of the resulting and original
4550 array elements equals the integer expression. In other words, if the expression P points to
4551 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
4552 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
4553 the array object, provided they exist. Moreover, if the expression P points to the last
4554 element of an array object, the expression (P)+1 points one past the last element of the
4555 array object, and if the expression Q points one past the last element of an array object,
4556 the expression (Q)-1 points to the last element of the array object. If both the pointer
4557 operand and the result point to elements of the same array object, or one past the last
4558 element of the array object, the evaluation shall not produce an overflow; otherwise, the
4559 behavior is undefined. If the result points one past the last element of the array object, it
4560 shall not be used as the operand of a unary * operator that is evaluated.
4561 <p><!--para 9 -->
4562 When two pointers are subtracted, both shall point to elements of the same array object,
4563 or one past the last element of the array object; the result is the difference of the
4564 subscripts of the two array elements. The size of the result is implementation-defined,
4565 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.17"><stddef.h></a> header.
4566 If the result is not representable in an object of that type, the behavior is undefined. In
4567 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
4568 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
4569 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
4570 an array object or one past the last element of an array object, and the expression Q points
4571 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
4572 <!--page 96 -->
4573 value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
4574 expression P points one past the last element of the array object, even though the
4575 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note91"><b>91)</b></a></sup>
4576 <p><!--para 10 -->
4577 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
4578 <pre>
4579 {
4580 int n = 4, m = 3;
4581 int a[n][m];
4582 int (*p)[m] = a; // p == &a[0]
4583 p += 1; // p == &a[1]
4584 (*p)[2] = 99; // a[1][2] == 99
4585 n = p - a; // n == 1
4586 }
4587 </pre>
4588 <p><!--para 11 -->
4589 If array a in the above example were declared to be an array of known constant size, and pointer p were
4590 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
4591 the same.
4593 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), common definitions <a href="#7.17"><stddef.h></a>
4596 <p><b>Footnotes</b>
4597 <p><small><a name="note91" href="#note91">91)</a> Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In
4598 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
4599 by the size of the object originally pointed to, and the resulting pointer is converted back to the
4600 original type. For pointer subtraction, the result of the difference between the character pointers is
4601 similarly divided by the size of the object originally pointed to.
4602 When viewed in this way, an implementation need only provide one extra byte (which may overlap
4603 another object in the program) just after the end of the object in order to satisfy the ''one past the last
4604 element'' requirements.
4605 </small>
4608 <p><b>Syntax</b>
4609 <p><!--para 1 -->
4610 <pre>
4611 shift-expression:
4612 additive-expression
4613 shift-expression << additive-expression
4614 shift-expression >> additive-expression
4615 </pre>
4616 <p><b>Constraints</b>
4617 <p><!--para 2 -->
4618 Each of the operands shall have integer type.
4619 <p><b>Semantics</b>
4620 <p><!--para 3 -->
4621 The integer promotions are performed on each of the operands. The type of the result is
4622 that of the promoted left operand. If the value of the right operand is negative or is
4623 greater than or equal to the width of the promoted left operand, the behavior is undefined.
4628 <!--page 97 -->
4629 <p><!--para 4 -->
4630 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
4631 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
4632 one more than the maximum value representable in the result type. If E1 has a signed
4633 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
4634 the resulting value; otherwise, the behavior is undefined.
4635 <p><!--para 5 -->
4636 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
4637 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
4638 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
4639 resulting value is implementation-defined.
4642 <p><b>Syntax</b>
4643 <p><!--para 1 -->
4644 <pre>
4645 relational-expression:
4646 shift-expression
4647 relational-expression < shift-expression
4648 relational-expression > shift-expression
4649 relational-expression <= shift-expression
4650 relational-expression >= shift-expression
4651 </pre>
4652 <p><b>Constraints</b>
4653 <p><!--para 2 -->
4654 One of the following shall hold:
4655 <ul>
4656 <li> both operands have real type;
4657 <li> both operands are pointers to qualified or unqualified versions of compatible object
4658 types; or
4659 <li> both operands are pointers to qualified or unqualified versions of compatible
4660 incomplete types.
4661 </ul>
4662 <p><b>Semantics</b>
4663 <p><!--para 3 -->
4664 If both of the operands have arithmetic type, the usual arithmetic conversions are
4665 performed.
4666 <p><!--para 4 -->
4667 For the purposes of these operators, a pointer to an object that is not an element of an
4668 array behaves the same as a pointer to the first element of an array of length one with the
4669 type of the object as its element type.
4670 <p><!--para 5 -->
4671 When two pointers are compared, the result depends on the relative locations in the
4672 address space of the objects pointed to. If two pointers to object or incomplete types both
4673 point to the same object, or both point one past the last element of the same array object,
4674 they compare equal. If the objects pointed to are members of the same aggregate object,
4675 pointers to structure members declared later compare greater than pointers to members
4676 declared earlier in the structure, and pointers to array elements with larger subscript
4677 <!--page 98 -->
4678 values compare greater than pointers to elements of the same array with lower subscript
4679 values. All pointers to members of the same union object compare equal. If the
4680 expression P points to an element of an array object and the expression Q points to the
4681 last element of the same array object, the pointer expression Q+1 compares greater than
4682 P. In all other cases, the behavior is undefined.
4683 <p><!--para 6 -->
4684 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
4685 (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is false.<sup><a href="#note92"><b>92)</b></a></sup>
4686 The result has type int.
4688 <p><b>Footnotes</b>
4689 <p><small><a name="note92" href="#note92">92)</a> The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it
4690 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
4691 </small>
4694 <p><b>Syntax</b>
4695 <p><!--para 1 -->
4696 <pre>
4697 equality-expression:
4698 relational-expression
4699 equality-expression == relational-expression
4700 equality-expression != relational-expression
4701 </pre>
4702 <p><b>Constraints</b>
4703 <p><!--para 2 -->
4704 One of the following shall hold:
4705 <ul>
4706 <li> both operands have arithmetic type;
4707 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4708 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4709 qualified or unqualified version of void; or
4710 <li> one operand is a pointer and the other is a null pointer constant.
4711 </ul>
4712 <p><b>Semantics</b>
4713 <p><!--para 3 -->
4714 The == (equal to) and != (not equal to) operators are analogous to the relational
4715 operators except for their lower precedence.<sup><a href="#note93"><b>93)</b></a></sup> Each of the operators yields 1 if the
4716 specified relation is true and 0 if it is false. The result has type int. For any pair of
4717 operands, exactly one of the relations is true.
4718 <p><!--para 4 -->
4719 If both of the operands have arithmetic type, the usual arithmetic conversions are
4720 performed. Values of complex types are equal if and only if both their real parts are equal
4721 and also their imaginary parts are equal. Any two values of arithmetic types from
4722 different type domains are equal if and only if the results of their conversions to the
4723 (complex) result type determined by the usual arithmetic conversions are equal.
4726 <!--page 99 -->
4727 <p><!--para 5 -->
4728 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
4729 null pointer constant, the null pointer constant is converted to the type of the pointer. If
4730 one operand is a pointer to an object or incomplete type and the other is a pointer to a
4731 qualified or unqualified version of void, the former is converted to the type of the latter.
4732 <p><!--para 6 -->
4733 Two pointers compare equal if and only if both are null pointers, both are pointers to the
4734 same object (including a pointer to an object and a subobject at its beginning) or function,
4735 both are pointers to one past the last element of the same array object, or one is a pointer
4736 to one past the end of one array object and the other is a pointer to the start of a different
4737 array object that happens to immediately follow the first array object in the address
4739 <p><!--para 7 -->
4740 For the purposes of these operators, a pointer to an object that is not an element of an
4741 array behaves the same as a pointer to the first element of an array of length one with the
4742 type of the object as its element type.
4744 <p><b>Footnotes</b>
4745 <p><small><a name="note93" href="#note93">93)</a> Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
4746 </small>
4747 <p><small><a name="note94" href="#note94">94)</a> Two objects may be adjacent in memory because they are adjacent elements of a larger array or
4748 adjacent members of a structure with no padding between them, or because the implementation chose
4749 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
4750 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
4751 behavior.
4752 </small>
4755 <p><b>Syntax</b>
4756 <p><!--para 1 -->
4757 <pre>
4758 AND-expression:
4759 equality-expression
4760 AND-expression & equality-expression
4761 </pre>
4762 <p><b>Constraints</b>
4763 <p><!--para 2 -->
4764 Each of the operands shall have integer type.
4765 <p><b>Semantics</b>
4766 <p><!--para 3 -->
4767 The usual arithmetic conversions are performed on the operands.
4768 <p><!--para 4 -->
4769 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
4770 the result is set if and only if each of the corresponding bits in the converted operands is
4771 set).
4776 <!--page 100 -->
4779 <p><b>Syntax</b>
4780 <p><!--para 1 -->
4781 <pre>
4782 exclusive-OR-expression:
4783 AND-expression
4784 exclusive-OR-expression ^ AND-expression
4785 </pre>
4786 <p><b>Constraints</b>
4787 <p><!--para 2 -->
4788 Each of the operands shall have integer type.
4789 <p><b>Semantics</b>
4790 <p><!--para 3 -->
4791 The usual arithmetic conversions are performed on the operands.
4792 <p><!--para 4 -->
4793 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
4794 in the result is set if and only if exactly one of the corresponding bits in the converted
4795 operands is set).
4798 <p><b>Syntax</b>
4799 <p><!--para 1 -->
4800 <pre>
4801 inclusive-OR-expression:
4802 exclusive-OR-expression
4803 inclusive-OR-expression | exclusive-OR-expression
4804 </pre>
4805 <p><b>Constraints</b>
4806 <p><!--para 2 -->
4807 Each of the operands shall have integer type.
4808 <p><b>Semantics</b>
4809 <p><!--para 3 -->
4810 The usual arithmetic conversions are performed on the operands.
4811 <p><!--para 4 -->
4812 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
4813 the result is set if and only if at least one of the corresponding bits in the converted
4814 operands is set).
4815 <!--page 101 -->
4818 <p><b>Syntax</b>
4819 <p><!--para 1 -->
4820 <pre>
4821 logical-AND-expression:
4822 inclusive-OR-expression
4823 logical-AND-expression && inclusive-OR-expression
4824 </pre>
4825 <p><b>Constraints</b>
4826 <p><!--para 2 -->
4827 Each of the operands shall have scalar type.
4828 <p><b>Semantics</b>
4829 <p><!--para 3 -->
4830 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
4831 yields 0. The result has type int.
4832 <p><!--para 4 -->
4833 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
4834 there is a sequence point after the evaluation of the first operand. If the first operand
4835 compares equal to 0, the second operand is not evaluated.
4838 <p><b>Syntax</b>
4839 <p><!--para 1 -->
4840 <pre>
4841 logical-OR-expression:
4842 logical-AND-expression
4843 logical-OR-expression || logical-AND-expression
4844 </pre>
4845 <p><b>Constraints</b>
4846 <p><!--para 2 -->
4847 Each of the operands shall have scalar type.
4848 <p><b>Semantics</b>
4849 <p><!--para 3 -->
4850 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
4851 yields 0. The result has type int.
4852 <p><!--para 4 -->
4853 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; there is
4854 a sequence point after the evaluation of the first operand. If the first operand compares
4855 unequal to 0, the second operand is not evaluated.
4856 <!--page 102 -->
4859 <p><b>Syntax</b>
4860 <p><!--para 1 -->
4861 <pre>
4862 conditional-expression:
4863 logical-OR-expression
4864 logical-OR-expression ? expression : conditional-expression
4865 </pre>
4866 <p><b>Constraints</b>
4867 <p><!--para 2 -->
4868 The first operand shall have scalar type.
4869 <p><!--para 3 -->
4870 One of the following shall hold for the second and third operands:
4871 <ul>
4872 <li> both operands have arithmetic type;
4873 <li> both operands have the same structure or union type;
4874 <li> both operands have void type;
4875 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4876 <li> one operand is a pointer and the other is a null pointer constant; or
4877 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4878 qualified or unqualified version of void.
4879 </ul>
4880 <p><b>Semantics</b>
4881 <p><!--para 4 -->
4882 The first operand is evaluated; there is a sequence point after its evaluation. The second
4883 operand is evaluated only if the first compares unequal to 0; the third operand is evaluated
4884 only if the first compares equal to 0; the result is the value of the second or third operand
4885 (whichever is evaluated), converted to the type described below.<sup><a href="#note95"><b>95)</b></a></sup> If an attempt is made
4886 to modify the result of a conditional operator or to access it after the next sequence point,
4887 the behavior is undefined.
4888 <p><!--para 5 -->
4889 If both the second and third operands have arithmetic type, the result type that would be
4890 determined by the usual arithmetic conversions, were they applied to those two operands,
4891 is the type of the result. If both the operands have structure or union type, the result has
4892 that type. If both operands have void type, the result has void type.
4893 <p><!--para 6 -->
4894 If both the second and third operands are pointers or one is a null pointer constant and the
4895 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
4896 of the types pointed-to by both operands. Furthermore, if both operands are pointers to
4897 compatible types or to differently qualified versions of compatible types, the result type is
4898 a pointer to an appropriately qualified version of the composite type; if one operand is a
4899 null pointer constant, the result has the type of the other operand; otherwise, one operand
4900 is a pointer to void or a qualified version of void, in which case the result type is a
4902 <!--page 103 -->
4903 pointer to an appropriately qualified version of void.
4904 <p><!--para 7 -->
4905 EXAMPLE The common type that results when the second and third operands are pointers is determined
4906 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
4907 pointers have compatible types.
4908 <p><!--para 8 -->
4909 Given the declarations
4910 <pre>
4911 const void *c_vp;
4912 void *vp;
4913 const int *c_ip;
4914 volatile int *v_ip;
4915 int *ip;
4916 const char *c_cp;
4917 </pre>
4918 the third column in the following table is the common type that is the result of a conditional expression in
4919 which the first two columns are the second and third operands (in either order):
4920 <pre>
4921 c_vp c_ip const void *
4922 v_ip 0 volatile int *
4923 c_ip v_ip const volatile int *
4924 vp c_cp const void *
4925 ip c_ip const int *
4926 vp ip void *
4927 </pre>
4930 <p><b>Footnotes</b>
4931 <p><small><a name="note95" href="#note95">95)</a> A conditional expression does not yield an lvalue.
4932 </small>
4935 <p><b>Syntax</b>
4936 <p><!--para 1 -->
4937 <pre>
4938 assignment-expression:
4939 conditional-expression
4940 unary-expression assignment-operator assignment-expression
4941 assignment-operator: one of
4942 = *= /= %= += -= <<= >>= &= ^= |=
4943 </pre>
4944 <p><b>Constraints</b>
4945 <p><!--para 2 -->
4946 An assignment operator shall have a modifiable lvalue as its left operand.
4947 <p><b>Semantics</b>
4948 <p><!--para 3 -->
4949 An assignment operator stores a value in the object designated by the left operand. An
4950 assignment expression has the value of the left operand after the assignment, but is not an
4951 lvalue. The type of an assignment expression is the type of the left operand unless the
4952 left operand has qualified type, in which case it is the unqualified version of the type of
4953 the left operand. The side effect of updating the stored value of the left operand shall
4954 occur between the previous and the next sequence point.
4955 <p><!--para 4 -->
4956 The order of evaluation of the operands is unspecified. If an attempt is made to modify
4957 the result of an assignment operator or to access it after the next sequence point, the
4958 behavior is undefined.
4959 <!--page 104 -->
4962 <p><b>Constraints</b>
4963 <p><!--para 1 -->
4965 <ul>
4966 <li> the left operand has qualified or unqualified arithmetic type and the right has
4967 arithmetic type;
4968 <li> the left operand has a qualified or unqualified version of a structure or union type
4969 compatible with the type of the right;
4970 <li> both operands are pointers to qualified or unqualified versions of compatible types,
4971 and the type pointed to by the left has all the qualifiers of the type pointed to by the
4972 right;
4973 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4974 qualified or unqualified version of void, and the type pointed to by the left has all
4975 the qualifiers of the type pointed to by the right;
4976 <li> the left operand is a pointer and the right is a null pointer constant; or
4977 <li> the left operand has type _Bool and the right is a pointer.
4978 </ul>
4979 <p><b>Semantics</b>
4980 <p><!--para 2 -->
4981 In simple assignment (=), the value of the right operand is converted to the type of the
4982 assignment expression and replaces the value stored in the object designated by the left
4983 operand.
4984 <p><!--para 3 -->
4985 If the value being stored in an object is read from another object that overlaps in any way
4986 the storage of the first object, then the overlap shall be exact and the two objects shall
4987 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
4988 undefined.
4989 <p><!--para 4 -->
4990 EXAMPLE 1 In the program fragment
4991 <pre>
4992 int f(void);
4993 char c;
4994 /* ... */
4995 if ((c = f()) == -1)
4996 /* ... */
4997 </pre>
4998 the int value returned by the function may be truncated when stored in the char, and then converted back
4999 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
5000 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
5004 <!--page 105 -->
5005 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
5006 variable c should be declared as int.
5008 <p><!--para 5 -->
5009 EXAMPLE 2 In the fragment:
5010 <pre>
5011 char c;
5012 int i;
5013 long l;
5014 l = (c = i);
5015 </pre>
5016 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
5017 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
5018 that is, long int type.
5020 <p><!--para 6 -->
5021 EXAMPLE 3 Consider the fragment:
5022 <pre>
5023 const char **cpp;
5024 char *p;
5025 const char c = 'A';
5026 cpp = &p; // constraint violation
5027 *cpp = &c; // valid
5028 *p = 0; // valid
5029 </pre>
5030 The first assignment is unsafe because it would allow the following valid code to attempt to change the
5031 value of the const object c.
5034 <p><b>Footnotes</b>
5035 <p><small><a name="note96" href="#note96">96)</a> The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
5036 (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
5037 qualifiers that were applied to the type category of the expression (for example, it removes const but
5038 not volatile from the type int volatile * const).
5039 </small>
5042 <p><b>Constraints</b>
5043 <p><!--para 1 -->
5044 For the operators += and -= only, either the left operand shall be a pointer to an object
5045 type and the right shall have integer type, or the left operand shall have qualified or
5046 unqualified arithmetic type and the right shall have arithmetic type.
5047 <p><!--para 2 -->
5048 For the other operators, each operand shall have arithmetic type consistent with those
5049 allowed by the corresponding binary operator.
5050 <p><b>Semantics</b>
5051 <p><!--para 3 -->
5052 A compound assignment of the form E1 op = E2 differs from the simple assignment
5053 expression E1 = E1 op (E2) only in that the lvalue E1 is evaluated only once.
5054 <!--page 106 -->
5057 <p><b>Syntax</b>
5058 <p><!--para 1 -->
5059 <pre>
5060 expression:
5061 assignment-expression
5062 expression , assignment-expression
5063 </pre>
5064 <p><b>Semantics</b>
5065 <p><!--para 2 -->
5066 The left operand of a comma operator is evaluated as a void expression; there is a
5067 sequence point after its evaluation. Then the right operand is evaluated; the result has its
5068 type and value.<sup><a href="#note97"><b>97)</b></a></sup> If an attempt is made to modify the result of a comma operator or to
5069 access it after the next sequence point, the behavior is undefined.
5070 <p><!--para 3 -->
5071 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
5072 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
5073 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
5074 expression of a conditional operator in such contexts. In the function call
5075 <pre>
5076 f(a, (t=3, t+2), c)
5077 </pre>
5078 the function has three arguments, the second of which has the value 5.
5085 <!--page 107 -->
5087 <p><b>Footnotes</b>
5089 </small>
5092 <p><b>Syntax</b>
5093 <p><!--para 1 -->
5094 <pre>
5095 constant-expression:
5096 conditional-expression
5097 </pre>
5098 <p><b>Description</b>
5099 <p><!--para 2 -->
5100 A constant expression can be evaluated during translation rather than runtime, and
5101 accordingly may be used in any place that a constant may be.
5102 <p><b>Constraints</b>
5103 <p><!--para 3 -->
5104 Constant expressions shall not contain assignment, increment, decrement, function-call,
5105 or comma operators, except when they are contained within a subexpression that is not
5107 <p><!--para 4 -->
5108 Each constant expression shall evaluate to a constant that is in the range of representable
5109 values for its type.
5110 <p><b>Semantics</b>
5111 <p><!--para 5 -->
5112 An expression that evaluates to a constant is required in several contexts. If a floating
5113 expression is evaluated in the translation environment, the arithmetic precision and range
5114 shall be at least as great as if the expression were being evaluated in the execution
5115 environment.
5116 <p><!--para 6 -->
5117 An integer constant expression<sup><a href="#note99"><b>99)</b></a></sup> shall have integer type and shall only have operands
5118 that are integer constants, enumeration constants, character constants, sizeof
5119 expressions whose results are integer constants, and floating constants that are the
5120 immediate operands of casts. Cast operators in an integer constant expression shall only
5121 convert arithmetic types to integer types, except as part of an operand to the sizeof
5122 operator.
5123 <p><!--para 7 -->
5124 More latitude is permitted for constant expressions in initializers. Such a constant
5125 expression shall be, or evaluate to, one of the following:
5126 <ul>
5127 <li> an arithmetic constant expression,
5128 <li> a null pointer constant,
5133 <!--page 108 -->
5134 <li> an address constant, or
5135 <li> an address constant for an object type plus or minus an integer constant expression.
5136 </ul>
5137 <p><!--para 8 -->
5138 An arithmetic constant expression shall have arithmetic type and shall only have
5139 operands that are integer constants, floating constants, enumeration constants, character
5140 constants, and sizeof expressions. Cast operators in an arithmetic constant expression
5141 shall only convert arithmetic types to arithmetic types, except as part of an operand to a
5142 sizeof operator whose result is an integer constant.
5143 <p><!--para 9 -->
5144 An address constant is a null pointer, a pointer to an lvalue designating an object of static
5145 storage duration, or a pointer to a function designator; it shall be created explicitly using
5146 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
5147 an expression of array or function type. The array-subscript [] and member-access .
5148 and -> operators, the address & and indirection * unary operators, and pointer casts may
5149 be used in the creation of an address constant, but the value of an object shall not be
5150 accessed by use of these operators.
5151 <p><!--para 10 -->
5152 An implementation may accept other forms of constant expressions.
5153 <p><!--para 11 -->
5154 The semantic rules for the evaluation of a constant expression are the same as for
5156 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), initialization (<a href="#6.7.8">6.7.8</a>).
5161 <!--page 109 -->
5163 <p><b>Footnotes</b>
5164 <p><small><a name="note98" href="#note98">98)</a> The operand of a sizeof operator is usually not evaluated (<a href="#6.5.3.4">6.5.3.4</a>).
5165 </small>
5166 <p><small><a name="note99" href="#note99">99)</a> An integer constant expression is used to specify the size of a bit-field member of a structure, the
5167 value of an enumeration constant, the size of an array, or the value of a case constant. Further
5168 constraints that apply to the integer constant expressions used in conditional-inclusion preprocessing
5170 </small>
5173 <pre>
5174 static int i = 2 || 1 / 0;
5175 </pre>
5176 the expression is a valid integer constant expression with value one.
5177 </small>
5180 <p><b>Syntax</b>
5181 <p><!--para 1 -->
5182 <pre>
5183 declaration:
5184 declaration-specifiers init-declarator-list<sub>opt</sub> ;
5185 declaration-specifiers:
5186 storage-class-specifier declaration-specifiers<sub>opt</sub>
5187 type-specifier declaration-specifiers<sub>opt</sub>
5188 type-qualifier declaration-specifiers<sub>opt</sub>
5189 function-specifier declaration-specifiers<sub>opt</sub>
5190 init-declarator-list:
5191 init-declarator
5192 init-declarator-list , init-declarator
5193 init-declarator:
5194 declarator
5195 declarator = initializer
5196 </pre>
5197 <p><b>Constraints</b>
5198 <p><!--para 2 -->
5199 A declaration shall declare at least a declarator (other than the parameters of a function or
5200 the members of a structure or union), a tag, or the members of an enumeration.
5201 <p><!--para 3 -->
5202 If an identifier has no linkage, there shall be no more than one declaration of the identifier
5203 (in a declarator or type specifier) with the same scope and in the same name space, except
5205 <p><!--para 4 -->
5206 All declarations in the same scope that refer to the same object or function shall specify
5207 compatible types.
5208 <p><b>Semantics</b>
5209 <p><!--para 5 -->
5210 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
5211 of an identifier is a declaration for that identifier that:
5212 <ul>
5213 <li> for an object, causes storage to be reserved for that object;
5215 <li> for an enumeration constant or typedef name, is the (only) declaration of the
5216 identifier.
5217 </ul>
5218 <p><!--para 6 -->
5219 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
5220 storage duration, and part of the type of the entities that the declarators denote. The init-
5221 declarator-list is a comma-separated sequence of declarators, each of which may have
5223 <!--page 110 -->
5224 additional type information, or an initializer, or both. The declarators contain the
5225 identifiers (if any) being declared.
5226 <p><!--para 7 -->
5227 If an identifier for an object is declared with no linkage, the type for the object shall be
5228 complete by the end of its declarator, or by the end of its init-declarator if it has an
5229 initializer; in the case of function parameters (including in prototypes), it is the adjusted
5231 <p><b> Forward references</b>: declarators (<a href="#6.7.5">6.7.5</a>), enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), initialization
5234 <p><b>Footnotes</b>
5235 <p><small><a name="note101" href="#note101">101)</a> Function definitions have a different syntax, described in <a href="#6.9.1">6.9.1</a>.
5236 </small>
5239 <p><b>Syntax</b>
5240 <p><!--para 1 -->
5241 <pre>
5242 storage-class-specifier:
5243 typedef
5244 extern
5245 static
5246 auto
5247 register
5248 </pre>
5249 <p><b>Constraints</b>
5250 <p><!--para 2 -->
5251 At most, one storage-class specifier may be given in the declaration specifiers in a
5253 <p><b>Semantics</b>
5254 <p><!--para 3 -->
5255 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
5256 only; it is discussed in <a href="#6.7.7">6.7.7</a>. The meanings of the various linkages and storage durations
5258 <p><!--para 4 -->
5259 A declaration of an identifier for an object with storage-class specifier register
5260 suggests that access to the object be as fast as possible. The extent to which such
5261 suggestions are effective is implementation-defined.<sup><a href="#note103"><b>103)</b></a></sup>
5262 <p><!--para 5 -->
5263 The declaration of an identifier for a function that has block scope shall have no explicit
5264 storage-class specifier other than extern.
5268 <!--page 111 -->
5269 <p><!--para 6 -->
5270 If an aggregate or union object is declared with a storage-class specifier other than
5271 typedef, the properties resulting from the storage-class specifier, except with respect to
5272 linkage, also apply to the members of the object, and so on recursively for any aggregate
5273 or union member objects.
5276 <p><b>Footnotes</b>
5277 <p><small><a name="note102" href="#note102">102)</a> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
5278 </small>
5279 <p><small><a name="note103" href="#note103">103)</a> The implementation may treat any register declaration simply as an auto declaration. However,
5280 whether or not addressable storage is actually used, the address of any part of an object declared with
5281 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
5282 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
5283 <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
5284 register is sizeof.
5285 </small>
5288 <p><b>Syntax</b>
5289 <p><!--para 1 -->
5290 <pre>
5291 type-specifier:
5292 void
5293 char
5294 short
5295 int
5296 long
5297 float
5298 double
5299 signed
5300 unsigned
5301 _Bool
5302 _Complex
5303 struct-or-union-specifier *
5304 enum-specifier
5305 typedef-name
5306 </pre>
5307 <p><b>Constraints</b>
5308 <p><!--para 2 -->
5309 At least one type specifier shall be given in the declaration specifiers in each declaration,
5310 and in the specifier-qualifier list in each struct declaration and type name. Each list of
5311 type specifiers shall be one of the following sets (delimited by commas, when there is
5312 more than one set on a line); the type specifiers may occur in any order, possibly
5313 intermixed with the other declaration specifiers.
5314 <ul>
5315 <li> void
5316 <li> char
5317 <li> signed char
5318 <li> unsigned char
5319 <li> short, signed short, short int, or signed short int
5320 <li> unsigned short, or unsigned short int
5321 <li> int, signed, or signed int
5322 <!--page 112 -->
5323 <li> unsigned, or unsigned int
5324 <li> long, signed long, long int, or signed long int
5325 <li> unsigned long, or unsigned long int
5326 <li> long long, signed long long, long long int, or
5327 signed long long int
5328 <li> unsigned long long, or unsigned long long int
5329 <li> float
5330 <li> double
5331 <li> long double
5332 <li> _Bool
5333 <li> float _Complex
5334 <li> double _Complex
5335 <li> long double _Complex
5336 <li> struct or union specifier *
5337 <li> enum specifier
5338 <li> typedef name
5339 </ul>
5340 <p><!--para 3 -->
5341 The type specifier _Complex shall not be used if the implementation does not provide
5343 <p><b>Semantics</b>
5344 <p><!--para 4 -->
5345 Specifiers for structures, unions, and enumerations are discussed in <a href="#6.7.2.1">6.7.2.1</a> through
5346 <a href="#6.7.2.3">6.7.2.3</a>. Declarations of typedef names are discussed in <a href="#6.7.7">6.7.7</a>. The characteristics of the
5348 <p><!--para 5 -->
5349 Each of the comma-separated sets designates the same type, except that for bit-fields, it is
5350 implementation-defined whether the specifier int designates the same type as signed
5351 int or the same type as unsigned int.
5352 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
5353 (<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="#6.7.7">6.7.7</a>).
5358 <!--page 113 -->
5360 <p><b>Footnotes</b>
5361 <p><small><a name="note104" href="#note104">104)</a> Freestanding implementations are not required to provide complex types. *
5362 </small>
5365 <p><b>Syntax</b>
5366 <p><!--para 1 -->
5367 <pre>
5368 struct-or-union-specifier:
5369 struct-or-union identifier<sub>opt</sub> { struct-declaration-list }
5370 struct-or-union identifier
5371 struct-or-union:
5372 struct
5373 union
5374 struct-declaration-list:
5375 struct-declaration
5376 struct-declaration-list struct-declaration
5377 struct-declaration:
5378 specifier-qualifier-list struct-declarator-list ;
5379 specifier-qualifier-list:
5380 type-specifier specifier-qualifier-list<sub>opt</sub>
5381 type-qualifier specifier-qualifier-list<sub>opt</sub>
5382 struct-declarator-list:
5383 struct-declarator
5384 struct-declarator-list , struct-declarator
5385 struct-declarator:
5386 declarator
5387 declarator<sub>opt</sub> : constant-expression
5388 </pre>
5389 <p><b>Constraints</b>
5390 <p><!--para 2 -->
5391 A structure or union shall not contain a member with incomplete or function type (hence,
5392 a structure shall not contain an instance of itself, but may contain a pointer to an instance
5393 of itself), except that the last member of a structure with more than one named member
5394 may have incomplete array type; such a structure (and any union containing, possibly
5395 recursively, a member that is such a structure) shall not be a member of a structure or an
5396 element of an array.
5397 <p><!--para 3 -->
5398 The expression that specifies the width of a bit-field shall be an integer constant
5399 expression with a nonnegative value that does not exceed the width of an object of the
5400 type that would be specified were the colon and expression omitted. If the value is zero,
5401 the declaration shall have no declarator.
5402 <p><!--para 4 -->
5403 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
5404 int, unsigned int, or some other implementation-defined type.
5405 <!--page 114 -->
5406 <p><b>Semantics</b>
5407 <p><!--para 5 -->
5408 As discussed in <a href="#6.2.5">6.2.5</a>, a structure is a type consisting of a sequence of members, whose
5409 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
5410 of members whose storage overlap.
5411 <p><!--para 6 -->
5412 Structure and union specifiers have the same form. The keywords struct and union
5413 indicate that the type being specified is, respectively, a structure type or a union type.
5414 <p><!--para 7 -->
5415 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
5416 within a translation unit. The struct-declaration-list is a sequence of declarations for the
5417 members of the structure or union. If the struct-declaration-list contains no named
5418 members, the behavior is undefined. The type is incomplete until after the } that
5419 terminates the list.
5420 <p><!--para 8 -->
5421 A member of a structure or union may have any object type other than a variably
5422 modified type.<sup><a href="#note105"><b>105)</b></a></sup> In addition, a member may be declared to consist of a specified
5423 number of bits (including a sign bit, if any). Such a member is called a bit-field;<sup><a href="#note106"><b>106)</b></a></sup> its
5424 width is preceded by a colon.
5425 <p><!--para 9 -->
5426 A bit-field is interpreted as a signed or unsigned integer type consisting of the specified
5427 number of bits.<sup><a href="#note107"><b>107)</b></a></sup> If the value 0 or 1 is stored into a nonzero-width bit-field of type
5428 _Bool, the value of the bit-field shall compare equal to the value stored.
5429 <p><!--para 10 -->
5430 An implementation may allocate any addressable storage unit large enough to hold a bit-
5431 field. If enough space remains, a bit-field that immediately follows another bit-field in a
5432 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
5433 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
5434 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
5435 low-order or low-order to high-order) is implementation-defined. The alignment of the
5436 addressable storage unit is unspecified.
5437 <p><!--para 11 -->
5438 A bit-field declaration with no declarator, but only a colon and a width, indicates an
5439 unnamed bit-field.<sup><a href="#note108"><b>108)</b></a></sup> As a special case, a bit-field structure member with a width of 0
5440 indicates that no further bit-field is to be packed into the unit in which the previous bit-
5441 field, if any, was placed.
5444 <!--page 115 -->
5445 <p><!--para 12 -->
5446 Each non-bit-field member of a structure or union object is aligned in an implementation-
5447 defined manner appropriate to its type.
5448 <p><!--para 13 -->
5449 Within a structure object, the non-bit-field members and the units in which bit-fields
5450 reside have addresses that increase in the order in which they are declared. A pointer to a
5451 structure object, suitably converted, points to its initial member (or if that member is a
5452 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
5453 padding within a structure object, but not at its beginning.
5454 <p><!--para 14 -->
5455 The size of a union is sufficient to contain the largest of its members. The value of at
5456 most one of the members can be stored in a union object at any time. A pointer to a
5457 union object, suitably converted, points to each of its members (or if a member is a bit-
5458 field, then to the unit in which it resides), and vice versa.
5459 <p><!--para 15 -->
5460 There may be unnamed padding at the end of a structure or union.
5461 <p><!--para 16 -->
5462 As a special case, the last element of a structure with more than one named member may
5463 have an incomplete array type; this is called a flexible array member. In most situations,
5464 the flexible array member is ignored. In particular, the size of the structure is as if the
5465 flexible array member were omitted except that it may have more trailing padding than
5466 the omission would imply. However, when a . (or ->) operator has a left operand that is
5467 (a pointer to) a structure with a flexible array member and the right operand names that
5468 member, it behaves as if that member were replaced with the longest array (with the same
5469 element type) that would not make the structure larger than the object being accessed; the
5470 offset of the array shall remain that of the flexible array member, even if this would differ
5471 from that of the replacement array. If this array would have no elements, it behaves as if
5472 it had one element but the behavior is undefined if any attempt is made to access that
5473 element or to generate a pointer one past it.
5474 <p><!--para 17 -->
5475 EXAMPLE After the declaration:
5476 <pre>
5477 struct s { int n; double d[]; };
5478 </pre>
5479 the structure struct s has a flexible array member d. A typical way to use this is:
5480 <pre>
5481 int m = /* some value */;
5482 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
5483 </pre>
5484 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
5485 p had been declared as:
5486 <pre>
5487 struct { int n; double d[m]; } *p;
5488 </pre>
5489 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
5490 not be the same).
5491 <p><!--para 18 -->
5492 Following the above declaration:
5493 <!--page 116 -->
5494 <pre>
5495 struct s t1 = { 0 }; // valid
5497 t1.n = 4; // valid
5499 </pre>
5500 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
5501 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
5502 <pre>
5503 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)
5504 </pre>
5505 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
5506 code.
5507 <p><!--para 19 -->
5508 After the further declaration:
5509 <pre>
5510 struct ss { int n; };
5511 </pre>
5512 the expressions:
5513 <pre>
5514 sizeof (struct s) >= sizeof (struct ss)
5515 sizeof (struct s) >= offsetof(struct s, d)
5516 </pre>
5517 are always equal to 1.
5518 <p><!--para 20 -->
5519 If sizeof (double) is 8, then after the following code is executed:
5520 <pre>
5521 struct s *s1;
5522 struct s *s2;
5523 s1 = malloc(sizeof (struct s) + 64);
5524 s2 = malloc(sizeof (struct s) + 46);
5525 </pre>
5526 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
5527 purposes, as if the identifiers had been declared as:
5528 <pre>
5529 struct { int n; double d[8]; } *s1;
5530 struct { int n; double d[5]; } *s2;
5531 </pre>
5532 <p><!--para 21 -->
5533 Following the further successful assignments:
5534 <pre>
5535 s1 = malloc(sizeof (struct s) + 10);
5536 s2 = malloc(sizeof (struct s) + 6);
5537 </pre>
5538 they then behave as if the declarations were:
5539 <pre>
5540 struct { int n; double d[1]; } *s1, *s2;
5541 </pre>
5542 and:
5543 <pre>
5544 double *dp;
5545 dp = &(s1->d[0]); // valid
5546 *dp = 42; // valid
5547 dp = &(s2->d[0]); // valid
5548 *dp = 42; // undefined behavior
5549 </pre>
5550 <p><!--para 22 -->
5551 The assignment:
5552 <pre>
5553 *s1 = *s2;
5554 </pre>
5555 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
5556 of the structure, they might be copied or simply overwritten with indeterminate values.
5559 <!--page 117 -->
5561 <p><b>Footnotes</b>
5562 <p><small><a name="note105" href="#note105">105)</a> A structure or union can not contain a member with a variably modified type because member names
5564 </small>
5565 <p><small><a name="note106" href="#note106">106)</a> The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
5566 or arrays of bit-field objects.
5567 </small>
5568 <p><small><a name="note107" href="#note107">107)</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,
5569 then it is implementation-defined whether the bit-field is signed or unsigned.
5570 </small>
5571 <p><small><a name="note108" href="#note108">108)</a> An unnamed bit-field structure member is useful for padding to conform to externally imposed
5572 layouts.
5573 </small>
5576 <p><b>Syntax</b>
5577 <p><!--para 1 -->
5578 <pre>
5579 enum-specifier:
5580 enum identifier<sub>opt</sub> { enumerator-list }
5581 enum identifier<sub>opt</sub> { enumerator-list , }
5582 enum identifier
5583 enumerator-list:
5584 enumerator
5585 enumerator-list , enumerator
5586 enumerator:
5587 enumeration-constant
5588 enumeration-constant = constant-expression
5589 </pre>
5590 <p><b>Constraints</b>
5591 <p><!--para 2 -->
5592 The expression that defines the value of an enumeration constant shall be an integer
5593 constant expression that has a value representable as an int.
5594 <p><b>Semantics</b>
5595 <p><!--para 3 -->
5596 The identifiers in an enumerator list are declared as constants that have type int and
5597 may appear wherever such are permitted.<sup><a href="#note109"><b>109)</b></a></sup> An enumerator with = defines its
5598 enumeration constant as the value of the constant expression. If the first enumerator has
5599 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
5600 defines its enumeration constant as the value of the constant expression obtained by
5601 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
5602 = may produce enumeration constants with values that duplicate other values in the same
5603 enumeration.) The enumerators of an enumeration are also known as its members.
5604 <p><!--para 4 -->
5605 Each enumerated type shall be compatible with char, a signed integer type, or an
5606 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note110"><b>110)</b></a></sup> but shall be
5607 capable of representing the values of all the members of the enumeration. The
5608 enumerated type is incomplete until after the } that terminates the list of enumerator
5609 declarations.
5614 <!--page 118 -->
5615 <p><!--para 5 -->
5616 EXAMPLE The following fragment:
5617 <pre>
5618 enum hue { chartreuse, burgundy, claret=20, winedark };
5619 enum hue col, *cp;
5620 col = claret;
5621 cp = &col;
5622 if (*cp != burgundy)
5623 /* ... */
5624 </pre>
5625 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
5626 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
5630 <p><b>Footnotes</b>
5631 <p><small><a name="note109" href="#note109">109)</a> Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
5632 each other and from other identifiers declared in ordinary declarators.
5633 </small>
5634 <p><small><a name="note110" href="#note110">110)</a> An implementation may delay the choice of which integer type until all enumeration constants have
5635 been seen.
5636 </small>
5639 <p><b>Constraints</b>
5640 <p><!--para 1 -->
5641 A specific type shall have its content defined at most once.
5642 <p><!--para 2 -->
5643 Where two declarations that use the same tag declare the same type, they shall both use
5644 the same choice of struct, union, or enum.
5645 <p><!--para 3 -->
5646 A type specifier of the form
5647 <pre>
5648 enum identifier
5649 </pre>
5650 without an enumerator list shall only appear after the type it specifies is complete.
5651 <p><b>Semantics</b>
5652 <p><!--para 4 -->
5653 All declarations of structure, union, or enumerated types that have the same scope and
5654 use the same tag declare the same type. The type is incomplete<sup><a href="#note111"><b>111)</b></a></sup> until the closing brace
5655 of the list defining the content, and complete thereafter.
5656 <p><!--para 5 -->
5657 Two declarations of structure, union, or enumerated types which are in different scopes or
5658 use different tags declare distinct types. Each declaration of a structure, union, or
5659 enumerated type which does not include a tag declares a distinct type.
5660 <p><!--para 6 -->
5661 A type specifier of the form
5662 <pre>
5663 struct-or-union identifier<sub>opt</sub> { struct-declaration-list }
5664 </pre>
5665 or
5666 <pre>
5667 enum identifier { enumerator-list }
5668 </pre>
5669 or
5670 <pre>
5671 enum identifier { enumerator-list , }
5672 </pre>
5673 declares a structure, union, or enumerated type. The list defines the structure content,
5675 <!--page 119 -->
5676 union content, or enumeration content. If an identifier is provided,<sup><a href="#note112"><b>112)</b></a></sup> the type specifier
5677 also declares the identifier to be the tag of that type.
5678 <p><!--para 7 -->
5679 A declaration of the form
5680 <pre>
5681 struct-or-union identifier ;
5682 </pre>
5683 specifies a structure or union type and declares the identifier as a tag of that type.<sup><a href="#note113"><b>113)</b></a></sup>
5684 <p><!--para 8 -->
5685 If a type specifier of the form
5686 <pre>
5687 struct-or-union identifier
5688 </pre>
5689 occurs other than as part of one of the above forms, and no other declaration of the
5690 identifier as a tag is visible, then it declares an incomplete structure or union type, and
5692 <p><!--para 9 -->
5693 If a type specifier of the form
5694 <pre>
5695 struct-or-union identifier
5696 </pre>
5697 or
5698 <pre>
5699 enum identifier
5700 </pre>
5701 occurs other than as part of one of the above forms, and a declaration of the identifier as a
5702 tag is visible, then it specifies the same type as that other declaration, and does not
5703 redeclare the tag.
5704 <p><!--para 10 -->
5705 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
5706 <pre>
5707 struct tnode {
5708 int count;
5709 struct tnode *left, *right;
5710 };
5711 </pre>
5712 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
5713 declaration has been given, the declaration
5714 <pre>
5715 struct tnode s, *sp;
5716 </pre>
5717 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
5718 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
5719 which sp points; the expression s.right->count designates the count member of the right struct
5720 tnode pointed to from s.
5721 <p><!--para 11 -->
5722 The following alternative formulation uses the typedef mechanism:
5727 <!--page 120 -->
5728 <pre>
5729 typedef struct tnode TNODE;
5730 struct tnode {
5731 int count;
5732 TNODE *left, *right;
5733 };
5734 TNODE s, *sp;
5735 </pre>
5737 <p><!--para 12 -->
5738 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
5739 structures, the declarations
5740 <pre>
5741 struct s1 { struct s2 *s2p; /* ... */ }; // D1
5742 struct s2 { struct s1 *s1p; /* ... */ }; // D2
5743 </pre>
5744 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
5745 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
5746 D2. To eliminate this context sensitivity, the declaration
5747 <pre>
5748 struct s2;
5749 </pre>
5750 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
5751 completes the specification of the new type.
5753 <p><b> Forward references</b>: declarators (<a href="#6.7.5">6.7.5</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>), type definitions
5756 <p><b>Footnotes</b>
5757 <p><small><a name="note111" href="#note111">111)</a> An incomplete type may only by used when the size of an object of that type is not needed. It is not
5758 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
5759 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
5760 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
5761 </small>
5762 <p><small><a name="note112" href="#note112">112)</a> If there is no identifier, the type can, within the translation unit, only be referred to by the declaration
5763 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
5764 can make use of that typedef name to declare objects having the specified structure, union, or
5765 enumerated type.
5766 </small>
5767 <p><small><a name="note113" href="#note113">113)</a> A similar construction with enum does not exist.
5768 </small>
5771 <p><b>Syntax</b>
5772 <p><!--para 1 -->
5773 <pre>
5774 type-qualifier:
5775 const
5776 restrict
5777 volatile
5778 </pre>
5779 <p><b>Constraints</b>
5780 <p><!--para 2 -->
5781 Types other than pointer types derived from object or incomplete types shall not be
5782 restrict-qualified.
5783 <p><b>Semantics</b>
5784 <p><!--para 3 -->
5785 The properties associated with qualified types are meaningful only for expressions that
5787 <p><!--para 4 -->
5788 If the same qualifier appears more than once in the same specifier-qualifier-list, either
5789 directly or via one or more typedefs, the behavior is the same as if it appeared only
5790 once.
5795 <!--page 121 -->
5796 <p><!--para 5 -->
5797 If an attempt is made to modify an object defined with a const-qualified type through use
5798 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
5799 made to refer to an object defined with a volatile-qualified type through use of an lvalue
5800 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note115"><b>115)</b></a></sup>
5801 <p><!--para 6 -->
5802 An object that has volatile-qualified type may be modified in ways unknown to the
5803 implementation or have other unknown side effects. Therefore any expression referring
5804 to such an object shall be evaluated strictly according to the rules of the abstract machine,
5805 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
5806 object shall agree with that prescribed by the abstract machine, except as modified by the
5807 unknown factors mentioned previously.<sup><a href="#note116"><b>116)</b></a></sup> What constitutes an access to an object that
5808 has volatile-qualified type is implementation-defined.
5809 <p><!--para 7 -->
5810 An object that is accessed through a restrict-qualified pointer has a special association
5811 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
5812 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note117"><b>117)</b></a></sup> The intended
5813 use of the restrict qualifier (like the register storage class) is to promote
5814 optimization, and deleting all instances of the qualifier from all preprocessing translation
5815 units composing a conforming program does not change its meaning (i.e., observable
5816 behavior).
5817 <p><!--para 8 -->
5818 If the specification of an array type includes any type qualifiers, the element type is so-
5819 qualified, not the array type. If the specification of a function type includes any type
5821 <p><!--para 9 -->
5822 For two qualified types to be compatible, both shall have the identically qualified version
5823 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
5824 does not affect the specified type.
5825 <p><!--para 10 -->
5826 EXAMPLE 1 An object declared
5827 <pre>
5828 extern const volatile int real_time_clock;
5829 </pre>
5830 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
5835 <!--page 122 -->
5836 <p><!--para 11 -->
5837 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
5838 modify an aggregate type:
5839 <pre>
5840 const struct s { int mem; } cs = { 1 };
5841 struct s ncs; // the object ncs is modifiable
5842 typedef int A[2][3];
5843 const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
5844 int *pi;
5845 const int *pci;
5846 ncs = cs; // valid
5847 cs = ncs; // violates modifiable lvalue constraint for =
5848 pi = &ncs.mem; // valid
5849 pi = &cs.mem; // violates type constraints for =
5850 pci = &cs.mem; // valid
5851 pi = a[0]; // invalid: a[0] has type ''const int *''
5852 </pre>
5855 <p><b>Footnotes</b>
5856 <p><small><a name="note114" href="#note114">114)</a> The implementation may place a const object that is not volatile in a read-only region of
5857 storage. Moreover, the implementation need not allocate storage for such an object if its address is
5858 never used.
5859 </small>
5860 <p><small><a name="note115" href="#note115">115)</a> This applies to those objects that behave as if they were defined with qualified types, even if they are
5861 never actually defined as objects in the program (such as an object at a memory-mapped input/output
5862 address).
5863 </small>
5864 <p><small><a name="note116" href="#note116">116)</a> A volatile declaration may be used to describe an object corresponding to a memory-mapped
5865 input/output port or an object accessed by an asynchronously interrupting function. Actions on
5866 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
5867 permitted by the rules for evaluating expressions.
5868 </small>
5869 <p><small><a name="note117" href="#note117">117)</a> For example, a statement that assigns a value returned by malloc to a single pointer establishes this
5870 association between the allocated object and the pointer.
5871 </small>
5872 <p><small><a name="note118" href="#note118">118)</a> Both of these can occur through the use of typedefs.
5873 </small>
5876 <p><!--para 1 -->
5877 Let D be a declaration of an ordinary identifier that provides a means of designating an
5878 object P as a restrict-qualified pointer to type T.
5879 <p><!--para 2 -->
5880 If D appears inside a block and does not have storage class extern, let B denote the
5881 block. If D appears in the list of parameter declarations of a function definition, let B
5882 denote the associated block. Otherwise, let B denote the block of main (or the block of
5883 whatever function is called at program startup in a freestanding environment).
5884 <p><!--para 3 -->
5885 In what follows, a pointer expression E is said to be based on object P if (at some
5886 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
5887 a copy of the array object into which it formerly pointed would change the value of E.<sup><a href="#note119"><b>119)</b></a></sup>
5888 Note that ''based'' is defined only for expressions with pointer types.
5889 <p><!--para 4 -->
5890 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
5891 access the value of the object X that it designates, and X is also modified (by any means),
5892 then the following requirements apply: T shall not be const-qualified. Every other lvalue
5893 used to access the value of X shall also have its address based on P. Every access that
5894 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
5895 is assigned the value of a pointer expression E that is based on another restricted pointer
5896 object P2, associated with block B2, then either the execution of B2 shall begin before
5897 the execution of B, or the execution of B2 shall end prior to the assignment. If these
5898 requirements are not met, then the behavior is undefined.
5899 <p><!--para 5 -->
5900 Here an execution of B means that portion of the execution of the program that would
5901 correspond to the lifetime of an object with scalar type and automatic storage duration
5903 <!--page 123 -->
5904 associated with B.
5905 <p><!--para 6 -->
5906 A translator is free to ignore any or all aliasing implications of uses of restrict.
5907 <p><!--para 7 -->
5908 EXAMPLE 1 The file scope declarations
5909 <pre>
5910 int * restrict a;
5911 int * restrict b;
5912 extern int c[];
5913 </pre>
5914 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
5915 program, then it is never accessed using either of the other two.
5917 <p><!--para 8 -->
5918 EXAMPLE 2 The function parameter declarations in the following example
5919 <pre>
5920 void f(int n, int * restrict p, int * restrict q)
5921 {
5922 while (n-- > 0)
5923 *p++ = *q++;
5924 }
5925 </pre>
5926 assert that, during each execution of the function, if an object is accessed through one of the pointer
5927 parameters, then it is not also accessed through the other.
5928 <p><!--para 9 -->
5929 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
5930 analysis of function f without examining any of the calls of f in the program. The cost is that the
5931 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
5932 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
5933 both p and q.
5934 <pre>
5935 void g(void)
5936 {
5937 extern int d[100];
5938 f(50, d + 50, d); // valid
5939 f(50, d + 1, d); // undefined behavior
5940 }
5941 </pre>
5943 <p><!--para 10 -->
5944 EXAMPLE 3 The function parameter declarations
5945 <pre>
5946 void h(int n, int * restrict p, int * restrict q, int * restrict r)
5947 {
5948 int i;
5949 for (i = 0; i < n; i++)
5950 p[i] = q[i] + r[i];
5951 }
5952 </pre>
5953 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
5954 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
5955 modified within function h.
5957 <p><!--para 11 -->
5958 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
5959 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
5960 between restricted pointers declared in nested blocks have defined behavior.
5961 <!--page 124 -->
5962 <pre>
5963 {
5964 int * restrict p1;
5965 int * restrict q1;
5966 p1 = q1; // undefined behavior
5967 {
5968 int * restrict p2 = p1; // valid
5969 int * restrict q2 = q1; // valid
5970 p1 = q2; // undefined behavior
5971 p2 = q2; // undefined behavior
5972 }
5973 }
5974 </pre>
5975 <p><!--para 12 -->
5976 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
5977 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
5978 example, this permits new_vector to return a vector.
5979 <pre>
5980 typedef struct { int n; float * restrict v; } vector;
5981 vector new_vector(int n)
5982 {
5983 vector t;
5984 t.n = n;
5985 t.v = malloc(n * sizeof (float));
5986 return t;
5987 }
5988 </pre>
5991 <p><b>Footnotes</b>
5992 <p><small><a name="note119" href="#note119">119)</a> In other words, E depends on the value of P itself rather than on the value of an object referenced
5993 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
5994 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
5995 expressions *p and p[1] are not.
5996 </small>
5999 <p><b>Syntax</b>
6000 <p><!--para 1 -->
6001 <pre>
6002 function-specifier:
6003 inline
6004 </pre>
6005 <p><b>Constraints</b>
6006 <p><!--para 2 -->
6007 Function specifiers shall be used only in the declaration of an identifier for a function.
6008 <p><!--para 3 -->
6009 An inline definition of a function with external linkage shall not contain a definition of a
6010 modifiable object with static storage duration, and shall not contain a reference to an
6011 identifier with internal linkage.
6012 <p><!--para 4 -->
6013 In a hosted environment, the inline function specifier shall not appear in a declaration
6014 of main.
6015 <p><b>Semantics</b>
6016 <p><!--para 5 -->
6017 A function declared with an inline function specifier is an inline function. The
6018 function specifier may appear more than once; the behavior is the same as if it appeared
6019 only once. Making a function an inline function suggests that calls to the function be as
6020 fast as possible.<sup><a href="#note120"><b>120)</b></a></sup> The extent to which such suggestions are effective is
6022 <p><!--para 6 -->
6023 Any function with internal linkage can be an inline function. For a function with external
6024 linkage, the following restrictions apply: If a function is declared with an inline
6025 <!--page 125 -->
6026 function specifier, then it shall also be defined in the same translation unit. If all of the
6027 file scope declarations for a function in a translation unit include the inline function
6028 specifier without extern, then the definition in that translation unit is an inline
6029 definition. An inline definition does not provide an external definition for the function,
6030 and does not forbid an external definition in another translation unit. An inline definition
6031 provides an alternative to an external definition, which a translator may use to implement
6032 any call to the function in the same translation unit. It is unspecified whether a call to the
6033 function uses the inline definition or the external definition.<sup><a href="#note122"><b>122)</b></a></sup>
6034 <p><!--para 7 -->
6035 EXAMPLE The declaration of an inline function with external linkage can result in either an external
6036 definition, or a definition available for use only within the translation unit. A file scope declaration with
6037 extern creates an external definition. The following example shows an entire translation unit.
6038 <pre>
6039 inline double fahr(double t)
6040 {
6041 return (9.0 * t) / 5.0 + 32.0;
6042 }
6043 inline double cels(double t)
6044 {
6045 return (5.0 * (t - 32.0)) / 9.0;
6046 }
6047 extern double fahr(double); // creates an external definition
6048 double convert(int is_fahr, double temp)
6049 {
6050 /* A translator may perform inline substitutions */
6051 return is_fahr ? cels(temp) : fahr(temp);
6052 }
6053 </pre>
6054 <p><!--para 8 -->
6055 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
6056 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
6057 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
6058 definition are distinct and either may be used for the call.
6063 <!--page 126 -->
6065 <p><b>Footnotes</b>
6066 <p><small><a name="note120" href="#note120">120)</a> By using, for example, an alternative to the usual function call mechanism, such as ''inline
6067 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
6068 Therefore, for example, the expansion of a macro used within the body of the function uses the
6069 definition it had at the point the function body appears, and not where the function is called; and
6070 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
6071 single address, regardless of the number of inline definitions that occur in addition to the external
6072 definition.
6073 </small>
6074 <p><small><a name="note121" href="#note121">121)</a> For example, an implementation might never perform inline substitution, or might only perform inline
6075 substitutions to calls in the scope of an inline declaration.
6076 </small>
6077 <p><small><a name="note122" href="#note122">122)</a> Since an inline definition is distinct from the corresponding external definition and from any other
6078 corresponding inline definitions in other translation units, all corresponding objects with static storage
6079 duration are also distinct in each of the definitions.
6080 </small>
6083 <p><b>Syntax</b>
6084 <p><!--para 1 -->
6085 <pre>
6086 declarator:
6087 pointer<sub>opt</sub> direct-declarator
6088 direct-declarator:
6089 identifier
6090 ( declarator )
6091 direct-declarator [ type-qualifier-list<sub>opt</sub> assignment-expression<sub>opt</sub> ]
6092 direct-declarator [ static type-qualifier-list<sub>opt</sub> assignment-expression ]
6093 direct-declarator [ type-qualifier-list static assignment-expression ]
6094 direct-declarator [ type-qualifier-list<sub>opt</sub> * ]
6095 direct-declarator ( parameter-type-list )
6096 direct-declarator ( identifier-list<sub>opt</sub> )
6097 pointer:
6098 * type-qualifier-list<sub>opt</sub>
6099 * type-qualifier-list<sub>opt</sub> pointer
6100 type-qualifier-list:
6101 type-qualifier
6102 type-qualifier-list type-qualifier
6103 parameter-type-list:
6104 parameter-list
6105 parameter-list , ...
6106 parameter-list:
6107 parameter-declaration
6108 parameter-list , parameter-declaration
6109 parameter-declaration:
6110 declaration-specifiers declarator
6111 declaration-specifiers abstract-declarator<sub>opt</sub>
6112 identifier-list:
6113 identifier
6114 identifier-list , identifier
6115 </pre>
6116 <p><b>Semantics</b>
6117 <p><!--para 2 -->
6118 Each declarator declares one identifier, and asserts that when an operand of the same
6119 form as the declarator appears in an expression, it designates a function or object with the
6120 scope, storage duration, and type indicated by the declaration specifiers.
6121 <p><!--para 3 -->
6122 A full declarator is a declarator that is not part of another declarator. The end of a full
6123 declarator is a sequence point. If, in the nested sequence of declarators in a full
6124 <!--page 127 -->
6125 declarator, there is a declarator specifying a variable length array type, the type specified
6126 by the full declarator is said to be variably modified. Furthermore, any type derived by
6127 declarator type derivation from a variably modified type is itself variably modified.
6128 <p><!--para 4 -->
6129 In the following subclauses, consider a declaration
6130 <pre>
6131 T D1
6132 </pre>
6133 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
6134 a declarator that contains an identifier ident. The type specified for the identifier ident in
6135 the various forms of declarator is described inductively using this notation.
6136 <p><!--para 5 -->
6137 If, in the declaration ''T D1'', D1 has the form
6138 <pre>
6139 identifier
6140 </pre>
6141 then the type specified for ident is T .
6142 <p><!--para 6 -->
6143 If, in the declaration ''T D1'', D1 has the form
6144 <pre>
6145 ( D )
6146 </pre>
6147 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
6148 parentheses is identical to the unparenthesized declarator, but the binding of complicated
6149 declarators may be altered by parentheses.
6150 <p><b>Implementation limits</b>
6151 <p><!--para 7 -->
6152 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of pointer, array, and
6153 function declarators that modify an arithmetic, structure, union, or incomplete type, either
6154 directly or via one or more typedefs.
6155 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), type definitions (<a href="#6.7.7">6.7.7</a>).
6158 <p><b>Semantics</b>
6159 <p><!--para 1 -->
6160 If, in the declaration ''T D1'', D1 has the form
6161 <pre>
6162 * type-qualifier-list<sub>opt</sub> D
6163 </pre>
6164 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
6165 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
6166 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
6167 <p><!--para 2 -->
6168 For two pointer types to be compatible, both shall be identically qualified and both shall
6169 be pointers to compatible types.
6170 <p><!--para 3 -->
6171 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
6172 to a constant value'' and a ''constant pointer to a variable value''.
6173 <!--page 128 -->
6174 <pre>
6175 const int *ptr_to_constant;
6176 int *const constant_ptr;
6177 </pre>
6178 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
6179 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
6180 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
6181 same location.
6182 <p><!--para 4 -->
6183 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
6184 type ''pointer to int''.
6185 <pre>
6186 typedef int *int_ptr;
6187 const int_ptr constant_ptr;
6188 </pre>
6189 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
6193 <p><b>Constraints</b>
6194 <p><!--para 1 -->
6195 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
6196 an expression or *. If they delimit an expression (which specifies the size of an array), the
6197 expression shall have an integer type. If the expression is a constant expression, it shall
6198 have a value greater than zero. The element type shall not be an incomplete or function
6199 type. The optional type qualifiers and the keyword static shall appear only in a
6200 declaration of a function parameter with an array type, and then only in the outermost
6201 array type derivation.
6202 <p><!--para 2 -->
6203 An ordinary identifier (as defined in <a href="#6.2.3">6.2.3</a>) that has a variably modified type shall have
6204 either block scope and no linkage or function prototype scope. If an identifier is declared
6205 to be an object with static storage duration, it shall not have a variable length array type.
6206 <p><b>Semantics</b>
6207 <p><!--para 3 -->
6208 If, in the declaration ''T D1'', D1 has one of the forms:
6209 <pre>
6210 D[ type-qualifier-list<sub>opt</sub> assignment-expression<sub>opt</sub> ]
6211 D[ static type-qualifier-list<sub>opt</sub> assignment-expression ]
6212 D[ type-qualifier-list static assignment-expression ]
6213 D[ type-qualifier-list<sub>opt</sub> * ]
6214 </pre>
6215 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
6216 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note123"><b>123)</b></a></sup>
6217 (See <a href="#6.7.5.3">6.7.5.3</a> for the meaning of the optional type qualifiers and the keyword static.)
6218 <p><!--para 4 -->
6219 If the size is not present, the array type is an incomplete type. If the size is * instead of
6220 being an expression, the array type is a variable length array type of unspecified size,
6221 which can only be used in declarations with function prototype scope;<sup><a href="#note124"><b>124)</b></a></sup> such arrays are
6222 nonetheless complete types. If the size is an integer constant expression and the element
6224 <!--page 129 -->
6225 type has a known constant size, the array type is not a variable length array type;
6226 otherwise, the array type is a variable length array type.
6227 <p><!--para 5 -->
6228 If the size is an expression that is not an integer constant expression: if it occurs in a
6229 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
6230 each time it is evaluated it shall have a value greater than zero. The size of each instance
6231 of a variable length array type does not change during its lifetime. Where a size
6232 expression is part of the operand of a sizeof operator and changing the value of the
6233 size expression would not affect the result of the operator, it is unspecified whether or not
6234 the size expression is evaluated.
6235 <p><!--para 6 -->
6236 For two array types to be compatible, both shall have compatible element types, and if
6237 both size specifiers are present, and are integer constant expressions, then both size
6238 specifiers shall have the same constant value. If the two array types are used in a context
6239 which requires them to be compatible, it is undefined behavior if the two size specifiers
6240 evaluate to unequal values.
6241 <p><!--para 7 -->
6242 EXAMPLE 1
6243 <pre>
6244 float fa[11], *afp[17];
6245 </pre>
6246 declares an array of float numbers and an array of pointers to float numbers.
6248 <p><!--para 8 -->
6249 EXAMPLE 2 Note the distinction between the declarations
6250 <pre>
6251 extern int *x;
6252 extern int y[];
6253 </pre>
6254 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
6255 (an incomplete type), the storage for which is defined elsewhere.
6257 <p><!--para 9 -->
6258 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
6259 <pre>
6260 extern int n;
6261 extern int m;
6262 void fcompat(void)
6263 {
6264 int a[n][6][m];
6265 int (*p)[4][n+1];
6266 int c[n][n][6][m];
6267 int (*r)[n][n][n+1];
6268 p = a; // invalid: not compatible because 4 != 6
6269 r = c; // compatible, but defined behavior only if
6270 // n == 6 and m == n+1
6271 }
6272 </pre>
6277 <!--page 130 -->
6278 <p><!--para 10 -->
6279 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
6280 function prototype scope. Array objects declared with the static or extern storage-class specifier
6281 cannot have a variable length array (VLA) type. However, an object declared with the static storage-
6282 class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all identifiers declared with a
6283 VM type have to be ordinary identifiers and cannot, therefore, be members of structures or unions.
6284 <pre>
6285 extern int n;
6286 int A[n]; // invalid: file scope VLA
6287 extern int (*p2)[n]; // invalid: file scope VM
6288 int B[100]; // valid: file scope but not VM
6289 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
6290 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
6291 {
6292 typedef int VLA[m][m]; // valid: block scope typedef VLA
6293 struct tag {
6294 int (*y)[n]; // invalid: y not ordinary identifier
6295 int z[n]; // invalid: z not ordinary identifier
6296 };
6297 int D[m]; // valid: auto VLA
6298 static int E[m]; // invalid: static block scope VLA
6299 extern int F[m]; // invalid: F has linkage and is VLA
6300 int (*s)[m]; // valid: auto pointer to VLA
6301 extern int (*r)[m]; // invalid: r has linkage and points to VLA
6302 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
6303 }
6304 </pre>
6306 <p><b> Forward references</b>: function declarators (<a href="#6.7.5.3">6.7.5.3</a>), function definitions (<a href="#6.9.1">6.9.1</a>),
6309 <p><b>Footnotes</b>
6310 <p><small><a name="note123" href="#note123">123)</a> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
6311 </small>
6312 <p><small><a name="note124" href="#note124">124)</a> Thus, * can be used only in function declarations that are not definitions (see <a href="#6.7.5.3">6.7.5.3</a>).
6313 </small>
6315 <h5><a name="6.7.5.3" href="#6.7.5.3">6.7.5.3 Function declarators (including prototypes)</a></h5>
6316 <p><b>Constraints</b>
6317 <p><!--para 1 -->
6318 A function declarator shall not specify a return type that is a function type or an array
6319 type.
6320 <p><!--para 2 -->
6321 The only storage-class specifier that shall occur in a parameter declaration is register.
6322 <p><!--para 3 -->
6323 An identifier list in a function declarator that is not part of a definition of that function
6324 shall be empty.
6325 <p><!--para 4 -->
6326 After adjustment, the parameters in a parameter type list in a function declarator that is
6327 part of a definition of that function shall not have incomplete type.
6328 <p><b>Semantics</b>
6329 <p><!--para 5 -->
6330 If, in the declaration ''T D1'', D1 has the form
6331 <pre>
6332 D( parameter-type-list )
6333 </pre>
6334 or
6335 <!--page 131 -->
6336 <pre>
6337 D( identifier-list<sub>opt</sub> )
6338 </pre>
6339 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
6340 T '', then the type specified for ident is ''derived-declarator-type-list function returning
6341 T ''.
6342 <p><!--para 6 -->
6343 A parameter type list specifies the types of, and may declare identifiers for, the
6344 parameters of the function.
6345 <p><!--para 7 -->
6346 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
6347 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
6348 array type derivation. If the keyword static also appears within the [ and ] of the
6349 array type derivation, then for each call to the function, the value of the corresponding
6350 actual argument shall provide access to the first element of an array with at least as many
6351 elements as specified by the size expression.
6352 <p><!--para 8 -->
6353 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
6355 <p><!--para 9 -->
6356 If the list terminates with an ellipsis (, ...), no information about the number or types
6358 <p><!--para 10 -->
6359 The special case of an unnamed parameter of type void as the only item in the list
6360 specifies that the function has no parameters.
6361 <p><!--para 11 -->
6362 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
6363 parameter name, it shall be taken as a typedef name.
6364 <p><!--para 12 -->
6365 If the function declarator is not part of a definition of that function, parameters may have
6366 incomplete type and may use the [*] notation in their sequences of declarator specifiers
6367 to specify variable length array types.
6368 <p><!--para 13 -->
6369 The storage-class specifier in the declaration specifiers for a parameter declaration, if
6370 present, is ignored unless the declared parameter is one of the members of the parameter
6371 type list for a function definition.
6372 <p><!--para 14 -->
6373 An identifier list declares only the identifiers of the parameters of the function. An empty
6374 list in a function declarator that is part of a definition of that function specifies that the
6375 function has no parameters. The empty list in a function declarator that is not part of a
6376 definition of that function specifies that no information about the number or types of the
6378 <p><!--para 15 -->
6379 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note127"><b>127)</b></a></sup>
6382 <!--page 132 -->
6383 Moreover, the parameter type lists, if both are present, shall agree in the number of
6384 parameters and in use of the ellipsis terminator; corresponding parameters shall have
6385 compatible types. If one type has a parameter type list and the other type is specified by a
6386 function declarator that is not part of a function definition and that contains an empty
6387 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
6388 parameter shall be compatible with the type that results from the application of the
6389 default argument promotions. If one type has a parameter type list and the other type is
6390 specified by a function definition that contains a (possibly empty) identifier list, both shall
6391 agree in the number of parameters, and the type of each prototype parameter shall be
6392 compatible with the type that results from the application of the default argument
6393 promotions to the type of the corresponding identifier. (In the determination of type
6394 compatibility and of a composite type, each parameter declared with function or array
6395 type is taken as having the adjusted type and each parameter declared with qualified type
6396 is taken as having the unqualified version of its declared type.)
6397 <p><!--para 16 -->
6398 EXAMPLE 1 The declaration
6399 <pre>
6400 int f(void), *fip(), (*pfi)();
6401 </pre>
6402 declares a function f with no parameters returning an int, a function fip with no parameter specification
6403 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
6404 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
6405 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
6406 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
6407 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
6408 designator, which is then used to call the function; it returns an int.
6409 <p><!--para 17 -->
6410 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
6411 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
6412 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
6413 the identifier of the pointer pfi has block scope and no linkage.
6415 <p><!--para 18 -->
6416 EXAMPLE 2 The declaration
6417 <pre>
6418 int (*apfi[3])(int *x, int *y);
6419 </pre>
6420 declares an array apfi of three pointers to functions returning int. Each of these functions has two
6421 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
6422 go out of scope at the end of the declaration of apfi.
6424 <p><!--para 19 -->
6425 EXAMPLE 3 The declaration
6426 <pre>
6427 int (*fpfi(int (*)(long), int))(int, ...);
6428 </pre>
6429 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
6430 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
6431 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
6432 additional arguments of any type.
6433 <!--page 133 -->
6434 <p><!--para 20 -->
6435 EXAMPLE 4 The following prototype has a variably modified parameter.
6436 <pre>
6437 void addscalar(int n, int m,
6438 double a[n][n*m+300], double x);
6439 int main()
6440 {
6441 double b[4][308];
6443 return 0;
6444 }
6445 void addscalar(int n, int m,
6446 double a[n][n*m+300], double x)
6447 {
6448 for (int i = 0; i < n; i++)
6449 for (int j = 0, k = n*m+300; j < k; j++)
6450 // a is a pointer to a VLA with n*m+300 elements
6451 a[i][j] += x;
6452 }
6453 </pre>
6455 <p><!--para 21 -->
6456 EXAMPLE 5 The following are all compatible function prototype declarators.
6457 <pre>
6458 double maximum(int n, int m, double a[n][m]);
6459 double maximum(int n, int m, double a[*][*]);
6460 double maximum(int n, int m, double a[ ][*]);
6461 double maximum(int n, int m, double a[ ][m]);
6462 </pre>
6463 as are:
6464 <pre>
6465 void f(double (* restrict a)[5]);
6466 void f(double a[restrict][5]);
6467 void f(double a[restrict 3][5]);
6468 void f(double a[restrict static 3][5]);
6469 </pre>
6470 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
6471 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
6473 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>), type names (<a href="#6.7.6">6.7.6</a>).
6474 <!--page 134 -->
6476 <p><b>Footnotes</b>
6477 <p><small><a name="note125" href="#note125">125)</a> The macros defined in the <a href="#7.15"><stdarg.h></a> header (<a href="#7.15">7.15</a>) may be used to access arguments that
6478 correspond to the ellipsis.
6479 </small>
6480 <p><small><a name="note126" href="#note126">126)</a> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
6481 </small>
6482 <p><small><a name="note127" href="#note127">127)</a> If both function types are ''old style'', parameter types are not compared.
6483 </small>
6486 <p><b>Syntax</b>
6487 <p><!--para 1 -->
6488 <pre>
6489 type-name:
6490 specifier-qualifier-list abstract-declarator<sub>opt</sub>
6491 abstract-declarator:
6492 pointer
6493 pointer<sub>opt</sub> direct-abstract-declarator
6494 direct-abstract-declarator:
6495 ( abstract-declarator )
6496 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list<sub>opt</sub>
6497 assignment-expression<sub>opt</sub> ]
6498 direct-abstract-declarator<sub>opt</sub> [ static type-qualifier-list<sub>opt</sub>
6499 assignment-expression ]
6500 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list static
6501 assignment-expression ]
6502 direct-abstract-declarator<sub>opt</sub> [ * ]
6503 direct-abstract-declarator<sub>opt</sub> ( parameter-type-list<sub>opt</sub> )
6504 </pre>
6505 <p><b>Semantics</b>
6506 <p><!--para 2 -->
6507 In several contexts, it is necessary to specify a type. This is accomplished using a type
6508 name, which is syntactically a declaration for a function or an object of that type that
6510 <p><!--para 3 -->
6511 EXAMPLE The constructions
6512 <pre>
6513 (a) int
6514 (b) int *
6515 (c) int *[3]
6516 (d) int (*)[3]
6517 (e) int (*)[*]
6518 (f) int *()
6519 (g) int (*)(void)
6520 (h) int (*const [])(unsigned int, ...)
6521 </pre>
6522 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
6523 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
6524 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
6525 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
6526 parameter that has type unsigned int and an unspecified number of other parameters, returning an
6527 int.
6532 <!--page 135 -->
6534 <p><b>Footnotes</b>
6535 <p><small><a name="note128" href="#note128">128)</a> As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
6536 parameter specification'', rather than redundant parentheses around the omitted identifier.
6537 </small>
6540 <p><b>Syntax</b>
6541 <p><!--para 1 -->
6542 <pre>
6543 typedef-name:
6544 identifier
6545 </pre>
6546 <p><b>Constraints</b>
6547 <p><!--para 2 -->
6548 If a typedef name specifies a variably modified type then it shall have block scope.
6549 <p><b>Semantics</b>
6550 <p><!--para 3 -->
6551 In a declaration whose storage-class specifier is typedef, each declarator defines an
6552 identifier to be a typedef name that denotes the type specified for the identifier in the way
6553 described in <a href="#6.7.5">6.7.5</a>. Any array size expressions associated with variable length array
6554 declarators are evaluated each time the declaration of the typedef name is reached in the
6555 order of execution. A typedef declaration does not introduce a new type, only a
6556 synonym for the type so specified. That is, in the following declarations:
6557 <pre>
6558 typedef T type_ident;
6559 type_ident D;
6560 </pre>
6561 type_ident is defined as a typedef name with the type specified by the declaration
6562 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
6563 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
6564 typedef name shares the same name space as other identifiers declared in ordinary
6565 declarators.
6566 <p><!--para 4 -->
6567 EXAMPLE 1 After
6568 <pre>
6569 typedef int MILES, KLICKSP();
6570 typedef struct { double hi, lo; } range;
6571 </pre>
6572 the constructions
6573 <pre>
6574 MILES distance;
6575 extern KLICKSP *metricp;
6576 range x;
6577 range z, *zp;
6578 </pre>
6579 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
6580 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
6581 such a structure. The object distance has a type compatible with any other int object.
6583 <p><!--para 5 -->
6584 EXAMPLE 2 After the declarations
6585 <pre>
6586 typedef struct s1 { int x; } t1, *tp1;
6587 typedef struct s2 { int x; } t2, *tp2;
6588 </pre>
6589 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
6590 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
6591 <!--page 136 -->
6592 <p><!--para 6 -->
6593 EXAMPLE 3 The following obscure constructions
6594 <pre>
6595 typedef signed int t;
6596 typedef int plain;
6597 struct tag {
6598 unsigned t:4;
6599 const t:5;
6600 plain r:5;
6601 };
6602 </pre>
6603 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
6604 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
6605 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
6606 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
6607 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
6608 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
6609 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
6610 in an inner scope by
6611 <pre>
6612 t f(t (t));
6613 long t;
6614 </pre>
6615 then a function f is declared with type ''function returning signed int with one unnamed parameter
6616 with type pointer to function returning signed int with one unnamed parameter with type signed
6617 int'', and an identifier t with type long int.
6619 <p><!--para 7 -->
6620 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
6621 following declarations of the signal function specify exactly the same type, the first without making use
6622 of any typedef names.
6623 <pre>
6624 typedef void fv(int), (*pfv)(int);
6625 void (*signal(int, void (*)(int)))(int);
6626 fv *signal(int, fv *);
6627 pfv signal(int, pfv);
6628 </pre>
6630 <p><!--para 8 -->
6631 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
6632 time the typedef name is defined, not each time it is used:
6633 <!--page 137 -->
6634 <pre>
6635 void copyt(int n)
6636 {
6637 typedef int B[n]; // B is n ints, n evaluated now
6638 n += 1;
6639 B a; // a is n ints, n without += 1
6640 int b[n]; // a and b are different sizes
6641 for (int i = 1; i < n; i++)
6642 a[i-1] = b[i];
6643 }
6644 </pre>
6647 <p><b>Syntax</b>
6648 <p><!--para 1 -->
6649 <pre>
6650 initializer:
6651 assignment-expression
6652 { initializer-list }
6653 { initializer-list , }
6654 initializer-list:
6655 designation<sub>opt</sub> initializer
6656 initializer-list , designation<sub>opt</sub> initializer
6657 designation:
6658 designator-list =
6659 designator-list:
6660 designator
6661 designator-list designator
6662 designator:
6663 [ constant-expression ]
6664 . identifier
6665 </pre>
6666 <p><b>Constraints</b>
6667 <p><!--para 2 -->
6668 No initializer shall attempt to provide a value for an object not contained within the entity
6669 being initialized.
6670 <p><!--para 3 -->
6671 The type of the entity to be initialized shall be an array of unknown size or an object type
6672 that is not a variable length array type.
6673 <p><!--para 4 -->
6674 All the expressions in an initializer for an object that has static storage duration shall be
6675 constant expressions or string literals.
6676 <p><!--para 5 -->
6677 If the declaration of an identifier has block scope, and the identifier has external or
6678 internal linkage, the declaration shall have no initializer for the identifier.
6679 <p><!--para 6 -->
6680 If a designator has the form
6681 <pre>
6682 [ constant-expression ]
6683 </pre>
6684 then the current object (defined below) shall have array type and the expression shall be
6685 an integer constant expression. If the array is of unknown size, any nonnegative value is
6686 valid.
6687 <p><!--para 7 -->
6688 If a designator has the form
6689 <pre>
6690 . identifier
6691 </pre>
6692 then the current object (defined below) shall have structure or union type and the
6693 identifier shall be the name of a member of that type.
6694 <!--page 138 -->
6695 <p><b>Semantics</b>
6696 <p><!--para 8 -->
6697 An initializer specifies the initial value stored in an object.
6698 <p><!--para 9 -->
6699 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
6700 members of objects of structure and union type do not participate in initialization.
6701 Unnamed members of structure objects have indeterminate value even after initialization.
6702 <p><!--para 10 -->
6703 If an object that has automatic storage duration is not initialized explicitly, its value is
6704 indeterminate. If an object that has static storage duration is not initialized explicitly,
6705 then:
6706 <ul>
6707 <li> if it has pointer type, it is initialized to a null pointer;
6708 <li> if it has arithmetic type, it is initialized to (positive or unsigned) zero;
6709 <li> if it is an aggregate, every member is initialized (recursively) according to these rules;
6710 <li> if it is a union, the first named member is initialized (recursively) according to these
6711 rules.
6712 </ul>
6713 <p><!--para 11 -->
6714 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
6715 initial value of the object is that of the expression (after conversion); the same type
6716 constraints and conversions as for simple assignment apply, taking the type of the scalar
6717 to be the unqualified version of its declared type.
6718 <p><!--para 12 -->
6719 The rest of this subclause deals with initializers for objects that have aggregate or union
6720 type.
6721 <p><!--para 13 -->
6722 The initializer for a structure or union object that has automatic storage duration shall be
6723 either an initializer list as described below, or a single expression that has compatible
6724 structure or union type. In the latter case, the initial value of the object, including
6725 unnamed members, is that of the expression.
6726 <p><!--para 14 -->
6727 An array of character type may be initialized by a character string literal, optionally
6728 enclosed in braces. Successive characters of the character string literal (including the
6729 terminating null character if there is room or if the array is of unknown size) initialize the
6730 elements of the array.
6731 <p><!--para 15 -->
6732 An array with element type compatible with wchar_t may be initialized by a wide
6733 string literal, optionally enclosed in braces. Successive wide characters of the wide string
6734 literal (including the terminating null wide character if there is room or if the array is of
6735 unknown size) initialize the elements of the array.
6736 <p><!--para 16 -->
6737 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
6738 enclosed list of initializers for the elements or named members.
6739 <p><!--para 17 -->
6740 Each brace-enclosed initializer list has an associated current object. When no
6741 designations are present, subobjects of the current object are initialized in order according
6742 to the type of the current object: array elements in increasing subscript order, structure
6743 <!--page 139 -->
6744 members in declaration order, and the first named member of a union.<sup><a href="#note129"><b>129)</b></a></sup> In contrast, a
6745 designation causes the following initializer to begin initialization of the subobject
6746 described by the designator. Initialization then continues forward in order, beginning
6747 with the next subobject after that described by the designator.<sup><a href="#note130"><b>130)</b></a></sup>
6748 <p><!--para 18 -->
6749 Each designator list begins its description with the current object associated with the
6750 closest surrounding brace pair. Each item in the designator list (in order) specifies a
6751 particular member of its current object and changes the current object for the next
6752 designator (if any) to be that member.<sup><a href="#note131"><b>131)</b></a></sup> The current object that results at the end of the
6753 designator list is the subobject to be initialized by the following initializer.
6754 <p><!--para 19 -->
6755 The initialization shall occur in initializer list order, each initializer provided for a
6756 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note132"><b>132)</b></a></sup>
6757 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
6758 objects that have static storage duration.
6759 <p><!--para 20 -->
6760 If the aggregate or union contains elements or members that are aggregates or unions,
6761 these rules apply recursively to the subaggregates or contained unions. If the initializer of
6762 a subaggregate or contained union begins with a left brace, the initializers enclosed by
6763 that brace and its matching right brace initialize the elements or members of the
6764 subaggregate or the contained union. Otherwise, only enough initializers from the list are
6765 taken to account for the elements or members of the subaggregate or the first member of
6766 the contained union; any remaining initializers are left to initialize the next element or
6767 member of the aggregate of which the current subaggregate or contained union is a part.
6768 <p><!--para 21 -->
6769 If there are fewer initializers in a brace-enclosed list than there are elements or members
6770 of an aggregate, or fewer characters in a string literal used to initialize an array of known
6771 size than there are elements in the array, the remainder of the aggregate shall be
6772 initialized implicitly the same as objects that have static storage duration.
6773 <p><!--para 22 -->
6774 If an array of unknown size is initialized, its size is determined by the largest indexed
6775 element with an explicit initializer. At the end of its initializer list, the array no longer
6776 has incomplete type.
6780 <!--page 140 -->
6781 <p><!--para 23 -->
6782 The order in which any side effects occur among the initialization list expressions is
6784 <p><!--para 24 -->
6785 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
6786 <pre>
6788 double complex c = 5 + 3 * I;
6789 </pre>
6790 define and initialize i with the value 3 and c with the value 5.0 + i3.0.
6792 <p><!--para 25 -->
6793 EXAMPLE 2 The declaration
6794 <pre>
6795 int x[] = { 1, 3, 5 };
6796 </pre>
6797 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
6798 and there are three initializers.
6800 <p><!--para 26 -->
6801 EXAMPLE 3 The declaration
6802 <pre>
6803 int y[4][3] = {
6804 { 1, 3, 5 },
6805 { 2, 4, 6 },
6806 { 3, 5, 7 },
6807 };
6808 </pre>
6809 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
6810 y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
6811 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
6812 been achieved by
6813 <pre>
6814 int y[4][3] = {
6815 1, 3, 5, 2, 4, 6, 3, 5, 7
6816 };
6817 </pre>
6818 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
6819 next three are taken successively for y[1] and y[2].
6821 <p><!--para 27 -->
6822 EXAMPLE 4 The declaration
6823 <pre>
6824 int z[4][3] = {
6825 { 1 }, { 2 }, { 3 }, { 4 }
6826 };
6827 </pre>
6828 initializes the first column of z as specified and initializes the rest with zeros.
6830 <p><!--para 28 -->
6831 EXAMPLE 5 The declaration
6832 <pre>
6833 struct { int a[3], b; } w[] = { { 1 }, 2 };
6834 </pre>
6835 is a definition with an inconsistently bracketed initialization. It defines an array with two element
6836 structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
6841 <!--page 141 -->
6842 <p><!--para 29 -->
6843 EXAMPLE 6 The declaration
6844 <pre>
6845 short q[4][3][2] = {
6846 { 1 },
6847 { 2, 3 },
6848 { 4, 5, 6 }
6849 };
6850 </pre>
6851 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
6852 object: q[0][0][0] is 1, q[1][0][0] is 2, q[1][0][1] is 3, and 4, 5, and 6 initialize
6853 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
6854 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
6855 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
6856 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
6857 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
6858 diagnostic message would have been issued. The same initialization result could have been achieved by:
6859 <pre>
6860 short q[4][3][2] = {
6861 1, 0, 0, 0, 0, 0,
6862 2, 3, 0, 0, 0, 0,
6863 4, 5, 6
6864 };
6865 </pre>
6866 or by:
6867 <pre>
6868 short q[4][3][2] = {
6869 {
6870 { 1 },
6871 },
6872 {
6873 { 2, 3 },
6874 },
6875 {
6876 { 4, 5 },
6877 { 6 },
6878 }
6879 };
6880 </pre>
6881 in a fully bracketed form.
6882 <p><!--para 30 -->
6883 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
6884 cause confusion.
6886 <p><!--para 31 -->
6887 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
6888 declaration
6889 <pre>
6890 typedef int A[]; // OK - declared with block scope
6891 </pre>
6892 the declaration
6893 <pre>
6894 A a = { 1, 2 }, b = { 3, 4, 5 };
6895 </pre>
6896 is identical to
6897 <pre>
6898 int a[] = { 1, 2 }, b[] = { 3, 4, 5 };
6899 </pre>
6900 due to the rules for incomplete types.
6901 <!--page 142 -->
6902 <p><!--para 32 -->
6903 EXAMPLE 8 The declaration
6904 <pre>
6906 </pre>
6907 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
6908 This declaration is identical to
6909 <pre>
6910 char s[] = { 'a', 'b', 'c', '\0' },
6911 t[] = { 'a', 'b', 'c' };
6912 </pre>
6913 The contents of the arrays are modifiable. On the other hand, the declaration
6914 <pre>
6916 </pre>
6917 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
6918 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
6919 modify the contents of the array, the behavior is undefined.
6921 <p><!--para 33 -->
6922 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
6923 designators:
6924 <pre>
6925 enum { member_one, member_two };
6926 const char *nm[] = {
6929 };
6930 </pre>
6932 <p><!--para 34 -->
6933 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
6934 <pre>
6935 div_t answer = { .quot = 2, .rem = -1 };
6936 </pre>
6938 <p><!--para 35 -->
6939 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
6940 might be misunderstood:
6941 <pre>
6942 struct { int a[3], b; } w[] =
6943 { [0].a = {1}, [1].a[0] = 2 };
6944 </pre>
6946 <p><!--para 36 -->
6947 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
6948 <pre>
6949 int a[MAX] = {
6950 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
6951 };
6952 </pre>
6953 <p><!--para 37 -->
6954 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
6955 than ten, some of the values provided by the first five initializers will be overridden by the second five.
6957 <p><!--para 38 -->
6958 EXAMPLE 13 Any member of a union can be initialized:
6959 <pre>
6960 union { /* ... */ } u = { .any_member = 42 };
6961 </pre>
6963 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>).
6964 <!--page 143 -->
6966 <p><b>Footnotes</b>
6967 <p><small><a name="note129" href="#note129">129)</a> If the initializer list for a subaggregate or contained union does not begin with a left brace, its
6968 subobjects are initialized as usual, but the subaggregate or contained union does not become the
6969 current object: current objects are associated only with brace-enclosed initializer lists.
6970 </small>
6971 <p><small><a name="note130" href="#note130">130)</a> After a union member is initialized, the next object is not the next member of the union; instead, it is
6972 the next subobject of an object containing the union.
6973 </small>
6974 <p><small><a name="note131" href="#note131">131)</a> Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with
6975 the surrounding brace pair. Note, too, that each separate designator list is independent.
6976 </small>
6977 <p><small><a name="note132" href="#note132">132)</a> Any initializer for the subobject which is overridden and so not used to initialize that subobject might
6978 not be evaluated at all.
6979 </small>
6980 <p><small><a name="note133" href="#note133">133)</a> In particular, the evaluation order need not be the same as the order of subobject initialization.
6981 </small>
6984 <p><b>Syntax</b>
6985 <p><!--para 1 -->
6986 <pre>
6987 statement:
6988 labeled-statement
6989 compound-statement
6990 expression-statement
6991 selection-statement
6992 iteration-statement
6993 jump-statement
6994 </pre>
6995 <p><b>Semantics</b>
6996 <p><!--para 2 -->
6997 A statement specifies an action to be performed. Except as indicated, statements are
6998 executed in sequence.
6999 <p><!--para 3 -->
7000 A block allows a set of declarations and statements to be grouped into one syntactic unit.
7001 The initializers of objects that have automatic storage duration, and the variable length
7002 array declarators of ordinary identifiers with block scope, are evaluated and the values are
7003 stored in the objects (including storing an indeterminate value in objects without an
7004 initializer) each time the declaration is reached in the order of execution, as if it were a
7005 statement, and within each declaration in the order that declarators appear.
7006 <p><!--para 4 -->
7007 A full expression is an expression that is not part of another expression or of a declarator.
7008 Each of the following is a full expression: an initializer; the expression in an expression
7009 statement; the controlling expression of a selection statement (if or switch); the
7010 controlling expression of a while or do statement; each of the (optional) expressions of
7011 a for statement; the (optional) expression in a return statement. The end of a full
7012 expression is a sequence point.
7013 <p><b> Forward references</b>: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
7014 (<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>).
7017 <p><b>Syntax</b>
7018 <p><!--para 1 -->
7019 <pre>
7020 labeled-statement:
7021 identifier : statement
7022 case constant-expression : statement
7023 default : statement
7024 </pre>
7025 <p><b>Constraints</b>
7026 <p><!--para 2 -->
7027 A case or default label shall appear only in a switch statement. Further
7028 constraints on such labels are discussed under the switch statement.
7029 <!--page 144 -->
7030 <p><!--para 3 -->
7031 Label names shall be unique within a function.
7032 <p><b>Semantics</b>
7033 <p><!--para 4 -->
7034 Any statement may be preceded by a prefix that declares an identifier as a label name.
7035 Labels in themselves do not alter the flow of control, which continues unimpeded across
7036 them.
7037 <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>).
7040 <p><b>Syntax</b>
7041 <p><!--para 1 -->
7042 <pre>
7043 compound-statement:
7044 { block-item-list<sub>opt</sub> }
7045 block-item-list:
7046 block-item
7047 block-item-list block-item
7048 block-item:
7049 declaration
7050 statement
7051 </pre>
7052 <p><b>Semantics</b>
7053 <p><!--para 2 -->
7054 A compound statement is a block.
7057 <p><b>Syntax</b>
7058 <p><!--para 1 -->
7059 <pre>
7060 expression-statement:
7061 expression<sub>opt</sub> ;
7062 </pre>
7063 <p><b>Semantics</b>
7064 <p><!--para 2 -->
7065 The expression in an expression statement is evaluated as a void expression for its side
7067 <p><!--para 3 -->
7068 A null statement (consisting of just a semicolon) performs no operations.
7069 <p><!--para 4 -->
7070 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
7071 discarding of its value may be made explicit by converting the expression to a void expression by means of
7072 a cast:
7073 <pre>
7074 int p(int);
7075 /* ... */
7076 (void)p(0);
7077 </pre>
7081 <!--page 145 -->
7082 <p><!--para 5 -->
7083 EXAMPLE 2 In the program fragment
7084 <pre>
7085 char *s;
7086 /* ... */
7087 while (*s++ != '\0')
7088 ;
7089 </pre>
7090 a null statement is used to supply an empty loop body to the iteration statement.
7092 <p><!--para 6 -->
7093 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
7094 statement.
7095 <pre>
7096 while (loop1) {
7097 /* ... */
7098 while (loop2) {
7099 /* ... */
7100 if (want_out)
7101 goto end_loop1;
7102 /* ... */
7103 }
7104 /* ... */
7105 end_loop1: ;
7106 }
7107 </pre>
7111 <p><b>Footnotes</b>
7112 <p><small><a name="note134" href="#note134">134)</a> Such as assignments, and function calls which have side effects.
7113 </small>
7116 <p><b>Syntax</b>
7117 <p><!--para 1 -->
7118 <pre>
7119 selection-statement:
7120 if ( expression ) statement
7121 if ( expression ) statement else statement
7122 switch ( expression ) statement
7123 </pre>
7124 <p><b>Semantics</b>
7125 <p><!--para 2 -->
7126 A selection statement selects among a set of statements depending on the value of a
7127 controlling expression.
7128 <p><!--para 3 -->
7129 A selection statement is a block whose scope is a strict subset of the scope of its
7130 enclosing block. Each associated substatement is also a block whose scope is a strict
7131 subset of the scope of the selection statement.
7134 <p><b>Constraints</b>
7135 <p><!--para 1 -->
7136 The controlling expression of an if statement shall have scalar type.
7137 <p><b>Semantics</b>
7138 <p><!--para 2 -->
7139 In both forms, the first substatement is executed if the expression compares unequal to 0.
7140 In the else form, the second substatement is executed if the expression compares equal
7141 <!--page 146 -->
7142 to 0. If the first substatement is reached via a label, the second substatement is not
7143 executed.
7144 <p><!--para 3 -->
7145 An else is associated with the lexically nearest preceding if that is allowed by the
7146 syntax.
7149 <p><b>Constraints</b>
7150 <p><!--para 1 -->
7151 The controlling expression of a switch statement shall have integer type.
7152 <p><!--para 2 -->
7153 If a switch statement has an associated case or default label within the scope of an
7154 identifier with a variably modified type, the entire switch statement shall be within the
7156 <p><!--para 3 -->
7157 The expression of each case label shall be an integer constant expression and no two of
7158 the case constant expressions in the same switch statement shall have the same value
7159 after conversion. There may be at most one default label in a switch statement.
7160 (Any enclosed switch statement may have a default label or case constant
7161 expressions with values that duplicate case constant expressions in the enclosing
7162 switch statement.)
7163 <p><b>Semantics</b>
7164 <p><!--para 4 -->
7165 A switch statement causes control to jump to, into, or past the statement that is the
7166 switch body, depending on the value of a controlling expression, and on the presence of a
7167 default label and the values of any case labels on or in the switch body. A case or
7168 default label is accessible only within the closest enclosing switch statement.
7169 <p><!--para 5 -->
7170 The integer promotions are performed on the controlling expression. The constant
7171 expression in each case label is converted to the promoted type of the controlling
7172 expression. If a converted value matches that of the promoted controlling expression,
7173 control jumps to the statement following the matched case label. Otherwise, if there is
7174 a default label, control jumps to the labeled statement. If no converted case constant
7175 expression matches and there is no default label, no part of the switch body is
7176 executed.
7177 <p><b>Implementation limits</b>
7178 <p><!--para 6 -->
7179 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
7180 switch statement.
7185 <!--page 147 -->
7186 <p><!--para 7 -->
7187 EXAMPLE In the artificial program fragment
7188 <pre>
7189 switch (expr)
7190 {
7191 int i = 4;
7192 f(i);
7193 case 0:
7194 i = 17;
7195 /* falls through into default code */
7196 default:
7198 }
7199 </pre>
7200 the object whose identifier is i exists with automatic storage duration (within the block) but is never
7201 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
7202 access an indeterminate value. Similarly, the call to the function f cannot be reached.
7205 <p><b>Footnotes</b>
7206 <p><small><a name="note135" href="#note135">135)</a> That is, the declaration either precedes the switch statement, or it follows the last case or
7207 default label associated with the switch that is in the block containing the declaration.
7208 </small>
7211 <p><b>Syntax</b>
7212 <p><!--para 1 -->
7213 <pre>
7214 iteration-statement:
7215 while ( expression ) statement
7216 do statement while ( expression ) ;
7217 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
7218 for ( declaration expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
7219 </pre>
7220 <p><b>Constraints</b>
7221 <p><!--para 2 -->
7222 The controlling expression of an iteration statement shall have scalar type.
7223 <p><!--para 3 -->
7224 The declaration part of a for statement shall only declare identifiers for objects having
7225 storage class auto or register.
7226 <p><b>Semantics</b>
7227 <p><!--para 4 -->
7228 An iteration statement causes a statement called the loop body to be executed repeatedly
7229 until the controlling expression compares equal to 0. The repetition occurs regardless of
7230 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note136"><b>136)</b></a></sup>
7231 <p><!--para 5 -->
7232 An iteration statement is a block whose scope is a strict subset of the scope of its
7233 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
7234 of the iteration statement.
7239 <!--page 148 -->
7241 <p><b>Footnotes</b>
7242 <p><small><a name="note136" href="#note136">136)</a> Code jumped over is not executed. In particular, the controlling expression of a for or while
7243 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
7244 </small>
7247 <p><!--para 1 -->
7248 The evaluation of the controlling expression takes place before each execution of the loop
7249 body.
7252 <p><!--para 1 -->
7253 The evaluation of the controlling expression takes place after each execution of the loop
7254 body.
7257 <p><!--para 1 -->
7258 The statement
7259 <pre>
7260 for ( clause-1 ; expression-2 ; expression-3 ) statement
7261 </pre>
7262 behaves as follows: The expression expression-2 is the controlling expression that is
7263 evaluated before each execution of the loop body. The expression expression-3 is
7264 evaluated as a void expression after each execution of the loop body. If clause-1 is a
7265 declaration, the scope of any identifiers it declares is the remainder of the declaration and
7266 the entire loop, including the other two expressions; it is reached in the order of execution
7267 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
7268 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note137"><b>137)</b></a></sup>
7269 <p><!--para 2 -->
7270 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
7271 nonzero constant.
7273 <p><b>Footnotes</b>
7274 <p><small><a name="note137" href="#note137">137)</a> Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in
7275 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
7276 such that execution of the loop continues until the expression compares equal to 0; and expression-3
7277 specifies an operation (such as incrementing) that is performed after each iteration.
7278 </small>
7281 <p><b>Syntax</b>
7282 <p><!--para 1 -->
7283 <pre>
7284 jump-statement:
7285 goto identifier ;
7286 continue ;
7287 break ;
7288 return expression<sub>opt</sub> ;
7289 </pre>
7290 <p><b>Semantics</b>
7291 <p><!--para 2 -->
7292 A jump statement causes an unconditional jump to another place.
7297 <!--page 149 -->
7300 <p><b>Constraints</b>
7301 <p><!--para 1 -->
7302 The identifier in a goto statement shall name a label located somewhere in the enclosing
7303 function. A goto statement shall not jump from outside the scope of an identifier having
7304 a variably modified type to inside the scope of that identifier.
7305 <p><b>Semantics</b>
7306 <p><!--para 2 -->
7307 A goto statement causes an unconditional jump to the statement prefixed by the named
7308 label in the enclosing function.
7309 <p><!--para 3 -->
7310 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
7311 following outline presents one possible approach to a problem based on these three assumptions:
7312 <ol>
7313 <li> The general initialization code accesses objects only visible to the current function.
7314 <li> The general initialization code is too large to warrant duplication.
7315 <li> The code to determine the next operation is at the head of the loop. (To allow it to be reached by
7316 continue statements, for example.)
7317 <pre>
7318 /* ... */
7319 goto first_time;
7320 for (;;) {
7321 // determine next operation
7322 /* ... */
7323 if (need to reinitialize) {
7324 // reinitialize-only code
7325 /* ... */
7326 first_time:
7327 // general initialization code
7328 /* ... */
7329 continue;
7330 }
7331 // handle other operations
7332 /* ... */
7333 }
7334 </pre>
7335 <!--page 150 -->
7336 </ol>
7337 <p><!--para 4 -->
7338 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
7339 modified types. A jump within the scope, however, is permitted.
7340 <pre>
7341 goto lab3; // invalid: going INTO scope of VLA.
7342 {
7343 double a[n];
7345 lab3:
7347 goto lab4; // valid: going WITHIN scope of VLA.
7349 lab4:
7351 }
7352 goto lab4; // invalid: going INTO scope of VLA.
7353 </pre>
7357 <p><b>Constraints</b>
7358 <p><!--para 1 -->
7359 A continue statement shall appear only in or as a loop body.
7360 <p><b>Semantics</b>
7361 <p><!--para 2 -->
7362 A continue statement causes a jump to the loop-continuation portion of the smallest
7363 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
7364 of the statements
7365 <pre>
7366 while (/* ... */) { do { for (/* ... */) {
7367 /* ... */ /* ... */ /* ... */
7368 continue; continue; continue;
7369 /* ... */ /* ... */ /* ... */
7370 contin: ; contin: ; contin: ;
7371 } } while (/* ... */); }
7372 </pre>
7373 unless the continue statement shown is in an enclosed iteration statement (in which
7374 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note138"><b>138)</b></a></sup>
7376 <p><b>Footnotes</b>
7377 <p><small><a name="note138" href="#note138">138)</a> Following the contin: label is a null statement.
7378 </small>
7381 <p><b>Constraints</b>
7382 <p><!--para 1 -->
7383 A break statement shall appear only in or as a switch body or loop body.
7384 <p><b>Semantics</b>
7385 <p><!--para 2 -->
7386 A break statement terminates execution of the smallest enclosing switch or iteration
7387 statement.
7391 <!--page 151 -->
7394 <p><b>Constraints</b>
7395 <p><!--para 1 -->
7396 A return statement with an expression shall not appear in a function whose return type
7397 is void. A return statement without an expression shall only appear in a function
7398 whose return type is void.
7399 <p><b>Semantics</b>
7400 <p><!--para 2 -->
7401 A return statement terminates execution of the current function and returns control to
7402 its caller. A function may have any number of return statements.
7403 <p><!--para 3 -->
7404 If a return statement with an expression is executed, the value of the expression is
7405 returned to the caller as the value of the function call expression. If the expression has a
7406 type different from the return type of the function in which it appears, the value is
7407 converted as if by assignment to an object having the return type of the function.<sup><a href="#note139"><b>139)</b></a></sup>
7408 <p><!--para 4 -->
7409 EXAMPLE In:
7410 <pre>
7411 struct s { double i; } f(void);
7412 union {
7413 struct {
7414 int f1;
7415 struct s f2;
7416 } u1;
7417 struct {
7418 struct s f3;
7419 int f4;
7420 } u2;
7421 } g;
7422 struct s f(void)
7423 {
7424 return g.u1.f2;
7425 }
7426 /* ... */
7427 g.u2.f3 = f();
7428 </pre>
7429 there is no undefined behavior, although there would be if the assignment were done directly (without using
7430 a function call to fetch the value).
7435 <!--page 152 -->
7437 <p><b>Footnotes</b>
7438 <p><small><a name="note139" href="#note139">139)</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
7439 apply to the case of function return. The representation of floating-point values may have wider range
7440 or precision and is determined by FLT_EVAL_METHOD. A cast may be used to remove this extra
7441 range and precision.
7442 </small>
7445 <p><b>Syntax</b>
7446 <p><!--para 1 -->
7447 <pre>
7448 translation-unit:
7449 external-declaration
7450 translation-unit external-declaration
7451 external-declaration:
7452 function-definition
7453 declaration
7454 </pre>
7455 <p><b>Constraints</b>
7456 <p><!--para 2 -->
7457 The storage-class specifiers auto and register shall not appear in the declaration
7458 specifiers in an external declaration.
7459 <p><!--para 3 -->
7460 There shall be no more than one external definition for each identifier declared with
7461 internal linkage in a translation unit. Moreover, if an identifier declared with internal
7462 linkage is used in an expression (other than as a part of the operand of a sizeof
7463 operator whose result is an integer constant), there shall be exactly one external definition
7464 for the identifier in the translation unit.
7465 <p><b>Semantics</b>
7466 <p><!--para 4 -->
7467 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,
7468 which consists of a sequence of external declarations. These are described as ''external''
7469 because they appear outside any function (and hence have file scope). As discussed in
7470 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
7471 by the identifier is a definition.
7472 <p><!--para 5 -->
7473 An external definition is an external declaration that is also a definition of a function
7474 (other than an inline definition) or an object. If an identifier declared with external
7475 linkage is used in an expression (other than as part of the operand of a sizeof operator
7476 whose result is an integer constant), somewhere in the entire program there shall be
7477 exactly one external definition for the identifier; otherwise, there shall be no more than
7483 <!--page 153 -->
7485 <p><b>Footnotes</b>
7486 <p><small><a name="note140" href="#note140">140)</a> Thus, if an identifier declared with external linkage is not used in an expression, there need be no
7487 external definition for it.
7488 </small>
7491 <p><b>Syntax</b>
7492 <p><!--para 1 -->
7493 <pre>
7494 function-definition:
7495 declaration-specifiers declarator declaration-list<sub>opt</sub> compound-statement
7496 declaration-list:
7497 declaration
7498 declaration-list declaration
7499 </pre>
7500 <p><b>Constraints</b>
7501 <p><!--para 2 -->
7502 The identifier declared in a function definition (which is the name of the function) shall
7503 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note141"><b>141)</b></a></sup>
7504 <p><!--para 3 -->
7505 The return type of a function shall be void or an object type other than array type.
7506 <p><!--para 4 -->
7507 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
7508 static.
7509 <p><!--para 5 -->
7510 If the declarator includes a parameter type list, the declaration of each parameter shall
7511 include an identifier, except for the special case of a parameter list consisting of a single
7512 parameter of type void, in which case there shall not be an identifier. No declaration list
7513 shall follow.
7514 <p><!--para 6 -->
7515 If the declarator includes an identifier list, each declaration in the declaration list shall
7516 have at least one declarator, those declarators shall declare only identifiers from the
7517 identifier list, and every identifier in the identifier list shall be declared. An identifier
7518 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
7519 declaration list shall contain no storage-class specifier other than register and no
7520 initializations.
7525 <!--page 154 -->
7526 <p><b>Semantics</b>
7527 <p><!--para 7 -->
7528 The declarator in a function definition specifies the name of the function being defined
7529 and the identifiers of its parameters. If the declarator includes a parameter type list, the
7530 list also specifies the types of all the parameters; such a declarator also serves as a
7531 function prototype for later calls to the same function in the same translation unit. If the
7532 declarator includes an identifier list,<sup><a href="#note142"><b>142)</b></a></sup> the types of the parameters shall be declared in a
7533 following declaration list. In either case, the type of each parameter is adjusted as
7534 described in <a href="#6.7.5.3">6.7.5.3</a> for a parameter type list; the resulting type shall be an object type.
7535 <p><!--para 8 -->
7536 If a function that accepts a variable number of arguments is defined without a parameter
7537 type list that ends with the ellipsis notation, the behavior is undefined.
7538 <p><!--para 9 -->
7539 Each parameter has automatic storage duration. Its identifier is an lvalue, which is in
7540 effect declared at the head of the compound statement that constitutes the function body
7541 (and therefore cannot be redeclared in the function body except in an enclosed block).
7542 The layout of the storage for parameters is unspecified.
7543 <p><!--para 10 -->
7544 On entry to the function, the size expressions of each variably modified parameter are
7545 evaluated and the value of each argument expression is converted to the type of the
7546 corresponding parameter as if by assignment. (Array expressions and function
7547 designators as arguments were converted to pointers before the call.)
7548 <p><!--para 11 -->
7549 After all parameters have been assigned, the compound statement that constitutes the
7550 body of the function definition is executed.
7551 <p><!--para 12 -->
7552 If the } that terminates a function is reached, and the value of the function call is used by
7553 the caller, the behavior is undefined.
7554 <p><!--para 13 -->
7555 EXAMPLE 1 In the following:
7556 <pre>
7557 extern int max(int a, int b)
7558 {
7559 return a > b ? a : b;
7560 }
7561 </pre>
7562 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
7563 function declarator; and
7564 <pre>
7565 { return a > b ? a : b; }
7566 </pre>
7567 is the function body. The following similar definition uses the identifier-list form for the parameter
7568 declarations:
7573 <!--page 155 -->
7574 <pre>
7575 extern int max(a, b)
7576 int a, b;
7577 {
7578 return a > b ? a : b;
7579 }
7580 </pre>
7581 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
7582 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
7583 to the function, whereas the second form does not.
7585 <p><!--para 14 -->
7586 EXAMPLE 2 To pass one function to another, one might say
7587 <pre>
7588 int f(void);
7589 /* ... */
7590 g(f);
7591 </pre>
7592 Then the definition of g might read
7593 <pre>
7594 void g(int (*funcp)(void))
7595 {
7596 /* ... */
7597 (*funcp)(); /* or funcp(); ... */
7598 }
7599 </pre>
7600 or, equivalently,
7601 <pre>
7602 void g(int func(void))
7603 {
7604 /* ... */
7605 func(); /* or (*func)(); ... */
7606 }
7607 </pre>
7610 <p><b>Footnotes</b>
7611 <p><small><a name="note141" href="#note141">141)</a> The intent is that the type category in a function definition cannot be inherited from a typedef:
7613 <pre>
7614 typedef int F(void); // type F is ''function with no parameters
7615 // returning int''
7616 F f, g; // f and g both have type compatible with F
7617 F f { /* ... */ } // WRONG: syntax/constraint error
7618 F g() { /* ... */ } // WRONG: declares that g returns a function
7619 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
7620 int g() { /* ... */ } // RIGHT: g has type compatible with F
7621 F *e(void) { /* ... */ } // e returns a pointer to a function
7622 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
7623 int (*fp)(void); // fp points to a function that has type F
7624 F *Fp; // Fp points to a function that has type F
7625 </pre>
7626 </small>
7627 <p><small><a name="note142" href="#note142">142)</a> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
7628 </small>
7631 <p><b>Semantics</b>
7632 <p><!--para 1 -->
7633 If the declaration of an identifier for an object has file scope and an initializer, the
7634 declaration is an external definition for the identifier.
7635 <p><!--para 2 -->
7636 A declaration of an identifier for an object that has file scope without an initializer, and
7637 without a storage-class specifier or with the storage-class specifier static, constitutes a
7638 tentative definition. If a translation unit contains one or more tentative definitions for an
7639 identifier, and the translation unit contains no external definition for that identifier, then
7640 the behavior is exactly as if the translation unit contains a file scope declaration of that
7641 identifier, with the composite type as of the end of the translation unit, with an initializer
7642 equal to 0.
7643 <p><!--para 3 -->
7644 If the declaration of an identifier for an object is a tentative definition and has internal
7645 linkage, the declared type shall not be an incomplete type.
7646 <!--page 156 -->
7647 <p><!--para 4 -->
7648 EXAMPLE 1
7649 <pre>
7650 int i1 = 1; // definition, external linkage
7651 static int i2 = 2; // definition, internal linkage
7652 extern int i3 = 3; // definition, external linkage
7653 int i4; // tentative definition, external linkage
7654 static int i5; // tentative definition, internal linkage
7655 int i1; // valid tentative definition, refers to previous
7657 int i3; // valid tentative definition, refers to previous
7658 int i4; // valid tentative definition, refers to previous
7660 extern int i1; // refers to previous, whose linkage is external
7661 extern int i2; // refers to previous, whose linkage is internal
7662 extern int i3; // refers to previous, whose linkage is external
7663 extern int i4; // refers to previous, whose linkage is external
7664 extern int i5; // refers to previous, whose linkage is internal
7665 </pre>
7667 <p><!--para 5 -->
7668 EXAMPLE 2 If at the end of the translation unit containing
7669 <pre>
7670 int i[];
7671 </pre>
7672 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
7673 zero on program startup.
7674 <!--page 157 -->
7677 <p><b>Syntax</b>
7678 <p><!--para 1 -->
7679 <!--page 158 -->
7680 <pre>
7681 preprocessing-file:
7682 group<sub>opt</sub>
7683 group:
7684 group-part
7685 group group-part
7686 group-part:
7687 if-section
7688 control-line
7689 text-line
7690 # non-directive
7691 if-section:
7692 if-group elif-groups<sub>opt</sub> else-group<sub>opt</sub> endif-line
7693 if-group:
7694 # if constant-expression new-line group<sub>opt</sub>
7695 # ifdef identifier new-line group<sub>opt</sub>
7696 # ifndef identifier new-line group<sub>opt</sub>
7697 elif-groups:
7698 elif-group
7699 elif-groups elif-group
7700 elif-group:
7701 # elif constant-expression new-line group<sub>opt</sub>
7702 else-group:
7703 # else new-line group<sub>opt</sub>
7704 endif-line:
7705 # endif new-line
7706 control-line:
7707 # include pp-tokens new-line
7708 # define identifier replacement-list new-line
7709 # define identifier lparen identifier-list<sub>opt</sub> )
7710 replacement-list new-line
7711 # define identifier lparen ... ) replacement-list new-line
7712 # define identifier lparen identifier-list , ... )
7713 replacement-list new-line
7714 # undef identifier new-line
7715 # line pp-tokens new-line
7716 # error pp-tokens<sub>opt</sub> new-line
7717 # pragma pp-tokens<sub>opt</sub> new-line
7718 # new-line
7719 text-line:
7720 pp-tokens<sub>opt</sub> new-line
7721 non-directive:
7722 pp-tokens new-line
7723 lparen:
7724 a ( character not immediately preceded by white-space
7725 replacement-list:
7726 pp-tokens<sub>opt</sub>
7727 pp-tokens:
7728 preprocessing-token
7729 pp-tokens preprocessing-token
7730 new-line:
7731 the new-line character
7732 </pre>
7733 <p><b>Description</b>
7734 <p><!--para 2 -->
7735 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
7736 following constraints: The first token in the sequence is a # preprocessing token that (at
7737 the start of translation phase 4) is either the first character in the source file (optionally
7738 after white space containing no new-line characters) or that follows white space
7739 containing at least one new-line character. The last token in the sequence is the first new-
7740 line character that follows the first token in the sequence.<sup><a href="#note143"><b>143)</b></a></sup> A new-line character ends
7741 the preprocessing directive even if it occurs within what would otherwise be an
7743 <!--page 159 -->
7744 invocation of a function-like macro.
7745 <p><!--para 3 -->
7746 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
7747 with any of the directive names appearing in the syntax.
7748 <p><!--para 4 -->
7749 When in a group that is skipped (<a href="#6.10.1">6.10.1</a>), the directive syntax is relaxed to allow any
7750 sequence of preprocessing tokens to occur between the directive name and the following
7751 new-line character.
7752 <p><b>Constraints</b>
7753 <p><!--para 5 -->
7754 The only white-space characters that shall appear between preprocessing tokens within a
7755 preprocessing directive (from just after the introducing # preprocessing token through
7756 just before the terminating new-line character) are space and horizontal-tab (including
7757 spaces that have replaced comments or possibly other white-space characters in
7758 translation phase 3).
7759 <p><b>Semantics</b>
7760 <p><!--para 6 -->
7761 The implementation can process and skip sections of source files conditionally, include
7762 other source files, and replace macros. These capabilities are called preprocessing,
7763 because conceptually they occur before translation of the resulting translation unit.
7764 <p><!--para 7 -->
7765 The preprocessing tokens within a preprocessing directive are not subject to macro
7766 expansion unless otherwise stated.
7767 <p><!--para 8 -->
7768 EXAMPLE In:
7769 <pre>
7770 #define EMPTY
7771 EMPTY # include <file.h>
7772 </pre>
7773 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
7774 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
7775 replaced.
7778 <p><b>Footnotes</b>
7779 <p><small><a name="note143" href="#note143">143)</a> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
7780 significance, as all white space is equivalent except in certain situations during preprocessing (see the
7781 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
7782 </small>
7785 <p><b>Constraints</b>
7786 <p><!--para 1 -->
7787 The expression that controls conditional inclusion shall be an integer constant expression
7788 except that: it shall not contain a cast; identifiers (including those lexically identical to
7789 keywords) are interpreted as described below;<sup><a href="#note144"><b>144)</b></a></sup> and it may contain unary operator
7790 expressions of the form
7795 <!--page 160 -->
7796 <pre>
7797 defined identifier
7798 </pre>
7799 or
7800 <pre>
7801 defined ( identifier )
7802 </pre>
7803 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
7804 predefined or if it has been the subject of a #define preprocessing directive without an
7805 intervening #undef directive with the same subject identifier), 0 if it is not.
7806 <p><!--para 2 -->
7807 Each preprocessing token that remains (in the list of preprocessing tokens that will
7808 become the controlling expression) after all macro replacements have occurred shall be in
7810 <p><b>Semantics</b>
7811 <p><!--para 3 -->
7812 Preprocessing directives of the forms
7813 <pre>
7814 # if constant-expression new-line group<sub>opt</sub>
7815 # elif constant-expression new-line group<sub>opt</sub>
7816 </pre>
7817 check whether the controlling constant expression evaluates to nonzero.
7818 <p><!--para 4 -->
7819 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
7820 the controlling constant expression are replaced (except for those macro names modified
7821 by the defined unary operator), just as in normal text. If the token defined is
7822 generated as a result of this replacement process or use of the defined unary operator
7823 does not match one of the two specified forms prior to macro replacement, the behavior is
7824 undefined. After all replacements due to macro expansion and the defined unary
7825 operator have been performed, all remaining identifiers (including those lexically
7826 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
7827 token is converted into a token. The resulting tokens compose the controlling constant
7828 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
7829 token conversion and evaluation, all signed integer types and all unsigned integer types
7830 act as if they have the same representation as, respectively, the types intmax_t and
7831 uintmax_t defined in the header <a href="#7.18"><stdint.h></a>.<sup><a href="#note145"><b>145)</b></a></sup> This includes interpreting
7832 character constants, which may involve converting escape sequences into execution
7833 character set members. Whether the numeric value for these character constants matches
7834 the value obtained when an identical character constant occurs in an expression (other
7835 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note146"><b>146)</b></a></sup> Also, whether a
7836 single-character character constant may have a negative value is implementation-defined.
7837 <p><!--para 5 -->
7838 Preprocessing directives of the forms
7842 <!--page 161 -->
7843 <pre>
7844 # ifdef identifier new-line group<sub>opt</sub>
7845 # ifndef identifier new-line group<sub>opt</sub>
7846 </pre>
7847 check whether the identifier is or is not currently defined as a macro name. Their
7848 conditions are equivalent to #if defined identifier and #if !defined identifier
7849 respectively.
7850 <p><!--para 6 -->
7851 Each directive's condition is checked in order. If it evaluates to false (zero), the group
7852 that it controls is skipped: directives are processed only through the name that determines
7853 the directive in order to keep track of the level of nested conditionals; the rest of the
7854 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
7855 group. Only the first group whose control condition evaluates to true (nonzero) is
7856 processed. If none of the conditions evaluates to true, and there is a #else directive, the
7857 group controlled by the #else is processed; lacking a #else directive, all the groups
7859 <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
7862 <p><b>Footnotes</b>
7863 <p><small><a name="note144" href="#note144">144)</a> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
7864 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
7865 </small>
7866 <p><small><a name="note145" href="#note145">145)</a> Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant
7867 0x8000 is signed and positive within a #if expression even though it would be unsigned in
7868 translation phase 7.
7869 </small>
7870 <p><small><a name="note146" href="#note146">146)</a> Thus, the constant expression in the following #if directive and if statement is not guaranteed to
7871 evaluate to the same value in these two contexts.
7872 <pre>
7873 #if 'z' - 'a' == 25
7874 if ('z' - 'a' == 25)
7875 </pre>
7877 </small>
7878 <p><small><a name="note147" href="#note147">147)</a> As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
7879 before the terminating new-line character. However, comments may appear anywhere in a source file,
7880 including within a preprocessing directive.
7881 </small>
7884 <p><b>Constraints</b>
7885 <p><!--para 1 -->
7886 A #include directive shall identify a header or source file that can be processed by the
7887 implementation.
7888 <p><b>Semantics</b>
7889 <p><!--para 2 -->
7890 A preprocessing directive of the form
7891 <pre>
7892 # include <h-char-sequence> new-line
7893 </pre>
7894 searches a sequence of implementation-defined places for a header identified uniquely by
7895 the specified sequence between the < and > delimiters, and causes the replacement of that
7896 directive by the entire contents of the header. How the places are specified or the header
7897 identified is implementation-defined.
7898 <p><!--para 3 -->
7899 A preprocessing directive of the form
7903 <!--page 162 -->
7904 <pre>
7906 </pre>
7907 causes the replacement of that directive by the entire contents of the source file identified
7908 by the specified sequence between the " delimiters. The named source file is searched
7909 for in an implementation-defined manner. If this search is not supported, or if the search
7910 fails, the directive is reprocessed as if it read
7911 <pre>
7913 </pre>
7914 with the identical contained sequence (including > characters, if any) from the original
7915 directive.
7917 A preprocessing directive of the form
7918 <pre>
7919 # include pp-tokens new-line
7920 </pre>
7921 (that does not match one of the two previous forms) is permitted. The preprocessing
7922 tokens after include in the directive are processed just as in normal text. (Each
7923 identifier currently defined as a macro name is replaced by its replacement list of
7924 preprocessing tokens.) The directive resulting after all replacements shall match one of
7925 the two previous forms.<sup><a href="#note148"><b>148)</b></a></sup> The method by which a sequence of preprocessing tokens
7926 between a < and a > preprocessing token pair or a pair of " characters is combined into a
7927 single header name preprocessing token is implementation-defined.
7928 <p><!--para 5 -->
7929 The implementation shall provide unique mappings for sequences consisting of one or
7930 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
7931 first character shall not be a digit. The implementation may ignore distinctions of
7932 alphabetical case and restrict the mapping to eight significant characters before the
7933 period.
7934 <p><!--para 6 -->
7935 A #include preprocessing directive may appear in a source file that has been read
7936 because of a #include directive in another file, up to an implementation-defined
7938 <p><!--para 7 -->
7939 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
7940 <pre>
7943 </pre>
7945 <p><!--para 8 -->
7946 EXAMPLE 2 This illustrates macro-replaced #include directives:
7951 <!--page 163 -->
7952 <pre>
7953 #if VERSION == 1
7955 #elif VERSION == 2
7957 #else
7959 #endif
7960 #include INCFILE
7961 </pre>
7965 <p><b>Footnotes</b>
7966 <p><small><a name="note148" href="#note148">148)</a> Note that adjacent string literals are not concatenated into a single string literal (see the translation
7967 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.
7968 </small>
7971 <p><b>Constraints</b>
7972 <p><!--para 1 -->
7973 Two replacement lists are identical if and only if the preprocessing tokens in both have
7974 the same number, ordering, spelling, and white-space separation, where all white-space
7975 separations are considered identical.
7976 <p><!--para 2 -->
7977 An identifier currently defined as an object-like macro shall not be redefined by another
7978 #define preprocessing directive unless the second definition is an object-like macro
7979 definition and the two replacement lists are identical. Likewise, an identifier currently
7980 defined as a function-like macro shall not be redefined by another #define
7981 preprocessing directive unless the second definition is a function-like macro definition
7982 that has the same number and spelling of parameters, and the two replacement lists are
7983 identical.
7984 <p><!--para 3 -->
7985 There shall be white-space between the identifier and the replacement list in the definition
7986 of an object-like macro.
7987 <p><!--para 4 -->
7988 If the identifier-list in the macro definition does not end with an ellipsis, the number of
7989 arguments (including those arguments consisting of no preprocessing tokens) in an
7990 invocation of a function-like macro shall equal the number of parameters in the macro
7991 definition. Otherwise, there shall be more arguments in the invocation than there are
7992 parameters in the macro definition (excluding the ...). There shall exist a )
7993 preprocessing token that terminates the invocation.
7994 <p><!--para 5 -->
7995 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
7996 macro that uses the ellipsis notation in the parameters.
7997 <p><!--para 6 -->
7998 A parameter identifier in a function-like macro shall be uniquely declared within its
7999 scope.
8000 <p><b>Semantics</b>
8001 <p><!--para 7 -->
8002 The identifier immediately following the define is called the macro name. There is one
8003 name space for macro names. Any white-space characters preceding or following the
8004 replacement list of preprocessing tokens are not considered part of the replacement list
8005 for either form of macro.
8006 <!--page 164 -->
8007 <p><!--para 8 -->
8008 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
8009 a preprocessing directive could begin, the identifier is not subject to macro replacement.
8010 <p><!--para 9 -->
8011 A preprocessing directive of the form
8012 <pre>
8013 # define identifier replacement-list new-line
8014 </pre>
8015 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note149"><b>149)</b></a></sup>
8016 to be replaced by the replacement list of preprocessing tokens that constitute the
8017 remainder of the directive. The replacement list is then rescanned for more macro names
8018 as specified below.
8019 <p><!--para 10 -->
8020 A preprocessing directive of the form
8021 <pre>
8022 # define identifier lparen identifier-list<sub>opt</sub> ) replacement-list new-line
8023 # define identifier lparen ... ) replacement-list new-line
8024 # define identifier lparen identifier-list , ... ) replacement-list new-line
8025 </pre>
8026 defines a function-like macro with parameters, whose use is similar syntactically to a
8027 function call. The parameters are specified by the optional list of identifiers, whose scope
8028 extends from their declaration in the identifier list until the new-line character that
8029 terminates the #define preprocessing directive. Each subsequent instance of the
8030 function-like macro name followed by a ( as the next preprocessing token introduces the
8031 sequence of preprocessing tokens that is replaced by the replacement list in the definition
8032 (an invocation of the macro). The replaced sequence of preprocessing tokens is
8033 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
8034 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
8035 tokens making up an invocation of a function-like macro, new-line is considered a normal
8036 white-space character.
8037 <p><!--para 11 -->
8038 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
8039 forms the list of arguments for the function-like macro. The individual arguments within
8040 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
8041 between matching inner parentheses do not separate arguments. If there are sequences of
8042 preprocessing tokens within the list of arguments that would otherwise act as
8043 preprocessing directives,<sup><a href="#note150"><b>150)</b></a></sup> the behavior is undefined.
8044 <p><!--para 12 -->
8045 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
8046 including any separating comma preprocessing tokens, are merged to form a single item:
8047 the variable arguments. The number of arguments so combined is such that, following
8050 <!--page 165 -->
8051 merger, the number of arguments is one more than the number of parameters in the macro
8052 definition (excluding the ...).
8054 <p><b>Footnotes</b>
8055 <p><small><a name="note149" href="#note149">149)</a> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
8056 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
8057 are never scanned for macro names or parameters.
8058 </small>
8059 <p><small><a name="note150" href="#note150">150)</a> Despite the name, a non-directive is a preprocessing directive.
8060 </small>
8063 <p><!--para 1 -->
8064 After the arguments for the invocation of a function-like macro have been identified,
8065 argument substitution takes place. A parameter in the replacement list, unless preceded
8066 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
8067 replaced by the corresponding argument after all macros contained therein have been
8068 expanded. Before being substituted, each argument's preprocessing tokens are
8069 completely macro replaced as if they formed the rest of the preprocessing file; no other
8070 preprocessing tokens are available.
8071 <p><!--para 2 -->
8072 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
8073 were a parameter, and the variable arguments shall form the preprocessing tokens used to
8074 replace it.
8077 <p><b>Constraints</b>
8078 <p><!--para 1 -->
8079 Each # preprocessing token in the replacement list for a function-like macro shall be
8080 followed by a parameter as the next preprocessing token in the replacement list.
8081 <p><b>Semantics</b>
8082 <p><!--para 2 -->
8083 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
8084 token, both are replaced by a single character string literal preprocessing token that
8085 contains the spelling of the preprocessing token sequence for the corresponding
8086 argument. Each occurrence of white space between the argument's preprocessing tokens
8087 becomes a single space character in the character string literal. White space before the
8088 first preprocessing token and after the last preprocessing token composing the argument
8089 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
8090 is retained in the character string literal, except for special handling for producing the
8091 spelling of string literals and character constants: a \ character is inserted before each "
8092 and \ character of a character constant or string literal (including the delimiting "
8093 characters), except that it is implementation-defined whether a \ character is inserted
8094 before the \ character beginning a universal character name. If the replacement that
8095 results is not a valid character string literal, the behavior is undefined. The character
8097 ## operators is unspecified.
8098 <!--page 166 -->
8101 <p><b>Constraints</b>
8102 <p><!--para 1 -->
8103 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
8104 list for either form of macro definition.
8105 <p><b>Semantics</b>
8106 <p><!--para 2 -->
8107 If, in the replacement list of a function-like macro, a parameter is immediately preceded
8108 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
8109 argument's preprocessing token sequence; however, if an argument consists of no
8110 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
8112 <p><!--para 3 -->
8113 For both object-like and function-like macro invocations, before the replacement list is
8114 reexamined for more macro names to replace, each instance of a ## preprocessing token
8115 in the replacement list (not from an argument) is deleted and the preceding preprocessing
8116 token is concatenated with the following preprocessing token. Placemarker
8117 preprocessing tokens are handled specially: concatenation of two placemarkers results in
8118 a single placemarker preprocessing token, and concatenation of a placemarker with a
8119 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
8120 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
8121 token is available for further macro replacement. The order of evaluation of ## operators
8122 is unspecified.
8123 <p><!--para 4 -->
8124 EXAMPLE In the following fragment:
8125 <pre>
8126 #define hash_hash # ## #
8127 #define mkstr(a) # a
8128 #define in_between(a) mkstr(a)
8129 #define join(c, d) in_between(c hash_hash d)
8130 char p[] = join(x, y); // equivalent to
8132 </pre>
8133 The expansion produces, at various stages:
8134 <pre>
8135 join(x, y)
8136 in_between(x hash_hash y)
8137 in_between(x ## y)
8138 mkstr(x ## y)
8140 </pre>
8141 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
8142 this new token is not the ## operator.
8145 <!--page 167 -->
8147 <p><b>Footnotes</b>
8148 <p><small><a name="note151" href="#note151">151)</a> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
8149 exist only within translation phase 4.
8150 </small>
8153 <p><!--para 1 -->
8154 After all parameters in the replacement list have been substituted and # and ##
8155 processing has taken place, all placemarker preprocessing tokens are removed. Then, the
8156 resulting preprocessing token sequence is rescanned, along with all subsequent
8157 preprocessing tokens of the source file, for more macro names to replace.
8158 <p><!--para 2 -->
8159 If the name of the macro being replaced is found during this scan of the replacement list
8160 (not including the rest of the source file's preprocessing tokens), it is not replaced.
8161 Furthermore, if any nested replacements encounter the name of the macro being replaced,
8162 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
8163 available for further replacement even if they are later (re)examined in contexts in which
8164 that macro name preprocessing token would otherwise have been replaced.
8165 <p><!--para 3 -->
8166 The resulting completely macro-replaced preprocessing token sequence is not processed
8167 as a preprocessing directive even if it resembles one, but all pragma unary operator
8171 <p><!--para 1 -->
8172 A macro definition lasts (independent of block structure) until a corresponding #undef
8173 directive is encountered or (if none is encountered) until the end of the preprocessing
8174 translation unit. Macro definitions have no significance after translation phase 4.
8175 <p><!--para 2 -->
8176 A preprocessing directive of the form
8177 <pre>
8178 # undef identifier new-line
8179 </pre>
8180 causes the specified identifier no longer to be defined as a macro name. It is ignored if
8181 the specified identifier is not currently defined as a macro name.
8182 <p><!--para 3 -->
8183 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
8184 <pre>
8185 #define TABSIZE 100
8186 int table[TABSIZE];
8187 </pre>
8189 <p><!--para 4 -->
8190 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
8191 It has the advantages of working for any compatible types of the arguments and of generating in-line code
8192 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
8193 arguments a second time (including side effects) and generating more code than a function if invoked
8194 several times. It also cannot have its address taken, as it has none.
8195 <pre>
8196 #define max(a, b) ((a) > (b) ? (a) : (b))
8197 </pre>
8198 The parentheses ensure that the arguments and the resulting expression are bound properly.
8199 <!--page 168 -->
8200 <p><!--para 5 -->
8201 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
8202 <pre>
8203 #define x 3
8204 #define f(a) f(x * (a))
8205 #undef x
8206 #define x 2
8207 #define g f
8208 #define z z[0]
8209 #define h g(~
8210 #define m(a) a(w)
8211 #define w 0,1
8212 #define t(a) a
8213 #define p() int
8214 #define q(x) x
8215 #define r(x,y) x ## y
8216 #define str(x) # x
8217 f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
8218 g(x+(3,4)-w) | h 5) & m
8219 (f)^m(m);
8220 p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
8221 char c[2][6] = { str(hello), str() };
8222 </pre>
8223 results in
8224 <pre>
8225 f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
8226 f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
8227 int i[] = { 1, 23, 4, 5, };
8229 </pre>
8231 <p><!--para 6 -->
8232 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
8233 sequence
8234 <pre>
8235 #define str(s) # s
8236 #define xstr(s) str(s)
8238 x ## s, x ## t)
8239 #define INCFILE(n) vers ## n
8240 #define glue(a, b) a ## b
8241 #define xglue(a, b) glue(a, b)
8244 debug(1, 2);
8246 == 0) str(: @\n), s);
8247 #include xstr(INCFILE(2).h)
8248 glue(HIGH, LOW);
8249 xglue(HIGH, LOW)
8250 </pre>
8251 results in
8252 <!--page 169 -->
8253 <pre>
8255 fputs(
8257 s);
8261 </pre>
8262 or, after concatenation of the character string literals,
8263 <pre>
8265 fputs(
8267 s);
8271 </pre>
8272 Space around the # and ## tokens in the macro definition is optional.
8274 <p><!--para 7 -->
8275 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
8276 <pre>
8277 #define t(x,y,z) x ## y ## z
8278 int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
8279 t(10,,), t(,11,), t(,,12), t(,,) };
8280 </pre>
8281 results in
8282 <pre>
8283 int j[] = { 123, 45, 67, 89,
8284 10, 11, 12, };
8285 </pre>
8287 <p><!--para 8 -->
8288 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
8289 <pre>
8290 #define OBJ_LIKE (1-1)
8291 #define OBJ_LIKE /* white space */ (1-1) /* other */
8292 #define FUNC_LIKE(a) ( a )
8293 #define FUNC_LIKE( a )( /* note the white space */ \
8294 a /* other stuff on this line
8295 */ )
8296 </pre>
8297 But the following redefinitions are invalid:
8298 <pre>
8299 #define OBJ_LIKE (0) // different token sequence
8300 #define OBJ_LIKE (1 - 1) // different white space
8301 #define FUNC_LIKE(b) ( a ) // different parameter usage
8302 #define FUNC_LIKE(b) ( b ) // different parameter spelling
8303 </pre>
8305 <p><!--para 9 -->
8306 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
8307 <!--page 170 -->
8308 <pre>
8309 #define debug(...) fprintf(stderr, __VA_ARGS__)
8310 #define showlist(...) puts(#__VA_ARGS__)
8311 #define report(test, ...) ((test)?puts(#test):\
8312 printf(__VA_ARGS__))
8315 showlist(The first, second, and third items.);
8317 </pre>
8318 results in
8319 <pre>
8325 </pre>
8329 <p><b>Constraints</b>
8330 <p><!--para 1 -->
8331 The string literal of a #line directive, if present, shall be a character string literal.
8332 <p><b>Semantics</b>
8333 <p><!--para 2 -->
8334 The line number of the current source line is one greater than the number of new-line
8335 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
8336 file to the current token.
8337 <p><!--para 3 -->
8338 A preprocessing directive of the form
8339 <pre>
8340 # line digit-sequence new-line
8341 </pre>
8342 causes the implementation to behave as if the following sequence of source lines begins
8343 with a source line that has a line number as specified by the digit sequence (interpreted as
8344 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
8345 2147483647.
8346 <p><!--para 4 -->
8347 A preprocessing directive of the form
8348 <pre>
8350 </pre>
8351 sets the presumed line number similarly and changes the presumed name of the source
8352 file to be the contents of the character string literal.
8353 <p><!--para 5 -->
8354 A preprocessing directive of the form
8355 <pre>
8356 # line pp-tokens new-line
8357 </pre>
8358 (that does not match one of the two previous forms) is permitted. The preprocessing
8359 tokens after line on the directive are processed just as in normal text (each identifier
8360 currently defined as a macro name is replaced by its replacement list of preprocessing
8361 tokens). The directive resulting after all replacements shall match one of the two
8362 previous forms and is then processed as appropriate.
8363 <!--page 171 -->
8366 <p><b>Semantics</b>
8367 <p><!--para 1 -->
8368 A preprocessing directive of the form
8369 <pre>
8370 # error pp-tokens<sub>opt</sub> new-line
8371 </pre>
8372 causes the implementation to produce a diagnostic message that includes the specified
8373 sequence of preprocessing tokens.
8376 <p><b>Semantics</b>
8377 <p><!--para 1 -->
8378 A preprocessing directive of the form
8379 <pre>
8380 # pragma pp-tokens<sub>opt</sub> new-line
8381 </pre>
8382 where the preprocessing token STDC does not immediately follow pragma in the
8383 directive (prior to any macro replacement)<sup><a href="#note152"><b>152)</b></a></sup> causes the implementation to behave in an
8384 implementation-defined manner. The behavior might cause translation to fail or cause the
8385 translator or the resulting program to behave in a non-conforming manner. Any such
8386 pragma that is not recognized by the implementation is ignored.
8387 <p><!--para 2 -->
8388 If the preprocessing token STDC does immediately follow pragma in the directive (prior
8389 to any macro replacement), then no macro replacement is performed on the directive, and
8390 the directive shall have one of the following forms<sup><a href="#note153"><b>153)</b></a></sup> whose meanings are described
8391 elsewhere:
8392 <pre>
8393 #pragma STDC FP_CONTRACT on-off-switch
8394 #pragma STDC FENV_ACCESS on-off-switch
8395 #pragma STDC CX_LIMITED_RANGE on-off-switch
8396 on-off-switch: one of
8397 ON OFF DEFAULT
8398 </pre>
8399 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
8405 <!--page 172 -->
8407 <p><b>Footnotes</b>
8408 <p><small><a name="note152" href="#note152">152)</a> An implementation is not required to perform macro replacement in pragmas, but it is permitted
8409 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
8410 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
8411 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
8412 but is not required to.
8413 </small>
8414 <p><small><a name="note153" href="#note153">153)</a> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
8415 </small>
8418 <p><b>Semantics</b>
8419 <p><!--para 1 -->
8420 A preprocessing directive of the form
8421 <pre>
8422 # new-line
8423 </pre>
8424 has no effect.
8427 <p><!--para 1 -->
8428 The following macro names<sup><a href="#note154"><b>154)</b></a></sup> shall be defined by the implementation:
8429 <dl>
8430 <dt> __DATE__ <dd>The date of translation of the preprocessing translation unit: a character
8432 months are the same as those generated by the asctime function, and the
8433 first character of dd is a space character if the value is less than 10. If the
8434 date of translation is not available, an implementation-defined valid date
8435 shall be supplied.
8436 <dt> __FILE__ <dd>The presumed name of the current source file (a character string literal).<sup><a href="#note155"><b>155)</b></a></sup>
8437 <dt> __LINE__ <dd>The presumed line number (within the current source file) of the current
8439 <dt> __STDC__ <dd>The integer constant 1, intended to indicate a conforming implementation.
8440 <dt> __STDC_HOSTED__ <dd>The integer constant 1 if the implementation is a hosted
8441 implementation or the integer constant 0 if it is not.
8442 <dt> __STDC_MB_MIGHT_NEQ_WC__ <dd>The integer constant 1, intended to indicate that, in
8443 the encoding for wchar_t, a member of the basic character set need not
8444 have a code value equal to its value when used as the lone character in an
8445 integer character constant.
8446 <dt> __STDC_VERSION__ <dd>The integer constant 199901L.<sup><a href="#note156"><b>156)</b></a></sup>
8447 <dt> __TIME__ <dd>The time of translation of the preprocessing translation unit: a character
8449 asctime function. If the time of translation is not available, an
8450 implementation-defined valid time shall be supplied.
8451 </dl>
8454 <!--page 173 -->
8455 <p><!--para 2 -->
8456 The following macro names are conditionally defined by the implementation:
8457 <dl>
8458 <dt> __STDC_IEC_559__ <dd>The integer constant 1, intended to indicate conformance to the
8460 <dt> __STDC_IEC_559_COMPLEX__ <dd>The integer constant 1, intended to indicate
8462 compatible complex arithmetic).
8463 <dt> __STDC_ISO_10646__ <dd>An integer constant of the form yyyymmL (for example,
8464 199712L). If this symbol is defined, then every character in the Unicode
8465 required set, when stored in an object of type wchar_t, has the same
8466 value as the short identifier of that character. The Unicode required set
8467 consists of all the characters that are defined by ISO/IEC 10646, along with
8468 all amendments and technical corrigenda, as of the specified year and
8469 month.
8470 </dl>
8471 <p><!--para 3 -->
8472 The values of the predefined macros (except for __FILE__ and __LINE__) remain
8473 constant throughout the translation unit.
8474 <p><!--para 4 -->
8475 None of these macro names, nor the identifier defined, shall be the subject of a
8476 #define or a #undef preprocessing directive. Any other predefined macro names
8477 shall begin with a leading underscore followed by an uppercase letter or a second
8478 underscore.
8479 <p><!--para 5 -->
8480 The implementation shall not predefine the macro __cplusplus, nor shall it define it
8481 in any standard header.
8482 <p><b> Forward references</b>: the asctime function (<a href="#7.23.3.1">7.23.3.1</a>), standard headers (<a href="#7.1.2">7.1.2</a>).
8484 <p><b>Footnotes</b>
8485 <p><small><a name="note154" href="#note154">154)</a> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
8486 </small>
8487 <p><small><a name="note155" href="#note155">155)</a> The presumed source file name and line number can be changed by the #line directive.
8488 </small>
8489 <p><small><a name="note156" href="#note156">156)</a> This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
8490 ISO/IEC 9899/AMD1:1995. The intention is that this will remain an integer constant of type long
8491 int that is increased with each revision of this International Standard.
8492 </small>
8495 <p><b>Semantics</b>
8496 <p><!--para 1 -->
8497 A unary operator expression of the form:
8498 <pre>
8499 _Pragma ( string-literal )
8500 </pre>
8501 is processed as follows: The string literal is destringized by deleting the L prefix, if
8502 present, deleting the leading and trailing double-quotes, replacing each escape sequence
8503 \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
8504 resulting sequence of characters is processed through translation phase 3 to produce
8505 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
8506 directive. The original four preprocessing tokens in the unary operator expression are
8507 removed.
8509 EXAMPLE A directive of the form:
8510 <pre>
8511 #pragma listing on "..\listing.dir"
8512 </pre>
8513 can also be expressed as:
8514 <!--page 174 -->
8515 <pre>
8517 </pre>
8518 The latter form is processed in the same way whether it appears literally as shown, or results from macro
8519 replacement, as in:
8520 <!--page 175 -->
8521 <pre>
8522 #define LISTING(x) PRAGMA(listing on #x)
8523 #define PRAGMA(x) _Pragma(#x)
8524 LISTING ( ..\listing.dir )
8525 </pre>
8531 Future standardization may include additional floating-point types, including those with
8532 greater range, precision, or both than long double.
8536 Declaring an identifier with internal linkage at file scope without the static storage-
8537 class specifier is an obsolescent feature.
8541 Restriction of the significance of an external name to fewer than 255 characters
8542 (considering each universal character name or extended source character as a single
8543 character) is an obsolescent feature that is a concession to existing implementations.
8547 Lowercase letters as escape sequences are reserved for future standardization. Other
8548 characters may be used in extensions.
8552 The placement of a storage-class specifier other than at the beginning of the declaration
8553 specifiers in a declaration is an obsolescent feature.
8557 The use of function declarators with empty parentheses (not prototype-format parameter
8558 type declarators) is an obsolescent feature.
8562 The use of function definitions with separate parameter identifier and declaration lists
8563 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
8567 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
8571 Macro names beginning with __STDC_ are reserved for future standardization.
8572 <!--page 176 -->
8581 A string is a contiguous sequence of characters terminated by and including the first null
8582 character. The term multibyte string is sometimes used instead to emphasize special
8583 processing given to multibyte characters contained in the string or to avoid confusion
8584 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
8585 character. The length of a string is the number of bytes preceding the null character and
8586 the value of a string is the sequence of the values of the contained characters, in order.
8588 The decimal-point character is the character used by functions that convert floating-point
8589 numbers to or from character sequences to denote the beginning of the fractional part of
8590 such character sequences.<sup><a href="#note157"><b>157)</b></a></sup> It is represented in the text and examples by a period, but
8591 may be changed by the setlocale function.
8593 A null wide character is a wide character with code value zero.
8595 A wide string is a contiguous sequence of wide characters terminated by and including
8596 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
8597 addressed) wide character. The length of a wide string is the number of wide characters
8598 preceding the null wide character and the value of a wide string is the sequence of code
8599 values of the contained wide characters, in order.
8601 A shift sequence is a contiguous sequence of bytes within a multibyte string that
8602 (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
8603 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
8605 <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>).
8610 <!--page 177 -->
8613 <p><small><a name="note157" href="#note157">157)</a> The functions that make use of the decimal-point character are the numeric conversion functions
8614 (<a href="#7.20.1">7.20.1</a>, <a href="#7.24.4.1">7.24.4.1</a>) and the formatted input/output functions (<a href="#7.19.6">7.19.6</a>, <a href="#7.24.2">7.24.2</a>).
8615 </small>
8616 <p><small><a name="note158" href="#note158">158)</a> For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus be large
8617 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
8618 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
8619 implementation's choice.
8620 </small>
8624 Each library function is declared, with a type that includes a prototype, in a header,<sup><a href="#note159"><b>159)</b></a></sup>
8625 whose contents are made available by the #include preprocessing directive. The
8626 header declares a set of related functions, plus any necessary types and additional macros
8627 needed to facilitate their use. Declarations of types described in this clause shall not
8628 include type qualifiers, unless explicitly stated otherwise.
8630 The standard headers are
8631 <pre>
8632 <a href="#7.2"><assert.h></a> <a href="#7.8"><inttypes.h></a> <a href="#7.14"><signal.h></a> <a href="#7.20"><stdlib.h></a>
8633 <a href="#7.3"><complex.h></a> <a href="#7.9"><iso646.h></a> <a href="#7.15"><stdarg.h></a> <a href="#7.21"><string.h></a>
8634 <a href="#7.4"><ctype.h></a> <a href="#7.10"><limits.h></a> <a href="#7.16"><stdbool.h></a> <a href="#7.22"><tgmath.h></a>
8635 <a href="#7.5"><errno.h></a> <a href="#7.11"><locale.h></a> <a href="#7.17"><stddef.h></a> <a href="#7.23"><time.h></a>
8636 <a href="#7.6"><fenv.h></a> <a href="#7.12"><math.h></a> <a href="#7.18"><stdint.h></a> <a href="#7.24"><wchar.h></a>
8637 <a href="#7.7"><float.h></a> <a href="#7.13"><setjmp.h></a> <a href="#7.19"><stdio.h></a> <a href="#7.25"><wctype.h></a>
8638 </pre>
8641 provided as part of the implementation, is placed in any of the standard places that are
8642 searched for included source files, the behavior is undefined.
8644 Standard headers may be included in any order; each may be included more than once in
8645 a given scope, with no effect different from being included only once, except that the
8646 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
8647 used, a header shall be included outside of any external declaration or definition, and it
8648 shall first be included before the first reference to any of the functions or objects it
8649 declares, or to any of the types or macros it defines. However, if an identifier is declared
8650 or defined in more than one header, the second and subsequent associated headers may be
8651 included after the initial reference to the identifier. The program shall not have any
8652 macros with names lexically identical to keywords currently defined prior to the
8653 inclusion.
8655 Any definition of an object-like macro described in this clause shall expand to code that is
8656 fully protected by parentheses where necessary, so that it groups in an arbitrary
8657 expression as if it were a single identifier.
8659 Any declaration of a library function shall have external linkage.
8667 <!--page 178 -->
8670 <p><small><a name="note159" href="#note159">159)</a> A header is not necessarily a source file, nor are the < and > delimited sequences in header names
8671 necessarily valid source file names.
8672 </small>
8676 Each header declares or defines all identifiers listed in its associated subclause, and
8677 optionally declares or defines identifiers listed in its associated future library directions
8678 subclause and identifiers which are always reserved either for any use or for use as file
8679 scope identifiers.
8680 <ul>
8681 <li> All identifiers that begin with an underscore and either an uppercase letter or another
8682 underscore are always reserved for any use.
8683 <li> All identifiers that begin with an underscore are always reserved for use as identifiers
8684 with file scope in both the ordinary and tag name spaces.
8685 <li> Each macro name in any of the following subclauses (including the future library
8686 directions) is reserved for use as specified if any of its associated headers is included;
8688 <li> All identifiers with external linkage in any of the following subclauses (including the
8689 future library directions) are always reserved for use as identifiers with external
8691 <li> Each identifier with file scope listed in any of the following subclauses (including the
8692 future library directions) is reserved for use as a macro name and as an identifier with
8693 file scope in the same name space if any of its associated headers is included.
8694 </ul>
8696 No other identifiers are reserved. If the program declares or defines an identifier in a
8697 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
8698 identifier as a macro name, the behavior is undefined.
8700 If the program removes (with #undef) any macro definition of an identifier in the first
8701 group listed above, the behavior is undefined.
8704 <p><small><a name="note160" href="#note160">160)</a> The list of reserved identifiers with external linkage includes errno, math_errhandling,
8705 setjmp, and va_end.
8706 </small>
8710 Each of the following statements applies unless explicitly stated otherwise in the detailed
8711 descriptions that follow: If an argument to a function has an invalid value (such as a value
8712 outside the domain of the function, or a pointer outside the address space of the program,
8713 or a null pointer, or a pointer to non-modifiable storage when the corresponding
8714 parameter is not const-qualified) or a type (after promotion) not expected by a function
8715 with variable number of arguments, the behavior is undefined. If a function argument is
8716 described as being an array, the pointer actually passed to the function shall have a value
8717 such that all address computations and accesses to objects (that would be valid if the
8718 pointer did point to the first element of such an array) are in fact valid. Any function
8719 declared in a header may be additionally implemented as a function-like macro defined in
8721 <!--page 179 -->
8722 the header, so if a library function is declared explicitly when its header is included, one
8723 of the techniques shown below can be used to ensure the declaration is not affected by
8724 such a macro. Any macro definition of a function can be suppressed locally by enclosing
8725 the name of the function in parentheses, because the name is then not followed by the left
8726 parenthesis that indicates expansion of a macro function name. For the same syntactic
8727 reason, it is permitted to take the address of a library function even if it is also defined as
8728 a macro.<sup><a href="#note161"><b>161)</b></a></sup> The use of #undef to remove any macro definition will also ensure that an
8729 actual function is referred to. Any invocation of a library function that is implemented as
8730 a macro shall expand to code that evaluates each of its arguments exactly once, fully
8731 protected by parentheses where necessary, so it is generally safe to use arbitrary
8732 expressions as arguments.<sup><a href="#note162"><b>162)</b></a></sup> Likewise, those function-like macros described in the
8733 following subclauses may be invoked in an expression anywhere a function with a
8734 compatible return type could be called.<sup><a href="#note163"><b>163)</b></a></sup> All object-like macros listed as expanding to
8735 integer constant expressions shall additionally be suitable for use in #if preprocessing
8736 directives.
8738 Provided that a library function can be declared without reference to any type defined in a
8739 header, it is also permissible to declare the function and use it without including its
8740 associated header.
8742 There is a sequence point immediately before a library function returns.
8744 The functions in the standard library are not guaranteed to be reentrant and may modify
8749 <!--page 180 -->
8751 EXAMPLE The function atoi may be used in any of several ways:
8752 <ul>
8753 <li> by use of its associated header (possibly generating a macro expansion)
8754 <pre>
8756 const char *str;
8757 /* ... */
8758 i = atoi(str);
8759 </pre>
8760 <li> by use of its associated header (assuredly generating a true function reference)
8761 <pre>
8763 #undef atoi
8764 const char *str;
8765 /* ... */
8766 i = atoi(str);
8767 </pre>
8768 or
8769 <pre>
8771 const char *str;
8772 /* ... */
8773 i = (atoi)(str);
8774 </pre>
8775 <li> by explicit declaration
8776 <!--page 181 -->
8777 <pre>
8778 extern int atoi(const char *);
8779 const char *str;
8780 /* ... */
8781 i = atoi(str);
8782 </pre>
8783 </ul>
8786 <p><small><a name="note161" href="#note161">161)</a> This means that an implementation shall provide an actual function for each library function, even if it
8787 also provides a macro for that function.
8788 </small>
8789 <p><small><a name="note162" href="#note162">162)</a> Such macros might not contain the sequence points that the corresponding function calls do.
8790 </small>
8791 <p><small><a name="note163" href="#note163">163)</a> Because external identifiers and some macro names beginning with an underscore are reserved,
8792 implementations may provide special semantics for such names. For example, the identifier
8793 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
8794 appropriate header could specify
8796 <pre>
8797 #define abs(x) _BUILTIN_abs(x)
8798 </pre>
8799 for a compiler whose code generator will accept it.
8800 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
8801 function may write
8803 <pre>
8804 #undef abs
8805 </pre>
8806 whether the implementation's header provides a macro implementation of abs or a built-in
8807 implementation. The prototype for the function, which precedes and is hidden by any macro
8808 definition, is thereby revealed also.
8809 </small>
8810 <p><small><a name="note164" href="#note164">164)</a> Thus, a signal handler cannot, in general, call standard library functions.
8811 </small>
8815 The header <a href="#7.2"><assert.h></a> defines the assert macro and refers to another macro,
8816 <pre>
8817 NDEBUG
8818 </pre>
8819 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
8820 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
8821 simply as
8822 <pre>
8823 #define assert(ignore) ((void)0)
8824 </pre>
8825 The assert macro is redefined according to the current state of NDEBUG each time that
8828 The assert macro shall be implemented as a macro, not as an actual function. If the
8829 macro definition is suppressed in order to access an actual function, the behavior is
8830 undefined.
8837 <pre>
8839 void assert(scalar expression);
8840 </pre>
8843 The assert macro puts diagnostic tests into programs; it expands to a void expression.
8844 When it is executed, if expression (which shall have a scalar type) is false (that is,
8845 compares equal to 0), the assert macro writes information about the particular call that
8846 failed (including the text of the argument, the name of the source file, the source line
8847 number, and the name of the enclosing function -- the latter are respectively the values of
8848 the preprocessing macros __FILE__ and __LINE__ and of the identifier
8849 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note165"><b>165)</b></a></sup> It
8850 then calls the abort function.
8853 The assert macro returns no value.
8859 <!--page 182 -->
8863 Assertion failed: expression, function abc, file xyz, line nnn.
8864 </small>
8870 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
8871 arithmetic.<sup><a href="#note166"><b>166)</b></a></sup> Each synopsis specifies a family of functions consisting of a principal
8872 function with one or more double complex parameters and a double complex or
8873 double return value; and other functions with the same name but with f and l suffixes
8874 which are corresponding functions with float and long double parameters and
8875 return values.
8877 The macro
8878 <pre>
8879 complex
8880 </pre>
8881 expands to _Complex; the macro
8882 <pre>
8883 _Complex_I
8884 </pre>
8885 expands to a constant expression of type const float _Complex, with the value of
8888 The macros
8889 <pre>
8890 imaginary
8891 </pre>
8892 and
8893 <pre>
8894 _Imaginary_I
8895 </pre>
8896 are defined if and only if the implementation supports imaginary types;<sup><a href="#note168"><b>168)</b></a></sup> if defined,
8897 they expand to _Imaginary and a constant expression of type const float
8898 _Imaginary with the value of the imaginary unit.
8900 The macro
8901 <pre>
8902 I
8903 </pre>
8904 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
8905 defined, I shall expand to _Complex_I.
8907 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
8908 redefine the macros complex, imaginary, and I.
8909 <p><b> Forward references</b>: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
8913 <!--page 183 -->
8916 <p><small><a name="note166" href="#note166">166)</a> See ''future library directions'' (<a href="#7.26.1">7.26.1</a>).
8917 </small>
8918 <p><small><a name="note167" href="#note167">167)</a> The imaginary unit is a number i such that i<sup>2</sup> = -1.
8919 </small>
8920 <p><small><a name="note168" href="#note168">168)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
8921 </small>
8925 Values are interpreted as radians, not degrees. An implementation may set errno but is
8926 not required to.
8930 Some of the functions below have branch cuts, across which the function is
8931 discontinuous. For implementations with a signed zero (including all IEC 60559
8932 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
8933 one side of a cut from another so the function is continuous (except for format
8934 limitations) as the cut is approached from either side. For example, for the square root
8935 function, which has a branch cut along the negative real axis, the top of the cut, with
8936 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
8937 imaginary part -0, maps to the negative imaginary axis.
8939 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
8940 sides of branch cuts. These implementations shall map a cut so the function is continuous
8941 as the cut is approached coming around the finite endpoint of the cut in a counter
8942 clockwise direction. (Branch cuts for the functions specified here have just one finite
8943 endpoint.) For example, for the square root function, coming counter clockwise around
8944 the finite endpoint of the cut along the negative real axis approaches the cut from above,
8945 so the cut maps to the positive imaginary axis.
8950 <pre>
8952 #pragma STDC CX_LIMITED_RANGE on-off-switch
8953 </pre>
8956 The usual mathematical formulas for complex multiply, divide, and absolute value are
8957 problematic because of their treatment of infinities and because of undue overflow and
8958 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
8959 implementation that (where the state is ''on'') the usual mathematical formulas are
8960 acceptable.<sup><a href="#note169"><b>169)</b></a></sup> The pragma can occur either outside external declarations or preceding all
8961 explicit declarations and statements inside a compound statement. When outside external
8963 <!--page 184 -->
8964 declarations, the pragma takes effect from its occurrence until another
8965 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
8966 When inside a compound statement, the pragma takes effect from its occurrence until
8967 another CX_LIMITED_RANGE pragma is encountered (including within a nested
8968 compound statement), or until the end of the compound statement; at the end of a
8969 compound statement the state for the pragma is restored to its condition just before the
8970 compound statement. If this pragma is used in any other context, the behavior is
8971 undefined. The default state for the pragma is ''off''.
8974 <p><small><a name="note169" href="#note169">169)</a> The purpose of the pragma is to allow the implementation to use the formulas:
8976 <pre>
8977 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
8980 </pre>
8981 where the programmer can determine they are safe.
8982 </small>
8989 <pre>
8991 double complex cacos(double complex z);
8992 float complex cacosf(float complex z);
8993 long double complex cacosl(long double complex z);
8994 </pre>
8997 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
9001 The cacos functions return the complex arc cosine value, in the range of a strip
9002 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
9003 real axis.
9008 <pre>
9010 double complex casin(double complex z);
9011 float complex casinf(float complex z);
9012 long double complex casinl(long double complex z);
9013 </pre>
9016 The casin functions compute the complex arc sine of z, with branch cuts outside the
9020 The casin functions return the complex arc sine value, in the range of a strip
9022 along the real axis.
9023 <!--page 185 -->
9028 <pre>
9030 double complex catan(double complex z);
9031 float complex catanf(float complex z);
9032 long double complex catanl(long double complex z);
9033 </pre>
9036 The catan functions compute the complex arc tangent of z, with branch cuts outside the
9037 interval [-i, +i] along the imaginary axis.
9040 The catan functions return the complex arc tangent value, in the range of a strip
9042 along the real axis.
9047 <pre>
9049 double complex ccos(double complex z);
9050 float complex ccosf(float complex z);
9051 long double complex ccosl(long double complex z);
9052 </pre>
9055 The ccos functions compute the complex cosine of z.
9058 The ccos functions return the complex cosine value.
9063 <pre>
9065 double complex csin(double complex z);
9066 float complex csinf(float complex z);
9067 long double complex csinl(long double complex z);
9068 </pre>
9071 The csin functions compute the complex sine of z.
9074 The csin functions return the complex sine value.
9075 <!--page 186 -->
9080 <pre>
9082 double complex ctan(double complex z);
9083 float complex ctanf(float complex z);
9084 long double complex ctanl(long double complex z);
9085 </pre>
9088 The ctan functions compute the complex tangent of z.
9091 The ctan functions return the complex tangent value.
9098 <pre>
9100 double complex cacosh(double complex z);
9101 float complex cacoshf(float complex z);
9102 long double complex cacoshl(long double complex z);
9103 </pre>
9106 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
9107 cut at values less than 1 along the real axis.
9110 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
9111 half-strip of non-negative values along the real axis and in the interval [-ipi , +ipi ] along
9112 the imaginary axis.
9117 <pre>
9119 double complex casinh(double complex z);
9120 float complex casinhf(float complex z);
9121 long double complex casinhl(long double complex z);
9122 </pre>
9125 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
9126 outside the interval [-i, +i] along the imaginary axis.
9127 <!--page 187 -->
9130 The casinh functions return the complex arc hyperbolic sine value, in the range of a
9132 along the imaginary axis.
9137 <pre>
9139 double complex catanh(double complex z);
9140 float complex catanhf(float complex z);
9141 long double complex catanhl(long double complex z);
9142 </pre>
9145 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
9149 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
9151 along the imaginary axis.
9156 <pre>
9158 double complex ccosh(double complex z);
9159 float complex ccoshf(float complex z);
9160 long double complex ccoshl(long double complex z);
9161 </pre>
9164 The ccosh functions compute the complex hyperbolic cosine of z.
9167 The ccosh functions return the complex hyperbolic cosine value.
9172 <!--page 188 -->
9173 <pre>
9175 double complex csinh(double complex z);
9176 float complex csinhf(float complex z);
9177 long double complex csinhl(long double complex z);
9178 </pre>
9181 The csinh functions compute the complex hyperbolic sine of z.
9184 The csinh functions return the complex hyperbolic sine value.
9189 <pre>
9191 double complex ctanh(double complex z);
9192 float complex ctanhf(float complex z);
9193 long double complex ctanhl(long double complex z);
9194 </pre>
9197 The ctanh functions compute the complex hyperbolic tangent of z.
9200 The ctanh functions return the complex hyperbolic tangent value.
9207 <pre>
9209 double complex cexp(double complex z);
9210 float complex cexpf(float complex z);
9211 long double complex cexpl(long double complex z);
9212 </pre>
9215 The cexp functions compute the complex base-e exponential of z.
9218 The cexp functions return the complex base-e exponential value.
9223 <!--page 189 -->
9224 <pre>
9226 double complex clog(double complex z);
9227 float complex clogf(float complex z);
9228 long double complex clogl(long double complex z);
9229 </pre>
9232 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
9233 cut along the negative real axis.
9236 The clog functions return the complex natural logarithm value, in the range of a strip
9237 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
9238 imaginary axis.
9245 <pre>
9247 double cabs(double complex z);
9248 float cabsf(float complex z);
9249 long double cabsl(long double complex z);
9250 </pre>
9253 The cabs functions compute the complex absolute value (also called norm, modulus, or
9254 magnitude) of z.
9257 The cabs functions return the complex absolute value.
9262 <pre>
9264 double complex cpow(double complex x, double complex y);
9265 float complex cpowf(float complex x, float complex y);
9266 long double complex cpowl(long double complex x,
9267 long double complex y);
9268 </pre>
9271 The cpow functions compute the complex power function xy , with a branch cut for the
9272 first parameter along the negative real axis.
9275 The cpow functions return the complex power function value.
9276 <!--page 190 -->
9281 <pre>
9283 double complex csqrt(double complex z);
9284 float complex csqrtf(float complex z);
9285 long double complex csqrtl(long double complex z);
9286 </pre>
9289 The csqrt functions compute the complex square root of z, with a branch cut along the
9290 negative real axis.
9293 The csqrt functions return the complex square root value, in the range of the right half-
9294 plane (including the imaginary axis).
9301 <pre>
9303 double carg(double complex z);
9304 float cargf(float complex z);
9305 long double cargl(long double complex z);
9306 </pre>
9309 The carg functions compute the argument (also called phase angle) of z, with a branch
9310 cut along the negative real axis.
9313 The carg functions return the value of the argument in the interval [-pi , +pi ].
9318 <!--page 191 -->
9319 <pre>
9321 double cimag(double complex z);
9322 float cimagf(float complex z);
9323 long double cimagl(long double complex z);
9324 </pre>
9327 The cimag functions compute the imaginary part of z.<sup><a href="#note170"><b>170)</b></a></sup>
9330 The cimag functions return the imaginary part value (as a real).
9333 <p><small><a name="note170" href="#note170">170)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
9334 </small>
9339 <pre>
9341 double complex conj(double complex z);
9342 float complex conjf(float complex z);
9343 long double complex conjl(long double complex z);
9344 </pre>
9347 The conj functions compute the complex conjugate of z, by reversing the sign of its
9348 imaginary part.
9351 The conj functions return the complex conjugate value.
9356 <pre>
9358 double complex cproj(double complex z);
9359 float complex cprojf(float complex z);
9360 long double complex cprojl(long double complex z);
9361 </pre>
9364 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
9365 z except that all complex infinities (even those with one infinite part and one NaN part)
9366 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
9367 equivalent to
9368 <pre>
9369 INFINITY + I * copysign(0.0, cimag(z))
9370 </pre>
9373 The cproj functions return the value of the projection onto the Riemann sphere.
9378 <!--page 192 -->
9383 <pre>
9385 double creal(double complex z);
9386 float crealf(float complex z);
9387 long double creall(long double complex z);
9388 </pre>
9394 The creal functions return the real part value.
9399 <!--page 193 -->
9402 <p><small><a name="note171" href="#note171">171)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
9403 </small>
9407 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
9408 characters.<sup><a href="#note172"><b>172)</b></a></sup> In all cases the argument is an int, the value of which shall be
9409 representable as an unsigned char or shall equal the value of the macro EOF. If the
9410 argument has any other value, the behavior is undefined.
9412 The behavior of these functions is affected by the current locale. Those functions that
9413 have locale-specific aspects only when not in the "C" locale are noted below.
9415 The term printing character refers to a member of a locale-specific set of characters, each
9416 of which occupies one printing position on a display device; the term control character
9417 refers to a member of a locale-specific set of characters that are not printing
9418 characters.<sup><a href="#note173"><b>173)</b></a></sup> All letters and digits are printing characters.
9419 <p><b> Forward references</b>: EOF (<a href="#7.19.1">7.19.1</a>), localization (<a href="#7.11">7.11</a>).
9422 <p><small><a name="note172" href="#note172">172)</a> See ''future library directions'' (<a href="#7.26.2">7.26.2</a>).
9423 </small>
9424 <p><small><a name="note173" href="#note173">173)</a> In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
9425 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
9427 </small>
9431 The functions in this subclause return nonzero (true) if and only if the value of the
9432 argument c conforms to that in the description of the function.
9437 <pre>
9439 int isalnum(int c);
9440 </pre>
9443 The isalnum function tests for any character for which isalpha or isdigit is true.
9448 <pre>
9450 int isalpha(int c);
9451 </pre>
9454 The isalpha function tests for any character for which isupper or islower is true,
9455 or any character that is one of a locale-specific set of alphabetic characters for which
9459 <!--page 194 -->
9460 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note174"><b>174)</b></a></sup> In the "C" locale,
9461 isalpha returns true only for the characters for which isupper or islower is true.
9464 <p><small><a name="note174" href="#note174">174)</a> The functions islower and isupper test true or false separately for each of these additional
9465 characters; all four combinations are possible.
9466 </small>
9471 <pre>
9473 int isblank(int c);
9474 </pre>
9477 The isblank function tests for any character that is a standard blank character or is one
9478 of a locale-specific set of characters for which isspace is true and that is used to
9479 separate words within a line of text. The standard blank characters are the following:
9480 space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
9481 for the standard blank characters.
9486 <pre>
9488 int iscntrl(int c);
9489 </pre>
9492 The iscntrl function tests for any control character.
9497 <pre>
9499 int isdigit(int c);
9500 </pre>
9503 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
9508 <pre>
9510 int isgraph(int c);
9511 </pre>
9516 <!--page 195 -->
9519 The isgraph function tests for any printing character except space (' ').
9524 <pre>
9526 int islower(int c);
9527 </pre>
9530 The islower function tests for any character that is a lowercase letter or is one of a
9531 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9532 isspace is true. In the "C" locale, islower returns true only for the lowercase
9538 <pre>
9540 int isprint(int c);
9541 </pre>
9544 The isprint function tests for any printing character including space (' ').
9549 <pre>
9551 int ispunct(int c);
9552 </pre>
9555 The ispunct function tests for any printing character that is one of a locale-specific set
9556 of punctuation characters for which neither isspace nor isalnum is true. In the "C"
9557 locale, ispunct returns true for every printing character for which neither isspace
9558 nor isalnum is true.
9563 <pre>
9565 int isspace(int c);
9566 </pre>
9569 The isspace function tests for any character that is a standard white-space character or
9570 is one of a locale-specific set of characters for which isalnum is false. The standard
9571 <!--page 196 -->
9572 white-space characters are the following: space (' '), form feed ('\f'), new-line
9573 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
9574 "C" locale, isspace returns true only for the standard white-space characters.
9579 <pre>
9581 int isupper(int c);
9582 </pre>
9585 The isupper function tests for any character that is an uppercase letter or is one of a
9586 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9587 isspace is true. In the "C" locale, isupper returns true only for the uppercase
9593 <pre>
9595 int isxdigit(int c);
9596 </pre>
9599 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
9606 <pre>
9608 int tolower(int c);
9609 </pre>
9612 The tolower function converts an uppercase letter to a corresponding lowercase letter.
9615 If the argument is a character for which isupper is true and there are one or more
9616 corresponding characters, as specified by the current locale, for which islower is true,
9617 the tolower function returns one of the corresponding characters (always the same one
9618 for any given locale); otherwise, the argument is returned unchanged.
9619 <!--page 197 -->
9624 <pre>
9626 int toupper(int c);
9627 </pre>
9630 The toupper function converts a lowercase letter to a corresponding uppercase letter.
9633 If the argument is a character for which islower is true and there are one or more
9634 corresponding characters, as specified by the current locale, for which isupper is true,
9635 the toupper function returns one of the corresponding characters (always the same one
9636 for any given locale); otherwise, the argument is returned unchanged.
9637 <!--page 198 -->
9641 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
9642 conditions.
9644 The macros are
9645 <pre>
9646 EDOM
9647 EILSEQ
9648 ERANGE
9649 </pre>
9650 which expand to integer constant expressions with type int, distinct positive values, and
9651 which are suitable for use in #if preprocessing directives; and
9652 <pre>
9653 errno
9654 </pre>
9655 which expands to a modifiable lvalue<sup><a href="#note175"><b>175)</b></a></sup> that has type int, the value of which is set to a
9656 positive error number by several library functions. It is unspecified whether errno is a
9657 macro or an identifier declared with external linkage. If a macro definition is suppressed
9658 in order to access an actual object, or a program defines an identifier with the name
9659 errno, the behavior is undefined.
9661 The value of errno is zero at program startup, but is never set to zero by any library
9662 function.<sup><a href="#note176"><b>176)</b></a></sup> The value of errno may be set to nonzero by a library function call
9663 whether or not there is an error, provided the use of errno is not documented in the
9664 description of the function in this International Standard.
9666 Additional macro definitions, beginning with E and a digit or E and an uppercase
9667 letter,<sup><a href="#note177"><b>177)</b></a></sup> may also be specified by the implementation.
9672 <!--page 199 -->
9675 <p><small><a name="note175" href="#note175">175)</a> The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue
9676 resulting from a function call (for example, *errno()).
9677 </small>
9678 <p><small><a name="note176" href="#note176">176)</a> Thus, a program that uses errno for error checking should set it to zero before a library function call,
9679 then inspect it before a subsequent library function call. Of course, a library function can save the
9680 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
9681 value is still zero just before the return.
9682 </small>
9683 <p><small><a name="note177" href="#note177">177)</a> See ''future library directions'' (<a href="#7.26.3">7.26.3</a>).
9684 </small>
9688 The header <a href="#7.6"><fenv.h></a> declares two types and several macros and functions to provide
9689 access to the floating-point environment. The floating-point environment refers
9690 collectively to any floating-point status flags and control modes supported by the
9691 implementation.<sup><a href="#note178"><b>178)</b></a></sup> A floating-point status flag is a system variable whose value is set
9692 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
9693 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note179"><b>179)</b></a></sup> A floating-
9694 point control mode is a system variable whose value may be set by the user to affect the
9695 subsequent behavior of floating-point arithmetic.
9697 Certain programming conventions support the intended model of use for the floating-
9699 <ul>
9700 <li> a function call does not alter its caller's floating-point control modes, clear its caller's
9701 floating-point status flags, nor depend on the state of its caller's floating-point status
9702 flags unless the function is so documented;
9703 <li> a function call is assumed to require default floating-point control modes, unless its
9704 documentation promises otherwise;
9705 <li> a function call is assumed to have the potential for raising floating-point exceptions,
9706 unless its documentation promises otherwise.
9707 </ul>
9709 The type
9710 <pre>
9711 fenv_t
9712 </pre>
9713 represents the entire floating-point environment.
9715 The type
9716 <pre>
9717 fexcept_t
9718 </pre>
9719 represents the floating-point status flags collectively, including any status the
9720 implementation associates with the flags.
9725 <!--page 200 -->
9727 Each of the macros
9728 <pre>
9729 FE_DIVBYZERO
9730 FE_INEXACT
9731 FE_INVALID
9732 FE_OVERFLOW
9733 FE_UNDERFLOW
9734 </pre>
9735 is defined if and only if the implementation supports the floating-point exception by
9736 means of the functions in 7.6.2.<sup><a href="#note181"><b>181)</b></a></sup> Additional implementation-defined floating-point
9737 exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
9738 be specified by the implementation. The defined macros expand to integer constant
9739 expressions with values such that bitwise ORs of all combinations of the macros result in
9740 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
9743 The macro
9744 <pre>
9745 FE_ALL_EXCEPT
9746 </pre>
9747 is simply the bitwise OR of all floating-point exception macros defined by the
9748 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
9750 Each of the macros
9751 <pre>
9752 FE_DOWNWARD
9753 FE_TONEAREST
9754 FE_TOWARDZERO
9755 FE_UPWARD
9756 </pre>
9757 is defined if and only if the implementation supports getting and setting the represented
9758 rounding direction by means of the fegetround and fesetround functions.
9759 Additional implementation-defined rounding directions, with macro definitions beginning
9760 with FE_ and an uppercase letter, may also be specified by the implementation. The
9761 defined macros expand to integer constant expressions whose values are distinct
9764 The macro
9768 <!--page 201 -->
9769 <pre>
9770 FE_DFL_ENV
9771 </pre>
9772 represents the default floating-point environment -- the one installed at program startup
9773 -- and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
9776 Additional implementation-defined environments, with macro definitions beginning with
9777 FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
9778 also be specified by the implementation.
9781 <p><small><a name="note178" href="#note178">178)</a> This header is designed to support the floating-point exception status flags and directed-rounding
9782 control modes required by IEC 60559, and other similar floating-point state information. Also it is
9783 designed to facilitate code portability among all systems.
9784 </small>
9785 <p><small><a name="note179" href="#note179">179)</a> A floating-point status flag is not an object and can be set more than once within an expression.
9786 </small>
9787 <p><small><a name="note180" href="#note180">180)</a> With these conventions, a programmer can safely assume default floating-point control modes (or be
9788 unaware of them). The responsibilities associated with accessing the floating-point environment fall
9789 on the programmer or program that does so explicitly.
9790 </small>
9791 <p><small><a name="note181" href="#note181">181)</a> The implementation supports an exception if there are circumstances where a call to at least one of the
9792 functions in <a href="#7.6.2">7.6.2</a>, using the macro as the appropriate argument, will succeed. It is not necessary for
9793 all the functions to succeed all the time.
9794 </small>
9795 <p><small><a name="note182" href="#note182">182)</a> The macros should be distinct powers of two.
9796 </small>
9797 <p><small><a name="note183" href="#note183">183)</a> Even though the rounding direction macros may expand to constants corresponding to the values of
9798 FLT_ROUNDS, they are not required to do so.
9799 </small>
9804 <pre>
9806 #pragma STDC FENV_ACCESS on-off-switch
9807 </pre>
9810 The FENV_ACCESS pragma provides a means to inform the implementation when a
9811 program might access the floating-point environment to test floating-point status flags or
9812 run under non-default floating-point control modes.<sup><a href="#note184"><b>184)</b></a></sup> The pragma shall occur either
9813 outside external declarations or preceding all explicit declarations and statements inside a
9814 compound statement. When outside external declarations, the pragma takes effect from
9815 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
9816 the translation unit. When inside a compound statement, the pragma takes effect from its
9817 occurrence until another FENV_ACCESS pragma is encountered (including within a
9818 nested compound statement), or until the end of the compound statement; at the end of a
9819 compound statement the state for the pragma is restored to its condition just before the
9820 compound statement. If this pragma is used in any other context, the behavior is
9821 undefined. If part of a program tests floating-point status flags, sets floating-point control
9822 modes, or runs under non-default mode settings, but was translated with the state for the
9823 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
9824 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
9825 the program translated with FENV_ACCESS ''off'' to a part translated with
9826 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
9827 floating-point control modes have their default settings.)
9832 <!--page 202 -->
9834 EXAMPLE
9835 <pre>
9837 void f(double x)
9838 {
9839 #pragma STDC FENV_ACCESS ON
9840 void g(double);
9841 void h(double);
9842 /* ... */
9843 g(x + 1);
9844 h(x + 1);
9845 /* ... */
9846 }
9847 </pre>
9849 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
9850 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
9851 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note185"><b>185)</b></a></sup>
9855 <p><small><a name="note184" href="#note184">184)</a> The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
9856 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
9857 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
9858 modes are in effect and the flags are not tested.
9859 </small>
9860 <p><small><a name="note185" href="#note185">185)</a> The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
9861 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
9862 ''off'', just one evaluation of x + 1 would suffice.
9863 </small>
9867 The following functions provide access to the floating-point status flags.<sup><a href="#note186"><b>186)</b></a></sup> The int
9868 input argument for the functions represents a subset of floating-point exceptions, and can
9869 be zero or the bitwise OR of one or more floating-point exception macros, for example
9870 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
9871 functions is undefined.
9874 <p><small><a name="note186" href="#note186">186)</a> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
9875 abstraction of flags that are either set or clear. An implementation may endow floating-point status
9876 flags with more information -- for example, the address of the code which first raised the floating-
9877 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
9878 content of flags.
9879 </small>
9884 <pre>
9886 int feclearexcept(int excepts);
9887 </pre>
9890 The feclearexcept function attempts to clear the supported floating-point exceptions
9891 represented by its argument.
9894 The feclearexcept function returns zero if the excepts argument is zero or if all
9895 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
9898 <!--page 203 -->
9903 <pre>
9905 int fegetexceptflag(fexcept_t *flagp,
9906 int excepts);
9907 </pre>
9910 The fegetexceptflag function attempts to store an implementation-defined
9911 representation of the states of the floating-point status flags indicated by the argument
9912 excepts in the object pointed to by the argument flagp.
9915 The fegetexceptflag function returns zero if the representation was successfully
9916 stored. Otherwise, it returns a nonzero value.
9921 <pre>
9923 int feraiseexcept(int excepts);
9924 </pre>
9927 The feraiseexcept function attempts to raise the supported floating-point exceptions
9928 represented by its argument.<sup><a href="#note187"><b>187)</b></a></sup> The order in which these floating-point exceptions are
9929 raised is unspecified, except as stated in <a href="#F.7.6">F.7.6</a>. Whether the feraiseexcept function
9930 additionally raises the ''inexact'' floating-point exception whenever it raises the
9931 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
9934 The feraiseexcept function returns zero if the excepts argument is zero or if all
9935 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
9940 <!--page 204 -->
9943 <p><small><a name="note187" href="#note187">187)</a> The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
9944 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
9946 </small>
9951 <pre>
9953 int fesetexceptflag(const fexcept_t *flagp,
9954 int excepts);
9955 </pre>
9958 The fesetexceptflag function attempts to set the floating-point status flags
9959 indicated by the argument excepts to the states stored in the object pointed to by
9960 flagp. The value of *flagp shall have been set by a previous call to
9961 fegetexceptflag whose second argument represented at least those floating-point
9962 exceptions represented by the argument excepts. This function does not raise floating-
9963 point exceptions, but only sets the state of the flags.
9966 The fesetexceptflag function returns zero if the excepts argument is zero or if
9967 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
9968 a nonzero value.
9973 <pre>
9975 int fetestexcept(int excepts);
9976 </pre>
9979 The fetestexcept function determines which of a specified subset of the floating-
9980 point exception flags are currently set. The excepts argument specifies the floating-
9984 The fetestexcept function returns the value of the bitwise OR of the floating-point
9985 exception macros corresponding to the currently set floating-point exceptions included in
9986 excepts.
9988 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
9993 <!--page 205 -->
9994 <pre>
9996 /* ... */
9997 {
9998 #pragma STDC FENV_ACCESS ON
9999 int set_excepts;
10000 feclearexcept(FE_INVALID | FE_OVERFLOW);
10001 // maybe raise exceptions
10002 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
10003 if (set_excepts & FE_INVALID) f();
10004 if (set_excepts & FE_OVERFLOW) g();
10005 /* ... */
10006 }
10007 </pre>
10011 <p><small><a name="note188" href="#note188">188)</a> This mechanism allows testing several floating-point exceptions with just one function call.
10012 </small>
10016 The fegetround and fesetround functions provide control of rounding direction
10017 modes.
10022 <pre>
10024 int fegetround(void);
10025 </pre>
10028 The fegetround function gets the current rounding direction.
10031 The fegetround function returns the value of the rounding direction macro
10032 representing the current rounding direction or a negative value if there is no such
10033 rounding direction macro or the current rounding direction is not determinable.
10038 <pre>
10040 int fesetround(int round);
10041 </pre>
10044 The fesetround function establishes the rounding direction represented by its
10045 argument round. If the argument is not equal to the value of a rounding direction macro,
10046 the rounding direction is not changed.
10049 The fesetround function returns zero if and only if the requested rounding direction
10050 was established.
10051 <!--page 206 -->
10053 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
10054 rounding direction fails.
10055 <pre>
10058 void f(int round_dir)
10059 {
10060 #pragma STDC FENV_ACCESS ON
10061 int save_round;
10062 int setround_ok;
10063 save_round = fegetround();
10064 setround_ok = fesetround(round_dir);
10065 assert(setround_ok == 0);
10066 /* ... */
10067 fesetround(save_round);
10068 /* ... */
10069 }
10070 </pre>
10075 The functions in this section manage the floating-point environment -- status flags and
10076 control modes -- as one entity.
10081 <pre>
10083 int fegetenv(fenv_t *envp);
10084 </pre>
10087 The fegetenv function attempts to store the current floating-point environment in the
10088 object pointed to by envp.
10091 The fegetenv function returns zero if the environment was successfully stored.
10092 Otherwise, it returns a nonzero value.
10097 <pre>
10099 int feholdexcept(fenv_t *envp);
10100 </pre>
10103 The feholdexcept function saves the current floating-point environment in the object
10104 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
10105 (continue on floating-point exceptions) mode, if available, for all floating-point
10107 <!--page 207 -->
10110 The feholdexcept function returns zero if and only if non-stop floating-point
10111 exception handling was successfully installed.
10114 <p><small><a name="note189" href="#note189">189)</a> IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
10115 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
10116 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
10117 function to write routines that hide spurious floating-point exceptions from their callers.
10118 </small>
10123 <pre>
10125 int fesetenv(const fenv_t *envp);
10126 </pre>
10129 The fesetenv function attempts to establish the floating-point environment represented
10130 by the object pointed to by envp. The argument envp shall point to an object set by a
10131 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
10132 Note that fesetenv merely installs the state of the floating-point status flags
10133 represented through its argument, and does not raise these floating-point exceptions.
10136 The fesetenv function returns zero if the environment was successfully established.
10137 Otherwise, it returns a nonzero value.
10142 <pre>
10144 int feupdateenv(const fenv_t *envp);
10145 </pre>
10148 The feupdateenv function attempts to save the currently raised floating-point
10149 exceptions in its automatic storage, install the floating-point environment represented by
10150 the object pointed to by envp, and then raise the saved floating-point exceptions. The
10151 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
10152 or equal a floating-point environment macro.
10155 The feupdateenv function returns zero if all the actions were successfully carried out.
10156 Otherwise, it returns a nonzero value.
10161 <!--page 208 -->
10163 EXAMPLE Hide spurious underflow floating-point exceptions:
10164 <!--page 209 -->
10165 <pre>
10167 double f(double x)
10168 {
10169 #pragma STDC FENV_ACCESS ON
10170 double result;
10171 fenv_t save_env;
10172 if (feholdexcept(&save_env))
10173 return /* indication of an environmental problem */;
10174 // compute result
10175 if (/* test spurious underflow */)
10176 if (feclearexcept(FE_UNDERFLOW))
10177 return /* indication of an environmental problem */;
10178 if (feupdateenv(&save_env))
10179 return /* indication of an environmental problem */;
10180 return result;
10181 }
10182 </pre>
10186 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
10187 parameters of the standard floating-point types.
10189 The macros, their meanings, and the constraints (or restrictions) on their values are listed
10191 <!--page 210 -->
10195 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.18"><stdint.h></a> and extends it with
10196 additional facilities provided by hosted implementations.
10198 It declares functions for manipulating greatest-width integers and converting numeric
10199 character strings to greatest-width integers, and it declares the type
10200 <pre>
10201 imaxdiv_t
10202 </pre>
10203 which is a structure type that is the type of the value returned by the imaxdiv function.
10204 For each type declared in <a href="#7.18"><stdint.h></a>, it defines corresponding macros for conversion
10205 specifiers for use with the formatted input/output functions.<sup><a href="#note190"><b>190)</b></a></sup>
10206 <p><b> Forward references</b>: integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>), formatted input/output
10207 functions (<a href="#7.19.6">7.19.6</a>), formatted wide character input/output functions (<a href="#7.24.2">7.24.2</a>).
10210 <p><small><a name="note190" href="#note190">190)</a> See ''future library directions'' (<a href="#7.26.4">7.26.4</a>).
10211 </small>
10215 Each of the following object-like macros<sup><a href="#note191"><b>191)</b></a></sup> expands to a character string literal
10216 containing a conversion specifier, possibly modified by a length modifier, suitable for use
10217 within the format argument of a formatted input/output function when converting the
10218 corresponding integer type. These macro names have the general form of PRI (character
10219 string literals for the fprintf and fwprintf family) or SCN (character string literals
10220 for the fscanf and fwscanf family),<sup><a href="#note192"><b>192)</b></a></sup> followed by the conversion specifier,
10221 followed by a name corresponding to a similar type name in <a href="#7.18.1">7.18.1</a>. In these names, N
10222 represents the width of the type as described in <a href="#7.18.1">7.18.1</a>. For example, PRIdFAST32 can
10223 be used in a format string to print the value of an integer of type int_fast32_t.
10225 The fprintf macros for signed integers are:
10226 <pre>
10227 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
10228 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
10229 </pre>
10234 <!--page 211 -->
10236 The fprintf macros for unsigned integers are:
10237 <pre>
10238 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
10239 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
10240 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
10241 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
10242 </pre>
10244 The fscanf macros for signed integers are:
10245 <pre>
10246 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
10247 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
10248 </pre>
10250 The fscanf macros for unsigned integers are:
10251 <pre>
10252 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
10253 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
10254 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
10255 </pre>
10257 For each type that the implementation provides in <a href="#7.18"><stdint.h></a>, the corresponding
10258 fprintf macros shall be defined and the corresponding fscanf macros shall be
10259 defined unless the implementation does not have a suitable fscanf length modifier for
10260 the type.
10262 EXAMPLE
10263 <pre>
10266 int main(void)
10267 {
10268 uintmax_t i = UINTMAX_MAX; // this type always exists
10269 wprintf(L"The largest integer value is %020"
10270 PRIxMAX "\n", i);
10271 return 0;
10272 }
10273 </pre>
10277 <p><small><a name="note191" href="#note191">191)</a> C++ implementations should define these macros only when __STDC_FORMAT_MACROS is defined
10279 </small>
10280 <p><small><a name="note192" href="#note192">192)</a> Separate macros are given for use with fprintf and fscanf functions because, in the general case,
10281 different format specifiers may be required for fprintf and fscanf, even when the type is the
10282 same.
10283 </small>
10290 <pre>
10292 intmax_t imaxabs(intmax_t j);
10293 </pre>
10296 The imaxabs function computes the absolute value of an integer j. If the result cannot
10301 <!--page 212 -->
10304 The imaxabs function returns the absolute value.
10307 <p><small><a name="note193" href="#note193">193)</a> The absolute value of the most negative number cannot be represented in two's complement.
10308 </small>
10313 <pre>
10315 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
10316 </pre>
10319 The imaxdiv function computes numer / denom and numer % denom in a single
10320 operation.
10323 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
10324 quotient and the remainder. The structure shall contain (in either order) the members
10325 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
10326 either part of the result cannot be represented, the behavior is undefined.
10331 <pre>
10333 intmax_t strtoimax(const char * restrict nptr,
10334 char ** restrict endptr, int base);
10335 uintmax_t strtoumax(const char * restrict nptr,
10336 char ** restrict endptr, int base);
10337 </pre>
10340 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
10341 strtoul, and strtoull functions, except that the initial portion of the string is
10342 converted to intmax_t and uintmax_t representation, respectively.
10345 The strtoimax and strtoumax functions return the converted value, if any. If no
10346 conversion could be performed, zero is returned. If the correct value is outside the range
10347 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
10348 (according to the return type and sign of the value, if any), and the value of the macro
10349 ERANGE is stored in errno.
10352 <!--page 213 -->
10357 <pre>
10360 intmax_t wcstoimax(const wchar_t * restrict nptr,
10361 wchar_t ** restrict endptr, int base);
10362 uintmax_t wcstoumax(const wchar_t * restrict nptr,
10363 wchar_t ** restrict endptr, int base);
10364 </pre>
10367 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
10368 wcstoul, and wcstoull functions except that the initial portion of the wide string is
10369 converted to intmax_t and uintmax_t representation, respectively.
10372 The wcstoimax function returns the converted value, if any. If no conversion could be
10373 performed, zero is returned. If the correct value is outside the range of representable
10374 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
10375 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
10376 errno.
10379 <!--page 214 -->
10383 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
10384 to the corresponding tokens (on the right):
10385 <!--page 215 -->
10386 <pre>
10387 and &&
10388 and_eq &=
10389 bitand &
10390 bitor |
10391 compl ~
10392 not !
10393 not_eq !=
10394 or ||
10395 or_eq |=
10396 xor ^
10397 xor_eq ^=
10398 </pre>
10402 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
10403 parameters of the standard integer types.
10405 The macros, their meanings, and the constraints (or restrictions) on their values are listed
10407 <!--page 216 -->
10411 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
10413 The type is
10414 <pre>
10415 struct lconv
10416 </pre>
10417 which contains members related to the formatting of numeric values. The structure shall
10418 contain at least the following members, in any order. The semantics of the members and
10419 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
10420 the values specified in the comments.
10421 <!--page 217 -->
10422 <pre>
10423 char *decimal_point; // "."
10424 char *thousands_sep; // ""
10425 char *grouping; // ""
10426 char *mon_decimal_point; // ""
10427 char *mon_thousands_sep; // ""
10428 char *mon_grouping; // ""
10429 char *positive_sign; // ""
10430 char *negative_sign; // ""
10431 char *currency_symbol; // ""
10432 char frac_digits; // CHAR_MAX
10433 char p_cs_precedes; // CHAR_MAX
10434 char n_cs_precedes; // CHAR_MAX
10435 char p_sep_by_space; // CHAR_MAX
10436 char n_sep_by_space; // CHAR_MAX
10437 char p_sign_posn; // CHAR_MAX
10438 char n_sign_posn; // CHAR_MAX
10439 char *int_curr_symbol; // ""
10440 char int_frac_digits; // CHAR_MAX
10441 char int_p_cs_precedes; // CHAR_MAX
10442 char int_n_cs_precedes; // CHAR_MAX
10443 char int_p_sep_by_space; // CHAR_MAX
10444 char int_n_sep_by_space; // CHAR_MAX
10445 char int_p_sign_posn; // CHAR_MAX
10446 char int_n_sign_posn; // CHAR_MAX
10447 </pre>
10450 <pre>
10451 LC_ALL
10452 LC_COLLATE
10453 LC_CTYPE
10454 LC_MONETARY
10455 LC_NUMERIC
10456 LC_TIME
10457 </pre>
10458 which expand to integer constant expressions with distinct values, suitable for use as the
10459 first argument to the setlocale function.<sup><a href="#note194"><b>194)</b></a></sup> Additional macro definitions, beginning
10460 with the characters LC_ and an uppercase letter,<sup><a href="#note195"><b>195)</b></a></sup> may also be specified by the
10461 implementation.
10464 <p><small><a name="note194" href="#note194">194)</a> ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
10465 </small>
10466 <p><small><a name="note195" href="#note195">195)</a> See ''future library directions'' (<a href="#7.26.5">7.26.5</a>).
10467 </small>
10474 <pre>
10476 char *setlocale(int category, const char *locale);
10477 </pre>
10480 The setlocale function selects the appropriate portion of the program's locale as
10481 specified by the category and locale arguments. The setlocale function may be
10482 used to change or query the program's entire current locale or portions thereof. The value
10483 LC_ALL for category names the program's entire locale; the other values for
10484 category name only a portion of the program's locale. LC_COLLATE affects the
10485 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
10486 the character handling functions<sup><a href="#note196"><b>196)</b></a></sup> and the multibyte and wide character functions.
10487 LC_MONETARY affects the monetary formatting information returned by the
10488 localeconv function. LC_NUMERIC affects the decimal-point character for the
10489 formatted input/output functions and the string conversion functions, as well as the
10490 nonmonetary formatting information returned by the localeconv function. LC_TIME
10491 affects the behavior of the strftime and wcsftime functions.
10493 A value of "C" for locale specifies the minimal environment for C translation; a value
10494 of "" for locale specifies the locale-specific native environment. Other
10495 implementation-defined strings may be passed as the second argument to setlocale.
10497 <!--page 218 -->
10499 At program startup, the equivalent of
10500 <pre>
10501 setlocale(LC_ALL, "C");
10502 </pre>
10503 is executed.
10505 The implementation shall behave as if no library function calls the setlocale function.
10508 If a pointer to a string is given for locale and the selection can be honored, the
10509 setlocale function returns a pointer to the string associated with the specified
10510 category for the new locale. If the selection cannot be honored, the setlocale
10511 function returns a null pointer and the program's locale is not changed.
10513 A null pointer for locale causes the setlocale function to return a pointer to the
10514 string associated with the category for the program's current locale; the program's
10517 The pointer to string returned by the setlocale function is such that a subsequent call
10518 with that string value and its associated category will restore that part of the program's
10519 locale. The string pointed to shall not be modified by the program, but may be
10520 overwritten by a subsequent call to the setlocale function.
10521 <p><b> Forward references</b>: formatted input/output functions (<a href="#7.19.6">7.19.6</a>), multibyte/wide
10522 character conversion functions (<a href="#7.20.7">7.20.7</a>), multibyte/wide string conversion functions
10523 (<a href="#7.20.8">7.20.8</a>), numeric conversion functions (<a href="#7.20.1">7.20.1</a>), the strcoll function (<a href="#7.21.4.3">7.21.4.3</a>), the
10524 strftime function (<a href="#7.23.3.5">7.23.3.5</a>), the strxfrm function (<a href="#7.21.4.5">7.21.4.5</a>).
10527 <p><small><a name="note196" href="#note196">196)</a> The only functions in <a href="#7.4">7.4</a> whose behavior is not affected by the current locale are isdigit and
10528 isxdigit.
10529 </small>
10530 <p><small><a name="note197" href="#note197">197)</a> The implementation shall arrange to encode in a string the various categories due to a heterogeneous
10531 locale when category has the value LC_ALL.
10532 </small>
10539 <pre>
10541 struct lconv *localeconv(void);
10542 </pre>
10545 The localeconv function sets the components of an object with type struct lconv
10546 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
10547 according to the rules of the current locale.
10549 The members of the structure with type char * are pointers to strings, any of which
10550 (except decimal_point) can point to "", to indicate that the value is not available in
10551 the current locale or is of zero length. Apart from grouping and mon_grouping, the
10553 <!--page 219 -->
10554 strings shall start and end in the initial shift state. The members with type char are
10555 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
10556 available in the current locale. The members include the following:
10557 <dl>
10558 <dt> char *decimal_point
10559 <dd>
10560 The decimal-point character used to format nonmonetary quantities.
10561 <dt> char *thousands_sep
10562 <dd>
10563 The character used to separate groups of digits before the decimal-point
10564 character in formatted nonmonetary quantities.
10565 <dt> char *grouping
10566 <dd>
10567 A string whose elements indicate the size of each group of digits in
10568 formatted nonmonetary quantities.
10569 <dt> char *mon_decimal_point
10570 <dd>
10571 The decimal-point used to format monetary quantities.
10572 <dt> char *mon_thousands_sep
10573 <dd>
10574 The separator for groups of digits before the decimal-point in formatted
10575 monetary quantities.
10576 <dt> char *mon_grouping
10577 <dd>
10578 A string whose elements indicate the size of each group of digits in
10579 formatted monetary quantities.
10580 <dt> char *positive_sign
10581 <dd>
10582 The string used to indicate a nonnegative-valued formatted monetary
10583 quantity.
10584 <dt> char *negative_sign
10585 <dd>
10586 The string used to indicate a negative-valued formatted monetary quantity.
10587 <dt> char *currency_symbol
10588 <dd>
10589 The local currency symbol applicable to the current locale.
10590 <dt> char frac_digits
10591 <dd>
10592 The number of fractional digits (those after the decimal-point) to be
10593 displayed in a locally formatted monetary quantity.
10594 <dt> char p_cs_precedes
10595 <dd>
10597 succeeds the value for a nonnegative locally formatted monetary quantity.
10598 <dt> char n_cs_precedes
10599 <!--page 220 -->
10600 <dd>
10602 succeeds the value for a negative locally formatted monetary quantity.
10603 <dt> char p_sep_by_space
10604 <dd>
10605 Set to a value indicating the separation of the currency_symbol, the
10606 sign string, and the value for a nonnegative locally formatted monetary
10607 quantity.
10608 <dt> char n_sep_by_space
10609 <dd>
10610 Set to a value indicating the separation of the currency_symbol, the
10611 sign string, and the value for a negative locally formatted monetary
10612 quantity.
10613 <dt> char p_sign_posn
10614 <dd>
10615 Set to a value indicating the positioning of the positive_sign for a
10616 nonnegative locally formatted monetary quantity.
10617 <dt> char n_sign_posn
10618 <dd>
10619 Set to a value indicating the positioning of the negative_sign for a
10620 negative locally formatted monetary quantity.
10621 <dt> char *int_curr_symbol
10622 <dd>
10623 The international currency symbol applicable to the current locale. The
10624 first three characters contain the alphabetic international currency symbol
10625 in accordance with those specified in ISO 4217. The fourth character
10626 (immediately preceding the null character) is the character used to separate
10627 the international currency symbol from the monetary quantity.
10628 <dt> char int_frac_digits
10629 <dd>
10630 The number of fractional digits (those after the decimal-point) to be
10631 displayed in an internationally formatted monetary quantity.
10632 <dt> char int_p_cs_precedes
10633 <dd>
10635 succeeds the value for a nonnegative internationally formatted monetary
10636 quantity.
10637 <dt> char int_n_cs_precedes
10638 <dd>
10640 succeeds the value for a negative internationally formatted monetary
10641 quantity.
10642 <dt> char int_p_sep_by_space
10643 <!--page 221 -->
10644 <dd>
10645 Set to a value indicating the separation of the int_curr_symbol, the
10646 sign string, and the value for a nonnegative internationally formatted
10647 monetary quantity.
10648 <dt> char int_n_sep_by_space
10649 <dd>
10650 Set to a value indicating the separation of the int_curr_symbol, the
10651 sign string, and the value for a negative internationally formatted monetary
10652 quantity.
10653 <dt> char int_p_sign_posn
10654 <dd>
10655 Set to a value indicating the positioning of the positive_sign for a
10656 nonnegative internationally formatted monetary quantity.
10657 <dt> char int_n_sign_posn
10658 <dd>
10659 Set to a value indicating the positioning of the negative_sign for a
10660 negative internationally formatted monetary quantity.
10661 </dl>
10663 The elements of grouping and mon_grouping are interpreted according to the
10664 following:
10665 <dl>
10668 digits.
10670 The next element is examined to determine the size of the next group of
10671 digits before the current group.
10672 </dl>
10674 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
10675 and int_n_sep_by_space are interpreted according to the following:
10676 <dl>
10678 <dt> 1 <dd>If the currency symbol and sign string are adjacent, a space separates them from the
10679 value; otherwise, a space separates the currency symbol from the value.
10681 otherwise, a space separates the sign string from the value.
10682 </dl>
10683 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
10684 int_curr_symbol is used instead of a space.
10686 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
10687 int_n_sign_posn are interpreted according to the following:
10688 <dl>
10694 </dl>
10695 <!--page 222 -->
10697 The implementation shall behave as if no library function calls the localeconv
10698 function.
10701 The localeconv function returns a pointer to the filled-in object. The structure
10702 pointed to by the return value shall not be modified by the program, but may be
10703 overwritten by a subsequent call to the localeconv function. In addition, calls to the
10704 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
10705 overwrite the contents of the structure.
10707 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
10708 monetary quantities.
10709 <pre>
10710 Local format International format
10712 Country Positive Negative Positive Negative
10718 </pre>
10720 For these four countries, the respective values for the monetary members of the structure returned by
10721 localeconv could be:
10722 <pre>
10723 Country1 Country2 Country3 Country4
10731 frac_digits 2 0 2 2
10732 p_cs_precedes 0 1 1 1
10733 n_cs_precedes 0 1 1 1
10734 p_sep_by_space 1 0 1 0
10735 n_sep_by_space 1 0 2 0
10736 p_sign_posn 1 1 1 1
10737 n_sign_posn 1 1 4 2
10739 int_frac_digits 2 0 2 2
10740 int_p_cs_precedes 1 1 1 1
10741 int_n_cs_precedes 1 1 1 1
10742 int_p_sep_by_space 1 1 1 1
10743 int_n_sep_by_space 2 1 2 1
10744 int_p_sign_posn 1 1 1 1
10745 int_n_sign_posn 4 1 4 2
10746 </pre>
10747 <!--page 223 -->
10749 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
10750 affect the formatted value.
10751 <pre>
10752 p_sep_by_space
10753 p_cs_precedes p_sign_posn 0 1 2
10766 </pre>
10768 <!--page 224 -->
10771 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
10772 several macros. Most synopses specify a family of functions consisting of a principal
10773 function with one or more double parameters, a double return value, or both; and
10774 other functions with the same name but with f and l suffixes, which are corresponding
10775 functions with float and long double parameters, return values, or both.<sup><a href="#note198"><b>198)</b></a></sup>
10776 Integer arithmetic functions and conversion functions are discussed later.
10778 The types
10779 <pre>
10780 float_t
10781 double_t
10782 </pre>
10783 are floating types at least as wide as float and double, respectively, and such that
10784 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
10785 float_t and double_t are float and double, respectively; if
10786 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
10787 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
10790 The macro
10791 <pre>
10792 HUGE_VAL
10793 </pre>
10794 expands to a positive double constant expression, not necessarily representable as a
10795 float. The macros
10796 <pre>
10797 HUGE_VALF
10798 HUGE_VALL
10799 </pre>
10800 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note200"><b>200)</b></a></sup>
10802 The macro
10803 <pre>
10804 INFINITY
10805 </pre>
10806 expands to a constant expression of type float representing positive or unsigned
10807 infinity, if available; else to a positive constant of type float that overflows at
10811 <!--page 225 -->
10814 The macro
10815 <pre>
10816 NAN
10817 </pre>
10818 is defined if and only if the implementation supports quiet NaNs for the float type. It
10819 expands to a constant expression of type float representing a quiet NaN.
10821 The number classification macros
10822 <pre>
10823 FP_INFINITE
10824 FP_NAN
10825 FP_NORMAL
10826 FP_SUBNORMAL
10827 FP_ZERO
10828 </pre>
10829 represent the mutually exclusive kinds of floating-point values. They expand to integer
10830 constant expressions with distinct values. Additional implementation-defined floating-
10831 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
10832 may also be specified by the implementation.
10834 The macro
10835 <pre>
10836 FP_FAST_FMA
10837 </pre>
10838 is optionally defined. If defined, it indicates that the fma function generally executes
10839 about as fast as, or faster than, a multiply and an add of double operands.<sup><a href="#note202"><b>202)</b></a></sup> The
10840 macros
10841 <pre>
10842 FP_FAST_FMAF
10843 FP_FAST_FMAL
10844 </pre>
10845 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
10846 these macros expand to the integer constant 1.
10848 The macros
10849 <pre>
10850 FP_ILOGB0
10851 FP_ILOGBNAN
10852 </pre>
10853 expand to integer constant expressions whose values are returned by ilogb(x) if x is
10854 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
10855 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
10858 <!--page 226 -->
10860 The macros
10861 <pre>
10862 MATH_ERRNO
10863 MATH_ERREXCEPT
10864 </pre>
10866 <pre>
10867 math_errhandling
10868 </pre>
10869 expands to an expression that has type int and the value MATH_ERRNO,
10870 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
10871 constant for the duration of the program. It is unspecified whether
10872 math_errhandling is a macro or an identifier with external linkage. If a macro
10873 definition is suppressed or a program defines an identifier with the name
10874 math_errhandling, the behavior is undefined. If the expression
10875 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
10876 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
10880 <p><small><a name="note198" href="#note198">198)</a> Particularly on systems with wide expression evaluation, a <a href="#7.12"><math.h></a> function might pass arguments
10881 and return values in wider format than the synopsis prototype indicates.
10882 </small>
10883 <p><small><a name="note199" href="#note199">199)</a> The types float_t and double_t are intended to be the implementation's most efficient types at
10885 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
10886 </small>
10887 <p><small><a name="note200" href="#note200">200)</a> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
10888 supports infinities.
10889 </small>
10890 <p><small><a name="note201" href="#note201">201)</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.
10891 </small>
10892 <p><small><a name="note202" href="#note202">202)</a> Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
10893 directly with a hardware multiply-add instruction. Software implementations are expected to be
10894 substantially slower.
10895 </small>
10899 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
10900 values of its input arguments, except where stated otherwise. Each function shall execute
10901 as if it were a single operation without generating any externally visible exceptional
10902 conditions.
10904 For all functions, a domain error occurs if an input argument is outside the domain over
10905 which the mathematical function is defined. The description of each function lists any
10906 required domain errors; an implementation may define additional domain errors, provided
10907 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note203"><b>203)</b></a></sup> On a
10908 domain error, the function returns an implementation-defined value; if the integer
10909 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
10910 errno acquires the value EDOM; if the integer expression math_errhandling &
10911 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
10913 Similarly, a range error occurs if the mathematical result of the function cannot be
10914 represented in an object of the specified type, due to extreme magnitude.
10916 A floating result overflows if the magnitude of the mathematical result is finite but so
10917 large that the mathematical result cannot be represented without extraordinary roundoff
10918 error in an object of the specified type. If a floating result overflows and default rounding
10919 is in effect, or if the mathematical result is an exact infinity from finite arguments (for
10920 example log(0.0)), then the function returns the value of the macro HUGE_VAL,
10923 <!--page 227 -->
10924 HUGE_VALF, or HUGE_VALL according to the return type, with the same sign as the
10925 correct value of the function; if the integer expression math_errhandling &
10926 MATH_ERRNO is nonzero, the integer expression errno acquires the value ERANGE; if
10927 the integer expression math_errhandling & MATH_ERREXCEPT is nonzero, the
10928 ''divide-by-zero'' floating-point exception is raised if the mathematical result is an exact
10929 infinity and the ''overflow'' floating-point exception is raised otherwise.
10931 The result underflows if the magnitude of the mathematical result is so small that the
10932 mathematical result cannot be represented, without extraordinary roundoff error, in an
10933 object of the specified type.<sup><a href="#note204"><b>204)</b></a></sup> If the result underflows, the function returns an
10934 implementation-defined value whose magnitude is no greater than the smallest
10935 normalized positive number in the specified type; if the integer expression
10936 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
10937 value ERANGE is implementation-defined; if the integer expression
10938 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
10939 floating-point exception is raised is implementation-defined.
10942 <p><small><a name="note203" href="#note203">203)</a> In an implementation that supports infinities, this allows an infinity as an argument to be a domain
10943 error if the mathematical domain of the function does not include the infinity.
10944 </small>
10945 <p><small><a name="note204" href="#note204">204)</a> The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
10946 also ''flush-to-zero'' underflow.
10947 </small>
10952 <pre>
10954 #pragma STDC FP_CONTRACT on-off-switch
10955 </pre>
10958 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
10959 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
10960 either outside external declarations or preceding all explicit declarations and statements
10961 inside a compound statement. When outside external declarations, the pragma takes
10962 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
10963 the end of the translation unit. When inside a compound statement, the pragma takes
10964 effect from its occurrence until another FP_CONTRACT pragma is encountered
10965 (including within a nested compound statement), or until the end of the compound
10966 statement; at the end of a compound statement the state for the pragma is restored to its
10967 condition just before the compound statement. If this pragma is used in any other
10968 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
10969 implementation-defined.
10974 <!--page 228 -->
10978 In the synopses in this subclause, real-floating indicates that the argument shall be an
10979 expression of real floating type.
10984 <pre>
10986 int fpclassify(real-floating x);
10987 </pre>
10990 The fpclassify macro classifies its argument value as NaN, infinite, normal,
10991 subnormal, zero, or into another implementation-defined category. First, an argument
10992 represented in a format wider than its semantic type is converted to its semantic type.
10993 Then classification is based on the type of the argument.<sup><a href="#note205"><b>205)</b></a></sup>
10996 The fpclassify macro returns the value of the number classification macro
10997 appropriate to the value of its argument.
10999 EXAMPLE The fpclassify macro might be implemented in terms of ordinary functions as
11000 <pre>
11001 #define fpclassify(x) \
11002 ((sizeof (x) == sizeof (float)) ? __fpclassifyf(x) : \
11003 (sizeof (x) == sizeof (double)) ? __fpclassifyd(x) : \
11004 __fpclassifyl(x))
11005 </pre>
11009 <p><small><a name="note205" href="#note205">205)</a> Since an expression can be evaluated with more range and precision than its type has, it is important to
11010 know the type that classification is based on. For example, a normal long double value might
11011 become subnormal when converted to double, and zero when converted to float.
11012 </small>
11017 <pre>
11019 int isfinite(real-floating x);
11020 </pre>
11023 The isfinite macro determines whether its argument has a finite value (zero,
11024 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
11025 format wider than its semantic type is converted to its semantic type. Then determination
11026 is based on the type of the argument.
11031 <!--page 229 -->
11034 The isfinite macro returns a nonzero value if and only if its argument has a finite
11035 value.
11040 <pre>
11042 int isinf(real-floating x);
11043 </pre>
11046 The isinf macro determines whether its argument value is an infinity (positive or
11047 negative). First, an argument represented in a format wider than its semantic type is
11048 converted to its semantic type. Then determination is based on the type of the argument.
11051 The isinf macro returns a nonzero value if and only if its argument has an infinite
11052 value.
11057 <pre>
11059 int isnan(real-floating x);
11060 </pre>
11063 The isnan macro determines whether its argument value is a NaN. First, an argument
11064 represented in a format wider than its semantic type is converted to its semantic type.
11065 Then determination is based on the type of the argument.<sup><a href="#note206"><b>206)</b></a></sup>
11068 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
11071 <p><small><a name="note206" href="#note206">206)</a> For the isnan macro, the type for determination does not matter unless the implementation supports
11072 NaNs in the evaluation type but not in the semantic type.
11073 </small>
11078 <pre>
11080 int isnormal(real-floating x);
11081 </pre>
11086 <!--page 230 -->
11089 The isnormal macro determines whether its argument value is normal (neither zero,
11090 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
11091 semantic type is converted to its semantic type. Then determination is based on the type
11092 of the argument.
11095 The isnormal macro returns a nonzero value if and only if its argument has a normal
11096 value.
11101 <pre>
11103 int signbit(real-floating x);
11104 </pre>
11107 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note207"><b>207)</b></a></sup>
11110 The signbit macro returns a nonzero value if and only if the sign of its argument value
11111 is negative.
11114 <p><small><a name="note207" href="#note207">207)</a> The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
11115 unsigned, it is treated as positive.
11116 </small>
11123 <pre>
11125 double acos(double x);
11126 float acosf(float x);
11127 long double acosl(long double x);
11128 </pre>
11131 The acos functions compute the principal value of the arc cosine of x. A domain error
11135 The acos functions return arccos x in the interval [0, pi ] radians.
11140 <!--page 231 -->
11145 <pre>
11147 double asin(double x);
11148 float asinf(float x);
11149 long double asinl(long double x);
11150 </pre>
11153 The asin functions compute the principal value of the arc sine of x. A domain error
11162 <pre>
11164 double atan(double x);
11165 float atanf(float x);
11166 long double atanl(long double x);
11167 </pre>
11170 The atan functions compute the principal value of the arc tangent of x.
11178 <pre>
11180 double atan2(double y, double x);
11181 float atan2f(float y, float x);
11182 long double atan2l(long double y, long double x);
11183 </pre>
11186 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
11187 arguments to determine the quadrant of the return value. A domain error may occur if
11188 both arguments are zero.
11191 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
11192 <!--page 232 -->
11197 <pre>
11199 double cos(double x);
11200 float cosf(float x);
11201 long double cosl(long double x);
11202 </pre>
11205 The cos functions compute the cosine of x (measured in radians).
11208 The cos functions return cos x.
11213 <pre>
11215 double sin(double x);
11216 float sinf(float x);
11217 long double sinl(long double x);
11218 </pre>
11221 The sin functions compute the sine of x (measured in radians).
11224 The sin functions return sin x.
11229 <pre>
11231 double tan(double x);
11232 float tanf(float x);
11233 long double tanl(long double x);
11234 </pre>
11237 The tan functions return the tangent of x (measured in radians).
11240 The tan functions return tan x.
11241 <!--page 233 -->
11248 <pre>
11250 double acosh(double x);
11251 float acoshf(float x);
11252 long double acoshl(long double x);
11253 </pre>
11256 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
11257 error occurs for arguments less than 1.
11260 The acosh functions return arcosh x in the interval [0, +(inf)].
11265 <pre>
11267 double asinh(double x);
11268 float asinhf(float x);
11269 long double asinhl(long double x);
11270 </pre>
11273 The asinh functions compute the arc hyperbolic sine of x.
11276 The asinh functions return arsinh x.
11281 <pre>
11283 double atanh(double x);
11284 float atanhf(float x);
11285 long double atanhl(long double x);
11286 </pre>
11289 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
11292 <!--page 234 -->
11295 The atanh functions return artanh x.
11300 <pre>
11302 double cosh(double x);
11303 float coshf(float x);
11304 long double coshl(long double x);
11305 </pre>
11308 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
11309 magnitude of x is too large.
11312 The cosh functions return cosh x.
11317 <pre>
11319 double sinh(double x);
11320 float sinhf(float x);
11321 long double sinhl(long double x);
11322 </pre>
11325 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
11326 magnitude of x is too large.
11329 The sinh functions return sinh x.
11334 <pre>
11336 double tanh(double x);
11337 float tanhf(float x);
11338 long double tanhl(long double x);
11339 </pre>
11342 The tanh functions compute the hyperbolic tangent of x.
11343 <!--page 235 -->
11346 The tanh functions return tanh x.
11353 <pre>
11355 double exp(double x);
11356 float expf(float x);
11357 long double expl(long double x);
11358 </pre>
11361 The exp functions compute the base-e exponential of x. A range error occurs if the
11362 magnitude of x is too large.
11370 <pre>
11372 double exp2(double x);
11373 float exp2f(float x);
11374 long double exp2l(long double x);
11375 </pre>
11378 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
11379 magnitude of x is too large.
11387 <!--page 236 -->
11388 <pre>
11390 double expm1(double x);
11391 float expm1f(float x);
11392 long double expm1l(long double x);
11393 </pre>
11396 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
11403 <p><small><a name="note208" href="#note208">208)</a> For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
11404 </small>
11409 <pre>
11411 double frexp(double value, int *exp);
11412 float frexpf(float value, int *exp);
11413 long double frexpl(long double value, int *exp);
11414 </pre>
11417 The frexp functions break a floating-point number into a normalized fraction and an
11418 integral power of 2. They store the integer in the int object pointed to by exp.
11421 If value is not a floating-point number, the results are unspecified. Otherwise, the
11423 zero, and value equals x 2<sup>*exp</sup> . If value is zero, both parts of the result are zero.
11428 <pre>
11430 int ilogb(double x);
11431 int ilogbf(float x);
11432 int ilogbl(long double x);
11433 </pre>
11436 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
11437 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
11438 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
11439 the corresponding logb function and casting the returned value to type int. A domain
11440 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
11441 the range of the return type, the numeric result is unspecified.
11446 <!--page 237 -->
11449 The ilogb functions return the exponent of x as a signed int value.
11455 <pre>
11457 double ldexp(double x, int exp);
11458 float ldexpf(float x, int exp);
11459 long double ldexpl(long double x, int exp);
11460 </pre>
11463 The ldexp functions multiply a floating-point number by an integral power of 2. A
11464 range error may occur.
11472 <pre>
11474 double log(double x);
11475 float logf(float x);
11476 long double logl(long double x);
11477 </pre>
11480 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
11481 the argument is negative. A range error may occur if the argument is zero.
11484 The log functions return loge x.
11489 <!--page 238 -->
11490 <pre>
11492 double log10(double x);
11493 float log10f(float x);
11494 long double log10l(long double x);
11495 </pre>
11498 The log10 functions compute the base-10 (common) logarithm of x. A domain error
11499 occurs if the argument is negative. A range error may occur if the argument is zero.
11502 The log10 functions return log10 x.
11507 <pre>
11509 double log1p(double x);
11510 float log1pf(float x);
11511 long double log1pl(long double x);
11512 </pre>
11515 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note209"><b>209)</b></a></sup>
11516 A domain error occurs if the argument is less than -1. A range error may occur if the
11517 argument equals -1.
11520 The log1p functions return loge (1 + x).
11523 <p><small><a name="note209" href="#note209">209)</a> For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
11524 </small>
11529 <pre>
11531 double log2(double x);
11532 float log2f(float x);
11533 long double log2l(long double x);
11534 </pre>
11537 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
11538 argument is less than zero. A range error may occur if the argument is zero.
11541 The log2 functions return log2 x.
11546 <!--page 239 -->
11551 <pre>
11553 double logb(double x);
11554 float logbf(float x);
11555 long double logbl(long double x);
11556 </pre>
11559 The logb functions extract the exponent of x, as a signed integer value in floating-point
11560 format. If x is subnormal it is treated as though it were normalized; thus, for positive
11561 finite x,
11562 <pre>
11564 </pre>
11565 A domain error or range error may occur if the argument is zero.
11568 The logb functions return the signed exponent of x.
11573 <pre>
11575 double modf(double value, double *iptr);
11576 float modff(float value, float *iptr);
11577 long double modfl(long double value, long double *iptr);
11578 </pre>
11581 The modf functions break the argument value into integral and fractional parts, each of
11582 which has the same type and sign as the argument. They store the integral part (in
11583 floating-point format) in the object pointed to by iptr.
11586 The modf functions return the signed fractional part of value.
11587 <!--page 240 -->
11592 <pre>
11594 double scalbn(double x, int n);
11595 float scalbnf(float x, int n);
11596 long double scalbnl(long double x, int n);
11597 double scalbln(double x, long int n);
11598 float scalblnf(float x, long int n);
11599 long double scalblnl(long double x, long int n);
11600 </pre>
11614 <pre>
11616 double cbrt(double x);
11617 float cbrtf(float x);
11618 long double cbrtl(long double x);
11619 </pre>
11622 The cbrt functions compute the real cube root of x.
11630 <pre>
11632 double fabs(double x);
11633 float fabsf(float x);
11634 long double fabsl(long double x);
11635 </pre>
11638 The fabs functions compute the absolute value of a floating-point number x.
11639 <!--page 241 -->
11642 The fabs functions return | x |.
11647 <pre>
11649 double hypot(double x, double y);
11650 float hypotf(float x, float y);
11651 long double hypotl(long double x, long double y);
11652 </pre>
11655 The hypot functions compute the square root of the sum of the squares of x and y,
11656 without undue overflow or underflow. A range error may occur.
11665 <pre>
11667 double pow(double x, double y);
11668 float powf(float x, float y);
11669 long double powl(long double x, long double y);
11670 </pre>
11673 The pow functions compute x raised to the power y. A domain error occurs if x is finite
11674 and negative and y is finite and not an integer value. A range error may occur. A domain
11675 error may occur if x is zero and y is zero. A domain error or range error may occur if x
11676 is zero and y is less than zero.
11684 <!--page 242 -->
11685 <pre>
11687 double sqrt(double x);
11688 float sqrtf(float x);
11689 long double sqrtl(long double x);
11690 </pre>
11693 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
11694 the argument is less than zero.
11697 The sqrt functions return (sqrt)(x).
11704 <pre>
11706 double erf(double x);
11707 float erff(float x);
11708 long double erfl(long double x);
11709 </pre>
11712 The erf functions compute the error function of x.
11715 The erf functions return
11716 <pre>
11717 2 x
11719 (sqrt)(pi) 0
11720 </pre>
11725 <pre>
11727 double erfc(double x);
11728 float erfcf(float x);
11729 long double erfcl(long double x);
11730 </pre>
11733 The erfc functions compute the complementary error function of x. A range error
11734 occurs if x is too large.
11737 The erfc functions return
11738 <pre>
11739 2 (inf)
11741 (sqrt)(pi) x
11742 </pre>
11744 <!--page 243 -->
11748 <pre>
11750 double lgamma(double x);
11751 float lgammaf(float x);
11752 long double lgammal(long double x);
11753 </pre>
11756 The lgamma functions compute the natural logarithm of the absolute value of gamma of
11757 x. A range error occurs if x is too large. A range error may occur if x is a negative
11758 integer or zero.
11761 The lgamma functions return loge | (Gamma)(x) |.
11766 <pre>
11768 double tgamma(double x);
11769 float tgammaf(float x);
11770 long double tgammal(long double x);
11771 </pre>
11774 The tgamma functions compute the gamma function of x. A domain error or range error
11775 may occur if x is a negative integer or zero. A range error may occur if the magnitude of
11776 x is too large or too small.
11779 The tgamma functions return (Gamma)(x).
11786 <pre>
11788 double ceil(double x);
11789 float ceilf(float x);
11790 long double ceill(long double x);
11791 </pre>
11794 The ceil functions compute the smallest integer value not less than x.
11795 <!--page 244 -->
11798 The ceil functions return [^x^], expressed as a floating-point number.
11803 <pre>
11805 double floor(double x);
11806 float floorf(float x);
11807 long double floorl(long double x);
11808 </pre>
11811 The floor functions compute the largest integer value not greater than x.
11814 The floor functions return [_x_], expressed as a floating-point number.
11819 <pre>
11821 double nearbyint(double x);
11822 float nearbyintf(float x);
11823 long double nearbyintl(long double x);
11824 </pre>
11827 The nearbyint functions round their argument to an integer value in floating-point
11828 format, using the current rounding direction and without raising the ''inexact'' floating-
11829 point exception.
11832 The nearbyint functions return the rounded integer value.
11837 <pre>
11839 double rint(double x);
11840 float rintf(float x);
11841 long double rintl(long double x);
11842 </pre>
11845 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
11846 rint functions may raise the ''inexact'' floating-point exception if the result differs in
11847 value from the argument.
11848 <!--page 245 -->
11851 The rint functions return the rounded integer value.
11856 <pre>
11858 long int lrint(double x);
11859 long int lrintf(float x);
11860 long int lrintl(long double x);
11861 long long int llrint(double x);
11862 long long int llrintf(float x);
11863 long long int llrintl(long double x);
11864 </pre>
11867 The lrint and llrint functions round their argument to the nearest integer value,
11868 rounding according to the current rounding direction. If the rounded value is outside the
11869 range of the return type, the numeric result is unspecified and a domain error or range
11870 error may occur. *
11873 The lrint and llrint functions return the rounded integer value.
11878 <pre>
11880 double round(double x);
11881 float roundf(float x);
11882 long double roundl(long double x);
11883 </pre>
11886 The round functions round their argument to the nearest integer value in floating-point
11887 format, rounding halfway cases away from zero, regardless of the current rounding
11888 direction.
11891 The round functions return the rounded integer value.
11892 <!--page 246 -->
11897 <pre>
11899 long int lround(double x);
11900 long int lroundf(float x);
11901 long int lroundl(long double x);
11902 long long int llround(double x);
11903 long long int llroundf(float x);
11904 long long int llroundl(long double x);
11905 </pre>
11908 The lround and llround functions round their argument to the nearest integer value,
11909 rounding halfway cases away from zero, regardless of the current rounding direction. If
11910 the rounded value is outside the range of the return type, the numeric result is unspecified
11911 and a domain error or range error may occur.
11914 The lround and llround functions return the rounded integer value.
11919 <pre>
11921 double trunc(double x);
11922 float truncf(float x);
11923 long double truncl(long double x);
11924 </pre>
11927 The trunc functions round their argument to the integer value, in floating format,
11928 nearest to but no larger in magnitude than the argument.
11931 The trunc functions return the truncated integer value.
11932 <!--page 247 -->
11939 <pre>
11941 double fmod(double x, double y);
11942 float fmodf(float x, float y);
11943 long double fmodl(long double x, long double y);
11944 </pre>
11947 The fmod functions compute the floating-point remainder of x/y.
11950 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
11951 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
11952 whether a domain error occurs or the fmod functions return zero is implementation-
11953 defined.
11958 <pre>
11960 double remainder(double x, double y);
11961 float remainderf(float x, float y);
11962 long double remainderl(long double x, long double y);
11963 </pre>
11966 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note210"><b>210)</b></a></sup>
11969 The remainder functions return x REM y. If y is zero, whether a domain error occurs
11970 or the functions return zero is implementation defined.
11975 <!--page 248 -->
11978 <p><small><a name="note210" href="#note210">210)</a> ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
11979 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
11980 | n - x/y | = 1/2, then n is even. Thus, the remainder is always exact. If r = 0, its sign shall be that of
11981 x.'' This definition is applicable for all implementations.
11982 </small>
11987 <pre>
11989 double remquo(double x, double y, int *quo);
11990 float remquof(float x, float y, int *quo);
11991 long double remquol(long double x, long double y,
11992 int *quo);
11993 </pre>
11996 The remquo functions compute the same remainder as the remainder functions. In
11997 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
11998 magnitude is congruent modulo 2<sup>n</sup> to the magnitude of the integral quotient of x/y, where
11999 n is an implementation-defined integer greater than or equal to 3.
12002 The remquo functions return x REM y. If y is zero, the value stored in the object
12003 pointed to by quo is unspecified and whether a domain error occurs or the functions
12004 return zero is implementation defined.
12011 <pre>
12013 double copysign(double x, double y);
12014 float copysignf(float x, float y);
12015 long double copysignl(long double x, long double y);
12016 </pre>
12019 The copysign functions produce a value with the magnitude of x and the sign of y.
12020 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
12021 represent a signed zero but do not treat negative zero consistently in arithmetic
12022 operations, the copysign functions regard the sign of zero as positive.
12025 The copysign functions return a value with the magnitude of x and the sign of y.
12026 <!--page 249 -->
12031 <pre>
12033 double nan(const char *tagp);
12034 float nanf(const char *tagp);
12035 long double nanl(const char *tagp);
12036 </pre>
12041 strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
12042 sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
12043 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
12044 and strtold.
12047 The nan functions return a quiet NaN, if available, with content indicated through tagp.
12048 If the implementation does not support quiet NaNs, the functions return zero.
12049 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
12054 <pre>
12056 double nextafter(double x, double y);
12057 float nextafterf(float x, float y);
12058 long double nextafterl(long double x, long double y);
12059 </pre>
12062 The nextafter functions determine the next representable value, in the type of the
12063 function, after x in the direction of y, where x and y are first converted to the type of the
12064 function.<sup><a href="#note211"><b>211)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
12065 if the magnitude of x is the largest finite value representable in the type and the result is
12066 infinite or not representable in the type.
12069 The nextafter functions return the next representable value in the specified format
12070 after x in the direction of y.
12073 <!--page 250 -->
12076 <p><small><a name="note211" href="#note211">211)</a> The argument values are converted to the type of the function, even by a macro implementation of the
12077 function.
12078 </small>
12083 <pre>
12085 double nexttoward(double x, long double y);
12086 float nexttowardf(float x, long double y);
12087 long double nexttowardl(long double x, long double y);
12088 </pre>
12091 The nexttoward functions are equivalent to the nextafter functions except that the
12092 second parameter has type long double and the functions return y converted to the
12096 <p><small><a name="note212" href="#note212">212)</a> The result of the nexttoward functions is determined in the type of the function, without loss of
12097 range or precision in a floating second argument.
12098 </small>
12100 <h4><a name="7.12.12" href="#7.12.12">7.12.12 Maximum, minimum, and positive difference functions</a></h4>
12105 <pre>
12107 double fdim(double x, double y);
12108 float fdimf(float x, float y);
12109 long double fdiml(long double x, long double y);
12110 </pre>
12113 The fdim functions determine the positive difference between their arguments:
12114 <pre>
12115 {x - y if x > y
12116 {
12118 </pre>
12119 A range error may occur.
12122 The fdim functions return the positive difference value.
12127 <pre>
12129 double fmax(double x, double y);
12130 float fmaxf(float x, float y);
12131 long double fmaxl(long double x, long double y);
12132 </pre>
12136 <!--page 251 -->
12139 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note213"><b>213)</b></a></sup>
12142 The fmax functions return the maximum numeric value of their arguments.
12145 <p><small><a name="note213" href="#note213">213)</a> NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
12147 </small>
12152 <pre>
12154 double fmin(double x, double y);
12155 float fminf(float x, float y);
12156 long double fminl(long double x, long double y);
12157 </pre>
12160 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note214"><b>214)</b></a></sup>
12163 The fmin functions return the minimum numeric value of their arguments.
12166 <p><small><a name="note214" href="#note214">214)</a> The fmin functions are analogous to the fmax functions in their treatment of NaNs.
12167 </small>
12174 <pre>
12176 double fma(double x, double y, double z);
12177 float fmaf(float x, float y, float z);
12178 long double fmal(long double x, long double y,
12179 long double z);
12180 </pre>
12183 The fma functions compute (x y) + z, rounded as one ternary operation: they compute
12184 the value (as if) to infinite precision and round once to the result format, according to the
12185 current rounding mode. A range error may occur.
12188 The fma functions return (x y) + z, rounded as one ternary operation.
12193 <!--page 252 -->
12197 The relational and equality operators support the usual mathematical relationships
12198 between numeric values. For any ordered pair of numeric values exactly one of the
12199 relationships -- less, greater, and equal -- is true. Relational operators may raise the
12200 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
12201 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note215"><b>215)</b></a></sup> The following
12202 subclauses provide macros that are quiet (non floating-point exception raising) versions
12203 of the relational operators, and other comparison macros that facilitate writing efficient
12204 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
12205 the synopses in this subclause, real-floating indicates that the argument shall be an
12206 expression of real floating type.
12209 <p><small><a name="note215" href="#note215">215)</a> IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
12210 the operands compare unordered, as an error indicator for programs written without consideration of
12211 NaNs; the result in these cases is false.
12212 </small>
12217 <pre>
12219 int isgreater(real-floating x, real-floating y);
12220 </pre>
12223 The isgreater macro determines whether its first argument is greater than its second
12224 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
12225 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
12226 exception when x and y are unordered.
12229 The isgreater macro returns the value of (x) > (y).
12234 <pre>
12236 int isgreaterequal(real-floating x, real-floating y);
12237 </pre>
12240 The isgreaterequal macro determines whether its first argument is greater than or
12241 equal to its second argument. The value of isgreaterequal(x, y) is always equal
12243 not raise the ''invalid'' floating-point exception when x and y are unordered.
12247 <!--page 253 -->
12250 The isgreaterequal macro returns the value of (x) >= (y).
12255 <pre>
12257 int isless(real-floating x, real-floating y);
12258 </pre>
12261 The isless macro determines whether its first argument is less than its second
12262 argument. The value of isless(x, y) is always equal to (x) < (y); however,
12263 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
12264 exception when x and y are unordered.
12267 The isless macro returns the value of (x) < (y).
12272 <pre>
12274 int islessequal(real-floating x, real-floating y);
12275 </pre>
12278 The islessequal macro determines whether its first argument is less than or equal to
12279 its second argument. The value of islessequal(x, y) is always equal to
12281 the ''invalid'' floating-point exception when x and y are unordered.
12284 The islessequal macro returns the value of (x) <= (y).
12289 <pre>
12291 int islessgreater(real-floating x, real-floating y);
12292 </pre>
12295 The islessgreater macro determines whether its first argument is less than or
12296 greater than its second argument. The islessgreater(x, y) macro is similar to
12298 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
12299 and y twice).
12300 <!--page 254 -->
12308 <pre>
12310 int isunordered(real-floating x, real-floating y);
12311 </pre>
12314 The isunordered macro determines whether its arguments are unordered.
12318 <!--page 255 -->
12322 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
12323 one type, for bypassing the normal function call and return discipline.<sup><a href="#note216"><b>216)</b></a></sup>
12325 The type declared is
12326 <pre>
12327 jmp_buf
12328 </pre>
12329 which is an array type suitable for holding the information needed to restore a calling
12330 environment. The environment of a call to the setjmp macro consists of information
12331 sufficient for a call to the longjmp function to return execution to the correct block and
12332 invocation of that block, were it called recursively. It does not include the state of the
12333 floating-point status flags, of open files, or of any other component of the abstract
12334 machine.
12336 It is unspecified whether setjmp is a macro or an identifier declared with external
12337 linkage. If a macro definition is suppressed in order to access an actual function, or a
12338 program defines an external identifier with the name setjmp, the behavior is undefined.
12341 <p><small><a name="note216" href="#note216">216)</a> These functions are useful for dealing with unusual conditions encountered in a low-level function of
12342 a program.
12343 </small>
12350 <pre>
12352 int setjmp(jmp_buf env);
12353 </pre>
12356 The setjmp macro saves its calling environment in its jmp_buf argument for later use
12357 by the longjmp function.
12360 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
12361 return is from a call to the longjmp function, the setjmp macro returns a nonzero
12362 value.
12365 An invocation of the setjmp macro shall appear only in one of the following contexts:
12366 <ul>
12367 <li> the entire controlling expression of a selection or iteration statement;
12368 <li> one operand of a relational or equality operator with the other operand an integer
12369 constant expression, with the resulting expression being the entire controlling
12372 <!--page 256 -->
12373 expression of a selection or iteration statement;
12374 <li> the operand of a unary ! operator with the resulting expression being the entire
12375 controlling expression of a selection or iteration statement; or
12376 <li> the entire expression of an expression statement (possibly cast to void).
12377 </ul>
12379 If the invocation appears in any other context, the behavior is undefined.
12386 <pre>
12388 void longjmp(jmp_buf env, int val);
12389 </pre>
12392 The longjmp function restores the environment saved by the most recent invocation of
12393 the setjmp macro in the same invocation of the program with the corresponding
12394 jmp_buf argument. If there has been no such invocation, or if the function containing
12395 the invocation of the setjmp macro has terminated execution<sup><a href="#note217"><b>217)</b></a></sup> in the interim, or if the
12396 invocation of the setjmp macro was within the scope of an identifier with variably
12397 modified type and execution has left that scope in the interim, the behavior is undefined.
12399 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note218"><b>218)</b></a></sup>
12400 have state, as of the time the longjmp function was called, except that the values of
12401 objects of automatic storage duration that are local to the function containing the
12402 invocation of the corresponding setjmp macro that do not have volatile-qualified type
12403 and have been changed between the setjmp invocation and longjmp call are
12404 indeterminate.
12407 After longjmp is completed, program execution continues as if the corresponding
12408 invocation of the setjmp macro had just returned the value specified by val. The
12410 the setjmp macro returns the value 1.
12412 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
12413 might cause memory associated with a variable length array object to be squandered.
12418 <!--page 257 -->
12419 <!--page 258 -->
12420 <pre>
12422 jmp_buf buf;
12423 void g(int n);
12424 void h(int n);
12425 int n = 6;
12426 void f(void)
12427 {
12428 int x[n]; // valid: f is not terminated
12429 setjmp(buf);
12430 g(n);
12431 }
12432 void g(int n)
12433 {
12434 int a[n]; // a may remain allocated
12435 h(n);
12436 }
12437 void h(int n)
12438 {
12439 int b[n]; // b may remain allocated
12440 longjmp(buf, 2); // might cause memory loss
12441 }
12442 </pre>
12445 <p><small><a name="note217" href="#note217">217)</a> For example, by executing a return statement or because another longjmp call has caused a
12446 transfer to a setjmp invocation in a function earlier in the set of nested calls.
12447 </small>
12448 <p><small><a name="note218" href="#note218">218)</a> This includes, but is not limited to, the floating-point status flags and the state of open files.
12449 </small>
12453 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
12454 for handling various signals (conditions that may be reported during program execution).
12456 The type defined is
12457 <pre>
12458 sig_atomic_t
12459 </pre>
12460 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
12461 an atomic entity, even in the presence of asynchronous interrupts.
12463 The macros defined are
12464 <pre>
12465 SIG_DFL
12466 SIG_ERR
12467 SIG_IGN
12468 </pre>
12469 which expand to constant expressions with distinct values that have type compatible with
12470 the second argument to, and the return value of, the signal function, and whose values
12471 compare unequal to the address of any declarable function; and the following, which
12472 expand to positive integer constant expressions with type int and distinct values that are
12473 the signal numbers, each corresponding to the specified condition:
12474 <pre>
12475 SIGABRT abnormal termination, such as is initiated by the abort function
12476 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
12477 resulting in overflow
12478 SIGILL detection of an invalid function image, such as an invalid instruction
12479 SIGINT receipt of an interactive attention signal
12480 SIGSEGV an invalid access to storage
12481 SIGTERM a termination request sent to the program
12482 </pre>
12484 An implementation need not generate any of these signals, except as a result of explicit
12485 calls to the raise function. Additional signals and pointers to undeclarable functions,
12486 with macro definitions beginning, respectively, with the letters SIG and an uppercase
12487 letter or with SIG_ and an uppercase letter,<sup><a href="#note219"><b>219)</b></a></sup> may also be specified by the
12488 implementation. The complete set of signals, their semantics, and their default handling
12489 is implementation-defined; all signal numbers shall be positive.
12494 <!--page 259 -->
12497 <p><small><a name="note219" href="#note219">219)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>). The names of the signal numbers reflect the following terms
12498 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
12499 and termination.
12500 </small>
12507 <pre>
12509 void (*signal(int sig, void (*func)(int)))(int);
12510 </pre>
12513 The signal function chooses one of three ways in which receipt of the signal number
12514 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
12515 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
12516 Otherwise, func shall point to a function to be called when that signal occurs. An
12517 invocation of such a function because of a signal, or (recursively) of any further functions
12518 called by that invocation (other than functions in the standard library), is called a signal
12519 handler.
12521 When a signal occurs and func points to a function, it is implementation-defined
12522 whether the equivalent of signal(sig, SIG_DFL); is executed or the
12523 implementation prevents some implementation-defined set of signals (at least including
12524 sig) from occurring until the current signal handling has completed; in the case of
12525 SIGILL, the implementation may alternatively define that no action is taken. Then the
12526 equivalent of (*func)(sig); is executed. If and when the function returns, if the
12527 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
12528 value corresponding to a computational exception, the behavior is undefined; otherwise
12529 the program will resume execution at the point it was interrupted.
12531 If the signal occurs as the result of calling the abort or raise function, the signal
12532 handler shall not call the raise function.
12534 If the signal occurs other than as the result of calling the abort or raise function, the
12535 behavior is undefined if the signal handler refers to any object with static storage duration
12536 other than by assigning a value to an object declared as volatile sig_atomic_t, or
12537 the signal handler calls any function in the standard library other than the abort
12538 function, the _Exit function, or the signal function with the first argument equal to
12539 the signal number corresponding to the signal that caused the invocation of the handler.
12540 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
12543 At program startup, the equivalent of
12544 <pre>
12545 signal(sig, SIG_IGN);
12546 </pre>
12549 <!--page 260 -->
12550 may be executed for some signals selected in an implementation-defined manner; the
12551 equivalent of
12552 <pre>
12553 signal(sig, SIG_DFL);
12554 </pre>
12555 is executed for all other signals defined by the implementation.
12557 The implementation shall behave as if no library function calls the signal function.
12560 If the request can be honored, the signal function returns the value of func for the
12561 most recent successful call to signal for the specified signal sig. Otherwise, a value of
12562 SIG_ERR is returned and a positive value is stored in errno.
12563 <p><b> Forward references</b>: the abort function (<a href="#7.20.4.1">7.20.4.1</a>), the exit function (<a href="#7.20.4.3">7.20.4.3</a>), the
12567 <p><small><a name="note220" href="#note220">220)</a> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
12568 </small>
12575 <pre>
12577 int raise(int sig);
12578 </pre>
12581 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
12582 signal handler is called, the raise function shall not return until after the signal handler
12583 does.
12586 The raise function returns zero if successful, nonzero if unsuccessful.
12587 <!--page 261 -->
12591 The header <a href="#7.15"><stdarg.h></a> declares a type and defines four macros, for advancing
12592 through a list of arguments whose number and types are not known to the called function
12593 when it is translated.
12595 A function may be called with a variable number of arguments of varying types. As
12596 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
12597 parameter plays a special role in the access mechanism, and will be designated parmN in
12598 this description.
12600 The type declared is
12601 <pre>
12602 va_list
12603 </pre>
12604 which is an object type suitable for holding information needed by the macros
12605 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
12606 desired, the called function shall declare an object (generally referred to as ap in this
12607 subclause) having type va_list. The object ap may be passed as an argument to
12608 another function; if that function invokes the va_arg macro with parameter ap, the
12609 value of ap in the calling function is indeterminate and shall be passed to the va_end
12613 <p><small><a name="note221" href="#note221">221)</a> It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
12614 case the original function may make further use of the original list after the other function returns.
12615 </small>
12619 The va_start and va_arg macros described in this subclause shall be implemented
12620 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
12621 identifiers declared with external linkage. If a macro definition is suppressed in order to
12622 access an actual function, or a program defines an external identifier with the same name,
12623 the behavior is undefined. Each invocation of the va_start and va_copy macros
12624 shall be matched by a corresponding invocation of the va_end macro in the same
12625 function.
12630 <pre>
12632 type va_arg(va_list ap, type);
12633 </pre>
12636 The va_arg macro expands to an expression that has the specified type and the value of
12637 the next argument in the call. The parameter ap shall have been initialized by the
12638 va_start or va_copy macro (without an intervening invocation of the va_end
12640 <!--page 262 -->
12641 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
12642 values of successive arguments are returned in turn. The parameter type shall be a type
12643 name specified such that the type of a pointer to an object that has the specified type can
12644 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
12645 type is not compatible with the type of the actual next argument (as promoted according
12646 to the default argument promotions), the behavior is undefined, except for the following
12647 cases:
12648 <ul>
12649 <li> one type is a signed integer type, the other type is the corresponding unsigned integer
12650 type, and the value is representable in both types;
12651 <li> one type is pointer to void and the other is a pointer to a character type.
12652 </ul>
12655 The first invocation of the va_arg macro after that of the va_start macro returns the
12656 value of the argument after that specified by parmN . Successive invocations return the
12657 values of the remaining arguments in succession.
12662 <pre>
12664 void va_copy(va_list dest, va_list src);
12665 </pre>
12668 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
12669 been applied to dest followed by the same sequence of uses of the va_arg macro as
12670 had previously been used to reach the present state of src. Neither the va_copy nor
12671 va_start macro shall be invoked to reinitialize dest without an intervening
12672 invocation of the va_end macro for the same dest.
12675 The va_copy macro returns no value.
12680 <pre>
12682 void va_end(va_list ap);
12683 </pre>
12686 The va_end macro facilitates a normal return from the function whose variable
12687 argument list was referred to by the expansion of the va_start macro, or the function
12688 containing the expansion of the va_copy macro, that initialized the va_list ap. The
12689 va_end macro may modify ap so that it is no longer usable (without being reinitialized
12690 <!--page 263 -->
12691 by the va_start or va_copy macro). If there is no corresponding invocation of the
12692 va_start or va_copy macro, or if the va_end macro is not invoked before the
12693 return, the behavior is undefined.
12696 The va_end macro returns no value.
12701 <pre>
12703 void va_start(va_list ap, parmN);
12704 </pre>
12707 The va_start macro shall be invoked before any access to the unnamed arguments.
12709 The va_start macro initializes ap for subsequent use by the va_arg and va_end
12710 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
12711 without an intervening invocation of the va_end macro for the same ap.
12713 The parameter parmN is the identifier of the rightmost parameter in the variable
12714 parameter list in the function definition (the one just before the , ...). If the parameter
12715 parmN is declared with the register storage class, with a function or array type, or
12716 with a type that is not compatible with the type that results after application of the default
12717 argument promotions, the behavior is undefined.
12720 The va_start macro returns no value.
12722 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
12723 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
12724 pointers is specified by the first argument to f1.
12725 <!--page 264 -->
12726 <pre>
12728 #define MAXARGS 31
12729 void f1(int n_ptrs, ...)
12730 {
12731 va_list ap;
12732 char *array[MAXARGS];
12733 int ptr_no = 0;
12734 if (n_ptrs > MAXARGS)
12735 n_ptrs = MAXARGS;
12736 va_start(ap, n_ptrs);
12737 while (ptr_no < n_ptrs)
12738 array[ptr_no++] = va_arg(ap, char *);
12739 va_end(ap);
12740 f2(n_ptrs, array);
12741 }
12742 </pre>
12743 Each call to f1 is required to have visible the definition of the function or a declaration such as
12744 <pre>
12745 void f1(int, ...);
12746 </pre>
12749 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
12750 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
12751 is gathered again and passed to function f4.
12752 <!--page 265 -->
12753 <pre>
12755 #define MAXARGS 31
12756 void f3(int n_ptrs, int f4_after, ...)
12757 {
12758 va_list ap, ap_save;
12759 char *array[MAXARGS];
12760 int ptr_no = 0;
12761 if (n_ptrs > MAXARGS)
12762 n_ptrs = MAXARGS;
12763 va_start(ap, f4_after);
12764 while (ptr_no < n_ptrs) {
12765 array[ptr_no++] = va_arg(ap, char *);
12766 if (ptr_no == f4_after)
12767 va_copy(ap_save, ap);
12768 }
12769 va_end(ap);
12770 f2(n_ptrs, array);
12771 // Now process the saved copy.
12772 n_ptrs -= f4_after;
12773 ptr_no = 0;
12774 while (ptr_no < n_ptrs)
12775 array[ptr_no++] = va_arg(ap_save, char *);
12776 va_end(ap_save);
12777 f4(n_ptrs, array);
12778 }
12779 </pre>
12785 The macro
12786 <pre>
12787 bool
12788 </pre>
12789 expands to _Bool.
12791 The remaining three macros are suitable for use in #if preprocessing directives. They
12792 are
12793 <pre>
12794 true
12795 </pre>
12796 which expands to the integer constant 1,
12797 <pre>
12798 false
12799 </pre>
12800 which expands to the integer constant 0, and
12801 <pre>
12802 __bool_true_false_are_defined
12803 </pre>
12804 which expands to the integer constant 1.
12806 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
12812 <!--page 266 -->
12815 <p><small><a name="note222" href="#note222">222)</a> See ''future library directions'' (<a href="#7.26.7">7.26.7</a>).
12816 </small>
12820 The following types and macros are defined in the standard header <a href="#7.17"><stddef.h></a>. Some
12821 are also defined in other headers, as noted in their respective subclauses.
12823 The types are
12824 <pre>
12825 ptrdiff_t
12826 </pre>
12827 which is the signed integer type of the result of subtracting two pointers;
12828 <pre>
12829 size_t
12830 </pre>
12831 which is the unsigned integer type of the result of the sizeof operator; and
12832 <pre>
12833 wchar_t
12834 </pre>
12835 which is an integer type whose range of values can represent distinct codes for all
12836 members of the largest extended character set specified among the supported locales; the
12837 null character shall have the code value zero. Each member of the basic character set
12838 shall have a code value equal to its value when used as the lone character in an integer
12839 character constant if an implementation does not define
12840 __STDC_MB_MIGHT_NEQ_WC__.
12842 The macros are
12843 <pre>
12844 NULL
12845 </pre>
12846 which expands to an implementation-defined null pointer constant; and
12847 <pre>
12848 offsetof(type, member-designator)
12849 </pre>
12850 which expands to an integer constant expression that has type size_t, the value of
12851 which is the offset in bytes, to the structure member (designated by member-designator),
12852 from the beginning of its structure (designated by type). The type and member designator
12853 shall be such that given
12854 <pre>
12855 static type t;
12856 </pre>
12857 then the expression &(t.member-designator) evaluates to an address constant. (If the
12858 specified member is a bit-field, the behavior is undefined.)
12861 The types used for size_t and ptrdiff_t should not have an integer conversion rank
12862 greater than that of signed long int unless the implementation supports objects
12863 large enough to make this necessary.
12865 <!--page 267 -->
12869 The header <a href="#7.18"><stdint.h></a> declares sets of integer types having specified widths, and
12870 defines corresponding sets of macros.<sup><a href="#note223"><b>223)</b></a></sup> It also defines macros that specify limits of
12871 integer types corresponding to types defined in other standard headers.
12873 Types are defined in the following categories:
12874 <ul>
12875 <li> integer types having certain exact widths;
12876 <li> integer types having at least certain specified widths;
12877 <li> fastest integer types having at least certain specified widths;
12878 <li> integer types wide enough to hold pointers to objects;
12879 <li> integer types having greatest width.
12880 </ul>
12881 (Some of these types may denote the same type.)
12883 Corresponding macros specify limits of the declared types and construct suitable
12884 constants.
12886 For each type described herein that the implementation provides,<sup><a href="#note224"><b>224)</b></a></sup> <a href="#7.18"><stdint.h></a> shall
12887 declare that typedef name and define the associated macros. Conversely, for each type
12888 described herein that the implementation does not provide, <a href="#7.18"><stdint.h></a> shall not
12889 declare that typedef name nor shall it define the associated macros. An implementation
12890 shall provide those types described as ''required'', but need not provide any of the others
12891 (described as ''optional'').
12894 <p><small><a name="note223" href="#note223">223)</a> See ''future library directions'' (<a href="#7.26.8">7.26.8</a>).
12895 </small>
12896 <p><small><a name="note224" href="#note224">224)</a> Some of these types may denote implementation-defined extended integer types.
12897 </small>
12901 When typedef names differing only in the absence or presence of the initial u are defined,
12902 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
12903 implementation providing one of these corresponding types shall also provide the other.
12905 In the following descriptions, the symbol N represents an unsigned decimal integer with
12911 <!--page 268 -->
12915 The typedef name intN_t designates a signed integer type with width N , no padding
12916 bits, and a two's complement representation. Thus, int8_t denotes a signed integer
12917 type with a width of exactly 8 bits.
12919 The typedef name uintN_t designates an unsigned integer type with width N . Thus,
12920 uint24_t denotes an unsigned integer type with a width of exactly 24 bits.
12922 These types are optional. However, if an implementation provides integer types with
12924 two's complement representation, it shall define the corresponding typedef names.
12928 The typedef name int_leastN_t designates a signed integer type with a width of at
12929 least N , such that no signed integer type with lesser size has at least the specified width.
12930 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
12932 The typedef name uint_leastN_t designates an unsigned integer type with a width
12933 of at least N , such that no unsigned integer type with lesser size has at least the specified
12934 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
12935 least 16 bits.
12937 The following types are required:
12938 <pre>
12939 int_least8_t uint_least8_t
12940 int_least16_t uint_least16_t
12941 int_least32_t uint_least32_t
12942 int_least64_t uint_least64_t
12943 </pre>
12944 All other types of this form are optional.
12948 Each of the following types designates an integer type that is usually fastest<sup><a href="#note225"><b>225)</b></a></sup> to operate
12949 with among all integer types that have at least the specified width.
12951 The typedef name int_fastN_t designates the fastest signed integer type with a width
12952 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
12953 type with a width of at least N .
12958 <!--page 269 -->
12960 The following types are required:
12961 <pre>
12962 int_fast8_t uint_fast8_t
12963 int_fast16_t uint_fast16_t
12964 int_fast32_t uint_fast32_t
12965 int_fast64_t uint_fast64_t
12966 </pre>
12967 All other types of this form are optional.
12970 <p><small><a name="note225" href="#note225">225)</a> The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
12971 grounds for choosing one type over another, it will simply pick some integer type satisfying the
12972 signedness and width requirements.
12973 </small>
12975 <h5><a name="7.18.1.4" href="#7.18.1.4">7.18.1.4 Integer types capable of holding object pointers</a></h5>
12977 The following type designates a signed integer type with the property that any valid
12978 pointer to void can be converted to this type, then converted back to pointer to void,
12979 and the result will compare equal to the original pointer:
12980 <pre>
12981 intptr_t
12982 </pre>
12983 The following type designates an unsigned integer type with the property that any valid
12984 pointer to void can be converted to this type, then converted back to pointer to void,
12985 and the result will compare equal to the original pointer:
12986 <pre>
12987 uintptr_t
12988 </pre>
12989 These types are optional.
12993 The following type designates a signed integer type capable of representing any value of
12994 any signed integer type:
12995 <pre>
12996 intmax_t
12997 </pre>
12998 The following type designates an unsigned integer type capable of representing any value
12999 of any unsigned integer type:
13000 <pre>
13001 uintmax_t
13002 </pre>
13003 These types are required.
13007 The following object-like macros<sup><a href="#note226"><b>226)</b></a></sup> specify the minimum and maximum limits of the
13008 types declared in <a href="#7.18"><stdint.h></a>. Each macro name corresponds to a similar type name in
13011 Each instance of any defined macro shall be replaced by a constant expression suitable
13012 for use in #if preprocessing directives, and this expression shall have the same type as
13013 would an expression that is an object of the corresponding type converted according to
13015 <!--page 270 -->
13016 the integer promotions. Its implementation-defined value shall be equal to or greater in
13017 magnitude (absolute value) than the corresponding value given below, with the same sign,
13018 except where stated to be exactly the given value.
13021 <p><small><a name="note226" href="#note226">226)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
13023 </small>
13027 <ul>
13028 <li> minimum values of exact-width signed integer types
13029 <pre>
13031 </pre>
13032 <li> maximum values of exact-width signed integer types
13033 <pre>
13035 </pre>
13036 <li> maximum values of exact-width unsigned integer types
13037 <pre>
13039 </pre>
13040 </ul>
13042 <h5><a name="7.18.2.2" href="#7.18.2.2">7.18.2.2 Limits of minimum-width integer types</a></h5>
13044 <ul>
13045 <li> minimum values of minimum-width signed integer types
13046 <pre>
13048 </pre>
13049 <li> maximum values of minimum-width signed integer types
13050 <pre>
13052 </pre>
13053 <li> maximum values of minimum-width unsigned integer types
13054 <pre>
13056 </pre>
13057 </ul>
13059 <h5><a name="7.18.2.3" href="#7.18.2.3">7.18.2.3 Limits of fastest minimum-width integer types</a></h5>
13061 <ul>
13062 <li> minimum values of fastest minimum-width signed integer types
13063 <pre>
13065 </pre>
13066 <li> maximum values of fastest minimum-width signed integer types
13067 <pre>
13069 </pre>
13070 <li> maximum values of fastest minimum-width unsigned integer types
13071 <pre>
13073 </pre>
13074 </ul>
13076 <h5><a name="7.18.2.4" href="#7.18.2.4">7.18.2.4 Limits of integer types capable of holding object pointers</a></h5>
13078 <ul>
13079 <li> minimum value of pointer-holding signed integer type
13080 <pre>
13082 </pre>
13083 <li> maximum value of pointer-holding signed integer type
13084 <!--page 271 -->
13085 <pre>
13087 </pre>
13088 <li> maximum value of pointer-holding unsigned integer type
13089 <pre>
13091 </pre>
13092 </ul>
13094 <h5><a name="7.18.2.5" href="#7.18.2.5">7.18.2.5 Limits of greatest-width integer types</a></h5>
13096 <ul>
13097 <li> minimum value of greatest-width signed integer type
13098 <pre>
13100 </pre>
13101 <li> maximum value of greatest-width signed integer type
13102 <pre>
13104 </pre>
13105 <li> maximum value of greatest-width unsigned integer type
13106 <pre>
13108 </pre>
13109 </ul>
13113 The following object-like macros<sup><a href="#note227"><b>227)</b></a></sup> specify the minimum and maximum limits of
13114 integer types corresponding to types defined in other standard headers.
13116 Each instance of these macros shall be replaced by a constant expression suitable for use
13117 in #if preprocessing directives, and this expression shall have the same type as would an
13118 expression that is an object of the corresponding type converted according to the integer
13119 promotions. Its implementation-defined value shall be equal to or greater in magnitude
13120 (absolute value) than the corresponding value given below, with the same sign. An
13121 implementation shall define only the macros corresponding to those typedef names it
13123 <ul>
13124 <li> limits of ptrdiff_t
13125 <pre>
13126 PTRDIFF_MIN -65535
13127 PTRDIFF_MAX +65535
13128 </pre>
13129 <li> limits of sig_atomic_t
13130 <pre>
13131 SIG_ATOMIC_MIN see below
13132 SIG_ATOMIC_MAX see below
13133 </pre>
13134 <li> limit of size_t
13135 <pre>
13136 SIZE_MAX 65535
13137 </pre>
13138 <li> limits of wchar_t
13140 <!--page 272 -->
13141 <pre>
13142 WCHAR_MIN see below
13143 WCHAR_MAX see below
13144 </pre>
13145 <li> limits of wint_t
13146 <pre>
13147 WINT_MIN see below
13148 WINT_MAX see below
13149 </pre>
13150 </ul>
13152 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
13153 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
13154 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
13155 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
13156 SIG_ATOMIC_MAX shall be no less than 255.
13158 If wchar_t (see <a href="#7.17">7.17</a>) is defined as a signed integer type, the value of WCHAR_MIN
13160 otherwise, wchar_t is defined as an unsigned integer type, and the value of
13161 WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.<sup><a href="#note229"><b>229)</b></a></sup>
13163 If wint_t (see <a href="#7.24">7.24</a>) is defined as a signed integer type, the value of WINT_MIN shall
13165 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
13169 <p><small><a name="note227" href="#note227">227)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
13171 </small>
13172 <p><small><a name="note228" href="#note228">228)</a> A freestanding implementation need not provide all of these types.
13173 </small>
13174 <p><small><a name="note229" href="#note229">229)</a> The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
13175 character set.
13176 </small>
13180 The following function-like macros<sup><a href="#note230"><b>230)</b></a></sup> expand to integer constants suitable for
13181 initializing objects that have integer types corresponding to types defined in
13182 <a href="#7.18"><stdint.h></a>. Each macro name corresponds to a similar type name in <a href="#7.18.1.2">7.18.1.2</a> or
13185 The argument in any instance of these macros shall be an unsuffixed integer constant (as
13186 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.
13188 Each invocation of one of these macros shall expand to an integer constant expression
13189 suitable for use in #if preprocessing directives. The type of the expression shall have
13190 the same type as would an expression of the corresponding type converted according to
13191 the integer promotions. The value of the expression shall be that of the argument.
13196 <!--page 273 -->
13199 <p><small><a name="note230" href="#note230">230)</a> C++ implementations should define these macros only when __STDC_CONSTANT_MACROS is
13201 </small>
13203 <h5><a name="7.18.4.1" href="#7.18.4.1">7.18.4.1 Macros for minimum-width integer constants</a></h5>
13205 The macro INTN_C(value) shall expand to an integer constant expression
13206 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
13207 to an integer constant expression corresponding to the type uint_leastN_t. For
13208 example, if uint_least64_t is a name for the type unsigned long long int,
13211 <h5><a name="7.18.4.2" href="#7.18.4.2">7.18.4.2 Macros for greatest-width integer constants</a></h5>
13213 The following macro expands to an integer constant expression having the value specified
13214 by its argument and the type intmax_t:
13215 <pre>
13216 INTMAX_C(value)
13217 </pre>
13218 The following macro expands to an integer constant expression having the value specified
13219 by its argument and the type uintmax_t:
13220 <!--page 274 -->
13221 <pre>
13222 UINTMAX_C(value)
13223 </pre>
13229 The header <a href="#7.19"><stdio.h></a> declares three types, several macros, and many functions for
13230 performing input and output.
13233 <pre>
13234 FILE
13235 </pre>
13236 which is an object type capable of recording all the information needed to control a
13237 stream, including its file position indicator, a pointer to its associated buffer (if any), an
13238 error indicator that records whether a read/write error has occurred, and an end-of-file
13239 indicator that records whether the end of the file has been reached; and
13240 <pre>
13241 fpos_t
13242 </pre>
13243 which is an object type other than an array type capable of recording all the information
13244 needed to specify uniquely every position within a file.
13247 <pre>
13248 _IOFBF
13249 _IOLBF
13250 _IONBF
13251 </pre>
13252 which expand to integer constant expressions with distinct values, suitable for use as the
13253 third argument to the setvbuf function;
13254 <pre>
13255 BUFSIZ
13256 </pre>
13257 which expands to an integer constant expression that is the size of the buffer used by the
13258 setbuf function;
13259 <pre>
13260 EOF
13261 </pre>
13262 which expands to an integer constant expression, with type int and a negative value, that
13263 is returned by several functions to indicate end-of-file, that is, no more input from a
13264 stream;
13265 <pre>
13266 FOPEN_MAX
13267 </pre>
13268 which expands to an integer constant expression that is the minimum number of files that
13269 the implementation guarantees can be open simultaneously;
13270 <pre>
13271 FILENAME_MAX
13272 </pre>
13273 which expands to an integer constant expression that is the size needed for an array of
13274 char large enough to hold the longest file name string that the implementation
13275 <!--page 275 -->
13277 <pre>
13278 L_tmpnam
13279 </pre>
13280 which expands to an integer constant expression that is the size needed for an array of
13281 char large enough to hold a temporary file name string generated by the tmpnam
13282 function;
13283 <pre>
13284 SEEK_CUR
13285 SEEK_END
13286 SEEK_SET
13287 </pre>
13288 which expand to integer constant expressions with distinct values, suitable for use as the
13289 third argument to the fseek function;
13290 <pre>
13291 TMP_MAX
13292 </pre>
13293 which expands to an integer constant expression that is the maximum number of unique
13294 file names that can be generated by the tmpnam function;
13295 <pre>
13296 stderr
13297 stdin
13298 stdout
13299 </pre>
13300 which are expressions of type ''pointer to FILE'' that point to the FILE objects
13301 associated, respectively, with the standard error, input, and output streams.
13303 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide character input
13304 and output. The wide character input/output functions described in that subclause
13305 provide operations analogous to most of those described here, except that the
13306 fundamental units internal to the program are wide characters. The external
13307 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
13310 The input/output functions are given the following collective terms:
13311 <ul>
13312 <li> The wide character input functions -- those functions described in <a href="#7.24">7.24</a> that perform
13313 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
13314 fwscanf, wscanf, vfwscanf, and vwscanf.
13315 <li> The wide character output functions -- those functions described in <a href="#7.24">7.24</a> that perform
13316 output from wide characters and wide strings: fputwc, fputws, putwc,
13317 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
13320 <!--page 276 -->
13321 <li> The wide character input/output functions -- the union of the ungetwc function, the
13322 wide character input functions, and the wide character output functions.
13323 <li> The byte input/output functions -- those functions described in this subclause that
13324 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
13325 fscanf, fwrite, getc, getchar, gets, printf, putc, putchar, puts,
13326 scanf, ungetc, vfprintf, vfscanf, vprintf, and vscanf.
13327 </ul>
13328 <p><b> Forward references</b>: files (<a href="#7.19.3">7.19.3</a>), the fseek function (<a href="#7.19.9.2">7.19.9.2</a>), streams (<a href="#7.19.2">7.19.2</a>), the
13329 tmpnam function (<a href="#7.19.4.4">7.19.4.4</a>), <a href="#7.24"><wchar.h></a> (<a href="#7.24">7.24</a>).
13332 <p><small><a name="note231" href="#note231">231)</a> If the implementation imposes no practical limit on the length of file name strings, the value of
13333 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
13334 string. Of course, file name string contents are subject to other system-specific constraints; therefore
13335 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
13336 </small>
13340 Input and output, whether to or from physical devices such as terminals and tape drives,
13341 or whether to or from files supported on structured storage devices, are mapped into
13342 logical data streams, whose properties are more uniform than their various inputs and
13343 outputs. Two forms of mapping are supported, for text streams and for binary
13346 A text stream is an ordered sequence of characters composed into lines, each line
13347 consisting of zero or more characters plus a terminating new-line character. Whether the
13348 last line requires a terminating new-line character is implementation-defined. Characters
13349 may have to be added, altered, or deleted on input and output to conform to differing
13350 conventions for representing text in the host environment. Thus, there need not be a one-
13351 to-one correspondence between the characters in a stream and those in the external
13352 representation. Data read in from a text stream will necessarily compare equal to the data
13353 that were earlier written out to that stream only if: the data consist only of printing
13354 characters and the control characters horizontal tab and new-line; no new-line character is
13355 immediately preceded by space characters; and the last character is a new-line character.
13356 Whether space characters that are written out immediately before a new-line character
13357 appear when read in is implementation-defined.
13359 A binary stream is an ordered sequence of characters that can transparently record
13360 internal data. Data read in from a binary stream shall compare equal to the data that were
13361 earlier written out to that stream, under the same implementation. Such a stream may,
13362 however, have an implementation-defined number of null characters appended to the end
13363 of the stream.
13365 Each stream has an orientation. After a stream is associated with an external file, but
13366 before any operations are performed on it, the stream is without orientation. Once a wide
13367 character input/output function has been applied to a stream without orientation, the
13370 <!--page 277 -->
13371 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
13372 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
13373 Only a call to the freopen function or the fwide function can otherwise alter the
13374 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note233"><b>233)</b></a></sup>
13376 Byte input/output functions shall not be applied to a wide-oriented stream and wide
13377 character input/output functions shall not be applied to a byte-oriented stream. The
13378 remaining stream operations do not affect, and are not affected by, a stream's orientation,
13379 except for the following additional restrictions:
13380 <ul>
13381 <li> Binary wide-oriented streams have the file-positioning restrictions ascribed to both
13382 text and binary streams.
13383 <li> For wide-oriented streams, after a successful call to a file-positioning function that
13384 leaves the file position indicator prior to the end-of-file, a wide character output
13385 function can overwrite a partial multibyte character; any file contents beyond the
13386 byte(s) written are henceforth indeterminate.
13387 </ul>
13389 Each wide-oriented stream has an associated mbstate_t object that stores the current
13390 parse state of the stream. A successful call to fgetpos stores a representation of the
13391 value of this mbstate_t object as part of the value of the fpos_t object. A later
13392 successful call to fsetpos using the same stored fpos_t value restores the value of
13393 the associated mbstate_t object as well as the position within the controlled stream.
13396 An implementation shall support text files with lines containing at least 254 characters,
13397 including the terminating new-line character. The value of the macro BUFSIZ shall be at
13398 least 256.
13399 <p><b> Forward references</b>: the freopen function (<a href="#7.19.5.4">7.19.5.4</a>), the fwide function (<a href="#7.24.3.5">7.24.3.5</a>),
13400 mbstate_t (<a href="#7.25.1">7.25.1</a>), the fgetpos function (<a href="#7.19.9.1">7.19.9.1</a>), the fsetpos function
13406 <!--page 278 -->
13409 <p><small><a name="note232" href="#note232">232)</a> An implementation need not distinguish between text streams and binary streams. In such an
13410 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
13411 line.
13412 </small>
13413 <p><small><a name="note233" href="#note233">233)</a> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
13414 </small>
13418 A stream is associated with an external file (which may be a physical device) by opening
13419 a file, which may involve creating a new file. Creating an existing file causes its former
13420 contents to be discarded, if necessary. If a file can support positioning requests (such as a
13421 disk file, as opposed to a terminal), then a file position indicator associated with the
13422 stream is positioned at the start (character number zero) of the file, unless the file is
13423 opened with append mode in which case it is implementation-defined whether the file
13424 position indicator is initially positioned at the beginning or the end of the file. The file
13425 position indicator is maintained by subsequent reads, writes, and positioning requests, to
13426 facilitate an orderly progression through the file.
13428 Binary files are not truncated, except as defined in <a href="#7.19.5.3">7.19.5.3</a>. Whether a write on a text
13429 stream causes the associated file to be truncated beyond that point is implementation-
13430 defined.
13432 When a stream is unbuffered, characters are intended to appear from the source or at the
13433 destination as soon as possible. Otherwise characters may be accumulated and
13434 transmitted to or from the host environment as a block. When a stream is fully buffered,
13435 characters are intended to be transmitted to or from the host environment as a block when
13436 a buffer is filled. When a stream is line buffered, characters are intended to be
13437 transmitted to or from the host environment as a block when a new-line character is
13438 encountered. Furthermore, characters are intended to be transmitted as a block to the host
13439 environment when a buffer is filled, when input is requested on an unbuffered stream, or
13440 when input is requested on a line buffered stream that requires the transmission of
13441 characters from the host environment. Support for these characteristics is
13442 implementation-defined, and may be affected via the setbuf and setvbuf functions.
13444 A file may be disassociated from a controlling stream by closing the file. Output streams
13445 are flushed (any unwritten buffer contents are transmitted to the host environment) before
13446 the stream is disassociated from the file. The value of a pointer to a FILE object is
13447 indeterminate after the associated file is closed (including the standard text streams).
13448 Whether a file of zero length (on which no characters have been written by an output
13449 stream) actually exists is implementation-defined.
13451 The file may be subsequently reopened, by the same or another program execution, and
13452 its contents reclaimed or modified (if it can be repositioned at its start). If the main
13453 function returns to its original caller, or if the exit function is called, all open files are
13454 closed (hence all output streams are flushed) before program termination. Other paths to
13455 program termination, such as calling the abort function, need not close all files
13456 properly.
13458 The address of the FILE object used to control a stream may be significant; a copy of a
13459 FILE object need not serve in place of the original.
13460 <!--page 279 -->
13462 At program startup, three text streams are predefined and need not be opened explicitly
13463 -- standard input (for reading conventional input), standard output (for writing
13464 conventional output), and standard error (for writing diagnostic output). As initially
13465 opened, the standard error stream is not fully buffered; the standard input and standard
13466 output streams are fully buffered if and only if the stream can be determined not to refer
13467 to an interactive device.
13469 Functions that open additional (nontemporary) files require a file name, which is a string.
13470 The rules for composing valid file names are implementation-defined. Whether the same
13471 file can be simultaneously open multiple times is also implementation-defined.
13473 Although both text and binary wide-oriented streams are conceptually sequences of wide
13474 characters, the external file associated with a wide-oriented stream is a sequence of
13475 multibyte characters, generalized as follows:
13476 <ul>
13477 <li> Multibyte encodings within files may contain embedded null bytes (unlike multibyte
13478 encodings valid for use internal to the program).
13479 <li> A file need not begin nor end in the initial shift state.<sup><a href="#note234"><b>234)</b></a></sup>
13480 </ul>
13482 Moreover, the encodings used for multibyte characters may differ among files. Both the
13483 nature and choice of such encodings are implementation-defined.
13485 The wide character input functions read multibyte characters from the stream and convert
13486 them to wide characters as if they were read by successive calls to the fgetwc function.
13487 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
13488 described by the stream's own mbstate_t object. The byte input functions read
13489 characters from the stream as if by successive calls to the fgetc function.
13491 The wide character output functions convert wide characters to multibyte characters and
13492 write them to the stream as if they were written by successive calls to the fputwc
13493 function. Each conversion occurs as if by a call to the wcrtomb function, with the
13494 conversion state described by the stream's own mbstate_t object. The byte output
13495 functions write characters to the stream as if by successive calls to the fputc function.
13497 In some cases, some of the byte input/output functions also perform conversions between
13498 multibyte characters and wide characters. These conversions also occur as if by calls to
13499 the mbrtowc and wcrtomb functions.
13501 An encoding error occurs if the character sequence presented to the underlying
13502 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
13503 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
13506 <!--page 280 -->
13507 multibyte character. The wide character input/output functions and the byte input/output
13508 functions store the value of the macro EILSEQ in errno if and only if an encoding error
13509 occurs.
13512 The value of FOPEN_MAX shall be at least eight, including the three standard text
13513 streams.
13514 <p><b> Forward references</b>: the exit function (<a href="#7.20.4.3">7.20.4.3</a>), the fgetc function (<a href="#7.19.7.1">7.19.7.1</a>), the
13515 fopen function (<a href="#7.19.5.3">7.19.5.3</a>), the fputc function (<a href="#7.19.7.3">7.19.7.3</a>), the setbuf function
13516 (<a href="#7.19.5.5">7.19.5.5</a>), the setvbuf function (<a href="#7.19.5.6">7.19.5.6</a>), the fgetwc function (<a href="#7.24.3.1">7.24.3.1</a>), the
13517 fputwc function (<a href="#7.24.3.3">7.24.3.3</a>), conversion state (<a href="#7.24.6">7.24.6</a>), the mbrtowc function
13518 (<a href="#7.24.6.3.2">7.24.6.3.2</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
13521 <p><small><a name="note234" href="#note234">234)</a> Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
13522 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
13523 with state-dependent encoding that does not assuredly end in the initial shift state.
13524 </small>
13531 <pre>
13533 int remove(const char *filename);
13534 </pre>
13537 The remove function causes the file whose name is the string pointed to by filename
13538 to be no longer accessible by that name. A subsequent attempt to open that file using that
13539 name will fail, unless it is created anew. If the file is open, the behavior of the remove
13540 function is implementation-defined.
13543 The remove function returns zero if the operation succeeds, nonzero if it fails.
13548 <pre>
13550 int rename(const char *old, const char *new);
13551 </pre>
13554 The rename function causes the file whose name is the string pointed to by old to be
13555 henceforth known by the name given by the string pointed to by new. The file named
13556 old is no longer accessible by that name. If a file named by the string pointed to by new
13557 exists prior to the call to the rename function, the behavior is implementation-defined.
13558 <!--page 281 -->
13561 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note235"><b>235)</b></a></sup> in
13562 which case if the file existed previously it is still known by its original name.
13565 <p><small><a name="note235" href="#note235">235)</a> Among the reasons the implementation may cause the rename function to fail are that the file is open
13566 or that it is necessary to copy its contents to effectuate its renaming.
13567 </small>
13572 <pre>
13574 FILE *tmpfile(void);
13575 </pre>
13578 The tmpfile function creates a temporary binary file that is different from any other
13579 existing file and that will automatically be removed when it is closed or at program
13580 termination. If the program terminates abnormally, whether an open temporary file is
13581 removed is implementation-defined. The file is opened for update with "wb+" mode.
13584 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
13585 program (this limit may be shared with tmpnam) and there should be no limit on the
13586 number simultaneously open other than this limit and any limit on the number of open
13587 files (FOPEN_MAX).
13590 The tmpfile function returns a pointer to the stream of the file that it created. If the file
13591 cannot be created, the tmpfile function returns a null pointer.
13597 <pre>
13599 char *tmpnam(char *s);
13600 </pre>
13603 The tmpnam function generates a string that is a valid file name and that is not the same
13604 as the name of an existing file.<sup><a href="#note236"><b>236)</b></a></sup> The function is potentially capable of generating
13607 <!--page 282 -->
13608 TMP_MAX different strings, but any or all of them may already be in use by existing files
13609 and thus not be suitable return values.
13611 The tmpnam function generates a different string each time it is called.
13613 The implementation shall behave as if no library function calls the tmpnam function.
13616 If no suitable string can be generated, the tmpnam function returns a null pointer.
13617 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
13618 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
13619 function may modify the same object). If the argument is not a null pointer, it is assumed
13620 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
13621 in that array and returns the argument as its value.
13624 The value of the macro TMP_MAX shall be at least 25.
13627 <p><small><a name="note236" href="#note236">236)</a> Files created using strings generated by the tmpnam function are temporary only in the sense that
13628 their names should not collide with those generated by conventional naming rules for the
13629 implementation. It is still necessary to use the remove function to remove such files when their use
13630 is ended, and before program termination.
13631 </small>
13638 <pre>
13640 int fclose(FILE *stream);
13641 </pre>
13644 A successful call to the fclose function causes the stream pointed to by stream to be
13645 flushed and the associated file to be closed. Any unwritten buffered data for the stream
13646 are delivered to the host environment to be written to the file; any unread buffered data
13647 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
13648 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
13649 (and deallocated if it was automatically allocated).
13652 The fclose function returns zero if the stream was successfully closed, or EOF if any
13653 errors were detected.
13658 <!--page 283 -->
13659 <pre>
13661 int fflush(FILE *stream);
13662 </pre>
13665 If stream points to an output stream or an update stream in which the most recent
13666 operation was not input, the fflush function causes any unwritten data for that stream
13667 to be delivered to the host environment to be written to the file; otherwise, the behavior is
13668 undefined.
13670 If stream is a null pointer, the fflush function performs this flushing action on all
13671 streams for which the behavior is defined above.
13674 The fflush function sets the error indicator for the stream and returns EOF if a write
13675 error occurs, otherwise it returns zero.
13681 <pre>
13683 FILE *fopen(const char * restrict filename,
13684 const char * restrict mode);
13685 </pre>
13688 The fopen function opens the file whose name is the string pointed to by filename,
13689 and associates a stream with it.
13691 The argument mode points to a string. If the string is one of the following, the file is
13692 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note237"><b>237)</b></a></sup>
13693 <dl>
13704 <!--page 284 -->
13708 </dl>
13710 Opening a file with read mode ('r' as the first character in the mode argument) fails if
13711 the file does not exist or cannot be read.
13713 Opening a file with append mode ('a' as the first character in the mode argument)
13714 causes all subsequent writes to the file to be forced to the then current end-of-file,
13715 regardless of intervening calls to the fseek function. In some implementations, opening
13716 a binary file with append mode ('b' as the second or third character in the above list of
13717 mode argument values) may initially position the file position indicator for the stream
13718 beyond the last data written, because of null character padding.
13720 When a file is opened with update mode ('+' as the second or third character in the
13721 above list of mode argument values), both input and output may be performed on the
13722 associated stream. However, output shall not be directly followed by input without an
13723 intervening call to the fflush function or to a file positioning function (fseek,
13724 fsetpos, or rewind), and input shall not be directly followed by output without an
13725 intervening call to a file positioning function, unless the input operation encounters end-
13726 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
13727 binary stream in some implementations.
13729 When opened, a stream is fully buffered if and only if it can be determined not to refer to
13730 an interactive device. The error and end-of-file indicators for the stream are cleared.
13733 The fopen function returns a pointer to the object controlling the stream. If the open
13734 operation fails, fopen returns a null pointer.
13738 <p><small><a name="note237" href="#note237">237)</a> If the string begins with one of the above sequences, the implementation might choose to ignore the
13739 remaining characters, or it might use them to select different kinds of a file (some of which might not
13741 </small>
13746 <pre>
13748 FILE *freopen(const char * restrict filename,
13749 const char * restrict mode,
13750 FILE * restrict stream);
13751 </pre>
13754 The freopen function opens the file whose name is the string pointed to by filename
13755 and associates the stream pointed to by stream with it. The mode argument is used just
13756 <!--page 285 -->
13759 If filename is a null pointer, the freopen function attempts to change the mode of
13760 the stream to that specified by mode, as if the name of the file currently associated with
13761 the stream had been used. It is implementation-defined which changes of mode are
13762 permitted (if any), and under what circumstances.
13764 The freopen function first attempts to close any file that is associated with the specified
13765 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
13766 stream are cleared.
13769 The freopen function returns a null pointer if the open operation fails. Otherwise,
13770 freopen returns the value of stream.
13773 <p><small><a name="note238" href="#note238">238)</a> The primary use of the freopen function is to change the file associated with a standard text stream
13774 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
13775 returned by the fopen function may be assigned.
13776 </small>
13781 <pre>
13783 void setbuf(FILE * restrict stream,
13784 char * restrict buf);
13785 </pre>
13788 Except that it returns no value, the setbuf function is equivalent to the setvbuf
13789 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
13790 is a null pointer), with the value _IONBF for mode.
13793 The setbuf function returns no value.
13799 <pre>
13801 int setvbuf(FILE * restrict stream,
13802 char * restrict buf,
13803 int mode, size_t size);
13804 </pre>
13809 <!--page 286 -->
13812 The setvbuf function may be used only after the stream pointed to by stream has
13813 been associated with an open file and before any other operation (other than an
13814 unsuccessful call to setvbuf) is performed on the stream. The argument mode
13815 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
13816 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
13817 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
13818 used instead of a buffer allocated by the setvbuf function<sup><a href="#note239"><b>239)</b></a></sup> and the argument size
13819 specifies the size of the array; otherwise, size may determine the size of a buffer
13820 allocated by the setvbuf function. The contents of the array at any time are
13821 indeterminate.
13824 The setvbuf function returns zero on success, or nonzero if an invalid value is given
13825 for mode or if the request cannot be honored.
13828 <p><small><a name="note239" href="#note239">239)</a> The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
13829 before a buffer that has automatic storage duration is deallocated upon block exit.
13830 </small>
13834 The formatted input/output functions shall behave as if there is a sequence point after the
13838 <p><small><a name="note240" href="#note240">240)</a> The fprintf functions perform writes to memory for the %n specifier.
13839 </small>
13844 <pre>
13846 int fprintf(FILE * restrict stream,
13847 const char * restrict format, ...);
13848 </pre>
13851 The fprintf function writes output to the stream pointed to by stream, under control
13852 of the string pointed to by format that specifies how subsequent arguments are
13853 converted for output. If there are insufficient arguments for the format, the behavior is
13854 undefined. If the format is exhausted while arguments remain, the excess arguments are
13855 evaluated (as always) but are otherwise ignored. The fprintf function returns when
13856 the end of the format string is encountered.
13858 The format shall be a multibyte character sequence, beginning and ending in its initial
13859 shift state. The format is composed of zero or more directives: ordinary multibyte
13860 characters (not %), which are copied unchanged to the output stream; and conversion
13863 <!--page 287 -->
13864 specifications, each of which results in fetching zero or more subsequent arguments,
13865 converting them, if applicable, according to the corresponding conversion specifier, and
13866 then writing the result to the output stream.
13868 Each conversion specification is introduced by the character %. After the %, the following
13869 appear in sequence:
13870 <ul>
13871 <li> Zero or more flags (in any order) that modify the meaning of the conversion
13872 specification.
13873 <li> An optional minimum field width. If the converted value has fewer characters than the
13874 field width, it is padded with spaces (by default) on the left (or right, if the left
13875 adjustment flag, described later, has been given) to the field width. The field width
13876 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note241"><b>241)</b></a></sup>
13877 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
13878 o, u, x, and X conversions, the number of digits to appear after the decimal-point
13879 character for a, A, e, E, f, and F conversions, the maximum number of significant
13880 digits for the g and G conversions, or the maximum number of bytes to be written for
13881 s conversions. The precision takes the form of a period (.) followed either by an
13882 asterisk * (described later) or by an optional decimal integer; if only the period is
13883 specified, the precision is taken as zero. If a precision appears with any other
13884 conversion specifier, the behavior is undefined.
13885 <li> An optional length modifier that specifies the size of the argument.
13886 <li> A conversion specifier character that specifies the type of conversion to be applied.
13887 </ul>
13889 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
13890 this case, an int argument supplies the field width or precision. The arguments
13891 specifying field width, or precision, or both, shall appear (in that order) before the
13892 argument (if any) to be converted. A negative field width argument is taken as a - flag
13893 followed by a positive field width. A negative precision argument is taken as if the
13894 precision were omitted.
13896 The flag characters and their meanings are:
13897 <dl>
13898 <dt> - <dd> The result of the conversion is left-justified within the field. (It is right-justified if
13899 this flag is not specified.)
13901 begins with a sign only when a negative value is converted if this flag is not
13903 <!--page 288 -->
13905 <dt> space<dd> If the first character of a signed conversion is not a sign, or if a signed conversion
13906 results in no characters, a space is prefixed to the result. If the space and + flags
13907 both appear, the space flag is ignored.
13908 <dt> # <dd> The result is converted to an ''alternative form''. For o conversion, it increases
13909 the precision, if and only if necessary, to force the first digit of the result to be a
13912 and G conversions, the result of converting a floating-point number always
13913 contains a decimal-point character, even if no digits follow it. (Normally, a
13914 decimal-point character appears in the result of these conversions only if a digit
13915 follows it.) For g and G conversions, trailing zeros are not removed from the
13916 result. For other conversions, the behavior is undefined.
13918 (following any indication of sign or base) are used to pad to the field width rather
13919 than performing space padding, except when converting an infinity or NaN. If the
13921 conversions, if a precision is specified, the 0 flag is ignored. For other
13922 conversions, the behavior is undefined.
13923 </dl>
13925 The length modifiers and their meanings are:
13926 <dl>
13928 signed char or unsigned char argument (the argument will have
13929 been promoted according to the integer promotions, but its value shall be
13930 converted to signed char or unsigned char before printing); or that
13931 a following n conversion specifier applies to a pointer to a signed char
13932 argument.
13934 short int or unsigned short int argument (the argument will
13935 have been promoted according to the integer promotions, but its value shall
13936 be converted to short int or unsigned short int before printing);
13937 or that a following n conversion specifier applies to a pointer to a short
13938 int argument.
13939 <dt> l (ell) <dd> Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13940 long int or unsigned long int argument; that a following n
13941 conversion specifier applies to a pointer to a long int argument; that a
13942 <!--page 289 -->
13943 following c conversion specifier applies to a wint_t argument; that a
13944 following s conversion specifier applies to a pointer to a wchar_t
13945 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
13946 specifier.
13947 <dt> ll (ell-ell)<dd> Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13948 long long int or unsigned long long int argument; or that a
13949 following n conversion specifier applies to a pointer to a long long int
13950 argument.
13952 an intmax_t or uintmax_t argument; or that a following n conversion
13953 specifier applies to a pointer to an intmax_t argument.
13955 size_t or the corresponding signed integer type argument; or that a
13956 following n conversion specifier applies to a pointer to a signed integer type
13957 corresponding to size_t argument.
13959 ptrdiff_t or the corresponding unsigned integer type argument; or that a
13960 following n conversion specifier applies to a pointer to a ptrdiff_t
13961 argument.
13963 applies to a long double argument.
13964 </dl>
13965 If a length modifier appears with any conversion specifier other than as specified above,
13966 the behavior is undefined.
13968 The conversion specifiers and their meanings are:
13969 <dl>
13971 precision specifies the minimum number of digits to appear; if the value
13972 being converted can be represented in fewer digits, it is expanded with
13973 leading zeros. The default precision is 1. The result of converting a zero
13974 value with a precision of zero is no characters.
13976 <!--page 290 -->
13977 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
13978 letters abcdef are used for x conversion and the letters ABCDEF for X
13979 conversion. The precision specifies the minimum number of digits to appear;
13980 if the value being converted can be represented in fewer digits, it is expanded
13981 with leading zeros. The default precision is 1. The result of converting a
13982 zero value with a precision of zero is no characters.
13984 decimal notation in the style [-]ddd.ddd, where the number of digits after
13985 the decimal-point character is equal to the precision specification. If the
13986 precision is missing, it is taken as 6; if the precision is zero and the # flag is
13987 not specified, no decimal-point character appears. If a decimal-point
13988 character appears, at least one digit appears before it. The value is rounded to
13989 the appropriate number of digits.
13990 A double argument representing an infinity is converted in one of the styles
13991 [-]inf or [-]infinity -- which style is implementation-defined. A
13992 double argument representing a NaN is converted in one of the styles
13993 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
13994 any n-char-sequence, is implementation-defined. The F conversion specifier
13995 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
13998 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
13999 argument is nonzero) before the decimal-point character and the number of
14000 digits after it is equal to the precision; if the precision is missing, it is taken as
14001 6; if the precision is zero and the # flag is not specified, no decimal-point
14002 character appears. The value is rounded to the appropriate number of digits.
14003 The E conversion specifier produces a number with E instead of e
14004 introducing the exponent. The exponent always contains at least two digits,
14005 and only as many more digits as necessary to represent the exponent. If the
14006 value is zero, the exponent is zero.
14007 A double argument representing an infinity or NaN is converted in the style
14008 of an f or F conversion specifier.
14010 style f or e (or in style F or E in the case of a G conversion specifier),
14011 depending on the value converted and the precision. Let P equal the
14013 Then, if a conversion with style E would have an exponent of X :
14014 <ul>
14016 P - (X + 1).
14018 </ul>
14019 Finally, unless the # flag is used, any trailing zeros are removed from the
14020 <!--page 291 -->
14021 fractional portion of the result and the decimal-point character is removed if
14022 there is no fractional portion remaining.
14023 A double argument representing an infinity or NaN is converted in the style
14024 of an f or F conversion specifier.
14026 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
14027 nonzero if the argument is a normalized floating-point number and is
14028 otherwise unspecified) before the decimal-point character<sup><a href="#note244"><b>244)</b></a></sup> and the number
14029 of hexadecimal digits after it is equal to the precision; if the precision is
14030 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
14031 an exact representation of the value; if the precision is missing and
14032 FLT_RADIX is not a power of 2, then the precision is sufficient to
14033 distinguish<sup><a href="#note245"><b>245)</b></a></sup> values of type double, except that trailing zeros may be
14034 omitted; if the precision is zero and the # flag is not specified, no decimal-
14035 point character appears. The letters abcdef are used for a conversion and
14036 the letters ABCDEF for A conversion. The A conversion specifier produces a
14037 number with X and P instead of x and p. The exponent always contains at
14038 least one digit, and only as many more digits as necessary to represent the
14039 decimal exponent of 2. If the value is zero, the exponent is zero.
14040 A double argument representing an infinity or NaN is converted in the style
14041 of an f or F conversion specifier.
14043 unsigned char, and the resulting character is written.
14044 If an l length modifier is present, the wint_t argument is converted as if by
14045 an ls conversion specification with no precision and an argument that points
14046 to the initial element of a two-element array of wchar_t, the first element
14047 containing the wint_t argument to the lc conversion specification and the
14048 second a null wide character.
14049 <dt> s <dd> If no l length modifier is present, the argument shall be a pointer to the initial
14050 element of an array of character type.<sup><a href="#note246"><b>246)</b></a></sup> Characters from the array are
14051 <!--page 292 -->
14052 written up to (but not including) the terminating null character. If the
14053 precision is specified, no more than that many bytes are written. If the
14054 precision is not specified or is greater than the size of the array, the array shall
14055 contain a null character.
14056 If an l length modifier is present, the argument shall be a pointer to the initial
14057 element of an array of wchar_t type. Wide characters from the array are
14058 converted to multibyte characters (each as if by a call to the wcrtomb
14059 function, with the conversion state described by an mbstate_t object
14060 initialized to zero before the first wide character is converted) up to and
14061 including a terminating null wide character. The resulting multibyte
14062 characters are written up to (but not including) the terminating null character
14063 (byte). If no precision is specified, the array shall contain a null wide
14064 character. If a precision is specified, no more than that many bytes are
14065 written (including shift sequences, if any), and the array shall contain a null
14066 wide character if, to equal the multibyte character sequence length given by
14067 the precision, the function would need to access a wide character one past the
14068 end of the array. In no case is a partial multibyte character written.<sup><a href="#note247"><b>247)</b></a></sup>
14070 converted to a sequence of printing characters, in an implementation-defined
14071 manner.
14073 number of characters written to the output stream so far by this call to
14074 fprintf. No argument is converted, but one is consumed. If the conversion
14075 specification includes any flags, a field width, or a precision, the behavior is
14076 undefined.
14078 conversion specification shall be %%.
14079 </dl>
14081 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note248"><b>248)</b></a></sup> If any argument is
14082 not the correct type for the corresponding conversion specification, the behavior is
14083 undefined.
14085 In no case does a nonexistent or small field width cause truncation of a field; if the result
14086 of a conversion is wider than the field width, the field is expanded to contain the
14087 conversion result.
14092 <!--page 293 -->
14094 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
14095 to a hexadecimal floating number with the given precision.
14098 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
14099 representable in the given precision, the result should be one of the two adjacent numbers
14100 in hexadecimal floating style with the given precision, with the extra stipulation that the
14101 error should have a correct sign for the current rounding direction.
14103 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
14104 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note249"><b>249)</b></a></sup> If the number of
14105 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
14106 representable with DECIMAL_DIG digits, then the result should be an exact
14107 representation with trailing zeros. Otherwise, the source value is bounded by two
14108 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
14109 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
14110 the error should have a correct sign for the current rounding direction.
14113 The fprintf function returns the number of characters transmitted, or a negative value
14114 if an output or encoding error occurred.
14117 The number of characters that can be produced by any single conversion shall be at least
14118 4095.
14120 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
14121 places:
14122 <pre>
14125 /* ... */
14126 char *weekday, *month; // pointers to strings
14127 int day, hour, min;
14128 fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
14129 weekday, month, day, hour, min);
14131 </pre>
14134 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
14135 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
14136 the first of which is denoted here by a and the second by an uppercase letter.
14141 <!--page 294 -->
14143 Given the following wide string with length seven,
14144 <pre>
14145 static wchar_t wstr[] = L" X Yabc Z W";
14146 </pre>
14147 the seven calls
14148 <pre>
14149 fprintf(stdout, "|1234567890123|\n");
14150 fprintf(stdout, "|%13ls|\n", wstr);
14151 fprintf(stdout, "|%-13.9ls|\n", wstr);
14152 fprintf(stdout, "|%13.10ls|\n", wstr);
14153 fprintf(stdout, "|%13.11ls|\n", wstr);
14156 </pre>
14157 will print the following seven lines:
14158 <pre>
14159 |1234567890123|
14160 | X Yabc Z W|
14161 | X Yabc Z |
14162 | X Yabc Z|
14163 | X Yabc Z W|
14164 | abc Z W|
14165 | Z|
14166 </pre>
14168 <p><b> Forward references</b>: conversion state (<a href="#7.24.6">7.24.6</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
14171 <p><small><a name="note241" href="#note241">241)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
14172 </small>
14173 <p><small><a name="note242" href="#note242">242)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
14174 include a minus sign.
14175 </small>
14176 <p><small><a name="note243" href="#note243">243)</a> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
14177 the # and 0 flag characters have no effect.
14178 </small>
14179 <p><small><a name="note244" href="#note244">244)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
14180 that subsequent digits align to nibble (4-bit) boundaries.
14181 </small>
14182 <p><small><a name="note245" href="#note245">245)</a> The precision p is sufficient to distinguish values of the source type if 16<sup>p-1</sup> > b n where b is
14183 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
14184 might suffice depending on the implementation's scheme for determining the digit to the left of the
14185 decimal-point character.
14186 </small>
14187 <p><small><a name="note246" href="#note246">246)</a> No special provisions are made for multibyte characters.
14188 </small>
14189 <p><small><a name="note247" href="#note247">247)</a> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
14190 </small>
14191 <p><small><a name="note248" href="#note248">248)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
14192 </small>
14193 <p><small><a name="note249" href="#note249">249)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
14194 given format specifier. The number of significant digits is determined by the format specifier, and in
14195 the case of fixed-point conversion by the source value as well.
14196 </small>
14201 <pre>
14203 int fscanf(FILE * restrict stream,
14204 const char * restrict format, ...);
14205 </pre>
14208 The fscanf function reads input from the stream pointed to by stream, under control
14209 of the string pointed to by format that specifies the admissible input sequences and how
14210 they are to be converted for assignment, using subsequent arguments as pointers to the
14211 objects to receive the converted input. If there are insufficient arguments for the format,
14212 the behavior is undefined. If the format is exhausted while arguments remain, the excess
14213 arguments are evaluated (as always) but are otherwise ignored.
14215 The format shall be a multibyte character sequence, beginning and ending in its initial
14216 shift state. The format is composed of zero or more directives: one or more white-space
14217 characters, an ordinary multibyte character (neither % nor a white-space character), or a
14218 conversion specification. Each conversion specification is introduced by the character %.
14219 After the %, the following appear in sequence:
14220 <ul>
14221 <li> An optional assignment-suppressing character *.
14222 <li> An optional decimal integer greater than zero that specifies the maximum field width
14223 (in characters).
14224 <!--page 295 -->
14225 <li> An optional length modifier that specifies the size of the receiving object.
14226 <li> A conversion specifier character that specifies the type of conversion to be applied.
14227 </ul>
14229 The fscanf function executes each directive of the format in turn. If a directive fails, as
14230 detailed below, the function returns. Failures are described as input failures (due to the
14231 occurrence of an encoding error or the unavailability of input characters), or matching
14232 failures (due to inappropriate input).
14234 A directive composed of white-space character(s) is executed by reading input up to the
14235 first non-white-space character (which remains unread), or until no more characters can
14236 be read.
14238 A directive that is an ordinary multibyte character is executed by reading the next
14239 characters of the stream. If any of those characters differ from the ones composing the
14240 directive, the directive fails and the differing and subsequent characters remain unread.
14241 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
14242 read, the directive fails.
14244 A directive that is a conversion specification defines a set of matching input sequences, as
14245 described below for each specifier. A conversion specification is executed in the
14246 following steps:
14248 Input white-space characters (as specified by the isspace function) are skipped, unless
14249 the specification includes a [, c, or n specifier.<sup><a href="#note250"><b>250)</b></a></sup>
14251 An input item is read from the stream, unless the specification includes an n specifier. An
14252 input item is defined as the longest sequence of input characters which does not exceed
14253 any specified field width and which is, or is a prefix of, a matching input sequence.<sup><a href="#note251"><b>251)</b></a></sup>
14254 The first character, if any, after the input item remains unread. If the length of the input
14255 item is zero, the execution of the directive fails; this condition is a matching failure unless
14256 end-of-file, an encoding error, or a read error prevented input from the stream, in which
14257 case it is an input failure.
14259 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
14260 count of input characters) is converted to a type appropriate to the conversion specifier. If
14261 the input item is not a matching sequence, the execution of the directive fails: this
14262 condition is a matching failure. Unless assignment suppression was indicated by a *, the
14263 result of the conversion is placed in the object pointed to by the first argument following
14264 the format argument that has not already received a conversion result. If this object
14265 does not have an appropriate type, or if the result of the conversion cannot be represented
14268 <!--page 296 -->
14269 in the object, the behavior is undefined.
14271 The length modifiers and their meanings are:
14272 <dl>
14274 to an argument with type pointer to signed char or unsigned char.
14276 to an argument with type pointer to short int or unsigned short
14277 int.
14278 <dt> l (ell) <dd> Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
14279 to an argument with type pointer to long int or unsigned long
14280 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
14281 an argument with type pointer to double; or that a following c, s, or [
14282 conversion specifier applies to an argument with type pointer to wchar_t.
14283 <dt> ll (ell-ell)<dd> Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
14284 to an argument with type pointer to long long int or unsigned
14285 long long int.
14287 to an argument with type pointer to intmax_t or uintmax_t.
14289 to an argument with type pointer to size_t or the corresponding signed
14290 integer type.
14292 to an argument with type pointer to ptrdiff_t or the corresponding
14293 unsigned integer type.
14295 applies to an argument with type pointer to long double.
14296 </dl>
14297 If a length modifier appears with any conversion specifier other than as specified above,
14298 the behavior is undefined.
14300 The conversion specifiers and their meanings are:
14301 <dl>
14303 expected for the subject sequence of the strtol function with the value 10
14304 for the base argument. The corresponding argument shall be a pointer to
14305 signed integer.
14307 <!--page 297 -->
14308 for the subject sequence of the strtol function with the value 0 for the
14309 base argument. The corresponding argument shall be a pointer to signed
14310 integer.
14312 expected for the subject sequence of the strtoul function with the value 8
14313 for the base argument. The corresponding argument shall be a pointer to
14314 unsigned integer.
14316 expected for the subject sequence of the strtoul function with the value 10
14317 for the base argument. The corresponding argument shall be a pointer to
14318 unsigned integer.
14320 as expected for the subject sequence of the strtoul function with the value
14321 16 for the base argument. The corresponding argument shall be a pointer to
14322 unsigned integer.
14324 format is the same as expected for the subject sequence of the strtod
14325 function. The corresponding argument shall be a pointer to floating.
14327 width (1 if no field width is present in the directive).<sup><a href="#note252"><b>252)</b></a></sup>
14328 If no l length modifier is present, the corresponding argument shall be a
14329 pointer to the initial element of a character array large enough to accept the
14330 sequence. No null character is added.
14331 If an l length modifier is present, the input shall be a sequence of multibyte
14332 characters that begins in the initial shift state. Each multibyte character in the
14333 sequence is converted to a wide character as if by a call to the mbrtowc
14334 function, with the conversion state described by an mbstate_t object
14335 initialized to zero before the first multibyte character is converted. The
14336 corresponding argument shall be a pointer to the initial element of an array of
14337 wchar_t large enough to accept the resulting sequence of wide characters.
14338 No null wide character is added.
14339 <dt> s <dd> Matches a sequence of non-white-space characters.<sup><a href="#note252"><b>252)</b></a></sup>
14340 If no l length modifier is present, the corresponding argument shall be a
14341 pointer to the initial element of a character array large enough to accept the
14342 sequence and a terminating null character, which will be added automatically.
14343 If an l length modifier is present, the input shall be a sequence of multibyte
14344 <!--page 298 -->
14345 characters that begins in the initial shift state. Each multibyte character is
14346 converted to a wide character as if by a call to the mbrtowc function, with
14347 the conversion state described by an mbstate_t object initialized to zero
14348 before the first multibyte character is converted. The corresponding argument
14349 shall be a pointer to the initial element of an array of wchar_t large enough
14350 to accept the sequence and the terminating null wide character, which will be
14351 added automatically.
14354 If no l length modifier is present, the corresponding argument shall be a
14355 pointer to the initial element of a character array large enough to accept the
14356 sequence and a terminating null character, which will be added automatically.
14357 If an l length modifier is present, the input shall be a sequence of multibyte
14358 characters that begins in the initial shift state. Each multibyte character is
14359 converted to a wide character as if by a call to the mbrtowc function, with
14360 the conversion state described by an mbstate_t object initialized to zero
14361 before the first multibyte character is converted. The corresponding argument
14362 shall be a pointer to the initial element of an array of wchar_t large enough
14363 to accept the sequence and the terminating null wide character, which will be
14364 added automatically.
14365 The conversion specifier includes all subsequent characters in the format
14366 string, up to and including the matching right bracket (]). The characters
14367 between the brackets (the scanlist) compose the scanset, unless the character
14368 after the left bracket is a circumflex (^), in which case the scanset contains all
14369 characters that do not appear in the scanlist between the circumflex and the
14370 right bracket. If the conversion specifier begins with [] or [^], the right
14371 bracket character is in the scanlist and the next following right bracket
14372 character is the matching right bracket that ends the specification; otherwise
14373 the first following right bracket character is the one that ends the
14374 specification. If a - character is in the scanlist and is not the first, nor the
14375 second where the first character is a ^, nor the last character, the behavior is
14376 implementation-defined.
14378 <!--page 299 -->
14379 same as the set of sequences that may be produced by the %p conversion of
14380 the fprintf function. The corresponding argument shall be a pointer to a
14381 pointer to void. The input item is converted to a pointer value in an
14382 implementation-defined manner. If the input item is a value converted earlier
14383 during the same program execution, the pointer that results shall compare
14384 equal to that value; otherwise the behavior of the %p conversion is undefined.
14386 signed integer into which is to be written the number of characters read from
14387 the input stream so far by this call to the fscanf function. Execution of a
14388 %n directive does not increment the assignment count returned at the
14389 completion of execution of the fscanf function. No argument is converted,
14390 but one is consumed. If the conversion specification includes an assignment-
14391 suppressing character or a field width, the behavior is undefined.
14393 complete conversion specification shall be %%.
14394 </dl>
14396 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note253"><b>253)</b></a></sup>
14398 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
14399 respectively, a, e, f, g, and x.
14401 Trailing white space (including new-line characters) is left unread unless matched by a
14402 directive. The success of literal matches and suppressed assignments is not directly
14403 determinable other than via the %n directive.
14406 The fscanf function returns the value of the macro EOF if an input failure occurs
14407 before any conversion. Otherwise, the function returns the number of input items
14408 assigned, which can be fewer than provided for, or even zero, in the event of an early
14409 matching failure.
14411 EXAMPLE 1 The call:
14412 <pre>
14414 /* ... */
14415 int n, i; float x; char name[50];
14417 </pre>
14418 with the input line:
14419 <pre>
14420 25 54.32E-1 thompson
14421 </pre>
14422 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
14423 thompson\0.
14426 EXAMPLE 2 The call:
14427 <pre>
14429 /* ... */
14430 int i; float x; char name[50];
14432 </pre>
14433 with input:
14437 <!--page 300 -->
14438 <pre>
14439 56789 0123 56a72
14440 </pre>
14441 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
14445 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
14446 <pre>
14448 /* ... */
14450 do {
14452 fscanf(stdin,"%*[^\n]");
14453 } while (!feof(stdin) && !ferror(stdin));
14454 </pre>
14456 If the stdin stream contains the following lines:
14457 <pre>
14458 2 quarts of oil
14459 -12.8degrees Celsius
14460 lots of luck
14461 10.0LBS of
14462 dirt
14463 100ergs of energy
14464 </pre>
14465 the execution of the above example will be analogous to the following assignments:
14466 <pre>
14468 count = 3;
14473 count = 3;
14475 count = EOF;
14476 </pre>
14479 EXAMPLE 4 In:
14480 <pre>
14482 /* ... */
14483 int d1, d2, n1, n2, i;
14485 </pre>
14486 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
14490 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
14491 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
14492 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
14493 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
14494 entry into the alternate shift state.
14496 After the call:
14497 <!--page 301 -->
14498 <pre>
14500 /* ... */
14501 char str[50];
14502 fscanf(stdin, "a%s", str);
14503 </pre>
14504 with the input line:
14505 <pre>
14506 a(uparrow) X Y(downarrow) bc
14507 </pre>
14508 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
14509 characters, in the more general case) appears to be a single-byte white-space character.
14511 In contrast, after the call:
14512 <pre>
14515 /* ... */
14516 wchar_t wstr[50];
14517 fscanf(stdin, "a%ls", wstr);
14518 </pre>
14519 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
14520 terminating null wide character.
14522 However, the call:
14523 <pre>
14526 /* ... */
14527 wchar_t wstr[50];
14528 fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);
14529 </pre>
14530 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
14531 string.
14533 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
14534 character Y, after the call:
14535 <pre>
14538 /* ... */
14539 wchar_t wstr[50];
14540 fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);
14541 </pre>
14542 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
14543 multibyte character.
14545 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>), the
14546 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.20.1.4">7.20.1.4</a>), conversion state
14548 <!--page 302 -->
14551 <p><small><a name="note250" href="#note250">250)</a> These white-space characters are not counted against a specified field width.
14552 </small>
14553 <p><small><a name="note251" href="#note251">251)</a> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
14554 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
14555 </small>
14556 <p><small><a name="note252" href="#note252">252)</a> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
14557 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
14558 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
14559 </small>
14560 <p><small><a name="note253" href="#note253">253)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
14561 </small>
14566 <pre>
14568 int printf(const char * restrict format, ...);
14569 </pre>
14572 The printf function is equivalent to fprintf with the argument stdout interposed
14573 before the arguments to printf.
14576 The printf function returns the number of characters transmitted, or a negative value if
14577 an output or encoding error occurred.
14582 <pre>
14584 int scanf(const char * restrict format, ...);
14585 </pre>
14588 The scanf function is equivalent to fscanf with the argument stdin interposed
14589 before the arguments to scanf.
14592 The scanf function returns the value of the macro EOF if an input failure occurs before
14593 any conversion. Otherwise, the scanf function returns the number of input items
14594 assigned, which can be fewer than provided for, or even zero, in the event of an early
14595 matching failure.
14600 <pre>
14602 int snprintf(char * restrict s, size_t n,
14603 const char * restrict format, ...);
14604 </pre>
14607 The snprintf function is equivalent to fprintf, except that the output is written into
14608 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
14609 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
14610 discarded rather than being written to the array, and a null character is written at the end
14611 of the characters actually written into the array. If copying takes place between objects
14612 that overlap, the behavior is undefined.
14613 <!--page 303 -->
14616 The snprintf function returns the number of characters that would have been written
14617 had n been sufficiently large, not counting the terminating null character, or a negative
14618 value if an encoding error occurred. Thus, the null-terminated output has been
14619 completely written if and only if the returned value is nonnegative and less than n.
14624 <pre>
14626 int sprintf(char * restrict s,
14627 const char * restrict format, ...);
14628 </pre>
14631 The sprintf function is equivalent to fprintf, except that the output is written into
14632 an array (specified by the argument s) rather than to a stream. A null character is written
14633 at the end of the characters written; it is not counted as part of the returned value. If
14634 copying takes place between objects that overlap, the behavior is undefined.
14637 The sprintf function returns the number of characters written in the array, not
14638 counting the terminating null character, or a negative value if an encoding error occurred.
14643 <pre>
14645 int sscanf(const char * restrict s,
14646 const char * restrict format, ...);
14647 </pre>
14650 The sscanf function is equivalent to fscanf, except that input is obtained from a
14651 string (specified by the argument s) rather than from a stream. Reaching the end of the
14652 string is equivalent to encountering end-of-file for the fscanf function. If copying
14653 takes place between objects that overlap, the behavior is undefined.
14656 The sscanf function returns the value of the macro EOF if an input failure occurs
14657 before any conversion. Otherwise, the sscanf function returns the number of input
14658 items assigned, which can be fewer than provided for, or even zero, in the event of an
14659 early matching failure.
14660 <!--page 304 -->
14665 <pre>
14668 int vfprintf(FILE * restrict stream,
14669 const char * restrict format,
14670 va_list arg);
14671 </pre>
14674 The vfprintf function is equivalent to fprintf, with the variable argument list
14675 replaced by arg, which shall have been initialized by the va_start macro (and
14676 possibly subsequent va_arg calls). The vfprintf function does not invoke the
14680 The vfprintf function returns the number of characters transmitted, or a negative
14681 value if an output or encoding error occurred.
14683 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
14684 <pre>
14687 void error(char *function_name, char *format, ...)
14688 {
14689 va_list args;
14690 va_start(args, format);
14691 // print out name of function causing error
14692 fprintf(stderr, "ERROR in %s: ", function_name);
14693 // print out remainder of message
14694 vfprintf(stderr, format, args);
14695 va_end(args);
14696 }
14697 </pre>
14702 <!--page 305 -->
14705 <p><small><a name="note254" href="#note254">254)</a> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
14706 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
14707 </small>
14712 <pre>
14715 int vfscanf(FILE * restrict stream,
14716 const char * restrict format,
14717 va_list arg);
14718 </pre>
14721 The vfscanf function is equivalent to fscanf, with the variable argument list
14722 replaced by arg, which shall have been initialized by the va_start macro (and
14723 possibly subsequent va_arg calls). The vfscanf function does not invoke the
14727 The vfscanf function returns the value of the macro EOF if an input failure occurs
14728 before any conversion. Otherwise, the vfscanf function returns the number of input
14729 items assigned, which can be fewer than provided for, or even zero, in the event of an
14730 early matching failure.
14735 <pre>
14738 int vprintf(const char * restrict format,
14739 va_list arg);
14740 </pre>
14743 The vprintf function is equivalent to printf, with the variable argument list
14744 replaced by arg, which shall have been initialized by the va_start macro (and
14745 possibly subsequent va_arg calls). The vprintf function does not invoke the
14749 The vprintf function returns the number of characters transmitted, or a negative value
14750 if an output or encoding error occurred.
14751 <!--page 306 -->
14756 <pre>
14759 int vscanf(const char * restrict format,
14760 va_list arg);
14761 </pre>
14764 The vscanf function is equivalent to scanf, with the variable argument list replaced
14765 by arg, which shall have been initialized by the va_start macro (and possibly
14766 subsequent va_arg calls). The vscanf function does not invoke the va_end
14770 The vscanf function returns the value of the macro EOF if an input failure occurs
14771 before any conversion. Otherwise, the vscanf function returns the number of input
14772 items assigned, which can be fewer than provided for, or even zero, in the event of an
14773 early matching failure.
14778 <pre>
14781 int vsnprintf(char * restrict s, size_t n,
14782 const char * restrict format,
14783 va_list arg);
14784 </pre>
14787 The vsnprintf function is equivalent to snprintf, with the variable argument list
14788 replaced by arg, which shall have been initialized by the va_start macro (and
14789 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
14790 va_end macro.<sup><a href="#note254"><b>254)</b></a></sup> If copying takes place between objects that overlap, the behavior is
14791 undefined.
14794 The vsnprintf function returns the number of characters that would have been written
14795 had n been sufficiently large, not counting the terminating null character, or a negative
14796 value if an encoding error occurred. Thus, the null-terminated output has been
14797 completely written if and only if the returned value is nonnegative and less than n.
14798 <!--page 307 -->
14803 <pre>
14806 int vsprintf(char * restrict s,
14807 const char * restrict format,
14808 va_list arg);
14809 </pre>
14812 The vsprintf function is equivalent to sprintf, with the variable argument list
14813 replaced by arg, which shall have been initialized by the va_start macro (and
14814 possibly subsequent va_arg calls). The vsprintf function does not invoke the
14815 va_end macro.<sup><a href="#note254"><b>254)</b></a></sup> If copying takes place between objects that overlap, the behavior is
14816 undefined.
14819 The vsprintf function returns the number of characters written in the array, not
14820 counting the terminating null character, or a negative value if an encoding error occurred.
14825 <pre>
14828 int vsscanf(const char * restrict s,
14829 const char * restrict format,
14830 va_list arg);
14831 </pre>
14834 The vsscanf function is equivalent to sscanf, with the variable argument list
14835 replaced by arg, which shall have been initialized by the va_start macro (and
14836 possibly subsequent va_arg calls). The vsscanf function does not invoke the
14840 The vsscanf function returns the value of the macro EOF if an input failure occurs
14841 before any conversion. Otherwise, the vsscanf function returns the number of input
14842 items assigned, which can be fewer than provided for, or even zero, in the event of an
14843 early matching failure.
14844 <!--page 308 -->
14851 <pre>
14853 int fgetc(FILE *stream);
14854 </pre>
14857 If the end-of-file indicator for the input stream pointed to by stream is not set and a
14858 next character is present, the fgetc function obtains that character as an unsigned
14859 char converted to an int and advances the associated file position indicator for the
14860 stream (if defined).
14863 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
14864 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
14865 fgetc function returns the next character from the input stream pointed to by stream.
14866 If a read error occurs, the error indicator for the stream is set and the fgetc function
14870 <p><small><a name="note255" href="#note255">255)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
14871 </small>
14876 <pre>
14878 char *fgets(char * restrict s, int n,
14879 FILE * restrict stream);
14880 </pre>
14883 The fgets function reads at most one less than the number of characters specified by n
14884 from the stream pointed to by stream into the array pointed to by s. No additional
14885 characters are read after a new-line character (which is retained) or after end-of-file. A
14886 null character is written immediately after the last character read into the array.
14889 The fgets function returns s if successful. If end-of-file is encountered and no
14890 characters have been read into the array, the contents of the array remain unchanged and a
14891 null pointer is returned. If a read error occurs during the operation, the array contents are
14892 indeterminate and a null pointer is returned.
14897 <!--page 309 -->
14902 <pre>
14904 int fputc(int c, FILE *stream);
14905 </pre>
14908 The fputc function writes the character specified by c (converted to an unsigned
14909 char) to the output stream pointed to by stream, at the position indicated by the
14910 associated file position indicator for the stream (if defined), and advances the indicator
14911 appropriately. If the file cannot support positioning requests, or if the stream was opened
14912 with append mode, the character is appended to the output stream.
14915 The fputc function returns the character written. If a write error occurs, the error
14916 indicator for the stream is set and fputc returns EOF.
14921 <pre>
14923 int fputs(const char * restrict s,
14924 FILE * restrict stream);
14925 </pre>
14928 The fputs function writes the string pointed to by s to the stream pointed to by
14929 stream. The terminating null character is not written.
14932 The fputs function returns EOF if a write error occurs; otherwise it returns a
14933 nonnegative value.
14938 <pre>
14940 int getc(FILE *stream);
14941 </pre>
14944 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
14945 may evaluate stream more than once, so the argument should never be an expression
14946 with side effects.
14947 <!--page 310 -->
14950 The getc function returns the next character from the input stream pointed to by
14951 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14952 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
14953 getc returns EOF.
14958 <pre>
14960 int getchar(void);
14961 </pre>
14964 The getchar function is equivalent to getc with the argument stdin.
14967 The getchar function returns the next character from the input stream pointed to by
14968 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14969 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
14970 getchar returns EOF.
14975 <pre>
14977 char *gets(char *s);
14978 </pre>
14981 The gets function reads characters from the input stream pointed to by stdin, into the
14982 array pointed to by s, until end-of-file is encountered or a new-line character is read.
14983 Any new-line character is discarded, and a null character is written immediately after the
14984 last character read into the array.
14987 The gets function returns s if successful. If end-of-file is encountered and no
14988 characters have been read into the array, the contents of the array remain unchanged and a
14989 null pointer is returned. If a read error occurs during the operation, the array contents are
14990 indeterminate and a null pointer is returned.
14992 <!--page 311 -->
14997 <pre>
14999 int putc(int c, FILE *stream);
15000 </pre>
15003 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
15004 may evaluate stream more than once, so that argument should never be an expression
15005 with side effects.
15008 The putc function returns the character written. If a write error occurs, the error
15009 indicator for the stream is set and putc returns EOF.
15014 <pre>
15016 int putchar(int c);
15017 </pre>
15020 The putchar function is equivalent to putc with the second argument stdout.
15023 The putchar function returns the character written. If a write error occurs, the error
15024 indicator for the stream is set and putchar returns EOF.
15029 <pre>
15031 int puts(const char *s);
15032 </pre>
15035 The puts function writes the string pointed to by s to the stream pointed to by stdout,
15036 and appends a new-line character to the output. The terminating null character is not
15037 written.
15040 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
15041 value.
15042 <!--page 312 -->
15047 <pre>
15049 int ungetc(int c, FILE *stream);
15050 </pre>
15053 The ungetc function pushes the character specified by c (converted to an unsigned
15054 char) back onto the input stream pointed to by stream. Pushed-back characters will be
15055 returned by subsequent reads on that stream in the reverse order of their pushing. A
15056 successful intervening call (with the stream pointed to by stream) to a file positioning
15057 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
15058 stream. The external storage corresponding to the stream is unchanged.
15060 One character of pushback is guaranteed. If the ungetc function is called too many
15061 times on the same stream without an intervening read or file positioning operation on that
15062 stream, the operation may fail.
15064 If the value of c equals that of the macro EOF, the operation fails and the input stream is
15065 unchanged.
15067 A successful call to the ungetc function clears the end-of-file indicator for the stream.
15068 The value of the file position indicator for the stream after reading or discarding all
15069 pushed-back characters shall be the same as it was before the characters were pushed
15070 back. For a text stream, the value of its file position indicator after a successful call to the
15071 ungetc function is unspecified until all pushed-back characters are read or discarded.
15072 For a binary stream, its file position indicator is decremented by each successful call to
15073 the ungetc function; if its value was zero before a call, it is indeterminate after the
15077 The ungetc function returns the character pushed back after conversion, or EOF if the
15078 operation fails.
15084 <!--page 313 -->
15087 <p><small><a name="note256" href="#note256">256)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
15088 </small>
15095 <pre>
15097 size_t fread(void * restrict ptr,
15098 size_t size, size_t nmemb,
15099 FILE * restrict stream);
15100 </pre>
15103 The fread function reads, into the array pointed to by ptr, up to nmemb elements
15104 whose size is specified by size, from the stream pointed to by stream. For each
15105 object, size calls are made to the fgetc function and the results stored, in the order
15106 read, in an array of unsigned char exactly overlaying the object. The file position
15107 indicator for the stream (if defined) is advanced by the number of characters successfully
15108 read. If an error occurs, the resulting value of the file position indicator for the stream is
15109 indeterminate. If a partial element is read, its value is indeterminate.
15112 The fread function returns the number of elements successfully read, which may be
15113 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
15114 fread returns zero and the contents of the array and the state of the stream remain
15115 unchanged.
15120 <pre>
15122 size_t fwrite(const void * restrict ptr,
15123 size_t size, size_t nmemb,
15124 FILE * restrict stream);
15125 </pre>
15128 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
15129 whose size is specified by size, to the stream pointed to by stream. For each object,
15130 size calls are made to the fputc function, taking the values (in order) from an array of
15131 unsigned char exactly overlaying the object. The file position indicator for the
15132 stream (if defined) is advanced by the number of characters successfully written. If an
15133 error occurs, the resulting value of the file position indicator for the stream is
15134 indeterminate.
15135 <!--page 314 -->
15138 The fwrite function returns the number of elements successfully written, which will be
15139 less than nmemb only if a write error is encountered. If size or nmemb is zero,
15140 fwrite returns zero and the state of the stream remains unchanged.
15147 <pre>
15149 int fgetpos(FILE * restrict stream,
15150 fpos_t * restrict pos);
15151 </pre>
15154 The fgetpos function stores the current values of the parse state (if any) and file
15155 position indicator for the stream pointed to by stream in the object pointed to by pos.
15156 The values stored contain unspecified information usable by the fsetpos function for
15157 repositioning the stream to its position at the time of the call to the fgetpos function.
15160 If successful, the fgetpos function returns zero; on failure, the fgetpos function
15161 returns nonzero and stores an implementation-defined positive value in errno.
15167 <pre>
15169 int fseek(FILE *stream, long int offset, int whence);
15170 </pre>
15173 The fseek function sets the file position indicator for the stream pointed to by stream.
15174 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
15176 For a binary stream, the new position, measured in characters from the beginning of the
15177 file, is obtained by adding offset to the position specified by whence. The specified
15178 position is the beginning of the file if whence is SEEK_SET, the current value of the file
15179 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
15180 meaningfully support fseek calls with a whence value of SEEK_END.
15182 For a text stream, either offset shall be zero, or offset shall be a value returned by
15183 an earlier successful call to the ftell function on a stream associated with the same file
15184 and whence shall be SEEK_SET.
15185 <!--page 315 -->
15187 After determining the new position, a successful call to the fseek function undoes any
15188 effects of the ungetc function on the stream, clears the end-of-file indicator for the
15189 stream, and then establishes the new position. After a successful fseek call, the next
15190 operation on an update stream may be either input or output.
15193 The fseek function returns nonzero only for a request that cannot be satisfied.
15199 <pre>
15201 int fsetpos(FILE *stream, const fpos_t *pos);
15202 </pre>
15205 The fsetpos function sets the mbstate_t object (if any) and file position indicator
15206 for the stream pointed to by stream according to the value of the object pointed to by
15207 pos, which shall be a value obtained from an earlier successful call to the fgetpos
15208 function on a stream associated with the same file. If a read or write error occurs, the
15209 error indicator for the stream is set and fsetpos fails.
15211 A successful call to the fsetpos function undoes any effects of the ungetc function
15212 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
15213 parse state and position. After a successful fsetpos call, the next operation on an
15214 update stream may be either input or output.
15217 If successful, the fsetpos function returns zero; on failure, the fsetpos function
15218 returns nonzero and stores an implementation-defined positive value in errno.
15223 <pre>
15225 long int ftell(FILE *stream);
15226 </pre>
15229 The ftell function obtains the current value of the file position indicator for the stream
15230 pointed to by stream. For a binary stream, the value is the number of characters from
15231 the beginning of the file. For a text stream, its file position indicator contains unspecified
15232 information, usable by the fseek function for returning the file position indicator for the
15233 stream to its position at the time of the ftell call; the difference between two such
15234 return values is not necessarily a meaningful measure of the number of characters written
15235 <!--page 316 -->
15236 or read.
15239 If successful, the ftell function returns the current value of the file position indicator
15240 for the stream. On failure, the ftell function returns -1L and stores an
15241 implementation-defined positive value in errno.
15246 <pre>
15248 void rewind(FILE *stream);
15249 </pre>
15252 The rewind function sets the file position indicator for the stream pointed to by
15253 stream to the beginning of the file. It is equivalent to
15254 <pre>
15255 (void)fseek(stream, 0L, SEEK_SET)
15256 </pre>
15257 except that the error indicator for the stream is also cleared.
15260 The rewind function returns no value.
15267 <pre>
15269 void clearerr(FILE *stream);
15270 </pre>
15273 The clearerr function clears the end-of-file and error indicators for the stream pointed
15274 to by stream.
15277 The clearerr function returns no value.
15278 <!--page 317 -->
15283 <pre>
15285 int feof(FILE *stream);
15286 </pre>
15289 The feof function tests the end-of-file indicator for the stream pointed to by stream.
15292 The feof function returns nonzero if and only if the end-of-file indicator is set for
15293 stream.
15298 <pre>
15300 int ferror(FILE *stream);
15301 </pre>
15304 The ferror function tests the error indicator for the stream pointed to by stream.
15307 The ferror function returns nonzero if and only if the error indicator is set for
15308 stream.
15313 <pre>
15315 void perror(const char *s);
15316 </pre>
15319 The perror function maps the error number in the integer expression errno to an
15320 error message. It writes a sequence of characters to the standard error stream thus: first
15321 (if s is not a null pointer and the character pointed to by s is not the null character), the
15322 string pointed to by s followed by a colon (:) and a space; then an appropriate error
15323 message string followed by a new-line character. The contents of the error message
15324 strings are the same as those returned by the strerror function with argument errno.
15327 The perror function returns no value.
15329 <!--page 318 -->
15333 The header <a href="#7.20"><stdlib.h></a> declares five types and several functions of general utility, and
15337 <pre>
15338 div_t
15339 </pre>
15340 which is a structure type that is the type of the value returned by the div function,
15341 <pre>
15342 ldiv_t
15343 </pre>
15344 which is a structure type that is the type of the value returned by the ldiv function, and
15345 <pre>
15346 lldiv_t
15347 </pre>
15348 which is a structure type that is the type of the value returned by the lldiv function.
15351 <pre>
15352 EXIT_FAILURE
15353 </pre>
15354 and
15355 <pre>
15356 EXIT_SUCCESS
15357 </pre>
15358 which expand to integer constant expressions that can be used as the argument to the
15359 exit function to return unsuccessful or successful termination status, respectively, to the
15360 host environment;
15361 <pre>
15362 RAND_MAX
15363 </pre>
15364 which expands to an integer constant expression that is the maximum value returned by
15365 the rand function; and
15366 <pre>
15367 MB_CUR_MAX
15368 </pre>
15369 which expands to a positive integer expression with type size_t that is the maximum
15370 number of bytes in a multibyte character for the extended character set specified by the
15371 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
15376 <!--page 319 -->
15379 <p><small><a name="note257" href="#note257">257)</a> See ''future library directions'' (<a href="#7.26.10">7.26.10</a>).
15380 </small>
15384 The functions atof, atoi, atol, and atoll need not affect the value of the integer
15385 expression errno on an error. If the value of the result cannot be represented, the
15386 behavior is undefined.
15391 <pre>
15393 double atof(const char *nptr);
15394 </pre>
15397 The atof function converts the initial portion of the string pointed to by nptr to
15398 double representation. Except for the behavior on error, it is equivalent to
15399 <pre>
15400 strtod(nptr, (char **)NULL)
15401 </pre>
15404 The atof function returns the converted value.
15405 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
15410 <pre>
15412 int atoi(const char *nptr);
15413 long int atol(const char *nptr);
15414 long long int atoll(const char *nptr);
15415 </pre>
15418 The atoi, atol, and atoll functions convert the initial portion of the string pointed
15419 to by nptr to int, long int, and long long int representation, respectively.
15420 Except for the behavior on error, they are equivalent to
15421 <pre>
15422 atoi: (int)strtol(nptr, (char **)NULL, 10)
15423 atol: strtol(nptr, (char **)NULL, 10)
15424 atoll: strtoll(nptr, (char **)NULL, 10)
15425 </pre>
15428 The atoi, atol, and atoll functions return the converted value.
15431 <!--page 320 -->
15433 <h5><a name="7.20.1.3" href="#7.20.1.3">7.20.1.3 The strtod, strtof, and strtold functions</a></h5>
15436 <pre>
15438 double strtod(const char * restrict nptr,
15439 char ** restrict endptr);
15440 float strtof(const char * restrict nptr,
15441 char ** restrict endptr);
15442 long double strtold(const char * restrict nptr,
15443 char ** restrict endptr);
15444 </pre>
15447 The strtod, strtof, and strtold functions convert the initial portion of the string
15448 pointed to by nptr to double, float, and long double representation,
15449 respectively. First, they decompose the input string into three parts: an initial, possibly
15450 empty, sequence of white-space characters (as specified by the isspace function), a
15451 subject sequence resembling a floating-point constant or representing an infinity or NaN;
15452 and a final string of one or more unrecognized characters, including the terminating null
15453 character of the input string. Then, they attempt to convert the subject sequence to a
15454 floating-point number, and return the result.
15456 The expected form of the subject sequence is an optional plus or minus sign, then one of
15457 the following:
15458 <ul>
15459 <li> a nonempty sequence of decimal digits optionally containing a decimal-point
15462 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
15463 <li> INF or INFINITY, ignoring case
15465 <pre>
15466 n-char-sequence:
15467 digit
15468 nondigit
15469 n-char-sequence digit
15470 n-char-sequence nondigit
15471 </pre>
15472 </ul>
15473 The subject sequence is defined as the longest initial subsequence of the input string,
15474 starting with the first non-white-space character, that is of the expected form. The subject
15475 sequence contains no characters if the input string is not of the expected form.
15477 If the subject sequence has the expected form for a floating-point number, the sequence of
15478 characters starting with the first digit or the decimal-point character (whichever occurs
15479 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
15480 <!--page 321 -->
15481 decimal-point character is used in place of a period, and that if neither an exponent part
15482 nor a decimal-point character appears in a decimal floating point number, or if a binary
15483 exponent part does not appear in a hexadecimal floating point number, an exponent part
15484 of the appropriate type with value zero is assumed to follow the last digit in the string. If
15485 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note258"><b>258)</b></a></sup>
15486 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
15487 the return type, else like a floating constant that is too large for the range of the return
15488 type. A character sequence NAN or NAN(n-char-sequence<sub>opt</sub>), is interpreted as a quiet
15489 NaN, if supported in the return type, else like a subject sequence part that does not have
15490 the expected form; the meaning of the n-char sequences is implementation-defined.<sup><a href="#note259"><b>259)</b></a></sup> A
15491 pointer to the final string is stored in the object pointed to by endptr, provided that
15492 endptr is not a null pointer.
15494 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
15495 value resulting from the conversion is correctly rounded.
15497 In other than the "C" locale, additional locale-specific subject sequence forms may be
15498 accepted.
15500 If the subject sequence is empty or does not have the expected form, no conversion is
15501 performed; the value of nptr is stored in the object pointed to by endptr, provided
15502 that endptr is not a null pointer.
15505 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
15506 the result is not exactly representable, the result should be one of the two numbers in the
15507 appropriate internal format that are adjacent to the hexadecimal floating source value,
15508 with the extra stipulation that the error should have a correct sign for the current rounding
15509 direction.
15511 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
15512 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
15513 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
15514 consider the two bounding, adjacent decimal strings L and U, both having
15515 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
15516 The result should be one of the (equal or adjacent) values that would be obtained by
15517 correctly rounding L and U according to the current rounding direction, with the extra
15519 <!--page 322 -->
15520 stipulation that the error with respect to D should have a correct sign for the current
15524 The functions return the converted value, if any. If no conversion could be performed,
15525 zero is returned. If the correct value is outside the range of representable values, plus or
15526 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
15527 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
15528 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
15529 than the smallest normalized positive number in the return type; whether errno acquires
15530 the value ERANGE is implementation-defined.
15533 <p><small><a name="note258" href="#note258">258)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
15534 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
15535 methods may yield different results if rounding is toward positive or negative infinity. In either case,
15536 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
15537 </small>
15538 <p><small><a name="note259" href="#note259">259)</a> An implementation may use the n-char sequence to determine extra information to be represented in
15539 the NaN's significand.
15540 </small>
15541 <p><small><a name="note260" href="#note260">260)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
15542 to the same internal floating value, but if not will round to adjacent values.
15543 </small>
15545 <h5><a name="7.20.1.4" href="#7.20.1.4">7.20.1.4 The strtol, strtoll, strtoul, and strtoull functions</a></h5>
15548 <pre>
15550 long int strtol(
15551 const char * restrict nptr,
15552 char ** restrict endptr,
15553 int base);
15554 long long int strtoll(
15555 const char * restrict nptr,
15556 char ** restrict endptr,
15557 int base);
15558 unsigned long int strtoul(
15559 const char * restrict nptr,
15560 char ** restrict endptr,
15561 int base);
15562 unsigned long long int strtoull(
15563 const char * restrict nptr,
15564 char ** restrict endptr,
15565 int base);
15566 </pre>
15569 The strtol, strtoll, strtoul, and strtoull functions convert the initial
15570 portion of the string pointed to by nptr to long int, long long int, unsigned
15571 long int, and unsigned long long int representation, respectively. First,
15572 they decompose the input string into three parts: an initial, possibly empty, sequence of
15573 white-space characters (as specified by the isspace function), a subject sequence
15576 <!--page 323 -->
15577 resembling an integer represented in some radix determined by the value of base, and a
15578 final string of one or more unrecognized characters, including the terminating null
15579 character of the input string. Then, they attempt to convert the subject sequence to an
15580 integer, and return the result.
15582 If the value of base is zero, the expected form of the subject sequence is that of an
15583 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
15585 expected form of the subject sequence is a sequence of letters and digits representing an
15586 integer with the radix specified by base, optionally preceded by a plus or minus sign,
15587 but not including an integer suffix. The letters from a (or A) through z (or Z) are
15590 optionally precede the sequence of letters and digits, following the sign if present.
15592 The subject sequence is defined as the longest initial subsequence of the input string,
15593 starting with the first non-white-space character, that is of the expected form. The subject
15594 sequence contains no characters if the input string is empty or consists entirely of white
15595 space, or if the first non-white-space character is other than a sign or a permissible letter
15596 or digit.
15598 If the subject sequence has the expected form and the value of base is zero, the sequence
15599 of characters starting with the first digit is interpreted as an integer constant according to
15600 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
15601 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
15602 as given above. If the subject sequence begins with a minus sign, the value resulting from
15603 the conversion is negated (in the return type). A pointer to the final string is stored in the
15604 object pointed to by endptr, provided that endptr is not a null pointer.
15606 In other than the "C" locale, additional locale-specific subject sequence forms may be
15607 accepted.
15609 If the subject sequence is empty or does not have the expected form, no conversion is
15610 performed; the value of nptr is stored in the object pointed to by endptr, provided
15611 that endptr is not a null pointer.
15614 The strtol, strtoll, strtoul, and strtoull functions return the converted
15615 value, if any. If no conversion could be performed, zero is returned. If the correct value
15616 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
15617 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
15618 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
15619 <!--page 324 -->
15621 <h4><a name="7.20.2" href="#7.20.2">7.20.2 Pseudo-random sequence generation functions</a></h4>
15626 <pre>
15628 int rand(void);
15629 </pre>
15632 The rand function computes a sequence of pseudo-random integers in the range 0 to
15633 RAND_MAX.
15635 The implementation shall behave as if no library function calls the rand function.
15638 The rand function returns a pseudo-random integer.
15641 The value of the RAND_MAX macro shall be at least 32767.
15646 <pre>
15648 void srand(unsigned int seed);
15649 </pre>
15652 The srand function uses the argument as a seed for a new sequence of pseudo-random
15653 numbers to be returned by subsequent calls to rand. If srand is then called with the
15654 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
15655 called before any calls to srand have been made, the same sequence shall be generated
15656 as when srand is first called with a seed value of 1.
15658 The implementation shall behave as if no library function calls the srand function.
15661 The srand function returns no value.
15663 EXAMPLE The following functions define a portable implementation of rand and srand.
15664 <!--page 325 -->
15665 <pre>
15666 static unsigned long int next = 1;
15667 int rand(void) // RAND_MAX assumed to be 32767
15668 {
15671 }
15672 void srand(unsigned int seed)
15673 {
15674 next = seed;
15675 }
15676 </pre>
15681 The order and contiguity of storage allocated by successive calls to the calloc,
15682 malloc, and realloc functions is unspecified. The pointer returned if the allocation
15683 succeeds is suitably aligned so that it may be assigned to a pointer to any type of object
15684 and then used to access such an object or an array of such objects in the space allocated
15685 (until the space is explicitly deallocated). The lifetime of an allocated object extends
15686 from the allocation until the deallocation. Each such allocation shall yield a pointer to an
15687 object disjoint from any other object. The pointer returned points to the start (lowest byte
15688 address) of the allocated space. If the space cannot be allocated, a null pointer is
15689 returned. If the size of the space requested is zero, the behavior is implementation-
15690 defined: either a null pointer is returned, or the behavior is as if the size were some
15691 nonzero value, except that the returned pointer shall not be used to access an object.
15696 <pre>
15698 void *calloc(size_t nmemb, size_t size);
15699 </pre>
15702 The calloc function allocates space for an array of nmemb objects, each of whose size
15703 is size. The space is initialized to all bits zero.<sup><a href="#note261"><b>261)</b></a></sup>
15706 The calloc function returns either a null pointer or a pointer to the allocated space.
15709 <p><small><a name="note261" href="#note261">261)</a> Note that this need not be the same as the representation of floating-point zero or a null pointer
15710 constant.
15711 </small>
15716 <pre>
15718 void free(void *ptr);
15719 </pre>
15722 The free function causes the space pointed to by ptr to be deallocated, that is, made
15723 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
15724 the argument does not match a pointer earlier returned by the calloc, malloc, or
15727 <!--page 326 -->
15728 realloc function, or if the space has been deallocated by a call to free or realloc,
15729 the behavior is undefined.
15732 The free function returns no value.
15737 <pre>
15739 void *malloc(size_t size);
15740 </pre>
15743 The malloc function allocates space for an object whose size is specified by size and
15744 whose value is indeterminate.
15747 The malloc function returns either a null pointer or a pointer to the allocated space.
15752 <pre>
15754 void *realloc(void *ptr, size_t size);
15755 </pre>
15758 The realloc function deallocates the old object pointed to by ptr and returns a
15759 pointer to a new object that has the size specified by size. The contents of the new
15760 object shall be the same as that of the old object prior to deallocation, up to the lesser of
15761 the new and old sizes. Any bytes in the new object beyond the size of the old object have
15762 indeterminate values.
15764 If ptr is a null pointer, the realloc function behaves like the malloc function for the
15765 specified size. Otherwise, if ptr does not match a pointer earlier returned by the
15766 calloc, malloc, or realloc function, or if the space has been deallocated by a call
15767 to the free or realloc function, the behavior is undefined. If memory for the new
15768 object cannot be allocated, the old object is not deallocated and its value is unchanged.
15771 The realloc function returns a pointer to the new object (which may have the same
15772 value as a pointer to the old object), or a null pointer if the new object could not be
15773 allocated.
15774 <!--page 327 -->
15781 <pre>
15783 void abort(void);
15784 </pre>
15787 The abort function causes abnormal program termination to occur, unless the signal
15788 SIGABRT is being caught and the signal handler does not return. Whether open streams
15789 with unwritten buffered data are flushed, open streams are closed, or temporary files are
15790 removed is implementation-defined. An implementation-defined form of the status
15791 unsuccessful termination is returned to the host environment by means of the function
15792 call raise(SIGABRT).
15795 The abort function does not return to its caller.
15800 <pre>
15802 int atexit(void (*func)(void));
15803 </pre>
15806 The atexit function registers the function pointed to by func, to be called without
15807 arguments at normal program termination.
15810 The implementation shall support the registration of at least 32 functions.
15813 The atexit function returns zero if the registration succeeds, nonzero if it fails.
15819 <pre>
15821 void exit(int status);
15822 </pre>
15825 The exit function causes normal program termination to occur. If more than one call to
15826 the exit function is executed by a program, the behavior is undefined.
15827 <!--page 328 -->
15829 First, all functions registered by the atexit function are called, in the reverse order of
15830 their registration,<sup><a href="#note262"><b>262)</b></a></sup> except that a function is called after any previously registered
15831 functions that had already been called at the time it was registered. If, during the call to
15832 any such function, a call to the longjmp function is made that would terminate the call
15833 to the registered function, the behavior is undefined.
15835 Next, all open streams with unwritten buffered data are flushed, all open streams are
15836 closed, and all files created by the tmpfile function are removed.
15838 Finally, control is returned to the host environment. If the value of status is zero or
15839 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
15840 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
15841 of the status unsuccessful termination is returned. Otherwise the status returned is
15842 implementation-defined.
15845 The exit function cannot return to its caller.
15848 <p><small><a name="note262" href="#note262">262)</a> Each function is called as many times as it was registered, and in the correct order with respect to
15849 other registered functions.
15850 </small>
15855 <pre>
15857 void _Exit(int status);
15858 </pre>
15861 The _Exit function causes normal program termination to occur and control to be
15862 returned to the host environment. No functions registered by the atexit function or
15863 signal handlers registered by the signal function are called. The status returned to the
15864 host environment is determined in the same way as for the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
15865 Whether open streams with unwritten buffered data are flushed, open streams are closed,
15866 or temporary files are removed is implementation-defined.
15869 The _Exit function cannot return to its caller.
15874 <!--page 329 -->
15879 <pre>
15881 char *getenv(const char *name);
15882 </pre>
15885 The getenv function searches an environment list, provided by the host environment,
15886 for a string that matches the string pointed to by name. The set of environment names
15887 and the method for altering the environment list are implementation-defined.
15889 The implementation shall behave as if no library function calls the getenv function.
15892 The getenv function returns a pointer to a string associated with the matched list
15893 member. The string pointed to shall not be modified by the program, but may be
15894 overwritten by a subsequent call to the getenv function. If the specified name cannot
15895 be found, a null pointer is returned.
15900 <pre>
15902 int system(const char *string);
15903 </pre>
15906 If string is a null pointer, the system function determines whether the host
15907 environment has a command processor. If string is not a null pointer, the system
15908 function passes the string pointed to by string to that command processor to be
15909 executed in a manner which the implementation shall document; this might then cause the
15910 program calling system to behave in a non-conforming manner or to terminate.
15913 If the argument is a null pointer, the system function returns nonzero only if a
15914 command processor is available. If the argument is not a null pointer, and the system
15915 function does return, it returns an implementation-defined value.
15916 <!--page 330 -->
15920 These utilities make use of a comparison function to search or sort arrays of unspecified
15921 type. Where an argument declared as size_t nmemb specifies the length of the array
15922 for a function, nmemb can have the value zero on a call to that function; the comparison
15923 function is not called, a search finds no matching element, and sorting performs no
15924 rearrangement. Pointer arguments on such a call shall still have valid values, as described
15927 The implementation shall ensure that the second argument of the comparison function
15928 (when called from bsearch), or both arguments (when called from qsort), are
15929 pointers to elements of the array.<sup><a href="#note263"><b>263)</b></a></sup> The first argument when called from bsearch
15930 shall equal key.
15932 The comparison function shall not alter the contents of the array. The implementation
15933 may reorder elements of the array between calls to the comparison function, but shall not
15934 alter the contents of any individual element.
15936 When the same objects (consisting of size bytes, irrespective of their current positions
15937 in the array) are passed more than once to the comparison function, the results shall be
15938 consistent with one another. That is, for qsort they shall define a total ordering on the
15939 array, and for bsearch the same object shall always compare the same way with the
15940 key.
15942 A sequence point occurs immediately before and immediately after each call to the
15943 comparison function, and also between any call to the comparison function and any
15944 movement of the objects passed as arguments to that call.
15947 <p><small><a name="note263" href="#note263">263)</a> That is, if the value passed is p, then the following expressions are always nonzero:
15949 <pre>
15950 ((char *)p - (char *)base) % size == 0
15951 (char *)p >= (char *)base
15952 (char *)p < (char *)base + nmemb * size
15953 </pre>
15954 </small>
15959 <pre>
15961 void *bsearch(const void *key, const void *base,
15962 size_t nmemb, size_t size,
15963 int (*compar)(const void *, const void *));
15964 </pre>
15967 The bsearch function searches an array of nmemb objects, the initial element of which
15968 is pointed to by base, for an element that matches the object pointed to by key. The
15971 <!--page 331 -->
15972 size of each element of the array is specified by size.
15974 The comparison function pointed to by compar is called with two arguments that point
15975 to the key object and to an array element, in that order. The function shall return an
15976 integer less than, equal to, or greater than zero if the key object is considered,
15977 respectively, to be less than, to match, or to be greater than the array element. The array
15978 shall consist of: all the elements that compare less than, all the elements that compare
15979 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note264"><b>264)</b></a></sup>
15982 The bsearch function returns a pointer to a matching element of the array, or a null
15983 pointer if no match is found. If two elements compare as equal, which element is
15984 matched is unspecified.
15987 <p><small><a name="note264" href="#note264">264)</a> In practice, the entire array is sorted according to the comparison function.
15988 </small>
15993 <pre>
15995 void qsort(void *base, size_t nmemb, size_t size,
15996 int (*compar)(const void *, const void *));
15997 </pre>
16000 The qsort function sorts an array of nmemb objects, the initial element of which is
16001 pointed to by base. The size of each object is specified by size.
16003 The contents of the array are sorted into ascending order according to a comparison
16004 function pointed to by compar, which is called with two arguments that point to the
16005 objects being compared. The function shall return an integer less than, equal to, or
16006 greater than zero if the first argument is considered to be respectively less than, equal to,
16007 or greater than the second.
16009 If two elements compare as equal, their order in the resulting sorted array is unspecified.
16012 The qsort function returns no value.
16017 <!--page 332 -->
16024 <pre>
16026 int abs(int j);
16027 long int labs(long int j);
16028 long long int llabs(long long int j);
16029 </pre>
16032 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
16033 result cannot be represented, the behavior is undefined.<sup><a href="#note265"><b>265)</b></a></sup>
16036 The abs, labs, and llabs, functions return the absolute value.
16039 <p><small><a name="note265" href="#note265">265)</a> The absolute value of the most negative number cannot be represented in two's complement.
16040 </small>
16045 <pre>
16047 div_t div(int numer, int denom);
16048 ldiv_t ldiv(long int numer, long int denom);
16049 lldiv_t lldiv(long long int numer, long long int denom);
16050 </pre>
16053 The div, ldiv, and lldiv, functions compute numer / denom and numer %
16054 denom in a single operation.
16057 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
16058 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
16059 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
16060 each of which has the same type as the arguments numer and denom. If either part of
16061 the result cannot be represented, the behavior is undefined.
16066 <!--page 333 -->
16068 <h4><a name="7.20.7" href="#7.20.7">7.20.7 Multibyte/wide character conversion functions</a></h4>
16070 The behavior of the multibyte character functions is affected by the LC_CTYPE category
16071 of the current locale. For a state-dependent encoding, each function is placed into its
16072 initial conversion state by a call for which its character pointer argument, s, is a null
16073 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
16074 state of the function to be altered as necessary. A call with s as a null pointer causes
16075 these functions to return a nonzero value if encodings have state dependency, and zero
16076 otherwise.<sup><a href="#note266"><b>266)</b></a></sup> Changing the LC_CTYPE category causes the conversion state of these
16077 functions to be indeterminate.
16080 <p><small><a name="note266" href="#note266">266)</a> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
16081 character codes, but are grouped with an adjacent multibyte character.
16082 </small>
16087 <pre>
16089 int mblen(const char *s, size_t n);
16090 </pre>
16093 If s is not a null pointer, the mblen function determines the number of bytes contained
16094 in the multibyte character pointed to by s. Except that the conversion state of the
16095 mbtowc function is not affected, it is equivalent to
16096 <pre>
16097 mbtowc((wchar_t *)0, s, n);
16098 </pre>
16100 The implementation shall behave as if no library function calls the mblen function.
16103 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
16104 character encodings, respectively, do or do not have state-dependent encodings. If s is
16105 not a null pointer, the mblen function either returns 0 (if s points to the null character),
16106 or returns the number of bytes that are contained in the multibyte character (if the next n
16107 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
16108 multibyte character).
16114 <!--page 334 -->
16119 <pre>
16121 int mbtowc(wchar_t * restrict pwc,
16122 const char * restrict s,
16123 size_t n);
16124 </pre>
16127 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
16128 the byte pointed to by s to determine the number of bytes needed to complete the next
16129 multibyte character (including any shift sequences). If the function determines that the
16130 next multibyte character is complete and valid, it determines the value of the
16131 corresponding wide character and then, if pwc is not a null pointer, stores that value in
16132 the object pointed to by pwc. If the corresponding wide character is the null wide
16133 character, the function is left in the initial conversion state.
16135 The implementation shall behave as if no library function calls the mbtowc function.
16138 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
16139 character encodings, respectively, do or do not have state-dependent encodings. If s is
16140 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
16141 or returns the number of bytes that are contained in the converted multibyte character (if
16142 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
16143 form a valid multibyte character).
16145 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
16146 macro.
16151 <pre>
16153 int wctomb(char *s, wchar_t wc);
16154 </pre>
16157 The wctomb function determines the number of bytes needed to represent the multibyte
16158 character corresponding to the wide character given by wc (including any shift
16159 sequences), and stores the multibyte character representation in the array whose first
16160 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
16161 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
16162 sequence needed to restore the initial shift state, and the function is left in the initial
16163 conversion state.
16164 <!--page 335 -->
16166 The implementation shall behave as if no library function calls the wctomb function.
16169 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
16170 character encodings, respectively, do or do not have state-dependent encodings. If s is
16171 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
16172 to a valid multibyte character, or returns the number of bytes that are contained in the
16173 multibyte character corresponding to the value of wc.
16175 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
16177 <h4><a name="7.20.8" href="#7.20.8">7.20.8 Multibyte/wide string conversion functions</a></h4>
16179 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
16180 the current locale.
16185 <pre>
16187 size_t mbstowcs(wchar_t * restrict pwcs,
16188 const char * restrict s,
16189 size_t n);
16190 </pre>
16193 The mbstowcs function converts a sequence of multibyte characters that begins in the
16194 initial shift state from the array pointed to by s into a sequence of corresponding wide
16195 characters and stores not more than n wide characters into the array pointed to by pwcs.
16196 No multibyte characters that follow a null character (which is converted into a null wide
16197 character) will be examined or converted. Each multibyte character is converted as if by
16198 a call to the mbtowc function, except that the conversion state of the mbtowc function is
16199 not affected.
16201 No more than n elements will be modified in the array pointed to by pwcs. If copying
16202 takes place between objects that overlap, the behavior is undefined.
16205 If an invalid multibyte character is encountered, the mbstowcs function returns
16206 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
16207 elements modified, not including a terminating null wide character, if any.<sup><a href="#note267"><b>267)</b></a></sup>
16212 <!--page 336 -->
16215 <p><small><a name="note267" href="#note267">267)</a> The array will not be null-terminated if the value returned is n.
16216 </small>
16221 <pre>
16223 size_t wcstombs(char * restrict s,
16224 const wchar_t * restrict pwcs,
16225 size_t n);
16226 </pre>
16229 The wcstombs function converts a sequence of wide characters from the array pointed
16230 to by pwcs into a sequence of corresponding multibyte characters that begins in the
16231 initial shift state, and stores these multibyte characters into the array pointed to by s,
16232 stopping if a multibyte character would exceed the limit of n total bytes or if a null
16233 character is stored. Each wide character is converted as if by a call to the wctomb
16234 function, except that the conversion state of the wctomb function is not affected.
16236 No more than n bytes will be modified in the array pointed to by s. If copying takes place
16237 between objects that overlap, the behavior is undefined.
16240 If a wide character is encountered that does not correspond to a valid multibyte character,
16241 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
16242 returns the number of bytes modified, not including a terminating null character, if
16244 <!--page 337 -->
16250 The header <a href="#7.21"><string.h></a> declares one type and several functions, and defines one
16251 macro useful for manipulating arrays of character type and other objects treated as arrays
16252 of character type.<sup><a href="#note268"><b>268)</b></a></sup> The type is size_t and the macro is NULL (both described in
16253 <a href="#7.17">7.17</a>). Various methods are used for determining the lengths of the arrays, but in all cases
16254 a char * or void * argument points to the initial (lowest addressed) character of the
16255 array. If an array is accessed beyond the end of an object, the behavior is undefined.
16257 Where an argument declared as size_t n specifies the length of the array for a
16258 function, n can have the value zero on a call to that function. Unless explicitly stated
16259 otherwise in the description of a particular function in this subclause, pointer arguments
16260 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
16261 function that locates a character finds no occurrence, a function that compares two
16262 character sequences returns zero, and a function that copies characters copies zero
16263 characters.
16265 For all functions in this subclause, each character shall be interpreted as if it had the type
16266 unsigned char (and therefore every possible object representation is valid and has a
16267 different value).
16270 <p><small><a name="note268" href="#note268">268)</a> See ''future library directions'' (<a href="#7.26.11">7.26.11</a>).
16271 </small>
16278 <pre>
16280 void *memcpy(void * restrict s1,
16281 const void * restrict s2,
16282 size_t n);
16283 </pre>
16286 The memcpy function copies n characters from the object pointed to by s2 into the
16287 object pointed to by s1. If copying takes place between objects that overlap, the behavior
16288 is undefined.
16291 The memcpy function returns the value of s1.
16296 <!--page 338 -->
16301 <pre>
16303 void *memmove(void *s1, const void *s2, size_t n);
16304 </pre>
16307 The memmove function copies n characters from the object pointed to by s2 into the
16308 object pointed to by s1. Copying takes place as if the n characters from the object
16309 pointed to by s2 are first copied into a temporary array of n characters that does not
16310 overlap the objects pointed to by s1 and s2, and then the n characters from the
16311 temporary array are copied into the object pointed to by s1.
16314 The memmove function returns the value of s1.
16319 <pre>
16321 char *strcpy(char * restrict s1,
16322 const char * restrict s2);
16323 </pre>
16326 The strcpy function copies the string pointed to by s2 (including the terminating null
16327 character) into the array pointed to by s1. If copying takes place between objects that
16328 overlap, the behavior is undefined.
16331 The strcpy function returns the value of s1.
16336 <pre>
16338 char *strncpy(char * restrict s1,
16339 const char * restrict s2,
16340 size_t n);
16341 </pre>
16344 The strncpy function copies not more than n characters (characters that follow a null
16345 character are not copied) from the array pointed to by s2 to the array pointed to by
16346 <!--page 339 -->
16347 s1.<sup><a href="#note269"><b>269)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
16349 If the array pointed to by s2 is a string that is shorter than n characters, null characters
16350 are appended to the copy in the array pointed to by s1, until n characters in all have been
16351 written.
16354 The strncpy function returns the value of s1.
16357 <p><small><a name="note269" href="#note269">269)</a> Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
16358 not be null-terminated.
16359 </small>
16366 <pre>
16368 char *strcat(char * restrict s1,
16369 const char * restrict s2);
16370 </pre>
16373 The strcat function appends a copy of the string pointed to by s2 (including the
16374 terminating null character) to the end of the string pointed to by s1. The initial character
16375 of s2 overwrites the null character at the end of s1. If copying takes place between
16376 objects that overlap, the behavior is undefined.
16379 The strcat function returns the value of s1.
16384 <pre>
16386 char *strncat(char * restrict s1,
16387 const char * restrict s2,
16388 size_t n);
16389 </pre>
16392 The strncat function appends not more than n characters (a null character and
16393 characters that follow it are not appended) from the array pointed to by s2 to the end of
16394 the string pointed to by s1. The initial character of s2 overwrites the null character at the
16395 end of s1. A terminating null character is always appended to the result.<sup><a href="#note270"><b>270)</b></a></sup> If copying
16397 <!--page 340 -->
16398 takes place between objects that overlap, the behavior is undefined.
16401 The strncat function returns the value of s1.
16405 <p><small><a name="note270" href="#note270">270)</a> Thus, the maximum number of characters that can end up in the array pointed to by s1 is
16406 strlen(s1)+n+1.
16407 </small>
16411 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
16412 and strncmp is determined by the sign of the difference between the values of the first
16413 pair of characters (both interpreted as unsigned char) that differ in the objects being
16414 compared.
16419 <pre>
16421 int memcmp(const void *s1, const void *s2, size_t n);
16422 </pre>
16425 The memcmp function compares the first n characters of the object pointed to by s1 to
16426 the first n characters of the object pointed to by s2.<sup><a href="#note271"><b>271)</b></a></sup>
16429 The memcmp function returns an integer greater than, equal to, or less than zero,
16430 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
16431 pointed to by s2.
16434 <p><small><a name="note271" href="#note271">271)</a> The contents of ''holes'' used as padding for purposes of alignment within structure objects are
16435 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
16436 comparison.
16437 </small>
16442 <pre>
16444 int strcmp(const char *s1, const char *s2);
16445 </pre>
16448 The strcmp function compares the string pointed to by s1 to the string pointed to by
16449 s2.
16452 The strcmp function returns an integer greater than, equal to, or less than zero,
16453 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
16455 <!--page 341 -->
16456 pointed to by s2.
16461 <pre>
16463 int strcoll(const char *s1, const char *s2);
16464 </pre>
16467 The strcoll function compares the string pointed to by s1 to the string pointed to by
16468 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
16471 The strcoll function returns an integer greater than, equal to, or less than zero,
16472 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
16473 pointed to by s2 when both are interpreted as appropriate to the current locale.
16478 <pre>
16480 int strncmp(const char *s1, const char *s2, size_t n);
16481 </pre>
16484 The strncmp function compares not more than n characters (characters that follow a
16485 null character are not compared) from the array pointed to by s1 to the array pointed to
16486 by s2.
16489 The strncmp function returns an integer greater than, equal to, or less than zero,
16490 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
16491 to, or less than the possibly null-terminated array pointed to by s2.
16496 <pre>
16498 size_t strxfrm(char * restrict s1,
16499 const char * restrict s2,
16500 size_t n);
16501 </pre>
16504 The strxfrm function transforms the string pointed to by s2 and places the resulting
16505 string into the array pointed to by s1. The transformation is such that if the strcmp
16506 function is applied to two transformed strings, it returns a value greater than, equal to, or
16507 <!--page 342 -->
16508 less than zero, corresponding to the result of the strcoll function applied to the same
16509 two original strings. No more than n characters are placed into the resulting array
16510 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
16511 be a null pointer. If copying takes place between objects that overlap, the behavior is
16512 undefined.
16515 The strxfrm function returns the length of the transformed string (not including the
16516 terminating null character). If the value returned is n or more, the contents of the array
16517 pointed to by s1 are indeterminate.
16519 EXAMPLE The value of the following expression is the size of the array needed to hold the
16520 transformation of the string pointed to by s.
16521 <pre>
16523 </pre>
16531 <pre>
16533 void *memchr(const void *s, int c, size_t n);
16534 </pre>
16537 The memchr function locates the first occurrence of c (converted to an unsigned
16538 char) in the initial n characters (each interpreted as unsigned char) of the object
16539 pointed to by s.
16542 The memchr function returns a pointer to the located character, or a null pointer if the
16543 character does not occur in the object.
16548 <pre>
16550 char *strchr(const char *s, int c);
16551 </pre>
16554 The strchr function locates the first occurrence of c (converted to a char) in the
16555 string pointed to by s. The terminating null character is considered to be part of the
16556 string.
16559 The strchr function returns a pointer to the located character, or a null pointer if the
16560 character does not occur in the string.
16561 <!--page 343 -->
16566 <pre>
16568 size_t strcspn(const char *s1, const char *s2);
16569 </pre>
16572 The strcspn function computes the length of the maximum initial segment of the string
16573 pointed to by s1 which consists entirely of characters not from the string pointed to by
16574 s2.
16577 The strcspn function returns the length of the segment.
16582 <pre>
16584 char *strpbrk(const char *s1, const char *s2);
16585 </pre>
16588 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
16589 character from the string pointed to by s2.
16592 The strpbrk function returns a pointer to the character, or a null pointer if no character
16593 from s2 occurs in s1.
16598 <pre>
16600 char *strrchr(const char *s, int c);
16601 </pre>
16604 The strrchr function locates the last occurrence of c (converted to a char) in the
16605 string pointed to by s. The terminating null character is considered to be part of the
16606 string.
16609 The strrchr function returns a pointer to the character, or a null pointer if c does not
16610 occur in the string.
16611 <!--page 344 -->
16616 <pre>
16618 size_t strspn(const char *s1, const char *s2);
16619 </pre>
16622 The strspn function computes the length of the maximum initial segment of the string
16623 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
16626 The strspn function returns the length of the segment.
16631 <pre>
16633 char *strstr(const char *s1, const char *s2);
16634 </pre>
16637 The strstr function locates the first occurrence in the string pointed to by s1 of the
16638 sequence of characters (excluding the terminating null character) in the string pointed to
16639 by s2.
16642 The strstr function returns a pointer to the located string, or a null pointer if the string
16643 is not found. If s2 points to a string with zero length, the function returns s1.
16648 <pre>
16650 char *strtok(char * restrict s1,
16651 const char * restrict s2);
16652 </pre>
16655 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
16656 sequence of tokens, each of which is delimited by a character from the string pointed to
16657 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
16658 sequence have a null first argument. The separator string pointed to by s2 may be
16659 different from call to call.
16661 The first call in the sequence searches the string pointed to by s1 for the first character
16662 that is not contained in the current separator string pointed to by s2. If no such character
16663 is found, then there are no tokens in the string pointed to by s1 and the strtok function
16664 <!--page 345 -->
16665 returns a null pointer. If such a character is found, it is the start of the first token.
16667 The strtok function then searches from there for a character that is contained in the
16668 current separator string. If no such character is found, the current token extends to the
16669 end of the string pointed to by s1, and subsequent searches for a token will return a null
16670 pointer. If such a character is found, it is overwritten by a null character, which
16671 terminates the current token. The strtok function saves a pointer to the following
16672 character, from which the next search for a token will start.
16674 Each subsequent call, with a null pointer as the value of the first argument, starts
16675 searching from the saved pointer and behaves as described above.
16677 The implementation shall behave as if no library function calls the strtok function.
16680 The strtok function returns a pointer to the first character of a token, or a null pointer
16681 if there is no token.
16683 EXAMPLE
16684 <pre>
16686 static char str[] = "?a???b,,,#c";
16687 char *t;
16691 t = strtok(NULL, "?"); // t is a null pointer
16692 </pre>
16700 <pre>
16702 void *memset(void *s, int c, size_t n);
16703 </pre>
16706 The memset function copies the value of c (converted to an unsigned char) into
16707 each of the first n characters of the object pointed to by s.
16710 The memset function returns the value of s.
16711 <!--page 346 -->
16716 <pre>
16718 char *strerror(int errnum);
16719 </pre>
16722 The strerror function maps the number in errnum to a message string. Typically,
16723 the values for errnum come from errno, but strerror shall map any value of type
16724 int to a message.
16726 The implementation shall behave as if no library function calls the strerror function.
16729 The strerror function returns a pointer to the string, the contents of which are locale-
16730 specific. The array pointed to shall not be modified by the program, but may be
16731 overwritten by a subsequent call to the strerror function.
16736 <pre>
16738 size_t strlen(const char *s);
16739 </pre>
16742 The strlen function computes the length of the string pointed to by s.
16745 The strlen function returns the number of characters that precede the terminating null
16746 character.
16747 <!--page 347 -->
16751 The header <a href="#7.22"><tgmath.h></a> includes the headers <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> and
16752 defines several type-generic macros.
16754 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
16755 double) suffix, several have one or more parameters whose corresponding real type is
16756 double. For each such function, except modf, there is a corresponding type-generic
16757 macro.<sup><a href="#note272"><b>272)</b></a></sup> The parameters whose corresponding real type is double in the function
16758 synopsis are generic parameters. Use of the macro invokes a function whose
16759 corresponding real type and type domain are determined by the arguments for the generic
16762 Use of the macro invokes a function whose generic parameters have the corresponding
16763 real type determined as follows:
16764 <ul>
16765 <li> First, if any argument for generic parameters has type long double, the type
16766 determined is long double.
16767 <li> Otherwise, if any argument for generic parameters has type double or is of integer
16768 type, the type determined is double.
16769 <li> Otherwise, the type determined is float.
16770 </ul>
16772 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
16773 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
16774 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
16775 corresponding type-generic macro for fabs and cabs is fabs.
16780 <!--page 348 -->
16781 <pre>
16783 function function macro
16785 acos cacos acos
16786 asin casin asin
16787 atan catan atan
16788 acosh cacosh acosh
16789 asinh casinh asinh
16790 atanh catanh atanh
16791 cos ccos cos
16792 sin csin sin
16793 tan ctan tan
16794 cosh ccosh cosh
16795 sinh csinh sinh
16796 tanh ctanh tanh
16797 exp cexp exp
16798 log clog log
16799 pow cpow pow
16800 sqrt csqrt sqrt
16801 fabs cabs fabs
16802 </pre>
16803 If at least one argument for a generic parameter is complex, then use of the macro invokes
16804 a complex function; otherwise, use of the macro invokes a real function.
16806 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
16807 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
16808 name as the function. These type-generic macros are:
16809 <pre>
16810 atan2 fma llround remainder
16811 cbrt fmax log10 remquo
16812 ceil fmin log1p rint
16813 copysign fmod log2 round
16814 erf frexp logb scalbn
16815 erfc hypot lrint scalbln
16816 exp2 ilogb lround tgamma
16817 expm1 ldexp nearbyint trunc
16818 fdim lgamma nextafter
16819 floor llrint nexttoward
16820 </pre>
16821 If all arguments for generic parameters are real, then use of the macro invokes a real
16822 function; otherwise, use of the macro results in undefined behavior.
16824 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
16825 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
16826 function. These type-generic macros are:
16827 <!--page 349 -->
16828 <pre>
16829 carg conj creal
16830 cimag cproj
16831 </pre>
16832 Use of the macro with any real or complex argument invokes a complex function.
16834 EXAMPLE With the declarations
16835 <pre>
16837 int n;
16838 float f;
16839 double d;
16840 long double ld;
16841 float complex fc;
16842 double complex dc;
16843 long double complex ldc;
16844 </pre>
16845 functions invoked by use of type-generic macros are shown in the following table:
16846 <!--page 350 -->
16847 <pre>
16848 macro use invokes
16850 exp(n) exp(n), the function
16851 acosh(f) acoshf(f)
16852 sin(d) sin(d), the function
16853 atan(ld) atanl(ld)
16854 log(fc) clogf(fc)
16855 sqrt(dc) csqrt(dc)
16856 pow(ldc, f) cpowl(ldc, f)
16857 remainder(n, n) remainder(n, n), the function
16858 nextafter(d, f) nextafter(d, f), the function
16859 nexttoward(f, ld) nexttowardf(f, ld)
16860 copysign(n, ld) copysignl(n, ld)
16861 ceil(fc) undefined behavior
16862 rint(dc) undefined behavior
16863 fmax(ldc, ld) undefined behavior
16864 carg(n) carg(n), the function
16865 cproj(f) cprojf(f)
16866 creal(d) creal(d), the function
16867 cimag(ld) cimagl(ld)
16868 fabs(fc) cabsf(fc)
16869 carg(dc) carg(dc), the function
16870 cproj(ldc) cprojl(ldc)
16871 </pre>
16874 <p><small><a name="note272" href="#note272">272)</a> Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
16875 make available the corresponding ordinary function.
16876 </small>
16877 <p><small><a name="note273" href="#note273">273)</a> If the type of the argument is not compatible with the type of the parameter for the selected function,
16878 the behavior is undefined.
16879 </small>
16885 The header <a href="#7.23"><time.h></a> defines two macros, and declares several types and functions for
16886 manipulating time. Many functions deal with a calendar time that represents the current
16887 date (according to the Gregorian calendar) and time. Some functions deal with local
16888 time, which is the calendar time expressed for some specific time zone, and with Daylight
16889 Saving Time, which is a temporary change in the algorithm for determining local time.
16890 The local time zone and Daylight Saving Time are implementation-defined.
16893 <pre>
16894 CLOCKS_PER_SEC
16895 </pre>
16896 which expands to an expression with type clock_t (described below) that is the
16897 number per second of the value returned by the clock function.
16900 <pre>
16901 clock_t
16902 </pre>
16903 and
16904 <pre>
16905 time_t
16906 </pre>
16907 which are arithmetic types capable of representing times; and
16908 <pre>
16909 struct tm
16910 </pre>
16911 which holds the components of a calendar time, called the broken-down time.
16913 The range and precision of times representable in clock_t and time_t are
16914 implementation-defined. The tm structure shall contain at least the following members,
16915 in any order. The semantics of the members and their normal ranges are expressed in the
16917 <pre>
16923 int tm_year; // years since 1900
16926 int tm_isdst; // Daylight Saving Time flag
16927 </pre>
16931 <!--page 351 -->
16932 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
16933 Saving Time is not in effect, and negative if the information is not available.
16936 <p><small><a name="note274" href="#note274">274)</a> The range [0, 60] for tm_sec allows for a positive leap second.
16937 </small>
16944 <pre>
16946 clock_t clock(void);
16947 </pre>
16950 The clock function determines the processor time used.
16953 The clock function returns the implementation's best approximation to the processor
16954 time used by the program since the beginning of an implementation-defined era related
16955 only to the program invocation. To determine the time in seconds, the value returned by
16956 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
16957 the processor time used is not available or its value cannot be represented, the function
16961 <p><small><a name="note275" href="#note275">275)</a> In order to measure the time spent in a program, the clock function should be called at the start of
16962 the program and its return value subtracted from the value returned by subsequent calls.
16963 </small>
16968 <pre>
16970 double difftime(time_t time1, time_t time0);
16971 </pre>
16974 The difftime function computes the difference between two calendar times: time1 -
16975 time0.
16978 The difftime function returns the difference expressed in seconds as a double.
16983 <!--page 352 -->
16988 <pre>
16990 time_t mktime(struct tm *timeptr);
16991 </pre>
16994 The mktime function converts the broken-down time, expressed as local time, in the
16995 structure pointed to by timeptr into a calendar time value with the same encoding as
16996 that of the values returned by the time function. The original values of the tm_wday
16997 and tm_yday components of the structure are ignored, and the original values of the
16998 other components are not restricted to the ranges indicated above.<sup><a href="#note276"><b>276)</b></a></sup> On successful
16999 completion, the values of the tm_wday and tm_yday components of the structure are
17000 set appropriately, and the other components are set to represent the specified calendar
17001 time, but with their values forced to the ranges indicated above; the final value of
17002 tm_mday is not set until tm_mon and tm_year are determined.
17005 The mktime function returns the specified calendar time encoded as a value of type
17006 time_t. If the calendar time cannot be represented, the function returns the value
17007 (time_t)(-1).
17010 <pre>
17013 static const char *const wday[] = {
17016 };
17017 struct tm time_str;
17018 /* ... */
17019 </pre>
17024 <!--page 353 -->
17025 <pre>
17028 time_str.tm_mday = 4;
17029 time_str.tm_hour = 0;
17030 time_str.tm_min = 0;
17031 time_str.tm_sec = 1;
17032 time_str.tm_isdst = -1;
17034 time_str.tm_wday = 7;
17035 printf("%s\n", wday[time_str.tm_wday]);
17036 </pre>
17040 <p><small><a name="note276" href="#note276">276)</a> Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
17041 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
17042 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
17043 </small>
17048 <pre>
17050 time_t time(time_t *timer);
17051 </pre>
17054 The time function determines the current calendar time. The encoding of the value is
17055 unspecified.
17058 The time function returns the implementation's best approximation to the current
17059 calendar time. The value (time_t)(-1) is returned if the calendar time is not
17060 available. If timer is not a null pointer, the return value is also assigned to the object it
17061 points to.
17065 Except for the strftime function, these functions each return a pointer to one of two
17066 types of static objects: a broken-down time structure or an array of char. Execution of
17067 any of the functions that return a pointer to one of these object types may overwrite the
17068 information in any object of the same type pointed to by the value returned from any
17069 previous call to any of them. The implementation shall behave as if no other library
17070 functions call these functions.
17075 <pre>
17077 char *asctime(const struct tm *timeptr);
17078 </pre>
17081 The asctime function converts the broken-down time in the structure pointed to by
17082 timeptr into a string in the form
17083 <!--page 354 -->
17084 <pre>
17086 </pre>
17087 using the equivalent of the following algorithm.
17088 <pre>
17089 char *asctime(const struct tm *timeptr)
17090 {
17093 };
17097 };
17098 static char result[26];
17099 sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
17100 wday_name[timeptr->tm_wday],
17101 mon_name[timeptr->tm_mon],
17105 return result;
17106 }
17107 </pre>
17110 The asctime function returns a pointer to the string.
17115 <pre>
17117 char *ctime(const time_t *timer);
17118 </pre>
17121 The ctime function converts the calendar time pointed to by timer to local time in the
17122 form of a string. It is equivalent to
17123 <pre>
17124 asctime(localtime(timer))
17125 </pre>
17128 The ctime function returns the pointer returned by the asctime function with that
17129 broken-down time as argument.
17131 <!--page 355 -->
17136 <pre>
17138 struct tm *gmtime(const time_t *timer);
17139 </pre>
17142 The gmtime function converts the calendar time pointed to by timer into a broken-
17143 down time, expressed as UTC.
17146 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
17147 specified time cannot be converted to UTC.
17152 <pre>
17154 struct tm *localtime(const time_t *timer);
17155 </pre>
17158 The localtime function converts the calendar time pointed to by timer into a
17159 broken-down time, expressed as local time.
17162 The localtime function returns a pointer to the broken-down time, or a null pointer if
17163 the specified time cannot be converted to local time.
17168 <pre>
17170 size_t strftime(char * restrict s,
17171 size_t maxsize,
17172 const char * restrict format,
17173 const struct tm * restrict timeptr);
17174 </pre>
17177 The strftime function places characters into the array pointed to by s as controlled by
17178 the string pointed to by format. The format shall be a multibyte character sequence,
17179 beginning and ending in its initial shift state. The format string consists of zero or
17180 more conversion specifiers and ordinary multibyte characters. A conversion specifier
17181 consists of a % character, possibly followed by an E or O modifier character (described
17182 below), followed by a character that determines the behavior of the conversion specifier.
17183 All ordinary multibyte characters (including the terminating null character) are copied
17184 <!--page 356 -->
17185 unchanged into the array. If copying takes place between objects that overlap, the
17186 behavior is undefined. No more than maxsize characters are placed into the array.
17188 Each conversion specifier is replaced by appropriate characters as described in the
17189 following list. The appropriate characters are determined using the LC_TIME category
17190 of the current locale and by the values of zero or more members of the broken-down time
17191 structure pointed to by timeptr, as specified in brackets in the description. If any of
17192 the specified values is outside the normal range, the characters stored are unspecified.
17193 <dl>
17198 <dt> %c <dd> is replaced by the locale's appropriate date and time representation. [all specified
17204 <dt> %e <dd> is replaced by the day of the month as a decimal number (1-31); a single digit is
17205 preceded by a space. [tm_mday]
17207 tm_mday]
17211 [tm_year, tm_wday, tm_yday]
17219 <dt> %p <dd> is replaced by the locale's equivalent of the AM/PM designations associated with a
17220 12-hour clock. [tm_hour]
17226 <!--page 357 -->
17227 tm_sec]
17229 is 1. [tm_wday]
17230 <dt> %U <dd> is replaced by the week number of the year (the first Sunday as the first day of week
17235 [tm_wday]
17238 <dt> %x <dd> is replaced by the locale's appropriate date representation. [all specified in <a href="#7.23.1">7.23.1</a>]
17239 <dt> %X <dd> is replaced by the locale's appropriate time representation. [all specified in <a href="#7.23.1">7.23.1</a>]
17241 [tm_year]
17244 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
17245 zone is determinable. [tm_isdst]
17246 <dt> %Z <dd> is replaced by the locale's time zone name or abbreviation, or by no characters if no
17247 time zone is determinable. [tm_isdst]
17249 </dl>
17251 Some conversion specifiers can be modified by the inclusion of an E or O modifier
17252 character to indicate an alternative format or specification. If the alternative format or
17253 specification does not exist for the current locale, the modifier is ignored.
17254 <dl>
17257 representation.
17261 representation.
17263 <dt> %Od <dd>is replaced by the day of the month, using the locale's alternative numeric symbols
17264 (filled as needed with leading zeros, or with leading spaces if there is no alternative
17265 symbol for zero).
17266 <dt> %Oe <dd>is replaced by the day of the month, using the locale's alternative numeric symbols
17267 (filled as needed with leading spaces).
17269 <!--page 358 -->
17270 symbols.
17272 symbols.
17277 representation, where Monday is 1.
17280 symbols.
17282 symbols.
17283 <dt> %OW <dd>is replaced by the week number of the year, using the locale's alternative numeric
17284 symbols.
17285 <dt> %Oy <dd>is replaced by the last 2 digits of the year, using the locale's alternative numeric
17286 symbols.
17287 </dl>
17289 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
17291 which is also the week that includes the first Thursday of the year, and is also the first
17292 week that contains at least four days in the year. If the first Monday of January is the
17297 %V is replaced by 01.
17299 If a conversion specifier is not one of the above, the behavior is undefined.
17301 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
17302 following specifiers are:
17303 <dl>
17314 </dl>
17315 <!--page 359 -->
17318 If the total number of resulting characters including the terminating null character is not
17319 more than maxsize, the strftime function returns the number of characters placed
17320 into the array pointed to by s not including the terminating null character. Otherwise,
17321 zero is returned and the contents of the array are indeterminate.
17322 <!--page 360 -->
17324 <h3><a name="7.24" href="#7.24">7.24 Extended multibyte and wide character utilities <wchar.h></a></h3>
17328 The header <a href="#7.24"><wchar.h></a> declares four data types, one tag, four macros, and many
17332 <pre>
17333 mbstate_t
17334 </pre>
17335 which is an object type other than an array type that can hold the conversion state
17336 information necessary to convert between sequences of multibyte characters and wide
17337 characters;
17338 <pre>
17339 wint_t
17340 </pre>
17341 which is an integer type unchanged by default argument promotions that can hold any
17342 value corresponding to members of the extended character set, as well as at least one
17343 value that does not correspond to any member of the extended character set (see WEOF
17345 <pre>
17346 struct tm
17347 </pre>
17348 which is declared as an incomplete structure type (the contents are described in <a href="#7.23.1">7.23.1</a>).
17352 <pre>
17353 WEOF
17354 </pre>
17355 which expands to a constant expression of type wint_t whose value does not
17356 correspond to any member of the extended character set.<sup><a href="#note279"><b>279)</b></a></sup> It is accepted (and returned)
17357 by several functions in this subclause to indicate end-of-file, that is, no more input from a
17358 stream. It is also used as a wide character value that does not correspond to any member
17359 of the extended character set.
17361 The functions declared are grouped as follows:
17362 <ul>
17363 <li> Functions that perform input and output of wide characters, or multibyte characters,
17364 or both;
17365 <li> Functions that provide wide string numeric conversion;
17366 <li> Functions that perform general wide string manipulation;
17369 <!--page 361 -->
17370 <li> Functions for wide string date and time conversion; and
17371 <li> Functions that provide extended capabilities for conversion between multibyte and
17372 wide character sequences.
17373 </ul>
17375 Unless explicitly stated otherwise, if the execution of a function described in this
17376 subclause causes copying to take place between objects that overlap, the behavior is
17377 undefined.
17380 <p><small><a name="note277" href="#note277">277)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17381 </small>
17382 <p><small><a name="note278" href="#note278">278)</a> wchar_t and wint_t can be the same integer type.
17383 </small>
17384 <p><small><a name="note279" href="#note279">279)</a> The value of the macro WEOF may differ from that of EOF and need not be negative.
17385 </small>
17387 <h4><a name="7.24.2" href="#7.24.2">7.24.2 Formatted wide character input/output functions</a></h4>
17389 The formatted wide character input/output functions shall behave as if there is a sequence
17390 point after the actions associated with each specifier.<sup><a href="#note280"><b>280)</b></a></sup>
17393 <p><small><a name="note280" href="#note280">280)</a> The fwprintf functions perform writes to memory for the %n specifier.
17394 </small>
17399 <pre>
17402 int fwprintf(FILE * restrict stream,
17403 const wchar_t * restrict format, ...);
17404 </pre>
17407 The fwprintf function writes output to the stream pointed to by stream, under
17408 control of the wide string pointed to by format that specifies how subsequent arguments
17409 are converted for output. If there are insufficient arguments for the format, the behavior
17410 is undefined. If the format is exhausted while arguments remain, the excess arguments
17411 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
17412 when the end of the format string is encountered.
17414 The format is composed of zero or more directives: ordinary wide characters (not %),
17415 which are copied unchanged to the output stream; and conversion specifications, each of
17416 which results in fetching zero or more subsequent arguments, converting them, if
17417 applicable, according to the corresponding conversion specifier, and then writing the
17418 result to the output stream.
17420 Each conversion specification is introduced by the wide character %. After the %, the
17421 following appear in sequence:
17422 <ul>
17423 <li> Zero or more flags (in any order) that modify the meaning of the conversion
17424 specification.
17425 <li> An optional minimum field width. If the converted value has fewer wide characters
17426 than the field width, it is padded with spaces (by default) on the left (or right, if the
17429 <!--page 362 -->
17430 left adjustment flag, described later, has been given) to the field width. The field
17431 width takes the form of an asterisk * (described later) or a nonnegative decimal
17433 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
17434 o, u, x, and X conversions, the number of digits to appear after the decimal-point
17435 wide character for a, A, e, E, f, and F conversions, the maximum number of
17436 significant digits for the g and G conversions, or the maximum number of wide
17437 characters to be written for s conversions. The precision takes the form of a period
17438 (.) followed either by an asterisk * (described later) or by an optional decimal
17439 integer; if only the period is specified, the precision is taken as zero. If a precision
17440 appears with any other conversion specifier, the behavior is undefined.
17441 <li> An optional length modifier that specifies the size of the argument.
17442 <li> A conversion specifier wide character that specifies the type of conversion to be
17443 applied.
17444 </ul>
17446 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
17447 this case, an int argument supplies the field width or precision. The arguments
17448 specifying field width, or precision, or both, shall appear (in that order) before the
17449 argument (if any) to be converted. A negative field width argument is taken as a - flag
17450 followed by a positive field width. A negative precision argument is taken as if the
17451 precision were omitted.
17453 The flag wide characters and their meanings are:
17454 <dl>
17455 <dt> - <dd> The result of the conversion is left-justified within the field. (It is right-justified if
17456 this flag is not specified.)
17458 begins with a sign only when a negative value is converted if this flag is not
17460 <dt> space<dd> If the first wide character of a signed conversion is not a sign, or if a signed
17461 conversion results in no wide characters, a space is prefixed to the result. If the
17462 space and + flags both appear, the space flag is ignored.
17463 <dt> # <dd> The result is converted to an ''alternative form''. For o conversion, it increases
17464 the precision, if and only if necessary, to force the first digit of the result to be a
17468 <!--page 363 -->
17469 and G conversions, the result of converting a floating-point number always
17470 contains a decimal-point wide character, even if no digits follow it. (Normally, a
17471 decimal-point wide character appears in the result of these conversions only if a
17472 digit follows it.) For g and G conversions, trailing zeros are not removed from the
17473 result. For other conversions, the behavior is undefined.
17475 (following any indication of sign or base) are used to pad to the field width rather
17476 than performing space padding, except when converting an infinity or NaN. If the
17478 conversions, if a precision is specified, the 0 flag is ignored. For other
17479 conversions, the behavior is undefined.
17480 </dl>
17482 The length modifiers and their meanings are:
17483 <dl>
17485 signed char or unsigned char argument (the argument will have
17486 been promoted according to the integer promotions, but its value shall be
17487 converted to signed char or unsigned char before printing); or that
17488 a following n conversion specifier applies to a pointer to a signed char
17489 argument.
17491 short int or unsigned short int argument (the argument will
17492 have been promoted according to the integer promotions, but its value shall
17493 be converted to short int or unsigned short int before printing);
17494 or that a following n conversion specifier applies to a pointer to a short
17495 int argument.
17496 <dt> l (ell)<dd> Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
17497 long int or unsigned long int argument; that a following n
17498 conversion specifier applies to a pointer to a long int argument; that a
17499 following c conversion specifier applies to a wint_t argument; that a
17500 following s conversion specifier applies to a pointer to a wchar_t
17501 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
17502 specifier.
17503 <dt> ll (ell-ell)<dd> Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
17504 long long int or unsigned long long int argument; or that a
17505 following n conversion specifier applies to a pointer to a long long int
17506 argument.
17508 <!--page 364 -->
17509 an intmax_t or uintmax_t argument; or that a following n conversion
17510 specifier applies to a pointer to an intmax_t argument.
17512 size_t or the corresponding signed integer type argument; or that a
17513 following n conversion specifier applies to a pointer to a signed integer type
17514 corresponding to size_t argument.
17516 ptrdiff_t or the corresponding unsigned integer type argument; or that a
17517 following n conversion specifier applies to a pointer to a ptrdiff_t
17518 argument.
17520 applies to a long double argument.
17521 </dl>
17522 If a length modifier appears with any conversion specifier other than as specified above,
17523 the behavior is undefined.
17525 The conversion specifiers and their meanings are:
17526 <dl>
17528 precision specifies the minimum number of digits to appear; if the value
17529 being converted can be represented in fewer digits, it is expanded with
17530 leading zeros. The default precision is 1. The result of converting a zero
17531 value with a precision of zero is no wide characters.
17533 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
17534 letters abcdef are used for x conversion and the letters ABCDEF for X
17535 conversion. The precision specifies the minimum number of digits to appear;
17536 if the value being converted can be represented in fewer digits, it is expanded
17537 with leading zeros. The default precision is 1. The result of converting a
17538 zero value with a precision of zero is no wide characters.
17540 <!--page 365 -->
17541 decimal notation in the style [-]ddd.ddd, where the number of digits after
17542 the decimal-point wide character is equal to the precision specification. If the
17543 precision is missing, it is taken as 6; if the precision is zero and the # flag is
17544 not specified, no decimal-point wide character appears. If a decimal-point
17545 wide character appears, at least one digit appears before it. The value is
17546 rounded to the appropriate number of digits.
17547 A double argument representing an infinity is converted in one of the styles
17548 [-]inf or [-]infinity -- which style is implementation-defined. A
17549 double argument representing a NaN is converted in one of the styles
17550 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
17551 any n-wchar-sequence, is implementation-defined. The F conversion
17552 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
17555 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
17556 argument is nonzero) before the decimal-point wide character and the number
17557 of digits after it is equal to the precision; if the precision is missing, it is taken
17558 as 6; if the precision is zero and the # flag is not specified, no decimal-point
17559 wide character appears. The value is rounded to the appropriate number of
17560 digits. The E conversion specifier produces a number with E instead of e
17561 introducing the exponent. The exponent always contains at least two digits,
17562 and only as many more digits as necessary to represent the exponent. If the
17563 value is zero, the exponent is zero.
17564 A double argument representing an infinity or NaN is converted in the style
17565 of an f or F conversion specifier.
17567 style f or e (or in style F or E in the case of a G conversion specifier),
17568 depending on the value converted and the precision. Let P equal the
17570 Then, if a conversion with style E would have an exponent of X :
17571 <ul>
17573 P - (X + 1).
17575 </ul>
17576 Finally, unless the # flag is used, any trailing zeros are removed from the
17577 fractional portion of the result and the decimal-point wide character is
17578 removed if there is no fractional portion remaining.
17579 A double argument representing an infinity or NaN is converted in the style
17580 of an f or F conversion specifier.
17582 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
17583 nonzero if the argument is a normalized floating-point number and is
17584 otherwise unspecified) before the decimal-point wide character<sup><a href="#note284"><b>284)</b></a></sup> and the
17585 number of hexadecimal digits after it is equal to the precision; if the precision
17586 is missing and FLT_RADIX is a power of 2, then the precision is sufficient
17587 <!--page 366 -->
17588 for an exact representation of the value; if the precision is missing and
17589 FLT_RADIX is not a power of 2, then the precision is sufficient to
17590 distinguish<sup><a href="#note285"><b>285)</b></a></sup> values of type double, except that trailing zeros may be
17591 omitted; if the precision is zero and the # flag is not specified, no decimal-
17592 point wide character appears. The letters abcdef are used for a conversion
17593 and the letters ABCDEF for A conversion. The A conversion specifier
17594 produces a number with X and P instead of x and p. The exponent always
17595 contains at least one digit, and only as many more digits as necessary to
17596 represent the decimal exponent of 2. If the value is zero, the exponent is
17597 zero.
17598 A double argument representing an infinity or NaN is converted in the style
17599 of an f or F conversion specifier.
17601 character as if by calling btowc and the resulting wide character is written.
17602 If an l length modifier is present, the wint_t argument is converted to
17603 wchar_t and written.
17604 <dt> s <dd> If no l length modifier is present, the argument shall be a pointer to the initial
17605 element of a character array containing a multibyte character sequence
17606 beginning in the initial shift state. Characters from the array are converted as
17607 if by repeated calls to the mbrtowc function, with the conversion state
17608 described by an mbstate_t object initialized to zero before the first
17609 multibyte character is converted, and written up to (but not including) the
17610 terminating null wide character. If the precision is specified, no more than
17611 that many wide characters are written. If the precision is not specified or is
17612 greater than the size of the converted array, the converted array shall contain a
17613 null wide character.
17614 If an l length modifier is present, the argument shall be a pointer to the initial
17615 element of an array of wchar_t type. Wide characters from the array are
17616 written up to (but not including) a terminating null wide character. If the
17617 precision is specified, no more than that many wide characters are written. If
17618 the precision is not specified or is greater than the size of the array, the array
17619 shall contain a null wide character.
17621 converted to a sequence of printing wide characters, in an implementation-
17622 <!--page 367 -->
17623 defined manner.
17625 number of wide characters written to the output stream so far by this call to
17626 fwprintf. No argument is converted, but one is consumed. If the
17627 conversion specification includes any flags, a field width, or a precision, the
17628 behavior is undefined.
17630 conversion specification shall be %%.
17631 </dl>
17633 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note286"><b>286)</b></a></sup> If any argument is
17634 not the correct type for the corresponding conversion specification, the behavior is
17635 undefined.
17637 In no case does a nonexistent or small field width cause truncation of a field; if the result
17638 of a conversion is wider than the field width, the field is expanded to contain the
17639 conversion result.
17641 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
17642 to a hexadecimal floating number with the given precision.
17645 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
17646 representable in the given precision, the result should be one of the two adjacent numbers
17647 in hexadecimal floating style with the given precision, with the extra stipulation that the
17648 error should have a correct sign for the current rounding direction.
17650 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
17651 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note287"><b>287)</b></a></sup> If the number of
17652 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
17653 representable with DECIMAL_DIG digits, then the result should be an exact
17654 representation with trailing zeros. Otherwise, the source value is bounded by two
17655 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
17656 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
17657 the error should have a correct sign for the current rounding direction.
17660 The fwprintf function returns the number of wide characters transmitted, or a negative
17661 value if an output or encoding error occurred.
17663 <!--page 368 -->
17666 The number of wide characters that can be produced by any single conversion shall be at
17667 least 4095.
17669 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
17670 places:
17671 <pre>
17675 /* ... */
17676 wchar_t *weekday, *month; // pointers to wide strings
17677 int day, hour, min;
17678 fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
17679 weekday, month, day, hour, min);
17681 </pre>
17683 <p><b> Forward references</b>: the btowc function (<a href="#7.24.6.1.1">7.24.6.1.1</a>), the mbrtowc function
17687 <p><small><a name="note281" href="#note281">281)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
17688 </small>
17689 <p><small><a name="note282" href="#note282">282)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
17690 include a minus sign.
17691 </small>
17692 <p><small><a name="note283" href="#note283">283)</a> When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
17693 meaning; the # and 0 flag wide characters have no effect.
17694 </small>
17695 <p><small><a name="note284" href="#note284">284)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
17696 character so that subsequent digits align to nibble (4-bit) boundaries.
17697 </small>
17698 <p><small><a name="note285" href="#note285">285)</a> The precision p is sufficient to distinguish values of the source type if 16<sup>p-1</sup> > b n where b is
17699 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
17700 might suffice depending on the implementation's scheme for determining the digit to the left of the
17701 decimal-point wide character.
17702 </small>
17703 <p><small><a name="note286" href="#note286">286)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17704 </small>
17705 <p><small><a name="note287" href="#note287">287)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
17706 given format specifier. The number of significant digits is determined by the format specifier, and in
17707 the case of fixed-point conversion by the source value as well.
17708 </small>
17713 <pre>
17716 int fwscanf(FILE * restrict stream,
17717 const wchar_t * restrict format, ...);
17718 </pre>
17721 The fwscanf function reads input from the stream pointed to by stream, under
17722 control of the wide string pointed to by format that specifies the admissible input
17723 sequences and how they are to be converted for assignment, using subsequent arguments
17724 as pointers to the objects to receive the converted input. If there are insufficient
17725 arguments for the format, the behavior is undefined. If the format is exhausted while
17726 arguments remain, the excess arguments are evaluated (as always) but are otherwise
17727 ignored.
17729 The format is composed of zero or more directives: one or more white-space wide
17730 characters, an ordinary wide character (neither % nor a white-space wide character), or a
17731 conversion specification. Each conversion specification is introduced by the wide
17732 character %. After the %, the following appear in sequence:
17733 <ul>
17734 <li> An optional assignment-suppressing wide character *.
17735 <li> An optional decimal integer greater than zero that specifies the maximum field width
17736 (in wide characters).
17737 <!--page 369 -->
17738 <li> An optional length modifier that specifies the size of the receiving object.
17739 <li> A conversion specifier wide character that specifies the type of conversion to be
17740 applied.
17741 </ul>
17743 The fwscanf function executes each directive of the format in turn. If a directive fails,
17744 as detailed below, the function returns. Failures are described as input failures (due to the
17745 occurrence of an encoding error or the unavailability of input characters), or matching
17746 failures (due to inappropriate input).
17748 A directive composed of white-space wide character(s) is executed by reading input up to
17749 the first non-white-space wide character (which remains unread), or until no more wide
17750 characters can be read.
17752 A directive that is an ordinary wide character is executed by reading the next wide
17753 character of the stream. If that wide character differs from the directive, the directive
17754 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
17755 of-file, an encoding error, or a read error prevents a wide character from being read, the
17756 directive fails.
17758 A directive that is a conversion specification defines a set of matching input sequences, as
17759 described below for each specifier. A conversion specification is executed in the
17760 following steps:
17762 Input white-space wide characters (as specified by the iswspace function) are skipped,
17763 unless the specification includes a [, c, or n specifier.<sup><a href="#note288"><b>288)</b></a></sup>
17765 An input item is read from the stream, unless the specification includes an n specifier. An
17766 input item is defined as the longest sequence of input wide characters which does not
17767 exceed any specified field width and which is, or is a prefix of, a matching input
17768 sequence.<sup><a href="#note289"><b>289)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
17769 length of the input item is zero, the execution of the directive fails; this condition is a
17770 matching failure unless end-of-file, an encoding error, or a read error prevented input
17771 from the stream, in which case it is an input failure.
17773 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
17774 count of input wide characters) is converted to a type appropriate to the conversion
17775 specifier. If the input item is not a matching sequence, the execution of the directive fails:
17776 this condition is a matching failure. Unless assignment suppression was indicated by a *,
17777 the result of the conversion is placed in the object pointed to by the first argument
17778 following the format argument that has not already received a conversion result. If this
17781 <!--page 370 -->
17782 object does not have an appropriate type, or if the result of the conversion cannot be
17783 represented in the object, the behavior is undefined.
17785 The length modifiers and their meanings are:
17786 <dl>
17788 to an argument with type pointer to signed char or unsigned char.
17790 to an argument with type pointer to short int or unsigned short
17791 int.
17792 <dt> l (ell) <dd> Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17793 to an argument with type pointer to long int or unsigned long
17794 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
17795 an argument with type pointer to double; or that a following c, s, or [
17796 conversion specifier applies to an argument with type pointer to wchar_t.
17797 <dt> ll (ell-ell)<dd> Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17798 to an argument with type pointer to long long int or unsigned
17799 long long int.
17801 to an argument with type pointer to intmax_t or uintmax_t.
17803 to an argument with type pointer to size_t or the corresponding signed
17804 integer type.
17806 to an argument with type pointer to ptrdiff_t or the corresponding
17807 unsigned integer type.
17809 applies to an argument with type pointer to long double.
17810 </dl>
17811 If a length modifier appears with any conversion specifier other than as specified above,
17812 the behavior is undefined.
17814 The conversion specifiers and their meanings are:
17815 <dl>
17817 expected for the subject sequence of the wcstol function with the value 10
17818 for the base argument. The corresponding argument shall be a pointer to
17819 signed integer.
17821 <!--page 371 -->
17822 for the subject sequence of the wcstol function with the value 0 for the
17823 base argument. The corresponding argument shall be a pointer to signed
17824 integer.
17826 expected for the subject sequence of the wcstoul function with the value 8
17827 for the base argument. The corresponding argument shall be a pointer to
17828 unsigned integer.
17830 expected for the subject sequence of the wcstoul function with the value 10
17831 for the base argument. The corresponding argument shall be a pointer to
17832 unsigned integer.
17834 as expected for the subject sequence of the wcstoul function with the value
17835 16 for the base argument. The corresponding argument shall be a pointer to
17836 unsigned integer.
17838 format is the same as expected for the subject sequence of the wcstod
17839 function. The corresponding argument shall be a pointer to floating.
17841 field width (1 if no field width is present in the directive).
17842 If no l length modifier is present, characters from the input field are
17843 converted as if by repeated calls to the wcrtomb function, with the
17844 conversion state described by an mbstate_t object initialized to zero
17845 before the first wide character is converted. The corresponding argument
17846 shall be a pointer to the initial element of a character array large enough to
17847 accept the sequence. No null character is added.
17848 If an l length modifier is present, the corresponding argument shall be a
17849 pointer to the initial element of an array of wchar_t large enough to accept
17850 the sequence. No null wide character is added.
17852 <!--page 372 -->
17853 If no l length modifier is present, characters from the input field are
17854 converted as if by repeated calls to the wcrtomb function, with the
17855 conversion state described by an mbstate_t object initialized to zero
17856 before the first wide character is converted. The corresponding argument
17857 shall be a pointer to the initial element of a character array large enough to
17858 accept the sequence and a terminating null character, which will be added
17859 automatically.
17860 If an l length modifier is present, the corresponding argument shall be a
17861 pointer to the initial element of an array of wchar_t large enough to accept
17862 the sequence and the terminating null wide character, which will be added
17863 automatically.
17865 characters (the scanset).
17866 If no l length modifier is present, characters from the input field are
17867 converted as if by repeated calls to the wcrtomb function, with the
17868 conversion state described by an mbstate_t object initialized to zero
17869 before the first wide character is converted. The corresponding argument
17870 shall be a pointer to the initial element of a character array large enough to
17871 accept the sequence and a terminating null character, which will be added
17872 automatically.
17873 If an l length modifier is present, the corresponding argument shall be a
17874 pointer to the initial element of an array of wchar_t large enough to accept
17875 the sequence and the terminating null wide character, which will be added
17876 automatically.
17877 The conversion specifier includes all subsequent wide characters in the
17878 format string, up to and including the matching right bracket (]). The wide
17879 characters between the brackets (the scanlist) compose the scanset, unless the
17880 wide character after the left bracket is a circumflex (^), in which case the
17881 scanset contains all wide characters that do not appear in the scanlist between
17882 the circumflex and the right bracket. If the conversion specifier begins with
17883 [] or [^], the right bracket wide character is in the scanlist and the next
17884 following right bracket wide character is the matching right bracket that ends
17885 the specification; otherwise the first following right bracket wide character is
17886 the one that ends the specification. If a - wide character is in the scanlist and
17887 is not the first, nor the second where the first wide character is a ^, nor the
17888 last character, the behavior is implementation-defined.
17890 same as the set of sequences that may be produced by the %p conversion of
17891 the fwprintf function. The corresponding argument shall be a pointer to a
17892 pointer to void. The input item is converted to a pointer value in an
17893 implementation-defined manner. If the input item is a value converted earlier
17894 during the same program execution, the pointer that results shall compare
17895 equal to that value; otherwise the behavior of the %p conversion is undefined.
17897 <!--page 373 -->
17898 signed integer into which is to be written the number of wide characters read
17899 from the input stream so far by this call to the fwscanf function. Execution
17900 of a %n directive does not increment the assignment count returned at the
17901 completion of execution of the fwscanf function. No argument is
17902 converted, but one is consumed. If the conversion specification includes an
17903 assignment-suppressing wide character or a field width, the behavior is
17904 undefined.
17906 complete conversion specification shall be %%.
17907 </dl>
17909 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note290"><b>290)</b></a></sup>
17911 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
17912 respectively, a, e, f, g, and x.
17914 Trailing white space (including new-line wide characters) is left unread unless matched
17915 by a directive. The success of literal matches and suppressed assignments is not directly
17916 determinable other than via the %n directive.
17919 The fwscanf function returns the value of the macro EOF if an input failure occurs
17920 before any conversion. Otherwise, the function returns the number of input items
17921 assigned, which can be fewer than provided for, or even zero, in the event of an early
17922 matching failure.
17924 EXAMPLE 1 The call:
17925 <pre>
17928 /* ... */
17929 int n, i; float x; wchar_t name[50];
17931 </pre>
17932 with the input line:
17933 <pre>
17934 25 54.32E-1 thompson
17935 </pre>
17936 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
17937 thompson\0.
17940 EXAMPLE 2 The call:
17941 <pre>
17944 /* ... */
17945 int i; float x; double y;
17947 </pre>
17948 with input:
17949 <pre>
17950 56789 0123 56a72
17951 </pre>
17952 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
17953 56.0. The next wide character read from the input stream will be a.
17956 <!--page 374 -->
17957 <p><b> Forward references</b>: the wcstod, wcstof, and wcstold functions (<a href="#7.24.4.1.1">7.24.4.1.1</a>), the
17958 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.24.4.1.2">7.24.4.1.2</a>), the wcrtomb
17962 <p><small><a name="note288" href="#note288">288)</a> These white-space wide characters are not counted against a specified field width.
17963 </small>
17964 <p><small><a name="note289" href="#note289">289)</a> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
17965 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
17966 </small>
17967 <p><small><a name="note290" href="#note290">290)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17968 </small>
17973 <pre>
17975 int swprintf(wchar_t * restrict s,
17976 size_t n,
17977 const wchar_t * restrict format, ...);
17978 </pre>
17981 The swprintf function is equivalent to fwprintf, except that the argument s
17982 specifies an array of wide characters into which the generated output is to be written,
17983 rather than written to a stream. No more than n wide characters are written, including a
17984 terminating null wide character, which is always added (unless n is zero).
17987 The swprintf function returns the number of wide characters written in the array, not
17988 counting the terminating null wide character, or a negative value if an encoding error
17989 occurred or if n or more wide characters were requested to be written.
17994 <pre>
17996 int swscanf(const wchar_t * restrict s,
17997 const wchar_t * restrict format, ...);
17998 </pre>
18001 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
18002 wide string from which the input is to be obtained, rather than from a stream. Reaching
18003 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
18004 function.
18007 The swscanf function returns the value of the macro EOF if an input failure occurs
18008 before any conversion. Otherwise, the swscanf function returns the number of input
18009 items assigned, which can be fewer than provided for, or even zero, in the event of an
18010 early matching failure.
18011 <!--page 375 -->
18016 <pre>
18020 int vfwprintf(FILE * restrict stream,
18021 const wchar_t * restrict format,
18022 va_list arg);
18023 </pre>
18026 The vfwprintf function is equivalent to fwprintf, with the variable argument list
18027 replaced by arg, which shall have been initialized by the va_start macro (and
18028 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
18032 The vfwprintf function returns the number of wide characters transmitted, or a
18033 negative value if an output or encoding error occurred.
18035 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
18036 routine.
18037 <pre>
18041 void error(char *function_name, wchar_t *format, ...)
18042 {
18043 va_list args;
18044 va_start(args, format);
18045 // print out name of function causing error
18046 fwprintf(stderr, L"ERROR in %s: ", function_name);
18047 // print out remainder of message
18048 vfwprintf(stderr, format, args);
18049 va_end(args);
18050 }
18051 </pre>
18056 <!--page 376 -->
18059 <p><small><a name="note291" href="#note291">291)</a> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
18060 invoke the va_arg macro, the value of arg after the return is indeterminate.
18061 </small>
18066 <pre>
18070 int vfwscanf(FILE * restrict stream,
18071 const wchar_t * restrict format,
18072 va_list arg);
18073 </pre>
18076 The vfwscanf function is equivalent to fwscanf, with the variable argument list
18077 replaced by arg, which shall have been initialized by the va_start macro (and
18078 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
18082 The vfwscanf function returns the value of the macro EOF if an input failure occurs
18083 before any conversion. Otherwise, the vfwscanf function returns the number of input
18084 items assigned, which can be fewer than provided for, or even zero, in the event of an
18085 early matching failure.
18090 <pre>
18093 int vswprintf(wchar_t * restrict s,
18094 size_t n,
18095 const wchar_t * restrict format,
18096 va_list arg);
18097 </pre>
18100 The vswprintf function is equivalent to swprintf, with the variable argument list
18101 replaced by arg, which shall have been initialized by the va_start macro (and
18102 possibly subsequent va_arg calls). The vswprintf function does not invoke the
18106 The vswprintf function returns the number of wide characters written in the array, not
18107 counting the terminating null wide character, or a negative value if an encoding error
18108 occurred or if n or more wide characters were requested to be generated.
18109 <!--page 377 -->
18114 <pre>
18117 int vswscanf(const wchar_t * restrict s,
18118 const wchar_t * restrict format,
18119 va_list arg);
18120 </pre>
18123 The vswscanf function is equivalent to swscanf, with the variable argument list
18124 replaced by arg, which shall have been initialized by the va_start macro (and
18125 possibly subsequent va_arg calls). The vswscanf function does not invoke the
18129 The vswscanf function returns the value of the macro EOF if an input failure occurs
18130 before any conversion. Otherwise, the vswscanf function returns the number of input
18131 items assigned, which can be fewer than provided for, or even zero, in the event of an
18132 early matching failure.
18137 <pre>
18140 int vwprintf(const wchar_t * restrict format,
18141 va_list arg);
18142 </pre>
18145 The vwprintf function is equivalent to wprintf, with the variable argument list
18146 replaced by arg, which shall have been initialized by the va_start macro (and
18147 possibly subsequent va_arg calls). The vwprintf function does not invoke the
18151 The vwprintf function returns the number of wide characters transmitted, or a negative
18152 value if an output or encoding error occurred.
18153 <!--page 378 -->
18158 <pre>
18161 int vwscanf(const wchar_t * restrict format,
18162 va_list arg);
18163 </pre>
18166 The vwscanf function is equivalent to wscanf, with the variable argument list
18167 replaced by arg, which shall have been initialized by the va_start macro (and
18168 possibly subsequent va_arg calls). The vwscanf function does not invoke the
18172 The vwscanf function returns the value of the macro EOF if an input failure occurs
18173 before any conversion. Otherwise, the vwscanf function returns the number of input
18174 items assigned, which can be fewer than provided for, or even zero, in the event of an
18175 early matching failure.
18180 <pre>
18182 int wprintf(const wchar_t * restrict format, ...);
18183 </pre>
18186 The wprintf function is equivalent to fwprintf with the argument stdout
18187 interposed before the arguments to wprintf.
18190 The wprintf function returns the number of wide characters transmitted, or a negative
18191 value if an output or encoding error occurred.
18196 <pre>
18198 int wscanf(const wchar_t * restrict format, ...);
18199 </pre>
18202 The wscanf function is equivalent to fwscanf with the argument stdin interposed
18203 before the arguments to wscanf.
18204 <!--page 379 -->
18207 The wscanf function returns the value of the macro EOF if an input failure occurs
18208 before any conversion. Otherwise, the wscanf function returns the number of input
18209 items assigned, which can be fewer than provided for, or even zero, in the event of an
18210 early matching failure.
18217 <pre>
18220 wint_t fgetwc(FILE *stream);
18221 </pre>
18224 If the end-of-file indicator for the input stream pointed to by stream is not set and a
18225 next wide character is present, the fgetwc function obtains that wide character as a
18226 wchar_t converted to a wint_t and advances the associated file position indicator for
18227 the stream (if defined).
18230 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
18231 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
18232 the fgetwc function returns the next wide character from the input stream pointed to by
18233 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
18234 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
18235 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note292"><b>292)</b></a></sup>
18238 <p><small><a name="note292" href="#note292">292)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
18239 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
18240 </small>
18245 <pre>
18248 wchar_t *fgetws(wchar_t * restrict s,
18249 int n, FILE * restrict stream);
18250 </pre>
18253 The fgetws function reads at most one less than the number of wide characters
18254 specified by n from the stream pointed to by stream into the array pointed to by s. No
18257 <!--page 380 -->
18258 additional wide characters are read after a new-line wide character (which is retained) or
18259 after end-of-file. A null wide character is written immediately after the last wide
18260 character read into the array.
18263 The fgetws function returns s if successful. If end-of-file is encountered and no
18264 characters have been read into the array, the contents of the array remain unchanged and a
18265 null pointer is returned. If a read or encoding error occurs during the operation, the array
18266 contents are indeterminate and a null pointer is returned.
18271 <pre>
18274 wint_t fputwc(wchar_t c, FILE *stream);
18275 </pre>
18278 The fputwc function writes the wide character specified by c to the output stream
18279 pointed to by stream, at the position indicated by the associated file position indicator
18280 for the stream (if defined), and advances the indicator appropriately. If the file cannot
18281 support positioning requests, or if the stream was opened with append mode, the
18282 character is appended to the output stream.
18285 The fputwc function returns the wide character written. If a write error occurs, the
18286 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
18287 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
18292 <pre>
18295 int fputws(const wchar_t * restrict s,
18296 FILE * restrict stream);
18297 </pre>
18300 The fputws function writes the wide string pointed to by s to the stream pointed to by
18301 stream. The terminating null wide character is not written.
18304 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
18305 returns a nonnegative value.
18306 <!--page 381 -->
18311 <pre>
18314 int fwide(FILE *stream, int mode);
18315 </pre>
18318 The fwide function determines the orientation of the stream pointed to by stream. If
18319 mode is greater than zero, the function first attempts to make the stream wide oriented. If
18320 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note293"><b>293)</b></a></sup>
18321 Otherwise, mode is zero and the function does not alter the orientation of the stream.
18324 The fwide function returns a value greater than zero if, after the call, the stream has
18325 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
18326 stream has no orientation.
18329 <p><small><a name="note293" href="#note293">293)</a> If the orientation of the stream has already been determined, fwide does not change it.
18330 </small>
18335 <pre>
18338 wint_t getwc(FILE *stream);
18339 </pre>
18342 The getwc function is equivalent to fgetwc, except that if it is implemented as a
18343 macro, it may evaluate stream more than once, so the argument should never be an
18344 expression with side effects.
18347 The getwc function returns the next wide character from the input stream pointed to by
18348 stream, or WEOF.
18353 <pre>
18355 wint_t getwchar(void);
18356 </pre>
18361 <!--page 382 -->
18364 The getwchar function is equivalent to getwc with the argument stdin.
18367 The getwchar function returns the next wide character from the input stream pointed to
18368 by stdin, or WEOF.
18373 <pre>
18376 wint_t putwc(wchar_t c, FILE *stream);
18377 </pre>
18380 The putwc function is equivalent to fputwc, except that if it is implemented as a
18381 macro, it may evaluate stream more than once, so that argument should never be an
18382 expression with side effects.
18385 The putwc function returns the wide character written, or WEOF.
18390 <pre>
18392 wint_t putwchar(wchar_t c);
18393 </pre>
18396 The putwchar function is equivalent to putwc with the second argument stdout.
18399 The putwchar function returns the character written, or WEOF.
18404 <pre>
18407 wint_t ungetwc(wint_t c, FILE *stream);
18408 </pre>
18411 The ungetwc function pushes the wide character specified by c back onto the input
18412 stream pointed to by stream. Pushed-back wide characters will be returned by
18413 subsequent reads on that stream in the reverse order of their pushing. A successful
18414 <!--page 383 -->
18415 intervening call (with the stream pointed to by stream) to a file positioning function
18416 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
18417 stream. The external storage corresponding to the stream is unchanged.
18419 One wide character of pushback is guaranteed, even if the call to the ungetwc function
18420 follows just after a call to a formatted wide character input function fwscanf,
18421 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
18422 on the same stream without an intervening read or file positioning operation on that
18423 stream, the operation may fail.
18425 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
18426 unchanged.
18428 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
18429 The value of the file position indicator for the stream after reading or discarding all
18430 pushed-back wide characters is the same as it was before the wide characters were pushed
18431 back. For a text or binary stream, the value of its file position indicator after a successful
18432 call to the ungetwc function is unspecified until all pushed-back wide characters are
18433 read or discarded.
18436 The ungetwc function returns the wide character pushed back, or WEOF if the operation
18437 fails.
18441 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide string
18442 manipulation. Various methods are used for determining the lengths of the arrays, but in
18443 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
18444 array. If an array is accessed beyond the end of an object, the behavior is undefined.
18446 Where an argument declared as size_t n determines the length of the array for a
18447 function, n can have the value zero on a call to that function. Unless explicitly stated
18448 otherwise in the description of a particular function in this subclause, pointer arguments
18449 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
18450 function that locates a wide character finds no occurrence, a function that compares two
18451 wide character sequences returns zero, and a function that copies wide characters copies
18452 zero wide characters.
18453 <!--page 384 -->
18455 <h5><a name="7.24.4.1" href="#7.24.4.1">7.24.4.1 Wide string numeric conversion functions</a></h5>
18457 <h5><a name="7.24.4.1.1" href="#7.24.4.1.1">7.24.4.1.1 The wcstod, wcstof, and wcstold functions</a></h5>
18460 <pre>
18462 double wcstod(const wchar_t * restrict nptr,
18463 wchar_t ** restrict endptr);
18464 float wcstof(const wchar_t * restrict nptr,
18465 wchar_t ** restrict endptr);
18466 long double wcstold(const wchar_t * restrict nptr,
18467 wchar_t ** restrict endptr);
18468 </pre>
18471 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
18472 string pointed to by nptr to double, float, and long double representation,
18473 respectively. First, they decompose the input string into three parts: an initial, possibly
18474 empty, sequence of white-space wide characters (as specified by the iswspace
18475 function), a subject sequence resembling a floating-point constant or representing an
18476 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
18477 including the terminating null wide character of the input wide string. Then, they attempt
18478 to convert the subject sequence to a floating-point number, and return the result.
18480 The expected form of the subject sequence is an optional plus or minus sign, then one of
18481 the following:
18482 <ul>
18483 <li> a nonempty sequence of decimal digits optionally containing a decimal-point wide
18484 character, then an optional exponent part as defined for the corresponding single-byte
18487 decimal-point wide character, then an optional binary exponent part as defined in
18489 <li> INF or INFINITY, or any other wide string equivalent except for case
18490 <li> NAN or NAN(n-wchar-sequence<sub>opt</sub>), or any other wide string equivalent except for
18491 case in the NAN part, where:
18492 <pre>
18493 n-wchar-sequence:
18494 digit
18495 nondigit
18496 n-wchar-sequence digit
18497 n-wchar-sequence nondigit
18498 </pre>
18499 </ul>
18500 The subject sequence is defined as the longest initial subsequence of the input wide
18501 string, starting with the first non-white-space wide character, that is of the expected form.
18502 <!--page 385 -->
18503 The subject sequence contains no wide characters if the input wide string is not of the
18504 expected form.
18506 If the subject sequence has the expected form for a floating-point number, the sequence of
18507 wide characters starting with the first digit or the decimal-point wide character
18508 (whichever occurs first) is interpreted as a floating constant according to the rules of
18509 <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
18510 if neither an exponent part nor a decimal-point wide character appears in a decimal
18511 floating point number, or if a binary exponent part does not appear in a hexadecimal
18512 floating point number, an exponent part of the appropriate type with value zero is
18513 assumed to follow the last digit in the string. If the subject sequence begins with a minus
18514 sign, the sequence is interpreted as negated.<sup><a href="#note294"><b>294)</b></a></sup> A wide character sequence INF or
18515 INFINITY is interpreted as an infinity, if representable in the return type, else like a
18516 floating constant that is too large for the range of the return type. A wide character
18517 sequence NAN or NAN(n-wchar-sequence<sub>opt</sub>) is interpreted as a quiet NaN, if supported
18518 in the return type, else like a subject sequence part that does not have the expected form;
18519 the meaning of the n-wchar sequences is implementation-defined.<sup><a href="#note295"><b>295)</b></a></sup> A pointer to the
18520 final wide string is stored in the object pointed to by endptr, provided that endptr is
18521 not a null pointer.
18523 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
18524 value resulting from the conversion is correctly rounded.
18526 In other than the "C" locale, additional locale-specific subject sequence forms may be
18527 accepted.
18529 If the subject sequence is empty or does not have the expected form, no conversion is
18530 performed; the value of nptr is stored in the object pointed to by endptr, provided
18531 that endptr is not a null pointer.
18534 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
18535 the result is not exactly representable, the result should be one of the two numbers in the
18536 appropriate internal format that are adjacent to the hexadecimal floating source value,
18537 with the extra stipulation that the error should have a correct sign for the current rounding
18538 direction.
18542 <!--page 386 -->
18544 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
18545 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
18546 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
18547 consider the two bounding, adjacent decimal strings L and U, both having
18548 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
18549 The result should be one of the (equal or adjacent) values that would be obtained by
18550 correctly rounding L and U according to the current rounding direction, with the extra
18551 stipulation that the error with respect to D should have a correct sign for the current
18555 The functions return the converted value, if any. If no conversion could be performed,
18556 zero is returned. If the correct value is outside the range of representable values, plus or
18557 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
18558 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
18559 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
18560 than the smallest normalized positive number in the return type; whether errno acquires
18561 the value ERANGE is implementation-defined.
18566 <!--page 387 -->
18569 <p><small><a name="note294" href="#note294">294)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
18570 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
18571 methods may yield different results if rounding is toward positive or negative infinity. In either case,
18572 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
18573 </small>
18574 <p><small><a name="note295" href="#note295">295)</a> An implementation may use the n-wchar sequence to determine extra information to be represented in
18575 the NaN's significand.
18576 </small>
18577 <p><small><a name="note296" href="#note296">296)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
18578 to the same internal floating value, but if not will round to adjacent values.
18579 </small>
18581 <h5><a name="7.24.4.1.2" href="#7.24.4.1.2">7.24.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions</a></h5>
18584 <pre>
18586 long int wcstol(
18587 const wchar_t * restrict nptr,
18588 wchar_t ** restrict endptr,
18589 int base);
18590 long long int wcstoll(
18591 const wchar_t * restrict nptr,
18592 wchar_t ** restrict endptr,
18593 int base);
18594 unsigned long int wcstoul(
18595 const wchar_t * restrict nptr,
18596 wchar_t ** restrict endptr,
18597 int base);
18598 unsigned long long int wcstoull(
18599 const wchar_t * restrict nptr,
18600 wchar_t ** restrict endptr,
18601 int base);
18602 </pre>
18605 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
18606 portion of the wide string pointed to by nptr to long int, long long int,
18607 unsigned long int, and unsigned long long int representation,
18608 respectively. First, they decompose the input string into three parts: an initial, possibly
18609 empty, sequence of white-space wide characters (as specified by the iswspace
18610 function), a subject sequence resembling an integer represented in some radix determined
18611 by the value of base, and a final wide string of one or more unrecognized wide
18612 characters, including the terminating null wide character of the input wide string. Then,
18613 they attempt to convert the subject sequence to an integer, and return the result.
18615 If the value of base is zero, the expected form of the subject sequence is that of an
18616 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
18617 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
18619 is a sequence of letters and digits representing an integer with the radix specified by
18620 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
18622 letters and digits whose ascribed values are less than that of base are permitted. If the
18624 of letters and digits, following the sign if present.
18625 <!--page 388 -->
18627 The subject sequence is defined as the longest initial subsequence of the input wide
18628 string, starting with the first non-white-space wide character, that is of the expected form.
18629 The subject sequence contains no wide characters if the input wide string is empty or
18630 consists entirely of white space, or if the first non-white-space wide character is other
18631 than a sign or a permissible letter or digit.
18633 If the subject sequence has the expected form and the value of base is zero, the sequence
18634 of wide characters starting with the first digit is interpreted as an integer constant
18635 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
18637 letter its value as given above. If the subject sequence begins with a minus sign, the value
18638 resulting from the conversion is negated (in the return type). A pointer to the final wide
18639 string is stored in the object pointed to by endptr, provided that endptr is not a null
18640 pointer.
18642 In other than the "C" locale, additional locale-specific subject sequence forms may be
18643 accepted.
18645 If the subject sequence is empty or does not have the expected form, no conversion is
18646 performed; the value of nptr is stored in the object pointed to by endptr, provided
18647 that endptr is not a null pointer.
18650 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
18651 value, if any. If no conversion could be performed, zero is returned. If the correct value
18652 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
18653 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
18654 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
18661 <pre>
18663 wchar_t *wcscpy(wchar_t * restrict s1,
18664 const wchar_t * restrict s2);
18665 </pre>
18668 The wcscpy function copies the wide string pointed to by s2 (including the terminating
18669 null wide character) into the array pointed to by s1.
18672 The wcscpy function returns the value of s1.
18673 <!--page 389 -->
18678 <pre>
18680 wchar_t *wcsncpy(wchar_t * restrict s1,
18681 const wchar_t * restrict s2,
18682 size_t n);
18683 </pre>
18686 The wcsncpy function copies not more than n wide characters (those that follow a null
18687 wide character are not copied) from the array pointed to by s2 to the array pointed to by
18690 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
18691 wide characters are appended to the copy in the array pointed to by s1, until n wide
18692 characters in all have been written.
18695 The wcsncpy function returns the value of s1.
18698 <p><small><a name="note297" href="#note297">297)</a> Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
18699 result will not be null-terminated.
18700 </small>
18705 <pre>
18707 wchar_t *wmemcpy(wchar_t * restrict s1,
18708 const wchar_t * restrict s2,
18709 size_t n);
18710 </pre>
18713 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
18714 object pointed to by s1.
18717 The wmemcpy function returns the value of s1.
18722 <!--page 390 -->
18727 <pre>
18729 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
18730 size_t n);
18731 </pre>
18734 The wmemmove function copies n wide characters from the object pointed to by s2 to
18735 the object pointed to by s1. Copying takes place as if the n wide characters from the
18736 object pointed to by s2 are first copied into a temporary array of n wide characters that
18737 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
18738 the temporary array are copied into the object pointed to by s1.
18741 The wmemmove function returns the value of s1.
18748 <pre>
18750 wchar_t *wcscat(wchar_t * restrict s1,
18751 const wchar_t * restrict s2);
18752 </pre>
18755 The wcscat function appends a copy of the wide string pointed to by s2 (including the
18756 terminating null wide character) to the end of the wide string pointed to by s1. The initial
18757 wide character of s2 overwrites the null wide character at the end of s1.
18760 The wcscat function returns the value of s1.
18765 <pre>
18767 wchar_t *wcsncat(wchar_t * restrict s1,
18768 const wchar_t * restrict s2,
18769 size_t n);
18770 </pre>
18773 The wcsncat function appends not more than n wide characters (a null wide character
18774 and those that follow it are not appended) from the array pointed to by s2 to the end of
18775 <!--page 391 -->
18776 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
18777 wide character at the end of s1. A terminating null wide character is always appended to
18781 The wcsncat function returns the value of s1.
18784 <p><small><a name="note298" href="#note298">298)</a> Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
18785 wcslen(s1)+n+1.
18786 </small>
18790 Unless explicitly stated otherwise, the functions described in this subclause order two
18791 wide characters the same way as two integers of the underlying integer type designated
18792 by wchar_t.
18797 <pre>
18799 int wcscmp(const wchar_t *s1, const wchar_t *s2);
18800 </pre>
18803 The wcscmp function compares the wide string pointed to by s1 to the wide string
18804 pointed to by s2.
18807 The wcscmp function returns an integer greater than, equal to, or less than zero,
18808 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18809 wide string pointed to by s2.
18814 <pre>
18816 int wcscoll(const wchar_t *s1, const wchar_t *s2);
18817 </pre>
18820 The wcscoll function compares the wide string pointed to by s1 to the wide string
18821 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
18822 current locale.
18825 The wcscoll function returns an integer greater than, equal to, or less than zero,
18826 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18829 <!--page 392 -->
18830 wide string pointed to by s2 when both are interpreted as appropriate to the current
18831 locale.
18836 <pre>
18838 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
18839 size_t n);
18840 </pre>
18843 The wcsncmp function compares not more than n wide characters (those that follow a
18844 null wide character are not compared) from the array pointed to by s1 to the array
18845 pointed to by s2.
18848 The wcsncmp function returns an integer greater than, equal to, or less than zero,
18849 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
18850 to, or less than the possibly null-terminated array pointed to by s2.
18855 <pre>
18857 size_t wcsxfrm(wchar_t * restrict s1,
18858 const wchar_t * restrict s2,
18859 size_t n);
18860 </pre>
18863 The wcsxfrm function transforms the wide string pointed to by s2 and places the
18864 resulting wide string into the array pointed to by s1. The transformation is such that if
18865 the wcscmp function is applied to two transformed wide strings, it returns a value greater
18866 than, equal to, or less than zero, corresponding to the result of the wcscoll function
18867 applied to the same two original wide strings. No more than n wide characters are placed
18868 into the resulting array pointed to by s1, including the terminating null wide character. If
18869 n is zero, s1 is permitted to be a null pointer.
18872 The wcsxfrm function returns the length of the transformed wide string (not including
18873 the terminating null wide character). If the value returned is n or greater, the contents of
18874 the array pointed to by s1 are indeterminate.
18876 EXAMPLE The value of the following expression is the length of the array needed to hold the
18877 transformation of the wide string pointed to by s:
18878 <!--page 393 -->
18879 <pre>
18881 </pre>
18887 <pre>
18889 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
18890 size_t n);
18891 </pre>
18894 The wmemcmp function compares the first n wide characters of the object pointed to by
18895 s1 to the first n wide characters of the object pointed to by s2.
18898 The wmemcmp function returns an integer greater than, equal to, or less than zero,
18899 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
18900 pointed to by s2.
18907 <pre>
18909 wchar_t *wcschr(const wchar_t *s, wchar_t c);
18910 </pre>
18913 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
18914 The terminating null wide character is considered to be part of the wide string.
18917 The wcschr function returns a pointer to the located wide character, or a null pointer if
18918 the wide character does not occur in the wide string.
18923 <pre>
18925 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
18926 </pre>
18929 The wcscspn function computes the length of the maximum initial segment of the wide
18930 string pointed to by s1 which consists entirely of wide characters not from the wide
18931 string pointed to by s2.
18932 <!--page 394 -->
18935 The wcscspn function returns the length of the segment.
18940 <pre>
18942 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
18943 </pre>
18946 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
18947 any wide character from the wide string pointed to by s2.
18950 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
18951 no wide character from s2 occurs in s1.
18956 <pre>
18958 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
18959 </pre>
18962 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
18963 s. The terminating null wide character is considered to be part of the wide string.
18966 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
18967 not occur in the wide string.
18972 <pre>
18974 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
18975 </pre>
18978 The wcsspn function computes the length of the maximum initial segment of the wide
18979 string pointed to by s1 which consists entirely of wide characters from the wide string
18980 pointed to by s2.
18983 The wcsspn function returns the length of the segment.
18984 <!--page 395 -->
18989 <pre>
18991 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
18992 </pre>
18995 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
18996 the sequence of wide characters (excluding the terminating null wide character) in the
18997 wide string pointed to by s2.
19000 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
19001 wide string is not found. If s2 points to a wide string with zero length, the function
19002 returns s1.
19007 <pre>
19009 wchar_t *wcstok(wchar_t * restrict s1,
19010 const wchar_t * restrict s2,
19011 wchar_t ** restrict ptr);
19012 </pre>
19015 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
19016 a sequence of tokens, each of which is delimited by a wide character from the wide string
19017 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
19018 which the wcstok function stores information necessary for it to continue scanning the
19019 same wide string.
19021 The first call in a sequence has a non-null first argument and stores an initial value in the
19022 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
19023 the object pointed to by ptr is required to have the value stored by the previous call in
19024 the sequence, which is then updated. The separator wide string pointed to by s2 may be
19025 different from call to call.
19027 The first call in the sequence searches the wide string pointed to by s1 for the first wide
19028 character that is not contained in the current separator wide string pointed to by s2. If no
19029 such wide character is found, then there are no tokens in the wide string pointed to by s1
19030 and the wcstok function returns a null pointer. If such a wide character is found, it is
19031 the start of the first token.
19033 The wcstok function then searches from there for a wide character that is contained in
19034 the current separator wide string. If no such wide character is found, the current token
19035 <!--page 396 -->
19036 extends to the end of the wide string pointed to by s1, and subsequent searches in the
19037 same wide string for a token return a null pointer. If such a wide character is found, it is
19038 overwritten by a null wide character, which terminates the current token.
19040 In all cases, the wcstok function stores sufficient information in the pointer pointed to
19041 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
19042 value for ptr, shall start searching just past the element overwritten by a null wide
19043 character (if any).
19046 The wcstok function returns a pointer to the first wide character of a token, or a null
19047 pointer if there is no token.
19049 EXAMPLE
19050 <pre>
19052 static wchar_t str1[] = L"?a???b,,,#c";
19053 static wchar_t str2[] = L"\t \t";
19054 wchar_t *t, *ptr1, *ptr2;
19060 </pre>
19066 <pre>
19068 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
19069 size_t n);
19070 </pre>
19073 The wmemchr function locates the first occurrence of c in the initial n wide characters of
19074 the object pointed to by s.
19077 The wmemchr function returns a pointer to the located wide character, or a null pointer if
19078 the wide character does not occur in the object.
19079 <!--page 397 -->
19086 <pre>
19088 size_t wcslen(const wchar_t *s);
19089 </pre>
19092 The wcslen function computes the length of the wide string pointed to by s.
19095 The wcslen function returns the number of wide characters that precede the terminating
19096 null wide character.
19101 <pre>
19103 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
19104 </pre>
19107 The wmemset function copies the value of c into each of the first n wide characters of
19108 the object pointed to by s.
19111 The wmemset function returns the value of s.
19118 <pre>
19121 size_t wcsftime(wchar_t * restrict s,
19122 size_t maxsize,
19123 const wchar_t * restrict format,
19124 const struct tm * restrict timeptr);
19125 </pre>
19128 The wcsftime function is equivalent to the strftime function, except that:
19129 <ul>
19130 <li> The argument s points to the initial element of an array of wide characters into which
19131 the generated output is to be placed.
19132 <!--page 398 -->
19133 <li> The argument maxsize indicates the limiting number of wide characters.
19134 <li> The argument format is a wide string and the conversion specifiers are replaced by
19135 corresponding sequences of wide characters.
19136 <li> The return value indicates the number of wide characters.
19137 </ul>
19140 If the total number of resulting wide characters including the terminating null wide
19141 character is not more than maxsize, the wcsftime function returns the number of
19142 wide characters placed into the array pointed to by s not including the terminating null
19143 wide character. Otherwise, zero is returned and the contents of the array are
19144 indeterminate.
19146 <h4><a name="7.24.6" href="#7.24.6">7.24.6 Extended multibyte/wide character conversion utilities</a></h4>
19148 The header <a href="#7.24"><wchar.h></a> declares an extended set of functions useful for conversion
19149 between multibyte characters and wide characters.
19151 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.24.6.3">7.24.6.3</a> and
19152 <a href="#7.24.6.4">7.24.6.4</a> -- take as a last argument a pointer to an object of type mbstate_t that is used
19153 to describe the current conversion state from a particular multibyte character sequence to
19154 a wide character sequence (or the reverse) under the rules of a particular setting for the
19155 LC_CTYPE category of the current locale.
19157 The initial conversion state corresponds, for a conversion in either direction, to the
19158 beginning of a new multibyte character in the initial shift state. A zero-valued
19159 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
19160 valued mbstate_t object can be used to initiate conversion involving any multibyte
19161 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
19162 been altered by any of the functions described in this subclause, and is then used with a
19163 different multibyte character sequence, or in the other conversion direction, or with a
19164 different LC_CTYPE category setting than on earlier function calls, the behavior is
19167 On entry, each function takes the described conversion state (either internal or pointed to
19168 by an argument) as current. The conversion state described by the pointed-to object is
19169 altered as needed to track the shift state, and the position within a multibyte character, for
19170 the associated multibyte character sequence.
19175 <!--page 399 -->
19178 <p><small><a name="note299" href="#note299">299)</a> Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
19179 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
19180 character string.
19181 </small>
19183 <h5><a name="7.24.6.1" href="#7.24.6.1">7.24.6.1 Single-byte/wide character conversion functions</a></h5>
19188 <pre>
19191 wint_t btowc(int c);
19192 </pre>
19195 The btowc function determines whether c constitutes a valid single-byte character in the
19196 initial shift state.
19199 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
19200 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
19201 returns the wide character representation of that character.
19206 <pre>
19209 int wctob(wint_t c);
19210 </pre>
19213 The wctob function determines whether c corresponds to a member of the extended
19214 character set whose multibyte character representation is a single byte when in the initial
19215 shift state.
19218 The wctob function returns EOF if c does not correspond to a multibyte character with
19219 length one in the initial shift state. Otherwise, it returns the single-byte representation of
19220 that character as an unsigned char converted to an int.
19227 <pre>
19229 int mbsinit(const mbstate_t *ps);
19230 </pre>
19233 If ps is not a null pointer, the mbsinit function determines whether the pointed-to
19234 mbstate_t object describes an initial conversion state.
19235 <!--page 400 -->
19238 The mbsinit function returns nonzero if ps is a null pointer or if the pointed-to object
19239 describes an initial conversion state; otherwise, it returns zero.
19241 <h5><a name="7.24.6.3" href="#7.24.6.3">7.24.6.3 Restartable multibyte/wide character conversion functions</a></h5>
19243 These functions differ from the corresponding multibyte character functions of <a href="#7.20.7">7.20.7</a>
19244 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
19245 pointer to mbstate_t that points to an object that can completely describe the current
19246 conversion state of the associated multibyte character sequence. If ps is a null pointer,
19247 each function uses its own internal mbstate_t object instead, which is initialized at
19248 program startup to the initial conversion state. The implementation behaves as if no
19249 library function calls these functions with a null pointer for ps.
19251 Also unlike their corresponding functions, the return value does not represent whether the
19252 encoding is state-dependent.
19257 <pre>
19259 size_t mbrlen(const char * restrict s,
19260 size_t n,
19261 mbstate_t * restrict ps);
19262 </pre>
19265 The mbrlen function is equivalent to the call:
19266 <pre>
19267 mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)
19268 </pre>
19269 where internal is the mbstate_t object for the mbrlen function, except that the
19270 expression designated by ps is evaluated only once.
19273 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
19274 or (size_t)(-1).
19276 <!--page 401 -->
19281 <pre>
19283 size_t mbrtowc(wchar_t * restrict pwc,
19284 const char * restrict s,
19285 size_t n,
19286 mbstate_t * restrict ps);
19287 </pre>
19290 If s is a null pointer, the mbrtowc function is equivalent to the call:
19291 <pre>
19293 </pre>
19294 In this case, the values of the parameters pwc and n are ignored.
19296 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
19297 the byte pointed to by s to determine the number of bytes needed to complete the next
19298 multibyte character (including any shift sequences). If the function determines that the
19299 next multibyte character is complete and valid, it determines the value of the
19300 corresponding wide character and then, if pwc is not a null pointer, stores that value in
19301 the object pointed to by pwc. If the corresponding wide character is the null wide
19302 character, the resulting state described is the initial conversion state.
19305 The mbrtowc function returns the first of the following that applies (given the current
19306 conversion state):
19307 <dl>
19309 corresponds to the null wide character (which is the value stored).
19311 character (which is the value stored); the value returned is the number
19312 of bytes that complete the multibyte character.
19314 multibyte character, and all n bytes have been processed (no value is
19317 do not contribute to a complete and valid multibyte character (no
19318 value is stored); the value of the macro EILSEQ is stored in errno,
19319 and the conversion state is unspecified.
19320 </dl>
19321 <!--page 402 -->
19324 <p><small><a name="note300" href="#note300">300)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
19325 sequence of redundant shift sequences (for implementations with state-dependent encodings).
19326 </small>
19331 <pre>
19333 size_t wcrtomb(char * restrict s,
19334 wchar_t wc,
19335 mbstate_t * restrict ps);
19336 </pre>
19339 If s is a null pointer, the wcrtomb function is equivalent to the call
19340 <pre>
19341 wcrtomb(buf, L'\0', ps)
19342 </pre>
19343 where buf is an internal buffer.
19345 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
19346 to represent the multibyte character that corresponds to the wide character given by wc
19347 (including any shift sequences), and stores the multibyte character representation in the
19348 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
19349 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
19350 to restore the initial shift state; the resulting state described is the initial conversion state.
19353 The wcrtomb function returns the number of bytes stored in the array object (including
19354 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
19355 the function stores the value of the macro EILSEQ in errno and returns
19356 (size_t)(-1); the conversion state is unspecified.
19358 <h5><a name="7.24.6.4" href="#7.24.6.4">7.24.6.4 Restartable multibyte/wide string conversion functions</a></h5>
19360 These functions differ from the corresponding multibyte string functions of <a href="#7.20.8">7.20.8</a>
19361 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
19362 mbstate_t that points to an object that can completely describe the current conversion
19363 state of the associated multibyte character sequence. If ps is a null pointer, each function
19364 uses its own internal mbstate_t object instead, which is initialized at program startup
19365 to the initial conversion state. The implementation behaves as if no library function calls
19366 these functions with a null pointer for ps.
19368 Also unlike their corresponding functions, the conversion source parameter, src, has a
19369 pointer-to-pointer type. When the function is storing the results of conversions (that is,
19370 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
19371 to reflect the amount of the source processed by that invocation.
19372 <!--page 403 -->
19377 <pre>
19379 size_t mbsrtowcs(wchar_t * restrict dst,
19380 const char ** restrict src,
19381 size_t len,
19382 mbstate_t * restrict ps);
19383 </pre>
19386 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
19387 conversion state described by the object pointed to by ps, from the array indirectly
19388 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
19389 pointer, the converted characters are stored into the array pointed to by dst. Conversion
19390 continues up to and including a terminating null character, which is also stored.
19391 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
19392 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
19393 characters have been stored into the array pointed to by dst.<sup><a href="#note301"><b>301)</b></a></sup> Each conversion takes
19394 place as if by a call to the mbrtowc function.
19396 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
19397 pointer (if conversion stopped due to reaching a terminating null character) or the address
19398 just past the last multibyte character converted (if any). If conversion stopped due to
19399 reaching a terminating null character and if dst is not a null pointer, the resulting state
19400 described is the initial conversion state.
19403 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
19404 character, an encoding error occurs: the mbsrtowcs function stores the value of the
19405 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
19406 unspecified. Otherwise, it returns the number of multibyte characters successfully
19407 converted, not including the terminating null character (if any).
19412 <!--page 404 -->
19415 <p><small><a name="note301" href="#note301">301)</a> Thus, the value of len is ignored if dst is a null pointer.
19416 </small>
19421 <pre>
19423 size_t wcsrtombs(char * restrict dst,
19424 const wchar_t ** restrict src,
19425 size_t len,
19426 mbstate_t * restrict ps);
19427 </pre>
19430 The wcsrtombs function converts a sequence of wide characters from the array
19431 indirectly pointed to by src into a sequence of corresponding multibyte characters that
19432 begins in the conversion state described by the object pointed to by ps. If dst is not a
19433 null pointer, the converted characters are then stored into the array pointed to by dst.
19434 Conversion continues up to and including a terminating null wide character, which is also
19435 stored. Conversion stops earlier in two cases: when a wide character is reached that does
19436 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
19437 next multibyte character would exceed the limit of len total bytes to be stored into the
19438 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
19441 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
19442 pointer (if conversion stopped due to reaching a terminating null wide character) or the
19443 address just past the last wide character converted (if any). If conversion stopped due to
19444 reaching a terminating null wide character, the resulting state described is the initial
19445 conversion state.
19448 If conversion stops because a wide character is reached that does not correspond to a
19449 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
19450 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
19451 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
19452 character sequence, not including the terminating null character (if any).
19457 <!--page 405 -->
19460 <p><small><a name="note302" href="#note302">302)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
19461 include those necessary to reach the initial shift state immediately before the null byte.
19462 </small>
19464 <h3><a name="7.25" href="#7.25">7.25 Wide character classification and mapping utilities <wctype.h></a></h3>
19468 The header <a href="#7.25"><wctype.h></a> declares three data types, one macro, and many functions.<sup><a href="#note303"><b>303)</b></a></sup>
19470 The types declared are
19471 <pre>
19472 wint_t
19473 </pre>
19475 <pre>
19476 wctrans_t
19477 </pre>
19478 which is a scalar type that can hold values which represent locale-specific character
19479 mappings; and
19480 <pre>
19481 wctype_t
19482 </pre>
19483 which is a scalar type that can hold values which represent locale-specific character
19484 classifications.
19488 The functions declared are grouped as follows:
19489 <ul>
19490 <li> Functions that provide wide character classification;
19491 <li> Extensible functions that provide wide character classification;
19492 <li> Functions that provide wide character case mapping;
19493 <li> Extensible functions that provide wide character mapping.
19494 </ul>
19496 For all functions described in this subclause that accept an argument of type wint_t, the
19497 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
19498 this argument has any other value, the behavior is undefined.
19500 The behavior of these functions is affected by the LC_CTYPE category of the current
19501 locale.
19506 <!--page 406 -->
19509 <p><small><a name="note303" href="#note303">303)</a> See ''future library directions'' (<a href="#7.26.13">7.26.13</a>).
19510 </small>
19514 The header <a href="#7.25"><wctype.h></a> declares several functions useful for classifying wide
19515 characters.
19517 The term printing wide character refers to a member of a locale-specific set of wide
19518 characters, each of which occupies at least one printing position on a display device. The
19519 term control wide character refers to a member of a locale-specific set of wide characters
19520 that are not printing wide characters.
19522 <h5><a name="7.25.2.1" href="#7.25.2.1">7.25.2.1 Wide character classification functions</a></h5>
19524 The functions in this subclause return nonzero (true) if and only if the value of the
19525 argument wc conforms to that in the description of the function.
19527 Each of the following functions returns true for each wide character that corresponds (as
19528 if by a call to the wctob function) to a single-byte character for which the corresponding
19529 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
19530 iswpunct functions may differ with respect to wide characters other than L' ' that are
19535 <p><small><a name="note304" href="#note304">304)</a> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
19536 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
19537 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
19538 && iswspace(wc) is true, but not both.
19539 </small>
19544 <pre>
19546 int iswalnum(wint_t wc);
19547 </pre>
19550 The iswalnum function tests for any wide character for which iswalpha or
19551 iswdigit is true.
19556 <pre>
19558 int iswalpha(wint_t wc);
19559 </pre>
19562 The iswalpha function tests for any wide character for which iswupper or
19563 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
19565 <!--page 407 -->
19566 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
19570 <p><small><a name="note305" href="#note305">305)</a> The functions iswlower and iswupper test true or false separately for each of these additional
19571 wide characters; all four combinations are possible.
19572 </small>
19577 <pre>
19579 int iswblank(wint_t wc);
19580 </pre>
19583 The iswblank function tests for any wide character that is a standard blank wide
19584 character or is one of a locale-specific set of wide characters for which iswspace is true
19585 and that is used to separate words within a line of text. The standard blank wide
19586 characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
19587 locale, iswblank returns true only for the standard blank characters.
19592 <pre>
19594 int iswcntrl(wint_t wc);
19595 </pre>
19598 The iswcntrl function tests for any control wide character.
19603 <pre>
19605 int iswdigit(wint_t wc);
19606 </pre>
19609 The iswdigit function tests for any wide character that corresponds to a decimal-digit
19615 <pre>
19617 int iswgraph(wint_t wc);
19618 </pre>
19623 <!--page 408 -->
19626 The iswgraph function tests for any wide character for which iswprint is true and
19630 <p><small><a name="note306" href="#note306">306)</a> Note that the behavior of the iswgraph and iswpunct functions may differ from their
19631 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
19632 characters other than ' '.
19633 </small>
19638 <pre>
19640 int iswlower(wint_t wc);
19641 </pre>
19644 The iswlower function tests for any wide character that corresponds to a lowercase
19645 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
19646 iswdigit, iswpunct, or iswspace is true.
19651 <pre>
19653 int iswprint(wint_t wc);
19654 </pre>
19657 The iswprint function tests for any printing wide character.
19662 <pre>
19664 int iswpunct(wint_t wc);
19665 </pre>
19668 The iswpunct function tests for any printing wide character that is one of a locale-
19669 specific set of punctuation wide characters for which neither iswspace nor iswalnum
19675 <pre>
19677 int iswspace(wint_t wc);
19678 </pre>
19682 <!--page 409 -->
19685 The iswspace function tests for any wide character that corresponds to a locale-specific
19686 set of white-space wide characters for which none of iswalnum, iswgraph, or
19687 iswpunct is true.
19692 <pre>
19694 int iswupper(wint_t wc);
19695 </pre>
19698 The iswupper function tests for any wide character that corresponds to an uppercase
19699 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
19700 iswdigit, iswpunct, or iswspace is true.
19705 <pre>
19707 int iswxdigit(wint_t wc);
19708 </pre>
19711 The iswxdigit function tests for any wide character that corresponds to a
19714 <h5><a name="7.25.2.2" href="#7.25.2.2">7.25.2.2 Extensible wide character classification functions</a></h5>
19716 The functions wctype and iswctype provide extensible wide character classification
19717 as well as testing equivalent to that performed by the functions described in the previous
19723 <pre>
19725 int iswctype(wint_t wc, wctype_t desc);
19726 </pre>
19729 The iswctype function determines whether the wide character wc has the property
19730 described by desc. The current setting of the LC_CTYPE category shall be the same as
19731 during the call to wctype that returned the value desc.
19733 Each of the following expressions has a truth-value equivalent to the call to the wide
19734 character classification function (<a href="#7.25.2.1">7.25.2.1</a>) in the comment that follows the expression:
19735 <!--page 410 -->
19736 <pre>
19737 iswctype(wc, wctype("alnum")) // iswalnum(wc)
19738 iswctype(wc, wctype("alpha")) // iswalpha(wc)
19739 iswctype(wc, wctype("blank")) // iswblank(wc)
19740 iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
19741 iswctype(wc, wctype("digit")) // iswdigit(wc)
19742 iswctype(wc, wctype("graph")) // iswgraph(wc)
19743 iswctype(wc, wctype("lower")) // iswlower(wc)
19744 iswctype(wc, wctype("print")) // iswprint(wc)
19745 iswctype(wc, wctype("punct")) // iswpunct(wc)
19746 iswctype(wc, wctype("space")) // iswspace(wc)
19747 iswctype(wc, wctype("upper")) // iswupper(wc)
19748 iswctype(wc, wctype("xdigit")) // iswxdigit(wc)
19749 </pre>
19752 The iswctype function returns nonzero (true) if and only if the value of the wide
19753 character wc has the property described by desc.
19759 <pre>
19761 wctype_t wctype(const char *property);
19762 </pre>
19765 The wctype function constructs a value with type wctype_t that describes a class of
19766 wide characters identified by the string argument property.
19768 The strings listed in the description of the iswctype function shall be valid in all
19769 locales as property arguments to the wctype function.
19772 If property identifies a valid class of wide characters according to the LC_CTYPE
19773 category of the current locale, the wctype function returns a nonzero value that is valid
19774 as the second argument to the iswctype function; otherwise, it returns zero. *
19775 <!--page 411 -->
19779 The header <a href="#7.25"><wctype.h></a> declares several functions useful for mapping wide characters.
19781 <h5><a name="7.25.3.1" href="#7.25.3.1">7.25.3.1 Wide character case mapping functions</a></h5>
19786 <pre>
19788 wint_t towlower(wint_t wc);
19789 </pre>
19792 The towlower function converts an uppercase letter to a corresponding lowercase letter.
19795 If the argument is a wide character for which iswupper is true and there are one or
19796 more corresponding wide characters, as specified by the current locale, for which
19797 iswlower is true, the towlower function returns one of the corresponding wide
19798 characters (always the same one for any given locale); otherwise, the argument is
19799 returned unchanged.
19804 <pre>
19806 wint_t towupper(wint_t wc);
19807 </pre>
19810 The towupper function converts a lowercase letter to a corresponding uppercase letter.
19813 If the argument is a wide character for which iswlower is true and there are one or
19814 more corresponding wide characters, as specified by the current locale, for which
19815 iswupper is true, the towupper function returns one of the corresponding wide
19816 characters (always the same one for any given locale); otherwise, the argument is
19817 returned unchanged.
19819 <h5><a name="7.25.3.2" href="#7.25.3.2">7.25.3.2 Extensible wide character case mapping functions</a></h5>
19821 The functions wctrans and towctrans provide extensible wide character mapping as
19822 well as case mapping equivalent to that performed by the functions described in the
19824 <!--page 412 -->
19829 <pre>
19831 wint_t towctrans(wint_t wc, wctrans_t desc);
19832 </pre>
19835 The towctrans function maps the wide character wc using the mapping described by
19836 desc. The current setting of the LC_CTYPE category shall be the same as during the call
19837 to wctrans that returned the value desc.
19839 Each of the following expressions behaves the same as the call to the wide character case
19840 mapping function (<a href="#7.25.3.1">7.25.3.1</a>) in the comment that follows the expression:
19841 <pre>
19842 towctrans(wc, wctrans("tolower")) // towlower(wc)
19843 towctrans(wc, wctrans("toupper")) // towupper(wc)
19844 </pre>
19847 The towctrans function returns the mapped value of wc using the mapping described
19848 by desc.
19853 <pre>
19855 wctrans_t wctrans(const char *property);
19856 </pre>
19859 The wctrans function constructs a value with type wctrans_t that describes a
19860 mapping between wide characters identified by the string argument property.
19862 The strings listed in the description of the towctrans function shall be valid in all
19863 locales as property arguments to the wctrans function.
19866 If property identifies a valid mapping of wide characters according to the LC_CTYPE
19867 category of the current locale, the wctrans function returns a nonzero value that is valid
19868 as the second argument to the towctrans function; otherwise, it returns zero.
19869 <!--page 413 -->
19873 The following names are grouped under individual headers for convenience. All external
19874 names described below are reserved no matter what headers are included by the program.
19878 The function names
19879 <pre>
19880 cerf cexpm1 clog2
19881 cerfc clog10 clgamma
19882 cexp2 clog1p ctgamma
19883 </pre>
19884 and the same names suffixed with f or l may be added to the declarations in the
19889 Function names that begin with either is or to, and a lowercase letter may be added to
19894 Macros that begin with E and a digit or E and an uppercase letter may be added to the
19897 <h4><a name="7.26.4" href="#7.26.4">7.26.4 Format conversion of integer types <inttypes.h></a></h4>
19899 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
19904 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
19909 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
19914 The ability to undefine and perhaps then redefine the macros bool, true, and false is
19915 an obsolescent feature.
19919 Typedef names beginning with int or uint and ending with _t may be added to the
19920 types defined in the <a href="#7.18"><stdint.h></a> header. Macro names beginning with INT or UINT
19921 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
19923 <!--page 414 -->
19927 Lowercase letters may be added to the conversion specifiers and length modifiers in
19928 fprintf and fscanf. Other characters may be used in extensions.
19930 The gets function is obsolescent, and is deprecated.
19932 The use of ungetc on a binary stream where the file position indicator is zero prior to
19933 the call is an obsolescent feature.
19937 Function names that begin with str and a lowercase letter may be added to the
19942 Function names that begin with str, mem, or wcs and a lowercase letter may be added
19945 <h4><a name="7.26.12" href="#7.26.12">7.26.12 Extended multibyte and wide character utilities <wchar.h></a></h4>
19947 Function names that begin with wcs and a lowercase letter may be added to the
19950 Lowercase letters may be added to the conversion specifiers and length modifiers in
19951 fwprintf and fwscanf. Other characters may be used in extensions.
19953 <h4><a name="7.26.13" href="#7.26.13">7.26.13 Wide character classification and mapping utilities</a></h4>
19956 Function names that begin with is or to and a lowercase letter may be added to the
19958 <!--page 415 -->
19961 <pre>
19962 (informative)
19963 Language syntax summary
19964 </pre>
19973 <pre>
19974 keyword
19975 identifier
19976 constant
19977 string-literal
19978 punctuator
19979 </pre>
19981 <pre>
19982 header-name
19983 identifier
19984 pp-number
19985 character-constant
19986 string-literal
19987 punctuator
19988 each non-white-space character that cannot be one of the above
19989 </pre>
19993 <!--page 416 -->
19994 <pre>
19995 auto enum restrict unsigned
19996 break extern return void
19997 case float short volatile
19998 char for signed while
19999 const goto sizeof _Bool
20000 continue if static _Complex
20001 default inline struct _Imaginary
20002 do int switch
20003 double long typedef
20004 else register union
20005 </pre>
20009 <pre>
20010 identifier-nondigit
20011 identifier identifier-nondigit
20012 identifier digit
20013 </pre>
20015 <pre>
20016 nondigit
20017 universal-character-name
20018 other implementation-defined characters
20019 </pre>
20021 <pre>
20022 _ a b c d e f g h i j k l m
20023 n o p q r s t u v w x y z
20024 A B C D E F G H I J K L M
20025 N O P Q R S T U V W X Y Z
20026 </pre>
20028 <pre>
20029 0 1 2 3 4 5 6 7 8 9
20030 </pre>
20034 <pre>
20035 \u hex-quad
20036 \U hex-quad hex-quad
20037 </pre>
20039 <pre>
20040 hexadecimal-digit hexadecimal-digit
20041 hexadecimal-digit hexadecimal-digit
20042 </pre>
20046 <pre>
20047 integer-constant
20048 floating-constant
20049 enumeration-constant
20050 character-constant
20051 </pre>
20053 <pre>
20057 </pre>
20059 <!--page 417 -->
20060 <pre>
20061 nonzero-digit
20062 decimal-constant digit
20063 </pre>
20065 <pre>
20066 0
20067 octal-constant octal-digit
20068 </pre>
20070 <pre>
20071 hexadecimal-prefix hexadecimal-digit
20072 hexadecimal-constant hexadecimal-digit
20073 </pre>
20075 <pre>
20077 </pre>
20079 <pre>
20080 1 2 3 4 5 6 7 8 9
20081 </pre>
20083 <pre>
20084 0 1 2 3 4 5 6 7
20085 </pre>
20087 <pre>
20088 0 1 2 3 4 5 6 7 8 9
20089 a b c d e f
20090 A B C D E F
20091 </pre>
20093 <pre>
20095 unsigned-suffix long-long-suffix
20098 </pre>
20100 <pre>
20101 u U
20102 </pre>
20104 <pre>
20105 l L
20106 </pre>
20108 <pre>
20109 ll LL
20110 </pre>
20112 <pre>
20113 decimal-floating-constant
20114 hexadecimal-floating-constant
20115 </pre>
20117 <!--page 418 -->
20118 <pre>
20121 </pre>
20123 <pre>
20124 hexadecimal-prefix hexadecimal-fractional-constant
20126 hexadecimal-prefix hexadecimal-digit-sequence
20128 </pre>
20130 <pre>
20132 digit-sequence .
20133 </pre>
20135 <pre>
20138 </pre>
20140 <pre>
20141 + -
20142 </pre>
20144 <pre>
20145 digit
20146 digit-sequence digit
20147 </pre>
20149 <pre>
20151 hexadecimal-digit-sequence
20152 hexadecimal-digit-sequence .
20153 </pre>
20155 <pre>
20158 </pre>
20160 <pre>
20161 hexadecimal-digit
20162 hexadecimal-digit-sequence hexadecimal-digit
20163 </pre>
20165 <pre>
20166 f l F L
20167 </pre>
20169 <pre>
20170 identifier
20171 </pre>
20173 <!--page 419 -->
20174 <pre>
20175 ' c-char-sequence '
20176 L' c-char-sequence '
20177 </pre>
20179 <pre>
20180 c-char
20181 c-char-sequence c-char
20182 </pre>
20184 <pre>
20185 any member of the source character set except
20186 the single-quote ', backslash \, or new-line character
20187 escape-sequence
20188 </pre>
20190 <pre>
20191 simple-escape-sequence
20192 octal-escape-sequence
20193 hexadecimal-escape-sequence
20194 universal-character-name
20195 </pre>
20197 <pre>
20198 \' \" \? \\
20199 \a \b \f \n \r \t \v
20200 </pre>
20202 <pre>
20203 \ octal-digit
20204 \ octal-digit octal-digit
20205 \ octal-digit octal-digit octal-digit
20206 </pre>
20208 <pre>
20209 \x hexadecimal-digit
20210 hexadecimal-escape-sequence hexadecimal-digit
20211 </pre>
20215 <pre>
20218 </pre>
20220 <pre>
20221 s-char
20222 s-char-sequence s-char
20223 </pre>
20225 <!--page 420 -->
20226 <pre>
20227 any member of the source character set except
20228 the double-quote ", backslash \, or new-line character
20229 escape-sequence
20230 </pre>
20234 <pre>
20235 [ ] ( ) { } . ->
20236 ++ -- & * + - ~ !
20238 ? : ; ...
20240 , # ##
20242 </pre>
20246 <pre>
20248 " q-char-sequence "
20249 </pre>
20251 <pre>
20252 h-char
20253 h-char-sequence h-char
20254 </pre>
20256 <pre>
20257 any member of the source character set except
20258 the new-line character and >
20259 </pre>
20261 <pre>
20262 q-char
20263 q-char-sequence q-char
20264 </pre>
20266 <pre>
20267 any member of the source character set except
20268 the new-line character and "
20269 </pre>
20273 <!--page 421 -->
20274 <pre>
20275 digit
20276 . digit
20277 pp-number digit
20278 pp-number identifier-nondigit
20279 pp-number e sign
20280 pp-number E sign
20281 pp-number p sign
20282 pp-number P sign
20283 pp-number .
20284 </pre>
20290 <pre>
20291 identifier
20292 constant
20293 string-literal
20294 ( expression )
20295 </pre>
20297 <pre>
20298 primary-expression
20299 postfix-expression [ expression ]
20300 postfix-expression ( argument-expression-list<sub>opt</sub> )
20301 postfix-expression . identifier
20302 postfix-expression -> identifier
20303 postfix-expression ++
20304 postfix-expression --
20305 ( type-name ) { initializer-list }
20306 ( type-name ) { initializer-list , }
20307 </pre>
20309 <pre>
20310 assignment-expression
20311 argument-expression-list , assignment-expression
20312 </pre>
20314 <pre>
20315 postfix-expression
20316 ++ unary-expression
20317 -- unary-expression
20318 unary-operator cast-expression
20319 sizeof unary-expression
20320 sizeof ( type-name )
20321 </pre>
20323 <pre>
20324 & * + - ~ !
20325 </pre>
20327 <pre>
20328 unary-expression
20329 ( type-name ) cast-expression
20330 </pre>
20332 <!--page 422 -->
20333 <pre>
20334 cast-expression
20335 multiplicative-expression * cast-expression
20336 multiplicative-expression / cast-expression
20337 multiplicative-expression % cast-expression
20338 </pre>
20340 <pre>
20341 multiplicative-expression
20342 additive-expression + multiplicative-expression
20343 additive-expression - multiplicative-expression
20344 </pre>
20346 <pre>
20347 additive-expression
20348 shift-expression << additive-expression
20349 shift-expression >> additive-expression
20350 </pre>
20352 <pre>
20353 shift-expression
20354 relational-expression < shift-expression
20355 relational-expression > shift-expression
20356 relational-expression <= shift-expression
20357 relational-expression >= shift-expression
20358 </pre>
20360 <pre>
20361 relational-expression
20362 equality-expression == relational-expression
20363 equality-expression != relational-expression
20364 </pre>
20366 <pre>
20367 equality-expression
20368 AND-expression & equality-expression
20369 </pre>
20371 <pre>
20372 AND-expression
20373 exclusive-OR-expression ^ AND-expression
20374 </pre>
20376 <pre>
20377 exclusive-OR-expression
20378 inclusive-OR-expression | exclusive-OR-expression
20379 </pre>
20381 <pre>
20382 inclusive-OR-expression
20383 logical-AND-expression && inclusive-OR-expression
20384 </pre>
20386 <pre>
20387 logical-AND-expression
20388 logical-OR-expression || logical-AND-expression
20389 </pre>
20391 <!--page 423 -->
20392 <pre>
20393 logical-OR-expression
20394 logical-OR-expression ? expression : conditional-expression
20395 </pre>
20397 <pre>
20398 conditional-expression
20399 unary-expression assignment-operator assignment-expression
20400 </pre>
20402 <pre>
20403 = *= /= %= += -= <<= >>= &= ^= |=
20404 </pre>
20406 <pre>
20407 assignment-expression
20408 expression , assignment-expression
20409 </pre>
20411 <pre>
20412 conditional-expression
20413 </pre>
20417 <pre>
20418 declaration-specifiers init-declarator-list<sub>opt</sub> ;
20419 </pre>
20421 <pre>
20422 storage-class-specifier declaration-specifiers<sub>opt</sub>
20423 type-specifier declaration-specifiers<sub>opt</sub>
20424 type-qualifier declaration-specifiers<sub>opt</sub>
20425 function-specifier declaration-specifiers<sub>opt</sub>
20426 </pre>
20428 <pre>
20429 init-declarator
20430 init-declarator-list , init-declarator
20431 </pre>
20433 <pre>
20434 declarator
20435 declarator = initializer
20436 </pre>
20438 <!--page 424 -->
20439 <pre>
20440 typedef
20441 extern
20442 static
20443 auto
20444 register
20445 </pre>
20447 <pre>
20448 void
20449 char
20450 short
20451 int
20452 long
20453 float
20454 double
20455 signed
20456 unsigned
20457 _Bool
20458 _Complex
20459 struct-or-union-specifier *
20460 enum-specifier
20461 typedef-name
20462 </pre>
20464 <pre>
20465 struct-or-union identifier<sub>opt</sub> { struct-declaration-list }
20466 struct-or-union identifier
20467 </pre>
20469 <pre>
20470 struct
20471 union
20472 </pre>
20474 <pre>
20475 struct-declaration
20476 struct-declaration-list struct-declaration
20477 </pre>
20479 <pre>
20480 specifier-qualifier-list struct-declarator-list ;
20481 </pre>
20483 <pre>
20484 type-specifier specifier-qualifier-list<sub>opt</sub>
20485 type-qualifier specifier-qualifier-list<sub>opt</sub>
20486 </pre>
20488 <pre>
20489 struct-declarator
20490 struct-declarator-list , struct-declarator
20491 </pre>
20493 <!--page 425 -->
20494 <pre>
20495 declarator
20496 declarator<sub>opt</sub> : constant-expression
20497 </pre>
20499 <pre>
20500 enum identifier<sub>opt</sub> { enumerator-list }
20501 enum identifier<sub>opt</sub> { enumerator-list , }
20502 enum identifier
20503 </pre>
20505 <pre>
20506 enumerator
20507 enumerator-list , enumerator
20508 </pre>
20510 <pre>
20511 enumeration-constant
20512 enumeration-constant = constant-expression
20513 </pre>
20515 <pre>
20516 const
20517 restrict
20518 volatile
20519 </pre>
20521 <pre>
20522 inline
20523 </pre>
20525 <pre>
20526 pointer<sub>opt</sub> direct-declarator
20527 </pre>
20529 <pre>
20530 identifier
20531 ( declarator )
20532 direct-declarator [ type-qualifier-list<sub>opt</sub> assignment-expression<sub>opt</sub> ]
20533 direct-declarator [ static type-qualifier-list<sub>opt</sub> assignment-expression ]
20534 direct-declarator [ type-qualifier-list static assignment-expression ]
20535 direct-declarator [ type-qualifier-list<sub>opt</sub> * ]
20536 direct-declarator ( parameter-type-list )
20537 direct-declarator ( identifier-list<sub>opt</sub> )
20538 </pre>
20540 <pre>
20541 * type-qualifier-list<sub>opt</sub>
20542 * type-qualifier-list<sub>opt</sub> pointer
20543 </pre>
20545 <pre>
20546 type-qualifier
20547 type-qualifier-list type-qualifier
20548 </pre>
20550 <!--page 426 -->
20551 <pre>
20552 parameter-list
20553 parameter-list , ...
20554 </pre>
20556 <pre>
20557 parameter-declaration
20558 parameter-list , parameter-declaration
20559 </pre>
20561 <pre>
20562 declaration-specifiers declarator
20563 declaration-specifiers abstract-declarator<sub>opt</sub>
20564 </pre>
20566 <pre>
20567 identifier
20568 identifier-list , identifier
20569 </pre>
20571 <pre>
20572 specifier-qualifier-list abstract-declarator<sub>opt</sub>
20573 </pre>
20575 <pre>
20576 pointer
20577 pointer<sub>opt</sub> direct-abstract-declarator
20578 </pre>
20580 <pre>
20581 ( abstract-declarator )
20582 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list<sub>opt</sub>
20583 assignment-expression<sub>opt</sub> ]
20584 direct-abstract-declarator<sub>opt</sub> [ static type-qualifier-list<sub>opt</sub>
20585 assignment-expression ]
20586 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list static
20587 assignment-expression ]
20588 direct-abstract-declarator<sub>opt</sub> [ * ]
20589 direct-abstract-declarator<sub>opt</sub> ( parameter-type-list<sub>opt</sub> )
20590 </pre>
20592 <pre>
20593 identifier
20594 </pre>
20596 <pre>
20597 assignment-expression
20598 { initializer-list }
20599 { initializer-list , }
20600 </pre>
20602 <pre>
20603 designation<sub>opt</sub> initializer
20604 initializer-list , designation<sub>opt</sub> initializer
20605 </pre>
20607 <!--page 427 -->
20608 <pre>
20609 designator-list =
20610 </pre>
20612 <pre>
20613 designator
20614 designator-list designator
20615 </pre>
20617 <pre>
20618 [ constant-expression ]
20619 . identifier
20620 </pre>
20624 <pre>
20625 labeled-statement
20626 compound-statement
20627 expression-statement
20628 selection-statement
20629 iteration-statement
20630 jump-statement
20631 </pre>
20633 <pre>
20634 identifier : statement
20635 case constant-expression : statement
20636 default : statement
20637 </pre>
20639 <pre>
20640 { block-item-list<sub>opt</sub> }
20641 </pre>
20643 <pre>
20644 block-item
20645 block-item-list block-item
20646 </pre>
20648 <pre>
20649 declaration
20650 statement
20651 </pre>
20653 <pre>
20654 expression<sub>opt</sub> ;
20655 </pre>
20657 <!--page 428 -->
20658 <pre>
20659 if ( expression ) statement
20660 if ( expression ) statement else statement
20661 switch ( expression ) statement
20662 </pre>
20664 <pre>
20665 while ( expression ) statement
20666 do statement while ( expression ) ;
20667 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
20668 for ( declaration expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
20669 </pre>
20671 <pre>
20672 goto identifier ;
20673 continue ;
20674 break ;
20675 return expression<sub>opt</sub> ;
20676 </pre>
20680 <pre>
20681 external-declaration
20682 translation-unit external-declaration
20683 </pre>
20685 <pre>
20686 function-definition
20687 declaration
20688 </pre>
20690 <pre>
20691 declaration-specifiers declarator declaration-list<sub>opt</sub> compound-statement
20692 </pre>
20694 <pre>
20695 declaration
20696 declaration-list declaration
20697 </pre>
20701 <pre>
20702 group<sub>opt</sub>
20703 </pre>
20705 <pre>
20706 group-part
20707 group group-part
20708 </pre>
20710 <pre>
20711 if-section
20712 control-line
20713 text-line
20714 # non-directive
20715 </pre>
20717 <!--page 429 -->
20718 <pre>
20719 if-group elif-groups<sub>opt</sub> else-group<sub>opt</sub> endif-line
20720 </pre>
20722 <pre>
20723 # if constant-expression new-line group<sub>opt</sub>
20724 # ifdef identifier new-line group<sub>opt</sub>
20725 # ifndef identifier new-line group<sub>opt</sub>
20726 </pre>
20728 <pre>
20729 elif-group
20730 elif-groups elif-group
20731 </pre>
20733 <pre>
20734 # elif constant-expression new-line group<sub>opt</sub>
20735 </pre>
20737 <pre>
20738 # else new-line group<sub>opt</sub>
20739 </pre>
20741 <pre>
20742 # endif new-line
20743 </pre>
20745 <pre>
20746 # include pp-tokens new-line
20747 # define identifier replacement-list new-line
20748 # define identifier lparen identifier-list<sub>opt</sub> )
20749 replacement-list new-line
20750 # define identifier lparen ... ) replacement-list new-line
20751 # define identifier lparen identifier-list , ... )
20752 replacement-list new-line
20753 # undef identifier new-line
20754 # line pp-tokens new-line
20755 # error pp-tokens<sub>opt</sub> new-line
20756 # pragma pp-tokens<sub>opt</sub> new-line
20757 # new-line
20758 </pre>
20760 <pre>
20761 pp-tokens<sub>opt</sub> new-line
20762 </pre>
20764 <pre>
20765 pp-tokens new-line
20766 </pre>
20768 <pre>
20769 a ( character not immediately preceded by white-space
20770 </pre>
20772 <!--page 430 -->
20773 <pre>
20774 pp-tokens<sub>opt</sub>
20775 </pre>
20777 <pre>
20778 preprocessing-token
20779 pp-tokens preprocessing-token
20780 </pre>
20782 <!--page 431 -->
20783 <pre>
20784 the new-line character
20785 </pre>
20788 <pre>
20789 (informative)
20790 Library summary
20791 </pre>
20794 <pre>
20795 NDEBUG
20796 void assert(scalar expression);
20797 </pre>
20800 <!--page 432 -->
20801 <!--page 433 -->
20802 <pre>
20803 complex imaginary I
20804 _Complex_I _Imaginary_I
20805 #pragma STDC CX_LIMITED_RANGE on-off-switch
20806 double complex cacos(double complex z);
20807 float complex cacosf(float complex z);
20808 long double complex cacosl(long double complex z);
20809 double complex casin(double complex z);
20810 float complex casinf(float complex z);
20811 long double complex casinl(long double complex z);
20812 double complex catan(double complex z);
20813 float complex catanf(float complex z);
20814 long double complex catanl(long double complex z);
20815 double complex ccos(double complex z);
20816 float complex ccosf(float complex z);
20817 long double complex ccosl(long double complex z);
20818 double complex csin(double complex z);
20819 float complex csinf(float complex z);
20820 long double complex csinl(long double complex z);
20821 double complex ctan(double complex z);
20822 float complex ctanf(float complex z);
20823 long double complex ctanl(long double complex z);
20824 double complex cacosh(double complex z);
20825 float complex cacoshf(float complex z);
20826 long double complex cacoshl(long double complex z);
20827 double complex casinh(double complex z);
20828 float complex casinhf(float complex z);
20829 long double complex casinhl(long double complex z);
20830 double complex catanh(double complex z);
20831 float complex catanhf(float complex z);
20832 long double complex catanhl(long double complex z);
20833 double complex ccosh(double complex z);
20834 float complex ccoshf(float complex z);
20835 long double complex ccoshl(long double complex z);
20836 double complex csinh(double complex z);
20837 float complex csinhf(float complex z);
20838 long double complex csinhl(long double complex z);
20839 double complex ctanh(double complex z);
20840 float complex ctanhf(float complex z);
20841 long double complex ctanhl(long double complex z);
20842 double complex cexp(double complex z);
20843 float complex cexpf(float complex z);
20844 long double complex cexpl(long double complex z);
20845 double complex clog(double complex z);
20846 float complex clogf(float complex z);
20847 long double complex clogl(long double complex z);
20848 double cabs(double complex z);
20849 float cabsf(float complex z);
20850 long double cabsl(long double complex z);
20851 double complex cpow(double complex x, double complex y);
20852 float complex cpowf(float complex x, float complex y);
20853 long double complex cpowl(long double complex x,
20854 long double complex y);
20855 double complex csqrt(double complex z);
20856 float complex csqrtf(float complex z);
20857 long double complex csqrtl(long double complex z);
20858 double carg(double complex z);
20859 float cargf(float complex z);
20860 long double cargl(long double complex z);
20861 double cimag(double complex z);
20862 float cimagf(float complex z);
20863 long double cimagl(long double complex z);
20864 double complex conj(double complex z);
20865 float complex conjf(float complex z);
20866 long double complex conjl(long double complex z);
20867 double complex cproj(double complex z);
20868 float complex cprojf(float complex z);
20869 long double complex cprojl(long double complex z);
20870 double creal(double complex z);
20871 float crealf(float complex z);
20872 long double creall(long double complex z);
20873 </pre>
20876 <pre>
20877 int isalnum(int c);
20878 int isalpha(int c);
20879 int isblank(int c);
20880 int iscntrl(int c);
20881 int isdigit(int c);
20882 int isgraph(int c);
20883 int islower(int c);
20884 int isprint(int c);
20885 int ispunct(int c);
20886 int isspace(int c);
20887 int isupper(int c);
20888 int isxdigit(int c);
20889 int tolower(int c);
20890 int toupper(int c);
20891 </pre>
20894 <pre>
20895 EDOM EILSEQ ERANGE errno
20896 </pre>
20899 <!--page 434 -->
20900 <pre>
20901 fenv_t FE_OVERFLOW FE_TOWARDZERO
20902 fexcept_t FE_UNDERFLOW FE_UPWARD
20903 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
20904 FE_INEXACT FE_DOWNWARD
20905 FE_INVALID FE_TONEAREST
20906 #pragma STDC FENV_ACCESS on-off-switch
20907 int feclearexcept(int excepts);
20908 int fegetexceptflag(fexcept_t *flagp, int excepts);
20909 int feraiseexcept(int excepts);
20910 int fesetexceptflag(const fexcept_t *flagp,
20911 int excepts);
20912 int fetestexcept(int excepts);
20913 int fegetround(void);
20914 int fesetround(int round);
20915 int fegetenv(fenv_t *envp);
20916 int feholdexcept(fenv_t *envp);
20917 int fesetenv(const fenv_t *envp);
20918 int feupdateenv(const fenv_t *envp);
20919 </pre>
20922 <pre>
20923 FLT_ROUNDS DBL_MIN_EXP FLT_MAX
20924 FLT_EVAL_METHOD LDBL_MIN_EXP DBL_MAX
20925 FLT_RADIX FLT_MIN_10_EXP LDBL_MAX
20926 FLT_MANT_DIG DBL_MIN_10_EXP FLT_EPSILON
20927 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_EPSILON
20928 LDBL_MANT_DIG FLT_MAX_EXP LDBL_EPSILON
20929 DECIMAL_DIG DBL_MAX_EXP FLT_MIN
20930 FLT_DIG LDBL_MAX_EXP DBL_MIN
20931 DBL_DIG FLT_MAX_10_EXP LDBL_MIN
20932 LDBL_DIG DBL_MAX_10_EXP
20933 FLT_MIN_EXP LDBL_MAX_10_EXP
20934 </pre>
20937 <!--page 435 -->
20938 <pre>
20939 imaxdiv_t
20940 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
20941 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
20942 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
20943 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
20944 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
20945 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
20946 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
20947 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
20948 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
20949 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
20950 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
20951 intmax_t imaxabs(intmax_t j);
20952 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
20953 intmax_t strtoimax(const char * restrict nptr,
20954 char ** restrict endptr, int base);
20955 uintmax_t strtoumax(const char * restrict nptr,
20956 char ** restrict endptr, int base);
20957 intmax_t wcstoimax(const wchar_t * restrict nptr,
20958 wchar_t ** restrict endptr, int base);
20959 uintmax_t wcstoumax(const wchar_t * restrict nptr,
20960 wchar_t ** restrict endptr, int base);
20961 </pre>
20964 <pre>
20965 and bitor not_eq xor
20966 and_eq compl or xor_eq
20967 bitand not or_eq
20968 </pre>
20971 <pre>
20972 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
20973 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
20974 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
20975 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
20976 CHAR_MIN USHRT_MAX LONG_MAX
20977 </pre>
20980 <pre>
20981 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
20982 NULL LC_COLLATE LC_MONETARY LC_TIME
20983 char *setlocale(int category, const char *locale);
20984 struct lconv *localeconv(void);
20985 </pre>
20988 <!--page 436 -->
20989 <!--page 437 -->
20990 <!--page 438 -->
20991 <!--page 439 -->
20992 <!--page 440 -->
20993 <pre>
20994 float_t FP_INFINITE FP_FAST_FMAL
20995 double_t FP_NAN FP_ILOGB0
20996 HUGE_VAL FP_NORMAL FP_ILOGBNAN
20997 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
20998 HUGE_VALL FP_ZERO MATH_ERREXCEPT
20999 INFINITY FP_FAST_FMA math_errhandling
21000 NAN FP_FAST_FMAF
21001 #pragma STDC FP_CONTRACT on-off-switch
21002 int fpclassify(real-floating x);
21003 int isfinite(real-floating x);
21004 int isinf(real-floating x);
21005 int isnan(real-floating x);
21006 int isnormal(real-floating x);
21007 int signbit(real-floating x);
21008 double acos(double x);
21009 float acosf(float x);
21010 long double acosl(long double x);
21011 double asin(double x);
21012 float asinf(float x);
21013 long double asinl(long double x);
21014 double atan(double x);
21015 float atanf(float x);
21016 long double atanl(long double x);
21017 double atan2(double y, double x);
21018 float atan2f(float y, float x);
21019 long double atan2l(long double y, long double x);
21020 double cos(double x);
21021 float cosf(float x);
21022 long double cosl(long double x);
21023 double sin(double x);
21024 float sinf(float x);
21025 long double sinl(long double x);
21026 double tan(double x);
21027 float tanf(float x);
21028 long double tanl(long double x);
21029 double acosh(double x);
21030 float acoshf(float x);
21031 long double acoshl(long double x);
21032 double asinh(double x);
21033 float asinhf(float x);
21034 long double asinhl(long double x);
21035 double atanh(double x);
21036 float atanhf(float x);
21037 long double atanhl(long double x);
21038 double cosh(double x);
21039 float coshf(float x);
21040 long double coshl(long double x);
21041 double sinh(double x);
21042 float sinhf(float x);
21043 long double sinhl(long double x);
21044 double tanh(double x);
21045 float tanhf(float x);
21046 long double tanhl(long double x);
21047 double exp(double x);
21048 float expf(float x);
21049 long double expl(long double x);
21050 double exp2(double x);
21051 float exp2f(float x);
21052 long double exp2l(long double x);
21053 double expm1(double x);
21054 float expm1f(float x);
21055 long double expm1l(long double x);
21056 double frexp(double value, int *exp);
21057 float frexpf(float value, int *exp);
21058 long double frexpl(long double value, int *exp);
21059 int ilogb(double x);
21060 int ilogbf(float x);
21061 int ilogbl(long double x);
21062 double ldexp(double x, int exp);
21063 float ldexpf(float x, int exp);
21064 long double ldexpl(long double x, int exp);
21065 double log(double x);
21066 float logf(float x);
21067 long double logl(long double x);
21068 double log10(double x);
21069 float log10f(float x);
21070 long double log10l(long double x);
21071 double log1p(double x);
21072 float log1pf(float x);
21073 long double log1pl(long double x);
21074 double log2(double x);
21075 float log2f(float x);
21076 long double log2l(long double x);
21077 double logb(double x);
21078 float logbf(float x);
21079 long double logbl(long double x);
21080 double modf(double value, double *iptr);
21081 float modff(float value, float *iptr);
21082 long double modfl(long double value, long double *iptr);
21083 double scalbn(double x, int n);
21084 float scalbnf(float x, int n);
21085 long double scalbnl(long double x, int n);
21086 double scalbln(double x, long int n);
21087 float scalblnf(float x, long int n);
21088 long double scalblnl(long double x, long int n);
21089 double cbrt(double x);
21090 float cbrtf(float x);
21091 long double cbrtl(long double x);
21092 double fabs(double x);
21093 float fabsf(float x);
21094 long double fabsl(long double x);
21095 double hypot(double x, double y);
21096 float hypotf(float x, float y);
21097 long double hypotl(long double x, long double y);
21098 double pow(double x, double y);
21099 float powf(float x, float y);
21100 long double powl(long double x, long double y);
21101 double sqrt(double x);
21102 float sqrtf(float x);
21103 long double sqrtl(long double x);
21104 double erf(double x);
21105 float erff(float x);
21106 long double erfl(long double x);
21107 double erfc(double x);
21108 float erfcf(float x);
21109 long double erfcl(long double x);
21110 double lgamma(double x);
21111 float lgammaf(float x);
21112 long double lgammal(long double x);
21113 double tgamma(double x);
21114 float tgammaf(float x);
21115 long double tgammal(long double x);
21116 double ceil(double x);
21117 float ceilf(float x);
21118 long double ceill(long double x);
21119 double floor(double x);
21120 float floorf(float x);
21121 long double floorl(long double x);
21122 double nearbyint(double x);
21123 float nearbyintf(float x);
21124 long double nearbyintl(long double x);
21125 double rint(double x);
21126 float rintf(float x);
21127 long double rintl(long double x);
21128 long int lrint(double x);
21129 long int lrintf(float x);
21130 long int lrintl(long double x);
21131 long long int llrint(double x);
21132 long long int llrintf(float x);
21133 long long int llrintl(long double x);
21134 double round(double x);
21135 float roundf(float x);
21136 long double roundl(long double x);
21137 long int lround(double x);
21138 long int lroundf(float x);
21139 long int lroundl(long double x);
21140 long long int llround(double x);
21141 long long int llroundf(float x);
21142 long long int llroundl(long double x);
21143 double trunc(double x);
21144 float truncf(float x);
21145 long double truncl(long double x);
21146 double fmod(double x, double y);
21147 float fmodf(float x, float y);
21148 long double fmodl(long double x, long double y);
21149 double remainder(double x, double y);
21150 float remainderf(float x, float y);
21151 long double remainderl(long double x, long double y);
21152 double remquo(double x, double y, int *quo);
21153 float remquof(float x, float y, int *quo);
21154 long double remquol(long double x, long double y,
21155 int *quo);
21156 double copysign(double x, double y);
21157 float copysignf(float x, float y);
21158 long double copysignl(long double x, long double y);
21159 double nan(const char *tagp);
21160 float nanf(const char *tagp);
21161 long double nanl(const char *tagp);
21162 double nextafter(double x, double y);
21163 float nextafterf(float x, float y);
21164 long double nextafterl(long double x, long double y);
21165 double nexttoward(double x, long double y);
21166 float nexttowardf(float x, long double y);
21167 long double nexttowardl(long double x, long double y);
21168 double fdim(double x, double y);
21169 float fdimf(float x, float y);
21170 long double fdiml(long double x, long double y);
21171 double fmax(double x, double y);
21172 float fmaxf(float x, float y);
21173 long double fmaxl(long double x, long double y);
21174 double fmin(double x, double y);
21175 float fminf(float x, float y);
21176 long double fminl(long double x, long double y);
21177 double fma(double x, double y, double z);
21178 float fmaf(float x, float y, float z);
21179 long double fmal(long double x, long double y,
21180 long double z);
21181 int isgreater(real-floating x, real-floating y);
21182 int isgreaterequal(real-floating x, real-floating y);
21183 int isless(real-floating x, real-floating y);
21184 int islessequal(real-floating x, real-floating y);
21185 int islessgreater(real-floating x, real-floating y);
21186 int isunordered(real-floating x, real-floating y);
21187 </pre>
21190 <pre>
21191 jmp_buf
21192 int setjmp(jmp_buf env);
21193 void longjmp(jmp_buf env, int val);
21194 </pre>
21197 <pre>
21198 sig_atomic_t SIG_IGN SIGILL SIGTERM
21199 SIG_DFL SIGABRT SIGINT
21200 SIG_ERR SIGFPE SIGSEGV
21201 void (*signal(int sig, void (*func)(int)))(int);
21202 int raise(int sig);
21203 </pre>
21206 <pre>
21207 va_list
21208 type va_arg(va_list ap, type);
21209 void va_copy(va_list dest, va_list src);
21210 void va_end(va_list ap);
21211 void va_start(va_list ap, parmN);
21212 </pre>
21215 <!--page 441 -->
21216 <pre>
21217 bool
21218 true
21219 false
21220 __bool_true_false_are_defined
21221 </pre>
21224 <pre>
21225 ptrdiff_t size_t wchar_t NULL
21226 offsetof(type, member-designator)
21227 </pre>
21230 <pre>
21231 intN_t INT_LEASTN_MIN PTRDIFF_MAX
21232 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
21233 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
21234 uint_leastN_t INT_FASTN_MIN SIZE_MAX
21235 int_fastN_t INT_FASTN_MAX WCHAR_MIN
21236 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
21237 intptr_t INTPTR_MIN WINT_MIN
21238 uintptr_t INTPTR_MAX WINT_MAX
21239 intmax_t UINTPTR_MAX INTN_C(value)
21240 uintmax_t INTMAX_MIN UINTN_C(value)
21241 INTN_MIN INTMAX_MAX INTMAX_C(value)
21242 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
21243 UINTN_MAX PTRDIFF_MIN
21244 </pre>
21247 <!--page 442 -->
21248 <!--page 443 -->
21249 <pre>
21250 size_t _IOLBF FILENAME_MAX TMP_MAX
21251 FILE _IONBF L_tmpnam stderr
21252 fpos_t BUFSIZ SEEK_CUR stdin
21253 NULL EOF SEEK_END stdout
21254 _IOFBF FOPEN_MAX SEEK_SET
21255 int remove(const char *filename);
21256 int rename(const char *old, const char *new);
21257 FILE *tmpfile(void);
21258 char *tmpnam(char *s);
21259 int fclose(FILE *stream);
21260 int fflush(FILE *stream);
21261 FILE *fopen(const char * restrict filename,
21262 const char * restrict mode);
21263 FILE *freopen(const char * restrict filename,
21264 const char * restrict mode,
21265 FILE * restrict stream);
21266 void setbuf(FILE * restrict stream,
21267 char * restrict buf);
21268 int setvbuf(FILE * restrict stream,
21269 char * restrict buf,
21270 int mode, size_t size);
21271 int fprintf(FILE * restrict stream,
21272 const char * restrict format, ...);
21273 int fscanf(FILE * restrict stream,
21274 const char * restrict format, ...);
21275 int printf(const char * restrict format, ...);
21276 int scanf(const char * restrict format, ...);
21277 int snprintf(char * restrict s, size_t n,
21278 const char * restrict format, ...);
21279 int sprintf(char * restrict s,
21280 const char * restrict format, ...);
21281 int sscanf(const char * restrict s,
21282 const char * restrict format, ...);
21283 int vfprintf(FILE * restrict stream,
21284 const char * restrict format, va_list arg);
21285 int vfscanf(FILE * restrict stream,
21286 const char * restrict format, va_list arg);
21287 int vprintf(const char * restrict format, va_list arg);
21288 int vscanf(const char * restrict format, va_list arg);
21289 int vsnprintf(char * restrict s, size_t n,
21290 const char * restrict format, va_list arg);
21291 int vsprintf(char * restrict s,
21292 const char * restrict format, va_list arg);
21293 int vsscanf(const char * restrict s,
21294 const char * restrict format, va_list arg);
21295 int fgetc(FILE *stream);
21296 char *fgets(char * restrict s, int n,
21297 FILE * restrict stream);
21298 int fputc(int c, FILE *stream);
21299 int fputs(const char * restrict s,
21300 FILE * restrict stream);
21301 int getc(FILE *stream);
21302 int getchar(void);
21303 char *gets(char *s);
21304 int putc(int c, FILE *stream);
21305 int putchar(int c);
21306 int puts(const char *s);
21307 int ungetc(int c, FILE *stream);
21308 size_t fread(void * restrict ptr,
21309 size_t size, size_t nmemb,
21310 FILE * restrict stream);
21311 size_t fwrite(const void * restrict ptr,
21312 size_t size, size_t nmemb,
21313 FILE * restrict stream);
21314 int fgetpos(FILE * restrict stream,
21315 fpos_t * restrict pos);
21316 int fseek(FILE *stream, long int offset, int whence);
21317 int fsetpos(FILE *stream, const fpos_t *pos);
21318 long int ftell(FILE *stream);
21319 void rewind(FILE *stream);
21320 void clearerr(FILE *stream);
21321 int feof(FILE *stream);
21322 int ferror(FILE *stream);
21323 void perror(const char *s);
21324 </pre>
21327 <!--page 444 -->
21328 <!--page 445 -->
21329 <pre>
21330 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
21331 wchar_t lldiv_t EXIT_SUCCESS
21332 div_t NULL RAND_MAX
21333 double atof(const char *nptr);
21334 int atoi(const char *nptr);
21335 long int atol(const char *nptr);
21336 long long int atoll(const char *nptr);
21337 double strtod(const char * restrict nptr,
21338 char ** restrict endptr);
21339 float strtof(const char * restrict nptr,
21340 char ** restrict endptr);
21341 long double strtold(const char * restrict nptr,
21342 char ** restrict endptr);
21343 long int strtol(const char * restrict nptr,
21344 char ** restrict endptr, int base);
21345 long long int strtoll(const char * restrict nptr,
21346 char ** restrict endptr, int base);
21347 unsigned long int strtoul(
21348 const char * restrict nptr,
21349 char ** restrict endptr, int base);
21350 unsigned long long int strtoull(
21351 const char * restrict nptr,
21352 char ** restrict endptr, int base);
21353 int rand(void);
21354 void srand(unsigned int seed);
21355 void *calloc(size_t nmemb, size_t size);
21356 void free(void *ptr);
21357 void *malloc(size_t size);
21358 void *realloc(void *ptr, size_t size);
21359 void abort(void);
21360 int atexit(void (*func)(void));
21361 void exit(int status);
21362 void _Exit(int status);
21363 char *getenv(const char *name);
21364 int system(const char *string);
21365 void *bsearch(const void *key, const void *base,
21366 size_t nmemb, size_t size,
21367 int (*compar)(const void *, const void *));
21368 void qsort(void *base, size_t nmemb, size_t size,
21369 int (*compar)(const void *, const void *));
21370 int abs(int j);
21371 long int labs(long int j);
21372 long long int llabs(long long int j);
21373 div_t div(int numer, int denom);
21374 ldiv_t ldiv(long int numer, long int denom);
21375 lldiv_t lldiv(long long int numer,
21376 long long int denom);
21377 int mblen(const char *s, size_t n);
21378 int mbtowc(wchar_t * restrict pwc,
21379 const char * restrict s, size_t n);
21380 int wctomb(char *s, wchar_t wchar);
21381 size_t mbstowcs(wchar_t * restrict pwcs,
21382 const char * restrict s, size_t n);
21383 size_t wcstombs(char * restrict s,
21384 const wchar_t * restrict pwcs, size_t n);
21385 </pre>
21388 <!--page 446 -->
21389 <pre>
21390 size_t
21391 NULL
21392 void *memcpy(void * restrict s1,
21393 const void * restrict s2, size_t n);
21394 void *memmove(void *s1, const void *s2, size_t n);
21395 char *strcpy(char * restrict s1,
21396 const char * restrict s2);
21397 char *strncpy(char * restrict s1,
21398 const char * restrict s2, size_t n);
21399 char *strcat(char * restrict s1,
21400 const char * restrict s2);
21401 char *strncat(char * restrict s1,
21402 const char * restrict s2, size_t n);
21403 int memcmp(const void *s1, const void *s2, size_t n);
21404 int strcmp(const char *s1, const char *s2);
21405 int strcoll(const char *s1, const char *s2);
21406 int strncmp(const char *s1, const char *s2, size_t n);
21407 size_t strxfrm(char * restrict s1,
21408 const char * restrict s2, size_t n);
21409 void *memchr(const void *s, int c, size_t n);
21410 char *strchr(const char *s, int c);
21411 size_t strcspn(const char *s1, const char *s2);
21412 char *strpbrk(const char *s1, const char *s2);
21413 char *strrchr(const char *s, int c);
21414 size_t strspn(const char *s1, const char *s2);
21415 char *strstr(const char *s1, const char *s2);
21416 char *strtok(char * restrict s1,
21417 const char * restrict s2);
21418 void *memset(void *s, int c, size_t n);
21419 char *strerror(int errnum);
21420 size_t strlen(const char *s);
21421 </pre>
21424 <pre>
21425 acos sqrt fmod nextafter
21426 asin fabs frexp nexttoward
21427 atan atan2 hypot remainder
21428 acosh cbrt ilogb remquo
21429 asinh ceil ldexp rint
21430 atanh copysign lgamma round
21431 cos erf llrint scalbn
21432 sin erfc llround scalbln
21433 tan exp2 log10 tgamma
21434 cosh expm1 log1p trunc
21435 sinh fdim log2 carg
21436 tanh floor logb cimag
21437 exp fma lrint conj
21438 log fmax lround cproj
21439 pow fmin nearbyint creal
21440 </pre>
21443 <!--page 447 -->
21444 <pre>
21445 NULL size_t time_t
21446 CLOCKS_PER_SEC clock_t struct tm
21447 clock_t clock(void);
21448 double difftime(time_t time1, time_t time0);
21449 time_t mktime(struct tm *timeptr);
21450 time_t time(time_t *timer);
21451 char *asctime(const struct tm *timeptr);
21452 char *ctime(const time_t *timer);
21453 struct tm *gmtime(const time_t *timer);
21454 struct tm *localtime(const time_t *timer);
21455 size_t strftime(char * restrict s,
21456 size_t maxsize,
21457 const char * restrict format,
21458 const struct tm * restrict timeptr);
21459 </pre>
21461 <h3><a name="B.23" href="#B.23">B.23 Extended multibyte/wide character utilities <wchar.h></a></h3>
21462 <!--page 448 -->
21463 <!--page 449 -->
21464 <pre>
21465 wchar_t wint_t WCHAR_MAX
21466 size_t struct tm WCHAR_MIN
21467 mbstate_t NULL WEOF
21468 int fwprintf(FILE * restrict stream,
21469 const wchar_t * restrict format, ...);
21470 int fwscanf(FILE * restrict stream,
21471 const wchar_t * restrict format, ...);
21472 int swprintf(wchar_t * restrict s, size_t n,
21473 const wchar_t * restrict format, ...);
21474 int swscanf(const wchar_t * restrict s,
21475 const wchar_t * restrict format, ...);
21476 int vfwprintf(FILE * restrict stream,
21477 const wchar_t * restrict format, va_list arg);
21478 int vfwscanf(FILE * restrict stream,
21479 const wchar_t * restrict format, va_list arg);
21480 int vswprintf(wchar_t * restrict s, size_t n,
21481 const wchar_t * restrict format, va_list arg);
21482 int vswscanf(const wchar_t * restrict s,
21483 const wchar_t * restrict format, va_list arg);
21484 int vwprintf(const wchar_t * restrict format,
21485 va_list arg);
21486 int vwscanf(const wchar_t * restrict format,
21487 va_list arg);
21488 int wprintf(const wchar_t * restrict format, ...);
21489 int wscanf(const wchar_t * restrict format, ...);
21490 wint_t fgetwc(FILE *stream);
21491 wchar_t *fgetws(wchar_t * restrict s, int n,
21492 FILE * restrict stream);
21493 wint_t fputwc(wchar_t c, FILE *stream);
21494 int fputws(const wchar_t * restrict s,
21495 FILE * restrict stream);
21496 int fwide(FILE *stream, int mode);
21497 wint_t getwc(FILE *stream);
21498 wint_t getwchar(void);
21499 wint_t putwc(wchar_t c, FILE *stream);
21500 wint_t putwchar(wchar_t c);
21501 wint_t ungetwc(wint_t c, FILE *stream);
21502 double wcstod(const wchar_t * restrict nptr,
21503 wchar_t ** restrict endptr);
21504 float wcstof(const wchar_t * restrict nptr,
21505 wchar_t ** restrict endptr);
21506 long double wcstold(const wchar_t * restrict nptr,
21507 wchar_t ** restrict endptr);
21508 long int wcstol(const wchar_t * restrict nptr,
21509 wchar_t ** restrict endptr, int base);
21510 long long int wcstoll(const wchar_t * restrict nptr,
21511 wchar_t ** restrict endptr, int base);
21512 unsigned long int wcstoul(const wchar_t * restrict nptr,
21513 wchar_t ** restrict endptr, int base);
21514 unsigned long long int wcstoull(
21515 const wchar_t * restrict nptr,
21516 wchar_t ** restrict endptr, int base);
21517 wchar_t *wcscpy(wchar_t * restrict s1,
21518 const wchar_t * restrict s2);
21519 wchar_t *wcsncpy(wchar_t * restrict s1,
21520 const wchar_t * restrict s2, size_t n);
21521 wchar_t *wmemcpy(wchar_t * restrict s1,
21522 const wchar_t * restrict s2, size_t n);
21523 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
21524 size_t n);
21525 wchar_t *wcscat(wchar_t * restrict s1,
21526 const wchar_t * restrict s2);
21527 wchar_t *wcsncat(wchar_t * restrict s1,
21528 const wchar_t * restrict s2, size_t n);
21529 int wcscmp(const wchar_t *s1, const wchar_t *s2);
21530 int wcscoll(const wchar_t *s1, const wchar_t *s2);
21531 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
21532 size_t n);
21533 size_t wcsxfrm(wchar_t * restrict s1,
21534 const wchar_t * restrict s2, size_t n);
21535 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
21536 size_t n);
21537 wchar_t *wcschr(const wchar_t *s, wchar_t c);
21538 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
21539 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2); *
21540 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
21541 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
21542 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
21543 wchar_t *wcstok(wchar_t * restrict s1,
21544 const wchar_t * restrict s2,
21545 wchar_t ** restrict ptr);
21546 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
21547 size_t wcslen(const wchar_t *s);
21548 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
21549 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
21550 const wchar_t * restrict format,
21551 const struct tm * restrict timeptr);
21552 wint_t btowc(int c);
21553 int wctob(wint_t c);
21554 int mbsinit(const mbstate_t *ps);
21555 size_t mbrlen(const char * restrict s, size_t n,
21556 mbstate_t * restrict ps);
21557 size_t mbrtowc(wchar_t * restrict pwc,
21558 const char * restrict s, size_t n,
21559 mbstate_t * restrict ps);
21560 size_t wcrtomb(char * restrict s, wchar_t wc,
21561 mbstate_t * restrict ps);
21562 size_t mbsrtowcs(wchar_t * restrict dst,
21563 const char ** restrict src, size_t len,
21564 mbstate_t * restrict ps);
21565 size_t wcsrtombs(char * restrict dst,
21566 const wchar_t ** restrict src, size_t len,
21567 mbstate_t * restrict ps);
21568 </pre>
21570 <h3><a name="B.24" href="#B.24">B.24 Wide character classification and mapping utilities <wctype.h></a></h3>
21571 <!--page 450 -->
21572 <!--page 451 -->
21573 <pre>
21574 wint_t wctrans_t wctype_t WEOF
21575 int iswalnum(wint_t wc);
21576 int iswalpha(wint_t wc);
21577 int iswblank(wint_t wc);
21578 int iswcntrl(wint_t wc);
21579 int iswdigit(wint_t wc);
21580 int iswgraph(wint_t wc);
21581 int iswlower(wint_t wc);
21582 int iswprint(wint_t wc);
21583 int iswpunct(wint_t wc);
21584 int iswspace(wint_t wc);
21585 int iswupper(wint_t wc);
21586 int iswxdigit(wint_t wc);
21587 int iswctype(wint_t wc, wctype_t desc);
21588 wctype_t wctype(const char *property);
21589 wint_t towlower(wint_t wc);
21590 wint_t towupper(wint_t wc);
21591 wint_t towctrans(wint_t wc, wctrans_t desc);
21592 wctrans_t wctrans(const char *property);
21593 </pre>
21596 <pre>
21597 (informative)
21598 Sequence points
21599 </pre>
21600 <p><!--para 1 -->
21602 <ul>
21603 <li> The call to a function, after the arguments have been evaluated (<a href="#6.5.2.2">6.5.2.2</a>).
21604 <li> The end of the first operand of the following operators: logical AND && (<a href="#6.5.13">6.5.13</a>);
21605 logical OR || (<a href="#6.5.14">6.5.14</a>); conditional ? (<a href="#6.5.15">6.5.15</a>); comma , (<a href="#6.5.17">6.5.17</a>).
21607 <li> The end of a full expression: an initializer (<a href="#6.7.8">6.7.8</a>); the expression in an expression
21608 statement (<a href="#6.8.3">6.8.3</a>); the controlling expression of a selection statement (if or switch)
21609 (<a href="#6.8.4">6.8.4</a>); the controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the
21610 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the expression in a return statement
21613 <li> After the actions associated with each formatted input/output function conversion
21615 <li> Immediately before and immediately after each call to a comparison function, and
21616 also between any call to a comparison function and any movement of the objects
21618 <!--page 452 -->
21619 </ul>
21622 <pre>
21623 (normative)
21624 Universal character names for identifiers
21625 </pre>
21626 <p><!--para 1 -->
21627 This clause lists the hexadecimal code values that are valid in universal character names
21628 in identifiers.
21629 <p><!--para 2 -->
21630 This table is reproduced unchanged from ISO/IEC TR 10176:1998, produced by ISO/IEC
21631 JTC 1/SC 22/WG 20, except for the omission of ranges that are part of the basic character
21632 sets.
21633 Latin: 00AA, 00BA, 00C0-00D6, 00D8-00F6, 00F8-01F5, 01FA-0217,
21634 <pre>
21635 0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F
21636 </pre>
21637 Greek: 0386, 0388-038A, 038C, 038E-03A1, 03A3-03CE, 03D0-03D6,
21638 <pre>
21639 03DA, 03DC, 03DE, 03E0, 03E2-03F3, 1F00-1F15, 1F18-1F1D,
21640 1F20-1F45, 1F48-1F4D, 1F50-1F57, 1F59, 1F5B, 1F5D,
21641 1F5F-1F7D, 1F80-1FB4, 1FB6-1FBC, 1FC2-1FC4, 1FC6-1FCC,
21642 1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC
21643 </pre>
21644 Cyrillic: 0401-040C, 040E-044F, 0451-045C, 045E-0481, 0490-04C4,
21645 <pre>
21646 04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9
21647 </pre>
21648 Armenian: 0531-0556, 0561-0587
21649 Hebrew: 05B0-05B9, 05BB-05BD, 05BF, 05C1-05C2, 05D0-05EA,
21650 <pre>
21651 05F0-05F2
21652 </pre>
21653 Arabic: 0621-063A, 0640-0652, 0670-06B7, 06BA-06BE, 06C0-06CE,
21654 <pre>
21655 06D0-06DC, 06E5-06E8, 06EA-06ED
21656 </pre>
21657 Devanagari: 0901-0903, 0905-0939, 093E-094D, 0950-0952, 0958-0963
21658 Bengali: 0981-0983, 0985-098C, 098F-0990, 0993-09A8, 09AA-09B0,
21659 <pre>
21660 09B2, 09B6-09B9, 09BE-09C4, 09C7-09C8, 09CB-09CD,
21661 09DC-09DD, 09DF-09E3, 09F0-09F1
21662 </pre>
21663 Gurmukhi: 0A02, 0A05-0A0A, 0A0F-0A10, 0A13-0A28, 0A2A-0A30,
21664 <pre>
21665 0A32-0A33, 0A35-0A36, 0A38-0A39, 0A3E-0A42, 0A47-0A48,
21666 0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74
21667 </pre>
21668 Gujarati: 0A81-0A83, 0A85-0A8B, 0A8D, 0A8F-0A91, 0A93-0AA8,
21669 <pre>
21670 0AAA-0AB0, 0AB2-0AB3, 0AB5-0AB9, 0ABD-0AC5,
21671 0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0
21672 </pre>
21673 Oriya: 0B01-0B03, 0B05-0B0C, 0B0F-0B10, 0B13-0B28, 0B2A-0B30,
21674 <!--page 453 -->
21675 <pre>
21676 0B32-0B33, 0B36-0B39, 0B3E-0B43, 0B47-0B48, 0B4B-0B4D,
21677 0B5C-0B5D, 0B5F-0B61
21678 </pre>
21679 Tamil: 0B82-0B83, 0B85-0B8A, 0B8E-0B90, 0B92-0B95, 0B99-0B9A,
21680 <pre>
21681 0B9C, 0B9E-0B9F, 0BA3-0BA4, 0BA8-0BAA, 0BAE-0BB5,
21682 0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD
21683 </pre>
21684 Telugu: 0C01-0C03, 0C05-0C0C, 0C0E-0C10, 0C12-0C28, 0C2A-0C33,
21685 <pre>
21686 0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61
21687 </pre>
21688 Kannada: 0C82-0C83, 0C85-0C8C, 0C8E-0C90, 0C92-0CA8, 0CAA-0CB3,
21689 <pre>
21690 0CB5-0CB9, 0CBE-0CC4, 0CC6-0CC8, 0CCA-0CCD, 0CDE,
21691 0CE0-0CE1
21692 </pre>
21693 Malayalam: 0D02-0D03, 0D05-0D0C, 0D0E-0D10, 0D12-0D28, 0D2A-0D39,
21694 <pre>
21695 0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61
21696 </pre>
21697 Thai: 0E01-0E3A, 0E40-0E5B
21698 Lao: 0E81-0E82, 0E84, 0E87-0E88, 0E8A, 0E8D, 0E94-0E97,
21699 <pre>
21700 0E99-0E9F, 0EA1-0EA3, 0EA5, 0EA7, 0EAA-0EAB,
21701 0EAD-0EAE, 0EB0-0EB9, 0EBB-0EBD, 0EC0-0EC4, 0EC6,
21702 0EC8-0ECD, 0EDC-0EDD
21703 </pre>
21704 Tibetan: 0F00, 0F18-0F19, 0F35, 0F37, 0F39, 0F3E-0F47, 0F49-0F69,
21705 <pre>
21706 0F71-0F84, 0F86-0F8B, 0F90-0F95, 0F97, 0F99-0FAD,
21707 0FB1-0FB7, 0FB9
21708 </pre>
21709 Georgian: 10A0-10C5, 10D0-10F6
21710 Hiragana: 3041-3093, 309B-309C
21711 Katakana: 30A1-30F6, 30FB-30FC
21712 Bopomofo: 3105-312C
21713 CJK Unified Ideographs: 4E00-9FA5
21714 Hangul: AC00-D7A3
21715 Digits: 0660-0669, 06F0-06F9, 0966-096F, 09E6-09EF, 0A66-0A6F,
21716 <pre>
21717 0AE6-0AEF, 0B66-0B6F, 0BE7-0BEF, 0C66-0C6F, 0CE6-0CEF,
21718 0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33
21719 </pre>
21720 Special characters: 00B5, 00B7, 02B0-02B8, 02BB, 02BD-02C1, 02D0-02D1,
21721 <!--page 454 -->
21722 <pre>
21723 02E0-02E4, 037A, 0559, 093D, 0B3D, 1FBE, 203F-2040, 2102,
21724 2107, 210A-2113, 2115, 2118-211D, 2124, 2126, 2128, 212A-2131,
21725 2133-2138, 2160-2182, 3005-3007, 3021-3029
21726 </pre>
21729 <pre>
21730 (informative)
21731 Implementation limits
21732 </pre>
21733 <p><!--para 1 -->
21734 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
21735 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
21736 with the same sign. The values shall all be constant expressions suitable for use in #if
21737 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
21738 <pre>
21739 #define CHAR_BIT 8
21740 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
21741 #define CHAR_MIN 0 or SCHAR_MIN
21742 #define INT_MAX +32767
21743 #define INT_MIN -32767
21744 #define LONG_MAX +2147483647
21745 #define LONG_MIN -2147483647
21746 #define LLONG_MAX +9223372036854775807
21747 #define LLONG_MIN -9223372036854775807
21748 #define MB_LEN_MAX 1
21749 #define SCHAR_MAX +127
21750 #define SCHAR_MIN -127
21751 #define SHRT_MAX +32767
21752 #define SHRT_MIN -32767
21753 #define UCHAR_MAX 255
21754 #define USHRT_MAX 65535
21755 #define UINT_MAX 65535
21756 #define ULONG_MAX 4294967295
21757 #define ULLONG_MAX 18446744073709551615
21758 </pre>
21759 <p><!--para 2 -->
21760 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
21761 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
21762 directives; all floating values shall be constant expressions. The components are
21764 <p><!--para 3 -->
21765 The values given in the following list shall be replaced by implementation-defined
21766 expressions:
21767 <pre>
21768 #define FLT_EVAL_METHOD
21769 #define FLT_ROUNDS
21770 </pre>
21771 <p><!--para 4 -->
21772 The values given in the following list shall be replaced by implementation-defined
21773 constant expressions that are greater or equal in magnitude (absolute value) to those
21774 shown, with the same sign:
21775 <!--page 455 -->
21776 <pre>
21777 #define DBL_DIG 10
21778 #define DBL_MANT_DIG
21779 #define DBL_MAX_10_EXP +37
21780 #define DBL_MAX_EXP
21781 #define DBL_MIN_10_EXP -37
21782 #define DBL_MIN_EXP
21783 #define DECIMAL_DIG 10
21784 #define FLT_DIG 6
21785 #define FLT_MANT_DIG
21786 #define FLT_MAX_10_EXP +37
21787 #define FLT_MAX_EXP
21788 #define FLT_MIN_10_EXP -37
21789 #define FLT_MIN_EXP
21790 #define FLT_RADIX 2
21791 #define LDBL_DIG 10
21792 #define LDBL_MANT_DIG
21793 #define LDBL_MAX_10_EXP +37
21794 #define LDBL_MAX_EXP
21795 #define LDBL_MIN_10_EXP -37
21796 #define LDBL_MIN_EXP
21797 </pre>
21798 <p><!--para 5 -->
21799 The values given in the following list shall be replaced by implementation-defined
21800 constant expressions with values that are greater than or equal to those shown:
21801 <pre>
21802 #define DBL_MAX 1E+37
21803 #define FLT_MAX 1E+37
21804 #define LDBL_MAX 1E+37
21805 </pre>
21806 <p><!--para 6 -->
21807 The values given in the following list shall be replaced by implementation-defined
21808 constant expressions with (positive) values that are less than or equal to those shown:
21809 <!--page 456 -->
21810 <pre>
21811 #define DBL_EPSILON 1E-9
21812 #define DBL_MIN 1E-37
21813 #define FLT_EPSILON 1E-5
21814 #define FLT_MIN 1E-37
21815 #define LDBL_EPSILON 1E-9
21816 #define LDBL_MIN 1E-37
21817 </pre>
21820 <pre>
21821 (normative)
21822 IEC 60559 floating-point arithmetic
21823 </pre>
21826 <p><!--para 1 -->
21827 This annex specifies C language support for the IEC 60559 floating-point standard. The
21828 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
21829 microprocessor systems, second edition (IEC 60559:1989), previously designated
21830 IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
21831 (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
21832 Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
21833 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
21834 standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
21835 defines __STDC_IEC_559__ shall conform to the specifications in this annex. Where
21836 a binding between the C language and IEC 60559 is indicated, the IEC 60559-specified
21837 behavior is adopted by reference, unless stated otherwise.
21840 <p><!--para 1 -->
21841 The C floating types match the IEC 60559 formats as follows:
21842 <ul>
21843 <li> The float type matches the IEC 60559 single format.
21844 <li> The double type matches the IEC 60559 double format.
21845 <li> The long double type matches an IEC 60559 extended format,<sup><a href="#note307"><b>307)</b></a></sup> else a
21846 non-IEC 60559 extended format, else the IEC 60559 double format.
21847 </ul>
21848 Any non-IEC 60559 extended format used for the long double type shall have more
21849 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note308"><b>308)</b></a></sup>
21850 <p><b>Recommended practice</b>
21851 <p><!--para 2 -->
21852 The long double type should match an IEC 60559 extended format.
21857 <!--page 457 -->
21859 <p><b>Footnotes</b>
21860 <p><small><a name="note307" href="#note307">307)</a> ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
21861 and quadruple 128-bit IEC 60559 formats.
21862 </small>
21863 <p><small><a name="note308" href="#note308">308)</a> A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
21864 all double values.
21865 </small>
21868 <p><!--para 1 -->
21869 This specification does not define the behavior of signaling NaNs.<sup><a href="#note309"><b>309)</b></a></sup> It generally uses
21870 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
21871 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
21873 <p><b>Footnotes</b>
21874 <p><small><a name="note309" href="#note309">309)</a> Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
21875 sufficient for closure of the arithmetic.
21876 </small>
21879 <p><!--para 1 -->
21880 C operators and functions provide IEC 60559 required and recommended facilities as
21881 listed below.
21882 <ul>
21883 <li> The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
21884 divide operations.
21885 <li> The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
21886 <li> The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
21887 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
21888 with additional information.
21889 <li> The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
21890 floating-point number to an integer value (in the same precision). The nearbyint
21891 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
21892 Appendix to ANSI/IEEE 854.
21893 <li> The conversions for floating types provide the IEC 60559 conversions between
21894 floating-point precisions.
21895 <li> The conversions from integer to floating types provide the IEC 60559 conversions
21896 from integer to floating point.
21897 <li> The conversions from floating to integer types provide IEC 60559-like conversions
21898 but always round toward zero.
21899 <li> The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
21900 conversions, which honor the directed rounding mode, from floating point to the
21901 long int and long long int integer formats. The lrint and llrint
21902 functions can be used to implement IEC 60559 conversions from floating to other
21903 integer formats.
21904 <li> The translation time conversion of floating constants and the strtod, strtof,
21905 strtold, fprintf, fscanf, and related library functions in <a href="#7.20"><stdlib.h></a>,
21906 <a href="#7.19"><stdio.h></a>, and <a href="#7.24"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
21907 strtold function in <a href="#7.20"><stdlib.h></a> provides the conv function recommended in the
21908 Appendix to ANSI/IEEE 854.
21910 <!--page 458 -->
21911 <li> The relational and equality operators provide IEC 60559 comparisons. IEC 60559
21912 identifies a need for additional comparison predicates to facilitate writing code that
21913 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
21915 supplement the language operators to address this need. The islessgreater and
21916 isunordered macros provide respectively a quiet version of the <> predicate and
21917 the unordered predicate recommended in the Appendix to IEC 60559.
21918 <li> The feclearexcept, feraiseexcept, and fetestexcept functions in
21919 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
21920 exception status flags. The fegetexceptflag and fesetexceptflag
21921 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
21922 one time. These functions are used in conjunction with the type fexcept_t and the
21923 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
21925 <li> The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
21926 to select among the IEC 60559 directed rounding modes represented by the rounding
21928 FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
21929 IEC 60559 directed rounding modes.
21930 <li> The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
21931 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
21932 the IEC 60559 status flags and control modes.
21933 <li> The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
21934 recommended in the Appendix to IEC 60559.
21935 <li> The unary minus (-) operator provides the minus (-) operation recommended in the
21936 Appendix to IEC 60559.
21937 <li> The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
21938 recommended in the Appendix to IEC 60559.
21939 <li> The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
21940 Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
21941 <li> The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
21942 function recommended in the Appendix to IEC 60559 (but with a minor change to
21943 better handle signed zeros).
21944 <li> The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
21945 the Appendix to IEC 60559.
21946 <li> The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
21947 Appendix to IEC 60559.
21948 <!--page 459 -->
21949 <li> The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
21950 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
21951 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
21952 function recommended in the Appendix to IEC 60559 (except that the classification
21954 </ul>
21957 <p><!--para 1 -->
21958 If the floating value is infinite or NaN or if the integral part of the floating value exceeds
21959 the range of the integer type, then the ''invalid'' floating-point exception is raised and the
21960 resulting value is unspecified. Whether conversion of non-integer floating values whose
21961 integral part is within the range of the integer type raises the ''inexact'' floating-point
21964 <p><b>Footnotes</b>
21965 <p><small><a name="note310" href="#note310">310)</a> ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
21966 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
21967 cases where it matters, library functions can be used to effect such conversions with or without raising
21968 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
21970 </small>
21973 <p><!--para 1 -->
21974 Conversion from the widest supported IEC 60559 format to decimal with
21975 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note311"><b>311)</b></a></sup>
21976 <p><!--para 2 -->
21977 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
21978 particular, conversion between any supported IEC 60559 format and decimal with
21979 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
21980 rounding mode), which assures that conversion from the widest supported IEC 60559
21981 format to decimal with DECIMAL_DIG digits and back is the identity function.
21982 <p><!--para 3 -->
21983 Functions such as strtod that convert character sequences to floating types honor the
21984 rounding direction. Hence, if the rounding direction might be upward or downward, the
21985 implementation cannot convert a minus-signed sequence by negating the converted
21986 unsigned sequence.
21991 <!--page 460 -->
21993 <p><b>Footnotes</b>
21994 <p><small><a name="note311" href="#note311">311)</a> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
21995 DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
21996 IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
21997 DBL_DIG are 18 and 15, respectively, for these formats.)
21998 </small>
22001 <p><!--para 1 -->
22002 A contracted expression treats infinities, NaNs, signed zeros, subnormals, and the
22003 rounding directions in a manner consistent with the basic arithmetic operations covered
22004 by IEC 60559.
22005 <p><b>Recommended practice</b>
22006 <p><!--para 2 -->
22007 A contracted expression should raise floating-point exceptions in a manner generally
22008 consistent with the basic arithmetic operations. A contracted expression should deliver
22009 the same value as its uncontracted counterpart, else should be correctly rounded (once).
22012 <p><!--para 1 -->
22013 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
22014 point exception status flags and directed-rounding control modes. It includes also
22015 IEC 60559 dynamic rounding precision and trap enablement modes, if the
22018 <p><b>Footnotes</b>
22019 <p><small><a name="note312" href="#note312">312)</a> This specification does not require dynamic rounding precision nor trap enablement modes.
22020 </small>
22023 <p><!--para 1 -->
22024 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
22025 status flags, and that rounding control modes can be set explicitly to affect result values of
22026 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
22027 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
22030 <p><b>Footnotes</b>
22031 <p><small><a name="note313" href="#note313">313)</a> If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
22032 point control modes will be the default ones and the floating-point status flags will not be tested,
22034 </small>
22037 <p><!--para 1 -->
22038 During translation the IEC 60559 default modes are in effect:
22039 <ul>
22040 <li> The rounding direction mode is rounding to nearest.
22041 <li> The rounding precision mode (if supported) is set so that results are not shortened.
22042 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
22043 </ul>
22044 <p><b>Recommended practice</b>
22045 <p><!--para 2 -->
22046 The implementation should produce a diagnostic message for each translation-time
22051 <!--page 461 -->
22052 floating-point exception, other than ''inexact'';<sup><a href="#note314"><b>314)</b></a></sup> the implementation should then
22053 proceed with the translation of the program.
22055 <p><b>Footnotes</b>
22056 <p><small><a name="note314" href="#note314">314)</a> As floating constants are converted to appropriate internal representations at translation time, their
22057 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
22058 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
22059 strtod, provide execution-time conversion of numeric strings.
22060 </small>
22063 <p><!--para 1 -->
22064 At program startup the floating-point environment is initialized as prescribed by
22065 IEC 60559:
22066 <ul>
22067 <li> All floating-point exception status flags are cleared.
22068 <li> The rounding direction mode is rounding to nearest.
22069 <li> The dynamic rounding precision mode (if supported) is set so that results are not
22070 shortened.
22071 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
22072 </ul>
22075 <p><!--para 1 -->
22076 An arithmetic constant expression of floating type, other than one in an initializer for an
22077 object that has static storage duration, is evaluated (as if) during execution; thus, it is
22078 affected by any operative floating-point control modes and raises floating-point
22079 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
22081 <p><!--para 2 -->
22082 EXAMPLE
22083 <pre>
22085 #pragma STDC FENV_ACCESS ON
22086 void f(void)
22087 {
22088 float w[] = { 0.0/0.0 }; // raises an exception
22089 static float x = 0.0/0.0; // does not raise an exception
22090 float y = 0.0/0.0; // raises an exception
22091 double z = 0.0/0.0; // raises an exception
22092 /* ... */
22093 }
22094 </pre>
22095 <p><!--para 3 -->
22096 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
22097 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
22100 <!--page 462 -->
22101 execution time.
22104 <p><b>Footnotes</b>
22105 <p><small><a name="note315" href="#note315">315)</a> Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like 1.0/3.0
22106 are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
22107 1.0/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
22108 efficiency of translation-time evaluation through static initialization, such as
22110 <pre>
22111 const static double one_third = 1.0/3.0;
22112 </pre>
22113 </small>
22116 <p><!--para 1 -->
22117 All computation for automatic initialization is done (as if) at execution time; thus, it is
22118 affected by any operative modes and raises floating-point exceptions as required by
22119 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
22120 for initialization of objects that have static storage duration is done (as if) at translation
22121 time.
22122 <p><!--para 2 -->
22123 EXAMPLE
22124 <pre>
22126 #pragma STDC FENV_ACCESS ON
22127 void f(void)
22128 {
22129 float u[] = { 1.1e75 }; // raises exceptions
22130 static float v = 1.1e75; // does not raise exceptions
22131 float w = 1.1e75; // raises exceptions
22132 double x = 1.1e75; // may raise exceptions
22133 float y = 1.1e75f; // may raise exceptions
22134 long double z = 1.1e75; // does not raise exceptions
22135 /* ... */
22136 }
22137 </pre>
22138 <p><!--para 3 -->
22139 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
22140 done at translation time. The automatic initialization of u and w require an execution-time conversion to
22141 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
22142 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
22143 conversions is not to a narrower format, in which case no floating-point exception is raised.<sup><a href="#note316"><b>316)</b></a></sup> The
22144 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
22145 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
22146 their internal representations occur at translation time in all cases.
22151 <!--page 463 -->
22153 <p><b>Footnotes</b>
22154 <p><small><a name="note316" href="#note316">316)</a> Use of float_t and double_t variables increases the likelihood of translation-time computation.
22155 For example, the automatic initialization
22157 <pre>
22158 double_t x = 1.1e75;
22159 </pre>
22160 could be done at translation time, regardless of the expression evaluation method.
22161 </small>
22164 <p><!--para 1 -->
22165 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
22166 change floating-point status flags and control modes just as indicated by their
22167 specifications (including conformance to IEC 60559). They do not change flags or modes
22168 (so as to be detectable by the user) in any other cases.
22169 <p><!--para 2 -->
22170 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
22171 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
22172 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
22173 before ''inexact''.
22176 <p><!--para 1 -->
22177 This section identifies code transformations that might subvert IEC 60559-specified
22178 behavior, and others that do not.
22181 <p><!--para 1 -->
22182 Floating-point arithmetic operations and external function calls may entail side effects
22183 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
22184 ''on''. The flags and modes in the floating-point environment may be regarded as global
22185 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
22186 flags.
22187 <p><!--para 2 -->
22188 Concern about side effects may inhibit code motion and removal of seemingly useless
22189 code. For example, in
22190 <pre>
22192 #pragma STDC FENV_ACCESS ON
22193 void f(double x)
22194 {
22195 /* ... */
22196 for (i = 0; i < n; i++) x + 1;
22197 /* ... */
22198 }
22199 </pre>
22200 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
22201 body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
22202 course these optimizations are valid if the implementation can rule out the nettlesome
22203 cases.)
22204 <p><!--para 3 -->
22205 This specification does not require support for trap handlers that maintain information
22206 about the order or count of floating-point exceptions. Therefore, between function calls,
22207 floating-point exceptions need not be precise: the actual order and number of occurrences
22208 of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
22209 the preceding loop could be treated as
22210 <!--page 464 -->
22211 <pre>
22212 if (0 < n) x + 1;
22213 </pre>
22216 <p><!--para 1 -->
22217 x / 2 <-> x * 0.5 Although similar transformations involving inexact
22218 <pre>
22219 constants generally do not yield numerically equivalent
22220 expressions, if the constants are exact then such
22221 transformations can be made on IEC 60559 machines
22222 and others that round perfectly.
22223 </pre>
22224 1 * x and x / 1 -> x The expressions 1 * x, x / 1, and x are equivalent
22225 <pre>
22227 </pre>
22228 x / x -> 1.0 The expressions x / x and 1.0 are not equivalent if x
22229 <pre>
22230 can be zero, infinite, or NaN.
22231 </pre>
22232 x - y <-> x + (-y) The expressions x - y, x + (-y), and (-y) + x
22233 <pre>
22234 are equivalent (on IEC 60559 machines, among others).
22235 </pre>
22236 x - y <-> -(y - x) The expressions x - y and -(y - x) are not
22237 <pre>
22238 equivalent because 1 - 1 is +0 but -(1 - 1) is -0 (in the
22240 </pre>
22241 x - x -> 0.0 The expressions x - x and 0.0 are not equivalent if
22242 <pre>
22243 x is a NaN or infinite.
22244 </pre>
22245 0 * x -> 0.0 The expressions 0 * x and 0.0 are not equivalent if
22246 <pre>
22247 x is a NaN, infinite, or -0.
22248 </pre>
22249 x + 0->x The expressions x + 0 and x are not equivalent if x is
22250 <pre>
22251 -0, because (-0) + (+0) yields +0 (in the default
22252 rounding direction), not -0.
22253 </pre>
22254 x - 0->x (+0) - (+0) yields -0 when rounding is downward
22255 <pre>
22256 (toward -(inf)), but +0 otherwise, and (-0) - (+0) always
22257 yields -0; so, if the state of the FENV_ACCESS pragma
22258 is ''off'', promising default rounding, then the
22259 implementation can replace x - 0 by x, even if x
22260 </pre>
22263 <!--page 465 -->
22264 <pre>
22265 might be zero.
22266 </pre>
22267 -x <-> 0 - x The expressions -x and 0 - x are not equivalent if x
22268 <pre>
22269 is +0, because -(+0) yields -0, but 0 - (+0) yields +0
22270 (unless rounding is downward).
22271 </pre>
22273 <p><b>Footnotes</b>
22274 <p><small><a name="note317" href="#note317">317)</a> Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
22275 other transformations that remove arithmetic operators.
22276 </small>
22277 <p><small><a name="note318" href="#note318">318)</a> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
22278 Examples include:
22280 <pre>
22281 1/(1/ (+-) (inf)) is (+-) (inf)
22282 </pre>
22283 and
22285 <pre>
22286 conj(csqrt(z)) is csqrt(conj(z)),
22287 </pre>
22288 for complex z.
22289 </small>
22292 <p><!--para 1 -->
22293 x != x -> false The statement x != x is true if x is a NaN.
22294 x == x -> true The statement x == x is false if x is a NaN.
22295 x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically
22296 <pre>
22297 equal, these expressions are not equivalent because of
22298 side effects when x or y is a NaN and the state of the
22299 FENV_ACCESS pragma is ''on''. This transformation,
22300 which would be desirable if extra code were required to
22301 cause the ''invalid'' floating-point exception for
22302 unordered cases, could be performed provided the state
22303 of the FENV_ACCESS pragma is ''off''.
22304 </pre>
22305 The sense of relational operators shall be maintained. This includes handling unordered
22306 cases as expressed by the source code.
22307 <p><!--para 2 -->
22308 EXAMPLE
22309 <pre>
22310 // calls g and raises ''invalid'' if a and b are unordered
22311 if (a < b)
22312 f();
22313 else
22314 g();
22315 </pre>
22316 is not equivalent to
22317 <pre>
22318 // calls f and raises ''invalid'' if a and b are unordered
22319 if (a >= b)
22320 g();
22321 else
22322 f();
22323 </pre>
22324 nor to
22325 <pre>
22326 // calls f without raising ''invalid'' if a and b are unordered
22327 if (isgreaterequal(a,b))
22328 g();
22329 else
22330 f();
22331 </pre>
22332 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
22333 <!--page 466 -->
22334 <pre>
22335 // calls g without raising ''invalid'' if a and b are unordered
22336 if (isless(a,b))
22337 f();
22338 else
22339 g();
22340 </pre>
22341 but is equivalent to
22342 <pre>
22343 if (!(a < b))
22344 g();
22345 else
22346 f();
22347 </pre>
22351 <p><!--para 1 -->
22352 The implementation shall honor floating-point exceptions raised by execution-time
22353 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.7.4">F.7.4</a>
22354 and <a href="#F.7.5">F.7.5</a>.) An operation on constants that raises no floating-point exception can be
22355 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
22356 further check is required to assure that changing the rounding direction to downward does
22357 not alter the sign of the result,<sup><a href="#note319"><b>319)</b></a></sup> and implementations that support dynamic rounding
22358 precision modes shall assure further that the result of the operation raises no floating-
22359 point exception when converted to the semantic type of the operation.
22361 <p><b>Footnotes</b>
22362 <p><small><a name="note319" href="#note319">319)</a> 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
22363 </small>
22366 <p><!--para 1 -->
22367 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
22368 for IEC 60559 implementations.
22369 <p><!--para 2 -->
22370 The Standard C macro HUGE_VAL and its float and long double analogs,
22371 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
22372 infinities.
22373 <p><!--para 3 -->
22374 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
22375 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
22376 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
22377 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
22378 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
22379 <p><!--para 4 -->
22380 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
22381 nonzero value.
22382 <p><!--para 5 -->
22383 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
22384 subsequent subclauses of this annex.
22385 <p><!--para 6 -->
22386 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
22387 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
22390 <!--page 467 -->
22391 whose magnitude is too large.
22392 <p><!--para 7 -->
22393 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
22395 <p><!--para 8 -->
22396 Whether or when library functions raise the ''inexact'' floating-point exception is
22397 unspecified, unless explicitly specified otherwise.
22398 <p><!--para 9 -->
22399 Whether or when library functions raise an undeserved ''underflow'' floating-point
22400 exception is unspecified.<sup><a href="#note321"><b>321)</b></a></sup> Otherwise, as implied by <a href="#F.7.6">F.7.6</a>, the <a href="#7.12"><math.h></a> functions do
22401 not raise spurious floating-point exceptions (detectable by the user), other than the
22402 ''inexact'' floating-point exception.
22403 <p><!--para 10 -->
22404 Whether the functions honor the rounding direction mode is implementation-defined,
22405 unless explicitly specified otherwise.
22406 <p><!--para 11 -->
22407 Functions with a NaN argument return a NaN result and raise no floating-point exception,
22408 except where stated otherwise.
22409 <p><!--para 12 -->
22410 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
22411 For families of functions, the specifications apply to all of the functions even though only
22412 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
22413 occurs in both an argument and the result, the result has the same sign as the argument.
22414 <p><b>Recommended practice</b>
22415 <p><!--para 13 -->
22416 If a function with one or more NaN arguments returns a NaN result, the result should be
22417 the same as one of the NaN arguments (after possible type conversion), except perhaps
22418 for the sign.
22420 <p><b>Footnotes</b>
22421 <p><small><a name="note320" href="#note320">320)</a> IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
22422 when the floating-point exception is raised.
22423 </small>
22424 <p><small><a name="note321" href="#note321">321)</a> It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
22425 avoiding them would be too costly.
22426 </small>
22431 <p><!--para 1 -->
22432 <ul>
22433 <li> acos(1) returns +0.
22434 <li> acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
22435 | x | > 1.
22440 <!--page 468 -->
22441 </ul>
22444 <p><!--para 1 -->
22445 <ul>
22446 <li> asin((+-)0) returns (+-)0.
22447 <li> asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
22448 | x | > 1.
22449 </ul>
22452 <p><!--para 1 -->
22453 <ul>
22454 <li> atan((+-)0) returns (+-)0.
22455 <li> atan((+-)(inf)) returns (+-)pi /2.
22456 </ul>
22459 <p><!--para 1 -->
22460 <ul>
22462 <li> atan2((+-)0, +0) returns (+-)0.
22463 <li> atan2((+-)0, x) returns (+-)pi for x < 0.
22464 <li> atan2((+-)0, x) returns (+-)0 for x > 0.
22465 <li> atan2(y, (+-)0) returns -pi /2 for y < 0.
22466 <li> atan2(y, (+-)0) returns pi /2 for y > 0.
22467 <li> atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
22468 <li> atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
22469 <li> atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
22470 <li> atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
22471 <li> atan2((+-)(inf), +(inf)) returns (+-)pi /4.
22472 </ul>
22474 <p><b>Footnotes</b>
22475 <p><small><a name="note322" href="#note322">322)</a> atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
22476 the ''divide-by-zero'' floating-point exception.
22477 </small>
22480 <p><!--para 1 -->
22481 <ul>
22482 <li> cos((+-)0) returns 1.
22483 <li> cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
22484 </ul>
22487 <p><!--para 1 -->
22488 <ul>
22489 <li> sin((+-)0) returns (+-)0.
22490 <li> sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
22495 <!--page 469 -->
22496 </ul>
22499 <p><!--para 1 -->
22500 <ul>
22501 <li> tan((+-)0) returns (+-)0.
22502 <li> tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
22503 </ul>
22508 <p><!--para 1 -->
22509 <ul>
22510 <li> acosh(1) returns +0.
22511 <li> acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
22512 <li> acosh(+(inf)) returns +(inf).
22513 </ul>
22516 <p><!--para 1 -->
22517 <ul>
22518 <li> asinh((+-)0) returns (+-)0.
22519 <li> asinh((+-)(inf)) returns (+-)(inf).
22520 </ul>
22523 <p><!--para 1 -->
22524 <ul>
22525 <li> atanh((+-)0) returns (+-)0.
22526 <li> atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
22527 <li> atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
22528 | x | > 1.
22529 </ul>
22532 <p><!--para 1 -->
22533 <ul>
22534 <li> cosh((+-)0) returns 1.
22535 <li> cosh((+-)(inf)) returns +(inf).
22536 </ul>
22539 <p><!--para 1 -->
22540 <ul>
22541 <li> sinh((+-)0) returns (+-)0.
22542 <li> sinh((+-)(inf)) returns (+-)(inf).
22543 </ul>
22546 <p><!--para 1 -->
22547 <ul>
22548 <li> tanh((+-)0) returns (+-)0.
22549 <li> tanh((+-)(inf)) returns (+-)1.
22550 <!--page 470 -->
22551 </ul>
22556 <p><!--para 1 -->
22557 <ul>
22558 <li> exp((+-)0) returns 1.
22559 <li> exp(-(inf)) returns +0.
22560 <li> exp(+(inf)) returns +(inf).
22561 </ul>
22564 <p><!--para 1 -->
22565 <ul>
22566 <li> exp2((+-)0) returns 1.
22567 <li> exp2(-(inf)) returns +0.
22568 <li> exp2(+(inf)) returns +(inf).
22569 </ul>
22572 <p><!--para 1 -->
22573 <ul>
22574 <li> expm1((+-)0) returns (+-)0.
22575 <li> expm1(-(inf)) returns -1.
22576 <li> expm1(+(inf)) returns +(inf).
22577 </ul>
22580 <p><!--para 1 -->
22581 <ul>
22582 <li> frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
22583 <li> frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
22584 pointed to by exp.
22585 <li> frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
22586 (and returns a NaN).
22587 </ul>
22588 <p><!--para 2 -->
22589 frexp raises no floating-point exceptions.
22590 <p><!--para 3 -->
22591 On a binary system, the body of the frexp function might be
22592 <pre>
22593 {
22594 *exp = (value == 0) ? 0 : (int)(1 + logb(value));
22595 return scalbn(value, -(*exp));
22596 }
22597 </pre>
22600 <p><!--para 1 -->
22601 If the correct result is outside the range of the return type, the numeric result is
22602 unspecified and the ''invalid'' floating-point exception is raised.
22603 <!--page 471 -->
22606 <p><!--para 1 -->
22607 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
22610 <p><!--para 1 -->
22611 <ul>
22612 <li> log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
22613 <li> log(1) returns +0.
22614 <li> log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
22615 <li> log(+(inf)) returns +(inf).
22616 </ul>
22619 <p><!--para 1 -->
22620 <ul>
22621 <li> log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
22622 <li> log10(1) returns +0.
22623 <li> log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
22624 <li> log10(+(inf)) returns +(inf).
22625 </ul>
22628 <p><!--para 1 -->
22629 <ul>
22630 <li> log1p((+-)0) returns (+-)0.
22631 <li> log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
22632 <li> log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
22633 x < -1.
22634 <li> log1p(+(inf)) returns +(inf).
22635 </ul>
22638 <p><!--para 1 -->
22639 <ul>
22640 <li> log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
22641 <li> log2(1) returns +0.
22642 <li> log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
22643 <li> log2(+(inf)) returns +(inf).
22644 </ul>
22647 <p><!--para 1 -->
22648 <ul>
22649 <li> logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
22650 <li> logb((+-)(inf)) returns +(inf).
22651 <!--page 472 -->
22652 </ul>
22655 <p><!--para 1 -->
22656 <ul>
22657 <li> modf((+-)x, iptr) returns a result with the same sign as x.
22658 <li> modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
22659 <li> modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
22660 NaN).
22661 </ul>
22662 <p><!--para 2 -->
22663 modf behaves as though implemented by
22664 <pre>
22667 #pragma STDC FENV_ACCESS ON
22668 double modf(double value, double *iptr)
22669 {
22670 int save_round = fegetround();
22671 fesetround(FE_TOWARDZERO);
22672 *iptr = nearbyint(value);
22673 fesetround(save_round);
22674 return copysign(
22675 isinf(value) ? 0.0 :
22676 value - (*iptr), value);
22677 }
22678 </pre>
22681 <p><!--para 1 -->
22682 <ul>
22683 <li> scalbn((+-)0, n) returns (+-)0.
22684 <li> scalbn(x, 0) returns x.
22685 <li> scalbn((+-)(inf), n) returns (+-)(inf).
22686 </ul>
22691 <p><!--para 1 -->
22692 <ul>
22693 <li> cbrt((+-)0) returns (+-)0.
22694 <li> cbrt((+-)(inf)) returns (+-)(inf).
22695 </ul>
22698 <p><!--para 1 -->
22699 <ul>
22700 <li> fabs((+-)0) returns +0.
22701 <li> fabs((+-)(inf)) returns +(inf).
22702 <!--page 473 -->
22703 </ul>
22706 <p><!--para 1 -->
22707 <ul>
22708 <li> hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
22709 <li> hypot(x, (+-)0) is equivalent to fabs(x).
22710 <li> hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
22711 </ul>
22714 <p><!--para 1 -->
22715 <ul>
22716 <li> pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
22717 for y an odd integer < 0.
22718 <li> pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
22719 for y < 0 and not an odd integer.
22720 <li> pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
22721 <li> pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
22722 <li> pow(-1, (+-)(inf)) returns 1.
22723 <li> pow(+1, y) returns 1 for any y, even a NaN.
22724 <li> pow(x, (+-)0) returns 1 for any x, even a NaN.
22725 <li> pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
22726 finite x < 0 and finite non-integer y.
22727 <li> pow(x, -(inf)) returns +(inf) for | x | < 1.
22728 <li> pow(x, -(inf)) returns +0 for | x | > 1.
22729 <li> pow(x, +(inf)) returns +0 for | x | < 1.
22730 <li> pow(x, +(inf)) returns +(inf) for | x | > 1.
22731 <li> pow(-(inf), y) returns -0 for y an odd integer < 0.
22732 <li> pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
22733 <li> pow(-(inf), y) returns -(inf) for y an odd integer > 0.
22734 <li> pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
22735 <li> pow(+(inf), y) returns +0 for y < 0.
22736 <li> pow(+(inf), y) returns +(inf) for y > 0.
22737 <!--page 474 -->
22738 </ul>
22741 <p><!--para 1 -->
22742 sqrt is fully specified as a basic arithmetic operation in IEC 60559.
22747 <p><!--para 1 -->
22748 <ul>
22749 <li> erf((+-)0) returns (+-)0.
22750 <li> erf((+-)(inf)) returns (+-)1.
22751 </ul>
22754 <p><!--para 1 -->
22755 <ul>
22756 <li> erfc(-(inf)) returns 2.
22757 <li> erfc(+(inf)) returns +0.
22758 </ul>
22761 <p><!--para 1 -->
22762 <ul>
22763 <li> lgamma(1) returns +0.
22764 <li> lgamma(2) returns +0.
22765 <li> lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
22766 x a negative integer or zero.
22767 <li> lgamma(-(inf)) returns +(inf).
22768 <li> lgamma(+(inf)) returns +(inf).
22769 </ul>
22772 <p><!--para 1 -->
22773 <ul>
22774 <li> tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
22775 <li> tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
22776 negative integer.
22777 <li> tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
22778 <li> tgamma(+(inf)) returns +(inf).
22779 </ul>
22784 <p><!--para 1 -->
22785 <ul>
22786 <li> ceil((+-)0) returns (+-)0.
22787 <li> ceil((+-)(inf)) returns (+-)(inf).
22788 </ul>
22789 <p><!--para 2 -->
22790 The double version of ceil behaves as though implemented by
22791 <!--page 475 -->
22792 <pre>
22795 #pragma STDC FENV_ACCESS ON
22796 double ceil(double x)
22797 {
22798 double result;
22799 int save_round = fegetround();
22800 fesetround(FE_UPWARD);
22801 result = rint(x); // or nearbyint instead of rint
22802 fesetround(save_round);
22803 return result;
22804 }
22805 </pre>
22808 <p><!--para 1 -->
22809 <ul>
22810 <li> floor((+-)0) returns (+-)0.
22811 <li> floor((+-)(inf)) returns (+-)(inf).
22812 </ul>
22813 <p><!--para 2 -->
22817 <p><!--para 1 -->
22818 The nearbyint functions use IEC 60559 rounding according to the current rounding
22819 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
22820 value from the argument.
22821 <ul>
22822 <li> nearbyint((+-)0) returns (+-)0 (for all rounding directions).
22823 <li> nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
22824 </ul>
22827 <p><!--para 1 -->
22828 The rint functions differ from the nearbyint functions only in that they do raise the
22829 ''inexact'' floating-point exception if the result differs in value from the argument.
22832 <p><!--para 1 -->
22833 The lrint and llrint functions provide floating-to-integer conversion as prescribed
22834 by IEC 60559. They round according to the current rounding direction. If the rounded
22835 value is outside the range of the return type, the numeric result is unspecified and the
22836 ''invalid'' floating-point exception is raised. When they raise no other floating-point
22837 exception and the result differs from the argument, they raise the ''inexact'' floating-point
22838 exception.
22839 <!--page 476 -->
22842 <p><!--para 1 -->
22843 <ul>
22844 <li> round((+-)0) returns (+-)0.
22845 <li> round((+-)(inf)) returns (+-)(inf).
22846 </ul>
22847 <p><!--para 2 -->
22848 The double version of round behaves as though implemented by
22849 <pre>
22852 #pragma STDC FENV_ACCESS ON
22853 double round(double x)
22854 {
22855 double result;
22856 fenv_t save_env;
22857 feholdexcept(&save_env);
22858 result = rint(x);
22859 if (fetestexcept(FE_INEXACT)) {
22860 fesetround(FE_TOWARDZERO);
22861 result = rint(copysign(0.5 + fabs(x), x));
22862 }
22863 feupdateenv(&save_env);
22864 return result;
22865 }
22866 </pre>
22867 The round functions may, but are not required to, raise the ''inexact'' floating-point
22868 exception for non-integer numeric arguments, as this implementation does.
22871 <p><!--para 1 -->
22872 The lround and llround functions differ from the lrint and llrint functions
22873 with the default rounding direction just in that the lround and llround functions
22874 round halfway cases away from zero and need not raise the ''inexact'' floating-point
22875 exception for non-integer arguments that round to within the range of the return type.
22878 <p><!--para 1 -->
22879 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
22880 rounding direction).
22881 <ul>
22882 <li> trunc((+-)0) returns (+-)0.
22883 <li> trunc((+-)(inf)) returns (+-)(inf).
22884 <!--page 477 -->
22885 </ul>
22890 <p><!--para 1 -->
22891 <ul>
22892 <li> fmod((+-)0, y) returns (+-)0 for y not zero.
22893 <li> fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
22894 infinite or y zero.
22895 <li> fmod(x, (+-)(inf)) returns x for x not infinite.
22896 </ul>
22897 <p><!--para 2 -->
22898 The double version of fmod behaves as though implemented by
22899 <pre>
22902 #pragma STDC FENV_ACCESS ON
22903 double fmod(double x, double y)
22904 {
22905 double result;
22906 result = remainder(fabs(x), (y = fabs(y)));
22907 if (signbit(result)) result += y;
22908 return copysign(result, x);
22909 }
22910 </pre>
22913 <p><!--para 1 -->
22914 The remainder functions are fully specified as a basic arithmetic operation in
22915 IEC 60559.
22918 <p><!--para 1 -->
22919 The remquo functions follow the specifications for the remainder functions. They
22920 have no further specifications special to IEC 60559 implementations.
22925 <p><!--para 1 -->
22926 copysign is specified in the Appendix to IEC 60559.
22929 <p><!--para 1 -->
22930 All IEC 60559 implementations support quiet NaNs, in all floating formats.
22931 <!--page 478 -->
22934 <p><!--para 1 -->
22935 <ul>
22936 <li> nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
22937 for x finite and the function value infinite.
22938 <li> nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
22939 exceptions for the function value subnormal or zero and x != y.
22940 </ul>
22943 <p><!--para 1 -->
22944 No additional requirements beyond those on nextafter.
22946 <h4><a name="F.9.9" href="#F.9.9">F.9.9 Maximum, minimum, and positive difference functions</a></h4>
22949 <p><!--para 1 -->
22950 No additional requirements.
22953 <p><!--para 1 -->
22954 If just one argument is a NaN, the fmax functions return the other argument (if both
22955 arguments are NaNs, the functions return a NaN).
22956 <p><!--para 2 -->
22958 <pre>
22959 { return (isgreaterequal(x, y) ||
22960 isnan(y)) ? x : y; }
22961 </pre>
22963 <p><b>Footnotes</b>
22964 <p><small><a name="note323" href="#note323">323)</a> Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
22965 return +0; however, implementation in software might be impractical.
22966 </small>
22969 <p><!--para 1 -->
22975 <p><!--para 1 -->
22976 <ul>
22977 <li> fma(x, y, z) computes xy + z, correctly rounded once.
22978 <li> fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
22979 exception if one of x and y is infinite, the other is zero, and z is a NaN.
22980 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
22981 one of x and y is infinite, the other is zero, and z is not a NaN.
22982 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
22983 times y is an exact infinity and z is also an infinity but with the opposite sign.
22988 <!--page 479 -->
22989 </ul>
22992 <pre>
22993 (informative)
22994 IEC 60559-compatible complex arithmetic
22995 </pre>
22998 <p><!--para 1 -->
22999 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
23000 IEC 60559 real floating-point arithmetic. Although these specifications have been
23001 carefully designed, there is little existing practice to validate the design decisions.
23002 Therefore, these specifications are not normative, but should be viewed more as
23003 recommended practice. An implementation that defines
23004 __STDC_IEC_559_COMPLEX__ should conform to the specifications in this annex.
23007 <p><!--para 1 -->
23008 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
23009 used as a type specifier within declaration specifiers in the same way as _Complex is
23010 (thus, _Imaginary float is a valid type name).
23011 <p><!--para 2 -->
23012 There are three imaginary types, designated as float _Imaginary, double
23013 _Imaginary, and long double _Imaginary. The imaginary types (along with
23014 the real floating and complex types) are floating types.
23015 <p><!--para 3 -->
23016 For imaginary types, the corresponding real type is given by deleting the keyword
23017 _Imaginary from the type name.
23018 <p><!--para 4 -->
23019 Each imaginary type has the same representation and alignment requirements as the
23020 corresponding real type. The value of an object of imaginary type is the value of the real
23021 representation times the imaginary unit.
23022 <p><!--para 5 -->
23023 The imaginary type domain comprises the imaginary types.
23026 <p><!--para 1 -->
23027 A complex or imaginary value with at least one infinite part is regarded as an infinity
23028 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
23029 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
23030 a zero if each of its parts is a zero.
23031 <!--page 480 -->
23036 <p><!--para 1 -->
23037 Conversions among imaginary types follow rules analogous to those for real floating
23038 types.
23041 <p><!--para 1 -->
23042 When a value of imaginary type is converted to a real type other than _Bool,<sup><a href="#note324"><b>324)</b></a></sup> the
23043 result is a positive zero.
23044 <p><!--para 2 -->
23045 When a value of real type is converted to an imaginary type, the result is a positive
23046 imaginary zero.
23048 <p><b>Footnotes</b>
23050 </small>
23053 <p><!--para 1 -->
23054 When a value of imaginary type is converted to a complex type, the real part of the
23055 complex result value is a positive zero and the imaginary part of the complex result value
23056 is determined by the conversion rules for the corresponding real types.
23057 <p><!--para 2 -->
23058 When a value of complex type is converted to an imaginary type, the real part of the
23059 complex value is discarded and the value of the imaginary part is converted according to
23060 the conversion rules for the corresponding real types.
23063 <p><!--para 1 -->
23064 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
23065 operation with an imaginary operand.
23066 <p><!--para 2 -->
23067 For most operand types, the value of the result of a binary operator with an imaginary or
23068 complex operand is completely determined, with reference to real arithmetic, by the usual
23069 mathematical formula. For some operand types, the usual mathematical formula is
23070 problematic because of its treatment of infinities and because of undue overflow or
23071 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
23072 not completely determined.
23077 <!--page 481 -->
23080 <p><b>Semantics</b>
23081 <p><!--para 1 -->
23082 If one operand has real type and the other operand has imaginary type, then the result has
23083 imaginary type. If both operands have imaginary type, then the result has real type. (If
23084 either operand has complex type, then the result has complex type.)
23085 <p><!--para 2 -->
23086 If the operands are not both complex, then the result and floating-point exception
23087 behavior of the * operator is defined by the usual mathematical formula:
23088 <pre>
23089 * u iv u + iv
23090 </pre>
23092 <pre>
23093 x xu i(xv) (xu) + i(xv)
23094 </pre>
23096 <pre>
23097 iy i(yu) -yv (-yv) + i(yu)
23098 </pre>
23100 <pre>
23101 x + iy (xu) + i(yu) (-yv) + i(xv)
23102 </pre>
23103 <p><!--para 3 -->
23104 If the second operand is not complex, then the result and floating-point exception
23105 behavior of the / operator is defined by the usual mathematical formula:
23106 <pre>
23107 / u iv
23108 </pre>
23110 <pre>
23111 x x/u i(-x/v)
23112 </pre>
23114 <pre>
23115 iy i(y/u) y/v
23116 </pre>
23118 <pre>
23119 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)
23120 </pre>
23121 <p><!--para 4 -->
23122 The * and / operators satisfy the following infinity properties for all real, imaginary, and
23124 <ul>
23125 <li> if one operand is an infinity and the other operand is a nonzero finite number or an
23126 infinity, then the result of the * operator is an infinity;
23127 <li> if the first operand is an infinity and the second operand is a finite number, then the
23128 result of the / operator is an infinity;
23129 <li> if the first operand is a finite number and the second operand is an infinity, then the
23130 result of the / operator is a zero;
23135 <!--page 482 -->
23136 <li> if the first operand is a nonzero finite number or an infinity and the second operand is
23137 a zero, then the result of the / operator is an infinity.
23138 </ul>
23139 <p><!--para 5 -->
23140 If both operands of the * operator are complex or if the second operand of the / operator
23141 is complex, the operator raises floating-point exceptions if appropriate for the calculation
23142 of the parts of the result, and may raise spurious floating-point exceptions.
23143 <p><!--para 6 -->
23144 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
23146 <!--page 483 -->
23147 <pre>
23150 /* Multiply z * w ... */
23151 double complex _Cmultd(double complex z, double complex w)
23152 {
23153 #pragma STDC FP_CONTRACT OFF
23154 double a, b, c, d, ac, bd, ad, bc, x, y;
23155 a = creal(z); b = cimag(z);
23156 c = creal(w); d = cimag(w);
23157 ac = a * c; bd = b * d;
23158 ad = a * d; bc = b * c;
23159 x = ac - bd; y = ad + bc;
23160 if (isnan(x) && isnan(y)) {
23161 /* Recover infinities that computed as NaN+iNaN ... */
23162 int recalc = 0;
23163 if ( isinf(a) || isinf(b) ) { // z is infinite
23165 a = copysign(isinf(a) ? 1.0 : 0.0, a);
23166 b = copysign(isinf(b) ? 1.0 : 0.0, b);
23167 if (isnan(c)) c = copysign(0.0, c);
23168 if (isnan(d)) d = copysign(0.0, d);
23169 recalc = 1;
23170 }
23171 if ( isinf(c) || isinf(d) ) { // w is infinite
23173 c = copysign(isinf(c) ? 1.0 : 0.0, c);
23174 d = copysign(isinf(d) ? 1.0 : 0.0, d);
23175 if (isnan(a)) a = copysign(0.0, a);
23176 if (isnan(b)) b = copysign(0.0, b);
23177 recalc = 1;
23178 }
23179 if (!recalc && (isinf(ac) || isinf(bd) ||
23180 isinf(ad) || isinf(bc))) {
23181 /* Recover infinities from overflow by changing NaNs to 0 ... */
23182 if (isnan(a)) a = copysign(0.0, a);
23183 if (isnan(b)) b = copysign(0.0, b);
23184 if (isnan(c)) c = copysign(0.0, c);
23185 if (isnan(d)) d = copysign(0.0, d);
23186 recalc = 1;
23187 }
23188 if (recalc) {
23189 x = INFINITY * ( a * c - b * d );
23190 y = INFINITY * ( a * d + b * c );
23191 }
23192 }
23193 return x + I * y;
23194 }
23195 </pre>
23196 <p><!--para 7 -->
23197 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
23198 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
23200 <p><!--para 8 -->
23201 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
23202 <!--page 484 -->
23203 <pre>
23206 /* Divide z / w ... */
23207 double complex _Cdivd(double complex z, double complex w)
23208 {
23209 #pragma STDC FP_CONTRACT OFF
23210 double a, b, c, d, logbw, denom, x, y;
23211 int ilogbw = 0;
23212 a = creal(z); b = cimag(z);
23213 c = creal(w); d = cimag(w);
23214 logbw = logb(fmax(fabs(c), fabs(d)));
23215 if (isfinite(logbw)) {
23216 ilogbw = (int)logbw;
23217 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
23218 }
23219 denom = c * c + d * d;
23220 x = scalbn((a * c + b * d) / denom, -ilogbw);
23221 y = scalbn((b * c - a * d) / denom, -ilogbw);
23222 /* Recover infinities and zeros that computed as NaN+iNaN; */
23223 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
23224 if (isnan(x) && isnan(y)) {
23225 if ((denom == 0.0) &&
23226 (!isnan(a) || !isnan(b))) {
23227 x = copysign(INFINITY, c) * a;
23228 y = copysign(INFINITY, c) * b;
23229 }
23230 else if ((isinf(a) || isinf(b)) &&
23231 isfinite(c) && isfinite(d)) {
23232 a = copysign(isinf(a) ? 1.0 : 0.0, a);
23233 b = copysign(isinf(b) ? 1.0 : 0.0, b);
23234 x = INFINITY * ( a * c + b * d );
23235 y = INFINITY * ( b * c - a * d );
23236 }
23237 else if (isinf(logbw) &&
23238 isfinite(a) && isfinite(b)) {
23239 c = copysign(isinf(c) ? 1.0 : 0.0, c);
23240 d = copysign(isinf(d) ? 1.0 : 0.0, d);
23241 x = 0.0 * ( a * c + b * d );
23242 y = 0.0 * ( b * c - a * d );
23243 }
23244 }
23245 return x + I * y;
23246 }
23247 </pre>
23248 <p><!--para 9 -->
23249 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
23250 for multiplication. In the spirit of the multiplication example above, this code does not defend against
23251 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
23252 with division, provides better roundoff characteristics.
23255 <p><b>Footnotes</b>
23256 <p><small><a name="note325" href="#note325">325)</a> These properties are already implied for those cases covered in the tables, but are required for all cases
23257 (at least where the state for CX_LIMITED_RANGE is ''off'').
23258 </small>
23261 <p><b>Semantics</b>
23262 <p><!--para 1 -->
23263 If both operands have imaginary type, then the result has imaginary type. (If one operand
23264 has real type and the other operand has imaginary type, or if either operand has complex
23265 type, then the result has complex type.)
23266 <p><!--para 2 -->
23267 In all cases the result and floating-point exception behavior of a + or - operator is defined
23268 by the usual mathematical formula:
23269 <pre>
23270 + or - u iv u + iv
23271 </pre>
23273 <pre>
23274 x x(+-)u x (+-) iv (x (+-) u) (+-) iv
23275 </pre>
23277 <pre>
23278 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)
23279 </pre>
23281 <pre>
23282 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)
23283 </pre>
23286 <p><!--para 1 -->
23287 The macros
23288 <pre>
23289 imaginary
23290 </pre>
23291 and
23292 <pre>
23293 _Imaginary_I
23294 </pre>
23295 are defined, respectively, as _Imaginary and a constant expression of type const
23296 float _Imaginary with the value of the imaginary unit. The macro
23297 <pre>
23298 I
23299 </pre>
23300 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
23301 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
23302 imaginary.
23303 <p><!--para 2 -->
23304 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
23305 particularly suited to IEC 60559 implementations. For families of functions, the
23306 specifications apply to all of the functions even though only the principal function is
23307 <!--page 485 -->
23308 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
23309 and the result, the result has the same sign as the argument.
23310 <p><!--para 3 -->
23311 The functions are continuous onto both sides of their branch cuts, taking into account the
23312 sign of zero. For example, csqrt(-2 (+-) i0) = (+-)i(sqrt)2. ???
23313 <p><!--para 4 -->
23314 Since complex and imaginary values are composed of real values, each function may be
23315 regarded as computing real values from real values. Except as noted, the functions treat
23316 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
23317 manner consistent with the specifications for real functions in F.9.<sup><a href="#note326"><b>326)</b></a></sup>
23318 <p><!--para 5 -->
23319 The functions cimag, conj, cproj, and creal are fully specified for all
23320 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
23321 point exceptions.
23322 <p><!--para 6 -->
23323 Each of the functions cabs and carg is specified by a formula in terms of a real
23325 <pre>
23326 cabs(x + iy) = hypot(x, y)
23327 carg(x + iy) = atan2(y, x)
23328 </pre>
23329 <p><!--para 7 -->
23330 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
23331 a formula in terms of other complex functions (whose special cases are specified below):
23332 <pre>
23333 casin(z) = -i casinh(iz)
23334 catan(z) = -i catanh(iz)
23335 ccos(z) = ccosh(iz)
23336 csin(z) = -i csinh(iz)
23337 ctan(z) = -i ctanh(iz)
23338 </pre>
23339 <p><!--para 8 -->
23340 For the other functions, the following subclauses specify behavior for special cases,
23341 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
23342 families of functions, the specifications apply to all of the functions even though only the
23343 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
23344 specifications for the upper half-plane imply the specifications for the lower half-plane; if
23345 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
23346 specifications for the first quadrant imply the specifications for the other three quadrants.
23347 <p><!--para 9 -->
23348 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
23353 <!--page 486 -->
23355 <p><b>Footnotes</b>
23356 <p><small><a name="note326" href="#note326">326)</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
23357 other part is a NaN.
23358 </small>
23363 <p><!--para 1 -->
23364 <ul>
23365 <li> cacos(conj(z)) = conj(cacos(z)).
23366 <li> cacos((+-)0 + i0) returns pi /2 - i0.
23367 <li> cacos((+-)0 + iNaN) returns pi /2 + iNaN.
23368 <li> cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
23369 <li> cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23370 point exception, for nonzero finite x.
23371 <li> cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
23372 <li> cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
23373 <li> cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
23374 <li> cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
23375 <li> cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
23376 result is unspecified).
23377 <li> cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23378 point exception, for finite y.
23379 <li> cacos(NaN + i (inf)) returns NaN - i (inf).
23380 <li> cacos(NaN + iNaN) returns NaN + iNaN.
23381 </ul>
23386 <p><!--para 1 -->
23387 <ul>
23388 <li> cacosh(conj(z)) = conj(cacosh(z)).
23389 <li> cacosh((+-)0 + i0) returns +0 + ipi /2.
23390 <li> cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
23391 <li> cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
23392 floating-point exception, for finite x.
23393 <li> cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
23394 <li> cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
23395 <li> cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
23396 <li> cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
23397 <li> cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
23398 <!--page 487 -->
23399 <li> cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
23400 floating-point exception, for finite y.
23401 <li> cacosh(NaN + i (inf)) returns +(inf) + iNaN.
23402 <li> cacosh(NaN + iNaN) returns NaN + iNaN.
23403 </ul>
23406 <p><!--para 1 -->
23407 <ul>
23408 <li> casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
23409 <li> casinh(+0 + i0) returns 0 + i0.
23410 <li> casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
23411 <li> casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
23412 floating-point exception, for finite x.
23413 <li> casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
23414 <li> casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
23415 <li> casinh(+(inf) + iNaN) returns +(inf) + iNaN.
23416 <li> casinh(NaN + i0) returns NaN + i0.
23417 <li> casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
23418 floating-point exception, for finite nonzero y.
23419 <li> casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
23420 is unspecified).
23421 <li> casinh(NaN + iNaN) returns NaN + iNaN.
23422 </ul>
23425 <p><!--para 1 -->
23426 <ul>
23427 <li> catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
23428 <li> catanh(+0 + i0) returns +0 + i0.
23429 <li> catanh(+0 + iNaN) returns +0 + iNaN.
23430 <li> catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
23431 exception.
23432 <li> catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
23433 <li> catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
23434 floating-point exception, for nonzero finite x.
23435 <li> catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
23436 <li> catanh(+(inf) + i (inf)) returns +0 + ipi /2.
23437 <li> catanh(+(inf) + iNaN) returns +0 + iNaN.
23438 <!--page 488 -->
23439 <li> catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
23440 floating-point exception, for finite y.
23441 <li> catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
23442 unspecified).
23443 <li> catanh(NaN + iNaN) returns NaN + iNaN.
23444 </ul>
23447 <p><!--para 1 -->
23448 <ul>
23449 <li> ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
23450 <li> ccosh(+0 + i0) returns 1 + i0.
23451 <li> ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
23452 result is unspecified) and raises the ''invalid'' floating-point exception.
23453 <li> ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
23454 result is unspecified).
23455 <li> ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
23456 exception, for finite nonzero x.
23457 <li> ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23458 point exception, for finite nonzero x.
23459 <li> ccosh(+(inf) + i0) returns +(inf) + i0.
23460 <li> ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
23461 <li> ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
23462 unspecified) and raises the ''invalid'' floating-point exception.
23463 <li> ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
23464 <li> ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
23465 result is unspecified).
23466 <li> ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23467 point exception, for all nonzero numbers y.
23468 <li> ccosh(NaN + iNaN) returns NaN + iNaN.
23469 </ul>
23472 <p><!--para 1 -->
23473 <ul>
23474 <li> csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
23475 <li> csinh(+0 + i0) returns +0 + i0.
23476 <li> csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
23477 unspecified) and raises the ''invalid'' floating-point exception.
23478 <li> csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
23479 unspecified).
23480 <!--page 489 -->
23481 <li> csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
23482 exception, for positive finite x.
23483 <li> csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23484 point exception, for finite nonzero x.
23485 <li> csinh(+(inf) + i0) returns +(inf) + i0.
23486 <li> csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
23487 <li> csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
23488 unspecified) and raises the ''invalid'' floating-point exception.
23489 <li> csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
23490 is unspecified).
23491 <li> csinh(NaN + i0) returns NaN + i0.
23492 <li> csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23493 point exception, for all nonzero numbers y.
23494 <li> csinh(NaN + iNaN) returns NaN + iNaN.
23495 </ul>
23498 <p><!--para 1 -->
23499 <ul>
23500 <li> ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
23501 <li> ctanh(+0 + i0) returns +0 + i0.
23502 <li> ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
23503 exception, for finite x.
23504 <li> ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23505 point exception, for finite x.
23506 <li> ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
23507 <li> ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
23508 is unspecified).
23509 <li> ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
23510 result is unspecified).
23511 <li> ctanh(NaN + i0) returns NaN + i0.
23512 <li> ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23513 point exception, for all nonzero numbers y.
23514 <li> ctanh(NaN + iNaN) returns NaN + iNaN.
23515 <!--page 490 -->
23516 </ul>
23521 <p><!--para 1 -->
23522 <ul>
23523 <li> cexp(conj(z)) = conj(cexp(z)).
23524 <li> cexp((+-)0 + i0) returns 1 + i0.
23525 <li> cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
23526 exception, for finite x.
23527 <li> cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23528 point exception, for finite x.
23529 <li> cexp(+(inf) + i0) returns +(inf) + i0.
23530 <li> cexp(-(inf) + iy) returns +0 cis(y), for finite y.
23531 <li> cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
23532 <li> cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
23533 the result are unspecified).
23534 <li> cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
23535 exception (where the sign of the real part of the result is unspecified).
23536 <li> cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
23537 of the result are unspecified).
23538 <li> cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
23539 is unspecified).
23540 <li> cexp(NaN + i0) returns NaN + i0.
23541 <li> cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23542 point exception, for all nonzero numbers y.
23543 <li> cexp(NaN + iNaN) returns NaN + iNaN.
23544 </ul>
23547 <p><!--para 1 -->
23548 <ul>
23549 <li> clog(conj(z)) = conj(clog(z)).
23550 <li> clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
23551 exception.
23552 <li> clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
23553 exception.
23554 <li> clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
23555 <li> clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23556 point exception, for finite x.
23557 <!--page 491 -->
23558 <li> clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
23559 <li> clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
23560 <li> clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
23561 <li> clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
23562 <li> clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
23563 <li> clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23564 point exception, for finite y.
23565 <li> clog(NaN + i (inf)) returns +(inf) + iNaN.
23566 <li> clog(NaN + iNaN) returns NaN + iNaN.
23567 </ul>
23572 <p><!--para 1 -->
23573 The cpow functions raise floating-point exceptions if appropriate for the calculation of
23574 the parts of the result, and may raise spurious exceptions.<sup><a href="#note327"><b>327)</b></a></sup>
23576 <p><b>Footnotes</b>
23577 <p><small><a name="note327" href="#note327">327)</a> This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
23578 implementations that treat special cases more carefully.
23579 </small>
23582 <p><!--para 1 -->
23583 <ul>
23584 <li> csqrt(conj(z)) = conj(csqrt(z)).
23585 <li> csqrt((+-)0 + i0) returns +0 + i0.
23586 <li> csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
23587 <li> csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23588 point exception, for finite x.
23589 <li> csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
23590 <li> csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
23591 <li> csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
23592 result is unspecified).
23593 <li> csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
23594 <li> csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
23595 point exception, for finite y.
23596 <li> csqrt(NaN + iNaN) returns NaN + iNaN.
23601 <!--page 492 -->
23602 </ul>
23605 <p><!--para 1 -->
23606 Type-generic macros that accept complex arguments also accept imaginary arguments. If
23607 an argument is imaginary, the macro expands to an expression whose type is real,
23608 imaginary, or complex, as appropriate for the particular function: if the argument is
23609 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
23610 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
23611 the types of the others are complex.
23612 <p><!--para 2 -->
23613 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
23614 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
23615 functions:
23616 <!--page 493 -->
23617 <pre>
23618 cos(iy) = cosh(y)
23619 sin(iy) = i sinh(y)
23620 tan(iy) = i tanh(y)
23621 cosh(iy) = cos(y)
23622 sinh(iy) = i sin(y)
23623 tanh(iy) = i tan(y)
23624 asin(iy) = i asinh(y)
23625 atan(iy) = i atanh(y)
23626 asinh(iy) = i asin(y)
23627 atanh(iy) = i atan(y)
23628 </pre>
23631 <pre>
23632 (informative)
23633 Language independent arithmetic
23634 </pre>
23637 <p><!--para 1 -->
23638 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
23639 standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
23640 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
23643 <p><!--para 1 -->
23644 The relevant C arithmetic types meet the requirements of LIA-1 types if an
23645 implementation adds notification of exceptional arithmetic operations and meets the 1
23646 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
23649 <p><!--para 1 -->
23650 The LIA-1 data type Boolean is implemented by the C data type bool with values of
23654 <p><!--para 1 -->
23655 The signed C integer types int, long int, long long int, and the corresponding
23656 unsigned types are compatible with LIA-1. If an implementation adds support for the
23657 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
23658 LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
23659 in that overflows or out-of-bounds results silently wrap. An implementation that defines
23660 signed integer types as also being modulo need not detect integer overflow, in which case,
23661 only integer divide-by-zero need be detected.
23662 <p><!--para 2 -->
23663 The parameters for the integer data types can be accessed by the following:
23664 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
23665 <pre>
23666 ULLONG_MAX
23667 </pre>
23668 minint INT_MIN, LONG_MIN, LLONG_MIN
23669 <p><!--para 3 -->
23670 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
23671 is always 0 for the unsigned types, and is not provided for those types.
23672 <!--page 494 -->
23675 <p><!--para 1 -->
23676 The integer operations on integer types are the following:
23677 addI x + y
23678 subI x - y
23679 mulI x * y
23680 divI, divtI x / y
23681 remI, remtI x % y
23682 negI -x
23683 absI abs(x), labs(x), llabs(x)
23684 eqI x == y
23685 neqI x != y
23686 lssI x < y
23687 leqI x <= y
23688 gtrI x > y
23689 geqI x >= y
23690 where x and y are expressions of the same integer type.
23693 <p><!--para 1 -->
23694 The C floating-point types float, double, and long double are compatible with
23695 LIA-1. If an implementation adds support for the LIA-1 exceptional values
23696 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
23698 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
23699 conformant types.
23703 The parameters for a floating point data type can be accessed by the following:
23704 r FLT_RADIX
23705 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
23706 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
23707 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
23709 The derived constants for the floating point types are accessed by the following:
23710 <!--page 495 -->
23711 fmax FLT_MAX, DBL_MAX, LDBL_MAX
23712 fminN FLT_MIN, DBL_MIN, LDBL_MIN
23713 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
23714 rnd_style FLT_ROUNDS
23718 The floating-point operations on floating-point types are the following:
23719 addF x + y
23720 subF x - y
23721 mulF x * y
23722 divF x / y
23723 negF -x
23724 absF fabsf(x), fabs(x), fabsl(x)
23726 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
23727 <pre>
23728 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)
23729 </pre>
23732 eqF x == y
23733 neqF x != y
23734 lssF x < y
23735 leqF x <= y
23736 gtrF x > y
23737 geqF x >= y
23738 where x and y are expressions of the same floating point type, n is of type int, and li
23739 is of type long int.
23743 The C Standard requires all floating types to use the same radix and rounding style, so
23744 that only one identifier for each is provided to map to LIA-1.
23746 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
23747 truncate FLT_ROUNDS == 0
23748 <!--page 496 -->
23749 nearest FLT_ROUNDS == 1
23751 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
23752 in all relevant LIA-1 operations, not just addition as in C.
23756 The LIA-1 type conversions are the following type casts:
23757 cvtI' -> I (int)i, (long int)i, (long long int)i,
23758 <pre>
23759 (unsigned int)i, (unsigned long int)i,
23760 (unsigned long long int)i
23761 </pre>
23762 cvtF -> I (int)x, (long int)x, (long long int)x,
23763 <pre>
23764 (unsigned int)x, (unsigned long int)x,
23765 (unsigned long long int)x
23766 </pre>
23767 cvtI -> F (float)i, (double)i, (long double)i
23768 cvtF' -> F (float)x, (double)x, (long double)x
23770 In the above conversions from floating to integer, the use of (cast)x can be replaced with
23771 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
23772 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
23773 conversion functions, lrint(), llrint(), lround(), and llround(), can be
23774 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
23775 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
23777 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
23780 to 65535.0 which can then be cast to unsigned short int. But, the
23781 remainder() function is not useful for doing silent wrapping to signed integer types,
23782 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
23784 int.
23786 C's conversions (casts) from floating-point to floating-point can meet LIA-1
23787 requirements if an implementation uses round-to-nearest (IEC 60559 default).
23789 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
23790 implementation uses round-to-nearest.
23791 <!--page 497 -->
23795 Notification is the process by which a user or program is informed that an exceptional
23796 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
23797 allows an implementation to cause a notification to occur when any arithmetic operation
23802 LIA-1 requires at least the following two alternatives for handling of notifications:
23803 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
23804 resume.
23806 An implementation need only support a given notification alternative for the entire
23807 program. An implementation may support the ability to switch between notification
23808 alternatives during execution, but is not required to do so. An implementation can
23809 provide separate selection for each kind of notification, but this is not required.
23811 C allows an implementation to provide notification. C's SIGFPE (for traps) and
23812 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
23813 can provide LIA-1 notification.
23815 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
23816 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
23817 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
23818 and-resume behavior with the same constraint.
23824 The following mapping is for floating-point types:
23825 undefined FE_INVALID, FE_DIVBYZERO
23826 floating_overflow FE_OVERFLOW
23827 underflow FE_UNDERFLOW
23829 The floating-point indicator interrogation and manipulation operations are:
23830 set_indicators feraiseexcept(i)
23831 clear_indicators feclearexcept(i)
23832 test_indicators fetestexcept(i)
23833 current_indicators fetestexcept(FE_ALL_EXCEPT)
23834 where i is an expression of type int representing a subset of the LIA-1 indicators.
23836 C allows an implementation to provide the following LIA-1 required behavior: at
23837 program termination if any indicator is set the implementation shall send an unambiguous
23838 <!--page 498 -->
23841 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
23842 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
23843 point indicators.
23847 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
23848 math library functions (which are not permitted to generate any externally visible
23849 exceptional conditions). An implementation can provide an alternative of notification
23850 through termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
23852 LIA-1 does not require that traps be precise.
23854 C does require that SIGFPE be the signal corresponding to arithmetic exceptions, if there
23855 is any signal raised for them.
23857 C supports signal handlers for SIGFPE and allows trapping of arithmetic exceptions.
23858 When arithmetic exceptions do trap, C's signal-handler mechanism allows trap-and-
23859 terminate (either default implementation behavior or user replacement for it) or trap-and-
23860 resume, at the programmer's option.
23861 <!--page 499 -->
23864 <pre>
23865 (informative)
23866 Common warnings
23867 </pre>
23869 An implementation may generate warnings in many situations, none of which are
23870 specified as part of this International Standard. The following are a few of the more
23871 common situations.
23873 <ul>
23874 <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>).
23875 <li> A block with initialization of an object that has automatic storage duration is jumped
23877 <li> An implicit narrowing conversion is encountered, such as the assignment of a long
23878 int or a double to an int, or a pointer to void to a pointer to any type other than
23880 <li> A hexadecimal floating constant cannot be represented exactly in its evaluation format
23882 <li> An integer character constant includes more than one character or a wide character
23885 <li> An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
23886 lvalue in one operand, and a side effect to, or an access to the value of, the identical
23888 <li> A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
23889 <li> The arguments in a function call do not agree in number and type with those of the
23892 <li> A value is given to an object of an enumerated type other than by assignment of an
23893 enumeration constant that is a member of that type, or an enumeration object that has
23894 the same type, or the value of a function that returns the same enumerated type
23899 <li> A constant expression is used as the controlling expression of a selection statement
23901 <!--page 500 -->
23902 <li> An incorrectly formed preprocessing group is encountered while skipping a
23905 <!--page 501 -->
23906 </ul>
23909 <pre>
23910 (informative)
23911 Portability issues
23912 </pre>
23914 This annex collects some information about portability that appears in this International
23915 Standard.
23919 The following are unspecified:
23920 <ul>
23922 <li> The termination status returned to the hosted environment if the return type of main
23924 <li> The behavior of the display device if a printing character is written when the active
23926 <li> The behavior of the display device if a backspace character is written when the active
23928 <li> The behavior of the display device if a horizontal tab character is written when the
23929 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
23930 <li> The behavior of the display device if a vertical tab character is written when the active
23931 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
23932 <li> How an extended source character that does not correspond to a universal character
23933 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
23935 <li> The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
23936 <li> The value of a union member other than the last one stored into (<a href="#6.2.6.1">6.2.6.1</a>).
23937 <li> The representation used when storing a value in an object that has more than one
23939 <li> The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
23940 <li> Whether certain operators can generate negative zeros and whether a negative zero
23943 <li> The order in which subexpressions are evaluated and the order in which side effects
23944 take place, except as specified for the function-call (), &&, ||, ?:, and comma
23946 <!--page 502 -->
23947 <li> The order in which the function designator, arguments, and subexpressions within the
23949 <li> The order of side effects among compound literal initialization list expressions
23951 <li> The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
23952 <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>).
23953 <li> Whether a call to an inline function uses the inline definition or the external definition
23955 <li> Whether or not a size expression is evaluated when it is part of the operand of a
23956 sizeof operator and changing the value of the size expression would not affect the
23958 <li> The order in which any side effects occur among the initialization list expressions in
23961 <li> When a fully expanded macro replacement list contains a function-like macro name
23962 as its last preprocessing token and the next preprocessing token from the source file is
23963 a (, and the fully expanded replacement of that macro ends with the name of the first
23964 macro and the next preprocessing token from the source file is again a (, whether that
23966 <li> The order in which # and ## operations are evaluated during macro substitution
23968 <li> Whether errno is a macro or an identifier with external linkage (<a href="#7.5">7.5</a>).
23969 <li> The state of the floating-point status flags when execution passes from a part of the
23970 program translated with FENV_ACCESS ''off'' to a part translated with
23972 <li> The order in which feraiseexcept raises floating-point exceptions, except as
23974 <li> Whether math_errhandling is a macro or an identifier with external linkage
23976 <li> The results of the frexp functions when the specified value is not a floating-point
23978 <li> The numeric result of the ilogb functions when the correct value is outside the
23980 <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.9.6.5">F.9.6.5</a>).
23981 <!--page 503 -->
23982 <li> The value stored by the remquo functions in the object pointed to by quo when y is
23984 <li> Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
23985 <li> Whether va_copy and va_end are macros or identifiers with external linkage
23987 <li> The hexadecimal digit before the decimal point when a non-normalized floating-point
23988 number is printed with an a or A conversion specifier (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23989 <li> The value of the file position indicator after a successful call to the ungetc function
23990 for a text stream, or the ungetwc function for any stream, until all pushed-back
23991 characters are read or discarded (<a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.3.10">7.24.3.10</a>).
23992 <li> The details of the value stored by the fgetpos function (<a href="#7.19.9.1">7.19.9.1</a>).
23993 <li> The details of the value returned by the ftell function for a text stream (<a href="#7.19.9.4">7.19.9.4</a>).
23994 <li> Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
23995 functions convert a minus-signed sequence to a negative number directly or by
23996 negating the value resulting from converting the corresponding unsigned sequence
23998 <li> The order and contiguity of storage allocated by successive calls to the calloc,
24000 <li> The amount of storage allocated by a successful call to the calloc, malloc, or
24002 <li> Which of two elements that compare as equal is matched by the bsearch function
24004 <li> The order of two elements that compare as equal in an array sorted by the qsort
24006 <li> The encoding of the calendar time returned by the time function (<a href="#7.23.2.4">7.23.2.4</a>).
24007 <li> The characters stored by the strftime or wcsftime function if any of the time
24008 values being converted is outside the normal range (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
24009 <li> The conversion state after an encoding error occurs (<a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>,
24011 <li> The resulting value when the ''invalid'' floating-point exception is raised during
24015 <!--page 504 -->
24016 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
24018 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
24020 <li> The exponent value stored by frexp for a NaN or infinity (<a href="#F.9.3.4">F.9.3.4</a>).
24021 <li> The numeric result returned by the lrint, llrint, lround, and llround
24022 functions if the rounded value is outside the range of the return type (<a href="#F.9.6.5">F.9.6.5</a>, <a href="#F.9.6.7">F.9.6.7</a>).
24023 <li> The sign of one part of the complex result of several math functions for certain
24024 exceptional values 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>,
24025 <a href="#G.6.2.3">G.6.2.3</a>, <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>).
24026 </ul>
24030 The behavior is undefined in the following circumstances:
24031 <ul>
24032 <li> A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
24033 (clause 4).
24034 <li> A nonempty source file does not end in a new-line character which is not immediately
24035 preceded by a backslash character or ends in a partial preprocessing token or
24037 <li> Token concatenation produces a character sequence matching the syntax of a
24039 <li> A program in a hosted environment does not define a function named main using one
24041 <li> A character not in the basic source character set is encountered in a source file, except
24042 in an identifier, a character constant, a string literal, a header name, a comment, or a
24044 <li> An identifier, comment, string literal, character constant, or header name contains an
24045 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>).
24046 <li> The same identifier has both internal and external linkage in the same translation unit
24049 <li> The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
24050 <li> The value of an object with automatic storage duration is used while it is
24051 indeterminate (<a href="#6.2.4">6.2.4</a>, <a href="#6.7.8">6.7.8</a>, <a href="#6.8">6.8</a>).
24052 <li> A trap representation is read by an lvalue expression that does not have character type
24054 <!--page 505 -->
24055 <li> A trap representation is produced by a side effect that modifies any part of the object
24056 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
24057 <li> The arguments to certain operators are such that could produce a negative zero result,
24059 <li> Two declarations of the same object or function specify types that are not compatible
24061 <li> Conversion to or from an integer type produces a value outside the range that can be
24063 <li> Demotion of one real floating type to another produces a value outside the range that
24066 <li> A non-array lvalue with an incomplete type is used in a context that requires the value
24068 <li> An lvalue having array type is converted to a pointer to the initial element of the
24070 <li> An attempt is made to use the value of a void expression, or an implicit or explicit
24072 <li> Conversion of a pointer to an integer type produces a value outside the range that can
24074 <li> Conversion between two pointer types produces a result that is incorrectly aligned
24076 <li> A pointer is used to call a function whose type is not compatible with the pointed-to
24080 <li> A reserved keyword token is used in translation phase 7 or 8 for some purpose other
24082 <li> A universal character name in an identifier does not designate a character whose
24084 <li> The initial character of an identifier is a universal character name designating a digit
24086 <li> Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
24088 <!--page 506 -->
24091 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
24093 <li> Between two sequence points, an object is modified more than once, or is modified
24094 and the prior value is read other than to determine the value to be stored (<a href="#6.5">6.5</a>).
24095 <li> An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
24096 <li> An object has its stored value accessed other than by an lvalue of an allowable type
24098 <li> An attempt is made to modify the result of a function call, a conditional operator, an
24099 assignment operator, or a comma operator, or to access it after the next sequence
24100 point (<a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.15">6.5.15</a>, <a href="#6.5.16">6.5.16</a>, <a href="#6.5.17">6.5.17</a>).
24101 <li> For a call to a function without a function prototype in scope, the number of
24103 <li> For call to a function without a function prototype in scope where the function is
24104 defined with a function prototype, either the prototype ends with an ellipsis or the
24105 types of the arguments after promotion are not compatible with the types of the
24107 <li> For a call to a function without a function prototype in scope where the function is not
24108 defined with a function prototype, the types of the arguments after promotion are not
24109 compatible with those of the parameters after promotion (with certain exceptions)
24111 <li> A function is defined with a type that is not compatible with the type (of the
24112 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
24113 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
24114 <li> A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
24115 <li> The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
24116 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
24117 integer type produces a result that does not point into, or just beyond, the same array
24119 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
24120 integer type produces a result that points just beyond the array object and is used as
24122 <li> Pointers that do not point into, or just beyond, the same array object are subtracted
24124 <!--page 507 -->
24125 <li> An array subscript is out of range, even if an object is apparently accessible with the
24126 given subscript (as in the lvalue expression a[1][7] given the declaration int
24128 <li> The result of subtracting two pointers is not representable in an object of type
24130 <li> An expression is shifted by a negative number or by an amount greater than or equal
24132 <li> An expression having signed promoted type is left-shifted and either the value of the
24133 expression is negative or the result of shifting would be not be representable in the
24135 <li> Pointers that do not point to the same aggregate or union (nor just beyond the same
24137 <li> An object is assigned to an inexactly overlapping object or to an exactly overlapping
24139 <li> An expression that is required to be an integer constant expression does not have an
24140 integer type; has operands that are not integer constants, enumeration constants,
24141 character constants, sizeof expressions whose results are integer constants, or
24142 immediately-cast floating constants; or contains casts (outside operands to sizeof
24143 operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
24144 <li> A constant expression in an initializer is not, or does not evaluate to, one of the
24145 following: an arithmetic constant expression, a null pointer constant, an address
24146 constant, or an address constant for an object type plus or minus an integer constant
24148 <li> An arithmetic constant expression does not have arithmetic type; has operands that
24149 are not integer constants, floating constants, enumeration constants, character
24150 constants, or sizeof expressions; or contains casts (outside operands to sizeof
24151 operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
24152 <li> The value of an object is accessed by an array-subscript [], member-access . or ->,
24153 address &, or indirection * operator or a pointer cast in creating an address constant
24155 <li> An identifier for an object is declared with no linkage and the type of the object is
24156 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
24157 <li> A function is declared at block scope with an explicit storage-class specifier other
24159 <li> A structure or union is defined as containing no named members (<a href="#6.7.2.1">6.7.2.1</a>).
24160 <!--page 508 -->
24161 <li> An attempt is made to access, or generate a pointer to just past, a flexible array
24162 member of a structure when the referenced object provides no elements for that array
24164 <li> When the complete type is needed, an incomplete structure or union type is not
24165 completed in the same scope by another declaration of the tag that defines the content
24167 <li> An attempt is made to modify an object defined with a const-qualified type through
24169 <li> An attempt is made to refer to an object defined with a volatile-qualified type through
24171 <li> The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>).
24172 <li> Two qualified types that are required to be compatible do not have the identically
24174 <li> An object which has been modified is accessed through a restrict-qualified pointer to
24175 a const-qualified type, or through a restrict-qualified pointer and another pointer that
24177 <li> A restrict-qualified pointer is assigned a value based on another restricted pointer
24178 whose associated block neither began execution before the block associated with this
24180 <li> A function with external linkage is declared with an inline function specifier, but is
24182 <li> Two pointer types that are required to be compatible are not identically qualified, or
24184 <li> The size expression in an array declaration is not a constant expression and evaluates
24186 <li> In a context requiring two array types to be compatible, they do not have compatible
24187 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.5.2">6.7.5.2</a>).
24188 <li> A declaration of an array parameter includes the keyword static within the [ and
24189 ] and the corresponding argument does not provide access to the first element of an
24191 <li> A storage-class specifier or type qualifier modifies the keyword void as a function
24193 <li> In a context requiring two function types to be compatible, they do not have
24194 compatible return types, or their parameters disagree in use of the ellipsis terminator
24195 or the number and type of parameters (after default argument promotion, when there
24196 is no parameter type list or when one type is specified by a function definition with an
24197 <!--page 509 -->
24199 <li> The value of an unnamed member of a structure or union is used (<a href="#6.7.8">6.7.8</a>).
24200 <li> The initializer for a scalar is neither a single expression nor a single expression
24202 <li> The initializer for a structure or union object that has automatic storage duration is
24203 neither an initializer list nor a single expression that has compatible structure or union
24205 <li> The initializer for an aggregate or union, other than an array initialized by a string
24206 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.8">6.7.8</a>).
24207 <li> An identifier with external linkage is used, but in the program there does not exist
24208 exactly one external definition for the identifier, or the identifier is not used and there
24210 <li> A function definition includes an identifier list, but the types of the parameters are not
24212 <li> An adjusted parameter type in a function definition is not an object type (<a href="#6.9.1">6.9.1</a>).
24213 <li> A function that accepts a variable number of arguments is defined without a
24215 <li> The } that terminates a function is reached, and the value of the function call is used
24217 <li> An identifier for an object with internal linkage and an incomplete type is declared
24219 <li> The token defined is generated during the expansion of a #if or #elif
24220 preprocessing directive, or the use of the defined unary operator does not match
24222 <li> The #include preprocessing directive that results after expansion does not match
24224 <li> The character sequence in an #include preprocessing directive does not start with a
24226 <li> There are sequences of preprocessing tokens within the list of macro arguments that
24228 <li> The result of the preprocessing operator # is not a valid character string literal
24230 <li> The result of the preprocessing operator ## is not a valid preprocessing token
24232 <!--page 510 -->
24233 <li> The #line preprocessing directive that results after expansion does not match one of
24234 the two well-defined forms, or its digit sequence specifies zero or a number greater
24236 <li> A non-STDC #pragma preprocessing directive that is documented as causing
24237 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
24238 <li> A #pragma STDC preprocessing directive does not match one of the well-defined
24240 <li> The name of a predefined macro, or the identifier defined, is the subject of a
24242 <li> An attempt is made to copy an object to an overlapping object by use of a library
24243 function, other than as explicitly allowed (e.g., memmove) (clause 7).
24244 <li> A file with the same name as one of the standard headers, not provided as part of the
24245 implementation, is placed in any of the standard places that are searched for included
24247 <li> A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
24248 <li> A function, object, type, or macro that is specified as being declared or defined by
24249 some standard header is used before any header that declares or defines it is included
24251 <li> A standard header is included while a macro is defined with the same name as a
24253 <li> The program attempts to declare a library function itself, rather than via a standard
24255 <li> The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
24257 <li> The program removes the definition of a macro whose name begins with an
24259 <li> An argument to a library function has an invalid value or a type not expected by a
24261 <li> The pointer passed to a library function array parameter does not have a value such
24263 <li> The macro definition of assert is suppressed in order to access an actual function
24266 <li> The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
24267 any context other than outside all external declarations or preceding all explicit
24268 <!--page 511 -->
24269 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>).
24270 <li> The value of an argument to a character handling function is neither equal to the value
24272 <li> A macro definition of errno is suppressed in order to access an actual object, or the
24274 <li> Part of the program tests floating-point status flags, sets floating-point control modes,
24275 or runs under non-default mode settings, but was translated with the state for the
24277 <li> The exception-mask argument for one of the functions that provide access to the
24278 floating-point status flags has a nonzero value not obtained by bitwise OR of the
24280 <li> The fesetexceptflag function is used to set floating-point status flags that were
24281 not specified in the call to the fegetexceptflag function that provided the value
24283 <li> The argument to fesetenv or feupdateenv is neither an object set by a call to
24284 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>).
24285 <li> The value of the result of an integer arithmetic or conversion function cannot be
24286 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="#7.20.6.1">7.20.6.1</a>, <a href="#7.20.6.2">7.20.6.2</a>, <a href="#7.20.1">7.20.1</a>).
24287 <li> The program modifies the string pointed to by the value returned by the setlocale
24289 <li> The program modifies the structure pointed to by the value returned by the
24291 <li> A macro definition of math_errhandling is suppressed or the program defines
24293 <li> An argument to a floating-point classification or comparison macro is not of real
24295 <li> A macro definition of setjmp is suppressed in order to access an actual function, or
24297 <li> An invocation of the setjmp macro occurs other than in an allowed context
24299 <li> The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
24300 <li> After a longjmp, there is an attempt to access the value of an object of automatic
24301 storage class with non-volatile-qualified type, local to the function containing the
24302 invocation of the corresponding setjmp macro, that was changed between the
24304 <!--page 512 -->
24305 <li> The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
24306 <li> A signal handler returns when the signal corresponded to a computational exception
24308 <li> A signal occurs as the result of calling the abort or raise function, and the signal
24310 <li> A signal occurs other than as the result of calling the abort or raise function, and
24311 the signal handler refers to an object with static storage duration other than by
24312 assigning a value to an object declared as volatile sig_atomic_t, or calls any
24313 function in the standard library other than the abort function, the _Exit function,
24315 <li> The value of errno is referred to after a signal occurred other than as the result of
24316 calling the abort or raise function and the corresponding signal handler obtained
24318 <li> A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
24319 <li> A function with a variable number of arguments attempts to access its varying
24320 arguments other than through a properly declared and initialized va_list object, or
24321 before the va_start macro is invoked (<a href="#7.15">7.15</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.4">7.15.1.4</a>).
24322 <li> The macro va_arg is invoked using the parameter ap that was passed to a function
24324 <li> A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
24325 order to access an actual function, or the program defines an external identifier with
24327 <li> The va_start or va_copy macro is invoked without a corresponding invocation
24328 of the va_end macro in the same function, or vice versa (<a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.3">7.15.1.3</a>,
24330 <li> The type parameter to the va_arg macro is not such that a pointer to an object of
24332 <li> The va_arg macro is invoked when there is no actual next argument, or with a
24333 specified type that is not compatible with the promoted type of the actual next
24335 <li> The va_copy or va_start macro is called to initialize a va_list that was
24336 previously initialized by either macro without an intervening invocation of the
24337 va_end macro for the same va_list (<a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.4">7.15.1.4</a>).
24338 <li> The parameter parmN of a va_start macro is declared with the register
24339 storage class, with a function or array type, or with a type that is not compatible with
24340 the type that results after application of the default argument promotions (<a href="#7.15.1.4">7.15.1.4</a>).
24341 <!--page 513 -->
24342 <li> The member designator parameter of an offsetof macro is an invalid right
24343 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.17">7.17</a>).
24344 <li> The argument in an instance of one of the integer-constant macros is not a decimal,
24345 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
24347 <li> A byte input/output function is applied to a wide-oriented stream, or a wide character
24349 <li> Use is made of any portion of a file beyond the most recent wide character written to
24351 <li> The value of a pointer to a FILE object is used after the associated file is closed
24353 <li> The stream for the fflush function points to an input stream or to an update stream
24355 <li> The string pointed to by the mode argument in a call to the fopen function does not
24357 <li> An output operation on an update stream is followed by an input operation without an
24358 intervening call to the fflush function or a file positioning function, or an input
24359 operation on an update stream is followed by an output operation with an intervening
24361 <li> An attempt is made to use the contents of the array that was supplied in a call to the
24363 <li> There are insufficient arguments for the format in a call to one of the formatted
24364 input/output functions, or an argument does not have an appropriate type (<a href="#7.19.6.1">7.19.6.1</a>,
24365 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
24366 <li> The format in a call to one of the formatted input/output functions or to the
24367 strftime or wcsftime function is not a valid multibyte character sequence that
24368 begins and ends in its initial shift state (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>,
24370 <li> In a call to one of the formatted output functions, a precision appears with a
24371 conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
24372 <li> A conversion specification for a formatted output function uses an asterisk to denote
24373 an argument-supplied field width or precision, but the corresponding argument is not
24375 <li> A conversion specification for a formatted output function uses a # or 0 flag with a
24376 conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
24377 <!--page 514 -->
24378 <li> A conversion specification for one of the formatted input/output functions uses a
24379 length modifier with a conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>,
24380 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
24381 <li> An s conversion specifier is encountered by one of the formatted output functions,
24382 and the argument is missing the null terminator (unless a precision is specified that
24383 does not require null termination) (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
24384 <li> An n conversion specification for one of the formatted input/output functions includes
24385 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.19.6.1">7.19.6.1</a>,
24386 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
24387 <li> A % conversion specifier is encountered by one of the formatted input/output
24388 functions, but the complete conversion specification is not exactly %% (<a href="#7.19.6.1">7.19.6.1</a>,
24389 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
24390 <li> An invalid conversion specification is found in the format for one of the formatted
24391 input/output functions, or the strftime or wcsftime function (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>,
24392 <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.5.1">7.24.5.1</a>).
24393 <li> The number of characters transmitted by a formatted output function is greater than
24394 INT_MAX (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.10">7.19.6.10</a>).
24395 <li> The result of a conversion by one of the formatted input functions cannot be
24396 represented in the corresponding object, or the receiving object does not have an
24398 <li> A c, s, or [ conversion specifier is encountered by one of the formatted input
24399 functions, and the array pointed to by the corresponding argument is not large enough
24400 to accept the input sequence (and a null terminator if the conversion specifier is s or
24402 <li> A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
24403 formatted input functions, but the input is not a valid multibyte character sequence
24404 that begins in the initial shift state (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
24405 <li> The input item for a %p conversion by one of the formatted input functions is not a
24406 value converted earlier during the same program execution (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
24407 <li> The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
24408 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
24409 vwscanf function is called with an improperly initialized va_list argument, or
24410 the argument is used (other than in an invocation of va_end) after the function
24411 returns (<a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>, <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
24412 <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>).
24413 <li> The contents of the array supplied in a call to the fgets, gets, or fgetws function
24414 are used after a read error occurred (<a href="#7.19.7.2">7.19.7.2</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.24.3.2">7.24.3.2</a>).
24415 <!--page 515 -->
24416 <li> The file position indicator for a binary stream is used after a call to the ungetc
24418 <li> The file position indicator for a stream is used after an error occurred during a call to
24419 the fread or fwrite function (<a href="#7.19.8.1">7.19.8.1</a>, <a href="#7.19.8.2">7.19.8.2</a>).
24420 <li> A partial element read by a call to the fread function is used (<a href="#7.19.8.1">7.19.8.1</a>).
24421 <li> The fseek function is called for a text stream with a nonzero offset and either the
24422 offset was not returned by a previous successful call to the ftell function on a
24423 stream associated with the same file or whence is not SEEK_SET (<a href="#7.19.9.2">7.19.9.2</a>).
24424 <li> The fsetpos function is called to set a position that was not returned by a previous
24425 successful call to the fgetpos function on a stream associated with the same file
24427 <li> A non-null pointer returned by a call to the calloc, malloc, or realloc function
24429 <li> The value of a pointer that refers to space deallocated by a call to the free or
24431 <li> The pointer argument to the free or realloc function does not match a pointer
24432 earlier returned by calloc, malloc, or realloc, or the space has been
24433 deallocated by a call to free or realloc (<a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a>).
24434 <li> The value of the object allocated by the malloc function is used (<a href="#7.20.3.3">7.20.3.3</a>).
24435 <li> The value of any bytes in a new object allocated by the realloc function beyond
24437 <li> The program executes more than one call to the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
24438 <li> During the call to a function registered with the atexit function, a call is made to
24439 the longjmp function that would terminate the call to the registered function
24441 <li> The string set up by the getenv or strerror function is modified by the program
24443 <li> A command is executed through the system function in a way that is documented as
24444 causing termination or some other form of undefined behavior (<a href="#7.20.4.6">7.20.4.6</a>).
24445 <li> A searching or sorting utility function is called with an invalid pointer argument, even
24447 <li> The comparison function called by a searching or sorting utility function alters the
24448 contents of the array being searched or sorted, or returns ordering values
24450 <!--page 516 -->
24451 <li> The array being searched by the bsearch function does not have its elements in
24453 <li> The current conversion state is used by a multibyte/wide character conversion
24455 <li> A string or wide string utility function is instructed to access an array beyond the end
24457 <li> A string or wide string utility function is called with an invalid pointer argument, even
24459 <li> The contents of the destination array are used after a call to the strxfrm,
24460 strftime, wcsxfrm, or wcsftime function in which the specified length was
24461 too small to hold the entire null-terminated result (<a href="#7.21.4.5">7.21.4.5</a>, <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a>,
24463 <li> The first argument in the very first call to the strtok or wcstok is a null pointer
24465 <li> The type of an argument to a type-generic macro is not compatible with the type of
24467 <li> A complex argument is supplied for a generic parameter of a type-generic macro that
24469 <li> The argument corresponding to an s specifier without an l qualifier in a call to the
24470 fwprintf function does not point to a valid multibyte character sequence that
24472 <li> In a call to the wcstok function, the object pointed to by ptr does not have the
24473 value stored by the previous call for the same wide string (<a href="#7.24.4.5.7">7.24.4.5.7</a>).
24475 <li> The value of an argument of type wint_t to a wide character classification or case
24476 mapping function is neither equal to the value of WEOF nor representable as a
24478 <li> The iswctype function is called using a different LC_CTYPE category from the
24479 one in effect for the call to the wctype function that returned the description
24481 <li> The towctrans function is called using a different LC_CTYPE category from the
24482 one in effect for the call to the wctrans function that returned the description
24484 <!--page 517 -->
24485 </ul>
24488 <p><!--para 1 -->
24489 A conforming implementation is required to document its choice of behavior in each of
24490 the areas listed in this subclause. The following are implementation-defined:
24493 <p><!--para 1 -->
24494 <ul>
24495 <li> How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
24496 <li> Whether each nonempty sequence of white-space characters other than new-line is
24497 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
24498 </ul>
24501 <p><!--para 1 -->
24502 <ul>
24503 <li> The mapping between physical source file multibyte characters and the source
24505 <li> The name and type of the function called at program startup in a freestanding
24507 <li> The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
24508 <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>).
24509 <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>).
24511 <li> The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
24512 <li> Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
24514 <li> Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
24516 <li> The set of environment names and the method for altering the environment list used
24518 <li> The manner of execution of the string by the system function (<a href="#7.20.4.6">7.20.4.6</a>).
24519 </ul>
24522 <p><!--para 1 -->
24523 <ul>
24524 <li> Which additional multibyte characters may appear in identifiers and their
24526 <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>).
24527 <!--page 518 -->
24528 </ul>
24531 <p><!--para 1 -->
24532 <ul>
24535 <li> The unique value of the member of the execution character set produced for each of
24537 <li> The value of a char object into which has been stored any character other than a
24539 <li> Which of signed char or unsigned char has the same range, representation,
24541 <li> The mapping of members of the source character set (in character constants and string
24542 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>).
24543 <li> The value of an integer character constant containing more than one character or
24544 containing a character or escape sequence that does not map to a single-byte
24546 <li> The value of a wide character constant containing more than one multibyte character,
24547 or containing a multibyte character or escape sequence not represented in the
24549 <li> The current locale used to convert a wide character constant consisting of a single
24550 multibyte character that maps to a member of the extended execution character set
24552 <li> The current locale used to convert a wide string literal into corresponding wide
24554 <li> The value of a string literal containing a multibyte character or escape sequence not
24556 </ul>
24559 <p><!--para 1 -->
24560 <ul>
24561 <li> Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
24562 <li> Whether signed integer types are represented using sign and magnitude, two's
24563 complement, or ones' complement, and whether the extraordinary value is a trap
24565 <li> The rank of any extended integer type relative to another extended integer type with
24567 <li> The result of, or the signal raised by, converting an integer to a signed integer type
24568 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
24569 <!--page 519 -->
24571 </ul>
24574 <p><!--para 1 -->
24575 <ul>
24576 <li> The accuracy of the floating-point operations and of the library functions in
24577 <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>).
24578 <li> The accuracy of the conversions between floating-point internal representations and
24579 string representations performed by the library functions in <a href="#7.19"><stdio.h></a>,
24580 <a href="#7.20"><stdlib.h></a>, and <a href="#7.24"><wchar.h></a> (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
24581 <li> The rounding behaviors characterized by non-standard values of FLT_ROUNDS
24583 <li> The evaluation methods characterized by non-standard negative values of
24585 <li> The direction of rounding when an integer is converted to a floating-point number that
24587 <li> The direction of rounding when a floating-point number is converted to a narrower
24589 <li> How the nearest representable value or the larger or smaller representable value
24590 immediately adjacent to the nearest representable value is chosen for certain floating
24592 <li> Whether and how floating expressions are contracted when not disallowed by the
24595 <li> Additional floating-point exceptions, rounding modes, environments, and
24598 </ul>
24601 <p><!--para 1 -->
24602 <ul>
24603 <li> The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
24604 <li> The size of the result of subtracting two pointers to elements of the same array
24606 <!--page 520 -->
24607 </ul>
24610 <p><!--para 1 -->
24611 <ul>
24612 <li> The extent to which suggestions made by using the register storage-class
24614 <li> The extent to which suggestions made by using the inline function specifier are
24616 </ul>
24618 <h4><a name="J.3.9" href="#J.3.9">J.3.9 Structures, unions, enumerations, and bit-fields</a></h4>
24619 <p><!--para 1 -->
24620 <ul>
24621 <li> Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
24623 <li> Allowable bit-field types other than _Bool, signed int, and unsigned int
24625 <li> Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
24627 <li> The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
24628 no problem unless binary data written by one implementation is read by another.
24630 </ul>
24633 <p><!--para 1 -->
24634 <ul>
24635 <li> What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
24636 </ul>
24639 <p><!--para 1 -->
24640 <ul>
24641 <li> The locations within #pragma directives where header name preprocessing tokens
24643 <li> How sequences in both forms of header names are mapped to headers or external
24645 <li> Whether the value of a character constant in a constant expression that controls
24646 conditional inclusion matches the value of the same character constant in the
24648 <li> Whether the value of a single-character character constant in a constant expression
24650 <li> The places that are searched for an included < > delimited header, and how the places
24654 <li> The method by which preprocessing tokens (possibly resulting from macro
24655 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
24656 <!--page 521 -->
24658 <li> Whether the # operator inserts a \ character before the \ character that begins a
24659 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
24660 <li> The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
24661 <li> The definitions for __DATE__ and __TIME__ when respectively, the date and
24663 </ul>
24666 <p><!--para 1 -->
24667 <ul>
24668 <li> Any library facilities available to a freestanding program, other than the minimal set
24670 <li> The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
24671 <li> The representation of the floating-point status flags stored by the
24673 <li> Whether the feraiseexcept function raises the ''inexact'' floating-point
24674 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
24678 <li> The types defined for float_t and double_t when the value of the
24680 <li> Domain errors for the mathematics functions, other than those required by this
24682 <li> The values returned by the mathematics functions on domain errors (<a href="#7.12.1">7.12.1</a>).
24683 <li> The values returned by the mathematics functions on underflow range errors, whether
24684 errno is set to the value of the macro ERANGE when the integer expression
24685 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
24686 floating-point exception is raised when the integer expression math_errhandling
24688 <li> Whether a domain error occurs or zero is returned when an fmod function has a
24690 <li> Whether a domain error occurs or zero is returned when a remainder function has
24692 <li> The base-2 logarithm of the modulus used by the remquo functions in reducing the
24694 <!--page 522 -->
24695 <li> Whether a domain error occurs or zero is returned when a remquo function has a
24697 <li> Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
24698 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>).
24700 <li> Whether the last line of a text stream requires a terminating new-line character
24702 <li> Whether space characters that are written out to a text stream immediately before a
24704 <li> The number of null characters that may be appended to data written to a binary
24706 <li> Whether the file position indicator of an append-mode stream is initially positioned at
24708 <li> Whether a write on a text stream causes the associated file to be truncated beyond that
24713 <li> Whether the same file can be simultaneously open multiple times (<a href="#7.19.3">7.19.3</a>).
24714 <li> The nature and choice of encodings used for multibyte characters in files (<a href="#7.19.3">7.19.3</a>).
24716 <li> The effect if a file with the new name exists prior to a call to the rename function
24718 <li> Whether an open temporary file is removed upon abnormal program termination
24720 <li> Which changes of mode are permitted (if any), and under what circumstances
24722 <li> The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
24723 sequence printed for a NaN (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
24724 <li> The output for %p conversion in the fprintf or fwprintf function (<a href="#7.19.6.1">7.19.6.1</a>,
24726 <li> The interpretation of a - character that is neither the first nor the last character, nor
24727 the second where a ^ character is the first, in the scanlist for %[ conversion in the
24728 fscanf or fwscanf function (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>).
24729 <!--page 523 -->
24730 <li> The set of sequences matched by a %p conversion and the interpretation of the
24731 corresponding input item in the fscanf or fwscanf function (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
24732 <li> The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
24733 functions on failure (<a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.9.4">7.19.9.4</a>).
24734 <li> The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
24735 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
24737 <li> Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
24738 function sets errno to ERANGE when underflow occurs (<a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>).
24739 <li> Whether the calloc, malloc, and realloc functions return a null pointer or a
24740 pointer to an allocated object when the size requested is zero (<a href="#7.20.3">7.20.3</a>).
24741 <li> Whether open streams with unwritten buffered data are flushed, open streams are
24742 closed, or temporary files are removed when the abort or _Exit function is called
24744 <li> The termination status returned to the host environment by the abort, exit, or
24745 _Exit function (<a href="#7.20.4.1">7.20.4.1</a>, <a href="#7.20.4.3">7.20.4.3</a>, <a href="#7.20.4.4">7.20.4.4</a>).
24746 <li> The value returned by the system function when its argument is not a null pointer
24749 <li> The range and precision of times representable in clock_t and time_t (<a href="#7.23">7.23</a>).
24751 <li> The replacement string for the %Z specifier to the strftime, and wcsftime
24752 functions in the "C" locale (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
24753 <li> Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
24754 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.9">F.9</a>).
24755 </ul>
24758 <p><!--para 1 -->
24759 <ul>
24760 <li> The values or expressions assigned to the macros specified in the headers
24761 <a href="#7.7"><float.h></a>, <a href="#7.10"><limits.h></a>, and <a href="#7.18"><stdint.h></a> (<a href="#5.2.4.2">5.2.4.2</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>).
24762 <li> The number, order, and encoding of bytes in any object (when not explicitly specified
24765 <!--page 524 -->
24766 </ul>
24769 <p><!--para 1 -->
24770 The following characteristics of a hosted environment are locale-specific and are required
24771 to be documented by the implementation:
24772 <ul>
24773 <li> Additional members of the source and execution character sets beyond the basic
24775 <li> The presence, meaning, and representation of additional multibyte characters in the
24777 <li> The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
24782 <li> The sets of characters tested for by the isalpha, isblank, islower, ispunct,
24783 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
24784 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>,
24785 <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>).
24787 <li> Additional subject sequences accepted by the numeric conversion functions (<a href="#7.20.1">7.20.1</a>,
24789 <li> The collation sequence of the execution character set (<a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.24.4.4.2">7.24.4.4.2</a>).
24790 <li> The contents of the error message strings set up by the strerror function
24792 <li> The formats for time and date (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
24793 <li> Character mappings that are supported by the towctrans function (<a href="#7.25.1">7.25.1</a>).
24794 <li> Character classifications that are supported by the iswctype function (<a href="#7.25.1">7.25.1</a>).
24795 <!--page 525 -->
24796 </ul>
24799 <p><!--para 1 -->
24800 The following extensions are widely used in many systems, but are not portable to all
24801 implementations. The inclusion of any extension that may cause a strictly conforming
24802 program to become invalid renders an implementation nonconforming. Examples of such
24803 extensions are new keywords, extra library functions declared in standard headers, or
24804 predefined macros with names that do not begin with an underscore.
24807 <p><!--para 1 -->
24808 In a hosted environment, the main function receives a third argument, char *envp[],
24809 that points to a null-terminated array of pointers to char, each of which points to a string
24810 that provides information about the environment for this execution of the program
24814 <p><!--para 1 -->
24815 Characters other than the underscore _, letters, and digits, that are not part of the basic
24816 source character set (such as the dollar sign $, or characters in national character sets)
24820 <p><!--para 1 -->
24821 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
24824 <p><!--para 1 -->
24825 A function identifier, or the identifier of an object the declaration of which contains the
24829 <p><!--para 1 -->
24830 String literals are modifiable (in which case, identical string literals should denote distinct
24834 <p><!--para 1 -->
24835 Additional arithmetic types, such as __int128 or double double, and their
24836 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
24837 more range or precision than long double, may be used for evaluating expressions of
24838 other floating types, and may be used to define float_t or double_t.
24839 <!--page 526 -->
24842 <p><!--para 1 -->
24843 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
24845 <p><!--para 2 -->
24846 A pointer to a function may be cast to a pointer to an object or to void, allowing a
24847 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
24850 <p><!--para 1 -->
24851 A bit-field may be declared with a type other than _Bool, unsigned int, or
24855 <p><!--para 1 -->
24856 The fortran function specifier may be used in a function declaration to indicate that
24857 calls suitable for FORTRAN should be generated, or that a different representation for the
24861 <p><!--para 1 -->
24862 The asm keyword may be used to insert assembly language directly into the translator
24863 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
24864 <pre>
24865 asm ( character-string-literal );
24866 </pre>
24869 <p><!--para 1 -->
24870 There may be more than one external definition for the identifier of an object, with or
24871 without the explicit use of the keyword extern; if the definitions disagree, or more than
24875 <p><!--para 1 -->
24876 Macro names that do not begin with an underscore, describing the translation and
24877 execution environments, are defined by the implementation before translation begins
24881 <p><!--para 1 -->
24882 If any floating-point status flags are set on normal termination after all calls to functions
24883 registered by the atexit function have been made (see <a href="#7.20.4.3">7.20.4.3</a>), the implementation
24884 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
24885 <!--page 527 -->
24888 <p><!--para 1 -->
24889 Handlers for specific signals are called with extra arguments in addition to the signal
24892 <h4><a name="J.5.15" href="#J.5.15">J.5.15 Additional stream types and file-opening modes</a></h4>
24893 <p><!--para 1 -->
24895 <p><!--para 2 -->
24896 Additional file-opening modes may be specified by characters appended to the mode
24900 <p><!--para 1 -->
24901 The file position indicator is decremented by each successful call to the ungetc or
24902 ungetwc function for a text stream, except if its value was zero before a call (<a href="#7.19.7.11">7.19.7.11</a>,
24906 <p><!--para 1 -->
24907 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
24908 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
24910 <!--page 528 -->
24913 <ol>
24914 <li> ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
24915 published in The C Programming Language by Brian W. Kernighan and Dennis
24916 M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
24917 <li> 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
24918 California, USA, November 1984.
24919 <li> ANSI X3/TR-1-82 (1982), American National Dictionary for Information
24920 Processing Systems, Information Processing Systems Technical Report.
24921 <li> ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
24922 Arithmetic.
24923 <li> ANSI/IEEE 854-1988, American National Standard for Radix-Independent
24924 Floating-Point Arithmetic.
24925 <li> IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
24926 second edition (previously designated IEC 559:1989).
24927 <li> ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
24928 symbols for use in the physical sciences and technology.
24929 <li> ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
24930 information interchange.
24931 <li> ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
24932 Fundamental terms.
24933 <li> ISO 4217:1995, Codes for the representation of currencies and funds.
24934 <li> ISO 8601:1988, Data elements and interchange formats -- Information
24935 interchange -- Representation of dates and times.
24936 <li> ISO/IEC 9899:1990, Programming languages -- C.
24937 <li> ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
24938 <li> ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
24939 <li> ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
24940 <li> ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
24941 Interface (POSIX) -- Part 2: Shell and Utilities.
24942 <li> ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
24943 preparation of programming language standards.
24944 <li> ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
24945 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
24946 <!--page 529 -->
24947 <li> ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
24948 ISO/IEC 10646-1:1993.
24949 <li> ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
24950 ISO/IEC 10646-1:1993.
24951 <li> ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
24952 Transformation Format for 16 planes of group 00 (UTF-16).
24953 <li> ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
24954 Transformation Format 8 (UTF-8).
24955 <li> ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
24956 <li> ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
24957 <li> ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
24958 syllables.
24959 <li> ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993 Tibetan.
24960 <li> ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
24961 additional characters.
24962 <li> ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
24963 <li> ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
24964 Identifiers for characters.
24965 <li> ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
24966 Ethiopic.
24967 <li> ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
24968 Unified Canadian Aboriginal Syllabics.
24969 <li> ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
24970 Cherokee.
24971 <li> ISO/IEC 10967-1:1994, Information technology -- Language independent
24972 arithmetic -- Part 1: Integer and floating point arithmetic.
24973 <!--page 530 -->
24974 <!--page 531 -->
24975 </ol>
24978 <pre>
24979 ??? x ???, <a href="#3.18">3.18</a> , (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>,
24981 ??? x ???, <a href="#3.19">3.19</a> - (subtraction operator), <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>
24982 ! (logical negation operator), <a href="#6.5.3.3">6.5.3.3</a> - (unary minus operator), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a>
24983 != (inequality operator), <a href="#6.5.9">6.5.9</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>
24984 # operator, <a href="#6.10.3.2">6.10.3.2</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>
24985 # preprocessing directive, <a href="#6.10.7">6.10.7</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24986 # punctuator, <a href="#6.10">6.10</a> -> (structure/union pointer operator), <a href="#6.5.2.3">6.5.2.3</a>
24987 ## operator, <a href="#6.10.3.3">6.10.3.3</a> . (structure/union member operator), <a href="#6.3.2.1">6.3.2.1</a>,
24989 #elif preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.8">6.7.8</a>
24990 #else 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="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a>
24991 #endif preprocessing directive, <a href="#6.10.1">6.10.1</a> / (division operator), <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>
24992 #error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> /* */ (comment delimiters), <a href="#6.4.9">6.4.9</a>
24993 #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 delimiter), <a href="#6.4.9">6.4.9</a>
24994 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> /= (division assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24995 #ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> : (colon punctuator), <a href="#6.7.2.1">6.7.2.1</a>
24996 #ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> :> (alternative spelling of ]), <a href="#6.4.6">6.4.6</a>
24997 #include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</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>,
24999 #line preprocessing directive, <a href="#6.10.4">6.10.4</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
25000 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> <% (alternative spelling of {), <a href="#6.4.6">6.4.6</a>
25001 #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>
25003 % (remainder operator), <a href="#6.5.5">6.5.5</a> <<= (left-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
25004 %: (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>
25005 %:%: (alternative spelling of ##), <a href="#6.4.6">6.4.6</a> <a href="#7.2"><assert.h></a> header, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
25006 %= (remainder assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.3"><complex.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>,
25007 %> (alternative spelling of }), <a href="#6.4.6">6.4.6</a> <a href="#7.26.1">7.26.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
25008 & (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="#7.4"><ctype.h></a> header, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
25009 & (bitwise AND operator), <a href="#6.5.10">6.5.10</a> <a href="#7.5"><errno.h></a> header, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
25010 && (logical AND operator), <a href="#6.5.13">6.5.13</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>,
25012 ' ' (space character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.7"><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="#7.20.1.3">7.20.1.3</a>,
25013 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>
25014 ( ) (cast operator), <a href="#6.5.4">6.5.4</a> <a href="#7.8"><inttypes.h></a> header, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a>
25015 ( ) (function-call operator), <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.9"><iso646.h></a> header, <a href="#4">4</a>, <a href="#7.9">7.9</a>
25016 ( ) (parentheses punctuator), <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</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>
25017 ( ){ } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> <a href="#7.11"><locale.h></a> header, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
25018 * (asterisk punctuator), <a href="#6.7.5.1">6.7.5.1</a>, <a href="#6.7.5.2">6.7.5.2</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="#7.22">7.22</a>, <a href="#F">F</a>,
25019 * (indirection operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#F.9">F.9</a>, <a href="#J.5.17">J.5.17</a>
25020 * (multiplication operator), <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> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
25021 *= (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="#7.26.6">7.26.6</a>
25022 + (addition operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#7.15"><stdarg.h></a> header, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a>
25023 <a href="#G.5.2">G.5.2</a> <a href="#7.16"><stdbool.h></a> header, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a>
25024 + (unary plus operator), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.17"><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>,
25025 ++ (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="#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="#7.17">7.17</a>
25026 ++ (prefix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> <a href="#7.18"><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>,
25027 += (addition assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.18">7.18</a>, <a href="#7.26.8">7.26.8</a>
25029 <!--page 532 -->
25030 <a href="#7.19"><stdio.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a> __cplusplus macro, <a href="#6.10.8">6.10.8</a>
25031 <a href="#7.20"><stdlib.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a> __DATE__ macro, <a href="#6.10.8">6.10.8</a>
25032 <a href="#7.21"><string.h></a> header, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a> __FILE__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#7.2.1.1">7.2.1.1</a>
25033 <a href="#7.22"><tgmath.h></a> header, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</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>
25034 <a href="#7.23"><time.h></a> header, <a href="#7.23">7.23</a> __LINE__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#7.2.1.1">7.2.1.1</a>
25035 <a href="#7.24"><wchar.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, __STDC_, <a href="#6.11.9">6.11.9</a>
25036 <a href="#7.26.12">7.26.12</a>, <a href="#F">F</a> __STDC__ macro, <a href="#6.10.8">6.10.8</a>
25037 <a href="#7.25"><wctype.h></a> header, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a> __STDC_CONSTANT_MACROS macro, <a href="#7.18.4">7.18.4</a>
25038 = (equal-sign punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.8">6.7.8</a> __STDC_FORMAT_MACROS macro, <a href="#7.8.1">7.8.1</a>
25039 = (simple assignment operator), <a href="#6.5.16.1">6.5.16.1</a> __STDC_HOSTED__ macro, <a href="#6.10.8">6.10.8</a>
25040 == (equality operator), <a href="#6.5.9">6.5.9</a> __STDC_IEC_559__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#F.1">F.1</a>
25042 >= (greater-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a> <a href="#6.10.8">6.10.8</a>, <a href="#G.1">G.1</a>
25043 >> (right-shift operator), <a href="#6.5.7">6.5.7</a> __STDC_ISO_10646__ macro, <a href="#6.10.8">6.10.8</a>
25044 >>= (right-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a> __STDC_LIMIT_MACROS macro, <a href="#7.18.2">7.18.2</a>,
25047 [ ] (array subscript operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#6.10.8">6.10.8</a>, <a href="#7.17">7.17</a>
25048 [ ] (brackets punctuator), <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.8">6.7.8</a> __STDC_VERSION__ macro, <a href="#6.10.8">6.10.8</a>
25049 \ (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> __TIME__ macro, <a href="#6.10.8">6.10.8</a>
25050 \ (escape character), <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>
25051 \" (double-quote escape sequence), <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>
25052 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> _Bool type conversions, <a href="#6.3.1.2">6.3.1.2</a>
25053 \\ (backslash escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</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>
25054 \' (single-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> _Complex_I macro, <a href="#7.3.1">7.3.1</a>
25055 \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> _Exit function, <a href="#7.20.4.4">7.20.4.4</a>
25056 padding of binary stream, <a href="#7.19.2">7.19.2</a> _Imaginary keyword, <a href="#G.2">G.2</a>
25057 \? (question-mark escape sequence), <a href="#6.4.4.4">6.4.4.4</a> _Imaginary types, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
25058 \a (alert escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _Imaginary_I macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a>
25059 \b (backspace escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _IOFBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
25060 \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>, _IOLBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.6">7.19.5.6</a>
25061 <a href="#7.4.1.10">7.4.1.10</a> _IONBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
25062 \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>, _Pragma operator, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a>
25063 <a href="#7.4.1.10">7.4.1.10</a> { } (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="#6.7.8">6.7.8</a>,
25065 <a href="#6.4.4.4">6.4.4.4</a> { } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a>
25066 \r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, | (bitwise inclusive OR operator), <a href="#6.5.12">6.5.12</a>
25067 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> |= (bitwise inclusive OR assignment operator),
25068 \t (horizontal-tab escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.5.16.2">6.5.16.2</a>
25069 <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="#7.25.2.1.3">7.25.2.1.3</a> || (logical OR operator), <a href="#6.5.14">6.5.14</a>
25070 \U (universal character names), <a href="#6.4.3">6.4.3</a> ~ (bitwise complement operator), <a href="#6.5.3.3">6.5.3.3</a>
25072 \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>, 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="#7.19.3">7.19.3</a>,
25076 ^ (bitwise exclusive OR operator), <a href="#6.5.11">6.5.11</a> complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a>
25077 ^= (bitwise exclusive OR assignment operator), integer, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.20.6.1">7.20.6.1</a>
25078 <a href="#6.5.16.2">6.5.16.2</a> real, <a href="#7.12.7">7.12.7</a>, <a href="#F.9.4">F.9.4</a>
25081 <!--page 533 -->
25084 acos functions, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#F.9.1.1">F.9.1.1</a> declarator, <a href="#6.7.5.2">6.7.5.2</a>
25086 acosh functions, <a href="#7.12.5.1">7.12.5.1</a>, <a href="#F.9.2.1">F.9.2.1</a> multidimensional, <a href="#6.5.2.1">6.5.2.1</a>
25089 actual argument, <a href="#3.3">3.3</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>
25090 actual parameter (deprecated), <a href="#3.3">3.3</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
25091 addition assignment operator (+=), <a href="#6.5.16.2">6.5.16.2</a> type, <a href="#6.2.5">6.2.5</a>
25092 addition operator (+), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, type conversion, <a href="#6.3.2.1">6.3.2.1</a>
25093 <a href="#G.5.2">G.5.2</a> variable length, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
25094 additive expressions, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
25096 address operator (&), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> ASCII code set, <a href="#5.2.1.1">5.2.1.1</a>
25097 aggregate initialization, <a href="#6.7.8">6.7.8</a> asctime function, <a href="#7.23.3.1">7.23.3.1</a>
25098 aggregate types, <a href="#6.2.5">6.2.5</a> asin functions, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#F.9.1.2">F.9.1.2</a>
25099 alert escape sequence (\a), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> asin type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
25100 aliasing, <a href="#6.5">6.5</a> asinh functions, <a href="#7.12.5.2">7.12.5.2</a>, <a href="#F.9.2.2">F.9.2.2</a>
25101 alignment, <a href="#3.2">3.2</a> asinh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
25102 pointer, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.3">6.3.2.3</a> asm keyword, <a href="#J.5.10">J.5.10</a>
25103 structure/union member, <a href="#6.7.2.1">6.7.2.1</a> assert macro, <a href="#7.2.1.1">7.2.1.1</a>
25104 allocated storage, order and contiguity, <a href="#7.20.3">7.20.3</a> assert.h header, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
25108 bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a> expression, <a href="#6.5.16">6.5.16</a>
25109 logical (&&), <a href="#6.5.13">6.5.13</a> operators, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a>
25112 ANSI/IEEE 854, <a href="#F.1">F.1</a> asterisk punctuator (*), <a href="#6.7.5.1">6.7.5.1</a>, <a href="#6.7.5.2">6.7.5.2</a>
25113 argc (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a> atan functions, <a href="#7.12.4.3">7.12.4.3</a>, <a href="#F.9.1.3">F.9.1.3</a>
25114 argument, <a href="#3.3">3.3</a> atan type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
25115 array, <a href="#6.9.1">6.9.1</a> atan2 functions, <a href="#7.12.4.4">7.12.4.4</a>, <a href="#F.9.1.4">F.9.1.4</a>
25116 default promotions, <a href="#6.5.2.2">6.5.2.2</a> atan2 type-generic macro, <a href="#7.22">7.22</a>
25117 function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> atanh functions, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#F.9.2.3">F.9.2.3</a>
25118 macro, substitution, <a href="#6.10.3.1">6.10.3.1</a> atanh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
25119 argument, complex, <a href="#7.3.9.1">7.3.9.1</a> atexit function, <a href="#7.20.4.2">7.20.4.2</a>, <a href="#7.20.4.3">7.20.4.3</a>, <a href="#7.20.4.4">7.20.4.4</a>,
25120 argv (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a> <a href="#J.5.13">J.5.13</a>
25121 arithmetic constant expression, <a href="#6.6">6.6</a> atof function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.1">7.20.1.1</a>
25122 arithmetic conversions, usual, see usual arithmetic atoi function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
25124 arithmetic operators atoll function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
25125 additive, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> auto storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
25126 bitwise, <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> automatic storage duration, <a href="#5.2.3">5.2.3</a>, <a href="#6.2.4">6.2.4</a>
25128 multiplicative, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</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>
25129 shift, <a href="#6.5.7">6.5.7</a> backslash escape sequence (\\), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a>
25130 unary, <a href="#6.5.3.3">6.5.3.3</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>
25131 arithmetic types, <a href="#6.2.5">6.2.5</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>
25133 <!--page 534 -->
25135 binary streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, calloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.1">7.20.3.1</a>, <a href="#7.20.3.2">7.20.3.2</a>,
25137 bit, <a href="#3.5">3.5</a> carg functions, <a href="#7.3.9.1">7.3.9.1</a>, <a href="#G.6">G.6</a>
25138 high order, <a href="#3.6">3.6</a> carg type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
25139 low order, <a href="#3.6">3.6</a> carriage-return escape sequence (\r), <a href="#5.2.2">5.2.2</a>,
25140 bit-field, <a href="#6.7.2.1">6.7.2.1</a> <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a>
25141 bitand macro, <a href="#7.9">7.9</a> case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
25145 AND assignment (&=), <a href="#6.5.16.2">6.5.16.2</a> extensible, <a href="#7.25.3.2">7.25.3.2</a>
25146 complement (~), <a href="#6.5.3.3">6.5.3.3</a> casin functions, <a href="#7.3.5.2">7.3.5.2</a>, <a href="#G.6">G.6</a>
25148 exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> casinh functions, <a href="#7.3.6.2">7.3.6.2</a>, <a href="#G.6.2.2">G.6.2.2</a>
25150 inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> cast expression, <a href="#6.5.4">6.5.4</a>
25152 blank character, <a href="#7.4.1.3">7.4.1.3</a> catan functions, <a href="#7.3.5.3">7.3.5.3</a>, <a href="#G.6">G.6</a>
25153 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> type-generic macro for, <a href="#7.22">7.22</a>
25154 block scope, <a href="#6.2.1">6.2.1</a> catanh functions, <a href="#7.3.6.3">7.3.6.3</a>, <a href="#G.6.2.3">G.6.2.3</a>
25156 bold type convention, <a href="#6.1">6.1</a> cbrt functions, <a href="#7.12.7.1">7.12.7.1</a>, <a href="#F.9.4.1">F.9.4.1</a>
25158 boolean type, <a href="#6.3.1.2">6.3.1.2</a> ccos functions, <a href="#7.3.5.4">7.3.5.4</a>, <a href="#G.6">G.6</a>
25159 boolean type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a> type-generic macro for, <a href="#7.22">7.22</a>
25160 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="#6.7.8">6.7.8</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>
25162 brackets operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> ceil functions, <a href="#7.12.9.1">7.12.9.1</a>, <a href="#F.9.6.1">F.9.6.1</a>
25163 brackets punctuator ([ ]), <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.8">6.7.8</a> ceil type-generic macro, <a href="#7.22">7.22</a>
25166 broken-down time, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.3">7.23.3</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>
25167 <a href="#7.23.3.1">7.23.3.1</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a>, <a href="#7.23.3.5">7.23.3.5</a> type-generic macro for, <a href="#7.22">7.22</a>
25168 bsearch function, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.1">7.20.5.1</a> cexp2 function, <a href="#7.26.1">7.26.1</a>
25169 btowc function, <a href="#7.24.6.1.1">7.24.6.1.1</a> cexpm1 function, <a href="#7.26.1">7.26.1</a>
25170 BUFSIZ macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.5">7.19.5.5</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>
25171 byte, <a href="#3.6">3.6</a>, <a href="#6.5.3.4">6.5.3.4</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>,
25173 byte-oriented stream, <a href="#7.19.2">7.19.2</a> CHAR_BIT macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25175 <a href="#C">C</a> program, <a href="#5.1.1.1">5.1.1.1</a> CHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25176 <a href="#C">C</a>++, <a href="#7.8.1">7.8.1</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.18.4">7.18.4</a> character, <a href="#3.7">3.7</a>, <a href="#3.7.1">3.7.1</a>
25177 cabs functions, <a href="#7.3.8.1">7.3.8.1</a>, <a href="#G.6">G.6</a> character array initialization, <a href="#6.7.8">6.7.8</a>
25178 type-generic macro for, <a href="#7.22">7.22</a> character case mapping functions, <a href="#7.4.2">7.4.2</a>
25179 cacos functions, <a href="#7.3.5.1">7.3.5.1</a>, <a href="#G.6.1.1">G.6.1.1</a> wide character, <a href="#7.25.3.1">7.25.3.1</a>
25181 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 classification functions, <a href="#7.4.1">7.4.1</a>
25182 type-generic macro for, <a href="#7.22">7.22</a> wide character, <a href="#7.25.2.1">7.25.2.1</a>
25183 calendar time, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.2">7.23.2.2</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.2.4">7.23.2.4</a>, extensible, <a href="#7.25.2.2">7.25.2.2</a>
25184 <a href="#7.23.3.2">7.23.3.2</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</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>
25185 <!--page 535 -->
25186 character display semantics, <a href="#5.2.2">5.2.2</a> complex.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>, <a href="#7.26.1">7.26.1</a>,
25187 character handling header, <a href="#7.4">7.4</a>, <a href="#7.11.1.1">7.11.1.1</a> <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
25191 character string literal, see string literal compound assignment, <a href="#6.5.16.2">6.5.16.2</a>
25192 character type conversion, <a href="#6.3.1.1">6.3.1.1</a> compound literals, <a href="#6.5.2.5">6.5.2.5</a>
25193 character types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.8">6.7.8</a> compound statement, <a href="#6.8.2">6.8.2</a>
25194 cimag functions, <a href="#7.3.9.2">7.3.9.2</a>, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> compound-literal operator (( ){ }), <a href="#6.5.2.5">6.5.2.5</a>
25195 cimag type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> concatenation functions
25201 extensible, <a href="#7.25.2.2">7.25.2.2</a> conditional inclusion, <a href="#6.10.1">6.10.1</a>
25202 clearerr function, <a href="#7.19.10.1">7.19.10.1</a> conditional operator (? :), <a href="#6.5.15">6.5.15</a>
25204 clock function, <a href="#7.23.2.1">7.23.2.1</a> conj functions, <a href="#7.3.9.3">7.3.9.3</a>, <a href="#G.6">G.6</a>
25205 clock_t type, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.1">7.23.2.1</a> conj type-generic macro, <a href="#7.22">7.22</a>
25206 CLOCKS_PER_SEC macro, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.1">7.23.2.1</a> const type qualifier, <a href="#6.7.3">6.7.3</a>
25207 clog functions, <a href="#7.3.7.2">7.3.7.2</a>, <a href="#G.6.3.2">G.6.3.2</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>
25208 type-generic macro for, <a href="#7.22">7.22</a> constant expression, <a href="#6.6">6.6</a>, <a href="#F.7.4">F.7.4</a>
25210 clog1p function, <a href="#7.26.1">7.26.1</a> as primary expression, <a href="#6.5.1">6.5.1</a>
25212 collating sequences, <a href="#5.2.1">5.2.1</a> enumeration, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
25215 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>, integer, <a href="#6.4.4.1">6.4.4.1</a>
25216 <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a> octal, <a href="#6.4.4.1">6.4.4.1</a>
25217 command processor, <a href="#7.20.4.6">7.20.4.6</a> constraint, <a href="#3.8">3.8</a>, <a href="#4">4</a>
25218 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> content of structure/union/enumeration, <a href="#6.7.2.3">6.7.2.3</a>
25219 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> contiguity of allocated storage, <a href="#7.20.3">7.20.3</a>
25221 common initial sequence, <a href="#6.5.2.3">6.5.2.3</a> contracted expression, <a href="#6.5">6.5</a>, <a href="#7.12.2">7.12.2</a>, <a href="#F.6">F.6</a>
25222 common real type, <a href="#6.3.1.8">6.3.1.8</a> control character, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a>
25224 comparison functions, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.1">7.20.5.1</a>, <a href="#7.20.5.2">7.20.5.2</a> conversion, <a href="#6.3">6.3</a>
25229 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="#6.7.5">6.7.5</a> boolean, <a href="#6.3.1.2">6.3.1.2</a>
25230 compl macro, <a href="#7.9">7.9</a> boolean, characters, and integers, <a href="#6.3.1.1">6.3.1.1</a>
25231 complement operator (~), <a href="#6.5.3.3">6.5.3.3</a> by assignment, <a href="#6.5.16.1">6.5.16.1</a>
25233 complex numbers, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a> complex types, <a href="#6.3.1.6">6.3.1.6</a>
25234 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> explicit, <a href="#6.3">6.3</a>
25236 complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#G">G</a> function argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
25237 <!--page 536 -->
25238 function designators, <a href="#6.3.2.1">6.3.2.1</a> type-generic macro for, <a href="#7.22">7.22</a>
25239 function parameter, <a href="#6.9.1">6.9.1</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>
25241 imaginary and complex, <a href="#G.4.3">G.4.3</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>
25243 lvalues, <a href="#6.3.2.1">6.3.2.1</a> ctan functions, <a href="#7.3.5.6">7.3.5.6</a>, <a href="#G.6">G.6</a>
25244 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="#7.22">7.22</a>
25245 real and complex, <a href="#6.3.1.7">6.3.1.7</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>
25246 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.22">7.22</a>
25247 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> ctgamma function, <a href="#7.26.1">7.26.1</a>
25248 real floating types, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#F.3">F.3</a> ctime function, <a href="#7.23.3.2">7.23.3.2</a>
25249 signed and unsigned integers, <a href="#6.3.1.3">6.3.1.3</a> ctype.h header, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
25253 conversion functions data stream, see streams
25254 multibyte/wide character, <a href="#7.20.7">7.20.7</a> date and time header, <a href="#7.23">7.23</a>
25256 restartable, <a href="#7.24.6.3">7.24.6.3</a> DBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25257 multibyte/wide string, <a href="#7.20.8">7.20.8</a> DBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25258 restartable, <a href="#7.24.6.4">7.24.6.4</a> DBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25259 numeric, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a> DBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25260 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1">7.24.4.1</a> DBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25261 single byte/wide character, <a href="#7.24.6.1">7.24.6.1</a> DBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25263 wide character, <a href="#7.24.5">7.24.5</a> DBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25264 conversion specifier, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, DBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25266 conversion state, <a href="#7.20.7">7.20.7</a>, <a href="#7.24.6">7.24.6</a>, <a href="#7.24.6.2.1">7.24.6.2.1</a>, decimal digit, <a href="#5.2.1">5.2.1</a>
25267 <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4">7.24.6.4</a>, decimal-point character, <a href="#7.1.1">7.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
25268 <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
25269 conversion state functions, <a href="#7.24.6.2">7.24.6.2</a> <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.5">F.5</a>
25273 copysign functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#7.12.11.1">7.12.11.1</a>, <a href="#F.3">F.3</a>, pointer, <a href="#6.7.5.1">6.7.5.1</a>
25278 cos functions, <a href="#7.12.4.5">7.12.4.5</a>, <a href="#F.9.1.5">F.9.1.5</a> declarator type derivation, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.5">6.7.5</a>
25279 cos type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
25280 cosh functions, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#F.9.2.4">F.9.2.4</a> increment and decrement
25281 cosh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> default argument promotions, <a href="#6.5.2.2">6.5.2.2</a>
25282 cpow functions, <a href="#7.3.8.2">7.3.8.2</a>, <a href="#G.6.4.1">G.6.4.1</a> default initialization, <a href="#6.7.8">6.7.8</a>
25283 type-generic macro for, <a href="#7.22">7.22</a> default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
25284 cproj functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> define preprocessing directive, <a href="#6.10.3">6.10.3</a>
25285 cproj type-generic macro, <a href="#7.22">7.22</a> defined operator, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.8">6.10.8</a>
25286 creal functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a> definition, <a href="#6.7">6.7</a>
25287 creal type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> function, <a href="#6.9.1">6.9.1</a>
25288 csin functions, <a href="#7.3.5.5">7.3.5.5</a>, <a href="#G.6">G.6</a> derived declarator types, <a href="#6.2.5">6.2.5</a>
25289 <!--page 537 -->
25290 derived types, <a href="#6.2.5">6.2.5</a> end-of-file indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>,
25291 designated initializer, <a href="#6.7.8">6.7.8</a> <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>,
25292 destringizing, <a href="#6.10.9">6.10.9</a> <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.10.1">7.19.10.1</a>, <a href="#7.19.10.2">7.19.10.2</a>, <a href="#7.24.3.1">7.24.3.1</a>,
25294 diagnostic message, <a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a> end-of-file macro, see EOF macro
25296 diagnostics header, <a href="#7.2">7.2</a> endif preprocessing directive, <a href="#6.10.1">6.10.1</a>
25297 difftime function, <a href="#7.23.2.2">7.23.2.2</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>
25298 digit, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> enumerated type, <a href="#6.2.5">6.2.5</a>
25299 digraphs, <a href="#6.4.6">6.4.6</a> enumeration, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.2">6.7.2.2</a>
25300 direct input/output functions, <a href="#7.19.8">7.19.8</a> enumeration constant, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
25301 display device, <a href="#5.2.2">5.2.2</a> enumeration content, <a href="#6.7.2.3">6.7.2.3</a>
25302 div function, <a href="#7.20.6.2">7.20.6.2</a> enumeration members, <a href="#6.7.2.2">6.7.2.2</a>
25304 division assignment operator (/=), <a href="#6.5.16.2">6.5.16.2</a> enumeration tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
25305 division operator (/), <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> enumerator, <a href="#6.7.2.2">6.7.2.2</a>
25307 documentation of implementation, <a href="#4">4</a> environment functions, <a href="#7.20.4">7.20.4</a>
25308 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>, environment list, <a href="#7.20.4.5">7.20.4.5</a>
25309 <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>, environmental considerations, <a href="#5.2">5.2</a>
25310 <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>, environmental limits, <a href="#5.2.4">5.2.4</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.19.2">7.19.2</a>,
25311 <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>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.4.4">7.19.4.4</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.20.2.1">7.20.2.1</a>, <a href="#7.20.4.2">7.20.4.2</a>,
25312 <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> <a href="#7.24.2.1">7.24.2.1</a>
25313 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> EOF macro, <a href="#7.4">7.4</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.1">7.19.5.1</a>, <a href="#7.19.5.2">7.19.5.2</a>,
25314 double _Complex type, <a href="#6.2.5">6.2.5</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.11">7.19.6.11</a>,
25315 double _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#7.19.6.14">7.19.6.14</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.4">7.19.7.4</a>,
25316 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.7.10">7.19.7.10</a>,
25317 double _Imaginary type, <a href="#G.2">G.2</a> <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.2.4">7.24.2.4</a>,
25318 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="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.2.12">7.24.2.12</a>,
25319 <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.2">F.2</a> <a href="#7.24.3.4">7.24.3.4</a>, <a href="#7.24.6.1.1">7.24.6.1.1</a>, <a href="#7.24.6.1.2">7.24.6.1.2</a>
25320 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>, equal-sign punctuator (=), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.8">6.7.8</a>
25322 double-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> equality expressions, <a href="#6.5.9">6.5.9</a>
25323 double-quote escape sequence (\"), <a href="#6.4.4.4">6.4.4.4</a>, equality operator (==), <a href="#6.5.9">6.5.9</a>
25324 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</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>,
25325 double_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, see
25326 also range error
25327 EDOM macro, <a href="#7.5">7.5</a>, <a href="#7.12.1">7.12.1</a>, see also domain error erf functions, <a href="#7.12.8.1">7.12.8.1</a>, <a href="#F.9.5.1">F.9.5.1</a>
25329 EILSEQ macro, <a href="#7.5">7.5</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, erfc functions, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#F.9.5.2">F.9.5.2</a>
25330 <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a>, erfc type-generic macro, <a href="#7.22">7.22</a>
25331 see also encoding error 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>,
25332 element type, <a href="#6.2.5">6.2.5</a> <a href="#7.12.1">7.12.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.10.4">7.19.10.4</a>,
25333 elif preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.24.3.1">7.24.3.1</a>,
25334 ellipsis punctuator (...), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a> <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>,
25335 else preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a>, <a href="#J.5.17">J.5.17</a>
25336 else statement, <a href="#6.8.4.1">6.8.4.1</a> errno.h header, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
25338 encoding error, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, domain, see domain error
25339 <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> encoding, see encoding error
25341 <!--page 538 -->
25342 error conditions, <a href="#7.12.1">7.12.1</a> extended characters, <a href="#5.2.1">5.2.1</a>
25343 error functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.9.5">F.9.5</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>,
25344 error indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.18">7.18</a>
25345 <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.8">7.19.7.8</a>, extended multibyte/wide character conversion
25346 <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.10.1">7.19.10.1</a>, <a href="#7.19.10.3">7.19.10.3</a>, utilities, <a href="#7.24.6">7.24.6</a>
25347 <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a> extensible wide character case mapping functions,
25348 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> <a href="#7.25.3.2">7.25.3.2</a>
25349 error-handling functions, <a href="#7.19.10">7.19.10</a>, <a href="#7.21.6.2">7.21.6.2</a> extensible wide character classification functions,
25351 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> extern storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.7.1">6.7.1</a>
25352 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> external definition, <a href="#6.9">6.9</a>
25353 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.7.5">F.7.5</a> external identifiers, underscore, <a href="#7.1.3">7.1.3</a>
25355 exceptional condition, <a href="#6.5">6.5</a>, <a href="#7.12.1">7.12.1</a> external name, <a href="#6.4.2.1">6.4.2.1</a>
25356 excess precision, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, external object definitions, <a href="#6.9.2">6.9.2</a>
25358 excess range, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> fabs functions, <a href="#7.12.7.2">7.12.7.2</a>, <a href="#F.9.4.2">F.9.4.2</a>
25359 exclusive OR operators fabs type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
25361 bitwise assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> fclose function, <a href="#7.19.5.1">7.19.5.1</a>
25362 executable program, <a href="#5.1.1.1">5.1.1.1</a> fdim functions, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#F.9.9.1">F.9.9.1</a>
25363 execution character set, <a href="#5.2.1">5.2.1</a> fdim type-generic macro, <a href="#7.22">7.22</a>
25364 execution environment, <a href="#5">5</a>, <a href="#5.1.2">5.1.2</a>, see also FE_ALL_EXCEPT macro, <a href="#7.6">7.6</a>
25366 execution sequence, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.8">6.8</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>
25367 exit function, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</a>, FE_DOWNWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
25368 <a href="#7.20.4.4">7.20.4.4</a> FE_INEXACT macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
25369 EXIT_FAILURE macro, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</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>
25370 EXIT_SUCCESS macro, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</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>
25371 exp functions, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#F.9.3.1">F.9.3.1</a> FE_TONEAREST macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
25372 exp type-generic macro, <a href="#7.22">7.22</a> FE_TOWARDZERO macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
25373 exp2 functions, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#F.9.3.2">F.9.3.2</a> FE_UNDERFLOW macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
25374 exp2 type-generic macro, <a href="#7.22">7.22</a> FE_UPWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
25375 explicit conversion, <a href="#6.3">6.3</a> 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>
25376 expm1 functions, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#F.9.3.3">F.9.3.3</a> 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>
25377 expm1 type-generic macro, <a href="#7.22">7.22</a> 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>
25378 exponent part, <a href="#6.4.4.2">6.4.4.2</a> 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>
25379 exponential functions feholdexcept function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.3">7.6.4.3</a>,
25380 complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a> <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
25381 real, <a href="#7.12.6">7.12.6</a>, <a href="#F.9.3">F.9.3</a> 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>
25382 expression, <a href="#6.5">6.5</a> FENV_ACCESS pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.6.1">7.6.1</a>, <a href="#F.7">F.7</a>, <a href="#F.8">F.8</a>,
25386 full, <a href="#6.8">6.8</a> 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>
25387 order of evaluation, <a href="#6.5">6.5</a> ferror function, <a href="#7.19.10.3">7.19.10.3</a>
25388 parenthesized, <a href="#6.5.1">6.5.1</a> fesetenv function, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#F.3">F.3</a>
25389 primary, <a href="#6.5.1">6.5.1</a> 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>
25390 unary, <a href="#6.5.3">6.5.3</a> 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>
25391 expression statement, <a href="#6.8.3">6.8.3</a> 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>
25392 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> 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>
25393 <!--page 539 -->
25394 fexcept_t type, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> floating-point status flag, <a href="#7.6">7.6</a>, <a href="#F.7.6">F.7.6</a>
25395 fflush function, <a href="#7.19.5.2">7.19.5.2</a>, <a href="#7.19.5.3">7.19.5.3</a> floor functions, <a href="#7.12.9.2">7.12.9.2</a>, <a href="#F.9.6.2">F.9.6.2</a>
25396 fgetc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, floor type-generic macro, <a href="#7.22">7.22</a>
25397 <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.8.1">7.19.8.1</a> FLT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25398 fgetpos function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a> FLT_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25399 fgets function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.2">7.19.7.2</a> FLT_EVAL_METHOD macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.8.6.4">6.8.6.4</a>,
25400 fgetwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.12">7.12</a>
25402 fgetws function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.2">7.24.3.2</a> FLT_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25403 field width, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> FLT_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25405 access functions, <a href="#7.19.5">7.19.5</a> FLT_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25407 operations, <a href="#7.19.4">7.19.4</a> FLT_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25408 position indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, FLT_RADIX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
25409 <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>
25410 <a href="#7.19.8.1">7.19.8.1</a>, <a href="#7.19.8.2">7.19.8.2</a>, <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.2">7.19.9.2</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>
25411 <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.9.4">7.19.9.4</a>, <a href="#7.19.9.5">7.19.9.5</a>, <a href="#7.24.3.1">7.24.3.1</a>, fma functions, <a href="#7.12">7.12</a>, <a href="#7.12.13.1">7.12.13.1</a>, <a href="#F.9.10.1">F.9.10.1</a>
25412 <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.3.10">7.24.3.10</a> fma type-generic macro, <a href="#7.22">7.22</a>
25413 positioning functions, <a href="#7.19.9">7.19.9</a> fmax functions, <a href="#7.12.12.2">7.12.12.2</a>, <a href="#F.9.9.2">F.9.9.2</a>
25414 file scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.9">6.9</a> fmax type-generic macro, <a href="#7.22">7.22</a>
25415 FILE type, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> fmin functions, <a href="#7.12.12.3">7.12.12.3</a>, <a href="#F.9.9.3">F.9.9.3</a>
25416 FILENAME_MAX macro, <a href="#7.19.1">7.19.1</a> fmin type-generic macro, <a href="#7.22">7.22</a>
25417 flags, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> fmod functions, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#F.9.7.1">F.9.7.1</a>
25418 floating-point status, see floating-point status fmod type-generic macro, <a href="#7.22">7.22</a>
25420 flexible array member, <a href="#6.7.2.1">6.7.2.1</a> FOPEN_MAX macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.4.3">7.19.4.3</a>
25421 float _Complex type, <a href="#6.2.5">6.2.5</a> for statement, <a href="#6.8.5">6.8.5</a>, <a href="#6.8.5.3">6.8.5.3</a>
25422 float _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, form-feed character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
25423 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> 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>,
25425 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> formal argument (deprecated), <a href="#3.15">3.15</a>
25426 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>, formal parameter, <a href="#3.15">3.15</a>
25427 <a href="#6.3.1.8">6.3.1.8</a> formatted input/output functions, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.19.6">7.19.6</a>
25428 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="#7.20.1.3">7.20.1.3</a>, wide character, <a href="#7.24.2">7.24.2</a>
25430 float_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> forward reference, <a href="#3.11">3.11</a>
25431 floating constant, <a href="#6.4.4.2">6.4.4.2</a> 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
25432 floating suffix, f or <a href="#F">F</a>, <a href="#6.4.4.2">6.4.4.2</a> also contracted expression
25433 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>, FP_FAST_FMA macro, <a href="#7.12">7.12</a>
25435 floating types, <a href="#6.2.5">6.2.5</a>, <a href="#6.11.1">6.11.1</a> FP_FAST_FMAL macro, <a href="#7.12">7.12</a>
25436 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>, FP_ILOGB0 macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
25437 <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.5">F.5</a>, see also contracted expression FP_ILOGBNAN macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
25438 floating-point arithmetic functions, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> FP_INFINITE macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
25439 floating-point classification functions, <a href="#7.12.3">7.12.3</a> FP_NAN macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
25440 floating-point control mode, <a href="#7.6">7.6</a>, <a href="#F.7.6">F.7.6</a> FP_NORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
25441 floating-point environment, <a href="#7.6">7.6</a>, <a href="#F.7">F.7</a>, <a href="#F.7.6">F.7.6</a> FP_SUBNORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
25442 floating-point exception, <a href="#7.6">7.6</a>, <a href="#7.6.2">7.6.2</a>, <a href="#F.9">F.9</a> FP_ZERO macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
25443 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> fpclassify macro, <a href="#7.12.3.1">7.12.3.1</a>, <a href="#F.3">F.3</a>
25444 floating-point rounding mode, <a href="#5.2.4.2.2">5.2.4.2.2</a> fpos_t type, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>
25445 <!--page 540 -->
25446 fprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.1">7.19.6.1</a>, language, <a href="#6.11">6.11</a>
25447 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.5">7.19.6.5</a>, <a href="#7.19.6.6">7.19.6.6</a>, library, <a href="#7.26">7.26</a>
25448 <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.3">F.3</a> fwide function, <a href="#7.19.2">7.19.2</a>, <a href="#7.24.3.5">7.24.3.5</a>
25449 fputc function, <a href="#5.2.2">5.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.7.3">7.19.7.3</a>, fwprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.2">7.19.6.2</a>,
25450 <a href="#7.19.7.8">7.19.7.8</a>, <a href="#7.19.8.2">7.19.8.2</a> <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.2.3">7.24.2.3</a>, <a href="#7.24.2.5">7.24.2.5</a>,
25451 fputs function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.4">7.19.7.4</a> <a href="#7.24.2.11">7.24.2.11</a>
25452 fputwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.3">7.24.3.3</a>, fwrite function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.8.2">7.19.8.2</a>
25453 <a href="#7.24.3.8">7.24.3.8</a> fwscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.2">7.24.2.2</a>,
25454 fputws function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.4">7.24.3.4</a> <a href="#7.24.2.4">7.24.2.4</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.12">7.24.2.12</a>, <a href="#7.24.3.10">7.24.3.10</a>
25456 free function, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a> gamma functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.9.5">F.9.5</a>
25457 freestanding execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, general utilities, <a href="#7.20">7.20</a>
25459 freopen function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.4">7.19.5.4</a> general wide string utilities, <a href="#7.24.4">7.24.4</a>
25460 frexp functions, <a href="#7.12.6.4">7.12.6.4</a>, <a href="#F.9.3.4">F.9.3.4</a> generic parameters, <a href="#7.22">7.22</a>
25461 frexp type-generic macro, <a href="#7.22">7.22</a> getc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>
25462 fscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, getchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.6">7.19.7.6</a>
25463 <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#F.3">F.3</a> getenv function, <a href="#7.20.4.5">7.20.4.5</a>
25464 fseek function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, gets function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.26.9">7.26.9</a>
25465 <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a>, <a href="#7.19.9.5">7.19.9.5</a>, <a href="#7.24.3.10">7.24.3.10</a> getwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.6">7.24.3.6</a>, <a href="#7.24.3.7">7.24.3.7</a>
25466 fsetpos function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, getwchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.7">7.24.3.7</a>
25467 <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.24.3.10">7.24.3.10</a> gmtime function, <a href="#7.23.3.3">7.23.3.3</a>
25468 ftell function, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a> 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>
25470 full expression, <a href="#6.8">6.8</a> greater-than operator (>), <a href="#6.5.8">6.5.8</a>
25471 fully buffered stream, <a href="#7.19.3">7.19.3</a> greater-than-or-equal-to operator (>=), <a href="#6.5.8">6.5.8</a>
25472 function
25473 argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> header, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.2">7.1.2</a>, see also standard headers
25474 body, <a href="#6.9.1">6.9.1</a> header names, <a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>, <a href="#6.10.2">6.10.2</a>
25476 library, <a href="#7.1.4">7.1.4</a> hexadecimal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
25477 declarator, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.11.6">6.11.6</a> hexadecimal prefix, <a href="#6.4.4.1">6.4.4.1</a>
25478 definition, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.7">6.11.7</a> hexadecimal-character escape sequence
25479 designator, <a href="#6.3.2.1">6.3.2.1</a> (\x hexadecimal digits), <a href="#6.4.4.4">6.4.4.4</a>
25481 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.4">7.1.4</a> horizontal-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
25482 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> horizontal-tab escape sequence (\r), <a href="#7.25.2.1.3">7.25.2.1.3</a>
25483 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> horizontal-tab escape sequence (\t), <a href="#5.2.2">5.2.2</a>,
25484 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>, <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>
25485 <a href="#6.7.5.3">6.7.5.3</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> 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>
25486 prototype scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.7.5.2">6.7.5.2</a> HUGE_VAL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
25487 recursive call, <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
25488 return, <a href="#6.8.6.4">6.8.6.4</a> HUGE_VALF macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
25489 scope, <a href="#6.2.1">6.2.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
25490 type, <a href="#6.2.5">6.2.5</a> HUGE_VALL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
25491 type conversion, <a href="#6.3.2.1">6.3.2.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
25493 function type, <a href="#6.2.5">6.2.5</a> complex, <a href="#7.3.6">7.3.6</a>, <a href="#G.6.2">G.6.2</a>
25494 function-call operator (( )), <a href="#6.5.2.2">6.5.2.2</a> real, <a href="#7.12.5">7.12.5</a>, <a href="#F.9.2">F.9.2</a>
25495 function-like macro, <a href="#6.10.3">6.10.3</a> hypot functions, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#F.9.4.3">F.9.4.3</a>
25497 <!--page 541 -->
25498 <a href="#I">I</a> macro, <a href="#7.3.1">7.3.1</a>, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> initial position, <a href="#5.2.2">5.2.2</a>
25499 identifier, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.5.1">6.5.1</a> initial shift state, <a href="#5.2.1.2">5.2.1.2</a>
25500 linkage, see linkage 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="#6.7.8">6.7.8</a>,
25503 reserved, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a> initializer, <a href="#6.7.8">6.7.8</a>
25508 IEC 559, <a href="#F.1">F.1</a> input failure, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a>
25509 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">6.10.8</a>, <a href="#7.3.3">7.3.3</a>, <a href="#7.6">7.6</a>, input/output functions
25510 <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>, <a href="#H.1">H.1</a> character, <a href="#7.19.7">7.19.7</a>
25516 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>, input/output header, <a href="#7.19">7.19</a>
25517 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> input/output, device, <a href="#5.1.2.3">5.1.2.3</a>
25518 if statement, <a href="#6.8.4.1">6.8.4.1</a> int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.7.2">6.7.2</a>
25519 ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
25521 ilogb functions, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.9.3.5">F.9.3.5</a> INT_FASTN_MAX macros, <a href="#7.18.2.3">7.18.2.3</a>
25522 ilogb type-generic macro, <a href="#7.22">7.22</a> INT_FASTN_MIN macros, <a href="#7.18.2.3">7.18.2.3</a>
25523 imaginary macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a> int_fastN_t types, <a href="#7.18.1.3">7.18.1.3</a>
25525 imaginary type domain, <a href="#G.2">G.2</a> INT_LEASTN_MIN macros, <a href="#7.18.2.2">7.18.2.2</a>
25527 imaxabs function, <a href="#7.8.2.1">7.8.2.1</a> INT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
25528 imaxdiv function, <a href="#7.8">7.8</a>, <a href="#7.8.2.2">7.8.2.2</a> INT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>
25529 imaxdiv_t type, <a href="#7.8">7.8</a> integer arithmetic functions, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>,
25531 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>, integer character constant, <a href="#6.4.4.4">6.4.4.4</a>
25532 <a href="#6.7.5">6.7.5</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#E">E</a>, see also environmental integer constant, <a href="#6.4.4.1">6.4.4.1</a>
25534 implementation-defined behavior, <a href="#3.4.1">3.4.1</a>, <a href="#4">4</a>, <a href="#J.3">J.3</a> integer conversion rank, <a href="#6.3.1.1">6.3.1.1</a>
25535 implementation-defined value, <a href="#3.17.1">3.17.1</a> 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>,
25536 implicit conversion, <a href="#6.3">6.3</a> <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.3.3">6.5.3.3</a>, <a href="#6.5.7">6.5.7</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>,
25537 implicit initialization, <a href="#6.7.8">6.7.8</a> <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>
25538 include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.2">6.10.2</a> integer suffix, <a href="#6.4.4.1">6.4.4.1</a>
25539 inclusive OR operators 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>,
25541 bitwise assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> integer types, <a href="#6.2.5">6.2.5</a>, <a href="#7.18">7.18</a>
25542 incomplete type, <a href="#6.2.5">6.2.5</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="#7.18">7.18</a>
25543 increment operators, see arithmetic operators, interactive device, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.3">7.19.5.3</a>
25545 indeterminate value, <a href="#3.17.2">3.17.2</a> internal name, <a href="#6.4.2.1">6.4.2.1</a>
25546 indirection operator (*), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> interrupt, <a href="#5.2.3">5.2.3</a>
25547 inequality operator (!=), <a href="#6.5.9">6.5.9</a> INTMAX_C macro, <a href="#7.18.4.2">7.18.4.2</a>
25548 INFINITY macro, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</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="#7.18.2.5">7.18.2.5</a>
25549 <!--page 542 -->
25550 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="#7.18.2.5">7.18.2.5</a> iswalpha function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
25551 intmax_t type, <a href="#7.18.1.5">7.18.1.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
25552 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> iswblank function, <a href="#7.25.2.1.3">7.25.2.1.3</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
25553 INTN_C macros, <a href="#7.18.4.1">7.18.4.1</a> iswcntrl function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.4">7.25.2.1.4</a>,
25554 INTN_MAX macros, <a href="#7.18.2.1">7.18.2.1</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
25555 INTN_MIN macros, <a href="#7.18.2.1">7.18.2.1</a> iswctype function, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>
25556 intN_t types, <a href="#7.18.1.1">7.18.1.1</a> iswdigit function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
25557 INTPTR_MAX macro, <a href="#7.18.2.4">7.18.2.4</a> <a href="#7.25.2.1.5">7.25.2.1.5</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
25558 INTPTR_MIN macro, <a href="#7.18.2.4">7.18.2.4</a> iswgraph function, <a href="#7.25.2.1">7.25.2.1</a>, <a href="#7.25.2.1.6">7.25.2.1.6</a>,
25559 intptr_t type, <a href="#7.18.1.4">7.18.1.4</a> <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
25560 inttypes.h header, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a> iswlower function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>,
25561 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> <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.1.2">7.25.3.1.2</a>
25562 isalpha function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a> iswprint function, <a href="#7.25.2.1.6">7.25.2.1.6</a>, <a href="#7.25.2.1.8">7.25.2.1.8</a>,
25564 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>, iswpunct function, <a href="#7.25.2.1">7.25.2.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
25565 <a href="#7.4.1.11">7.4.1.11</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>,
25566 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>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
25567 <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> iswspace function, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>,
25568 isfinite macro, <a href="#7.12.3.2">7.12.3.2</a>, <a href="#F.3">F.3</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.6">7.25.2.1.6</a>,
25569 isgraph function, <a href="#7.4.1.6">7.4.1.6</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>,
25570 isgreater macro, <a href="#7.12.14.1">7.12.14.1</a>, <a href="#F.3">F.3</a> <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
25571 isgreaterequal macro, <a href="#7.12.14.2">7.12.14.2</a>, <a href="#F.3">F.3</a> iswupper function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>,
25572 isinf macro, <a href="#7.12.3.3">7.12.3.3</a> <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.1.2">7.25.3.1.2</a>
25573 isless macro, <a href="#7.12.14.3">7.12.14.3</a>, <a href="#F.3">F.3</a> iswxdigit function, <a href="#7.25.2.1.12">7.25.2.1.12</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
25574 islessequal macro, <a href="#7.12.14.4">7.12.14.4</a>, <a href="#F.3">F.3</a> isxdigit function, <a href="#7.4.1.12">7.4.1.12</a>, <a href="#7.11.1.1">7.11.1.1</a>
25575 islessgreater macro, <a href="#7.12.14.5">7.12.14.5</a>, <a href="#F.3">F.3</a> italic type convention, <a href="#3">3</a>, <a href="#6.1">6.1</a>
25576 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>, iteration statements, <a href="#6.8.5">6.8.5</a>
25578 isnan macro, <a href="#7.12.3.4">7.12.3.4</a>, <a href="#F.3">F.3</a> jmp_buf type, <a href="#7.13">7.13</a>
25581 ISO 4217, <a href="#2">2</a>, <a href="#7.11.2.1">7.11.2.1</a> keywords, <a href="#6.4.1">6.4.1</a>, <a href="#G.2">G.2</a>, <a href="#J.5.9">J.5.9</a>, <a href="#J.5.10">J.5.10</a>
25582 ISO 8601, <a href="#2">2</a>, <a href="#7.23.3.5">7.23.3.5</a> known constant size, <a href="#6.2.5">6.2.5</a>
25583 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">6.10.8</a>
25584 ISO/IEC 10976-1, <a href="#H.1">H.1</a> L_tmpnam macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.4">7.19.4.4</a>
25585 ISO/IEC 2382-1, <a href="#2">2</a>, <a href="#3">3</a> label name, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.3">6.2.3</a>
25586 ISO/IEC 646, <a href="#2">2</a>, <a href="#5.2.1.1">5.2.1.1</a> labeled statement, <a href="#6.8.1">6.8.1</a>
25589 iso646.h header, <a href="#4">4</a>, <a href="#7.9">7.9</a> future directions, <a href="#6.11">6.11</a>
25590 isprint function, <a href="#5.2.2">5.2.2</a>, <a href="#7.4.1.8">7.4.1.8</a> syntax summary, <a href="#A">A</a>
25591 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>, Latin alphabet, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
25592 <a href="#7.4.1.11">7.4.1.11</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>
25593 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>, LC_COLLATE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.3">7.21.4.3</a>,
25594 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.4.2">7.24.4.4.2</a>
25595 <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a> LC_CTYPE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.20">7.20</a>, <a href="#7.20.7">7.20.7</a>,
25596 isunordered macro, <a href="#7.12.14.6">7.12.14.6</a>, <a href="#F.3">F.3</a> <a href="#7.20.8">7.20.8</a>, <a href="#7.24.6">7.24.6</a>, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>,
25597 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>, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
25598 <a href="#7.4.2.2">7.4.2.2</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>
25599 iswalnum function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.9">7.25.2.1.9</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>
25600 <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a> LC_TIME macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.3.5">7.23.3.5</a>
25601 <!--page 543 -->
25602 lconv structure type, <a href="#7.11">7.11</a> llabs function, <a href="#7.20.6.1">7.20.6.1</a>
25603 LDBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> lldiv function, <a href="#7.20.6.2">7.20.6.2</a>
25605 LDBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> LLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>,
25607 LDBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> LLONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>,
25609 LDBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.5">F.9.6.5</a>
25610 LDBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llrint type-generic macro, <a href="#7.22">7.22</a>
25611 LDBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.7">F.9.6.7</a>
25612 ldexp functions, <a href="#7.12.6.6">7.12.6.6</a>, <a href="#F.9.3.6">F.9.3.6</a> llround type-generic macro, <a href="#7.22">7.22</a>
25615 ldiv_t type, <a href="#7.20">7.20</a> locale-specific behavior, <a href="#3.4.2">3.4.2</a>, <a href="#J.4">J.4</a>
25616 leading underscore in identifiers, <a href="#7.1.3">7.1.3</a> locale.h header, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
25617 left-shift assignment operator (<<=), <a href="#6.5.16.2">6.5.16.2</a> localeconv function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
25618 left-shift operator (<<), <a href="#6.5.7">6.5.7</a> localization, <a href="#7.11">7.11</a>
25620 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> log functions, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#F.9.3.7">F.9.3.7</a>
25621 function name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> log type-generic macro, <a href="#7.22">7.22</a>
25622 identifier, <a href="#6.4.2.1">6.4.2.1</a> log10 functions, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#F.9.3.8">F.9.3.8</a>
25623 internal name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a> log10 type-generic macro, <a href="#7.22">7.22</a>
25624 length function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.24.4.6.1">7.24.4.6.1</a>, log1p functions, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#F.9.3.9">F.9.3.9</a>
25626 length modifier, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, log2 functions, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#F.9.3.10">F.9.3.10</a>
25629 less-than-or-equal-to operator (<=), <a href="#6.5.8">6.5.8</a> complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
25630 letter, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> real, <a href="#7.12.6">7.12.6</a>, <a href="#F.9.3">F.9.3</a>
25631 lexical elements, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a> logb functions, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.11">F.9.3.11</a>
25632 lgamma functions, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#F.9.5.3">F.9.5.3</a> logb type-generic macro, <a href="#7.22">7.22</a>
25634 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7">7</a> AND (&&), <a href="#6.5.13">6.5.13</a>
25638 use of functions, <a href="#7.1.4">7.1.4</a> long double _Complex type, <a href="#6.2.5">6.2.5</a>
25640 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>
25642 implementation, see implementation limits long double suffix, l or <a href="#L">L</a>, <a href="#6.4.4.2">6.4.4.2</a>
25643 numerical, see numerical 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>,
25644 translation, see translation limits <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.2">F.2</a>
25645 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> 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>,
25646 line buffered stream, <a href="#7.19.3">7.19.3</a> <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
25647 line number, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8">6.10.8</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="#7.19.6.1">7.19.6.1</a>,
25648 line preprocessing directive, <a href="#6.10.4">6.10.4</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
25649 lines, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#7.19.2">7.19.2</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>,
25650 preprocessing directive, <a href="#6.10">6.10</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
25651 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="#6.7.5.2">6.7.5.2</a>, <a href="#6.9">6.9</a>, <a href="#6.9.2">6.9.2</a>, long integer suffix, l or <a href="#L">L</a>, <a href="#6.4.4.1">6.4.4.1</a>
25652 <a href="#6.11.2">6.11.2</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>,
25653 <!--page 544 -->
25654 <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> mbsinit function, <a href="#7.24.6.2.1">7.24.6.2.1</a>
25655 long long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, mbsrtowcs function, <a href="#7.24.6.4.1">7.24.6.4.1</a>
25656 <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> mbstate_t type, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.1">7.19.6.1</a>,
25657 long long integer suffix, ll or LL, <a href="#6.4.4.1">6.4.4.1</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.6">7.24.6</a>,
25658 LONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.6.2.1">7.24.6.2.1</a>, <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.24.6.3.1">7.24.6.3.1</a>, <a href="#7.24.6.4">7.24.6.4</a>
25659 LONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> mbstowcs function, <a href="#6.4.5">6.4.5</a>, <a href="#7.20.8.1">7.20.8.1</a>, <a href="#7.24.6.4">7.24.6.4</a>
25660 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="#7.20.4.3">7.20.4.3</a> mbtowc function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.20.7.2">7.20.7.2</a>, <a href="#7.20.8.1">7.20.8.1</a>,
25662 low-order bit, <a href="#3.6">3.6</a> member access operators (. and ->), <a href="#6.5.2.3">6.5.2.3</a>
25664 lrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.5">F.9.6.5</a> memchr function, <a href="#7.21.5.1">7.21.5.1</a>
25665 lrint type-generic macro, <a href="#7.22">7.22</a> memcmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.1">7.21.4.1</a>
25666 lround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.7">F.9.6.7</a> memcpy function, <a href="#7.21.2.1">7.21.2.1</a>
25667 lround type-generic macro, <a href="#7.22">7.22</a> memmove function, <a href="#7.21.2.2">7.21.2.2</a>
25668 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> memory management functions, <a href="#7.20.3">7.20.3</a>
25670 macro argument substitution, <a href="#6.10.3.1">6.10.3.1</a> minimum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a>
25676 predefined, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a> modf functions, <a href="#7.12.6.12">7.12.6.12</a>, <a href="#F.9.3.12">F.9.3.12</a>
25679 macro parameter, <a href="#6.10.3">6.10.3</a> modulus, complex, <a href="#7.3.8.1">7.3.8.1</a>
25680 macro preprocessor, <a href="#6.10">6.10</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>
25682 magnitude, complex, <a href="#7.3.8.1">7.3.8.1</a> wide character, <a href="#7.20.7">7.20.7</a>
25683 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>, extended, <a href="#7.24.6">7.24.6</a>
25685 malloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.3">7.20.3.3</a>, wide string, <a href="#7.20.8">7.20.8</a>
25690 matching failure, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a> extended, <a href="#7.24.6">7.24.6</a>
25691 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="#7.22">7.22</a>, <a href="#F">F</a>, <a href="#F.9">F.9</a>, restartable, <a href="#7.24.6.3">7.24.6.3</a>
25692 <a href="#J.5.17">J.5.17</a> multibyte/wide string conversion functions, <a href="#7.20.8">7.20.8</a>
25693 MATH_ERREXCEPT macro, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> restartable, <a href="#7.24.6.4">7.24.6.4</a>
25694 math_errhandling macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> multidimensional array, <a href="#6.5.2.1">6.5.2.1</a>
25695 MATH_ERRNO macro, <a href="#7.12">7.12</a> multiplication assignment operator (*=), <a href="#6.5.16.2">6.5.16.2</a>
25696 maximum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a> multiplication operator (*), <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>
25697 MB_CUR_MAX macro, <a href="#7.1.1">7.1.1</a>, <a href="#7.20">7.20</a>, <a href="#7.20.7.2">7.20.7.2</a>, multiplicative expressions, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
25699 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="#7.20">7.20</a> n-char sequence, <a href="#7.20.1.3">7.20.1.3</a>
25700 mblen function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.24.6.3">7.24.6.3</a> n-wchar sequence, <a href="#7.24.4.1.1">7.24.4.1.1</a>
25702 mbrtowc function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</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>
25703 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.6.3.1">7.24.6.3.1</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>, file, <a href="#7.19.3">7.19.3</a>
25704 <a href="#7.24.6.4.1">7.24.6.4.1</a> internal, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
25705 <!--page 545 -->
25711 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.9.8.2">F.9.8.2</a> operand, <a href="#6.4.6">6.4.6</a>, <a href="#6.5">6.5</a>
25712 NAN macro, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> operating system, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#7.20.4.6">7.20.4.6</a>
25714 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>, operator, <a href="#6.4.6">6.4.6</a>
25716 nearbyint type-generic macro, <a href="#7.22">7.22</a> assignment, <a href="#6.5.16">6.5.16</a>
25717 nearest integer functions, <a href="#7.12.9">7.12.9</a>, <a href="#F.9.6">F.9.6</a> associativity, <a href="#6.5">6.5</a>
25719 negative zero, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.12.11.1">7.12.11.1</a> multiplicative, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
25720 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> postfix, <a href="#6.5.2">6.5.2</a>
25721 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>, precedence, <a href="#6.5">6.5</a>
25722 <a href="#7.4.1.10">7.4.1.10</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>
25723 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>, relational, <a href="#6.5.8">6.5.8</a>
25726 nexttoward functions, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, <a href="#F.9.8.4">F.9.8.4</a> unary arithmetic, <a href="#6.5.3.3">6.5.3.3</a>
25729 non-stop floating-point control mode, <a href="#7.6.4.2">7.6.4.2</a> bitwise exclusive (^), <a href="#6.5.11">6.5.11</a>
25730 nongraphic characters, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> bitwise exclusive assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
25731 nonlocal jumps header, <a href="#7.13">7.13</a> bitwise inclusive (|), <a href="#6.5.12">6.5.12</a>
25732 norm, complex, <a href="#7.3.8.1">7.3.8.1</a> bitwise inclusive assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
25736 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> order of evaluation, <a href="#6.5">6.5</a>
25737 padding of binary stream, <a href="#7.19.2">7.19.2</a> ordinary identifier name space, <a href="#6.2.3">6.2.3</a>
25738 NULL macro, <a href="#7.11">7.11</a>, <a href="#7.17">7.17</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.20">7.20</a>, <a href="#7.21.1">7.21.1</a>, orientation of stream, <a href="#7.19.2">7.19.2</a>, <a href="#7.24.3.5">7.24.3.5</a>
25739 <a href="#7.23.1">7.23.1</a>, <a href="#7.24.1">7.24.1</a> outer scope, <a href="#6.2.1">6.2.1</a>
25742 null preprocessing directive, <a href="#6.10.7">6.10.7</a> binary stream, <a href="#7.19.2">7.19.2</a>
25743 null statement, <a href="#6.8.3">6.8.3</a> bits, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.18.1.1">7.18.1.1</a>
25744 null wide character, <a href="#7.1.1">7.1.1</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>
25745 number classification macros, <a href="#7.12">7.12</a>, <a href="#7.12.3.1">7.12.3.1</a> parameter, <a href="#3.15">3.15</a>
25746 numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a> array, <a href="#6.9.1">6.9.1</a>
25747 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1">7.24.4.1</a> ellipsis, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a>
25748 numerical limits, <a href="#5.2.4.2">5.2.4.2</a> 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>
25751 object representation, <a href="#6.2.6.1">6.2.6.1</a> program, <a href="#5.1.2.2.1">5.1.2.2.1</a>
25753 object-like macro, <a href="#6.10.3">6.10.3</a> parentheses punctuator (( )), <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a>
25754 obsolescence, <a href="#6.11">6.11</a>, <a href="#7.26">7.26</a> parenthesized expression, <a href="#6.5.1">6.5.1</a>
25756 octal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.4">6.4.4.4</a> permitted form of initializer, <a href="#6.6">6.6</a>
25757 <!--page 546 -->
25758 perror function, <a href="#7.19.10.4">7.19.10.4</a> PRIcPTR macros, <a href="#7.8.1">7.8.1</a>
25759 phase angle, complex, <a href="#7.3.9.1">7.3.9.1</a> primary expression, <a href="#6.5.1">6.5.1</a>
25760 physical source lines, <a href="#5.1.1.2">5.1.1.2</a> printf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.10">7.19.6.10</a>
25761 placemarker, <a href="#6.10.3.3">6.10.3.3</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>
25762 plus operator, unary, <a href="#6.5.3.3">6.5.3.3</a> printing wide character, <a href="#7.25.2">7.25.2</a>
25763 pointer arithmetic, <a href="#6.5.6">6.5.6</a> program diagnostics, <a href="#7.2.1">7.2.1</a>
25764 pointer comparison, <a href="#6.5.8">6.5.8</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>
25765 pointer declarator, <a href="#6.7.5.1">6.7.5.1</a> program file, <a href="#5.1.1.1">5.1.1.1</a>
25766 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> program image, <a href="#5.1.1.2">5.1.1.2</a>
25767 pointer to function, <a href="#6.5.2.2">6.5.2.2</a> program name (argv[0]), <a href="#5.1.2.2.1">5.1.2.2.1</a>
25768 pointer type, <a href="#6.2.5">6.2.5</a> program parameters, <a href="#5.1.2.2.1">5.1.2.2.1</a>
25769 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 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>
25770 pointer, null, <a href="#6.3.2.3">6.3.2.3</a> program structure, <a href="#5.1.1.1">5.1.1.1</a>
25771 portability, <a href="#4">4</a>, <a href="#J">J</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>,
25773 positive difference, <a href="#7.12.12.1">7.12.12.1</a> program, conforming, <a href="#4">4</a>
25774 positive difference functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a> program, strictly conforming, <a href="#4">4</a>
25775 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> promotions
25776 postfix expressions, <a href="#6.5.2">6.5.2</a> default argument, <a href="#6.5.2.2">6.5.2.2</a>
25777 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> integer, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.3.1.1">6.3.1.1</a>
25778 pow functions, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#F.9.4.4">F.9.4.4</a> prototype, see function prototype
25779 pow type-generic macro, <a href="#7.22">7.22</a> pseudo-random sequence functions, <a href="#7.20.2">7.20.2</a>
25781 complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a> PTRDIFF_MIN macro, <a href="#7.18.3">7.18.3</a>
25782 real, <a href="#7.12.7">7.12.7</a>, <a href="#F.9.4">F.9.4</a> ptrdiff_t type, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>,
25783 pp-number, <a href="#6.4.8">6.4.8</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
25785 pragma preprocessing directive, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> putc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.8">7.19.7.8</a>, <a href="#7.19.7.9">7.19.7.9</a>
25786 precedence of operators, <a href="#6.5">6.5</a> putchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.9">7.19.7.9</a>
25787 precedence of syntax rules, <a href="#5.1.1.2">5.1.1.2</a> puts function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.10">7.19.7.10</a>
25788 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="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> putwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.8">7.24.3.8</a>, <a href="#7.24.3.9">7.24.3.9</a>
25789 excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> putwchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.9">7.24.3.9</a>
25791 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> qsort function, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.2">7.20.5.2</a>
25792 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> qualified types, <a href="#6.2.5">6.2.5</a>
25793 preprocessing concatenation, <a href="#6.10.3.3">6.10.3.3</a> qualified version of type, <a href="#6.2.5">6.2.5</a>
25794 preprocessing directives, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10">6.10</a> question-mark escape sequence (\?), <a href="#6.4.4.4">6.4.4.4</a>
25795 preprocessing file, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.10">6.10</a> quiet NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25797 preprocessing operators 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="#7.20.4.1">7.20.4.1</a>
25798 #, <a href="#6.10.3.2">6.10.3.2</a> rand function, <a href="#7.20">7.20</a>, <a href="#7.20.2.1">7.20.2.1</a>, <a href="#7.20.2.2">7.20.2.2</a>
25799 ##, <a href="#6.10.3.3">6.10.3.3</a> RAND_MAX macro, <a href="#7.20">7.20</a>, <a href="#7.20.2.1">7.20.2.1</a>
25801 defined, <a href="#6.10.1">6.10.1</a> excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>
25802 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> range error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#7.12.5.5">7.12.5.5</a>,
25803 preprocessing translation unit, <a href="#5.1.1.1">5.1.1.1</a> <a href="#7.12.6.1">7.12.6.1</a>, <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>,
25804 preprocessor, <a href="#6.10">6.10</a> <a href="#7.12.6.6">7.12.6.6</a>, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#7.12.6.9">7.12.6.9</a>,
25805 PRIcFASTN macros, <a href="#7.8.1">7.8.1</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="#7.12.6.13">7.12.6.13</a>, <a href="#7.12.7.3">7.12.7.3</a>,
25806 PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#7.12.8.4">7.12.8.4</a>,
25807 PRIcMAX macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.12.1">7.12.12.1</a>,
25809 <!--page 547 -->
25811 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>, save calling environment function, <a href="#7.13.1">7.13.1</a>
25812 <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> scalar types, <a href="#6.2.5">6.2.5</a>
25813 real floating types, <a href="#6.2.5">6.2.5</a> scalbln function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.13">F.9.3.13</a>
25814 real type domain, <a href="#6.2.5">6.2.5</a> scalbln type-generic macro, <a href="#7.22">7.22</a>
25815 real types, <a href="#6.2.5">6.2.5</a> scalbn function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.13">F.9.3.13</a>
25816 real-floating, <a href="#7.12.3">7.12.3</a> scalbn type-generic macro, <a href="#7.22">7.22</a>
25817 realloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a> scanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.19.6.11">7.19.6.11</a>
25818 recommended practice, <a href="#3.16">3.16</a> scanlist, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>
25819 recursion, <a href="#6.5.2.2">6.5.2.2</a> scanset, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>
25820 recursive function call, <a href="#6.5.2.2">6.5.2.2</a> SCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25821 redefinition of macro, <a href="#6.10.3">6.10.3</a> SCHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25822 reentrancy, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a> SCNcFASTN macros, <a href="#7.8.1">7.8.1</a>
25825 register storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a> SCNcN macros, <a href="#7.8.1">7.8.1</a>
25827 reliability of data, interrupted, <a href="#5.1.2.3">5.1.2.3</a> scope of identifier, <a href="#6.2.1">6.2.1</a>, <a href="#6.9.2">6.9.2</a>
25829 remainder functions, <a href="#7.12.10">7.12.10</a>, <a href="#F.9.7">F.9.7</a> string, <a href="#7.21.5">7.21.5</a>
25830 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>, utility, <a href="#7.20.5">7.20.5</a>
25832 remainder operator (%), <a href="#6.5.5">6.5.5</a> SEEK_CUR macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
25833 remainder type-generic macro, <a href="#7.22">7.22</a> SEEK_END macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
25834 remove function, <a href="#7.19.4.1">7.19.4.1</a>, <a href="#7.19.4.4">7.19.4.4</a> SEEK_SET macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
25835 remquo functions, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, <a href="#F.9.7.3">F.9.7.3</a> selection statements, <a href="#6.8.4">6.8.4</a>
25836 remquo type-generic macro, <a href="#7.22">7.22</a> self-referential structure, <a href="#6.7.2.3">6.7.2.3</a>
25837 rename function, <a href="#7.19.4.2">7.19.4.2</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>,
25838 representations of types, <a href="#6.2.6">6.2.6</a> <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a>
25840 rescanning and replacement, <a href="#6.10.3.4">6.10.3.4</a> separate translation, <a href="#5.1.1.1">5.1.1.1</a>
25841 reserved identifiers, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a> sequence points, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a>, <a href="#6.8">6.8</a>, <a href="#7.1.4">7.1.4</a>, <a href="#7.19.6">7.19.6</a>,
25842 restartable multibyte/wide character conversion <a href="#7.20.5">7.20.5</a>, <a href="#7.24.2">7.24.2</a>, <a href="#C">C</a>
25844 restartable multibyte/wide string conversion setbuf function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.1">7.19.5.1</a>, <a href="#7.19.5.5">7.19.5.5</a>
25845 functions, <a href="#7.24.6.4">7.24.6.4</a> setjmp macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>
25846 restore calling environment function, <a href="#7.13.2">7.13.2</a> setjmp.h header, <a href="#7.13">7.13</a>
25847 restrict type qualifier, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a> setlocale function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
25848 restrict-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a> setvbuf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.1">7.19.5.1</a>,
25849 return statement, <a href="#6.8.6.4">6.8.6.4</a> <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
25850 rewind function, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.5">7.19.9.5</a>, shall, <a href="#4">4</a>
25852 right-shift assignment operator (>>=), <a href="#6.5.16.2">6.5.16.2</a> shift sequence, <a href="#7.1.1">7.1.1</a>
25853 right-shift operator (>>), <a href="#6.5.7">6.5.7</a> shift states, <a href="#5.2.1.2">5.2.1.2</a>
25854 rint functions, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.4">F.9.6.4</a> short identifier, character, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.3">6.4.3</a>
25855 rint type-generic macro, <a href="#7.22">7.22</a> short int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
25856 round functions, <a href="#7.12.9.6">7.12.9.6</a>, <a href="#F.9.6.6">F.9.6.6</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
25857 round type-generic macro, <a href="#7.22">7.22</a> short int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
25858 rounding mode, floating point, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
25861 <!--page 548 -->
25862 side effects, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a> source lines, <a href="#5.1.1.2">5.1.1.2</a>
25863 SIG_ATOMIC_MAX macro, <a href="#7.18.3">7.18.3</a> source text, <a href="#5.1.1.2">5.1.1.2</a>
25864 SIG_ATOMIC_MIN macro, <a href="#7.18.3">7.18.3</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>,
25865 sig_atomic_t type, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.18.3">7.18.3</a> <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a>
25866 SIG_DFL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sprintf function, <a href="#7.19.6.6">7.19.6.6</a>, <a href="#7.19.6.13">7.19.6.13</a>
25867 SIG_ERR macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sqrt functions, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.4.5">F.9.4.5</a>
25868 SIG_IGN macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sqrt type-generic macro, <a href="#7.22">7.22</a>
25869 SIGABRT macro, <a href="#7.14">7.14</a>, <a href="#7.20.4.1">7.20.4.1</a> srand function, <a href="#7.20.2.2">7.20.2.2</a>
25870 SIGFPE macro, <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> sscanf function, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.14">7.19.6.14</a>
25871 SIGILL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> standard error stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.10.4">7.19.10.4</a>
25872 SIGINT macro, <a href="#7.14">7.14</a> standard headers, <a href="#4">4</a>, <a href="#7.1.2">7.1.2</a>
25873 sign and magnitude, <a href="#6.2.6.2">6.2.6.2</a> <a href="#7.2"><assert.h></a>, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
25874 sign bit, <a href="#6.2.6.2">6.2.6.2</a> <a href="#7.3"><complex.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>, <a href="#7.26.1">7.26.1</a>,
25875 signal function, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.20.4.4">7.20.4.4</a> <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
25876 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> <a href="#7.4"><ctype.h></a>, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
25877 signal handling functions, <a href="#7.14.1">7.14.1</a> <a href="#7.5"><errno.h></a>, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
25878 signal.h header, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a> <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>
25879 signaling NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#F.2.1">F.2.1</a> <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="#7.20.1.3">7.20.1.3</a>,
25880 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> <a href="#7.24.4.1.1">7.24.4.1.1</a>
25881 signbit macro, <a href="#7.12.3.6">7.12.3.6</a>, <a href="#F.3">F.3</a> <a href="#7.8"><inttypes.h></a>, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a>
25882 signed char type, <a href="#6.2.5">6.2.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.9"><iso646.h></a>, <a href="#4">4</a>, <a href="#7.9">7.9</a>
25883 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> <a href="#7.10"><limits.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
25884 signed character, <a href="#6.3.1.1">6.3.1.1</a> <a href="#7.11"><locale.h></a>, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
25885 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> <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="#7.22">7.22</a>, <a href="#F">F</a>, <a href="#F.9">F.9</a>,
25886 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>, <a href="#J.5.17">J.5.17</a>
25888 signed types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a> <a href="#7.14"><signal.h></a>, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a>
25889 significand part, <a href="#6.4.4.2">6.4.4.2</a> <a href="#7.15"><stdarg.h></a>, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a>
25890 SIGSEGV macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> <a href="#7.16"><stdbool.h></a>, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a>
25891 SIGTERM macro, <a href="#7.14">7.14</a> <a href="#7.17"><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>,
25892 simple assignment operator (=), <a href="#6.5.16.1">6.5.16.1</a> <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.17">7.17</a>
25893 sin functions, <a href="#7.12.4.6">7.12.4.6</a>, <a href="#F.9.1.6">F.9.1.6</a> <a href="#7.18"><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="#7.18">7.18</a>,
25894 sin type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> <a href="#7.26.8">7.26.8</a>
25895 single-byte character, <a href="#3.7.1">3.7.1</a>, <a href="#5.2.1.2">5.2.1.2</a> <a href="#7.19"><stdio.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a>
25896 single-byte/wide character conversion functions, <a href="#7.20"><stdlib.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a>
25897 <a href="#7.24.6.1">7.24.6.1</a> <a href="#7.21"><string.h></a>, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a>
25898 single-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.22"><tgmath.h></a>, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
25899 single-quote escape sequence (\'), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> <a href="#7.23"><time.h></a>, <a href="#7.23">7.23</a>
25900 sinh functions, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#F.9.2.5">F.9.2.5</a> <a href="#7.24"><wchar.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, <a href="#7.26.12">7.26.12</a>,
25902 SIZE_MAX macro, <a href="#7.18.3">7.18.3</a> <a href="#7.25"><wctype.h></a>, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a>
25903 size_t type, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.1">7.19.1</a>, standard input stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>
25904 <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20">7.20</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.23.1">7.23.1</a>, standard integer types, <a href="#6.2.5">6.2.5</a>
25905 <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> standard output stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>
25906 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> standard signed integer types, <a href="#6.2.5">6.2.5</a>
25907 snprintf function, <a href="#7.19.6.5">7.19.6.5</a>, <a href="#7.19.6.12">7.19.6.12</a> state-dependent encoding, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#7.20.7">7.20.7</a>
25909 source character set, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a> break, <a href="#6.8.6.3">6.8.6.3</a>
25911 name, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8">6.10.8</a> continue, <a href="#6.8.6.2">6.8.6.2</a>
25913 <!--page 549 -->
25921 labeled, <a href="#6.8.1">6.8.1</a> literal, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.7.8">6.7.8</a>
25923 return, <a href="#6.8.6.4">6.8.6.4</a> numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a>
25926 switch, <a href="#6.8.4.2">6.8.4.2</a> string.h header, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a>
25927 while, <a href="#6.8.5.1">6.8.5.1</a> stringizing, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.9">6.10.9</a>
25928 static storage duration, <a href="#6.2.4">6.2.4</a> strlen function, <a href="#7.21.6.3">7.21.6.3</a>
25929 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> strncat function, <a href="#7.21.3.2">7.21.3.2</a>
25930 static, in array declarators, <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.5.3">6.7.5.3</a> strncmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.4">7.21.4.4</a>
25931 stdarg.h header, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a> strncpy function, <a href="#7.21.2.4">7.21.2.4</a>
25932 stdbool.h header, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a> strpbrk function, <a href="#7.21.5.4">7.21.5.4</a>
25933 STDC, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> strrchr function, <a href="#7.21.5.5">7.21.5.5</a>
25934 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>, strspn function, <a href="#7.21.5.6">7.21.5.6</a>
25935 <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="#7.17">7.17</a> strstr function, <a href="#7.21.5.7">7.21.5.7</a>
25936 stderr macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a> strtod function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.3">7.20.1.3</a>,
25937 stdin macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.3">F.3</a>
25938 <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.24.2.12">7.24.2.12</a>, <a href="#7.24.3.7">7.24.3.7</a> strtof function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.3">F.3</a>
25939 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="#7.18">7.18</a>, strtoimax function, <a href="#7.8.2.3">7.8.2.3</a>
25941 stdio.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a> strtol function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.2">7.20.1.2</a>,
25942 stdlib.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a> <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a>
25943 stdout macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.3">7.19.6.3</a>, strtold function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.3">F.3</a>
25944 <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.7.10">7.19.7.10</a>, <a href="#7.24.2.11">7.24.2.11</a>, <a href="#7.24.3.9">7.24.3.9</a> strtoll function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1.2">7.20.1.2</a>, <a href="#7.20.1.4">7.20.1.4</a>
25945 storage duration, <a href="#6.2.4">6.2.4</a> strtoul function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.2">7.20.1.2</a>,
25946 storage order of array, <a href="#6.5.2.1">6.5.2.1</a> <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a>
25947 storage-class specifiers, <a href="#6.7.1">6.7.1</a>, <a href="#6.11.5">6.11.5</a> strtoull function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1.2">7.20.1.2</a>, <a href="#7.20.1.4">7.20.1.4</a>
25948 strcat function, <a href="#7.21.3.1">7.21.3.1</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
25951 strcoll function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.21.4.5">7.21.4.5</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
25953 strcspn function, <a href="#7.21.5.3">7.21.5.3</a> dot operator (.), <a href="#6.5.2.3">6.5.2.3</a>
25954 streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.20.4.3">7.20.4.3</a> initialization, <a href="#6.7.8">6.7.8</a>
25957 orientation, <a href="#7.19.2">7.19.2</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>
25958 standard error, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
25959 standard input, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> specifier, <a href="#6.7.2.1">6.7.2.1</a>
25960 standard output, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
25961 unbuffered, <a href="#7.19.3">7.19.3</a> type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a>
25962 strerror function, <a href="#7.19.10.4">7.19.10.4</a>, <a href="#7.21.6.2">7.21.6.2</a> strxfrm function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.5">7.21.4.5</a>
25963 strftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.3">7.23.3</a>, <a href="#7.23.3.5">7.23.3.5</a>, subscripting, <a href="#6.5.2.1">6.5.2.1</a>
25964 <a href="#7.24.5.1">7.24.5.1</a> subtraction assignment operator (-=), <a href="#6.5.16.2">6.5.16.2</a>
25965 <!--page 550 -->
25966 subtraction operator (-), <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> tolower function, <a href="#7.4.2.1">7.4.2.1</a>
25968 floating constant, <a href="#6.4.4.2">6.4.4.2</a> towctrans function, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
25969 integer constant, <a href="#6.4.4.1">6.4.4.1</a> towlower function, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>
25970 switch body, <a href="#6.8.4.2">6.8.4.2</a> towupper function, <a href="#7.25.3.1.2">7.25.3.1.2</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>
25971 switch case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation environment, <a href="#5">5</a>, <a href="#5.1.1">5.1.1</a>
25972 switch default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation limits, <a href="#5.2.4.1">5.2.4.1</a>
25973 switch statement, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation phases, <a href="#5.1.1.2">5.1.1.2</a>
25974 swprintf function, <a href="#7.24.2.3">7.24.2.3</a>, <a href="#7.24.2.7">7.24.2.7</a> translation unit, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.9">6.9</a>
25975 swscanf function, <a href="#7.24.2.4">7.24.2.4</a>, <a href="#7.24.2.8">7.24.2.8</a> trap representation, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.3.2.3">6.3.2.3</a>,
25978 syntax notation, <a href="#6.1">6.1</a> complex, <a href="#7.3.5">7.3.5</a>, <a href="#G.6.1">G.6.1</a>
25979 syntax rule precedence, <a href="#5.1.1.2">5.1.1.2</a> real, <a href="#7.12.4">7.12.4</a>, <a href="#F.9.1">F.9.1</a>
25980 syntax summary, language, <a href="#A">A</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>
25983 tab characters, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> trunc type-generic macro, <a href="#7.22">7.22</a>
25984 tag compatibility, <a href="#6.2.7">6.2.7</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="#7.19.3">7.19.3</a>, <a href="#7.19.5.3">7.19.5.3</a>
25986 tags, <a href="#6.7.2.3">6.7.2.3</a> two's complement, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.18.1.1">7.18.1.1</a>
25987 tan functions, <a href="#7.12.4.7">7.12.4.7</a>, <a href="#F.9.1.7">F.9.1.7</a> type category, <a href="#6.2.5">6.2.5</a>
25988 tan type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> type conversion, <a href="#6.3">6.3</a>
25989 tanh functions, <a href="#7.12.5.6">7.12.5.6</a>, <a href="#F.9.2.6">F.9.2.6</a> type definitions, <a href="#6.7.7">6.7.7</a>
25990 tanh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> type domain, <a href="#6.2.5">6.2.5</a>, <a href="#G.2">G.2</a>
25993 text streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a> type qualifiers, <a href="#6.7.3">6.7.3</a>
25994 tgamma functions, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#F.9.5.4">F.9.5.4</a> type specifiers, <a href="#6.7.2">6.7.2</a>
25995 tgamma type-generic macro, <a href="#7.22">7.22</a> type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
25996 tgmath.h header, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> typedef declaration, <a href="#6.7.7">6.7.7</a>
25998 broken down, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.3">7.23.3</a>, <a href="#7.23.3.1">7.23.3.1</a>, types, <a href="#6.2.5">6.2.5</a>
25999 <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a>, <a href="#7.23.3.5">7.23.3.5</a> character, <a href="#6.7.8">6.7.8</a>
26000 calendar, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.2">7.23.2.2</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.2.4">7.23.2.4</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="#6.7.5">6.7.5</a>
26001 <a href="#7.23.3.2">7.23.3.2</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a> complex, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a>
26003 conversion functions, <a href="#7.23.3">7.23.3</a> const qualified, <a href="#6.7.3">6.7.3</a>
26006 manipulation functions, <a href="#7.23.2">7.23.2</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
26007 time function, <a href="#7.23.2.4">7.23.2.4</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
26010 tm structure type, <a href="#7.23.1">7.23.1</a>, <a href="#7.24.1">7.24.1</a> UINT_FASTN_MAX macros, <a href="#7.18.2.3">7.18.2.3</a>
26011 TMP_MAX macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.19.4.4">7.19.4.4</a> uint_fastN_t types, <a href="#7.18.1.3">7.18.1.3</a>
26012 tmpfile function, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.20.4.3">7.20.4.3</a> UINT_LEASTN_MAX macros, <a href="#7.18.2.2">7.18.2.2</a>
26013 tmpnam function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.19.4.4">7.19.4.4</a> uint_leastN_t types, <a href="#7.18.1.2">7.18.1.2</a>
26014 token, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, see also preprocessing tokens UINT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
26015 token concatenation, <a href="#6.10.3.3">6.10.3.3</a> UINTMAX_C macro, <a href="#7.18.4.2">7.18.4.2</a>
26016 token pasting, <a href="#6.10.3.3">6.10.3.3</a> UINTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.18.2.5">7.18.2.5</a>
26017 <!--page 551 -->
26018 uintmax_t type, <a href="#7.18.1.5">7.18.1.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, USHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
26019 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</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>,
26020 UINTN_C macros, <a href="#7.18.4.1">7.18.4.1</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>
26021 UINTN_MAX macros, <a href="#7.18.2.1">7.18.2.1</a> utilities, general, <a href="#7.20">7.20</a>
26024 uintptr_t type, <a href="#7.18.1.4">7.18.1.4</a> va_arg macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.2">7.15.1.2</a>,
26025 ULLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>,
26026 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
26027 ULONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>,
26028 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
26029 unary arithmetic operators, <a href="#6.5.3.3">6.5.3.3</a> va_copy macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.2">7.15.1.2</a>,
26031 unary minus operator (-), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a> va_end macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.3">7.15.1.3</a>,
26032 unary operators, <a href="#6.5.3">6.5.3</a> <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>,
26033 unary plus operator (+), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
26034 unbuffered stream, <a href="#7.19.3">7.19.3</a> <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>,
26035 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="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
26036 <a href="#7.1.4">7.1.4</a> va_list type, <a href="#7.15">7.15</a>, <a href="#7.15.1.3">7.15.1.3</a>
26037 undefined behavior, <a href="#3.4.3">3.4.3</a>, <a href="#4">4</a>, <a href="#J.2">J.2</a> va_start macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>,
26038 underscore character, <a href="#6.4.2.1">6.4.2.1</a> <a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.3">7.15.1.3</a>, <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>,
26039 underscore, leading, in identifier, <a href="#7.1.3">7.1.3</a> <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>, <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>,
26040 ungetc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>, <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>,
26041 <a href="#7.19.9.3">7.19.9.3</a> <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
26042 ungetwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.10">7.24.3.10</a> value, <a href="#3.17">3.17</a>
26045 arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a> variable arguments header, <a href="#7.15">7.15</a>
26046 content, <a href="#6.7.2.3">6.7.2.3</a> variable length array, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
26047 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> variably modified type, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
26048 initialization, <a href="#6.7.8">6.7.8</a> vertical-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
26049 member alignment, <a href="#6.7.2.1">6.7.2.1</a> 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>,
26051 member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a> vfprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>
26052 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> vfscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>
26053 specifier, <a href="#6.7.2.1">6.7.2.1</a> vfwprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.5">7.24.2.5</a>
26054 tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a> vfwscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.3.10">7.24.3.10</a>
26055 type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a> visibility of identifier, <a href="#6.2.1">6.2.1</a>
26058 unqualified version of type, <a href="#6.2.5">6.2.5</a> void function parameter, <a href="#6.7.5.3">6.7.5.3</a>
26059 unsigned integer suffix, u or <a href="#U">U</a>, <a href="#6.4.4.1">6.4.4.1</a> void type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.2">6.3.2.2</a>, <a href="#6.7.2">6.7.2</a>
26060 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> void type conversion, <a href="#6.3.2.2">6.3.2.2</a>
26061 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>, volatile storage, <a href="#5.1.2.3">5.1.2.3</a>
26062 <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> volatile type qualifier, <a href="#6.7.3">6.7.3</a>
26063 unsigned types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, volatile-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a>
26064 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> vprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.10">7.19.6.10</a>
26065 unspecified behavior, <a href="#3.4.4">3.4.4</a>, <a href="#4">4</a>, <a href="#J.1">J.1</a> vscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.11">7.19.6.11</a>
26066 unspecified value, <a href="#3.17.3">3.17.3</a> vsnprintf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.12">7.19.6.12</a>
26067 uppercase letter, <a href="#5.2.1">5.2.1</a> vsprintf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.13">7.19.6.13</a>
26068 use of library functions, <a href="#7.1.4">7.1.4</a> vsscanf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.14">7.19.6.14</a>
26069 <!--page 552 -->
26070 vswprintf function, <a href="#7.24.2.7">7.24.2.7</a> wctype.h header, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a>
26071 vswscanf function, <a href="#7.24.2.8">7.24.2.8</a> wctype_t type, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>
26072 vwprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.9">7.24.2.9</a> WEOF macro, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.3.6">7.24.3.6</a>,
26073 vwscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.3.10">7.24.3.10</a> <a href="#7.24.3.7">7.24.3.7</a>, <a href="#7.24.3.8">7.24.3.8</a>, <a href="#7.24.3.9">7.24.3.9</a>, <a href="#7.24.3.10">7.24.3.10</a>,
26076 wchar.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, <a href="#7.26.12">7.26.12</a>, white space, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#7.4.1.10">7.4.1.10</a>,
26078 WCHAR_MAX macro, <a href="#7.18.3">7.18.3</a>, <a href="#7.24.1">7.24.1</a> white-space characters, <a href="#6.4">6.4</a>
26079 WCHAR_MIN macro, <a href="#7.18.3">7.18.3</a>, <a href="#7.24.1">7.24.1</a> wide character, <a href="#3.7.3">3.7.3</a>
26080 wchar_t type, <a href="#3.7.3">3.7.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.8">6.7.8</a>, case mapping functions, <a href="#7.25.3.1">7.25.3.1</a>
26081 <a href="#6.10.8">6.10.8</a>, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20">7.20</a>, extensible, <a href="#7.25.3.2">7.25.3.2</a>
26082 <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> classification functions, <a href="#7.25.2.1">7.25.2.1</a>
26083 wcrtomb function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, extensible, <a href="#7.25.2.2">7.25.2.2</a>
26084 <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> constant, <a href="#6.4.4.4">6.4.4.4</a>
26085 wcscat function, <a href="#7.24.4.3.1">7.24.4.3.1</a> formatted input/output functions, <a href="#7.24.2">7.24.2</a>
26086 wcschr function, <a href="#7.24.4.5.1">7.24.4.5.1</a> input functions, <a href="#7.19.1">7.19.1</a>
26087 wcscmp function, <a href="#7.24.4.4.1">7.24.4.4.1</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a> input/output functions, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3">7.24.3</a>
26088 wcscoll function, <a href="#7.24.4.4.2">7.24.4.4.2</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a> output functions, <a href="#7.19.1">7.19.1</a>
26089 wcscpy function, <a href="#7.24.4.2.1">7.24.4.2.1</a> single-byte conversion functions, <a href="#7.24.6.1">7.24.6.1</a>
26090 wcscspn function, <a href="#7.24.4.5.2">7.24.4.5.2</a> wide string, <a href="#7.1.1">7.1.1</a>
26091 wcsftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.24.5.1">7.24.5.1</a> wide string comparison functions, <a href="#7.24.4.4">7.24.4.4</a>
26092 wcslen function, <a href="#7.24.4.6.1">7.24.4.6.1</a> wide string concatenation functions, <a href="#7.24.4.3">7.24.4.3</a>
26093 wcsncat function, <a href="#7.24.4.3.2">7.24.4.3.2</a> wide string copying functions, <a href="#7.24.4.2">7.24.4.2</a>
26094 wcsncmp function, <a href="#7.24.4.4.3">7.24.4.4.3</a> wide string literal, see string literal
26095 wcsncpy function, <a href="#7.24.4.2.2">7.24.4.2.2</a> wide string miscellaneous functions, <a href="#7.24.4.6">7.24.4.6</a>
26096 wcspbrk function, <a href="#7.24.4.5.3">7.24.4.5.3</a> wide string numeric conversion functions, <a href="#7.8.2.4">7.8.2.4</a>,
26098 wcsrtombs function, <a href="#7.24.6.4.2">7.24.6.4.2</a> wide string search functions, <a href="#7.24.4.5">7.24.4.5</a>
26099 wcsspn function, <a href="#7.24.4.5.5">7.24.4.5.5</a> wide-oriented stream, <a href="#7.19.2">7.19.2</a>
26101 wcstod function, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a> WINT_MAX macro, <a href="#7.18.3">7.18.3</a>
26102 wcstod function, <a href="#7.24.4.1.1">7.24.4.1.1</a> WINT_MIN macro, <a href="#7.18.3">7.18.3</a>
26103 wcstof function, <a href="#7.24.4.1.1">7.24.4.1.1</a> wint_t type, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>,
26105 wcstok function, <a href="#7.24.4.5.7">7.24.4.5.7</a> wmemchr function, <a href="#7.24.4.5.8">7.24.4.5.8</a>
26106 wcstol function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, wmemcmp function, <a href="#7.24.4.4.5">7.24.4.4.5</a>
26108 wcstold function, <a href="#7.24.4.1.1">7.24.4.1.1</a> wmemmove function, <a href="#7.24.4.2.4">7.24.4.2.4</a>
26109 wcstoll function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> wmemset function, <a href="#7.24.4.6.2">7.24.4.6.2</a>
26110 wcstombs function, <a href="#7.20.8.2">7.20.8.2</a>, <a href="#7.24.6.4">7.24.6.4</a> wprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.11">7.24.2.11</a>
26111 wcstoul function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, wscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.2.12">7.24.2.12</a>,
26117 wctomb function, <a href="#7.20.7.3">7.20.7.3</a>, <a href="#7.20.8.2">7.20.8.2</a>, <a href="#7.24.6.3">7.24.6.3</a>
26121 </pre>
26122 </body></html>